AIX Glossary
Bull
AIX Glossary
AIX
ORDER REFERENCE
86 A2 79JX 01
Bull
AIX Glossary
AIX
Software
December 1998
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Contents
Special Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1
Alphabetical List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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M ......................................................................
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O ......................................................................
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Q ......................................................................
R ......................................................................
S ......................................................................
T ......................................................................
U ......................................................................
V ......................................................................
W ......................................................................
X ......................................................................
Y ......................................................................
Z ......................................................................
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1-2
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1-18
1-38
1-50
1-57
1-63
1-66
1-69
1-78
1-79
1-81
1-89
1-97
1-102
1-107
1-123
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1-153
1-161
1-164
1-168
1-171
1-173
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Preface
iii
iv
Glossary
Master Glossary
This glossary provides definitions of specialized terms used in the AIX documentation
library. Terms that are defined in nontechnical dictionaries and that have no special meaning
in information processing are not defined in this glossary.
This glossary includes terms and definitions from the following publications:
ISO Vocabulary––Information Processing, developed by the International Organization for
Standardization, Technical Committee 97, Subcommittee 1, as well as definitions from draft
international standards, draft proposals, and working papers in development by the
ISO/TC97/SC1 vocabulary subcommittee.
CCITT Eighth Plenary Assembly Red Book, Terms and Definitions and working documents
published by the International Telegraph and Telephone Consultative Committee of the
International Telecommunication Union, Geneva, 1985.
American National Dictionary for Information Processing Systems, by the Computer and
Business Equipment Manufacturers Association (CBEMA), copyright 1982.
X/Open XAE Specification System Interface Definitions, Issue 4, published by X/Open
Company, Ltd., U.K., copyright 1992.
Preface
v
vi
Glossary
Special Characters
2–1/2 dimension. A drafting term that describes
limited associativity between orthogonal views; two
dimensions with a perspective view that cannot be
modified once created and that cannot be rotated.
Allows for semi–automatic creation of isometric
views.
3270 Device Emulation. Support that allows a
local or remote device on one system to appear as
a 3270 device to another system.
3270 Host Connection Program (HCON). A
program that allows a system unit to emulate a
workstation or printer attached to a System/370
host. See also session profile and HCONuser.
$HOME. An environment variable, set by the
system, that designates a user’s home directory.
Many programs use this variable to designate a
directory where they store temporary work files.
/usr file system. Contains files and programs
necessary for operating the machine.
/tmp file system. A shared storage location for
files.
/var file system. Contains files that are variable on
a per–client basis, such as spool and mail files.
/ file system. The root file system; contains files
that contain machine–specific configuration data.
Glossary
1-1
Alphabetical List
access. To obtain data from or to put data in
storage.
A
A. See ampere.
abbreviation. A character string representing a
longer character string.
abend. (1.) The abnormal end of a task. (2.) The
ending of a task before its completion because of
an error condition that recovery facilities cannot
resolve while the task is running.
abort. This term refers to transactions that do not
complete. Any changes made by a transaction that
is aborted, for whatever reason, must be undone.
Once a transaction is undone (rolled back), no
evidence that the transaction was ever attempted
remains outside of records in the transaction
processing system’s log. See also rolled back.
absolute address. An address that, without the
need for further evaluation, identifies a storage
location or a device.
absolute device. A locating device, such as a
tablet, that reports its position to the operating
system as a set of numbers on a coordinate
system.
absolute time. A point on a time scale.
absolute value. The numeric value of a real
number regardless of its algebraic sign (positive or
negative).
abstract class. A SOM class that is not designed
to be instantiated, but serves as a base class for
the definition of subclasses. Regardless of whether
an abstract class inherits instance data and
methods from parent classes, it will always
introduce methods that must be overridden in a
subclass, in order to produce a class whose
objects are semantically valid.
Abstract Syntax Notation One (ASN.1). A
notation that enables both complicated types to be
defined and values of these types to be specified.
abstraction (data). A data type with a private
representation and a public set of operations.
accelerator. In AIXwindows, a keyboard alternative
to a mouse button action. For example, holding the
<Shift> and <M> keys on the keyboard can be
made to post a menu in the same way that a
mouse button action does. Accelerators typically
provide increased input speed and greater
convenience.
1-2
Glossary
access control list (ACL). (1.) A file attribute that
contains the basic and extended permissions that
control access to the file. (2.) A list of hosts
(maintained by Enhanced X-Windows) that have
access to client programs. By default, only
programs on the local host and those in this list,
also known as ”access list,” can use the display.
The list can be changed by clients on the local
host; some server implementations can also modify
the list. The authorization protocol name and data
received by the server at connection setup may
affect the list as well. See also discretionary access
control.
access control list entry. Data in an access
control list that specifies a set of permissions. In
the case of a principal or group entry, the
permission set is that which may be granted to a
principal having the privilege attribute specified in
the entry; in the case of a mask entry, the
permission set is that which masks the permission
set in a principal or group entry.
access declaration. Used to restore access to
members of a base class.
access level. In computer security, the level of
authority a user has while accessing a secured file
or library.
access permission. A group of designations that
determine who can access a particular file and how
the user can access the file. See also permission
code.
access procedure. The procedure or protocol
used for gaining access to a shared resource. In a
local area network, the shared resource is the
transmission medium. The medium access
procedures specified by the IEEE 802 standard are
CSMA/CD token bus and token ring.
access resolution. The process by which the
accessibility of a particular class member is
determined.
access right. See permission.
accessible. Said of an object for which the client
possesses a valid designator or handle.
account. The log in directory and other information
that give a user access to the system.
accounting system. A utility that monitors various
aspects of system operations; it collects detailed
data on each transaction and provides tools for
processing the data to produce different kinds of
reports.
ACK. See acknowledgment character.
ACK0. A transmission control character for even
positive acknowledgment; indicates that text was
received without transmission errors.
ACK1. A transmission control character for odd
positive acknowledgment; indicates that text was
received without transmission errors.
acknowledge. (1.) To answer. To respond to a poll,
address, or message. (2.) In the X.25 API, to
confirm that a data packet with the D–bit set has
arrived.
acknowledge timeout. The number of seconds
that a station should wait for an acknowledgment
from a remote station after sending data.
acknowledgment character (ACK). In binary
synchronous communications, a transmission
control character sent as an affirmative response to
a data transmission.
ACL. See access control list.
ACM. Association for Computing Machinery.
ACSE. Association Control Service Element.
action. (1.) A defined task that an application
performs. An action modifies the properties of an
object or manipulates the object in some way. A
processing step or operation. (2.) In the awk
command, the lex command, and the yacc
command, a C language program fragment that
defines what the program does when it recognizes
input. (3.) In CDE, a desktop construct that
provides a method for running applications,
executing commands, and other activities such as
printing, removing files, and changing directories.
Actions are defined in a database of configuration
files.
action icon. In CDE, an icon that represents an
action in a File Manager or Application Manager
window, or in the workspace. An action icon is
created by creating an empty executable file with
the same name as the action it represents.
action label. In CDE, the name displayed under
the icon of an action. See also action name.
action name. In CDE, the name associated with
an action, which by default is displayed under the
icon for the action. See also action label.
action statement. C language program fragments
that define how the generated lexical analyzer
reacts to regular expressions that it recognizes.
action table. In Xtoolkit, a table that specifies the
mapping of externally available procedure strings
to the corresponding procedure implemented by
the widget class. All widget class records contain
an action table.
activate. To point with the mouse pointer and
double–click, successfully causing something to
happen.
active. (1.) The windowpane in which the text
cursor is currently positioned is said to be ”active.”
(2.) One of the states in the lifetime of a
transaction. This is the state during which it is
accessing or modifying data.
active gateway. A gateway that is treated like a
network interface in that it is expected to exchange
routing information. If it does not do so for a period
of time, the route associated with the gateway is
deleted. Contrast with passive gateway. See also
gateway.
active grab. In Enhanced X-Windows, a grab
actually owned by the grabbing client. Contrast with
passive grab. See also button grabbing and grab.
actual parameter. The actual value passed to a
routine. Contrast with formal parameter.
ACU. See automatic calling unit or auto–call unit.
adapter. (1.) A mechanism for connecting two
unlike parts or machines. (2.) A printed circuit card
that modifies the system unit to allow it to operate
in a particular way. See also communications
adapter and card.
adapter code. In X.25 communications, the X.25
Interface Co-Processor/2 Protocol Code, which
controls the frame–level and packet–level
communication processing.
adapter descriptor file (ADF). A file of predefined
information used to set up the programmable
option select (POS) registers for an adapter. The
adapter descriptor file database is on a system
hard disk.
add mode. In addition and subtraction operations,
a mode in which the decimal marker is placed at a
predetermined location with respect to the last digit
entered. In selection actions, a mode that allows
the selection to be unaffected by keyboard
navigation.
address. (1.) The telephone number that remote
systems use to call the system. (2.) To refer to a
device or an item of data by its address. (3.) In
word processing, the location, identified by an
address code, of a specific section of the recording
medium or storage. (4.) In data communication, the
Glossary
1-3
unique code assigned to each device or
workstation connected to a network. See also
network user address. (5.) A numbering system
used in network communications to identify a
specific network or host with which to
communicate. Addresses are often denoted in
dotted decimal form. See also presentation
address.
address extension. In X.25 communications, the
called and calling address extensions are optional
CCITT–specified facilities, available on networks
that conform to the 1984 version of X.25.
Synonymous with extended address.
address family. See protocol family.
address field. The part of a packet containing
addressing information. See also packet.
address list. The list used by the xtalk command
to associate users’ names with network user
addresses and other information, for the purpose of
making outgoing X.25 calls without the caller
having to know the addresses. There is one
address list for the system and one for each user.
See also system address list and user address list.
Address Resolution Protocol (ARP). One of the
protocols provided by TCP/IP that dynamically
maps between Internet addresses, Baseband
Adapter addresses, X.25 addresses, and
Token–Ring Adapter addresses on a local area
network.
address space. The code, stack, and data that is
accessible by a process.
Address Translation Register (ATR). A
mechanism that translates real addresses to virtual
addresses.
addressing. (1.) In data communications, the way
that the sending or controlling station selects the
station to which it is sending data. (2.) A means of
identifying storage locations. (3.) Specifying an
address or location within a file. (4.) The
assignment of addresses to the instructions of a
program. See also selection.
ADF. See adapter descriptor file.
adjust. The process of moving text to fit between
the left and right margins.
ADK (Application Developer’s Kit). The
component of the License Use Management
system that is used by software developers to
define and create licenses for software products.
administration environment. The part of the
Monitor that facilitates system configuration and
management.
1-4
Glossary
ADU. See automatic dialing unit.
Advanced Program–to–Program
Communication (APPC). A communications
architecture that allows transaction programs to
exchange information on a peer–to–peer basis.
SNA LU 6.2 allows APPC architecture to operate
on an SNA network.
advisory lock. A type of lock that a process holds
on a region of a file preventing any other process
from locking the region or an overlapping region.
See also enforced lock.
affinity group. In SOM, an array of class objects
that were all registered with the SOMClassMgr
object during the dynamic loading of a class. Any
class is a member of at most one affinity group.
aggregate. (1.) An array, structure, or union. (2.) In
programming languages, a structured collection of
data objects for a data type. (3.) A transmitted
carrier signal that consists of the 12 single–side
bands being sent over the transmission circuit.
aggregate type. In SOM, a user–defined data type
that combines basic types (such as, char, short,
float, and so on) into a more complex type (such as
structs, arrays, strings, sequences, unions, or
enums).
AIX. The operating system that exists between the
hardware and the application programs.
AIX command line. The area of the screen where
commands are displayed as they are typed.
CDE Desktop. A visual user interface for the
operating system consisting of icons and menus
within an AIXwindows window. An iconic view of
the file system providing users with windows, icons,
and menus to perform program and file
management tasks.
AIXwindows Environment. A software graphical
user interface environment based on OSF/MOTIF
consisting of the AIXwindows toolkit, graphics
libraries, window manager, and desktop running on
top of a compatible operating system.
AIXwindows Resource Manager (MRM). A
database management system that allows a user
to effectively retrieve and assign information, such
as specific values and other attributes, especially
regarding applications that allow a user to select
color, font, and other resource preferences. The
MRM system consists of library subroutines that
access the AIXwindows User Interface Language
(UIL) at run time and create user interfaces. See
also AIXwindows User Interface Language (UIL).
AIXwindows Toolkit. An object–oriented collection
of C language data structures and subroutines that
supplement the Enhanced X-Windows toolkit and
simplify the creation of interactive client application
interfaces.
AIXwindows User Interface Definition (UID). A
file containing the definitions for all objects included
in a particular user application. The UID is a subset
of the AIXwindows User Interface Language (UIL)
and functions similarly to the UIL for the particular
application to which it belongs. See also
AIXwindows User Interface Language (UIL).
AIXwindows User Interface Language (UIL). A
compiled–specific language for describing the initial
state of a user interface. UIL specifies the widgets,
gadgets, and compound objects that make up the
interface; it also identifies the subroutines to be
called whenever the interface changes state as a
result of user interaction. See also AIXwindows
User Interface Definition (UID).
alarm. An audible signal at a workstation or printer
that is used to get the operator’s attention.
alert. In SNA, an error message sent to the system
services control point (SSCP) at the host system.
algorithm. A finite set of well–defined rules for the
solution of a problem in a finite number of steps; for
example, a complete specification of a sequence of
arithmetic operations for evaluating sine x to a
given precision.
alias. (1.) An alternate name for a node or a file
that can be used in place of the real name of the
node or file. (2.) An alternate label for a data
element or point in a computer program. (3.) An
alternate name for a member of a partitioned data
set. (4.) Unofficial name used for the network.
Synonymous with nickname. (5.) An assumed or
actual association between two data entities, or
between a data entity and a pointer.
aliasing. (1.) A compilation process that attempts
to determine what aliases exist, so that
optimization does not result in incorrect program
results.
alignment. The position in main storage of a
fixed–length field, such as halfword or doubleword,
on an integral boundary for that unit of information.
For example, a word boundary is a storage
address evenly divisible by four.
All Points Addressable (APA) display. A display
that allows each picture element (pel) to be
individually addressed and displayed. An APA
display permits the display of images that are not
predefined in character boxes. Contrast with
character display. See also bitmapped display.
allocate. (1.) To assign a resource, such as a disk
file or a diskette file, to perform a specific task.
Contrast with deallocate. (2.) A request to allocate
a session between the local LU and a remote LU.
(3.) In NCS, to create a Remote Procedure Call
(RPC) handle that identifies an object.
alphabetic character. A letter or other symbol,
excluding digits, used in a language. Usually the
uppercase and lowercase letters A through Z plus
other special symbols (such as $ and _) allowed by
a particular language. See also alphanumeric
character.
alphanumeric character. Consisting of letters,
numbers, and often other symbols, such as
punctuation marks and mathematical symbols. See
also alphabetic character.
alphanumeric set. Character set composed of
uppercase and lowercase letters and numbers, but
no symbols. See also alphanumeric character.
alternate cell (isolated cell). An NCS cell that
restricts access to a partial group of nodes in the
network. This cell type is usually used to confine
License Use Management license transactions to a
particular set of nodes in the network.
alternate character set. A set of characters that
includes some special characters, such as
mathematical characters and Greek characters,
and that is defined for some printers.
ALU. Arithmetic and logical unit.
ambient light. In three–dimensional graphics, light
that reflects off one or more surfaces in the scene
before arriving at the target surface. Ambient light
is assumed to be nondirectional, and is reflected
uniformly in all directions by the reflecting surface.
In GL, ambient light is mocked up by use of
ambient terms in the lighting equation, rather than
actually computing the reflections.
ambiguous derivation. Derivation is ambiguous if
a C++ class is derived from two or more base
classes that have the same name.
American National Standard Code for
Information Interchange (ASCII). The code
developed by ANSI for information interchange
among data processing systems, data
communications systems, and associated
equipment. The ASCII character set consists of
7–bit control characters and symbolic characters.
American National Standards Institute (ANSI).
An organization sponsored by the Computer and
Business Equipment Manufacturers Association
through which accredited organizations create and
maintain voluntary industry standards.
Glossary
1-5
amp. See ampere.
ampere (A or amp). A unit of measurement for
electric current that is equivalent to a flow of 1
coulomb per second, or to the current produced by
1 volt applied across a resistance of 1 ohm.
amplitude. The size or magnitude of a voltage or
current wave form.
ancestor. In Enhanced X-Windows, a widget that
has inferior widgets. In other words, the superior or
predecessor of an inferior widget. If W is an inferior
of A, then A is an ancestor of W.
ancestor class. A SOM class from which another
class inherits instance methods, attributes, and
instance variables, either directly or indirectly. A
direct descendant of an ancestor class is called a
child class, derived class, or subclass. A direct
ancestor of a class is called a parent class, base
class, or superclass.
annotation. See license annotation.
anonymous union. A union in C++ without a class
name. It must not be followed by a declarator.
ANSI. See American National Standards Institute.
antialiasing. Techniques used to smooth the
”jaggies” otherwise found on lines and polygon
edges caused by scan conversion. Common
techniques include adjusting pixel positions or
setting pixel intensities according to the percent of
pixel area coverage at each point.
a.out. (1.) An output file produced by default for
certain commands. By default, this file is
executable and contains information for the
symbolic debug program. (2.) The object file format
created by the cc command and expected by the
exec subroutine.
APA. See All Points Addressable Display.
APAR. Authorized program analysis report. A
report of a problem caused by a suspected defect
in a current unaltered release of a program.
API. See application program interface.
APL. A programming language. A general–purpose
language for diverse applications such as
commercial data processing, system design,
mathematical and scientific computation, database
applications, and the teaching of mathematics and
other subjects.
AppBuilder. In CDE, a software application used
for constructing a graphical user interface.
APPC. See Advanced Program–To–Program
Communications.
append. (1.) The action that causes data to be
added to the end of existing data. (2.) In word
1-6
Glossary
processing, to attach a file to the end of another
file.
applet. A program, intended for delivery over the
Internet, which can be included in an HTML page,
just as an image can be included.
application. (1.) A program or group of programs
that apply to a particular business area, such as
Inventory Control or the Accounts Receivable
application. (2.) Software coded by or for end users
that performs a service or accomplishes
work–related tasks. (3.) In AIXwindows and
Enhanced X-Windows, the environment is modeled
on a traditional client–server relationship in which
compatible applications are considered clients of
the Enhanced X-Windows server.
Application Developer’s Kit. See ADK.
application development environment. The
Monitor functions used to construct transactional
applications.
application group. In CDE, an Application
Manager folder that holds a specific software
application or set of software applications.
application icon. See action icon.
application identifier (ID). A unique identifier used
to identify an application in the RPCs sent in a
distributed environment.
Application Manager. In CDE, a window
containing objects representing the system actions
available to you.
application program. A program used to perform
an application or part of an application.
application program interface (API). (1.) A set of
run–time routines or system calls that allows an
application program to use a particular service
provided by either the operating system or another
licensed program. (2.) The formally defined
programming language interface that is between a
system control program or a licensed program and
the user of the program.
application programmer. A programmer who
uses an API to produce an application.
application server. In CDE, a host computer that
provides access to a software application.
application shell. A subclass of top–level shell,
this shell is used primarily for an application’s
top–level window.
application transaction program. (1.) A program
that performs an application or part of an
application. (2.) A program that connects and
communicates with stations in a network, enabling
users to perform application–oriented activities.
See also transaction program and service
transaction program.
copy of a database that is saved in case the
original data is damaged or lost.
application window. A rectangular area that
displays the graphics associated with a specific
application. Application windows can be opened,
closed, combined with other types of windows,
moved, stacked, and otherwise manipulated
through user interaction with a window manager.
archive library. A place where programs are
stored for safekeeping.
apply. (1.) In journaling, to place after–images of
records into a physical file member. The
after–images are recorded as entries in a journal.
(2.) When a service update is installed or applied, it
enters the applied state and becomes the currently
active version of the software. When an update is
in the applied state, the previous version of the
update is stored in a special save directory. This
allows you to restore the previous version, if
necessary, without having to reinstall it. Software
that has been applied to the system can be either
committed or rejected. The installp –s command
can be used to get a list of applied products and
updates that are available to be either committed
or rejected. See also commit and reject.
Apply. In CDE, a choice that causes a selection (or
group of selections) in a dialog box to take effect.
apply list file. A file that contains an entry for each
file to be restored during an installation or an
update procedure.
apply stub. A SOM procedure corresponding to a
particular method that accepts as arguments: the
object on which the method is to be invoked, a
pointer to a location in memory where the method’s
result should be stored, a pointer to the method’s
procedure, and the method’s arguments in the form
of a va_list. The apply stub extracts the arguments
from the va_list, invokes the method with its
arguments, and stores its result in the specified
location. Apply stubs are registered with class
objects when instance methods are defined, and
are invoked using the somApply function. Typically,
implementations that override somDispatch call
somApply to invoke a method on a va_list of
arguments.
Appointment Editor. In CDE, in Calendar, a
window you use to schedule, change, or delete an
appointment.
Appointment List. In CDE, a chronological list of
appointments displayed by Calendar.
Arabic numerals. The 10 numerals used for
depicting decimal numbers: the digits 0, 1, 2, 3, 4,
5, 6, 7, 8, and 9. No font is implied. See also
Roman numerals.
archive. (1.) To store programs and data for
safekeeping. (2.) A copy of one or more files or a
arg pointer. A pointer to a subroutine parameter
argument.
argument. (1.) Numbers, letters, or words that
expand or change the way a command works. (2.)
A parameter passed between a calling routine and
a called routine. (3.) An independent variable.
argument list. A string of arguments.
argument string. An ordered list of parameters
passed between programs or routines.
arithmetic constant. In a programming language,
a constant of type integer, real, double precision, or
complex. See also arithmetic expression and
arithmetic operator.
arithmetic expression. One or more arithmetic
operators and arithmetic primaries, the evaluation
of which produces a numeric value. An arithmetic
expression can be an unsigned arithmetic constant,
the name of an arithmetic constant, a reference to
an arithmetic variable, array element, or function,
or a combination of such primaries formed by using
arithmetic operators and parentheses. See also
arithmetic constant and arithmetic operator.
arithmetic object. An integral object or objects
having the float, double, or long double type. The C
For AIX compiler also recognizes objects having
the long double type as arithmetic objects.
arithmetic operator. A symbol that directs a
compiler to perform an arithmetic operation. See
also arithmetic expression and arithmetic constant.
ARK (Administrator Runtime Kit). In License Use
Management, the run–time environment for
licensed software products. It consists of the
network license server daemon (netlsd) and its
associated tools: ls_admin, ls_rpt, and ls_stat.
ARP. See Address Resolution Protocol.
ARPA. Advanced Research Projects Association.
ARPA RFC 822. Standard of ARPA internet text
messages.
array. (1.) A structure that contains an ordered
group of data elements. All elements in an array
have the same data type. (2.) An arrangement of
data in one or more dimensions, such as a list,
table, or multidimensional arrangement of items.
(3.) In programming languages, an aggregate that
consists of data elements, with identical attributes,
each of which may be uniquely referenced by
subscripting.
Glossary
1-7
array declarator. The part of a statement that
describes an array used in a program unit. The
description includes the name of the array, the
number of dimensions, and the size of each
dimension.
array element. A single data item in an array.
array name. The name of an ordered set of data
items.
array padding. In a multiple–array definition, the
optimization of adding elements to each array, or
adding small arrays between user–defined arrays,
to improve the memory–access characteristics of
the arrays.
arrow button. A graphic control that simulates a
push button with a directional arrow. People use
the pointer and mouse to push the button and start
some action that has an associated direction.
arrow keys. In CDE, the four directional keys on a
keyboard.
art tag. In hypertext, a tag linking text to an artwork
window.
artwork frame. In Interleaf, the container for
graphical data.
ASCII. See American National Standard Code for
Information Interchange.
ASCII characters. The characters that make up
the ASCII character set. The ASCII character set
consists of 7–bit control characters and symbolic
characters. See also American National Standard
Code for Information Interchange.
ASCII flat file. See flat file.
ASCIIZ format. A string ending with a null
character.
ASN.1. See Abstract Syntax Notation One.
aspect ratio. The ratio of the height of a primitive
to its width. A rectangle with a width of 10 inches
and a height of 5 inches has an aspect ratio of 10/5
or 2.
assemble. To translate an assembly program into
a computer language. Assembling is usually
accomplished by substituting the computer
language operation codes for the assembly
language operation code, and by substituting
absolute addresses, immediate addresses,
relocatable addresses, or virtual addresses for
symbolic addresses.
assembler. A computer program that converts
assembly language instructions into object code.
Synonymous with assembly program.
assembler language. A symbolic programming
language in which the set of instructions includes
1-8
Glossary
the instructions of the machine and whose data
structures correspond directly to the storage and
registers of the machine.
assembly program. Synonym for assembler.
assertion. See program assertion.
assignment compatible. Indicates whether the
type of a value allows it to be assigned to a
variable. See also compatible types.
assignment conversion. A change to the form of
the right operand that makes the right operand
have the same data type as the left operand.
assignment expression. In C For AIX, an
expression that assigns the value of the right
operand expression to the left operand variable
and has as its value the value of the right operand.
assignment statement. In programming
languages, a statement that assigns the value of
an expression to a variable.
associative transformation. An optimization that
involves changing the order of an expression. An
associative transformation yields mathematically
identical results but not always bitwise identical
results.
associativity. The order for grouping operands
with an operator (either left–to–right or
right–to–left).
async. See asynchronous transmission.
asynchronous. Not synchronized in time. For
example, input events are controlled by the user;
the program can read them later.
asynchronous device. A device using data
transmission in which transmission of a character
or a block of characters can begin at any time, but
in which the bits that represent the character or
block have equal time duration.
asynchronous operation. An operation that does
not of itself cause the process requesting the
operation to be blocked from further use of the
CPU. This implies that the process and the
operation are running concurrently.
asynchronous terminal. A computer terminal
using asynchronous signals to communicate with a
host machine.
Asynchronous Terminal Emulation. A program
that provides emulation of a remote asynchronous
terminal.
asynchronous transmission. Data transmission
in which transmission of a character or block of
characters can begin at any time, but in which the
bits that represent the character or block have
equal time duration. Contrast with synchronous
transmission. See also start–stop.
ATE. See Asynchronous Terminal Emulation.
ATM. Asynchronous transfer mode. A
cell–switching, connection–oriented technology. In
ATM networks, end stations attach to the network
using dedicated full duplex connections.
atom. (1.) A unique ID corresponding to a string
name. Atoms are used to identify properties, types,
and selections. (2.) A 32–bit number that
represents a string value. See also X Atom.
atomic operation. An operation in which signals
cannot occur between the operations of setting the
masks and waiting for the signal.
ATR. See Address Translation Register.
attachment. (1.) The physical connection to the
network that makes it work. (2.) A type of resource
that controls CPs, logical link control, and physical
link control. (3.) In CDE, In Mailer, a data object
within an electronic mail message that is displayed
as an icon in the Attachments list. An attachment
can be text, sound, or a graphic. Multiple
messages can be added (attached) to a single
electronic mail message.
attachment class. The attachment class specifies
the mode in which a station will connect to the
FDDI network. A station may be a dual attachment
station (DAS) or a single attachment station (SAS).
attachment profile. Contains parameters that
associate other defined profiles with the attachment
of the LU to the network. These parameters also
define the type of network being used.
attenuation. (1.) A decrease in magnitude of
current, voltage, or power of a signal in
transmission between points. It may be expressed
in decibels or nepers. (2.) In 3D graphics, the fall
off of light intensity with distance.
attribute. (1.) A characteristic or property of one or
more objects or entities. For example, the attribute
for a displayed field could be ”blinking.” (2.) In GL,
a parameter that can affect the appearance of a
drawing primitive. For instance, color is an
attribute. If the color is set to ”RED,” it will remain
red until changed, and everything that is drawn will
be drawn in red. Other attributes include linestyle,
linewidth, pattern, and font. For a list of attributes
and pipeline options, see also pipeline options. (3.)
In devices, a characteristic of a defined or
configured device. (4.) In SOM, A specialized SOM
syntax for declaring ”set” and ”get” methods.
Method names corresponding to attributes always
begin with ”_set_” or ”_get_”. An attribute name is
declared in the body of the interface statement for
a class. Method procedures for get/set methods
are automatically defined by the SOM Compiler
unless an attribute is declared as ”noget/noset”.
Likewise, a corresponding instance variable is
automatically defined unless an attribute is
declared as ”nodata”. IDL also supports ”readonly”
attributes, which specify only a ”get” method.
Contrast with instance variable. See also resource
value.
attribute file. In system configuration, a text file
that is organized into stanzas, each of which has a
stanza name and a set of attribute definitions in the
form of Attribute=Value pairs. Configuration files
have the attribute file format.
attribute (of file). Some portion of the information
about a file that determines its access and
organizational characteristics.
attribute pair. See attribute, value, and resource
value.
attribute value. See attribute, value, and resource
value.
audit events. Occurrences on the system that may
be security violations. These events cause an audit
record to be written.
audit trail. A collection of audit records.
auditing subsystem. A mechanism that lets an
administrator detect potential or actual security
violations in the system. Components of this
subsystem detect audit events, log and collect
audit events in a system audit trail, and process the
audit trails.
authentication. Verifying the identity of a user
when the login or su command is given. For
example, the operating–system method of
authentication consists of checking the password
entered by a user against the encrypted version of
the password previously defined for that user. A
secondary authentication method can be added for
additional checks, such as verifying the identity of a
user to a network.
authoring environment. The organization and
equipment that allow the creation of hypertext
documents.
authorization. (1.) The determination of a
principal’s permissions with respect to a protected
object. (2.) The approval of a permission sought by
a principal with respect to a protected object.
authorization protocol. A formal procedure for
establishing the authorization of principals with
respect to protected objects.
authorize. (1.) To grant to a user the right to
communicate with or make use of a computer
system or display station. (2.) To give a user either
Glossary
1-9
complete or restricted access to an object,
resource, or function.
auto–answer. The ability of a station to receive a
call over a switched line without operator action.
auto–call. The ability of a station to place a call
over a switched line without operator action.
Contrast with manual call.
auto–call unit (ACU). In X.25 communications, a
device that automatically makes and answers calls.
autodialer. See automatic dialing unit.
autoexec. A command or list of commands run at
login time.
AUTOLOG. A menu–driven utility program
provided in the 3270 Host Connection Program 2.1
and 1.3.2 for AIX and used to create logon
procedures.
automatic calling unit (ACU). A device that allows
a host to automatically dial the number of a remote
device.
automatic dialing unit (ADU). A device that can
automatically generate dialing digits.
automatic scrolling. The scrolling action that
takes place automatically when a cursor is moved
to the border of a pane.
automatic variable. A variable allocated on entry
to a routine and deallocated on the return. Contrast
with static variable.
autonomous system. A group of networks and
gateways for which one administrative authority
has responsibility. An autonomous system can be
small or very large.
autonumber. A unique number associated with the
prefix of each component in the Interleaf desktop
publishing software. Because each autonumber
has a unique value, these numbers are used to
create references to their components elsewhere in
the text. In hardcopy, an autonumber can be used
to create a page reference that renumbers
automatically as its associated component moves
to a different page. In hypertext, autonumbers are
used to create the hypertext links that jump to the
corresponding component. For the ordered–list
1-10
Glossary
item component and the figure caption component,
the autonumbers are visible and are used to
number a series of these items in the proper order.
autonumber reference. A hardcopy or softcopy
reference created from an autonumber. The
autonumber reference automatically renumbers to
reflect the status of its corresponding autonumber.
In softcopy, an autonumber reference is associated
with a hypertext link so that the link jumps to the
corresponding autonumber. See also autonumber.
autopush. A STREAMS mechanism that enables a
prespecified list of modules to be pushed
automatically onto the stream when a STREAMS
device is opened.
auxiliary class data structure. A SOM structure
provided by the SOM API to support efficient static
access to class–specific information used in
dealing with SOM objects. The structure’s name is
<className>CClassData. Its first component
(parentMtab) is a list of parent–class method tables
(used to support efficient parent method calls). Its
second component (instanceDataToken) is the
instance token for the class (generally used to
locate the instance data introduced by method
procedures that implement methods defined by the
class).
available state. The state a device is in when it is
configured. The device status field in the
Customized Devices Object Class in the ODM
reflects whether a device is in the available state or
not.
AZERTY keyboard. A keyboard in which the keys
in the second–from–top row (row D) are labeled
(from left to right): A, Z, E, R, T, Y, U, I, O, and P.
See also QWERTY keyboard.
azimuthal angle. In GL, if a primitive is sitting on
the ground, with its z coordinate straight up, the
azimuthal viewing angle is the angle the observer
makes with the y axis in the x–y plane. If the
observer walks in a circle with the primitive at the
center, the azimuthal angle is the only thing that
varies.
azizo. In Performance Toolbox, a tool used to
analyze performance recordings.
B
backup. Pertaining to a system, device, file, or
facility that can be used in the event of a
malfunction or loss of data.
back margin. The margin of a page that is closest
to the binding edge. Normally, this is the left margin
of the recto page and the right margin of the verso
page.
backup copy. A copy, usually of a file or group of
files, that is kept in case the original file or files are
unintentionally changed or destroyed.
back up. To copy information, usually onto diskette
or tape, for safekeeping.
backup format. When the backup command
makes a copy of a file, it writes the file in this
format. A file in this format must be restored by the
restore command before it can be used.
backdrop. In CDE, the pattern that covers the
workspace background.
backend. The program that sends output to a
particular device. There are two types of backends:
friendly and unfriendly.
backend program. See backend.
backfacing polygon. In GL, a polygon whose
vertices appear in clockwise order in screen space.
If backface culling is enabled, such polygons are
not drawn.
background. (1.) In multiprogramming, the
conditions under which low–priority, noninteractive
programs are run. Contrast with foreground. See
also program level. (2.) In CDE, the underlying
area of a window on which elements, such as
buttons and lists, are displayed.
background activity. See background process.
background color. In AIXwindows and Enhanced
X-Windows, the single electronic color assigned to
the graphic field that appears behind the
foreground elements inside the border of a
displayed widget or gadget. Contrast with
foreground color.
background process. (1.) A process that does not
require operator intervention but can be run by the
computer while the workstation is used to do other
work. (2.) A mode of program execution in which
the shell does not wait for program completion
before prompting the user for another command.
Contrast with foreground process.
backing store. The collection of off–screen, saved
pixels maintained by the Enhanced X-Windows
server.
backscrolling. (1.) Reversing the normal
(top–to–bottom) direction of flow of paper through a
printer. (2.) In reference to a video display, moving
text through the viewing area from top to bottom.
Backtrack. In CDE, in Help Manager, a button and
Navigate menu item you use to follow links
backward, in the reverse order they were
traversed.
backup format file. A file in backup format.
backup system. See dump and restore.
bad block. A portion of a disk that can never be
used reliably.
bandwidth. Data rate transfer in K bits, K bytes, M
bits, and M bytes per second.
base address. The beginning address for
resolving symbolic references to locations in
storage.
base address register. Synonym for base register.
base class. A C++ class from which other classes
are derived. A base class may itself be derived
from another base class.
base line. See baseline.
base name. (1.) The last element to the right of a
full path name. (2.) A file name specified without its
parent directories. (3.) In Ada language, a
compilation unit name specified without its type
qualifier of lib/ or sec/. (4.) In CDE, The file name
of an icon file minus the file–name suffixes for size
(.l, .m, .s, .t) and type (.bm, .pm). For example, the
base name of an icon file named myicon.m.pm is
myicon.
base number. The part of a self–check field from
which the check digit is calculated.
Base Operating System (BOS) installation. The
process of installing and configuring the minimum
amount of software needed to bring a machine to
the running state.
base permission. An access mode that is
assigned to a file owner, file group, or others who
want access to the file. Access modes include read
(r) permission, write (w) permission, and
execute/search (x) permission. See also
discretionary access control.
base register. A general purpose register that the
programmer chooses to contain a base address.
Glossary
1-11
Synonym for base address register. See also
index.
curves, and Cardinal splines all differ in that they
have different bases.
base scalar type. In Pascal, the type from which a
set type or subrange type is derived. See also
subrange scalar type.
batch printing. Queueing one or more documents
to print in a separate job as a background process.
The operator can type or revise additional
documents at the same time. This is a background
process. See also background process.
baseband system. A communications system
whereby information is encoded, modulated, and
impressed on the transmission medium without
shifting or altering the frequency of the information
signal. At any point on the medium, only one
information signal at a time is present.
baseline. In a font, the imaginary line on which the
bottom of each character is aligned.
BASIC (beginner’s all–purpose symbolic
instruction code). (1.) A programming language
designed for interactive systems. Originally
developed at Dartmouth College to encourage
people to use computers for simple
problem–solving operations. (2.) A high–level
programming language with a small number of
statements and a simple syntax. BASIC is
designed to be easily learned and used and is
widely used for interactive applications on
microcomputers.
basic conversation. A connection between two
transaction programs that allows them to exchange
logical records that contain a 2–byte prefix that
specifies the length of the record. LUs 1, 2, and 3
do not use the 2–byte prefix; however, LU 1, 2, and
3 conversations must be basic conversations. This
conversation type is used by service transactions
and LU 1, 2, and 3 application transaction
programs. Contrast with mapped conversation.
Basic Encoding Rules (BER). A set of rules used
to encode ASN.1 values as strings of octets.
basic increment. The smallest unit of motion of
which a device is capable.
Basic Input/Output System. See BIOS.
Basic Networking Utilities (BNU). A group of
programs and files, sometimes called the
UNIX–to–UNIX Copy Program, that provides basic
networking utilities, such as the uucp command.
BNU includes a set of directories, files, programs,
and commands that allow the user to communicate
with a remote AIX or UNIX system over a
dedicated line or a telephone line. See also
UNIX–to–UNIX Copy Program and UUCP login ID.
basic real constant. A string of decimal digits
containing a decimal point and expressing a real
value.
basis. In GL, a curve or patch basis is a 4x4 matrix
that controls the relationship between control points
and the approximating spline. B–splines, Bezier
1-12
Glossary
batch processing. A processing method in which
one or more programs process records with little or
no operator action. This is a background process.
Contrast with interactive processing.
battery backup. A power source that allows the
processor drawer and other data storage devices
to continue operating during a primary AC power
source outage.
baud. (1.) The number of changes in signal levels,
frequency, or phase per second on a
communication channel. If each baud represents 1
bit of data, baud is the same as bits per second.
Informally (as used by programmers) synonymous
with ”bits per second.” Named for J. Baudot,
1845–1903, French inventor. However, it is
possible for one signal change (1 baud) to equal
more than 1 bit of data. (2.) A unit of signaling
speed equal to the number of discrete conditions or
signal events per second. For example, 1 baud
equals one–half dot cycle per second in Morse
code, 1 bit per second in a train of binary signals,
and one 3–bit value per second in a train of signals
that can each assume one of eight different states.
(3.) In asynchronous transmission, the unit of
modulation rate corresponding to one unit interval
per second; for example, if the duration of the unit
interval is 20 milliseconds, the modulation rate is
50 baud. See also bps.
baud rate. In remote communications, the
transmission rate that is synonymous with signal
events. The baud rate is usually expressed in bits
per second.
BCUG. See bilateral closed user group.
behavior (of an object). In SOM, the methods that
an object responds to. These methods are those
either introduced or inherited by the class of the
object. See also state.
BEL. The bell character. A control character that
activates an alarm or other attention devices when
human attention is required. Synonym for console
bell.
benchmark. A program designed to test the
relative performance of computers of different
architectures, or of different implementations of an
architecture. The combination of a rigorously
specified workload and a method of quantifying the
performance of a system when processing that
workload. The performance metric is usually
derived from the time required to process the
workload.
BER. See Basic Encoding Rules.
Bezier cubic curve. In GL, a cubic spline
approximation to a set of four control points that
passes through the first and fourth control points,
and has a continuous slope where two spline
segments meet. See also parametric cubic curve.
BGP. Border Gateway Protocol.
bibliography. A list of documents referred to within
a document. For each document, the following is
generally listed: the author, the document, notes
about the document, and sometimes notes about
its author.
bid. In the contention form of invitation or selection,
an attempt to gain control of a line to transmit data.
bidirectional. See shared port.
big endian. An attribute of data representation that
reflects how multi–octet data are stored in memory.
In big endian representation, the lowest addressed
octet of a multi–octet data item is the most
significant. See also endian and little endian.
big endian order. The method of storage in which
integer values are stored most significant byte first.
See also little endian order.
big word. In the vi editor, a contiguous set of
alphanumeric characters bounded at the beginning
and end by blank spaces, tabs, or new–line
indicators. See also small word.
bilateral closed user group (BCUG). In X.25
communications, an optional facility that allows
calls to be made only between two designated
DTEs. See also closed user group.
bin collection. A method of collecting auditing
data that writes audit records to a temporary bin
file. After the data is processed by the auditbin
daemon, records are written to an audit trail file for
storage.
binary. (1.) Pertaining to a system of numbers to
the base two. The binary digits are 0 and 1. (2.)
Involving a choice of two conditions, such as on–off
or yes–no. (3.) In ODM, a terminal descriptor type
used to define a variable as a bit string that is not
null–terminated. See also terminal descriptor.
binary constant. A constant that is made up of
one or more binary digits.
binary digit. Synonym for bit.
binary expression. An expression containing two
operands and one operator.
binary file. A file that contains codes that are not
part of the ASCII character set. Binary files can
utilize all 256 possible values for each byte in the
file.
binary–image transfer. See bit block transfer.
binary operator. (1.) A symbol representing an
operation to be performed on two data items,
arrays, or expressions. The four types of binary
operators are numeric, character, logical, and
relational. Contrast with unary operator. (2.) An
arithmetic operator that has two terms. Synonym
for dyadic operator.
binary search tree. A search structure in which, at
each step of the search, the set of data elements is
divided by two; some appropriate action is taken in
the case of an odd number of data elements.
binary synchronous communication (BSC). A
form of telecommunication line control that uses a
standard set of transmission control characters and
control character sequences for binary
synchronous transmission of binary–coded data
between stations. Contrast with synchronous data
link control.
bind. (1.) To associate a variable with an absolute
address, identifier, or virtual address, or with a
symbolic address or label in a program. (2.) In
SNA, a request to activate a session between two
logical units. See also bind session. (3.) For
information on how to set a binding, see also set.
BIND. See bind session.
bind image. In SNA, the session parameters that
the system services control point (SSCP) sends to
the primary logical unit (PLU) and the PLU sends in
the BIND request to the secondary logical unit
(SLU); these parameters specify the proposed
protocol options for an LU–LU session.
BIND password. One of the two communication
security passwords. In an LU–LU session, it is the
password that the system checks against the
remote system to verify that the program to which
the user is connected is the correct one. See also
node verification and communications authority
password.
bind session (BIND). In SNA products, a request
to activate a session between two logical units. See
also bind.
binder. See linkage editor.
binding. (1.) A temporary association between a
client and both an object and a server that exports
an interface to the object. A binding is meaningful
only to the program that sets it and is represented
by a bound handle. (2.) In SOM,
Glossary
1-13
Language–specific macro or procedure that makes
implementing and using SOM classes more
convenient. These bindings offer a convenient
interface to SOM that is tailored to a particular
programming language. The SOM Compiler
generates binding files for C and C++. These
binding files include an implementation template for
the class and two header files, one to be included
in the class’s implementation file and the other in
client programs. (3.) In a multiprocessor context,
constraining a thread to a specific physical
processor to gain the benefit of processor affinity.
binding edge. The edge of a page, perforated for
loose binding, to be bound, stapled, or drilled.
BIOS (Basic Input/Output System). In the
Personal Computer AT, microcode that controls
basic hardware operations such as interactions
with diskette drives, fixed–disk drives, and the
keyboard.
bis . Describes a secondary recommendation that
is an alternative to a primary recommendation.
BIST. Built–in self–test.
bit. Either of the binary digits 0 or 1 used in
computers to store information. Synonymous with
binary digit. See also byte.
bit block transfer (BLT). The movement of a
binary image (bitmap or pixmap) by specifying the
lower–left and upper–right corners of the image
and the destination address.
bit BLT. See bit block transfer.
bit clocking. In an EIA–232C or D interface, the
field that indicates which piece of equipment, either
the modem (DCE) or the computer (DTE), provides
the clock signal for synchronized data transactions.
bit field. A member of a structure or union that
contains 1 or more named bits.
bit gravity. In Enhanced X-Windows, the attraction
of window contents for a location in a window.
When a window is resized, its contents can be
relocated. The server can be requested to relocate
the previous contents to a region of the window.
See also gravity.
bit planes. In computer graphics, a bitplane
supplies one bit of color information per pixel on
the display. Thus, an eight bitplane system allows 2
to the eighth power different colors to be displayed
at each pixel.
bit rate. The speed at which bits are transmitted,
usually expressed in bits per second.
bit scattering. A technique for mapping memory
bits to ensure that a minimum number of bits in a
memory word are stored in a single DRAM. With a
1-14
Glossary
minimum number of bits, the ECC is better able to
detect and correct errors caused by a bad DRAM.
bitmap. A pixmap with a depth of one bit plane.
bitmap file. The file containing the height and
width instructions for creating a bitmap.
bitmapped display. A display with a display
adapter that has a hardware representation of each
separately addressable point on the display. The
hardware representation can be processor memory
or adapter memory. See also All Points
Addressable Display.
bits per character. The number of bits in a data
character.
blank common. In FORTRAN, an unnamed
common block.
blind folio. A document in which the pages of the
document are counted but not numbered. See also
folio, dropped folio, and expressed folio.
blit. Bit block transfer.
block. (1) A group of contiguous records recorded
or processed as a unit. Blocks are separated by
interblock gaps and each block may contain one or
more records. (2) In data communications, a group
of records that is recorded, processed, or sent as a
unit. (3) In programming languages, a compound
statement that coincides with the scope of at least
one of the declarations contained within it. A block
may also specify storage allocation or segment
programs for other purposes.
block data subprogram. In FORTRAN, a
subprogram headed by a BLOCK DATA statement
that is used to initialize variables in named
common blocks.
block device. (1.) One of the types of files in the
AIX file system, described by an i–node. (2.) A
device that is accessed by means of an AIX device
driver.
block file. A file listing the usage of blocks on a
disk. See also special file and character special file.
block input/output communication area
(BIOCA). A block of storage in the kernel address
space that is used to communicate with a block I/O
subsystem.
block I/O. Input/output operations on blocks of
data stored in random locations.
block special file. A special file for a block device.
The file provides access to an input or output
device that uses in–core buffers and is capable of
supporting a file system. See also character special
file.
block statement. Any number of data definitions,
declarations, and statements that appear between
the symbols { (left brace) and } (right brace). The C
language, for example, reads a block statement as
a single C language statement. In Ada language, a
block statement is a single statement that may
contain a sequence of statements. It may also
include a declarative part, and exception handlers;
their effects are local to the block statement. See
also statement.
blocking. An optimization that involves changing
the access order of loops that access large arrays,
so that each array element is accessed as
infrequently as possible.
blocking call. A call in which a caller is suspended
until a called procedure completes.
blocking factor. The number of iterations of an
inner loop that are executed for each pass of a
corresponding blocking loop.
BLT. See bit block transfer.
BNC. A connector used with some coaxial cables.
BNU. See Basic Networking Utilities.
BOA (basic object adapter) class. In SOM, a
CORBA interface (represented as an abstract class
in DSOM), which defines generic object–adapter
(OA) methods that a server can use to register
itself and its objects with an ORB (object request
broker). See also SOMOA (SOM object adapter)
class and ORB (object request broker).
body. (1.) On a printed page, the portion of the
page that contains the main text, excluding the
margins, headers, footers, and footnotes. (2.) In a
book, the portion between the front matter and the
back matter. (3.) In Ada language, a body defines
the execution of a subprogram, package, or task. A
body stub is a form of body that indicates that this
execution is defined in a separately compiled
subunit.
boldface. A heavy–faced type, generally a heavier
version of a regular text font. Also, the process of
printing in this type. See also double–strike and
emphasized.
Boolean. A binary numbering system named after
mathematician George Boole in which zero and
one are the only two values that can be returned.
Traditionally, a value of zero represents FALSE
while a value of one represents TRUE. A value of
TRUE or FALSE, where TRUE=1 AND FALSE=0.
boot. See initial program load.
boot block. In a file system, the first block where
the bootstrap program resides. See also bootstrap
block.
boot device. The device that assigns the fixed disk
within the root volume group (rootvg) that will
contain the startup (boot) image.
boot image. An image containing the kernel, file
systems, libraries, and programs. The boot image
is loaded after the machine is turned on or reset
and brings it to a running state.
boot processing. The type of processing that
occurs when a boot image is loaded. The type of
boot device (disk, tape, or network) determines the
type of boot processing that occurs. Boot
processing over the network brings a machine to
the running state, the BOS installing state, or the
diagnostic state depending on the configuration file.
bootstrap. A small program that loads larger
programs during system initialization.
bootstrap block. Synonym for boot block.
border. A visual boundary that separates a
displayed object from everything else on a screen.
BOS (Base Operating System). The collection of
programs that controls the resources and the
operations of the computer system.
bosinst.data. The file that controls the actions of
the BOS installation program.
bottleneck. An area of code within a program that
uses CPU resources inefficiently and therefore
causes unnecessary delays.
bottom shadow. In AIXwindows, a narrow band of
a dark color across the bottom of a rectangular
graphical object (a widget or gadget) that creates a
three–dimensional appearance when the object is
manipulated.
boundary alignment. The position in main storage
of a fixed–length field, such as halfword or
doubleword, on an integral boundary for that unit of
information. For example, a word boundary is a
storage address evenly divisible by four.
bounding box. (1.) In computer graphics, the
bounding box of a character is the smallest
rectangle that encloses the shape at the x, y origin.
(2.) In GL, a two–dimensional rectangle that
bounds a primitive. A bounding box can be used to
determine whether the primitive lies inside a
clipping region. See also character cell and
clipping.
bounds violation. An attempt to access an array
using an index or pointer that references storage
outside of the array.
box. A line enclosure around text or a table.
bpi. Bits per inch, a measure of linear density for
storage products.
Glossary
1-15
bps. Bits per second. In serial transmission, the
instantaneous bit speed with which a device or
channel transmits a character. See also baud.
braces. (1.) The characters { (left brace) and }
(right brace), also known as ”curly brackets.” These
ASCII characters are primary symbols in the C
programming language in which the operating
system is written. (2.) In Pascal, comment
delimiters.
bracket read lock. A shared lock that is obtained,
held only for the duration of the current operation,
and then immediately dropped. This lock mode
ensures that only committed data is read. It does
not guarantee that successive reads of the data will
yield the same value, because other transactions
can immediately modify the value after the read
operation is complete and the lock is dropped.
brackets. (1.) The ASCII characters [ (left bracket)
and ] (right bracket), also known as ”square
brackets.” (This usage does not follow the British
usage of ”brackets” to mean parentheses, the
characters that enclose this sentence.) (2.) In SNA,
one or more chains of request units and their
responses, which are exchanged between two
LU–LU half–sessions and represent a transaction
between them. A bracket must be completed
before another bracket can be started. Examples of
brackets are database inquiries and replies, update
transactions, and remote–job–entry output
sequences to workstations.
branch. In a computer program, an instruction that
selects one of a number of alternative sets of
instructions. A conditional branch occurs only when
a specified condition is met. An instruction that
selects one of a number of alternative sets of
instructions.
branch processing unit. A processing unit that
processes branch instructions and dispatches
fixed– and floating–point instructions to the
fixed–point unit and floating–point unit.
break condition. In the TTY subsystem, a
character framing error in which the data is all
zeros.
break signal. A signal sent over a remote
connection to interrupt current activity on the
remote system.
break statement. A C language control statement
that contains the keyword break and a semicolon.
break value. In allocating data segment space, the
address of the first location beyond the current end
of the data segment.
breakpoint. A place in a computer program,
usually specified by an instruction, where execution
1-16
Glossary
may be interrupted by external intervention or by a
monitor program.
bridge. (1.) In the connection of local loops,
channels, or rings, the equipment and techniques
used to match circuits and facilitate accurate data
transmission. (2.) A functional unit that connects
two local area networks (LANs) that use the same
logical link control (LLC) procedure but may use
different medium access control (MAC)
procedures. Contrast with gateway.
broadband. Transmission media and techniques
that use a broad frequency range, divided into
sub–bands of narrower frequency, so that different
kinds of transmission can occur at the same time.
broadband channel. A data transmission channel
6 MHz wide. Synonym for wide band channel.
broadcast. Simultaneous transmission of data to
more than one destination.
broadcast topology. The topology in which all
stations are connected in parallel with the medium
and are capable of concurrently receiving a signal
transmitted by any other station connected to the
medium.
broken pipe message. A message that occurs if
the pipe becomes unsynchronized.
broker. In NCS, a server that manages information
about objects and interfaces to the objects. A
program that wishes to become the client of an
interface can use a broker to obtain information
about servers that export the interface. See also
Location Broker.
browse. (1.) A function available when you select
the List of Books button at the bottom of a
navigation window. You can move forward and
backward through an online book in the same way
you can move through a book in hardcopy. (2.) In
the xtalk and xroute commands, to view the
details of an entry in the routing list or address list.
BSC. See Binary Synchronous Communication.
BSD. Berkeley Software Distribution.
B–spline cubic curve. In computer graphics, a
cubic spline approximation to a set of four control
points having the property that slope and curvature
are continuous across sets of control points. See
also parametric cubic curve.
BTU. (1.) British thermal unit. (2.) In SNA, basic
transmission unit.
bucket. One or more fields that accumulate the
result of an operation.
bucket counts. The number of elements greater
than or equal to the lowest limit and less than or
equal to the higher limit.
buffer. (1.) A temporary storage unit, especially
one that accepts information at one rate and
delivers it at another rate. (2.) An adjustable
memory storage space, temporarily reserved for
performing input or output, into which data is read
or from which data is written.
buffer length. The maximum length of a data
segment that can be stored in a given buffer.
bug. An error in a program or a logic problem in
the intent of the program.
BUID. See bus unit identification.
instead of relying on the system software to set up
the system DMA controller, giving the device
greater flexibility in function and, in general, better
system performance than a DMA slave device. See
also DMA slave.
bus–out. A unidirectional data bus that is part of
the System 360/370 parallel–I/O interface. This bus
passes data from the host to the system unit.
bus unit identification. A field in the I/O Segment
register that is decode to select the IOCC for the
particular hardware implementation.
busy light. In CDE, a control that blinks when a
Front Panel action has been invoked prior to the
appearance of a window or when reloading actions.
build code. The program that runs the build
process to convert source files into a hypertext
database. The build code defines which items can
be built into hypertext and which cannot. For
example, an illegal font does not build because it is
not included in the build code.
button. (1.) A word or picture on the screen that
can be selected. Once selected and activated, a
button begins an action in the same manner that
pressing a key on the keyboard can begin an
action. (2.) Buttons include those on the keyboard,
mouse, lightpen, or buttons on the dial and button
box.
built–in function. A function known to the
compiler, whose code is incorporated directly into a
program module rather than referenced through a
library call.
button grabbing. Enacting an active grab using a
mouse button. See also grab, pointer grabbing, key
grabbing, passive grab, and active grab.
bulletin board. A graphic object that simulates a
real–life bulletin board in that it displays text and
graphic information in the form of messages to the
user from client applications that are currently
running.
bundle. A collection of software products available
for installation.
burst pages. On continuous–form paper, pages of
output that can be separated at the perforations.
bus. (1.) In a processor, a physical facility on which
data is transferred to all destinations but from
which only addressed destinations can read in
accordance with appropriate conventions. (2.) A
computer configuration in which processors are
interconnected in series. (3.) One or more
conductors that transmit signals or power.
bus–in. A unidirectional data bus that is part of the
System 360/370 parallel–I/O interface. This bus
passes data from the system unit to the host.
Bus Master. A device on the Micro Channel bus
that has its own built–in DMA controller instead of
using the system–provided DMA controller. This
allows the device to set up the DMA transfer itself
button press. The initiation of a function by
pressing a mouse button.
byte. (1.) The amount of storage required to
represent 1 character; a byte is 8 bits. (2.) A binary
character operated on as a unit and usually shorter
than one word. (3.) A string that consists of a
certain number of bits (usually 8) treated as a unit,
and that represents a character. (4.) A group of 8
adjacent binary digits representing 1 EBCDIC
character. (5.) In X.25, a byte is called an octet.
See also bit.
byte boundary. Memory addressing based on
8–bit intervals. Each memory location contains an
8–bit value that can range from 0 to 255 in decimal
notation.
byte constant. In FORTRAN, a named constant
that is of type byte.
byte order. In Enhanced X-Windows, the order of
bytes as defined by the server for pixmap or bitmap
data. Clients with different native byte ordering
must swap bytes as necessary.
byte type. In FORTRAN, a binary character
operated on as a unit and usually shorter than a
computer word.
Glossary
1-17
cache hit. A processor storage reference that is
satisfied by information from a cache.
C
C. Celsius or country.
C interface. The interface, defined at a level that
depends on the variant of C standardized by ANSI.
C language. A general–purpose programming
language that is the primary language of the
operating system.
C library. A system library that contains common C
language subroutines for file access, string
operators, character operations, memory
allocation, and other functions.
cache line. The cache component that is normally
loaded, stored, and interrogated during cache
lookup. See also set associativity.
cache line tag. The information kept with each
cache line to identify the part of virtual storage it
contains.
cache lookup. The process of determining
whether or not a cache contains the information
necessary to satisfy a storage reference. A defined
set of bits in the address being referenced
identifies the line or lines to be interrogated.
C++ language. A programming language based on
the C language and developed by Bjarne
Stroustrup. C++ defines data types called classes.
Classes provide data abstraction and are
composed of data (data members) and operations
that operate on that data (member functions). C++
also implements the object–oriented programming
concepts of inheritance through class derivation
and polymorphism through virtual functions and
overloading.
cache miss. (1.) A delay that occurs when the
CPU references data or instructions that are not
already in the data cache or instruction cache. (2.)
A processor storage reference that cannot be
satisfied from a cache and therefore requires a
RAM access.
C++ language statement. A C++ language
statement contains zero or more expressions. All
C++ language statements, except block
statements, end with a ; (semicolon) symbol. A
block statement begins with a { (left brace) symbol,
ends with a } (right brace) symbol, and contains
any number of statements.
Calculator. In CDE, a software application that
mimics the function of a handheld calculator.
C++ library. A system library that contains
common C++ language subroutines for file access,
memory allocation, and other functions.
cable. The physical media for transmitting signals;
includes copper conductors and optical fibers.
cache. (1.) A high–speed buffer storage that
contains frequently accessed data or instructions
and that can deliver that data or instructions faster
than the storage medium on which that information
usually resides. A cache is used to reduce access
time. See also write back cache. (2.) To place,
hide, or store in a cache. A technique (usually
software–based) whereby high–speed storage that
is not immediately required for other purposes is
used to retain data that has been loaded into it
once, in the hope that another request for the data
will occur before the high–speed storage must be
reassigned.
cache coherency. The need to ensure that
multiple threads on multiple processors changing a
single cache line do not create inconsistent
versions of the cache line in the different caches.
1-18
Glossary
CAD/CAM. Computer–Aided
Design/Computer–Aided Manufacturing.
CAI. See computer–aided instruction.
Calendar. In CDE, a software application that
enables you to schedule appointments and create
To Do lists.
Calendar view. In CDE, the day, week, month, or
year displayed in the main Calendar window.
call. (1.) To activate a program or procedure,
usually by specifying the entry conditions and
jumping to an entry point. See also load. (2.) In
data communications, the action necessary in
making a connection between two stations on a
switched line. (3.) In X.25 communications, a
conversation between two users.
call–accepted packet. In X.25 communications, a
call supervision packet transmitted by a called DTE
to inform the DCE of the acceptance of the call.
See also packet.
call–back. A characteristic of the UUCP file
USERFILE that tells a remote system whether the
local system it tries to access will call back to check
its identity.
call collision. See collision.
call–connected packet. In X.25 communications,
a call supervision packet transmitted by a DCE to
inform the calling DTE of the complete
establishment of the call. See also packet.
call redirection notification. In X.25
communications, an optional CCITT–specified
facility that informs the caller that the call has been
redirected to another DTE.
call request (CRQ). A signal sent by a computer to
request from data communications equipment that
a communications connection be established with
another computer in the network.
call–request packet. In X.25 communications, a
call supervision packet transmitted by a DTE to ask
for a call establishment through the network. See
also packet.
call user data (CUD). In X.25 communications,
data optionally included in the call–request packet
by the user application.
callback. (1.) A procedure that is called if and
when certain specified conditions are met. This is
accomplished by specifying the procedure in a
callback list. Synonymous with callback function.
See also callback routines. (2.) In SOM, a
user–provided procedure or method to the Event
Management Framework that gets invoked when a
registered event occurs. See also event.
callback function. Synonym for callback.
callback list. (1.) A list of procedures that are
called if and when certain specified conditions are
met. (2.) In AIXwindows, individual widgets can
define callback lists as required.
callback reason. The conditions that, if met, result
in a callback procedure being called.
callback routine address. The internal address of
a given callback routine.
callback routines. Procedures that are called if
and when certain specified conditions are met. See
also callback.
calling. In X.25 communications, an adjective
applied to the location or user that makes a call.
calling address. See network user address.
calling address extension. See address
extension.
calling conventions. Specified ways for routines
and subroutines to exchange data with each other.
calling DLS user. The data link service (DLS)
user in connection mode that initiates the
establishment of a data link connection.
calling NS user . A network services (NS) user
that initiates a network connection.
calling tree. The tree of control of a program. The
main procedure is the calling tree’s trunk; any
procedure referenced by the main procedure
branches off from the trunk, and any procedure
referenced by another procedure is a branch off
that branch. A branch that does not reference other
procedures is known as a leaf.
callout. A kernel parameter that establishes the
maximum number of scheduled activities that can
be pending simultaneously.
callout table. A kernel table that keeps track of all
sleeping processes and the channel on which each
is waiting.
cancel. To end a task before it is completed.
Cancel. In CDE, a push button that removes a
window without applying any changes made in that
window.
canonical processing. Processing that occurs
according to a defined set of rules. This is the style
of input that is typically used by the shell and
simple commands.
called. In X.25 communications, an adjective
applied to the location or user to which a call is
made.
caps. (1.) Capital letters, an uppercase font. (2.) A
printing style that uses two type sizes of a single
uppercase font. The smaller size is used instead of
a lowercase font.
called address extension. See address
extension.
caption. Text associated with, and describing, a
table or figure.
called DLS user. The data link service (DLS) user
in connection mode that processes requests for
connections from other DLS users.
capture. To digitize an image into the video
memory of the M–Video Capture Adapter.
called line address modified notification. In
X.25 communications, an optional CCITT–specified
facility.
called NS user . A network service (NS) with
whom a calling NS user wants to establish a
network connection.
called subaddress. See subaddress.
capture file. A file used by a communications
program to capture, or record, data coming in over
a connection to a remote system or device.
capture key. A toggle control key that starts or
stops the process of saving the data displayed on
the screen during an active connection.
card. An electronic circuit board that is plugged
into a slot in the system unit. See also adapter.
Glossary
1-19
cardinal spline cubic curve. In computer
graphics, a cubic spline whose endpoints are the
second and third of four control points. A series of
cardinal splines have a continuous slope and pass
through all but the first and last control points. See
also parametric cubic curve.
carriage return. (1.) In text data, the action that
indicates to continue printing at the left margin of
the next line. A carriage return is equivalent to the
carriage return of a typewriter. (2.) A keystroke
generally indicating the end of a command line.
carrier. In data communication, a continuous
frequency that can be modulated or impressed with
an information–carrying signal.
carrier sense multiple access with collision
detection (CSMA/CD). The generic term for a
class of medium access procedures that allows
multiple stations to access the medium at will,
without explicit prior coordination, and avoids
contention by way of carrier sense and deference.
Contention is resolved by way of collision detection
and transmission.
carrier signal. A signal with a constant frequency
that can be modulated to carry a data signal.
cascade button. In AIXwindows, a rectangular
graphic control that can be made to appear from
behind another graphic control to provide an
additional option or range of options.
cascading menu. A submenu of related choices
that is invoked when the parent item, is selected.
Usually, a choice that offers a cascading menu is
designated by an arrow to the right of the choice.
Similar to a context line.
case clause. In a C For AIX switch statement, a
case label followed by any number of statements.
CASE. Computer Assisted Software Engineering.
A set of tools or programs to help develop complex
applications.
CASE label. In Pascal, a value or range of values
that comes before a statement in a CASE
statement branch. When the selector is evaluated
to the value of a CASE label, the statement
following the case label is processed.
case label. The word case followed by a constant
expression and a colon. When the selector is
evaluated to the value of the constant expression,
the statements following the case label are
processed.
case–sensitive. Able to distinguish between
uppercase and lowercase letters.
cast. In C language, an expression that converts
the value of the operand to a specified scalar data
type (the operator).
1-20
Glossary
casted dispatching. In SOM, a form of method
dispatching that uses casted method resolution;
that is, it uses a designated ancestor class of the
actual target object’s class to determine what
procedure to call to execute a specified method.
casted method resolution. In SOM, a method
resolution technique that uses a method procedure
from the method table of an ancestor of the class
of an object (rather than using a procedure from
the method table of the object’s own class).
C.A.T. Computer–assisted typesetting.
catalog. A set of predefined components and
attributes used to create Interleaf documents.
catastrophic cancellation. A programming error
in which values with very large negative exponents
are added or multiplied together until a zero value
is produced, which is then propagated into
successive computations.
catch block. A block in a C++ program that
receives control when an exception matching its
argument is thrown. Each catch block is associated
with a try block.
cathode ray tube (CRT). A vacuum tube in which
a beam of electrons can be moved to draw lines or
to form characters or symbols on its luminescent
screen.
cause code. In X.25 communications, a 1–byte
code included in clear– and reset–indication
packets that indicates the origin of the packet and
the reason for sending it. Synonymous with clear
cause. See also diagnostic code.
CBEMA. Computer and Business Equipment
Manufacturers Association.
CCITT. Comite Consultatif International
Telegraphique et Telephonique. See also
Consultative Committee on International
Telegraphy and Telephone.
CCW. Channel control word. This is a defined
control encoding that is used to control the
operations of I/O units on the System 360/370
channel.
CD. Carrier detect. See also DCD.
CDE. An acronym for Common Desktop
Environment, a graphical user interface running on
UNIX.
CDLI. Common Data Link Interface. Device drivers
that interface with kernel services to provide
support for sockets and STREAMS interfaces.
CD–ROM. High–capacity read–only memory in the
form of an optically read compact disc.
CDS. Cell Directory Service.
CDS–defined attribute. A standard attribute that
CDS associates with names. A specific
CDS–defined attribute has the same meaning no
matter what type of entry (clearinghouse, directory,
object) it is associated with. However, different
types of entries can have different CDS–defined
attributes. For example, every CDS name has the
CDS–defined attributes of Creation Timestamp
(CDS_CTS), Update Timestamp (CDS_UTS), and
Access Control Set (CDS_ACS). In addition to
those attributes, a soft link has unique
CDS–defined attributes containing its expiration
time and the name it points to.
CDS directory. A logical unit for storing entries
under one name (the directory name) in a CDS
namespace. In addition to object entries, a
directory can contain soft links and child pointers.
You can copy, delete, and control access to a
directory. Each physical instance of a directory is
called a replica.
CDSPI. Cell Directory Service Portable Interface.
CDSTL. See connect data set to line.
CEC. Central Electronics Complex.
cell. The rectangular juncture of a horizontal row
and a vertical column. Examples include the cells
of an electronic spreadsheet and the cells utilized
by an XmRowColumn widget in an AIXwindows
graphic interface. In Interleaf, a table cell is actually
a modified frame that can contain data.
cell–relative name. See local name.
centered dot. A heavy bullet used as a mark to set
off a paragraph or list item.
central processing unit (CPU). The part of a
computer that includes the circuits that control the
interpretation and running of instructions.
CFM. Cubic feet per minute.
CGA. Color Graphics Adapter.
CGM. See Computer Graphics Metafile.
change bit. A bit in each page–frame table entry
that denotes the corresponding page has been
written to since the last time the operating system
cleared the page.
channel. (1.) A path along which signals or data
passes. (2.) The portion of a storage medium that
is accessible to a given reading or writing station.
(3.) In data communication, a means of one–way
transmission. (4.) A functional unit, controlled by a
host computer, that handles the transfer of data
between processor storage and local peripheral
equipment. (5.) The system element that controls a
single channel path, whose mode of operation
depends on the type of hardware to which it is
attached. (6.) A device connecting the processor to
input and output devices. (7.) One of 32 bits in a
table used to represent which event classes are
active or inactive. The most significant bit is called
channel 0 and the least significant bit is called
channel 31. See also logical channel.
channel control word. See CCW.
channel ID. A channel identification passed back
from a multiplexed device to the file system as a
result of calling the ddmpx entry point.
channel number. A number that identifies the path
by which data is transferred between a particular
input or output device and the processor of the
computer. The major device, minor device, and
channel numbers uniquely identify a hardware
device.
channel path. A single interface attaching one or
more control units.
channel–path Identifier (CHPID). In a
System/390 channel subsystem, a value assigned
to each installed channel path of the system that
uniquely identifies that path to the system.
char. In Object Database Manager, a terminal
descriptor used to define a variable as a
fixed–length, null–terminated string. See also
terminal descriptor.
char specifier. The keywords char and unsigned
char, which describe the type of data a variable
represents.
character. A letter, digit, or other symbol.
character cell. The physical width and height in
pels of a font. See also bounding box.
character class. (1.) Ranges of characters that
match a single character in the input stream. (2.) A
set of characters enclosed in sequence, or square
[], brackets.
character constant. (1.) A constant value whose
data attribute is character. (2.) In programming
languages, a character or an escape sequence
enclosed in single quotation marks.
character data indexing. An input/output
optimization that reduces I/O access time by
searching for a string in a small index file, and
using the obtained index to find a record in the
main data file.
character delete. In text data, the action that
erases the character at the current cursor location
and moves any trailing text one character position
to the left.
character device. A device that handles data one
character at a time. See also character special file.
Glossary
1-21
character display. A display that uses a character
generator to display predefined character boxes of
images (characters) on the screen. This kind of
display cannot address the screen any less than
one character box at a time. Contrast with All
Points Addressable display.
character expression. A character constant or
variable, character array element, character
substring, character–valued function reference, or
sequence of the preceding separated by the
concatenation operator, with optional parentheses.
character graphics. (1.) The visual representation
of a character, defined by toned or intoned picture
elements (pels). (2.) Graphics that are composed
of symbols printed in a monospace font. Some
symbols are standalone; others are intended for
assembling larger figures.
character key. (1.) A keyboard key that allows the
user to enter the character shown on the key. See
also function keys. (2.) In word processing, a
control used to process text one character at a
time.
character literal. A symbol, quantity, or constant in
a source program that is itself data, rather than a
reference to data. Contrast with numeric literal.
character position. On a display, the location of a
character.
character set. A group of characters used for a
specific reason; for example, the set of characters
a printer can print or a keyboard can support.
character special file. A special file that provides
access to an input or output device. The character
interface is used for devices that do not use block
I/O. See also character device, block file, special
file, and block special file.
character string. A sequence of consecutive
characters. In the C programming language, a
string must be null–terminated.
character substring. A contiguous portion of a
character string.
character translation. In international character
support, the dd command and various conversion
subroutines that translate between extended
characters and ASCII escape strings to preserve
unique character information.
character type. A data type that consists of
alphanumeric characters. See also data type.
character variable. In the C language, a data
object whose value can be changed during the
running of a program and whose data type is char
or unsigned char.
1-22
Glossary
characteristic attribute. A type of attribute that
reflects or affects the behavior of a software entity.
You generally can set or change characteristic
attributes.
charging requesting service. In X.25
communications, an optional facility that specifies
that charging information (segment count data,
monetary unit data, or call duration data) is
required.
chat script. In remote communications, a list of
expect–send sequences that a modem uses to
establish a communication link with another
modem. See also handshaking and expect–send
sequence.
checkbox. A small square box that can be turned
on or off to indicate the state of an option.
checkpoint. A snapshot of the current state of the
recoverable data being used by an application.
Checkpoints are used to capture the state of
recoverable data between backups, thus
minimizing the time involved in restarting systems
which use that data by providing a more recent
image of that data.
checksum. (1.) The sum of a group of data
associated with the group and used for checking
purposes. (2.) On a diskette, data written in a
section for error detection purposes.
child. (1.) Pertaining to a secured resource, either
a file or library, that uses the user list of a parent
resource. A child resource can have only one
parent resource. (2.) In the operating system, a
child is a process, started by a parent process, that
shares the resources of the parent process.
Contrast with parent. (3.) In Enhanced X-Windows
and AIXwindows, a first–level subwindow. A widget
managed by another widget is said to be the child
of the managing parent widget. For example,
Composite widgets typically manage the Primitive
children widgets attached to them. The parent
widget typically controls the placement of the child
as well as when and how it is mapped.
child class. A SOM class that inherits instance
methods, attributes, and instance variables directly
from another class, called the parent class, base
class, or superclass, or indirectly from an ancestor
class. A child class may also be called a derived
class or subclass.
child device. A hierarchical location term. It
indicates what can be connected to a parent
device. For example, an SCSI disk can be a child
device of an SCSI adapter.
child gadget. A windowless child widget. See also
child widget.
child process. In the operating system, a process,
started by a parent process, that shares the
resources of the parent process.
child resource. Pertaining to a secured resource,
either a file or library, that uses the user list of a
parent resource. A child resource can have only
one parent resource.
child widget. In AIXwindows and Enhanced
X–Windows, a widget managed by another widget
is said to be the child of the managing parent
widget. For example, Composite widgets typically
manage the Primitive children widgets attached to
them. The parent widget typically controls the
placement of the child as well as when and how it
is mapped. When a parent widget is deleted, all the
children controlled by that parent are automatically
deleted as well. See also child gadget.
children. Plural of child.
children spacing. In AIXwindows and Enhanced
X–Windows, widgets managed by another widget
are said to be the children of the managing parent
widget. The parent widget typically controls the
physical spacing and placement of the children
within the border of the parent.
choice. An option in a pop–up or menu used to
influence the operation of the system.
chord. In graphics, a short line segment whose
end points lie on a circle. Chords are a means for
producing a circular image from straight lines. The
higher the number of chords per circle, the
smoother the circular image.
CHPID. Channel path identifier.
CICS. See Customer Information Control System.
CID. See connection identifier.
ciphertext. The output of an encryption function.
Encryption transforms plaintext into ciphertext.
circuit. See virtual circuit.
circuit switching. A process that, on demand,
connects two or more data terminal equipments
(DTEs) and permits the exclusive use of a data
circuit between them until the connection is
released. Synonym for line switching. See also
packet switching.
C–ISAM. C–language Indexed Sequential Access
Method.
CLA. See communications line adapter.
class. (1.) Pertains to the I/O characteristics of a
device. In this operating system, devices are
classified as block or character. (2.) In Enhanced
X-Windows, a general group to which a specific
object belongs. See also widget class and class
record. (3.) In AIXwindows, an object–oriented data
structure containing generalized information about
a group of similar graphical objects known as
widgets or gadgets. Each class of graphical objects
inherits some or all of the appearance
characteristics and behavior characteristics of the
classes that precede it in the object hierarchy. (4.)
A C++ class is a user–defined data type. A class
data type can contain both data representations
(data members) and functions (member functions).
See also object class. (5.) In SOM, a way of
categorizing objects based on their behavior (the
methods they support) and shape (memory layout).
A class is a definition of a generic object. In SOM,
a class is also a special kind of object that can
manufacture other objects that all have a common
shape and exhibit similar behavior. The
specification of what comprises the shape and
behavior of a set of objects is referred to as the
”definition” of a class. New classes are defined in
terms of existing classes through a technique
known as inheritance. See also class object.
class data structure. A structure provided by the
SOM API to support efficient static access to
class–specific information used in dealing with
SOM objects. The structure’s name is
<className>ClassData. Its first component
(classObject) is a pointer to the corresponding
class object. The remaining components (named
after the instance methods and instance variables)
are method tokens or data tokens, in order as
specified by the class’s implementation. Data
tokens are only used to support data (public and
private) introduced by classes declared using
OIDL; IDL attributes are supported with method
tokens.
class key. One of the C++ keywords: class,
struct, and union.
class library. A collection of C++ classes.
class manager. An object that acts as a run–time
registry for all SOM class objects that exist within
the current process and which assists in the
dynamic loading and unloading of class libraries. A
class implementor can define a customized class
manager by subclassing SOMClassMgr class to
replace the SOM–supplied SOMClassMgrObject.
This is done to augment the functionality of the
default class–management registry (for example, to
coordinate the automatic quiescing and unloading
of classes).
class member operators. Used to access C++
class members through class objects or pointers to
class objects. They are ., –>, .*, and –>*.
Glossary
1-23
class method. Also known as factory method or
constructor.) A SOM class method is a method that
a class object responds to (as opposed to an
instance method). A class method that class <X>
responds to is provided by the metaclass of class
<X>. Class methods are executed without requiring
any instances of class <X> to exist, and are
frequently used to create instances of the class.
See also metaclass.
class name. (1.) For widgets and gadgets, the
name in the code corresponding to the resource
database containing the generic properties for all
objects in the class. (2.) A unique identifier of a
C++ class type that becomes a reserved word
within its scope.
class object. The run–time object representing a
SOM class. In SOM, a class object can perform the
same behavior common to all objects, inherited
from SOMobject. See also class.
class record. A particular widget record that
contains the data objects pertaining to the class of
any given widget. See also record, widget record,
and class.
class scope. The scope of C++ class members.
class template. A blueprint describing how a set of
related C++ classes can be constructed.
class variable. In SOM, instance data of a class
object. All instance data of an object is defined
(through either introduction or inheritance) by the
object’s class. Thus, class variables are defined by
metaclasses.
CLAW. See Common Link Access to Workstation.
clean up. The clean–up procedure instructs the
system to attempt to remove software products that
were partially installed. The system also attempts
to revert to the previous version of the removed
product. If the system successfully reverts to the
previous version, it becomes the currently active
version. If this cannot be done, then the software
product is marked as broken. After the clean–up
procedure is complete, you can attempt to install
the software again.
clean–up code. In loops that have been unrolled
or blocked, an additional loop or set of loops that
ensures that all iterations of the original code are
executed in the unrolled or blocked code.
clear. In X.25 communications, to reject a call (if it
has not yet been accepted) or end a call.
clear–confirmation packet. In X.25
communications, a packet transmitted by the DTE
to inform the DCE that a call has been cleared. See
also packet.
clear diagnostic. See diagnostic code.
clear–indication packet. In X.25 communications,
a call supervision packet transmitted by a DCE to
inform a DTE of the clearing of a call. See also
packet.
clear–request packet. In X.25 communications, a
call supervision packet transmitted by a DTE to ask
for a call to be cleared. See also packet.
clear user data. In X.25 communications, data
optionally included in the clear–request packet by
the user application.
click. In CDE, to press and release a mouse button
without moving the mouse pointer. Unless
otherwise specified, mouse button 1 is assumed.
client. (1.) In a distributed file system environment,
a system that is dependent on a server to provide it
with programs or access to programs. (2.) In
Enhanced X-Windows, an application program that
connects to an Enhanced X-Windows server by an
inter–process communication (IPC) path, such as a
Transmission Control Protocol (TCP) connection or
a shared memory buffer. The program can be
referred to as the client of the server, but it is
actually the IPC path itself. Programs with multiple
paths open to the server are viewed as multiple
clients by the protocol. See also inter–process
communication. (3.) In Enhanced X–Windows, a
Toolkit routine that uses a widget in an application
or for composing another widget. (4.) In
AIXwindows, a software application that fills the
role of the client in the traditional client–server
model upon which Enhanced X-Windows and
AIXwindows are based. See also client application.
(5.) In NCS, a program that uses an interface to
make remote procedure calls (RPCs).
client agent. See Location Broker Client Agent.
client application. A type of application. See also
client and application.
client code. (Or client program or client.) A SOM
application program, written in the programmer’s
preferred language, which invokes methods on
objects that are instances of SOM classes. In
DSOM, this could be a program that invokes a
method on a remote object.
clear cause. See cause code.
client program. A program that uses a C++ class.
The program is said to be a client of the class.
clear collision . A condition that occurs when a
STE and a DCE simultaneously transmit a clear
request packet and a clear indication packet over
the same logical channel. See also collision.
client–side caching. A high–speed buffer storage
that contains frequently accessed information
associated with a client application. The primary
1-24
Glossary
purpose of client–side caching is to reduce access
time to key information.
clip. In computer graphics, to remove those parts
of a display image that lie outside of a given
boundary.
clip list. In Enhanced X-Windows, a list of
rectangles designated for clipping.
clipboard. A storage space set aside for the
temporary storage and retrieval of text or graphics
during cut–and–paste operations. Data in the
clipboard is available to other applications.
clipboard selection. Data selected and pasted to
the clipboard that can be pasted or passed to a
function. Data can include such elements as text,
graphics, and widgets.
clipping. In GL, if a primitive overlaps the
boundaries of a window, it is clipped. The part of a
primitive that appears in the window is displayed
and the rest is ignored. There are several types of
clipping that occur in the system. Three–D drawing
primitives are clipped to the boundaries of a
frustum (for perspective transformations) or to a
rhombohedron (for orthographic projections). This
3–D clipping applies as well to the origin of
character strings, but not to the characters
themselves. A 2–D clipping is also performed,
where all drawing is clipped to the boundaries of
the AIXwindows window. The area of 2–D clipping
can be controlled with the screenmask. See also
clipping planes, fine clipping, gross clipping,
screenmask, bounding box, culling, transformation,
and window.
clipping planes. In GL, before clipping occurs,
primitive space is mapped to normalized device
coordinates. The clipping planes x=+/–w; y=+/–w;
or z=+/–w correspond to the left, right, top, bottom,
near, and far planes bounding the viewing frustum.
See also gross clipping, clipping and frustum.
clipping region. In Enhanced X-Windows, a type
of graphics output. In a graphics context, the image
defined by the bitmap or rectangles used to restrict
output to a particular region of a window.
CLK. See clock.
Clock. In CDE, a Front Panel control that displays
the local time.
clock (CLK). (1.) A device that generates periodic
signals used for synchronization. (2.) In data
communication, equipment that provides a time
base used in a transmission system to control the
timing of certain functions, such as sampling, and
to control the duration of signal elements.
clocking. (1.) In binary synchronous
communication, the use of clock pulses to control
synchronization of data and control characters. (2.)
In data communications, a method of controlling
the number of data bits sent on a communications
line in a given time.
clone device. A STREAMS device that returns an
unused major or minor device when initially
opened, rather than requiring the minor device to
be specified by name in the open call.
close. (1.) To end an activity and remove that
window from the display. (2.) A data manipulation
function that ends the connection between a file
and a program. Contrast with open.
closed user group (CUG). In X.25
communications, a subgroup of users that is
assigned to a facility that enables a member of one
subgroup to communicate only with other members
of the subgroup. A DTE can belong to more than
one closed user group. See also bilateral closed
user group and optional facility.
cluster. (1.) Any configuration of interconnected
workstations for the purpose of sharing resources
(for example, local area networks, host attached
workstations, and so on). (2.) A group of storage
locations allocated at one time. (3.) A station that
consists of a control unit (cluster controller) and the
workstations attached to it. (4.) A page–size
(4096–byte) buffer provided by the mbuf
management facility to the various layers of
communication software in AIX. (Also called
”cluster mbuf,” ”mbuf cluster,” and ”mapped page.”)
clustered file. Files in which records with adjacent
key values are physically clustered together. The
clustered file organization optimizes sequential
access through the primary index to records in the
file.
CMOS. Complementary metal–oxide
semiconductor. CMOS is a technology that
combines the electrical properties of n–type
semiconductors and p–type semiconductors.
coaxial cable. A cable consisting of one conductor,
usually a small copper tube or wire, within and
insulated from another conductor of larger
diameter, usually copper tubing or copper braid.
COBOL. Common business–oriented language. A
high–level programming language, based on
English, that is used primarily for business
applications.
code. (1.) Instructions to the computer. (2.) To write
instructions for the computer; to program. (3.) A
representation of a condition, such as an error
code.
code page. (1.) An assignment of graphic
characters and control function meanings to all
Glossary
1-25
code points. (2.) Arrays of code points representing
characters that establish the ordinal sequence
(numeric order) of characters. This operating
system uses 256–character code pages. See also
code point and extended character. (3) An ordered
set of up to 256 predefined display symbols. The
first 32 code points of each code page are
reserved for control codes and are the same for all
code pages, leaving up to 224 distinct display
symbols per page.
code point. A character within a code page. See
also code page and extended character.
code segment. See segment.
code server. A system that is providing a code
service for other computers on a network.
code set. In the XPG4 system interface, a set of
unambiguous rules that establish a character set
and the one–to–one relationship between each
character of the set and its bit representation.
col. A typesetter postprocessor that buffers typeset
output to allow printing on printers and workstations
that do not support backscrolling.
collapse. To remove the contents of a directory
from the display (close it) using the CDS Browser.
To collapse an open directory, you double–click on
its icon. Double–clicking on a closed directory
expands it.
collating element. One or more characters that
match a sequence in a regular expression.
collating sequence. The sequence in which
characters are ordered within the computer for
sorting, combining, or comparing.
collation. The process of character and string
sorting based on alphabetical order and
equivalence class.
collation table. Provides an ordered character set
and character equivalence classes used by
functions.
collection. In Ada language, the entire set of
objects created by evaluation of allocators for an
access type.
colliding find request. A condition that occurs
when two link stations attempt to call each other at
the same time.
collision. (1.) An unwanted condition caused by
concurrent transmissions on the medium that
results in garbled data. (2.) In X.25
communications, a condition that occurs when a
DTE and a DCE simultaneously transmit packets
(for instance, a clear–request packet and a
clear–indication packet) over the same logical
1-26
Glossary
channel. This can be a clear collision, call collision,
or reset collision. See also clear collision.
colon format. A format into which data files can be
organized. Each data record consists of one line in
the colon file, and data fields in each data record
are separated by colons.
color cell. In Enhanced X-Windows, an entry in a
colormap that consists of three values based on
red, green, and blue intensities. The values are
16–bit, unsigned numbers. Zero represents the
minimum intensity. The values are scaled by the
server to match the particular display in use.
color display. A display device capable of
displaying more than two colors and the shades
produced by combinations of two colors, as
opposed to a monochrome display.
color expansion operation. A graphics
programming operation that occurs automatically
when the source pixel map data area contains only
1 byte per pixel and the destination pixel map data
area is a color display adapter buffer frame defined
to have more than 1 bit per pixel.
color graphics adapter. An adapter that allows a
computer to use a color display.
color lookup table. Synonym for color map.
color map. (1.) In computer graphics, a lookup
table where each index is associated with a red,
green, and blue value. Synonymous with color
lookup table, color palette, and color table. (2.) In
Enhanced X-Windows, a set of color cells. A pixel
value indexes the color map to produce
RGB–value intensities. A color map consists of a
set of entries defining color values that, when
associated with a window, is used to display the
contents of the window. Depending on hardware
limitations, one or more color maps can be installed
at one time such that windows associated with
those maps display correct colors. The two classes
of color maps are direct color and pseudocolor. (3.)
In GL, a lookup table that translates color indexes
into RGB triplets. The lookup table is sandwiched
between the frame buffer and the digital–to–analog
converters (DACs) and serves to translate the color
index value stored in the frame buffer into the red,
green, and blue values required by the DACs. On
most hardware configurations, the color map is
either 8 or 12 bits deep, allowing the simultaneous
display of 256 or 4096 colors. On most hardware
configurations, the DACs have an 8–bit per color
accuracy, allowing the user to choose among
16,777,216 colors.
color map mode. A configuration of the hardware
that passes the values stored in the frame buffer
through a color lookup table (color map), from
which the red, green, and blue values are obtained
for display. Entries in the color map are referred to
as color indexes. In color map mode, the values
stored in the frame buffer are treated as color map
indexes. See also RGB mode.
color palette. Synonym for color map.
color ramp. A progression of colors in a color map.
Most color ramps are smooth and have only a
small number, if any, of discontinuities. For
instance, if the full set of colors of the rainbow were
loaded into the color map, that would constitute a
color ramp.
color table. Synonym for color map.
color viewer. In AIXwindows, an interface that
allows the user to choose a color as a value for a
widget property.
column. A vertical arrangement of characters or
other expressions.
column headings. Text appearing near the top of
a column of data for the purpose of identifying or
titling the data in the column.
column inch. A unit of measure for printed text.
One column inch is the amount of text contained in
an inch of type depth, one column wide.
column–major order. A way of storing array
elements such that the leftmost subscript varies
most rapidly as memory–adjacent elements are
accessed.
combined I and D cache. A cache that contains
both instructions and data, distinguishable only by
the cache line tag.
comma expression. An expression that contains
two operands separated by a comma. Although the
compiler evaluates both operands, the value of the
right operand is the value of the expression. If the
left operand produces a value, the compiler
discards this value.
command. (1.) A request to perform an operation
or run a program. When parameters, values, flags,
or other operands are associated with a command,
the resulting character string is a single command.
(2.) In data communication, an instruction
represented in the control files of a frame and
transmitted by a primary or combined station. It
causes the addressed station to run a data link
control function.
command frame. A link–level frame or packet that
is serviced as a command and (in most cases)
expects a response.
command history. An automatic listing of
previously issued commands.
command interpreter. A program that sends
instructions to the kernel. Synonym for interface.
See also shell.
command line. The area of the screen where
commands are displayed as they are typed.
command line editing keys. Keys for editing the
command line.
command mode. A state of a system or device in
which the user can enter commands. See also text
input mode.
command module. A file that executes a
command or process. The file may be activated
when the user enters a command at the command
line or by another command module.
command name. (1.) The first or principal term in
a command. A command name does not include
parameters, values, flags, or other operands. (2.)
The full name of a command when an abbreviated
form is recognized by the computer (for example,
print working directory for pwd).
command programming language. Facility that
allows programming by the combination of
commands rather than by writing statements in a
conventional programming language.
command string. A request to perform an
operation, along with the operands that provide all
instructions needed for running the operation.
command substitution. The ability to capture the
output of any command as a value to another
command by placing that command line within ‘ ‘
(grave accents). The shell first runs the command
or commands enclosed within the grave accents
and then replaces the whole expression, including
grave accents, with their output. This feature is
often used in assignment statements.
command word. The name of the 16–bit units
used for storing graphic primitive strings. The first
command word determines the primitive type and
sets the length of the string. Subsequent command
words contain information in multiples of quid, or 4
bits of data.
commit. (1.) To make permanent all changes that
have been made to the database file since the last
commitment operation and to unlock the records so
they are available to other users. Contrast with
reject. (2.) When you commit software, you are
making a commitment to that version of the
software product. When you commit a product, the
saved files from all previous versions of the
software product are removed from the system,
thereby making it impossible to return to a previous
version of the software product. In SMIT, software
can be committed at the time of installation by
setting the COMMIT software? question to yes (or
Glossary
1-27
by using the –ac flags with the installp command).
Note that committing already applied software does
not change the currently active version of the
software product. It merely removes saved files for
the previous version of the software product. The
rejection of the installation level of the product does
not have the same meaning as the rejection of
updates to the product. Once you commit a new
version of a product, you must reinstall the
previous version if you want to use that version
again. Compare to apply and contrast with reject
and remove.
commit operation. An operation that saves a file
to permanent storage.
common block. In FORTRAN, a storage area that
can be referred to by a calling program and one or
more subprograms.
common carrier. Any government–regulated
company that provides communication services to
the general public.
Common Link Access to Workstation (CLAW).
The architecture that defines the channel
commands used between the host and the channel
attachment adapter.
common subexpression enhancement. An
optimization that enables a compiler to detect that
two or more distinct subexpressions within an
expression or loop are identical and need only be
computed once.
communications. The transmission of data
according to a protocol between computers or
remote devices, usually over a long distance.
communications adapter. A circuit card with
associated software that enables a processor,
controller, or other device to be connected to a
network. See also adapter.
communications authority password. One of the
two communications security passwords. It controls
access to communication configuration menus so
that only authorized persons can change the
profiles, encrypt a portion of the communication
profile database, or control the startup of SNA
processes. The password must be a
30–to–80–character phrase, with interior blanks
allowed. See also BIND password.
communications channel. An electrical path that
facilitates transmission of information from one
location to another.
communications co–processor. A
microprocessor on an expansion board that
supplements the operations of the processor in the
system unit, enabling a computer to use
communication services in parallel with other
operations.
1-28
Glossary
communications endpoint. In X.25, the local
communication channel between a DLS user and a
DLS provider.
communications line. The line over which data
communications take place; for example, a
telephone line. See also X.25 line.
communications line adapter (CLA). A functional
unit that converts the serial–by–bit output of a
station to a parallel bit form and from a parallel bit
form to serial–by–bit input to a station. See also
line adapter.
communications link. See data link.
communications service. The service performed
by the Sockets Application Programming Interface,
which allows data packets to be delivered to the
specified destination. There are three types of
communications services offered: reliable stream
delivery, connectionless datagram delivery, and
raw socket delivery.
compatibility. (1.) The ability to perform tasks
identically in different environments without major
modifications. (2.) The capability of a functional unit
to meet the requirements of a specified interface.
compatible. Pertaining to computers on which the
same program can be run without appreciable
alteration.
compatible types. Different data types that can be
operands for the same operation.
compilable unit. In Pascal, synonymous with
compilation unit. See also unit.
compilation. In Ada language, a compilation is
generally the translation of an Ada source program
into an executable object module. When using the
Ada language debugger, a compilation consists of
one or more compilation units in a single file. If you
include three package specifications and two
package bodies in one file, that file represents one
compilation consisting of five compilation units:
three library units and two secondary units. There
is usually only one compilation unit in a
compilation.
compilation time. The time during which a source
program is translated from a high–level language
into a machine language.
compilation unit. A portion of a computer program
sufficiently complete to be compiled correctly. In
Pascal, there are two types of units: the program
unit and the segment unit. In Ada language, a
compilation unit is the declaration or the body of a
program unit, presented for compilation as an
independent text. It is optionally preceded by a
context clause, naming other compilation units
upon which it depends by means of one more with
clauses. See also compilable unit and external
variable.
compile. To translate a program written in a
high–level programming language into an
intermediate language, assembly language, or a
machine language. See also interpreted routine.
compiler. (1.) A program that translates a source
program into an executable program (an object
program). (2.) A program that translates
instructions written in a high–level programming
language into machine language.
compiler directing statement. Synonym for
compiler directive.
compiler directive. A statement that controls what
the compiler does rather than what the user
program does.
complement of a number. The value that when
added to the number equals a given value.
complete class name. The complete qualification
of a nested C++ class name including all enclosing
class names.
complete overwrite installation. An installation
method that completely overwrites an existing
version of BOS that is installed on your system.
This procedure may impair recovery of data or
destroy all existing data on your hard drives. Be
sure to back up your system before doing a
complete overwrite installation.
complete packet sequence. Either an individual
X.25 data packet or a sequence of packets with the
M–bit set to 1 and the D–bit set to 0, followed by a
further data packet with the M–bit set to 0 and the
D–bit set as required.
complex constant. In FORTRAN, an ordered pair
of real or integer constants separated by a comma
and enclosed in parentheses. The first constant of
the ordered pair represents the real part of a
complex number; the second represents the
imaginary part.
Complex Mathematics Library. A C++ class
library that provides the facilities to manipulate
complex numbers and perform standard
mathematical operations on them.
complex number. A number consisting of an
ordered pair of real numbers, expressible in the
form a+bi, where a and b are real numbers and i
squared equals minus one. A complex number is
made up of two parts: a real part and an imaginary
part, where a is the value of the real part and b is
the value of the imaginary part and where i is the
square root of –1.
complex type. In FORTRAN, a data type that
represents values of complex numbers. A value is
expressed as an ordered pair of real data items
separated by a comma and enclosed in
parentheses. The first item represents the real part
of the complex number, and the second item
represents the imaginary part.
component. (1.) One part of a structured type or
value, such as an array element or a record field.
(2.) In AIXwindows or Enhanced X-Windows, the
widget, gadget, or other graphical object that
makes up an interactive user interface. (3.) In Ada
language, a value that is a part of a larger value, or
an object that is part of a larger object.
component bar. In an Interleaf document, the
black bar at the left margin that contains the
component identifiers for the components
contained in that document.
component dump table. A structure used by
kernel components to identify data structures that
should be collected by the kernel dump program.
compose. To set type.
Compose window. In CDE, in Mailer, the window
you use to create new electronic mail messages.
Several message–composing options are available
from the Compose window menu bar.
Composite Manager. In AIXwindows, a manager
widget with special knowledge about the handling
of one or more of its children widgets. Normally, a
manager widget has no knowledge of its children,
but a TitleBar widget and a ScrollBar widget can
be registered as children of a certain type of
Composite Manager widget known as a Panel
widget, and the Panel widget will correctly control
the positioning of the TitleBar and ScrollBar
widgets.
composite type. In Ada language, a composite
type is one whose values have components. There
are two kinds of composite type: array types and
record types.
composite video. The combined luna, chroma,
and sync signals in accordance with the NTSC
standards in the U.S., and the PAL standards in
Europe. Also called NTSC or PAL (Europe).
composite widget. In Enhanced X-Windows, a
widget that is a container for an arbitrary,
implementation–defined collection of children.
These children may be instantiated by the
composite widget itself, by other clients, or by a
combination. Composite widgets contain methods
for managing the geometry (layout) of any child
widget. A composite widget is a subclass of the
Core widget. See also widget.
Composite widget class. In Enhanced
X–Windows, a metaclass that does not instantiate
any widgets of its own but provides the resources
Glossary
1-29
and functionality that allow parent widgets to
manage the layout and mapping of their children
widgets and gadgets.
compound license. In License Use Management,
a type of license that allows a system administrator
to generate license passwords for a given number
of licenses. Such a license is valuable when an
administrator needs a certain number of licenses,
but does not yet know what machines or who will
use them. A compound license can generate either
nodelocked or non–nodelocked licenses, not both.
compound object. In AIXwindows, a graphical
object made up of several widgets and gadgets
collected within a single container widget.
compound string. A type of string designed to
simplify foreign language support by allowing text
to be displayed without hard–coding the
language–dependent attributes (character set, text,
and direction).
compress. (1.) To move files and libraries together
on disk to create one continuous area of unused
space. (2.) In data communications, to delete a
series of duplicate characters in a character string.
compressed output. Synonym for compression.
compression. (1.) A technique for removing
strings of duplicate characters, gaps, empty fields,
and trailing blanks before transmitting data.
Synonymous with compressed output. (2.) In SNA,
the replacement of a string of up to 64 characters
by an encoded control byte to reduce the length of
the data stream sent to the LU–LU session partner.
computational memory. The set of all
virtual–memory pages in real memory that are part
of working–storage or program–text segments.
computed time. The result of the synchronization
process––the time value that the clerk or server
process computes according to the values it
receives from several servers.
computer aided instruction (CAI). A data
processing application in which a computing
system is used to assist in the instruction of
students.
Computer Graphics Metafile. A
device–independent graphics file format used for
storing object–oriented graphics.
computer instruction. An instruction that can be
recognized by the processing unit of the computer
for which it is designed. Synonymous with machine
instruction.
computer language. Synonym for machine
language and machine instruction.
computer word. Synonym for word.
1-30
Glossary
concatenate. (1.) To link together. (2.) To join two
character strings.
concatenation. (1.) Linking together. (2.) Joining
two character strings. (3.) In GL, combining a
series of geometric transformations such as
rotations, translations, and scaling. Concatenation
of transformations corresponds to matrix
multiplication.
concave and convex polygons. In computer
graphics, a polygon is convex if a line segment
joining any two points in the figure is completely
contained within the figure. Nonconvex polygons
are sometimes called concave. Algorithms that
render only convex polygons are much simpler
than those that can render both convex and
concave polygons.
concentrator. An FDDI node that has additional
parts beyond those required for its own attachment
to a FDDI network. These additional parts (type M)
are for attaching other FDDI nodes (type S) in a
tree topology. Primarily, a concentrator is used to
allow more than two single attachment stations
(SAS) to communicate. It can also connect multiple
SAS to a dual attachment station (DAS) ring.
concrete class. An OM class of which instances
are permitted.
concurrent–use license. In License Use
Management, a type of license administered by the
license server that can be used by different users
at any node that is connected to a license server
node. Concurrent–use licenses allow as many
users to use a software product concurrently as
there are licenses.
condensed print. A print format where characters
are smaller and spaced closer together
horizontally, typically at a density of 17 characters
per inch.
condition. An expression in a program or
procedure that can be evaluated to a value of
either true or false when the program or procedure
is running.
condition code. Synonym for flag.
conditional. Conditionals test for certain
circumstances to carry out particular commands.
conditional branch. A branch that is taken when a
specified condition is met.
conditional compilation statement. A
preprocessor statement that causes the
preprocessor to process specified code in the file
depending on how a specified condition evaluates.
conditional expression. A C language expression
that contains a condition (the first expression), an
expression to be evaluated if the condition has a
nonzero value (the second expression), and an
expression to be evaluated if the condition has the
value 0 (zero).
configure. To describe to a system the devices,
optional features, and program products installed
on a system.
conditional statement. (1.) A statement that runs
if a specified expression evaluates to a nonzero
value. (2.) A statement that permits execution of
one of a number of possible operations, with or
without a transfer of control. (3.) A statement used
to express an assignment or branch based on
specified criteria.
configure method. Takes a device from the
defined state to the available state. If a device has
a device driver, the configure method is responsible
for loading and binding the driver into the kernel. If
the device supports the optional stopped state, the
configure method takes the device from the defined
state to the stopped state.
condition variable. A synchronization object used
in conjunction with a mutex. A condition variable
allows a thread to block until some event happens.
confirm. In X.25 communications, to respond to
the arrival of a clear–indication or reset–indication
packet.
conditioning. (1.) The use of indicators to control
when calculations or output operations are to be
performed. (2.) In data communications, the
addition of equipment to a nonswitched
voice–graded channel to provide minimum values
of line characteristics required for data
transmission.
CONFIRM. A request that asks the remote
transaction program to tell whether the last
transmission was received successfully.
conduit. A pipe for protecting electrical wires or
cables.
configuration. (1.) The group of machines,
devices, and programs that make up a data
processing system or network. (2.) The process of
describing to a system the devices, optional
features, and program products that have been
installed so that these features can be used.
Contrast with customization and system
customization.
Configuration Assistant. A graphical interface
application used to perform post–installation
system configuration tasks.
configuration feedback window. In AIXwindows,
a window displayed in the center of the screen
when AIXwindows Manager is restarted or when a
behavior switch is requested. The window contains
such variables as the size and location of a client
window.
configuration file. A file that specifies the
characteristics of a system or subsystem; for
example, the operating system queueing system.
configuration manager. A program to supervise
device configuration during initial program load
(IPL).
configuration operation/procedure. The
multistep process, performed in the host computer,
of constructing a configuration image for a 3601
Finance Communication Controller.
Configuration Rules Object Class. An object
class that contains the configuration rules used by
the configuration manager during initial program
load (IPL).
confirmation. A transmission by a receiver that
permits a sender to continue.
CONFIRMED. A response to the CONFIRM
request indicating that the remote site received the
transmission without detecting any errors.
conformant string. In Pascal, a string whose
declared length does not match that of a formal
parameter. See also formal parameter.
congruence class. In a cache, the group of lines
to which a given memory location can be mapped.
connect. In X.25 communications, to connect a
port to the X.25 network.
connect data set to line (CDSTL). In SNA, an
option that determines how the data terminal ready
(DTR) signal to the modem operates. It is used if
DTR indicates an unconditional command from the
DTE (data terminal equipment) to the attached
DCE (data circuit–terminating equipment) to
connect to or remove itself from the network.
connect–time accounting. The record of the
amount of time each user spends logged in to the
system.
connected unit. In FORTRAN, a unit that is
connected to a file by either an OPEN, READ, or
WRITE statement.
connection. (1.) In SNA, the network path that
links together two LUs in different nodes to provide
communications channels between them for the
application programs running at the respective
LUs. (2.) In X.25 communications, the existence of
a virtual circuit between two data terminal
equipments (DTEs). A switched virtual circuit
(SVC) connection is for the duration of a call; a
permanent virtual circuit (PVC) connection is a
permanent connection between the DTEs. (3.) In
Enhanced X-Windows, the IPC path between the
server and a client program. A client program
Glossary
1-31
typically, but not necessarily, has one connection to
the server over which requests and events are
sent. (4.) In system communications, a
communication link over which data can be passed
between two systems or between a system and a
device.
connection close. All events made by the client
are discarded and the server resets its state to
having no connections.
connection establishment. The phase in
connection mode that enables two data link service
(DLS) users to create a data link connection
between them.
connection identifier (CID). (1.) A value used to
identify a resource. The value is returned to the
connecting program after connect processing has
established a session and must be used on
subsequent requests to the resource. (2.) In the
X.25 API, the name used to identify a call that has
been made or received.
connection key. Identifies a subclass of devices
that can connect to the intermediate device at the
specified location.
connection location. Identifies a specific location
on the intermediate device where a child device
can be connected.
connection management stream. In X.25, a
special stream that receives all incoming connect
indications destined for DLSAP addresses that are
not bound to any other streams associated with a
particular PPA.
connection mode. A circuit–oriented mode of
transfer in which data is passed from one user to
another over an established connection in a
sequenced manner.
connection–oriented protocol. A
connection–based, reliable, virtual–circuit transport
protocol, such as TCP; an RPC protocol that runs
over a connection–based transport protocol.
connection profile. A data management file that
contains parameters that associate other defined
profiles to the connection of two logical units.
connection type. This is a field in the Predefined
Connection Object Class. For an intermediate
device, it identifies the subclass of devices that can
be connected to it.
information individually and does not guarantee
delivery.
connectivity. An algorithm that determines if two
machines on different networks can communicate.
If the machines can communicate, connectivity also
determines which host names should be used and
which TCP/IP routing information must be added.
connector. (1.) An electrical part used to join two
other electrical parts. (2.) A flowchart symbol that
represents a break in a flow line and indicates
where the flow line is continued. (3.) A means of
establishing electrical flow.
consistent. Pertaining to a file system, without
internal discrepancies.
console. The main operating system display
station. Synonym for system console.
console bell. Synonym for BEL.
console device. During the installation of the Base
Operating System (BOS), the system console is
the display device at the system on which you are
installing the software.
console display. A display at a system console on
which an operator can display, send, and reply to
messages and use all control commands.
constant. A data item with a value that does not
change during the running of a program. Contrast
with variable. For Ada programming, see also
object.
constant expression. An expression having a
value that can be determined during compilation
and that does not change during the running of the
program.
constant folding. Performing operations in which
operands are all constants at compilation time and
treating the results as constants. See also fold.
constant–width characters. A character set
designed so each character is the same width as
the other characters.
constraint. In Ada language, a constraint
determines a subset of the values of a type. A
value in that subset satisfies the constraint.
connectionless mode. A mode of transfer in
which data is passed from one user to another in
self–contained units with no logical relationship
required among the units.
Constraint. In AIXwindows, a class of objects from
which a unique resource set can be inherited. For
example, a PanedWindow widget can specify the
size of its children by using the inherited XtNmin
and XtNmax Constraint resources. The reference
material associated with each widget specifies
those that inherit resources from the Constraint
class.
connectionless packet delivery. A method of
data packet delivery that treats each packet of
constraint widget. In Enhanced X-Windows, a
widget that is a subclass of a composite widget. It
1-32
Glossary
manages the geometry of its children based on
constraints associated with each child.
SOM–supplied methods require context
parameters.
constructor. A special C++ member function that
has the same name as a class. It is used to
construct class objects and may initialize them.
context line. In the Performance Toolbox, menu
items ending in a slash and three dots (/...). The
slash and three dots signify that the line itself
represents a list at the next hierarchical level.
Contrast with statistic line. See also cascading
menu.
Consultative Committee on International
Telegraphy and Telephone (CCITT). A United
Nations Specialized Standards group whose
membership includes common carriers concerned
with devising and proposing recommendations for
international telecommunications representing
alphabets, graphics, control information, and other
fundamental information interchange issues.
contact port. Synonym for well–known port.
container. In CDE, a control intended to hold
objects or data. A folder and a notebook are
examples of containers. In Mailer, your electronic
mailbox and filing system that contains all mail
messages. Once a message is put in a container,
you can display, modify, delete, print, include,
forward, and reply to it.
containment. A pointer is ”contained” if the pointer
is located in the window, and not within an inferior
of the window, and the cursor hotspot is within a
visible region of a viewable window or one of its
inferiors. The border of the window is considered
part of the window.
contention. (1.) In a local area network, a
condition on a communications channel when two
or more stations are allowed by the protocol to start
transmitting concurrently and thus risk collision. (2.)
A condition on a session when two programs try to
start a conversation at the same time.
contention scope. The group of threads against
which a given thread must compete for the CPU. If
local, the thread competes against other threads in
the same process. If global, the thread competes
against all other threads in the system.
context address. A regular expression enclosed in
slashes (/).
context clause. For Ada programming, see
compilation unit.
context expression. In SOM, an optional
expression in a method’s IDL declaration,
specifying identifiers whose value (if any) can be
used during SOM’s method resolution process
and/or by the target object as it executes the
method procedure. If a context expression is
specified, then a related Context parameter is
required when the method is invoked. (This
Context parameter is an implicit parameter in the
IDL specification of the method, but it is an explicit
parameter of the method’s procedure.) No
context structure. An ordered group of variables
specifying the interface properties (notably
location) of a shadow widget.
continuation line. A line of a source statement
into which characters are entered when the source
statement cannot be contained on the previous
lines.
continuation reference. A continuation reference
describes how the performance of all or part of an
operation can be continued at a different DSA or
DSAs.
continue statement. A C language control
statement that contains the keyword continue and
a semicolon.
control. In CDE, a generic term for a variety of
elements (such as buttons, check boxes, and scroll
bars) that perform an action or indicate an option
setting. See Front Panel control.
control block. A storage area used by a program
to hold control information.
control character. (1.) A character that is not a
graphic character such as a letter, number, or
punctuation mark. Such characters are called
control characters because they frequently act to
control a peripheral device. RETURN and
FORM–FEED are control characters that control a
workstation or printer. Synonymous with
nonprinting character. (2.) The Ctrl key on the
keyboard. (3.) A character, occurring in a particular
context, that initiates, modifies, or stops any
operation that affects the recording, processing,
transmission, or interpretation of data (such as
carriage return, font change, and end of
transmission). (4.) A nonprinting character that
performs formatting functions in a text file.
control commands. Commands that allow
conditional or looping logic flow in shell procedures.
control state. A state that represents the current
network installation management (NIM) operation
being performed on a machine. This state is one of
two machine states.
control key. (1.) The keyboard key labeled Ctrl.
(2.) A key combination, made by pressing the Ctrl
Glossary
1-33
key followed by another key on the keyboard, that
performs a function or makes a special character.
Convenience functions are included in the
AIXwindows Toolkit.
control path. The set of line, hardware, and
control disciplines that determine the current
characteristics of a particular TTY.
convenience interface. An interface created by an
AIXwindows convenience creation subroutine. See
also convenience creation subroutine.
control point profile name. The name of the
control point profile that defines the node ID of the
physical unit associated with the attachment.
converged peripheral node. In SNA, a type of
physical unit that has limited addressing and path
control routing capabilities. It provides general
connectivity to other SNA nodes and supports
parallel sessions, multiple sessions per LU, primary
and secondary LUs, and multiple lines per node.
control points. In computer graphics, points in
real space that control the shape of a spline curve.
The system provides hardware support for wire
frame rational cubic splines, and for NURBS
surfaces, the specifications of which require four
control points.
control program (CP). Part of the operating
system that determines the order in which basic
functions should be performed.
control statement. In programming languages, a
statement that is used to alter the continuous
sequential execution of statements. A control
statement can be a conditional statement or an
imperative statement.
control station. The primary or controlling
computer on a multipoint line. The control station
controls the sending and receiving of data.
control unit terminal (CUT) mode. A protocol
used for communications with a 3174/3274
Controller or other appropriate interface unit. In this
protocol, a program in the workstation is emulating
a 3278/79 terminal for a user, and the interface unit
is responsible for enforcing the protocol.
controlling terminal. This term refers to an active
workstation at which a user is authorized to enter
commands that affect system operation. The
controlling terminal for any process normally is the
active workstation from which the process group for
that process was started. A workstation can have
no more than one controlling process group and a
process group can have no more than one
controlling terminal. The controlling process group
receives certain interrupt signals from the
controlling terminal.
convenience creation subroutine. Creates
certain useful combinations of widgets known as
convenience widgets or convenience dialogs,
including the appropriate Shell widgets where
necessary. See also convenience interface.
convenience dialog. A widget or collection of
widgets created by an AIXwindows Dialog
convenience subroutine.
convenience function. A function that performs a
frequently needed series of tasks automatically to
create or manage widgets or other code structures.
1-34
Glossary
conversation. (1.) In SNA, the logical connection
between a pair of transaction programs for serially
sharing a session between type 6.2 logical units
from transaction to transaction. While a
conversation is active, it has exclusive use of an
LU–LU session as delimited by a distinct bracket;
successive conversations may use the same
session. (2.) An interchange of information
between two application programs. (3.) A pathway
between two application programs that allows them
to exchange information. (4.) Interaction between a
computer and a user by means of a keyboard.
conversation correlator. An internal SNA
identifier used by the LU services to track which
applications are using which conversations. An
identifier of 1 to 8 bytes that is assigned by the
attach function and maintained by LU services.
conversation key. A short–lived encryption key
provided by the Authentication Service to two
principals for the purpose of ensuring secure
communications between them. See also session
key.
conversation mode. A mode of operation of a
computer system in which a sequence of
alternating entries and responses between a user
and the system takes place in a manner similar to a
dialog between two persons.
conversion. (1.) In programming languages, the
transformation between values that represent the
same data item but belong to different data types.
(2.) A change in the type of value. For example,
when you add values having different data types,
the compiler converts both values to the same form
before adding them. See also transaction program.
conversion code. In a print function call, a
specification of the type of the value, as the value
is to be printed (in octal format, for example).
conversion function. A C++ member function that
specifies a conversion from its class type to
another type.
conversion specification. In a print function call,
a specification of how the system is to place the
value of zero or more format parameters in the
output stream. Each conversion specification
contains a % (percent) symbol that is followed by
conversion modifiers and a conversion code.
converter. A device that converts data from one
form to another without altering the underlying
information.
converter cache. A high–speed buffer storage that
contains frequently accessed information
associated with a client application. The primary
purpose of a converter cache is to reduce access
time to key information.
coordinate system. A given convention for
locating pixels on a given display or window,
where, in AIXwindows, X is the horizontal axis and
Y is the vertical axis. The origin is [0,0] at the
upper–left or lower–left corner, depending on the
convention in use. For a window, the origin is at the
upper left or lower left (depending on the
convention in use), inside the border. Coordinates
are discrete and specified in pixels. Each window
and pixmap has its own coordinate system.
coprocessor. (1.) A supplementary processor that
performs operations in conjunction with another
processor. (2.) In personal computers, a
microprocessor on an expansion board that
extends the address range of the processor in the
system unit or adds specialized instructions to
handle a particular category of operations.
copy. (1.) The action by which the user makes a
whole or partial duplicate of an already existing
data object. (2.) Either a copy of an entry stored in
other DSAs through bilateral agreement, or a
locally and dynamically stored copy of an entry
resulting from a request (a cache copy).
copy constructor. A C++ constructor used to
make a copy of a class object from another class
object of the same class type.
copy–link. A link established between a target file
and the copied version of the same file. Any
changes made to the copied version of the target
file are automatically made to the original target
file.
copy–on–write. An option that creates a mapped
file with changes that are saved in the system
paging space, instead of saving the changes to the
copy of the file on the disk.
CORBA. In SOM, the Common Object Request
Broker Architecture established by the Object
Management Group. IBM’s Interface Definition
Language used to describe the interface for SOM
classes is fully compliant with CORBA standards.
Core. In AIXwindows, Core is the top–level
superclass from which all widgets and gadgets are
derived. Core consists of three subclasses (Object,
RectObject, and WindowObj) that collectively
provide the appearance resources and behavioral
resources required by all widgets and gadgets in
the AIXwindows toolkit.
core sequence controller. One of three control
programs for the initial program load (IPL) ROM.
The core sequence controller accepts control from
the initial sequence controller and passes control to
the IPL controller.
core widget. In Enhanced X-Windows, the widget
that contains the definitions of fields common to all
widgets. All widgets are subclasses of the core
widget. See also widget.
corequisite. A product or update that must be
installed concurrently with another specified
product or update.
correlator. A value passed between two or more
programs that allows correlation or identification of
mutual resources.
counter. (1.) A register or storage location used to
accumulate the number of occurrences of an
event. (2.) In the X.25 API, a variable that is
increased by one when a packet arrives and is
decreased by one when a packet is received; it can
be used to notify the application program of
incoming packets.
counter identifier. In the X.25 API, the name of a
counter.
country code. In X.25 communications, the 3–digit
number that precedes the national terminal number
in the network user address (for public networks).
coupler. A device connecting a modem to a
telephone network.
courier. In DTS, a local server that requests a time
value from a randomly selected global server each
time it synchronizes.
CP. See control program.
CPS. Characters per second.
CPU. See central processing unit.
CPU lock. See nodelocked license.
CPU time. The amount of time a program is
running in the CPU or is being serviced by the
operating system. Does not include time
associated with the program’s I/O or time in which
other processes preempt the program’s use of the
CPU.
crash. An unexpected interruption of computer
service, usually due to a serious hardware or
software malfunction.
CRC. See cyclical redundancy check character.
Glossary
1-35
Create Action. In CDE, a software application that
enables you to associate an icon with a command
so that the command can be issued by clicking on
the icon. Create Action is also used to define
specific data types for an application’s data files
and to associate icons with those data types.
creation date. The date when the file was created.
See also session date and system date.
critical resource. The system resource whose
speed and/or size limits the speed with which a
particular workload can be processed.
critical sections. Portions of shared data to which
simultaneous access by multiple threads or
applications must be prevented.
cross–referencer. In Ada language, a tool that
provides a listing of all places where symbols are
declared, assigned to, or referenced within a
compilation unit. Symbols are identified by name,
class, and enclosing unit, and references to the
symbol are identified by source file line numbers.
CRQ. See call request.
CRT. See cathode ray tube.
CSC. See core sequence controller.
CSMA/CD. See carrier sense multiple access with
collision detection.
CSX. Host–based diagnostics program.
current character position. The two–dimensional
screen coordinates where the next character string
or pixel read/write operation will occur.
current color. The color that is employed to color
all subsequent drawing primitives. All drawing
primitives are drawn with this color until it is
changed.
current directory. The directory that is active and
can be displayed with the pwd command. Relative
path name resolution begins in the current
directory. Synonymous with current working
directory and working directory.
current file. (1.) The file being edited. If multiple
windows are in use, the current file is the file
containing the cursor. (2.) In the make command,
the file that the make command is working with at a
given moment. The make command replaces the
$* macro with the name of the current file.
current folder. In CDE, the currently opened folder
in an active File Manager view.
current graphics position. The homogeneous
three–dimensional point from which geometric
drawing commands draw. The current graphics
position is not necessarily visible.
current graphics window. In GL, the window to
which the system directs the output from graphics
routines.
CTC. Channel–to–channel.
current heap. In Pascal, the area of storage where
dynamic variables allocated by calls to NEW
reside. Other heaps can exist at the same time, but
only one is current.
CTS. Clear to send. Used with EIA–232 protocol.
current host. Synonym for local host.
CUD. See call user data.
current line. The line on which the cursor is
located.
C–stub. The part of the DUA that implements the
connection with the communications network.
CUG. See closed user group.
culling. (1.) In GL, if a primitive is smaller than the
minimum size specified in the command, it is
culled: no further commands in the primitive are
interpreted. See also clipping and pruning. (2.) In
the graPHIGS API, if a polygon is backfacing, it
may be culled, or not rendered.
currency time. The time at which a user reads
news items. The news command considers only
the items posted after this time to be current for the
user.
current. For an Ada–language compilation unit, the
state where none of that unit’s supporters has been
recompiled since the unit itself was compiled. This
implies that all of the supporters exist, since the
Ada language requires this in order for the program
to be compiled. Currency implies that all supporters
of a unit were compiled in the correct order, as
defined by Ada language rules.
1-36
Glossary
current record. (1.) The record pointed to by the
current line pointer. (2.) The record that is currently
available to the program.
current record pointer (CRP). A logical indicator
used when sequentially processing SFS files or
selected ranges of records from those files. The
CRP tracks which of the records in the selected
range has just been processed and which will be
processed next.
current selection. A highlighted text block or
element.
current session. In CDE, the session saved by
Session Manager when you log off. At the next
login, unless you specify otherwise, this session
automatically opens, enabling work to continue
where you left off. Contrast with home session.
current transformation matrix. The
transformation matrix on top of the matrix stack. All
points passed through the graphics pipeline are
multiplied by the current transformation matrix
before being passed on. The current
transformation matrix is a concatenation of the
current modeling and viewing matrices. See also
transformation and matrix stack.
current window. The window to which the system
directs the output from graphics routines. See also
window.
current working directory. Synonym for current
directory.
cursor. (1.) A movable symbol (such as an
underline) on a display that indicates to the user
where the next typed character will be placed or
where the next action will be directed. (2.) In
Enhanced X-Windows, the visible shape of the
pointer on a screen. A cursor consists of a hotspot,
a source bitmap, and a pair of colors. (3.) A
primitive such as an arrowhead that can be moved
about the screen by means of an input device
(typically a mouse).
cursor glyph. In GL, a 16x16 or 32x32 raster
pattern (bitmap that determines the shape of the
cursor. A GL cursor glyph can be one or two bits
deep; thus, a GL cursor can use up to three colors.
Color 0 is always transparent.
cursor ID. In Enhanced X-Windows, a unique
identification number that is associated with each
unique type of cursor.
cursor movement keys. The directional keys used
to move the cursor without altering text.
cursor stability. In file systems other than one
managed by SFS, the ability to simultaneously
maintain multiple contexts within a single file
system. The SFS equivalent of a cursor is provided
by the ability to simultaneously obtain multiple
OFDs on a single file.
Customer Information Control System (CICS). A
licensed program that enables transactions entered
at remote workstations to be processed
concurrently by user–written application programs.
It includes facilities for building, using, and
maintaining databases.
customization. (1.) In the NIM environment, this is
optional software installation. (2.) The process of
describing optional changes to defaults of a
software program that is already installed on the
system and configured so that it can be used.
Contrast with configuration. See also system
customization.
customization profile. A file containing the
descriptions of optional changes to the default
settings of a device or a software program. See
also profile.
customize. (1.) To describe to the system the
devices, programs, users, and user defaults for a
particular data processing system or network. (2.)
To describe optional preferences or changes to
defaults in a software program that is already
installed and configured. Contrast with configure.
Customized Database. An entity within the ODM
that contains configuration data for defined or
available devices in the system. See also Device
Configuration Database and Predefined Database.
Customized Devices Object Class. A
representation within the ODM of each device
instance as distinguished by a unique logical name.
The Customized Devices Object Class contains
basic information about the device such as device
status and how to access the information contained
in other object classes.
CUT. See control unit terminal mode.
cycle time. (1.) The time elapsed during one cycle
of the processor. Cycle time varies from one type of
processor to another. (2.) The minimum time
interval between starts of successive read/write
cycles of a storage device.
cyclic redundancy check (CRC) character. A
character code used in a modified cyclic code for
error sensing and correction.
cylinder. All fixed disk or diskette tracks that can
be read or written without moving the disk drive or
diskette drive read/write mechanism.
cylindrical coordinate system. An array where
the left edge of each row is functionally adjacent to
the right edge of the same row.
Cyrillic. Cyrillic alphabet. An alphabet used for
writing Old Church Slavonic and for Russian and
various other Slavic languages.
Glossary
1-37
D
establish, maintain, and end a connection, and the
signal conversion and coding between the data
terminal equipment (DTE) and the line.
DAC. See digital–to–analog converter.
data communications. See communications.
daemon. A program that runs unattended to
perform a standard service. Some daemons are
triggered automatically to perform their task; others
operate periodically. An example is the cron
daemon, which periodically performs the tasks
listed in the /var/spool/cron/crontabs directory.
Synonym for demon.
data consumer. In Performance Toolbox, a
description of a program that receives statistics
over the network from the xmservd daemon and
prints, post–processes, or otherwise manipulates
the raw statistics. Synonymous with client. Contrast
with data supplier.
daemon process. A process begun by the root
user or the root shell that can be stopped only by
the root user. Daemon processes generally provide
services that must be available at all times, such as
sending data to a printer.
data definition. A program statement that
describes the features of, specifies relationships of,
or establishes the context of, data. A data definition
can also provide an initial value. Definitions appear
outside a function or at the beginning of a block
statement.
DAF. Destination Address Field.
dangling else. A condition arising as a result of
nesting an IF statement in the IF part of an
IF–ELSE statement. The ELSE statement is
associated with the closest IF statement, in this
case, the inner one. Placing an empty ELSE
statement in the nested statement prevents
misinterpretation by forcing the outer ELSE
statement to associate with the outer IF statement.
DAS. Dual–attachment station. A station that
connects to both the primary and secondary FDDI
rings.
DASD. Direct access storage device. A device in
which access time is effectively independent of the
location of the data. Information is entered and
retrieved without reference to previously accessed
data. DASDs include both fixed and removable
storage devices.
data. A representation of facts or instructions in a
form suitable for communication, interpretation, or
processing by human or automatic means. Data
includes constants, variables, arrays, and character
strings.
data area. An area of memory that contains
specific control variables that are normally
predefined in structures or vectors.
data block. See block.
data cache. A cache for providing data to the
processor faster than it can be obtained from RAM.
data cache unit (DCU). See cache.
data circuit. A pair of associated transmit and
receive lines that provide a means of two–way data
communications.
data–circuit–terminating equipment (DCE). In a
data station, the equipment installed at the user’s
premises that provides all the functions required to
1-38
Glossary
data dependency. A situation in which a source
operand for a computation is the result of a
preceding computation.
data description. For data objects that are not
self–describing, components of the data object that
describe the data so that it may be processed.
Data Encryption Standard (DES). A data
encryption algorithm widely used in the United
States.
data item. A unit of data to be processed that
includes constants, variables, array elements, and
character substrings.
data link. (1.) The assembly of parts for two data
workstations that are controlled by a link protocol
and the interconnecting data circuit, which enables
data to be transferred from a data source to a data
sink. (2.) The interconnecting data circuit and the
link protocol between two or more workstations, not
including the data source or data sink. (3.) The
physical connection and the connection protocols
between units that exchange data over a
telecommunications line. See also X.25 link.
data link control layer. In SNA and X.25, the layer
that consists of the link stations that schedule data
transfer over a link between two nodes and
perform error control for the link.
data link control (DLC) protocol. In SNA, the set
of rules used by two nodes on a data link to
accomplish an orderly exchange of information.
data link escape (DLE) character. In BSC, a
transmission control character usually used in
transparent text mode to indicate that the next
character is a transmission control character.
data–link level. In the hierarchical structure of a
data station, the conceptual level of control or
processing logic between high level logic and the
data link that maintains control of the data link. The
data link level performs such functions as inserting
transmit bits and deleting receive bits; interpreting
address and control fields; generating, transmitting,
and interpreting commands and responses; and
computing and interpreting frame check
sequences. Synonym for frame level. See also
packet level, physical level.
data lock. (1.) The insurance of data availability to
a single application program as a protection
against conflicting updates to a data record. (2.)
The system lock that locks data segment into
memory.
data object. A collection of data referred to by a
single name. See also object.
data packet. In X.25 communications, a packet
used for the transmission of user data on a virtual
circuit at the DTE/DCE interface. See also packet.
data storage interrupt. An interrupt posted when
a fault is encountered accessing storage or I/O
space. A typical data storage interrupt is a page
fault or protection violation.
data stream. (1.) All information (data and control
information) transmitted over a data channel in a
single read or write operation. (2.) A continuous
stream of data elements being transmitted, or
intended for transmission, in character or
binary–digit form using a defined format. (3.) All
information sent to the terminal device driver with a
write subroutine. Synonymous with stream.
data supplier. In Performance Toolbox, a program
that supplies statistics across a network.
Synonymous with server. Contrast with data
consumer.
data terminal equipment (DTE). (1.) The part of
data processing unit that serves as a data source,
data sink, or both. (2.) The user of the network.
data terminal ready (DTR). A signal to the modem
used with EIA–232 protocol.
data token. In SOM, a value that identifies a
specific instance variable within an object whose
class inherits the instance variable (as a result of
being derived, directly or indirectly, from the class
that introduces the instance variable). An object
and a data token are passed to the SOM run–time
procedure, somDataResolve, which returns is a
pointer to the specific instance variable
corresponding to the data token. See also instance
token.
data transfer. The movement, or copying, of data
from one location and the storage of the data at
another location.
data type. (1.) In programming languages, a set of
values together with a set of permitted operations.
(2.) The mathematical properties and internal
representation of data and functions. (3.) An
attribute used for defining data as numeric or
character. (4.) The type, format, or classification of
a data object. (5.) In CDE, a mechanism that
associates particular data files with the appropriate
applications and actions. Data types can determine
the type of a file based on file–naming conventions,
such as a particular extension name, or on the
contents of the file. See also character type and
type.
database. A collection of facts and instructions
comprising at least one file that is sufficient for a
given purpose.
datagram. (1.) In packet switching, a
self–contained packet, independent of other
packets, that carries information sufficient for
routing from the originating data terminal
equipment (DTE) to the destination DTE without
relying on earlier exchanges between the DTEs
and the network. (2.) In DCE, an unreliable network
data packet that is independent of all other packets
and lacks any guarantees of delivery or
sequentiality.
datagram protocol. A connectionless,
datagram–based transport protocol, such as UDP;
an RPC protocol that runs over a connectionless
transport protocol.
dataless. A workstation without local file systems
or local boot images that accesses some of its
resources remotely. Dataless clients use a local
disk used for paging and dump devices.
dB. See decibel.
DB. Database.
DBA. See direct–bus attached.
DBCS. See Double–Byte Character Set.
D–bit. In X.25 communications, the bit in a data
packet or call–request packet that is set to 1 if
end–to–end acknowledgment (delivery
confirmation) is required from the recipient.
DC. See DCU.
DCD. Data carrier detect used with EIA–232
protocol. See also CD and decode.
DCE. See Distributed Computing Environment and
data–circuit–terminating equipment.
DCN. Distributed Computer Network.
DCU. Data cache unit. See also cache.
Glossary
1-39
DD. See device driver.
DDN. Department of Defense Network.
dead code elimination. A compiler optimization
that removes code that is never referenced, or that
is always branched over. A compiler optimization
that removes store instructions for data entities
whose final values are not used.
dead letter file. A file containing mail messages
that could not be sent to a proper destination file.
dead variable. In Ada language, a variable that is
initialized, but is not used within the context of the
program. Like unreachable code, dead variables
are detected and removed by the optimizer.
dead zone. An area of a tablet from which no input
reports are generated. Each virtual terminal can set
its own dead zones. Synonymous with no–input
zone.
deadlock. (1.) An error condition in which
processing cannot continue because each of two
elements of the process is waiting for an action by
or a response from the other. (2.) Unresolved
contention for the use of a resource. (3.) An
impasse that occurs when multiple processes are
waiting for the availability of a resource that does
not become available because it is being held by
another process that is in a similar wait state.
deallocate. To release a resource assigned to a
specific task. Contrast with allocate.
DEALLOCATE. A request to remove the allocation
of the specified conversation from the local
transaction program.
deallocation. An operation that removes a client’s
permission to use a resource.
debug. To detect, locate, and correct errors in the
configuration of a computer system or a software
program.
debugger. A program or programs used to detect,
trace, and eliminate errors in computer programs
or software.
debugging. Acting to detect and correct errors in
software or system configuration.
debugging mode. A special mode in which a
program provides detailed output about its activities
to aid a user in detecting and correcting errors in
the program itself or in the configuration of the
program or system.
decibel (dB). (1.) One tenth of a bel. (2.) A unit of
signal strength, such as the signal on a data
communications channel. (3.) A unit for measuring
relative power. The number of decibels is 10 times
the logarithm (base 10) of the ratio of the
measured power levels.
1-40
Glossary
decimal. (1.) Pertaining to a system of numbers to
the base 10. The decimal digits range from 0
through 9. (2.) Characterized by a selection,
choice, or condition that has 10 possible different
values or states.
decimal constant. A number containing any digits
0 through 9.
declaration. (1.) A description that makes a
defined object available to a function or a block.
(2.) In programming languages, the mechanism for
establishing a language object. A declaration
normally involves attaching an identifier and
allocating attributes to the language object
concerned. (3.) In a programming language, a
meaningful expression that affects the
interpretation of other expressions in that
language. (4.) In Ada language, a declaration
associates an identifier (or some other notation)
with an entity. This association is in effect within a
region of text called the scope of the declaration.
Within the scope of a declaration, there are places
where it is possible to use the identifier to refer to
the associated declared entity. At such places the
identifier is said to be a simple name of the entity;
the name is said to denote the associated entity.
See also declare, simple name, scope, and name.
declarative part. In Ada language, a sequence of
declarations. It may also contain related
information such as subprogram bodies and
representation clauses.
declarator. An identifier and optional symbols that
describe the data type.
declare. A selection available from the Interpreter’s
Interpret menu that allows a user to assign variable
names and structure definitions. See also
declaration.
decode. (1.) To convert data by reversing the effect
of some previous encoding. (2.) To interpret a
code. See also DCD.
default. A value, attribute, or option that is
assumed when no alternative is specified by the
user. See also default value.
default accelerators. See accelerator.
default arguments. Arguments that are declared
with default values in a C++ function prototype or
declaration. If a call to the function omits these
arguments, default values are used. Arguments
with default values must be the trailing arguments
in a function prototype argument list.
default button labels. In AIXwindows, XmLabel
widgets or gadgets that are used when no other
button label has been specified.
default cell (global access). An NCS cell that
allows access from any node in the network. This is
the most common cell used in License Use
Management configurations because it allows all
other License Use Management servers in the
default cell to communicate freely.
default clause. In a C switch statement, the
keyword default followed by a colon and one or
more C statements. When the conditions of the
specified case labels in the switch statement do not
hold, the default clause is chosen.
default constructor. A C++ constructor that takes
no arguments, or if it takes any arguments, all its
arguments have default values.
default device. The device attached to your
computer (such as a printer or disk drive) that is
used when no alternative is specified by the
operator.
default directory. The directory name supplied by
the operating system if none is specified.
default drive. The drive name supplied by the
operating system if none is specified.
default files. Data files in which resource default
values are stored in ASCII form to permit the
assignment of alternative resource values at run
time without need for rewriting or recompiling
source code.
default initialization. The initial value assigned to
a data object by the compiler if no initial value is
specified by the programmer. In C language,
external and static variables receive a default
initialization of zero, while the default initialization
for auto and register variables is undefined. See
also default value.
default label. See label.
default printer. A printer that accepts all the
printed output from a display station assigned to it.
default shell. In AIXwindows, the shell that is used
when no other shell properties have been
specified.
default value. A value stored in the system that is
used when no other value is specified. See also
default and default initialization.
defaults file. See default files.
define. Creates an entry in the ODM Customized
Devices Database and establishes the parent
device and connection location.
define method. Used to create a device instance
in the ODM Customized Database. It takes a
device from the undefined or nonexistent state to
the defined state.
define statement. A preprocessor statement that
causes the preprocessor to replace an identifier or
macro call with specified code.
defined state. The state a device is put into when
its defined method is run or when an available
device’s unconfigure method is run. The device is
not a usable device at this point.
DEL. See delete character.
delayed port. A port that is enabled like a shared
port except that the login herald is not displayed
until you type one or more characters (usually
carriage returns). A port directly connected to a
remote system or intelligent modem is usually
enabled as a delayed port.
delete. (1.) To remove. For example, to delete a
file. See also erase. (2.) The C++ keyword delete
identifies a free store deallocation operator. In C++,
the delete operator is used to destroy objects
created by new.
delete character (DEL). (1.) A control character
used primarily to obliterate an erroneous or
unwanted character. (2.) A character that identifies
a record to be removed from a file.
delimiter. (1.) A character or sequence of
characters that marks the beginning or end of
character string or unit of data. (2.) A character that
groups or separates words or values in a line of
input.
deliver (callback). Delivering a callback or upcall
means to cause its invocation.
delivery–confirmation bit. See D–bit.
delta. The finite increment of a variable.
demangling. The conversion of mangled C++
names back to their original source code names.
During compilation, identifiers such as function and
static class member names are mangled (encoded)
with type and scoping information to ensure
type–safe linkage. These mangled names appear
in the object file and the final executable file.
Demangling converts these names back to their
original names to make program debugging easier.
demon. Synonym for daemon.
denote. See declaration.
density. In printing, refers to the number of
characters per inch horizontally.
dependency line. The first line of an entry in a
description file. It contains a list of target files
followed by a colon and an optional list of
prerequisite files or dependencies.
Glossary
1-41
dependent. A software product that requires
another product or update to be installed before or
at the same time it is installed. Contrast with
prerequisite.
dependent workstation. A workstation having
little or no stand–alone capability that must be
connected to a host or server in order to provide
any meaningful capability to the user.
dependents. Ada–language compilation units that
would have to be recompiled if another unit were to
be recompiled because of the compilation order
imposed by the Ada language.
depth. (1.) In Enhanced X-Windows, the number of
bits per pixel for a window or pixmap. (2.) In a
three–dimensional context, the second dimension.
depth–cueing. In 3D computer graphics, varying
the intensity of a line with depth. Typically, the
points on the line further from the eye are darker,
so the line seems to fade into the distance.
dequeue. To remove items from a queue. Contrast
with enqueue.
dereferenced pointer. In Pascal, an expression
using the –> or @ operator used to locate a
dynamic variable from a pointer.
derivation. The process of deriving a C++ class
from an existing class, called a base class.
derived class. A C++ class that inherits the
properties of a base class. You can add additional
data members and member functions to the
derived class. A derived class object can be
manipulated as if it were a base class object. The
derived class can override virtual functions of the
base class.
derived metaclass. (Or SOM–derived metaclass.)
A metaclass that SOM creates automatically (often
even when the class implementor specifies an
explicit metaclass) as needed to ensure that, for
any code that executes without method–resolution
error on an instance of a given class, the code will
similarly execute without method–resolution error
on instances of any subclass of the given class.
SOM’s ability to derive such metaclasses is a
fundamental necessity in order to ensure binary
compatibility for client programs despite any
subsequent changes in class implementations.
derived type. In Ada language, a type whose
operations and values are replicas of those of an
existing type. The existing type is called the parent
type of the derived type. See also parent type.
DES. See Data Encryption Standard.
descendant. See child.
1-42
Glossary
descending key sequence. The arrangement of
data in order from the highest value of the key field
to the lowest value of the key field.
descriptor. (1.) In ODM, a named and typed
variable that defines a single characteristic of an
object. See also terminal descriptor, link descriptor,
and method descriptor. (2.) In information retrieval,
a parameter word used to categorize or index
information. (3.) In XOM, the means by which the
client and service exchange an attribute value and
the integers that denote its representation, type,
and syntax. (4.) In XDS, a defined data structure
that is used to represent an OM attribute type and
a single value. (5.) In SOM, an ID representing the
identifier of a method definition or an attribute
definition in the Interface Repository. The IR
definition contains information about the method’s
return type and the type of its arguments.
deselect. To cancel the selection of a button. With
a mouse, you deselect a highlighted area with the
Select (left) button. Otherwise, you can use the
Select key on the keyboard. To deselect a default
button, select an alternate button in the selection
list.
deserialize. (1.) To change from serial–by–bit to
parallel–by–byte. (2.) In XDR, to change from XDR
format to a particular machine representation.
desktop. A visual representation of a group of
objects in your system, brought together to help
you organize your work.
destination cursor. A point or location marked by
the cursor to which data is to be pasted or inserted.
destination disk. The disk to which you are
installing.
destructor. A special member function of a class
with the same name as the class with a ~ (tilde)
preceding the name. You cannot specify arguments
or a return type for this function. A destructor
”cleans up” after an object by doing such things as
freeing any storage that was dynamically allocated
when the object was created.
device. (1.) A mechanical, electrical, or electronic
machine that is designed for a specific purpose and
that attaches to your computer, such as a printer,
plotter, or disk drive. (2.) A valuator, button, or the
keyboard. Buttons have values of 0 or 1 (up or
down); valuators (mouse, dials) return values in a
range, and the keyboard returns ASCII values.
device class. Functional grouping of devices. The
generic name for a group of device types, for
example, all display stations belong to the same
device class. Contrast with device type.
Device Configuration Database. Stores all
information relevant to support the device
configuration process. It consists of a Predefined
Database and a Customized Database. See also
Predefined Database and Customized Database.
device subclass. Distinguishes devices within the
same functional class. It is used to indicate
different interfaces. For example, the printer class
has three subclasses: rs232, rs422, and parallel.
device definition. Information about a device that
is in the Customized Database including attributes
and connection locations.
device switch table. (1) A table that is used as an
interface to the device drivers. (2) A table that
contains a pointer to the entry points for each
device head.
device description. Text used to give a short
description of the device. For example, the device
description for the token–ring adapter might be
”Token–Ring High–Performance Adapter.”
device type. The general name for a kind of
device sharing the same model number; for
example, 2311, 2400, 2400–1. Contrast with device
class.
device driver (DD). (1.) A program that operates a
specific device, such as a printer, disk drive, or
display. (2.) A collection of subroutines that control
the interface between I/O device adapters and the
processor.
DFT. See distributed function terminal.
device handler. The component of a device driver
that communicates directly with the hardware.
Synonymous with virtual device driver.
device head. The component of a device driver
that implements the application program interface
to a device.
device instance. When a device is defined, a
Customized Devices Object Class entry is created.
This entry is considered a device instance. There is
a device instance for each device defined in the
system.
device location. Indicates the location path of a
device. This is a field in the Customized Devices
Object Class.
device manager. For complex interfaces, a
collection of routines that acts as an intermediary
between drivers and virtual machines. For
example, supervisor calls from a virtual machine
are examined by a device manager and routed to
the appropriate subordinate device drivers.
device name. (1) The logical or symbolic name
reserved by the system to refer to a specific device.
(2) SNA uses the operating–system device name
of the network adapter to get information that
defines the interface. See also logical name.
device number. The reference number assigned
to any external device.
DHCP. Dynamic Host Configuration Protocol. An
application–layer protocol that allows a machine on
the network, the client, to get an IP address and
other configuration parameters from the server.
diacritic. A diacritic is a mark added to a letter to
indicate a special phonetic value. Diacritics are
implemented by a nonspacing character sequence,
a two–key sequence consisting of one of 13
diacritics followed by an alphabetic character or a
space. The terminal device driver converts this
two–key sequence into a single code point.
diagnostic. Pertaining to the detection and
isolation of errors in programs and faults in
equipment.
diagnostic aid. A tool (procedure, program, or
reference manual) used to detect and isolate a
device or program malfunction or error.
diagnostic code. In X.25 communications, a
1–byte code included in clear– and reset–indication
packets that gives information about the reason for
sending the packet. See also cause code.
Diagnostic Control Program. The top–level
control program and configuration manager for
diagnostics. It traverses the configuration
database, testing resources and their
interdependencies. It analyzes conclusions from
diagnostic applications and generates a problem
report.
diagnostic output. Error or status messages
produced by processes, in addition to those
messages produced by standard output.
Synonymous with error output.
device stanza. Defines a device attached to a
queue in the print spooling system. A device stanza
contains all information pertaining to the device
(usually a printer) and is found in the /etc/qconfig
file.
dial. (1) A computer input device that allows a user
to set parameter values. Dials are a type of
valuator. See also valuator.(2) An I/O device used
to input variables by way of thumbwheels.
device state. Indicates the current configuration
status of a device instance. Possible values are
defined, available, and stopped. This is a field in
the Customized Devices Object Class.
dial and switch box. An I/O device with 8 dials
(valuators) and 32 switches. The switch box is also
called a ”button box” or the ”lighted programmable
function keys (LPFKs).”
Glossary
1-43
dial–code. In BNU, a code representing a
telephone number or portion of a telephone
number.
direct–bus attached. Used in relation to the fixed
disk drives attached directly to the system board
rather then through a SCSI adapter card.
dialing directory. In ATE, a list of telephone
numbers that can be called with Asynchronous
Terminal Emulation (ATE). It is similar to a page in
a telephone directory.
direct color. (1.) In Enhanced X-Windows, a class
of color map in which a pixel value is decomposed
into three separate subfields for indexing. One
subfield indexes an array to produce red intensity
values, the second indexes another array for blue
intensity values, and the third for green intensity
values. The RGB values can be changed
dynamically. This is mutually exclusive to the
Pseudocolor color map color. (2.) Also DirectColor,
a value.
dialog. In an interactive system, a series of related
inquiries and responses similar to a conversation
between two people.
Dialog. In AIXwindows, a two–way text interface
between an application and its user. The interface
takes the form of a collection of widgets and
gadgets, including a DialogShell widget, a
BulletinBoard widget (or a subclass of a
BulletinBoard widget or some other container
widget), plus various children, including Label,
PushButton, and Text widgets.
dialog box. A window that is displayed when
further information is needed from the user, or
when the system needs to display information. A
line enclosure on a structure, such as a widget or
shell, that contains a specific, two–way text
interface.
dialog shell. A subclass of transient shell, this
shell is used for dialog boxes. See also dialog
widget.
dialog widget. Any of a class of widgets chosen
through the Create menu’s Dialog submenu; dialog
widgets always have the dialog shell as their
implicit shell. See also dialog shell.
digest. Data that has been organized into a format
that provides for quick access to each piece of
data.
digit. (1) A character that represents a
nonnegative integer. Synonymous with numeric
character. (2) A symbol that represents one of the
nonnegative integers smaller than the radix. (3)
Any of the numerals from 0 through 9.
digital–to–analog converter (DAC). (1) A highly
specialized chip that converts the digital values
coming out of the frame buffer into the rapidly
varying analog voltage levels that are required by
the monitor. (2) That portion of the display
subsystem that converts pixels into colors or
grayscale.
dimension. The attribute of size given to arrays
and tables.
direct addressing. (1) An addressing method that
uses an expression as an operand entry to
represent an instruction address. (2) A method of
addressing in which the address part of an
instruction contains a direct address.
1-44
Glossary
direct connection. The attachment of a system,
workstation, or other I/O device through a selected
communication interface and a limited–length
cable. No modem is required.
direct–mapped cache. A cache in which exactly
one line corresponds to each possible value of the
virtual–address field that identifies the line to be
interrogated.
direct memory access (DMA). (1.) The transfer of
data between memory and an input/output device
without processor intervention. (2.) General term
given to the system facility that allows a device on
the Micro Channel bus to get direct access to the
system or bus memory without the intervention of
the system processor. The system–supplied
resource that provides this facility and mediates the
data transfers between the memory and devices is
the DMA controller.
direct visibility. See visibility.
directional component. In AIXwindows, a portion
of a compound string that specifies a direction with
a given value. The directional component is
created with the XmStringDirectionCreate
function.
directive. In SOM, a message (a pre–defined
character constant) received by a replica from the
Replication Framework. Indicates a potential failure
situation.
directory. (1.) A type of file containing the names
and controlling information for other files or other
directories. (2.) A table of identifiers and references
to the corresponding items of data. (3.) An index
used by a control program to locate blocks of data
that are stored in separate areas of a data set in
direct access storage. (4.) Contrast with special
file. (5.) A listing of related files arranged in a useful
hierarchy. (6.) In CDS, a logical unit for storing
entries under one name (the directory name) in a
CDS namespace. In addition to object entries, a
directory can contain soft links and child pointers.
You can copy, delete, and control access to a
directory. Each physical instance of a directory is
called a replica. (7.) In XDS, a collection of open
systems that cooperate to hold a logical database
of information about a set of objects in the real
world. (8.) In CDE, a collection of files and other
subdirectories. In graphical user interface
applications, may be called a folder.
directory ID. See directory identifier.
directory identifier (directory ID). An identifier for
distinguishing several configurations of the
directory service within an installation.
directory mask. A pattern of characters that
controls which portions of a directory will be
retained and which portions will not be retained.
dirty object. In SOM, a persistent object that has
been modified since it was last written to persistent
storage.
disable. (1.) To make nonfunctional. In interactive
communications, to disconnect or stop a
subsystem. Contrast with enable. (2.) To bring a
queue or a device attached to a queue off line so
that no print jobs get sent to it.
disabled port. In Asynchronous Terminal
Emulation (ATE), a port configuration indicating
that a port is ready to call out.
DISC. Disconnect.
discipline. Ordering method used to line up jobs
for printing, FCFS (first–come–first–served) or SJN
(shortest–job–next). See also
first–come–first–served and shortest–job–next.
disconnect. In X.25 communications, to
disconnect a port from the X.25 network.
disconnected mode (DM). In SDLC, a response
from a secondary station indicating that it is
disconnected and wants to be online.
discrete type. In Ada language, a type that has an
ordered set of distinct values. The discrete types
are the enumeration and integer types. Discrete
types are used for indexing and iteration, and for
choices in case statements and record variants.
discretionary access control. A security
mechanism that protects information from
unauthorized disclosure or modification through
owner–controlled access to files. See also access
control list, base permission, and extended
permission.
discriminant. In Ada language, a distinguished
component of an object or value of a record type.
The subtypes of other components, or even their
presence or absence, may depend on the value of
the discriminant.
discriminant constraint. In Ada language, on a
record type or private type, specifies a value for
each discriminant of the type.
discriminated union. In XDR, a C language union
that holds several data types, with one arm of the
union being an enumeration value, or discriminant,
which holds a specific object to be processed over
the system first.
disk. A storage device made of one or more flat,
circular plates with magnetic surfaces on which
information can be stored.
disk adapter. The hardware used by a computer to
access and control disk drives. On POWERstations
and POWERservers, disk adapters each fit into a
single Micro Channel slot, and each are controlled
by software device drivers.
disk drive. The mechanism used to read and write
information on a disk.
disk I/O. Fixed–disk input and output.
Disk Operating System. See DOS.
disk–usage accounting. The record of the
number of disk blocks occupied by a user’s files.
Disk–usage accounting is performed by the
acctdisk command.
diskette. A thin, flexible magnetic plate that is
permanently sealed in a protective cover. It can be
used to store information copies from the disk or
another diskette.
diskette drive. The mechanism used to read and
write information on diskettes.
diskless. A workstation without local file systems
or local boot images that accesses some of its
resources remotely. Diskless clients boot remotely
from a diskless server and use the server for
remote paging.
Diskless Workstation Manager (DWM).
Operating–system software that initializes and
maintains resources for diskless clients and
diskless servers. It is a group of commands, awk
command scripts, and source code.
dispatch. To allocate processing time on a specific
device for a job that is ready to run.
dispatch–function resolution. Dispatch–function
resolution is the slowest, but most flexible, of the
three method–resolution techniques SOM offers.
Dispatch functions permit method resolution to be
based on arbitrary rules associated with an object’s
class. Thus, a class implementor has complete
freedom in determining how methods invoked on
Glossary
1-45
its instances are resolved. See also dispatch
method and dynamic dispatching.
operation during interaction with a host computer
that emulates a 3278/79 terminal display.
dispatch method. In SOM, a method (such as
somDispatch or somClassDispatch) that is invoked
(and passed an argument list and the ID of another
method) in order to determine the appropriate
method procedure to execute. The use of dispatch
methods facilitates dispatch–function resolution in
SOM applications and enables method invocation
on remote objects in DSOM applications. See also
Dynamic Invocation Interface, dynamic dispatching,
and dispatch–function resolution.
display station. An input/output device that
includes a keyboard from which an operator can
send information to the system and a display
screen on which an operator can see also the
information sent to or received from the computer.
dispatcher. In XOM, the software that implements
the service interface functions using workspace
interface functions.
displacement. (1.) A positive or negative number
that can be added to the contents of a base
register to calculate an effective address. (2.) The
distance from the beginning of a record, block, or
segment to the beginning of a field.
display. (1.) A visual presentation of data. (2.) To
present data visually. (3.) A computer output
screen on which visual information is displayed.
(4.) In Enhanced X-Windows, a set of one or more
screens and input devices that are driven by a
single X Server. Synonym for monitor.
display attribute. In XGSL, the following are some
of the attributes associated with displays: (1.) APA
(all points addressable) or character. An APA
display can address each pixel, while a character
display addresses character–sized blocks of pixels,
(2.) blink supported or not supported, (3.) color or
monochrome, and (4.) changeable color palette or
fixed color palette.
display device. See display.
display list (object). In GL, also called an object.
It is a sequence of drawing commands that have
been compiled into a unit. Conceptually, a display
list is like a macro: it can be invoked multiple times
simply by referring to its name. The object can be
instantiated at different locations, sizes, and
orientations by appropriate use of the
transformation matrices. For instance, series of
polygons arranged in the shape of a bolt can be
compiled into an object. The bolt can then be
drawn multiple times by invoking its display list.
display symbol. A predefined printable graphics
symbol (such as, characters, numbers, math
symbols, Greek letters, and so on) that can be
displayed on a graphics display.
display symbol set. A set of display symbols
placed in a table. There are up to 1024 display
symbols. Display symbols 0 through 31 represent
control functions and have no graphic
representation.
distinguished encoding. The restrictions to the
Basic Encoding Rules designed to ensure a unique
encoding of each ASN.1 value, defined in the
X.500 Directory Standards (CCITT X.509).
distortion. In data communications, an
undesirable change in a wave form that can occur
between two points in a transmission system. The
six major forms of distortion are bias, characteristic,
delay, end, fortuitous, and harmonic.
distributed. The programs and computerized
sources of information that make up a computing
environment can be physically located on different
computer systems, while still working together as a
single logical unit. Transaction processing systems
are easily moved to a distributed computing
environment, because these systems traditionally
involve modifying a centralized source of
information by submitting modification or
information requests from remote terminals.
Distributed Computing Environment (DCE). A
computing environment in which the resources and
data may be located on different processors.
distributed file system. A file system composed
of files or directories that physically reside on more
than one computer in a communications network.
distributed free space. Synonym for free space.
Display PostScript (DPS). Extension to X server
created by Adobe.
Distributed Function Terminal (DFT). A
workstation that performs operations previously
accomplished by the processing unit, such as
managing data links, controlling devices, and
formatting data.
display screen. The part of the display device that
displays information visually. Synonymous with
terminal screen. See also screen.
distributed transaction. A transaction which can
update data in many user processes on many
machines.
display session. A 3270 Host Connection
Program 2.1 and 1.3.2 for AIX (HCON) mode of
distribution medium. The medium on which the
operating system software, a licensed program, or
1-46
Glossary
an application program is distributed to the user.
The distribution medium can be any of several
different media supported by the hardware, such as
streaming cartridge tape, 9–track tape, or 3.5–inch
diskette.
dithering. In computer graphics, a technique of
interleaving dark and light pixels so that the
resulting image looks smoothly shaded when
viewed from a distance.
diversion. In text formatting, a command used to
save text for printing later in a document, such as
for footnotes.
DIX connector. A device that connects an Ethernet
network adapter to a standard (”thick”) Ethernet
local area network (LAN). Its name is derived from
the names of the principal developers of Ethernet
(Digital Equipment Corporation, Intel, and Xerox).
DLC. See data link control protocol.
DLE. See data link escape character.
DLPI. Data Link Provider Interface.
DLS. Data link service.
DLS provider. In X.25 communications, the data
link layer protocol that provides the services of the
Data Link Provider Interface (DLPI).
DLS user. In X.25 communications, the user–level
application or user–level or kernel–level protocol
that accesses the services of the data link layer.
DLSAP (data–link–service access point). In X.25
communications, a point at which a data link
service (DLS) user attaches itself to a DLS provider
to access data link services.
DLSAP address. In X.25 communications, an
identifier used to differentiate and locate specific
DLS user access points to a DLS provider.
DM. See disconnected mode.
DMA. See direct memory access.
DMA slave. A device on the Micro Channel bus
that uses the system–provided DMA facilities
instead of having a built–in controller. See also Bus
Master.
DO loop. In FORTRAN, a range of statements
called repetitively by a DO statement.
do statement. (1.) In C language, a looping
statement that contains the keyword do followed by
a statement (the action), the keyword while, and
an expression in parentheses (the condition). (2.) A
statement used to group a number of statements in
a procedure.
DO variable. In FORTRAN, a variable, specified in
a DO statement, that is incremented or
decremented on each iteration of the relative DO
loop and controls the number of iterations of the
loop.
domain. (1.) That part of a network in which the
data processing resources are under common
control. (2.) In a database, all the possible values
of an attribute or a data element. (3.) In TCP/IP, the
naming system used in hierarchical networks. The
domain naming system uses the DOMAIN protocol
and the named daemon. In a domain system,
groups of hosts are administered separately within
a tree–structured hierarchy of domains and
subdomains.
domain name. A level in the hierarchy of names
used throughout the Internet.
DOS (Disk Operating System). A disk operating
system used on personal computers.
dot. A symbol (.) that indicates the current
directory in a relative path name.
dot dot. A symbol (..) in a relative path name that
indicates the parent directory.
dot matrix. A printer with wires or other means that
uses a matrix of dots for printing characters.
dotted decimal. A common notation for Internet
host addresses that divides the 32–bit address into
four 8–bit fields. The value of each field is specified
as a decimal number and the fields are separated
by periods (for example, 010.002.000.052 or
10.2.0.52).
double buffer mode. In GL, a mode in which two
buffers are alternately displayed and updated. A
new image can be drawn into the back buffer while
the front buffer (containing the previous image) is
displayed. See also single buffer mode.
Double–Byte Character Set (DBCS). A set of
characters in which each character is represented
in 2 bytes of storage. Languages such as
Japanese, Chinese, and Korean, which contain
more symbols than can be expressed in a single
byte, are represented in this character set.
double–click. To click twice in rapid succession
without moving the mouse pointer.
double precision. (1.) Pertaining to the use of two
computer words to represent a number in
accordance with the required precision. (2.) A
specification that causes a floating–point value to
be stored internally in the long format. See also
precision.
double–strike. A process of printing a character
twice to create the appearance of bold type, used
frequently with impact printers. A more flexible form
Glossary
1-47
of double–strike is emphasized printing. See also
boldface and emphasized.
double–wide print. A print format in which
characters are twice as wide as they normally are.
download. To transfer data from one computer for
use on another one. Typically, users download from
a larger computer to a diskette or fixed disk on a
smaller computer or from a system unit to an
adapter.
downstream. The direction from stream head to
driver.
downward jump. For the bfs command, the act of
moving from the current location in a file toward the
bottom or end of the file.
DPS. See Display PostScript.
DR1I. Definite response 1 indicator.
DR2I. Definite response 2 indicator.
drag. To point to an object with the mouse pointer,
hold down the mouse button, move the mouse, and
then release the mouse button. A method of
”dragging” an object to a desired point.
DRAM. See dynamic random access memory.
drawable. In Enhanced X-Windows, a collective
term for both windows and pixmaps when used as
destinations in graphics operations. However, an
InputOnly window cannot be used as a source or
destination drawable in a graphics operation.
drawn button. In AIXwindows, a graphic object
that simulates a real–world button with a symbol or
other image drawn on its face.
driver. The end of a stream closest to an external
interface. The principal functions of the driver are
handling any associated device and transforming
data and information between the external device
and stream. It can also be a pseudo–driver, not
directly associated with a device, which performs
functions internal to a stream, such as a multiplexer
or log driver.
driving table. A table that describes all the
printer–specific information for the nroff command.
drop. In CDE, after starting the drag of an object,
the act of releasing the mouse button. If the object
is dropped in an appropriate area, an action is
initiated.
drop–in. Some applications can detect that an icon
has been dropped on to their window to perform an
appropriate action, such as opening a document.
drop target. In CDE, a rectangular graphic that
represents the drop zone in an application.
1-48
Glossary
drop zone. In CDE, an area of the workspace,
including the Trash Can, Print Manager, and Mailer
Front Panel controls, that accepts a dropped icon.
Icons can be dropped on the workspace for quick
access.
dropped folio. A page numbering style in which
the page number is printed at the foot of the page.
See also folio, blind folio, and expressed folio.
dropping locks. Releasing the locks that a
transaction holds on data.
DSI. See data storage interrupt.
DSR. Data set ready; used with EIA–232 protocol.
See your modem manual for more information.
DTE. See data terminal equipment.
DTR. See data terminal ready.
dummy argument. In FORTRAN, a variable within
a subprogram or statement function definition with
which actual arguments from the calling program or
function reference are positionally associated. See
also formal parameter.
dump. (1.) To copy the contents of all or part of
storage onto another data medium or to an output
device. (2.) Data that has been dumped.
dump data. The data collected by the kernel dump
program. It is obtained from memory locations
used by kernel components.
dump table entry. A record in the master dump
table that identifies the location of a component
dump table. All kernel components that need to
have special data collected by the dump program
need to generate a dump table entry.
duplex. Pertains to communications data that can
be sent and received at the same time.
Synonymous with full duplex and FDX. Contrast
with half duplex.
duplex connector. In a fiber channel link
environment, the component that terminates both
jumper cable fibers in one housing and provides
physical keying for attachment to a duplex
receptacle.
duplexed output. Output that uses both the front
and back of each sheet of paper for printing.
DWM. See Diskless Workstation Manager.
dyadic operator. Synonym for binary operator.
dynamic. A style of creating pop–up menus.
dynamic block header. A data structure used by a
compiler to link dynamic variables that are in the
same heap.
dynamic connection. A connection that is
established when needed rather than being
predetermined or fixed.
dynamic dispatching. In SOM, method
dispatching using dispatch–function resolution; the
use of dynamic method resolution at run time. See
also dispatch method, dispatch–function resolution,
and dynamic method.
Dynamic Invocation Interface (DII). In SOM, the
CORBA–specified interface, implemented in
DSOM, that is used to dynamically build requests
on remote objects. Note that DSOM applications
can also use the somDispatch method for dynamic
method calls when the object is remote. See also
dispatch method.
dynamic license. A license that specifies multiple
nodelocked licenses. The license is installed at a
license server, and then the license server derives
license passwords (each of which specifies a single
nodelocked license) from the dynamic license. The
server automatically installs the individual licenses
at the user nodes from which the licensed product
is invoked.
dynamic linking. Linking of a program in which
library procedures are not incorporated into the
load module but are dynamically loaded from their
library each time the program is loaded.
dynamic method. A SOM method that is not
declared in the IDL interface statement for a class
of objects, but is added to the interface at run time,
after which instances of the class (or of its
subclasses) will respond to the registered dynamic
method. Because dynamic methods are not
declared, usage bindings for SOM classes cannot
support their use; thus, offset method resolution is
not available. Instead, name–lookup or
dispatch–function method resolution must be used
to invoke dynamic methods. (There are currently
no known uses of dynamic methods by any SOM
applications.) See also dynamic dispatching,
method, and static method.
dynamic random access memory. A storage in
which the cells require repetitive application of
control signals to retain stored data. Such repetitive
application of the control signals is normally called
a refresh operation.
dynamic routing. A method of setting paths
between hosts, networks, or both by using
daemons that update the routing table as needed.
dynamic string. See string.
dynamic variable. A variable allocated only when
needed. Explicit allocations and deallocations are
required. In Pascal, the predefined procedures
NEW and DISPOSE are provided for this purpose.
dynamic window. A variable that can change
dynamically within a certain window or range of
values.
Glossary
1-49
original login ID. All discretionary access decisions
are based on the effective user ID.
E
Easy Install. An application used to install optional
software or service updates in the form of software
bundles.
EBCDIC. See extended binary–coded decimal
interchange code.
EBCDIC character. Any one of the symbols
included in the 8–bit EBCDIC set.
EC. Engineering Change level.
ECB. (1.) See event control bit. (2.) Event control
block. (3.) Electronic codebook.
ECC. (1.) See error–checking and correction. (2.)
Error correction code.
echo. (1.) A reflected signal on a communications
channel. On a communications terminal, each
signal is displayed twice, once when entered at the
local terminal and again when returned over the
communications link. This allows the signals to be
checked for accuracy. (2.) In computer graphics,
the immediate notification of the current values
provided by an input device to the operator at the
display console. (3.) In word processing, to print or
display each character or line as it is typed in.
ECM. Entity coordination management.
ECMA. European Computer Manufacturers’
Association.
edit. (1.) To add, change, delete, rearrange, or
modify the form or format of data. (2.) To check the
accuracy of information and to indicate if an error is
found.
edit buffer. A temporary storage area used by an
editor.
effective rate. The average sustained speed at
which a device operates under real–world
conditions, when processing a representative
workload.
effective root directory. The point where a system
starts when searching for a file. Its path name
begins with a / (slash). The chroot subroutine
causes the directory named by the path parameter
to become the effective root directory.
effective user ID. (1.) The user ID associated with
the last authenticated user or the last setuid
program. Equal to either the real or the saved user
ID. (2.) The current user ID, but not necessarily the
user’s login ID. For example, a user logged in
under a login ID may change to another user’s ID.
The ID to which the user changes becomes the
effective user ID until the user switches back to the
1-50
Glossary
EGA. The Enhanced Graphics Adapter.
EGP. Exterior Gateway Protocol. The mechanism
that allows the exterior gateway of an autonomous
system to share routing information with exterior
gateways on other autonomous systems.
EIA. Electronic Industries Association.
EIA–232D. An EIA interface standard that defines
the physical, electronic, and functional
characteristics of an interface line that connects a
communication device and associated workstation.
It uses a 25–pin connector and an unbalanced line
voltage.
EIA–422A. An EIA interface standard that defines
the physical, electronic, and functional
characteristics of an interface line connecting a
computer to communications equipment. It uses a
balanced line voltage for noise reduction and
longer distance capability. The system unit uses
the send and receive pins from the set of 40 pins
defined by the EIA–422A interface.
elaborated type specifier. Typically used in C++
in an incomplete class declaration or to qualify
types that are otherwise hidden.
elaboration. In Ada language, the elaboration of a
declaration is the process by which the declaration
achieves its effect (such as creating an object); this
process occurs during program execution.
electromagnetic compatibility. The design and
test of products to meet legal and corporate
specifications dealing with the emissions and
susceptibility to frequencies in the radio spectrum.
Electromagnetic compatibility is the ability of
various electronic equipment to operate properly in
the intended electromagnetic environment.
electronic mail. Synonym for mail.
element. (1.) The smallest unit of data in a table or
array. (2.) In a set, an object, entity, or concept
having the properties that define a set.
Synonymous with member. (3.) In SNA, the
particular resource within a subarea that is
identified by an element address. (4.) The
component of an array, subrange, enumeration, or
set. (5.) In AIXwindows, an object or similar data
structure having the properties that define a class.
else clause. The part of an if statement that
contains the keyword else followed by a statement.
The else clause provides an action that is started
when the if condition evaluates to a value of 0
(false).
em. In a specific type size, an em is the same
number of points as there are to that specific size.
See also en.
embedded blanks. Blanks that are surrounded by
any other characters.
EMC. See electromagnetic compatibility.
emitter. In SOM, generically, a program that takes
the output from one system and converts the
information into a different form. Using the Emitter
Framework, selected output from the SOM
Compiler (describing each syntactic unit in an IDL
source file) is transformed and formatted according
to a user–defined template. Example emitter
output, besides the implementation template and
language bindings, might include reference
documentation, class browser descriptions, or
”pretty” printouts.
emphasized. A form of double–strike printing in
which characters are printed in multiple passes
(usually two) with a slight offset, creating an
artificial bold type. Emphasized printing is used to
fill gaps and rough appearance in dot–matrix
character forms. It also prints a bold font without
changing the mounted character set. See also
boldface and double–strike.
emulation. (1.) The use of programming
techniques and special machine features to permit
a computing system to run programs written for
another system. (2.) Imitation. For example, when
one computer imitates the characteristics of
another computer.
emulator. A program that causes a computer to act
as a workstation attached to another system.
en. In the troff command, an en is half the size, in
points, of an em. In the nroff command, an em and
an en are identical size. See also em.
enable. (1.) To make functional. (2.) In interactive
communications, to load and start a subsystem.
Contrast with disable.
encapsulation. (1.) Hiding the internal
representation of data objects and implementation
details of functions from the client program. This
enables the end user to focus on the use of data
objects and functions without having to know about
their representation or implementation. (2.) In
SOM, an object–oriented programming feature
whereby the implementation details of a class are
hidden from client programs, which are only
required to know the interface of a class (the
signatures of its methods and the names of its
attributes) in order to use the class’s methods and
attributes.
encoder/decoder. In the SOM Persistence
Framework, a class that knows how to read/write
the persistent object format of a persistent object.
Every persistent object is associated with an
Encoder/Decoder, and an encoder/decoder object
is created for each attribute and instance variable.
An Encoder/Decoder is supplied by the Persistence
Framework by default, or an application can define
its own.
encrypt. To convert clear data into cipher text.
encryption key. A key generated by the makekey
command to use with programs that perform
encryption. Its input and output are usually pipes.
end signal. In an online conference, a mutually
agreed upon character that indicates the end of a
comment by a participant. Common end signals
are o and oo.
endian. An attribute of data representation that
reflects how certain multi–octet data are stored in
memory. See also big endian and little endian.
end–to–end transit delay. In X.25
communications, an optional CCITT–specified
facility.
enforced lock. A type of lock that a process holds
on a region of a file preventing any other process
from accessing that region with read or write
system calls. In addition, the create command is
prevented from truncating the files. See also
advisory lock.
enhanced graphics adapter (EGA). An adapter,
such as the Enhanced Graphics Adapter, that
provides high–resolution graphics, allowing the use
of a color display for text processing as well as
graphics applications.
Enhanced X-Windows. A collection of basic
functions for developing a variety of application
environments. Toolkit functions manage Toolkit
initialization, widgets, memory, events, geometry,
input focus, selections, resources, translation of
events, graphics contexts, pixmaps, and errors.
See also AIXwindows Environment.
enqueue. To place items in a queue. Contrast with
dequeue.
enter. (1.) To send information to the computer by
pressing the Enter key. (2.) To place a message on
the line to be transmitted from a terminal to the
computer.
Enterprise Systems Connection. See ESCON.
entry. (1.) In FORTRAN, a language construct
within a procedure, designating the start of the
execution sequences of the procedure. (2.) In Ada
language, an entry is used for communication
between tasks. Externally, an entry is called just as
a subprogram is called; its internal behavior is
specified by one or more accept statements
Glossary
1-51
specifying the actions to be performed when the
entry is called. (3.) An element of information in a
table, list, queue, or other organized structure of
data or control information. (4.) A single input
operation on a workstation.
named collection of logical and physical resources
used to support the performance of a function. (3.)
In CDE Desktop, the set of rule files, resources,
and message files that define the appearance and
behavior of a specific desktop configuration.
entry class. In the SOM Emitter Framework, a
class that represents some syntactic unit of an
interface definition in the IDL source file.
Environment parameter. In SOM, a
CORBA–required parameter in all method
procedures, it represents a memory location where
exception information can be returned by the object
of a method invocation. [Certain methods are
exempt (when the class contains a modifier of
callstyle=oidl), to maintain upward compatibility for
client programs written using an earlier release.]
entry point. (1.) An address or label of the first
instruction performed upon entering a computer
program, routine, or subroutine. A program may
have several different entry points, each
corresponding to a different function or purpose.
(2.) In a routine, any place to which control can be
passed.
entry point vector (EPV). A record in which fields
are pointers to procedures that implement the
operations defined by an interface.
entry sequence number (ESN). The number
corresponding to the order in which the record was
entered into an entry–sequenced file. The primary
index of an entry–sequenced file is based upon the
ESNs of its records. See also entry–sequenced file.
entry–sequenced file. A record–oriented file in
which the records are stored in the order in which
they were entered into the file. The primary index
of an entry–sequenced file is based on the entry
sequence numbers (ESNs) corresponding to the
order of record insertion. Also referred to as
sequential file. See also entry sequence number.
enumerated scalar type. A scalar defined by
enumerating the elements of the type. Each
element is represented by an identifier.
enumeration constant. In C language, an
identifier (with an associated integer value) defined
in an enumerator. You can use an enumeration
constant anywhere an integer constant is allowed.
enumeration data type. A type that represents
integers and a set of enumeration constants. Each
enumeration constant has an associated integer
value.
enumeration tag. The identifier that names an
enumeration data type.
enumeration type. In Ada language, a discrete
type whose values are represented by enumeration
literals which are given explicitly in the type
declaration. These enumeration literals are either
identifiers or character literals.
enumerator. An enumeration constant and its
associated value.
environment. (1.) The settings for shell variables
and paths set when the user logs in. These
variables can be modified later by the user. (2.) A
1-52
Glossary
environment variable. (1.) A variable that
describes the operating environment of the
process. Common environment variables describe
the home directory, command search path, the
terminal in use, and the current time zone (the
HOME, PATH, TERM, and TZ variables,
respectively). (2.) A variable that is included in the
current software environment and is therefore
available to any called program that requests it.
EOF. End of file.
ephemeral application. An ephemeral application
is one which does not contain any recoverable
data.
epoch. A timestamp that identifies directory
replicas as being part of the same set.
EPOW. Emergency power off warning.
EPROM. Erasable programmable read–only
memory.
EPV. See entry point vector or Entry Point Vector.
equivalence class. A grouping of characters or
character strings that are considered equal for
purposes of collation. For example, many
languages place an uppercase character in the
same equivalence class as its lowercase form, but
some languages distinguish between accented and
unaccented character forms for the purpose of
collation.
erase. To remove text from a data medium, leaving
the medium available for recording new text. See
also delete.
erase character. A character that indicates that the
previous character on the command line has been
erased.
error analysis facility. A program that provides
information about the probable cause of errors.
error–checking and correction (ECC). In a
processing unit, the detection and correction of all
single–bit errors, plus the detection of double–bit
and some multiple–bit errors.
error class. Identifies whether an error log entry is
for a hardware or software failure.
error condition. The state that results from an
attempt to run instructions in a computer program
that are not valid or that operate on data that is not
valid.
error counter. A type of error entry generated by
device driver components. Certain device drivers
can generate retry operations if an operation is not
successful on the first attempt. They use counters
to monitor the number and cause of retry
operations, and they contain algorithms that decide
when these counters should be sent to the error
log.
error device driver. A special file (psuedo device)
driver used by the error logging facilities. Error
entries are written to the error device driver by the
errlog() subroutine and the errsave() kernel
service. Error entries are read from the error device
driver by the error daemon process and saved in
the system error log file.
error ID. See error identifier.
error identifier (error ID). An 8–character code
used to identify a particular failure. There is a
unique error identifier for each error record
template.
error log. (1.) A data set or file in a product or
system where error information is stored for later
access. (2.) A form in a maintenance library that is
used to record error information about a product or
system. (3.) A data set used in a processor to
record information about certain hardware and
programming events. (4.) A record of machine
checks, device errors, and volume statistical data.
error log entry. A record in the system error log
describing a hardware or software failure and
containing failure data captured at the time of the
failure.
error message. An indication that an error has
been detected.
error output. Synonym for diagnostic output.
error record template. Describes the error class,
error type, error description, probable causes,
recommended actions, and failure data for an error
log entry.
error type. Identifies whether an error log entry is
for a permanent failure, temporary failure,
performance degradation, impending loss of
availability, or undetermined failure.
escape character (ESC). (1.) In shell
programming and TTY programming, the \
(backslash) character, which indicates that the next
character is not intended to have the special
meaning normally assigned to it. (2.) In general, a
character that suppresses or selects a special
meaning for one or more characters that follow.
escape function. The code of the form ‘ESC
Something’. One type of multibyte control function.
escape sequence. (1.) A character that is
preceded by a \ (backslash) and is interpreted to
have a special meaning to the operating system.
(2.) A sequence sent to a terminal to perform
actions such as moving the cursor, changing from
normal to reverse video, and clearing the screen.
The terminfo file defines these escape sequences.
Synonymous with multibyte control. (3.)
Multicharacter code specifying a string variable.
See also unescaped.
ESCD console. The ESCD input/output device
used to perform connectivity tasks at the ESCD.
ESCON (Enterprise Systems Connection). A
System/390 I/O architecture that uses both laser
and LED fiber–optic technology and the concept of
dynamic connectivity, which allows for path
sharing.
ESDI. Enhanced Small Device Interface.
ESN. See entry sequence number.
Ethernet. A 10–megabit baseband local area
network using CSMA/CD (carrier sense multiple
access with collision detection). The network allows
multiple stations to access the medium at will
without prior coordination, avoids contention by
using carrier sense and deference, and resolves
contention by using collision detection and
transmission.
evaluation. In Ada language, the evaluation of an
expression is the process by which the value of the
expression is computed. This process occurs
during program execution.
event. (1.) The enqueueing or dequeueing of an
element. (2.) An occurrence of significance to a
task. (3.) In computer graphics, information
generated either asynchronously from a device or
as the side–effect of a client request. Events are
grouped into types and are not sent to a client by
the server unless the client has issued a specific
request for information of that type. Events are
usually reported relative to a window. See also
callback.
ESC. See escape character.
Glossary
1-53
event class. A number assigned to a group of
trace points that relate to a specific subject or
system component. The defined event classes are
listed in the trace profile.
event control bit (ECB). A bit assigned to each
queue to signal the arrival or departure of an
element.
event loop. A sequence of steps performed
cyclically to accomplish a task. It must contain at
least one input (source) and an ending point.
event manager (EMan). The chief component of
the SOM Event Management Framework that
registers interest in various events from calling
modules and informs them through callbacks when
those events occur.
exception handling. A type of error handling that
allows control and information to be passed to an
exception handler when an exception occurs. try
blocks, catch blocks, and throw expressions are
the constructs used to implement formal exception
handling in C++.
exchange identification (XID). The ID that is
exchanged with the remote physical unit when an
attachment is first established.
exchange identification (XID) frame. In a logical
link control (LLC) header, the frame that conveys
the characteristics of the sending host.
exclusive lock. A type of lock in which only the
transaction holding the lock can access the data in
any way. See also shared locks.
event mask. In computer graphics, the set of event
types that a client requests relative to a window.
exec. To overlay the current process with another
executable program. See also fork.
event queue. In computer graphics, a queue that
records changes in input devices––buttons,
valuators, and the keyboard. The event queue
provides a time–ordered list of input events.
EXEC. Remote Command Execution Protocol.
exception. (1.) In programming languages, an
abnormal situation that may arise during the
running of a program, perhaps causing a deviation
from the normal run sequence, and for which
handling facilities exist. (2.) An abnormal condition
such as an I/O error encountered in processing a
data set or a file. (3.) One of five types of errors
that can occur during a floating–point exception.
These are an operation that was not valid,
overflow, underflow, division by zero, and inexact
results. (4.) In C++ language, any user, logic, or
system error detected by a function that does not
itself deal with the error but passes the error on to
a handling routine. Passing this error is called
throwing an exception. (5.) In Ada language, an
error situation which may arise during program
execution. To raise an exception is to abandon
normal program execution so as to signal that the
error has taken place. An exception handler is a
portion of program text specifying a response to
the exception. Execution of such a program text is
called handling the exception. Contrast with
interrupt and signal. See also handler and trap
handler.
exception handler. (1.) A set of routines used to
detect deadlock conditions or to process abnormal
condition processing. An exception handler allows
the normal running of processes to be interrupted
and resumed. (2.) Exception handlers are catch
blocks in C++. catch blocks catch exceptions when
they are thrown from a function enclosed in a try
block. try blocks, catch blocks and throw
expressions are the constructs used to implement
formal exception handling in C++.
1-54
Glossary
executable. A file that can be loaded into memory
and executed as a program. An executable is
produced by the binder (ld) from one or more
object (.o) files. The default processing of
compilation commands includes invoking the
binder to produce an executable whose name is
a.out.
executable file. A file that contains programs or
commands that perform operations on actions to
be taken.
executable program. A program that can be run
as a self–contained procedure. It consists of a main
program and, optionally, one or more subprograms.
executable statement. A statement that causes
an action to be taken by the program. For example,
to calculate, to test conditions, or to alter normal
sequential execution.
execute. In CDE, a file or folder (directory) access
permission. For files, execute permission enables
the user to run a program or shell script file. For
folders (directories), execute permission enables
the user to access the folder (directory) contents.
existing file. A file that has been defined and that
resides on a storage medium.
Exit button. In CDE, a Front Panel control used to
log out of the desktop.
exit value. (1.) A code sent to either standard
output or standard error on completion of the
command. (2.) A numeric value that a command
returns to indicate whether it completed
successfully. Some commands return exit values
that give other information such as whether a file
exists. Shell programs can test exit values to
control branching and looping.
expanded name. In Ada language, a name that
denotes an entity which is declared immediately
within some construct. An expanded name has the
form of a selected component: the prefix denotes
the construct (a program unit; or a block, loop, or
accept statement); the selector is the simple name
of the entity.
expect–send sequence. In remote
communications, a list of characters or signals a
program or modem should expect to receive from a
remote system, followed by the characters or
signals the program or modem should send to the
remote system after it receives the expected input.
The sequence can also include a subsequence that
tells the program or modem what to send if it does
not receive the expected input. See also
handshaking and chat script.
expedited data negotiation. In X.25
communications, an optional CCITT–specified
facility.
expedited data transfer. In X.25 communications,
an optional CCITT–specified facility.
expletive. An unnecessary be–verb phrase such
as ”It is” or ”there is” used to begin a sentence or
part of a sentence.
explicit binding. A form of binding that gives the
client application control over what server
machines are involved.
explicit shell. Any of a class of shells created
manually by the developer through the Create
menu’s Shells submenu.
exponent. A number indicating the power to which
another number (the base) is to be raised.
exponentiation. The operation in which a value is
raised to a power.
export. (1.) In NCS, to provide the operations
defined by an interface. A server exports an
interface to a client. Contrast with import. (2.) To
copy data onto removable media.
exposure event. In Enhanced X-Windows, an
event sent to clients to inform them when contents
have been lost, as when windows are obscured or
reconfigured. Servers do not guarantee the
preservation of window contents when they are
obscured or reconfigured.
expressed folio. A page numbering style in which
each page (possibly excluding the first page) is
numbered. See also folio, blind folio, and dropped
folio.
expression. (1.) A representation of a value. For
example, variables and constants appearing alone
or in combination with operators. (2.) In
programming languages, a language construct for
computing a value from one or more operands,
such as literals, identifiers, array references, and
function calls. In Ada language, an expression
defines the computation of a value. (3.) A
configuration of signs.
expression statement. In C language, an
expression that ends with a ; (semicolon). You can
use an expression statement to assign the value of
an expression to a variable or to call a function.
extended address. Synonym for address
extension.
extended binary–coded decimal interchange
code (EBCDIC). A code developed for the
representation of textual data. EBCDIC consists of
a set of 256 eight–bit characters.
extended character. A character other than a
7–bit ASCII character. An extended character can
be a 1–byte code point with the eighth bit set
(ordinal 128 through 255). See also code page and
code point.
extended common object file format (XCOFF).
The object file format for Version 3 of the operating
system. XCOFF combines the standard common
object file format (COFF) with the TOC module
format concept, which provides for dynamic linking
and replacement of units within an object file.
extended curses. A system library(the
libcurses.c library) that contains the control
functions for writing data to and getting data from
the terminal screen. It supports color, multiple
windows, and an enhanced character set.
extended family. The set of all of an
Ada–language compilation unit’s supporters and all
of their families, including the associated bodies
and subunits. The supporters of a unit include only
the library units required for its compilation, not the
associated bodies or subunits.
extended font. (1.) A font in which the characters
are wider than its corresponding normal font. (2.) A
collection of font sections to support languages
requiring more than 256 graphic characters at one
time.
extended interface. Provides a set of full–function
system calls (the readx and writex system calls) to
communicate with SNA Services. These calls
contain an extra parameter on the call (a pointer to
the structure containing extra function requests).
See also interface and limited interface.
extended permission. An access mode that
modifies the base permissions to a file for specified
individuals or groups. An extended permission can
deny or permit an access mode. See also
discretionary access control.
Glossary
1-55
extended precision constant. A processor
approximation to the value of a real number that
occupies 16 consecutive bytes of storage and can
assume a positive, negative, or zero value. The
precision is greater that of type double precision.
extended result. An exception notification that has
data defined in the result_ext field of the
dlc_getx_arg structure.
extended selection. In CDE, to add multiple items
to a selected set by augmenting the selection
technique. For example, you can add to a selection
by moving the pointer to a new item and pressing
Control and the SELECT mouse button
simultaneously.
Extended Services. A group of optionally installed
operating system functions and programs.
extension. In Enhanced X-Windows, to extend the
system, the named extensions can be defined for
the Core protocol, including extensions to output
requests, resources, and event types.
extent. (1.) A continuous space on disk or diskette
that is occupied by or reserved for a particular data
set, data space, or file.
exterior gateway. A gateway on one autonomous
system that communicates with other autonomous
system.
external clocking. In data communications, the
ability of a modem to provide data clocking.
external data definition. A description of a
variable appearing outside a function. It causes the
system to allocate storage for that variable and
makes that variable accessible to all functions that
follow the definition and are located in the same file
as the definition.
eXternal Data Representation (XDR). A standard
for the description and encoding of data; it uses a
languages to describe data formats, but the
language is used only for describing data and is not
a programming language. Protocols such as RPC
and NFS use XDR to describe their data formats.
1-56
Glossary
external function. In FORTRAN, synonymous with
external routine.
external modem. A modem that is separate from
the unit with which it operates.
external name. (1.) A name that can be referred to
by any control section or separately assembled or
compiled module; a control section name or an
entry name in another module. (2.) In a program, a
name whose scope is not necessarily confined to
one block and its contained blocks.
external procedure. Synonymous with external
routine.
external reference. A reference to a symbol
defined as an external name in another program or
module.
external routine. A procedure or function called
from outside the program in which the routine is
defined. Synonymous with external procedure.
external symbol. A symbol that is defined in a file
other than the file in which the symbol occurs. An
ordinary symbol that represents an external
reference.
external variable. A variable accessible to another
compilation unit. See also compilation unit.
extract. To obtain. For example, to extract
information from a file.
eye coordinates. In GL, the coordinate system in
which the viewer’s eye is located at the origin, and
thus all distances are measured with respect to the
eye. Viewing transformations map from world
coordinates into eye coordinates, and projection
transformations map from eye coordinates to
normalized device coordinates. Synonym for eye
space, viewing coordinates, and viewer
coordinates. See also modeling coordinates,
primitive coordinates, world coordinates, screen
coordinates, and transformation.
eye space. Synonym for eye coordinates.
F
F. Fahrenheit.
facilities. See optional facilities.
facilities extension. In the X.25 API, an extension
to the optional facilities field in a packet that allows
further, non–CCITT–specified, optional facility
information to be added.
factorization. An arithmetic transformation in
which common factors are removed from
subexpressions within an expression, and then
multiplied by the resulting expression.
factory method. See class method.
fake target name. A control name used in a
makefile file that looks like a target name, but
actually tells the make command to perform some
operation differently.
family. An Ada–language library unit together with
its body and subunits (if any). Not all potential
family members need be present; a library unit may
have a missing optional body, and a main program
procedure may have only an implicit specification.
The family of a secondary unit is that unit together
with any subunits.
fast select. In X.25 communications, an optional
facility that allows inclusion of data in call–request
and clear–request packets. See also optional
facilities.
FCC. Federal Communications Commission.
FCFS. See first–come–first–served.
FD. Full duplex. See duplex.
FDDI. Fiber–optic Distributed Data Interface. A
100–Mbit/sec optical LAN interface. An ANSI
standard for a high–speed, 100–Mbit/sec,
general–purpose network for the interconnection of
computers, networks, and peripheral equipment
using optical fiber cable in a dual–ring
configuration. FDDI can connect as many as 500
stations with a maximum link–to–link distance of 2
kilometers and a total LAN circumference of 100
kilometers.
FDX. Full duplex. See duplex.
feature. A programming or hardware option,
usually available at an extra cost.
fiber optics. The branch of optical technology
concerned with the transmission of radiant power
through fibers made of transparent materials such
as glass, fused silica, and plastic.
field. (1.) An area in a record or panel used to
contain a particular category of data. (2.) The
smallest identifiable component of a record. An
individually addressable subdivision of a record
containing a specific portion of the data in the
record. For example, a record of data about an
employee might be subdivided into fields
containing the employee’s name, identification
number, and salary. (3.) An area in a presentation
space into which the program accepts input. (4.) In
the INed editor, an area in a structured file defined
in the form used to enter and display data. Fields
are defined using either text data paths or tree data
paths. (5.) In video, a field is one–half of a frame.
Fields are drawn 60 times per second. See also
structured field.
field of view. In GL, the extent of the area which is
under view. The field of view is defined by the
viewing matrix in use.
field return. The action that moves a data cursor
from field to field in a reverse direction, as
determined by the panel layout.
FIFO. See first–in–first–out.
file. (1.) A collection of related data that is stored
and retrieved by an assigned name. Contrast with
special file. (2.) A sequence of records. If the file is
located in internal storage, it is an internal file; if it
is on an input/output device, it is an external file.
(3.) A collection of related information stored in a
single location for organizational purposes and
processed as a unit. See also filename.
file descriptor. A small positive integer that the
system uses instead of the file name to identify an
open file. See also shared memory ID (shmid).
file format. A description of the entries to be made
in an ASCII file, such as a configuration or
customization profile.
file index. 64 bytes of information describing a file.
The file index contains the type and size of the file
and the location of the file data on the physical
device. This index is the same as the operating
system i–node. Synonym for i–node.
file manager. A program that manipulates files or
directories.
file memory. Virtual–memory pages that are
currently in real memory that are not part of
computational memory. Normally these are pages
of nonexecutable files.
file mode creation mask. See mask.
file name. (1.) A name assigned or declared for a
file. (2.) The name used by a program to identify a
file. See also label.
file name substitution. The process in which the
shell recognizing a word (character string) that
Glossary
1-57
contains any of the *, ?, [, or { characters, or begins
with the ~ character, and replaces it with an
alphabetically sorted list of file names that match
the pattern of the word. Synonymous with globbing.
file owner. The user who has the highest level of
access authority to a file, as defined by the file.
file pointer. An identifier that indicates a structure
containing the file name.
file scope. A C++ name declared outside all blocks
and classes has file scope and can be used after
the point of declaration in a source file.
file server. In CDE, a host computer that stores
data files used by applications.
file spec. See file specification.
file specification (filespec). The name and
location of a file. A file specification consists of a
drive specifier, a path name, and a file name.
file suffix. In CDE, a suffix added to the end of a
file name, often used in file typing or to categorize
files for the user.
file system. The collection of files and file
management structures on a physical or logical
mass storage device, such as a diskette or
minidisk.
file transfer. In remote communications, the
transfer of a file or files from one system to another
over a communications link.
File Transfer Protocol (FTP). In TCP/IP, the
protocol that makes it possible to transfer data
among hosts and to use foreign hosts indirectly.
file tree. The complete directory and file structure
of a particular node, starting at the root directory. A
file tree contains all local and remote mounts
performed on directories and files.
file type. In the operating system, one of the five
possible types of files: ordinary file, directory, block
device, character device, and
first–in–first–out(FIFO or named pipe).
filename. In DOS, that portion of the file name that
precedes the extension. See also file.
fileset. (1.) An individually installable option or
update. Options provide specific function and
updates correct an error in, or enhance, a
previously installed option. (2.) One or more
separately installable, logically grouped units in an
installation package.
filetab. A kernel parameter establishing the
maximum number of files that can be open
simultaneously.
fill characters. (1.) Characters used to fill fields in
storage. (2.) Visual representations of enterable
1-58
Glossary
character positions on the display (for example,
dots in each position or vertical bars between
positions).
filter. (1.) A command that reads standard input
data, modifies the data, and sends it to the display
screen. (2.) A device or program that separates
data, signals, or materials in accordance with
specified criteria.
filter primitive. A program that separates data in
accordance with specified criteria.
fine clipping. In GL, fine clipping masks all
drawing commands to a rectangular region of the
screen. It would be unnecessary except for the
case of character strings. The origin of a character
string after transformation may be clipped out by
gross, or 3–D, clipping, and the string would not be
drawn. By doing gross clipping with the viewport
and fine clipping with the screen masks, strings can
be moved smoothly off the screen to the left or
bottom. See also clipping and gross clipping.
FINGER. Name/Finger Protocol. An
application–level Internet protocol that provides an
interface between finger command and the
fingered daemon.
firewall. A system or machine that controls the
access between outside networks and private
networks.
first–come–first–served (FCFS). In general, a
queuing technique in which the next item to be
retrieved is the item that has been in the queue for
the longest time. Synonym for first–in–first–out.
Contrast with shortest–job–next. See also
discipline.
first–in–first–out (FIFO). In the operating system,
a named permanent pipe. A FIFO allows two
unrelated processes to exchange information
through a pipe connection. Synonym for
first–come–first–served.
first–level interrupt handler (FLIH). A routine that
receives control of the system as a result of a
hardware interrupt. One FLIH is assigned to each
of the six interrupt levels.
fix number. The fix level of a program, which is an
indicator of small updates that are to be built into a
regular modification or release at a later time. The
version, release, modification, and fix levels
together comprise the program level or version of a
program. See also program level, modification
number, release number, version, and version
number.
fixed box. (1.) A geometry management
technique. (2.) A type of bounding box that has a
fixed number of children created by the parent.
These managed children do not make geometry
manager requests.
optional sign (+ or –), and one or more digits (0
through 9).
fixed disk. (1.) A flat, circular, nonremovable plate
with a magnetizable surface layer on which data
can be stored by magnetic recording. A rigid
magnetic disk used in a fixed–disk drive.(2.) The
term fixed disk is also used loosely in the industry
for boards and cartridges containing microchips or
bubble memory that simulate the operations of a
fixed–disk drive.
floating display. In text formatting, a block of text
that the nroff command keeps on one page.
However, if there is no room for a floating display
on the current page, the nroff command sets aside
the display and finishes filling the page with the text
from the input file that follows the display. When the
page is full, the nroff command places the display
at the top of the next page and then continues with
the text from the previous page. See also static
display.
fixed–disk drive. The mechanism used to read
and write information on a fixed disk.
fixed icon. An icon that is fixed on the desktop.
Fixed icons are ordinarily used for files that are
necessary to use AIX Common Desktop
Environment and therefore always appear on the
desktop, such as the Home directory.
fixed part (of a record). In Pascal, the part of a
record that is common to all instances of a
particular record type.
fixed point type. See real type.
fixed storage space. Any storage device defined
during system configuration to be an integral part
of system DASD. If a fixed storage device is not
available at some time during normal operation, the
operating system detects an error.
flag. (1.) A modifier that appears on a command
line with the command name that defines the action
of the command. A dash usually precedes a flag.
(2.) An indicator or parameter that shows the
setting of a switch. (3.) A character that signals the
occurrence of some condition, such as the end of a
word. (4.) An internal indicator that describes a
condition to the processing unit. In the processing
unit of the PC AT, flags indicate if the result of an
operation is zero, if interrupts are enabled, and
other conditions. Synonymous with condition code.
flat file. (1.) A file that has no hierarchical
structure. (2.) A one–dimensional or
two–dimensional array. A list or table of items.
flat network. A network in which all hosts are
administered by one central authority.
flattened character. An ASCII character created
by translating an extended character to the ASCII
character most like it. The code point information is
lost and the character cannot be retranslated to an
extended character. For example, a cedilla
character would be flattened to a plain ”c.”
FLIH. See first–level interrupt handler.
float constant. A number containing a decimal
point, an exponent, or both a decimal point and an
exponent. The exponent contains an ”e” or ”E,” an
floating keep. A keep ensures that bracketed text
is not broken across a page boundary, by
comparing the size of the text block against the
space remaining on the page. If it does not fit, the
block is printed at the first possible opportunity on
the following page. A fixed keep leaves the
remainder of the page blank and a floating keep
moves subsequent text onto that page.
floating license. See concurrent–use license.
floating point. A way of representing real numbers
(that is, values with fractions or decimals) in 32 bits
or 64 bits. Floating–point representation is useful to
describe very small or very large numbers.
floating–point constant. A constant
representation of a floating–point number
expressed as an optional sign followed by one or
more digits and including a decimal point. See also
floating–point number.
floating–point exception. See exception.
floating–point number. A real number
represented by a pair of distinct numerals. The real
number is the product of the fractional part, one of
the numerals, and a value obtained by raising the
implicit floating–point base to a power indicated by
the second numeral. See also floating–point
constant.
floating point type. See real type.
flow control. In X.25 communications, the
procedure for controlling the data transfer rate.
flow diagram. Deprecated term for flow chart.
flyback. A movement similar to a reversing line
feed.
FM. See frequency modulation.
FM Header. Function Management Header.
focus window. Synonym for input focus.
fold. (1.) To compact data by combining parts of
the data; for example, to transform a two–word
numeric key by adding the numeric equivalents of
Glossary
1-59
the letters. (2.) To translate the lowercase
characters of a character string into uppercase.
See also constant folding. (3.) To place on the next
line a portion of a line that does not fit on the line.
Contrast with truncate.
folder. (1.) In Message Handler, a directory of
messages. (2.) In CDE, an icon that represents a
directory.
folio. A page numbering format that places the
page number at the outside of the running head at
the top of the page. See also blind folio, dropped
folio, and expressed folio.
font. (1.) A set of characters in a particular style.
See also raster font and primitive font. (2.) In
Enhanced X-Windows, a set of glyphs, usually
characters. The protocol does not translate or
interpret character sets. The client indicates values
used to access the glyph arrays. A font contains
additional metric information to determine
inter–glyph and inter–line spacing. (3.) A complete
set of graphic characters of the same size, style,
and typeface. For example, a Times 12 point font is
different in size from a Times 24 point font, different
in style from a Helvetica 12 point font, and different
in typeface from a Times 12 point boldface font.
font ascent. Height of a character in a specified
font.
font list. In AIXwindows, a list of available fonts
specified by the fontlist parameter. Also, the list of
fonts to be used in formatting a source document.
See also font table.
font structure. A data structure that contains all
the information necessary to create a font set.
font table. A list of all fonts that have been loaded
into the system. See also font list.
font unit. Any group of characters regarded as a
whole, especially for the determination of values,
variables, and other data pertaining to font
characteristics.
footer. Text that appears at the bottom of every
page of a document, for example, a page number.
footnote. A note of reference, explanation, or
comment placed below the text of a column or
page, but within the body of the page above the
footer.
footnote text. The text within the footnote.
for statement. In programming languages, a
statement that executes one or more statements
for each of a set of values assigned to one or more
variables.
foreground. (1.) A mode of running a program in
which the shell waits for the program specified on
1-60
Glossary
the command line to complete before responding
to user input. (2.) In multiprogramming, the
environment in which high–priority programs are
run. Contrast with background.
foreground color. A single color assigned to all of
the graphic elements that appear in front of all the
background graphic elements within a displayed
image. Contrast with background color.
foreground process. A process that must run to
completion before another command is issued to
the shell. The foreground process is in the
foreground process group, which is the group that
receives the signals generated by a terminal.
Contrast with background process.
foreign cell.A cell other than the one to which the
local machine belongs. See also local cell.
foreign host. Synonym for remote host.
fork. To create and start a child process. See also
exec.
form. A predefined INed structured file with
specially defined fields that allow you to view and
edit special types of data.
formal parameter. A parameter declared in a
routine heading. It specifies what can be passed to
a routine as an actual parameter. See also
conformant string and dummy argument. For Ada
programming, see also parameter. Contrast with
actual parameter.
format. (1.) A defined arrangement of such things
as characters, fields, and lines, usually used for
displays, printouts, or files. (2.) The pattern that
determines how data is recorded. (3.) To arrange
such things as characters, fields, and lines. (4.) In
programming languages, a language construct that
specifies the representation, in character form, of
data objects in a file. See also formatted data.
formatted data. Data that is transferred between
main storage and an input/output device according
to a specified format. See also list–directed data
and format.
formatted diskette. A diskette on which track and
control information for a particular computer
system has been written but that may or may not
contain any data.
formatter. (1.) A computer program that prepares
a source document for printing. (2.) The part of a
text processor that formats input lines for printing
or display on a particular type of device.
FORTRAN (FORmula TRANslation). A high–level
programming language used primarily for scientific,
engineering, and mathematical applications.
forward difference matrix. In GL, 4x4matrix that
is iterated by adding each row to the next and the
bottom row is output as the next point. Points so
generated generally fall on a rational cubic curve.
FP. See FPU.
FPU (FP). Floating–point unit.
fragment. A unit of disk storage that is smaller that
a (4KB) page.
frame. (1.) In a high–level data link control (HDLC),
the sequence of contiguous bits bracketed by and
including opening and closing flag (01111110)
sequences. (2.) A set of consecutive digit time slots
in which the position of each digit time slot can be
identified by reference to a frame alignment signal.
(3.) In an interlaced video monitor, a frame consists
of two fields, called ”even” and ”odd”, each of which
is one sixtieth of a second in duration. (4.) In
block–multiplexer–channel–adapter and ESCON
transmissions, the block of data that is transferred
between the S/370 and the workstation in one
CCW. (5.) A block of information corresponding to
the FDDI protocol which is transmitted between two
or more stations on a ring. An FDDI frame is similar
to a packet.
frame buffer. A quantity of video RAM (VRAM)
that is used to store the image displayed on the
monitor. The frame buffer is the electronic canvas
on which every drawing primitive is drawn. It is one
of the last stops in the graphics pipeline, where the
final image resides in the form of digitally coded
intensities and brightnesses. These are converted
into analog voltage signals 60 times a second and
sent to the electron guns of the monitor. The
dimensions of the frame buffer can be changed
with GL. Typically, the main frame buffer might be
1024 pixels vertical by 1280 pixels horizontal by 8
color bits. The overlay planes might by
1024x1280x2. The z–buffer is considered a frame
buffer, although it is not directly visible from the
monitor. (There is no direct means of displaying the
contents of the z–buffer, although this can be done
indirectly.) The size of the z–buffer is typically
1024x1280x24. The cursor is a very specialized
form of a frame buffer; one which can move
around. The typical cursor is 32x32x2 in size. See
also raster.
frame burst. A group of transmitter receive frames
that are contiguous on the media.
frame level. In X.25 communications, the level
between the physical level and the packet level,
which works according to the high–level data link
control procedure (HDLC). Synonymous with
data–link level and level 2. See also level, packet
level, and physical level.
frame–level interface. In X.25 communications,
the level of the DTE/DCE interface in packet mode
operation relating to the exchange of packets with
local error control, where packets are contained in
frames. See also packet–level interface.
frame window. In X.25 communications, the
number of frames that can be outstanding without
acknowledgment. See also packet window and
window.
framing error. An asynchronous transmission error
usually caused by the number of bits per character
not being set the same on the sending and
receiving workstations.
free list. A list of available blocks on each file
system.
free–block list. See free list.
free space. Space reserved within the control
intervals of a key–sequenced data set or file, used
for inserting new records into the data set or file in
key sequence; also, whole control intervals
reserved in a control area for the same purpose.
Synonym for distributed free space.
frequency modulation (FM). Modifying the
frequency of a fixed amplitude carrier signal in
accordance with an informational signal so that it
can carry data signals.
friend class. A C++ class in which all the member
functions are granted access to the private and
protected members of another class. It is named in
the declaration of another class and uses the
keyword friend as a prefix to the class. For
example, class me { on one line followed by
friend class you; on the next and then //
... and ending with }; makes all the
functions in class you friends of class me .
friend function. A C++ function that is granted
access to the private and protected parts of a
class. It is named in the declaration of the class
and uses the keyword friend as a prefix.
front and back buffers. In GL, in double buffer
mode, the main frame buffer bit planes are
separated into two sets––the front and back
buffers. Bits in the front buffer planes are visible
and those in the back buffer are not. Typically, an
application draws into the back buffer and views
the front buffer for dynamic graphics.
Front Panel. In CDE, a centrally located window
containing controls for accessing applications and
utilities, including the workspace switch. The Front
Panel occupies all workspaces.
Front Panel control. In CDE, an object in the
Front Panel used as an interface to basic system
Glossary
1-61
services and frequently performed tasks and
operations. Controls in the default Front Panel are:
Clock, Calendar, Mailer, Text Editor, Help Viewer,
File Manager, Printer, Style Manager, Application
Manager, and Trash Can. See also control.
Front Panel move handles. In CDE, an area on
each end of the Front Panel used for moving the
Front Panel and for bringing it to the front of the
workspace.
frustum. In GL, a truncated, four–sided pyramid;
that is, a pyramid with the point cut off. In a
perspective projection, the shape of the clipping
volume is a frustum. The bottom of the frustum is
referred to the far clipping plane, the top of the
frustum is the near clipping plane, and the sides
are respectively the top, left, bottom, and right
clipping planes. In an orthographic projection, the
clipping volume is a parallelepiped. See also
clipping panes.
FTP. File Transfer Program. See also File Transfer
Protocol.
full backup. Backup copies of all the files on the
system. Contrast with incremental backup.
full duplex (FDX). Synonym for duplex.
full high. Pertains to a storage device that has the
original height (82.5 mm or 3.25 inches), width
(146 mm or 5.75 inches), and length (203 mm or
8.0 inches). See also half high.
full path name. The name of any directory or file
expressed as a string of directories and files
beginning with the root directory. See also fully
qualified name, path name, and relative path
name.
full–screen editor. An editor that displays an
entire screen at a time and that allows data to be
accessed and modified only by moving the cursor
and entering commands.
fullword. Synonym for word.
fully qualified host name. A complete qualified
name. Includes all names in the hierarchical
sequence above the structure member to which the
name refers, as well as the member itself.
fully qualified name. A qualified name that
includes all names in the hierarchical sequence
above the structure member to which the name
refers, as well as the name of the member itself.
See also full path name.
function. (1.) A specific purpose of an entity, or its
characteristic action. (2.) A machine action such as
1-62
Glossary
carriage return or line feed. (3.) A subroutine that
returns the value of a single variable and that
usually has a single exit, such as subroutines that
compute mathematical functions. Synonymous with
procedure. For Ada programming, see also
subprogram.
function call. An expression that moves the path
of execution from the current function to a specified
function and evaluates to the return value provided
by the called function. A function call contains the
name of the function to which control moves and a
parenthesized list of values.
function declarator. The part of a function
definition that names the function, provides
additional information about the return value of the
function, and lists the function parameters.
function definition. The complete description of a
function. A function definition contains an optional
storage class specifier, an optional type specifier, a
function declarator, optional parameter
declarations, and a block statement (the function
body).
function keys. Keys that request actions but do
not display or print characters. This includes the
keys that normally produce a printed character, but
produce a function instead when used with the
code key. See also character key.
function pointer. An identifier that gives the
location of a function or procedure.
function reference. The appearance of an intrinsic
function name or a user function name in an
expression.
function scope. C++ labels that are declared in a
function have function scope and can be used
anywhere in that function.
function subprogram. See function.
function template. Provides a blueprint describing
how a set of related individual C++ functions can
be constructed.
functional equivalence. A situation in which
different algorithms for a given problem domain
yield identical results.
funnelling. Forcing device drivers and kernel
extensions that are not known to be MP safe to run
only on the master processor.
FX. See FXU.
FXU (FX). Fixed–point unit.
GContext. See graphics context.
G
GCP. Graphics Control Processor.
gadget. In AIXwindows, a windowless graphical
object that looks like its equivalent like–named
widget but does not support the translations,
actions, or Popup widget children supplied by that
widget.
GCR. Group Code Recording, a magnetic tape
recording format with a density of 6250 bpi.
gadget ID. In AIXwindows, a unique identification
number assigned to each instance of a gadget
used within a given graphical interface.
general purpose register (GPR). An explicitly
addressable register that can be used for a variety
of purposes (for example, as an accumulator or an
index register). See also register.
gamma correction. In GL, a logarithmic
assignment of intensities to lookup table entries for
shading applications. This is required since the
human eye perceives intensities logarithmically
rather than linearly. See also gamma ramp.
gamma ramp. In GL, a set of three lookup tables,
one for each of the colors red, green, and blue,
attached to the electron guns of the monitor.
Entries in the gamma lookup table can be set to
adjust for variations in the phosphor quality
between different brands of monitors. Usually, a
logarithmic curve is loaded into the gamma lookup
tables. See also gamma correction. The gamma
lookup tables are not a subset of the color map
tables, but a separate entity.
gateway. (1.) An entity that operates above the link
layer and translates, when required, the interface
and protocol used by one network into those used
by another distinct network. (2.) The network that
connects hosts. See also active gateway. (3.) A
device and its associated software that
interconnect networks or systems of different
architectures. The connection is usually made
above the reference model network layer. For
example, a gateway allows LANs access to
System/390 host computers. Contrast with bridge.
gateway host. A host that connects independent
networks. It has multiple interfaces, each with a
different name and address.
Gateway–to–Gateway Protocol (GGP). The
protocol with which a gateway determines
connectivity to networks and neighbor gateways
and implements the shortest–path routing
algorithm.
gather. For input/output operations, to read data
from noncontiguous memory locations to write to a
device. Contrast with scatter.
GB. See gigabyte.
GC. See graphics context.
GC caching. In Enhanced X-Windows, allows
independent change requests to be merged into
one protocol request.
GDA. Global Directory Agent.
GDLC. See generic data link control.
generation. (1.) A means of referencing items in
terms of time and ancestry so that an item without
antecedents is designated as the first (n–th)
generation and subsequent derivations are
designated as n–1, n–2, and so on. (2.) For some
remote systems, the translation of configuration
into machine language.
generation number. A number used to
differentiate between the uses of the same inode
for several files or for different versions of the same
file. When a file is created, an inode is allocated for
the file, and a new generation number is stored in
the inode for that file. Any use of an inode with the
wrong generation number indicates that the user’s
view of the file is out–of–date, or ”stale.”
generation phase. The part of the sort program
that translates the sequence specifications into
machine language.
generic data link control (GDCL). A generic
interface definition that provides application and
kernel users a common set of commands to control
DLC device managers within the operating system.
Requirements for entry–point definitions, functions
provided, and data structures for all DLC managers
are specified. The following DLCs conform to this
interface: IEEE 802.3 Ethernet, standard Ethernet,
SDLC, and Token Ring.
generic interface. The interface, defined at a level
that is independent of any particular programming
language.
generic network. A Network Installation
Management (NIM) network type used to define
networks which are not currently known by NIM to
support network boot operations.
generic unit. In Ada language, a template either
for a set of subprograms or for a set of packages.
A subprogram or package created using the
template is called an instance of the generic unit. A
generic instantiation is the kind of declaration that
creates an instance. A generic unit is written as a
subprogram or package but with the specification
prefixed by a generic formal part which may
Glossary
1-63
declare generic formal parameters. A generic
formal parameter is either a type, a subprogram, or
an object. A generic unit is one of the kinds of
program unit. See also instance.
accessible by any program of a task set in the
partition at a given time. The same area may be
used by other task sets that run in the same
partition.
geometric text. Text whose character fonts are
defined by mathematical descriptions of the strokes
required to draw the characters, rather than by
raster images. Also called programmable character
set or stroke text.
global character. The * and ? special characters
that can be used in a file specification to match one
or more characters. For example, placing ? in a file
specification means any character can be in that
position.
geometry. In Enhanced X-Windows, (1.) Window
size and position on the screen. (2.) The size of a
widget is changed using geometry management
routines. Synonym for layout and geometry
management.
global data. Data that can be addressed by any
process while in kernel mode, for example, tables,
such as the open file table and process table, and
other data maintained by the kernel, such as buffer
pointers.
geometry management. Synonymous with
geometry.
global forward substitution. An optimization in
which the result of an assignment can be
propagated forward through a program. For
example, the assignment B=C followed by A=B can
be replaced by A=C if B is not used elsewhere in
the program.
GGP. See Gateway–to–Gateway Protocol.
ghost icon. An icon that indicates that a file is
missing.
ghost instrument. In the Performance Toolbox, an
empty space in the console where an instrument
used to be, usually caused when a console
designed for one system contains instruments not
available on the current system. Ghost instruments
occupy a space and prevent a new instrument from
being defined in that same space or other
instruments from being moved or resized to use
the space.
Global Location Broker (GLB). Part of the NCS
Location Broker. A server that maintains global
information about objects on a network or an
internet.
ghosted. A description of an unavailable choice.
Menu items are ghosted or ”grayed out” to indicate
that a standard choice is not available under the
current circumstances.
glossary window. A window that contains a
glossary term.
GID. See group number.
gigabyte (GB). 1 073 741 824 in decimal notation
when referring to memory capacity; in all other
cases, it is defined as 1 000 000 000.
GL. Graphics Library.
GLB. See Global Location Broker.
glbd. The Global Location Broker daemon.
global. (1.) In programming languages, pertaining
to the relationship between a language object and
a block in which the language object has a scope
extending beyond that block but contained within
an encompassing block. (2.) Pertaining to
information defined in one subdivision of a
computer program and used in at least one other
subdivision of the program. (3.) Pertaining to
information available to more than one program or
subroutine.
global area. (1.) A storage area used for
communication between two or more main
programs. (2.) An uninitialized portion of a partition
1-64
Glossary
global variable. A symbol defined in one program
module but used in other independently assembled
program modules.
globbing. Synonym for file name substitution.
glyph. (1.) An image, usually of a character, in a
font. (2.) A graphic symbol whose appearance
conveys information; for example, the vertical and
horizontal arrows on cursor keys that indicate the
directions in which they control cursor movement.
good citizenship. A group of standards
established by the Inter–Client Communications
Conventions Manual (ICCCM) that are supported
and implemented by AIXwindows Window
Manager. These standards prescribe behavior
among clients in a multiclient environment to avoid
costly compatibility problems.
goto statement. In programming languages, a
statement that transfers control to another point in
a program.
Gouraud shading. A method of shading polygons
smoothly based on the intensities at their vertices.
The color is uniformly interpolated along each
edge, and then the edge values are uniformly
interpolated along each scan line. For realistic
shading, colors should be gamma corrected.
GPR. See general purpose register.
grab. (1.) The act of selecting keyboard keys, the
keyboard, pointer buttons, the pointer, and the
server for exclusive use by a client. In general,
these facilities are not intended to be used by
normal applications, but are intended for various
input and window managers to implement various
styles of user interfaces. See also active grab,
passive grab, button grabbing, pointer grabbing,
and key grabbing. (2.) A procedure by which a
window acts upon a key or button event that occurs
for it or any of its descendents. This precludes the
necessity of setting up translations for all windows.
graPHIGS API. An implementation of PHIGS,
based on the American National Standards
Institute (ANSI) proposed standard, Programmer’s
Hierarchical Interactive Graphics System (PHIGS).
gravity. In Enhanced X-Windows, the contents of
windows or subwindows have an attraction to a
location within the window. This determines how
the window ID is resized. See also bit gravity and
window gravity.
grammar rules. The structure rules in a parser
program. See also parser.
gray scale. (1.) In Enhanced X-Windows, a type of
degenerate pseudocolor where the red, green, and
blue values in any given color map entry are equal,
thus producing shades of gray. The gray values
can be changed dynamically. (2.) Also GrayScale,
a value. (3.) In a grayscale adapter, the different
levels of intensity corresponding to the shades of
gray produced. See also monochrome display.
granularity. The extent to which a larger entity is
subdivided. For example, a yard broken into inches
has finer granularity than a yard broken into feet.
grayed. A characteristic of a command or option
that is listed on a menu or list box but cannot be
chosen.
graphic character. A character that can be
displayed or printed.
gross clipping. In GL, also known as 3–D clipping
this is the clipping that occurs in normalized device
coordinates, against the sides of the perspective
frustum. All 3–D primitives undergo this clipping; in
particular, the origin of text strings (but not
individual letters) are clipped in this way. See also
clipping, fine clipping, and clipping planes.
grab handles (or handles). In CDE, the small
squares displayed at the corners and midpoints of
a selected graphic element.
graphical user interface. (1.) A boundary
between two functional units that is displayed to the
user by means of fundamental drawing units such
as lines and polygons. (2.) A type of computer
interface consisting of a visual metaphor of a
real–world scene, often a desktop. Within that
scene are icons, representing actual objects, that
the user can access and manipulate with a pointing
device. (Also called graphical interface.)
graphics. A type of data created from such
fundamental drawing units such as lines, curves,
polygons, and so forth.
graphics context (GC). In Enhanced X-Windows,
the storage area for various kinds of graphics
output, such as foreground pixel, background pixel,
line width, and clipping region. Also known as ”GC”
and ”GContext,” a graphics context can be used
only with drawables that have the same root and
the same depth as the graphics context.
graphics pipeline. In GL, the sequence of steps
that a graphics primitive goes through before it
becomes visible on the screen: transformation from
model coordinates to NDC coordinates; 3–D
clipping (if out of bounds); perspective division;
determination of color through lighting equations or
depth–cueing; transformation of NDC coordinates
to screen coordinates; 2–D clipping (by the
screenmask); rasterization (drawing into the frame
buffer); and display of frame buffer.
Graphics Support Library (XGSL). A
two–dimensional graphics application programming
interface to various output devices.
group. (1.) A collection of users who can share
access authorities for protected resources. (2.) A
list of names that are known together by a single
name. (3.) A series of records logically joined
together. (4.) A series of lines repeated
consecutively as a set on a full–screen form or
full–screen panel. (5.) A set of related records that
have the same value for a particular field in all
records.
Group Appointment. In CDE, in Calendar, an
appointment for a group of people, scheduled
using the Group Appointment Editor.
group ID (GID). A number that corresponds to a
specific group name. The group ID can often be
substituted in commands that take a group name
as a value. Synonymous with group number.
group name. A name, which uniquely identifies a
group of users to the system, that contains one to
eight alphanumeric characters, beginning with an
alphabetic, #, $, or > character.
group number. Synonym for group ID.
guard expressions. Expressions placed at the
beginning of Boolean expressions to check that
other operations can be done.
Glossary
1-65
hash codes. Format in which data is stored in
compressed form.
H
half duplex (HD or HDX). Pertains to
communications in which data can be sent in only
one direction at a time. Contrast with duplex.
hash signature. The fixed–length bit string
resulting from hashing a character string.
Character strings may be compared quickly by
comparing their hash signatures.
half high. Pertains to a storage device that has
one half the height (41.3 mm or 1.63 inches) with
the width and length the same as the full high
device. See also full high.
hash table. A table of information that is accessed
by way of a shortened search key (the hash value).
Using a hash table minimizes average search time.
half–session. A component that provides data
flow control and transmission control at one end of
a session.
hashing. (1.) A method of transforming a search
key into an address for the purpose of storing and
retrieving items of data. (2.) Encoding a character
string as a fixed–length bit string for comparison.
The encoding may not necessarily be unique.
halfword. A contiguous sequence of bits or
characters that constitutes half a computer word
and can be addressed as a unit. Contrast with
word.
hand tuning. The process of modifying source
code by hand to improve the performance of the
resulting object code. Hand tuning is one aspect of
optimization.
handle. A data structure that is a temporary local
identifier for an object. You create a handle by
allocating it. You make a handle identify an object
at a specific location by binding it.
HCON. See 3270 Host Connection Program 2.1
and 1.3.2 for AIX
HCONMRI. 3270 Host Connection Program 2.1
and 1.3.2 for AIX Message Catalog.
HCONuser. A user who has been given the special
permissions necessary to use the 3270 Host
Connection Program 2.1 and 1.3.2 for AIX (HCON).
See also 3270 Host Connection Program 2.1 and
1.3.2 for AIX.
HD. See half duplex.
handler. A software routine that controls a
program’s reaction to specific external events, such
as an interrupt handler. For Ada programming, see
exception.
HDLC. See high–level data link control.
handshaking. The process used by modems and
equipment, before transmitting data, to establish an
electrical path and synchronization. See also chat
script and expect–send sequence.
header. (1.) Constant text that is formatted to be in
the top margin of printed pages in a document. (2.)
System–defined control information that precedes
user data. (3.) The portion of a message that
contains control information for the message such
as destination fields, originating station, and priority
level. (4.) In CDE, in Mailer, the basic information
about an electronic mail message as it appears in
the mailer container. A message header displays
the name of the sender, subject, the date and time
it was received, and message size.
hard copy. A printed copy of machine output in a
visually readable form such as printed reports,
listings, documents, and summaries.
hard disk. See fixed disk.
hard–disk drive. See fixed–disk drive.
hard link. A mechanism that allows the ln
command to assign more than one name to a file.
Both the new name and the file being linked must
be in the same file system.
hard return. In an Interleaf textfile, a control
character created by pressing Shift–Enter that
causes text to wrap to the next line.
hard space. In an Interleaf file, a nonbreaking
space character.
hardware. The physical equipment of computing
and computer–directed activities. The physical
components of a computer system. Contrast with
software.
1-66
Glossary
HDR. See header label.
HDX. See half duplex.
header file. A text file that contains declarations
used by a group of functions or users. Synonymous
with include file.
header label (HDR). A special set of records on a
diskette describing the contents of the diskette.
header page. A separator page that precedes a
printed file or a print job.
header record. A record at the beginning of a file
that details the sizes, locations, and other
information that follows in the file.
heap. A collection of dynamically allocated
variables.
HELLO. DCN Local–Network Protocol. An interior
gateway protocol designed for use within
autonomous systems.
’Hello, World’. The standalone sample program
that introduces the fundamental construct provided
by Tran–C.
help. One or more display images that describe
how to use application software or how to do a
system operation.
help callback. A function that calls a help.
help file. A file, separate from the source code of a
program, that contains help definitions in a special
help format that Base Operating System message
services can use.
Help Manager. In CDE, a special help volume that
lists all the online help registered on your system.
Help Viewer. In CDE, the software application that
displays online help.
help volume. In CDE, a complete body of help
information about a subject.
helper. A program used by the INed editor to
provide extra functions for a particular type of data
file.
hertz (Hz). A unit of frequency equal to one cycle
per second.
heuristics. Guidelines that a system administrator
uses to intervene where the two–phase commit or
abort would otherwise fail.
hex. See hexadecimal.
hexadecimal (hex). Pertaining to a system of
numbers to the base sixteen; hexadecimal digits
range from 0 (zero) through 9 (nine) and A (ten)
through F (fifteen).
hexadecimal constant. (1.) The characters 0x or
0X (zero X) followed by any digits 0 through 9 and
uppercase or lowercase letters A through F. (2.) A
constant, usually starting with special characters,
that contains only hexadecimal digits.
HIA. See System/370 Host Interface Adapter.
hidden file. An operating system file that is not
displayed by a directory listing. The name of a
hidden file usually begins with a period.
hidden surface. A surface of a geometric primitive
that is not visible because it is obscured by other
surfaces. See also z–buffer.
hierarchical file system. In CDE, a way to
organize data on computer systems using a
hierarchy of containers, often called folders
(directories) and files. In this scheme, folders may
contain other folders and files. The successive
containment of folders within folders creates the
levels of organization, which is the hierarchy.
hierarchical network. A network in which hosts
are administered by a tree structure of authority.
This network structure relieves the administrative
burden of the central authority.
hierarchy. A series of elements that have been
graded or ranked in some useful manner. In
AIXwindows, more than 40 classes of graphical
objects are ranked top–down from the simplest to
the most complex to determine the relative order of
inheritance of appearance resources and behavior
resources.
high–level data link control (HDLC). In data
communications, the use of a specified series of
bits to control data links in accordance with the
International Standards for HDLC: ISO 3309 Frame
Structure and ISO 4335 Elements of Procedures.
high–order. Most significant; leftmost. For
example, bit 0 in a register.
higher layer or level. The conceptual level of
control or processing logic existing in the
hierarchical structure of a station that is above the
link layer and upon which the performance of data
link functions are dependent (for example, device
control, buffer allocation, station management).
See also level.
highlight. To emphasize an area on the display
screen by any of several methods, such as
brightening the area or reversing the color of
characters within the area.
hiragana. A graphic character set consisting of
symbols used in one of the two common Japanese
phonetic alphabets. Each character is represented
by 1 byte.
history. A list of Ada debugger commands entered
recently. The history command has a default list of
the 20 most recently entered commands. You can
use history to re–enter a previous command, or to
form a new command by editing the history
reference text.
hit. In GL, also called pick hit or select hit. A hit
occurs whenever a drawing primitive draws within
the picking or selecting region. A hit is reported
back to the user only if the name stack has
changed since the last hit. In other words, multiple
hits may occur although only one pick/select event
is reported. See also picking, picking region,
selecting region, and selecting.
H&J. In C.A.T terminology, the (usually automatic)
process of hyphenation and justification.
hog factor. In system accounting, an analysis of
how many times each command was run, how
Glossary
1-67
much processor time and memory it used, and how
intensive that use was.
hole in a file. Empty space in a sparse file that is
left open for future additions of data. See also
sparse file.
Hollerith constant. In FORTRAN, a string of any
characters capable of representation in the
processor and preceded by nH, where n is the
number of characters in the string.
HOME. See $HOME.
home cell. See local cell.
home directory. (1.) A directory associated with an
individual user. (2.) The user’s current directory
after login or after issuing the cd command with no
argument. (3.) A parameter that supplies the full
path name of the home directory for the transaction
program.
home folder. In CDE, a folder where you keep
personal files and additional directories. By default,
File Manager and Terminal Emulator windows are
set to the home folder when you first open them.
When discussing command–line activities, may be
called the home directory.
home session. In CDE, a choice at logout to
designate a particular session, other than the one
you are currently in, as the one you will
automatically return to at the next login. Contrast
with current session.
home–window. A window that completely displays
the contents of the display buffer.
homogeneous coordinates. A four–dimensional
method of representing three–dimensional space.
A point (x, y, z, w) in homogeneous coordinates is
used to represent a point (X, Y, Z) in
three–dimensional space by taking X=x/w, Y=y/w,
and Z=z/w. See also parametric bicubic surface.
hop count. In the Token–Ring Network, the
number of bridges through which a frame passes
on the way to its destination.
hop count metric. (1.) In a gateway, indicates that
the next string represents the hop count to the
destination host or network. (2.) The number of
host–to–host connections in a route.
host. (1.) The primary or controlling computer in
the communications network. (2.) A computer
attached to a network.
host ID. An identifier for a host. A host ID uniquely
identifies a host within an address family on a
network but does not identify the network. A host
ID is not necessarily sufficient to establish
communications with a host.
host name. (1.) A name assigned to a computer
connected to a network. The use of this term can
be ambiguous as it can refer to either the short
form name of the computer, or the fully qualified
name of the computer. (2.) The Internet address of
a machine in the network. Also known as host ID.
hotspot. The spot associated with a cursor that
corresponds to the coordinates reported for the
pointer. A cursor has an associated hotspot, which
defines a point in the cursor that corresponds to
the coordinates reported for the pointer.
HTML. HyperText Markup Language (HTML) is the
tagging language that a web browser uses to
interpret and display documents.
Huffman coding. A character–coding technique to
compress data.
hyper–integer. An XDR standard that defines
64–bit (8–byte) numbers that are the extensions of
integers and unsigned integers.
hyperlink. In CDE, in Help text, text or a graphic
you click to display another Help topic.
hook ID. A unique number assigned to a specific
trace point. All trace entries include the hook
identifier of the originating trace point in the trace
entry header. A hook ID is a 12–bit value. For user
programs, the hook ID may be a value from 0x010
to 0x0FF. Hook identifiers are defined in the
/usr/include/sys/trchkid.h file.
hypertext. A way of presenting information online
with connections between one piece of information
and another. These connections are called
hypertext links. Thousands of these hypertext links
enable you to explore additional or related
information throughout the online documentation.
See also hypertext link.
hooking routines. Functions that connect with the
library but remain outside the library; protocol
extension procedures. Synonym for stub.
hypertext link. A connection between one piece of
online information and another. See also hypertext.
1-68
Glossary
Hz. See hertz.
I
IAR. See instruction address register.
IC. See ICU.
ICCC. Inter–Client Communications Conventions.
A standard abbreviation for the manual that
contains a detailed set of guidelines for client
applications using the Enhanced X-Windows
system and the AIXwindows toolkit. See also
ICCCM.
ICCCM. Inter–Client Communications Conventions
manual. See also ICCC.
ICMP. See Internet Control Message Protocol.
the resource. An identifier can be used over any
connection to name the resource.
IDL source file. In SOM, a user–written .idl file,
expressed using the syntax of the Interface
Definition Language (IDL), which describes the
interface for a particular class (or classes, for a
module). The IDL source file is processed by the
SOM Compiler to generate the binding files specific
to the programming languages of the class
implementor and the client application. (This file
may also be called the ”IDL file,” the ”source file,”
or the ”interface definition file.”)
idle list. A list of secondary stations on a network
that are polled less often by the primary station due
to their inactivity.
idle time. The part of operable time during which a
functional unit is not operated.
icon. (1.) A picture or graphical representation of
an object on a display screen to which a user can
point to with a device such as a mouse in order to
select a particular operation or perform a certain
action. (2.) In CDE Desktop, the visual
representation of a file or directory, or an object
used by the desktop, consisting of a picture on the
desktop or in a directory window.
IDP. Internet Datagram Protocol. A simple,
unreliable datagram protocol, which is used to
support the SOCK_DGRAM abstraction for the
Internet Protocol family.
icon box. In AIXwindows, a window used as a
visual storage area for icons representing
minimized windows.
IEEE 754. Binary Floating Point Standard.
Icon Editor. In CDE, the software application used
to create new icons and to modify existing icons.
icon layout policy. In AIXwindows, a specification
that determines whether icons representing
minimized windows are placed on the root window
or within an icon box.
iconify. See icon.
ICU (IC). Instruction cache unit.
ID. Identification. See identifier.
idempotent. A class of operations. An operation is
idempotent if its results do not affect the results of
any operation. For example, a call that returns the
time is idempotent.
identifier (ID). (1.) A name that refers to a data
object. An identifier contains some combination of
letters, digits, and underscores, but its first
character cannot be a digit. (2.) In programming
languages, a lexical unit that names a language
object, such as the name of an array, record, label,
or procedure. An identifier usually begins with a
letter optionally followed by letters, digits, or other
characters. (3.) A sequence of bits or characters
that identifies a program, device, or system to
another program, device, or system. (4.) In
Enhanced X-Windows, a unique value associated
with a resource that a client program uses to name
IEEE. Institute of Electrical and Electronics
Engineers.
IEEE 802.3. Ethernet LAN specification.
IEEE 802.5. Token–Ring LAN specification.
IETF. Internet Engineering Task Force.
IF expression. An expression in a procedure that
tests for a condition. The action performed by the
procedure depends on the result of the test.
if statement. (1.) A C language conditional
statement that contains the keyword if followed by
an expression in parentheses (the condition), a
statement (the action), and an optional else clause
(the alternative action). (2.) A conditional statement
that specifies a condition to be tested and the
action to be taken if the condition is satisfied.
I–field. Information field.
I–field bytes. Data within the information field of a
transmit or receive sequenced data frame.
ignore. In DOS, the option to disregard the device
error and continue processing.
i–list. In a Base Operating System file system,
blocks 2 through n compose the i–list, which
contains structures (i–nodes) that relate a file to the
data blocks or disk. The size of the i–list depends
on the size of the mounted file system. See also
i–node and superblock.
Glossary
1-69
illegal. A violation of an architecture rule that an
implementation is required to report. See also
unpredictable.
image cache. In AIXwindows, a means of
associating an image with a name. Once this
association is in place, the appropriate AIXwindows
subroutines can generate pixmaps through
references to an .Xdefaults file (by name) and
through an argument list (by pixmap). See also
pixmap.
image structure. The existing image in an
XmInstallImage function.
immediate data. (1.) In Assembler language,
actual data appearing in an instruction, as opposed
to the symbolic name of some data. The data is
immediately available from the instruction and
therefore does not have to be read from memory.
(2.) Data transferred during instruction run time.
immediate mode. In GL, in this mode, graphics
commands are executed immediately rather than
being compiled into a display list.
immediate subclass. A subclass, of a class C,
having no super classes that are themselves
subclasses of C.
immediate subobject. One object that is a value
of an attribute of another.
immediate superclass. The superclass, of a class
C, having no subclasses that are themselves
superclasses of C.
immediate superobject. One object that contains
another among its attribute values.
IMPL. Initial microprogram load.
implementation (Or object implementation). In
SOM, the specification of what instance variables
implement an object’s state and what procedures
implement its methods (or behaviors). In DSOM, a
remote object’s implementation is also
characterized by its server implementation (a
program).
Implementation Repository. In SOM, a database
used by DSOM to store the implementation
definitions of DSOM servers.
implementation statement. An optional
declaration within the body of the interface
definition of a class in a SOM IDL source file,
specifying information about how the class will be
implemented (such as, version numbers for the
class, overriding of inherited methods, or type of
method resolution to be supported by particular
methods). This statement is a SOM–unique
statement; thus, it must be preceded by the term
1-70
Glossary
”#ifdef __SOMIDL__” and followed by ”#endif”. See
also interface declaration.
implementation template. In SOM, a template file
containing stub procedures for methods that a
class introduces or overrides. The implementation
template is one of the binding files generated by
the SOM Compiler when it processes the IDL
source file containing class interface declarations.
The class implementor then customizes the
implementation, by adding language–specific code
to the method procedures.
implicit method parameter. In SOM, a method
parameter that is not included in the IDL interface
specification of a method, but which is a parameter
of the method’s procedure and which is required
when the method is invoked from a client program.
Implicit parameters include the required
Environment parameter indicating where exception
information can be returned, as well as a Context
parameter, if needed.
implicit type conversion. A type conversion
generated by the compiler as the result of an
association between variables of different types.
For example, initializing a floating–point array to
the value of a loop counter is an implicit type
conversion from integer to floating–point.
implied DO. In FORTRAN, an indexing
specification with a list of data elements, rather
than a set of statements, as its range. Similar to an
FORTRAN DO statement, however, without using
the word DO.
import. (1.) In NCS, to request the operations
defined by an interface. A client imports an
interface from a server. (2.) To bring data in from
another system. Contrast with export.
imports. In Ada language, all compilation units
named in the context specification of a library unit
(stated in its with clauses) and any supporting unit
specifications introduced by the compiler, for
example, the standard package SYSTEM. The
imports of a secondary unit are all the units named
in its context specification, any supporting unit
requirements introduced by the compiler; its
associated parent unit (if any), and the bodies of
any generic specifications included among its other
imports.
in. See inch.
inaccessible. In XOM, said of an object for which
the client does not possess a valid designator or
handle.
inactive. Describes a window that does not have
the input focus.
Inbox. In CDE, the main or default Mailer
container. The Inbox receives all incoming mail.
Messages can be moved out of the Inbox and put
in various containers.
inch (in). 2.54 centimeters or 25.4 millimeters.
include file. A text file that contains declarations
used by a group of functions, programs, or users.
Synonymous with header file. See also include
statement.
include statement. A computer language
preprocessor statement that directs the processor
to retrieve a specific file that contains instructions
and data the program may need. See also include
file.
index priority. Priority of an attribute type in
search queries.
indexed application widget. Any widget named in
the User Interface Language (UIL) that is not the
child of any other widget in the User Interface
Definition (UID) hierarchy.
indexed component. In Ada language, an indexed
component denotes a component in an array. It is a
form of name containing expressions which specify
the values of the indices of the array component.
An indexed component may also denote an entry in
a family of entries.
indexed fields. An area in a structured data file
that contains tree data paths.
incoming call. In X.25 communications, a call
arriving at the data terminal equipment (DTE).
indexed instruction. An instruction that uses an
indexed address.
incoming–call packet. In X.25 communications, a
call supervision packet transmitted by a DCE to
inform a DTE of a call requested by another DTE.
See also packet.
indicator. (1.) An internal switch that
communicates a condition between parts of a
program or procedure. (2.) A device that can be set
to a prescribed state, usually according to the
result of a previous process or on the occurrence
of a specified condition in the equipment. The
device usually indicates the existence of the state
and may be used to determine the selection among
alternative processes.
incomplete class declaration. A C++ class
declaration that does not define any members of a
class. Until a class is fully declared, or defined, you
can only use the class name where the size of the
class is not required. Typically, an incomplete class
declaration is used as a forward declaration.
incremental backup. The process of copying files
that have been opened for reasons other than
read–only access since the last backup was
created and that meet the backup frequency
criteria. Contrast with full backup.
incremental update. In SOM, a revision to an
implementation template file that results from
reprocessing of the IDL source file by the SOM
Compiler. The updated implementation file will
contain new stub procedures, added comments,
and revised method prototypes reflecting changes
made to the method definitions in the IDL
specification. Importantly, these updates do not
disturb existing code that the class implementor
has defined for the prior method procedures.
index. (1.) A table containing the key value and
location of each record in an indexed file. (2.) A
computer storage position or register whose
contents identify a particular element in a set of
elements. (3.) A list of the contents of a file or a
document, together with keys or references for
locating the contents. See also base register.
index constraint. In Ada language, an index
constraint for an array type specifies the lower and
upper bounds for each index range of the array
type.
indirect block. A block containing pointers to other
blocks.
industry–standard benchmark. A benchmark that
has been adopted by consensus or by some
(presumably neutral) sponsoring organization as
constituting a meaningful measure of some aspect
of computer–system performance. There are many
counter–examples to the assumption that an
improvement in industry–standard benchmark
performance corresponds to an improvement in the
performance experienced by users.
inferiors. In Enhanced X-Windows, all the
subwindows nested below a window.
infinity. (1.) A name for the upper boundary of the
set of numbers. (2.) In binary floating–point
concepts, a value with an associated sign that is
mathematically greater in magnitude than any
binary floating point number.
information field overflow (I–field overflow).
Condition that occurs when the size of the
information field in the receive data exceeds the
primary station’s buffer capacity. Some of the
information field is lost.
informational message. (1.) A message that
provides information to the operator but does not
Glossary
1-71
require a response. (2.) A message that is not the
result of an error condition.
inherit. To copy resources or attributes from a
parent to a child.
inheritance. (1.) In AIXwindows and Enhanced
X–Windows, the passing of class resources from
an object superclass downstream in the class
hierarchy to an object subclass. (2.) An
object–oriented programming technique that allows
you to use existing classes as bases for creating
other classes. (3.) In SOM, the technique of
defining one class (called a subclass, derived
class, or child class) as incremental differences
from another class (called the parent class, base
class, superclass, or ancestor class). From its
parents, the subclass inherits variables and
methods for its instances. The subclass can also
provide additional instance variables and methods.
Furthermore, the subclass can provide new
procedures for implementing inherited methods.
The subclass is then said to override the parent
class’s methods. An overriding method procedure
can elect to call the parent class’s method
procedure. Such a call is known as a parent
method call. See also subclassing.
inheritance hierarchy. In SOM, the sequential
relationship from a root class to a subclass,
through which the subclass inherits instance
methods, attributes, and instance variables from all
of its ancestors, either directly or indirectly. The
root class of all SOM classes is SOMobject.
initial program load (IPL). (1.) The initialization
procedure that causes an operating system to
commence operation. Synonymous with system
restart and system startup. (2.) The process by
which a configuration image is loaded into storage
at the beginning or a work day or after a system
malfunction. (3.) The process of loading system
programs and preparing a system to run jobs.
initial program load device (IPL device). The
input/output device, usually a fixed disk or diskette,
from which the system software is loaded when the
machine is turned on.
initial sequence controller. One of three control
programs for the initial program load (IPL) ROM.
The initial sequence controller accepts control after
the hardware initialization and passes control to the
core sequence controller.
initialize. (1.) In programming languages, to set
the starting value of a data object. (2.) To set
counters, switches, addresses, or contents of
storage to zero or other starting values at the
beginning of, or at prescribed points in, the
operation of a computer routine. (3.) To prepare for
use, such as initializing a diskette. (4.) To prepare
1-72
Glossary
the system for operation. After loading the kernel
into memory, the system runs internal checks,
initializes all memory and some devices, and
analyzes the root file system.
initializer. The assignment operator followed by an
expression or multiple expressions for aggregate
variables.
inline. See inline component.
inline component. A component within a
component that has its own properties and can
contain anything a component contains. It is
created from the same set of masters as a
component.
inline expansion. An optimization in which the
reference to a procedure is replaced with the code
of the procedure itself, to eliminate calling
overhead.
inline function. In C++, inlining is a hint to the
compiler to perform inline expansion of the body of
a function member. Functions declared and defined
simultaneously in a class definition are inline. You
can also explicitly declare a function inline by using
the keyword inline. Both member and nonmember
functions can be inlined.
inlining. See inline expansion.
i–node. The internal structure that describes the
individual files in the operating system; there is one
i–node for each file. An i–node contains the node,
type, owner, and location of a file. A table of
i–nodes is stored near the beginning of a file
system. Synonym for file index. See also i–list and
i–node number.
i–node number. A number specifying a particular
i–node file in the file system. See also i–node.
inodetab. A kernel parameter that establishes a
table in memory for storing copies of i–nodes for all
active files.
input. (1.) Data to be processed. (2.) In Pascal, a
predefined standard file definition.
input data type. The type of data contained in the
input file. Examples are ASCII and PostScript.
input device. (1.) A physical device that provides
data to a computer. (2.) The device that is the
source of the software you are installing. The input
device can be a tape drive, CD–ROM drive,
diskette drive, or a directory.
input field. (1.) An area in a display file into which
you can type data. (2.) In computer graphics, an
unprotected field on a display surface in which data
can be entered, modified, or erased.
input file. A file opened in order to allow records to
be read.
input focus. In a graphics environment, a window
defining the scope for processing keyboard input.
By default, keyboard events are sent to the client
using the window the pointer is in. It is also
possible to attach the keyboard input to a specific
window. Events are then sent to the appropriate
client regardless of the pointer position.
Synonymous with focus window. See also inactive.
input list. A list of variables to which values are
assigned from input data.
input manager. In a graphics environment, a client
that controls keyboard input and is usually part of a
window manager.
input mode. An open mode in which records can
be read from the file.
Input Only window. In a graphics environment, an
invisible window that can be used to control such
things as cursors, input event generation, and
grabbing. This window cannot be used for graphics
requests.
input redirection. The specification of an input
source other than the standard one.
input semantics. The specified order and format
in which user input must be entered.
input stream. The sequence of operation control
statements and data given to the system from an
input device.
input/output (I/O). (1.) Pertaining to either input,
output, or both between a computer and a device.
(2.) Pertaining to a device whose parts can perform
an input process and an output process at the
same time. (3.) Pertaining to a functional unit or
channel involved in an input process, an output
process, or both, concurrently or not, and to the
data involved in such a process.
input/output channel (IO channel). (1.) In a data
processing system, a functional unit that handles
transfer of data between internal and peripheral
equipment. (2.) In a computing system, a functional
unit, controlled by a processor, that handles
transfer of data between processor storage and
local peripheral devices.
input/output channel controller (IOCC). A
hardware component that supervises
communication between the input/output bus and
the processor.
input/output configuration data set (IOCDS). A
configuration definition built by the I/O configuration
program (IOCP) and stored on disk files associated
with the processor controller.
input/output configuration program (IOCP). The
program that defines the I/O configuration data
required by the processor complex to control I/O
requests.
input/output device number. A value assigned to
a device driver by the guest operating system or to
the virtual device by the virtual resource manager.
This number uniquely identifies the device
regardless of whether it is real or virtual.
input/output file. A file opened for input and
output use.
input/output subsystem. That part of the
operating system comprised of processes and
device managers that provides the mechanisms for
data transfer and I/O device management and
control.
InputOutput window. In a graphics environment,
a kind of opaque window used for input and output.
InputOutput windows can have both InputOutput
and InputOnly windows as inferiors.
inquiry. (1.) A request for information in storage.
(2.) A request that puts a display station into inquiry
mode. (3.) In data communications, a request for
information from another system.
insert cursor. The position of the cursor marking
where new characters will be added when entering
text.
insert mode. (1.) A keyboard operation that puts
new text within existing text at the cursor position.
(2.) The source entry utility operation during which
source statements are typed in and added as new
records in a source member. (3.) In the
Token–Ring Network, to make an attaching device
an active part of a ring.
insertion cursor position. The point at which text
will be inserted.
insertion point. In AIX Common Desktop
Environment, the point at which text is inserted
when you type. It usually appears as a flashing
vertical line or underline.
install. (1.) To add a program, program option, or
software program to the system in a manner such
that it is runnable and interacts properly with all
affected programs in the system. (2.) To connect a
piece of hardware to the processor. (3.) The
process of connecting used when discussing the
process of connecting something to the internal
portion of the processor.
Install Icon. In CDE, an item on a subpanel used
to install icons into the Front Panel using drag and
drop.
Glossary
1-73
installation. (1.) The procedure of adding a
program or program option to the mass storage
medium of the computer, making the program
runnable, and ensuring that the program interacts
properly with all other affected programs in the
system. (2.) The task of adding a device driver to
the system and activating the driver so that it can
be used. (3.) The task of connecting a piece of
hardware to the processor or of adding a software
program to the system.
Installation Assistant. An application used to
perform system configuration tasks.
installation image. An installation image contains
a copy of the software you are installing in backup
format, as well as copies of other files the system
needs to install the software product.
installation script. A shell script or executable file
created by the developer of an application program
to install the program. The script file must follow
specific guidelines in order to be compatible with
the program installation tools that are provided in
the operating system.
instance. (1.) A concrete realization of an abstract
object class. An instance of a widget or gadget is a
specific data structure that contains detailed
appearance and behavioral information that is used
to generate a specific graphical object on–screen
at runtime. See also widget instance and instance
record. For Ada programming, see generic unit.
(2.) An object–oriented programming term
synonymous with ”object”. An instance is a
particular instantiation of a data type. It is simply a
region of storage that contains a value or group of
values. For example, if a class box is previously
defined, two instances of a class box could be
instantiated with the declaration: box box1,
box2; (3.) In XOM, an object in the category
represented by a class.
instance method. In SOM, a method valid for an
object instance (as opposed to a class method,
which is valid for a class object). An instance
method that an object responds to is defined by its
class or inherited from an ancestor class.
instance record. A particular widget record that
contains the data objects pertaining to the identity
of any given widget as an instance. See also
record, widget record, and instance.
instance token. In SOM, a data token that
identifies the first instance variable among those
introduced by a given class. The
somGetInstanceToken method invoked on a class
object returns that class’s instance token. See also
data token.
instance variables. (Or, instance data.) In SOM,
variables declared for use within the method
1-74
Glossary
procedures of a class. An instance variable is
declared within the body of the implementation
statement in a SOM IDL source file. An instance
variable is ”private” to the class and should not be
accessed by a client program. Contrast with
attribute.
instant duration locks. Locks that behave as if
they were obtained and then immediately released.
These are commonly used when a large number of
data objects require locking, but the transaction
wishes to avoid obtaining some of the necessary
locks while waiting an unknown amount of time for
another transaction to release the other required
locks. These are primarily useful for implementing
schemes such as Jim Gray’s key–range locking
(see also his Transaction Processing: Concepts
and Techniques).
instantiate. (1.) To make an instance of; to
replicate. (2.) In object–oriented programming, to
represent a class abstraction with a concrete
instance of the class. (3.) In AIXwindows, to create
a specific concrete instance of that general class.
(4.) To create or generate a particular instance (or
object) of a data type. For example, an instance
box1 of class box could be instantiated with the
declaration: box box1;
instruction. A program statement that specifies an
operation to be performed by the computer, along
with the values or locations of operands. This
statement represents the programmer’s request to
the processor to perform a specific operation.
instruction address register (IAR). A system
control register containing the address of the next
instruction to be run. The IAR can be accessed by
way of a supervisor call in supervisor state, but
cannot be directly addressed in problem state.
Synonymous with program counter. See also
location counter.
instruction cache. A cache for providing program
instructions to the processor faster than they can
be obtained from RAM.
instruction pointer (IP). See instruction address
register.
instruction scheduling. A compiler optimization
that schedules instructions to the different
processing units of the CPU so that maximum
instruction overlap can occur.
int specifier. In C language, one of the words int,
short, short int, long, long int, unsigned,
unsigned int, unsigned short, unsigned short
int, unsigned long, or unsigned long int,which
describe the type of data a variable represents.
integer. A positive or negative whole number or
zero.
integer constant. (1.) A decimal constant
containing no decimal point. (2.) An octal or
hexadecimal constant. (3.) A string of decimal
digits containing no decimal point.
integer expression. An arithmetic expression with
only integer type values.
integer type. An arithmetic data type that consists
of integer values. In Ada language, an integer type
is a discrete type whose values represent all
integer numbers within a specific range.
integral object. In the C language, a character
object, an object having an enumeration type, or an
object having the type short, int, long, unsigned
short, unsigned int, or unsigned long.
integrity. A protection level that may be specified
in secure RPC communications that ensures that
data transferred between two principals has not
been modified in transit.
intention locks. Locks used for hierarchical
resources that permit an application to avoid
locking a large data object, such as a file of
records, when it only needs to modify a portion of
the data object, such as one record in a file.
Obtaining the intention lock on the file indicates
that some records in the file may be changing
currently, but allows access to records that are not
further locked against access.
interaction. A continuing cycle of reciprocal action
between a user and one or more software
applications through input devices (a keyboard,
mouse, file server, and so on) and output devices
(a display, printer, file server, and so on).
interactive. Pertaining to an activity that involves
requests and replies, such as between a system
user and a program or between two programs.
interactive processing. A processing method in
which each system user action causes response
from the program or the system. Contrast with
batch processing.
interface. (1.) A common boundary, but not of
internal connections. An interface can be a
hardware component to link two devices or a
portion of storage or registers accessed by two or
more computer programs. Synonymous with
command interpreter. (2.) A shared boundary
between two functional units, defined by functional
characteristics, common physical interconnection
characteristics, signal characteristics, and other
characteristics. (3.) Hardware or software, or both,
that link systems, programs, or devices. (4.)
Synonymous with shell. (5.) A set of operations.
The Network Computing Architecture specifies a
Network Interface Definition Language for defining
interfaces. (6.) In SOM, the information that a client
must know to use a class––namely, the names of
its attributes and the signatures of its methods. The
interface is described in a formal language (the
Interface Definition Language, IDL) that is
independent of the programming language used to
implement the class’s methods. See also extended
interface and limited interface.
interface declaration. (Or interface statement.) In
SOM, the statement in the IDL source file that
specifies the name of a new class and the names
of its parent class(es). The ”body” of the interface
declaration defines the signature of each new
method and any attribute(s) associated with the
class. In SOM IDL, the body may also include an
implementation statement (where instance
variables are declared or a modifier is specified, for
example to override a method). See also
implementation statement.
Interface Definition Language (IDL). In SOM, the
formal language (independent of any programming
language) by which the interface for a class of
objects is defined in a .idl file, which the SOM
Compiler then interprets to create an
implementation template file and binding files.
SOM’s Interface Definition Language is fully
compliant with standards established by the Object
Management Group’s Common Object Request
Broker Architecture (CORBA).
interface, extended. See extended interface.
interface icon. Any pictorial representation of a
selection choice appearing within an interface.
interface, limited. See limited interface.
Interface Repository (IR). The database that
SOM optionally creates to provide persistent
storage of objects representing the major elements
of interface definitions. Creation and maintenance
of the IR is based on information supplied in the
IDL source file. The SOM IR Framework supports
all interfaces described in the CORBA standard.
Interface Repository Framework. In SOM, a set
of classes that provide methods whereby executing
programs can access the persistent objects of the
Interface Repository to discover everything known
about the programming interfaces of SOM classes.
interior gateway. A gateway that communicates
only with gateways on its own autonomous system.
interlacing. A method of doubling vertical
resolution by displacing odd video frames by
one–half scan line.
Glossary
1-75
interlanguage call. In a program written in a given
language, any reference to a procedure written in a
different language.
internetwork. Any wide area network connecting
more than one network.
intermediate data type. Any of the basic data
types in terms of which the other, substantive data
types of the interface are defined.
interpreted routine. A routine that decodes
instructions written as pseudocodes and
immediately executes those instructions. See also
compile.
intermediate nodes. On the widget tree, widgets
with one or more children. See also widget tree.
interpreter. A tool that allows a program to be run
immediately, without recompiling or relinking.
intern. The procedure of defining an atom.
interprocedural analysis. The process of
inspecting referenced procedures for information
on relationships between arguments, returned
values, and global data.
internal clocking. In data communications, data
clocking provided by an adapter.
internal data definition. A description of a
variable appearing at the beginning of a block that
directs the system to allocate storage for that
variable and makes that variable accessible to the
current block.
internal data structures. The format of other data
stored internally by a program or function. Used to
perform type conversion on argument lists.
internal routine. A routine available only within the
lexical scope in which it was declared.
international character support. Synonym for
national language support.
International Standards Organization (ISO). An
international body that standardizes goods and
services. For Enhanced X–Windows, standards
relating to character sets and fonts.
Internet. (1.) A wide area network connecting
thousands of disparate networks in industry,
education, government, and research. The Internet
network uses TCP/IP as the standard for
transmitting information. (2.) Any wide area
network connecting more than one network.
Internet address. The numbering system used in
TCP/IP Internetwork communications to specify a
particular network or a particular host on that
network with which to communicate. Internet
addresses are commonly denoted in dotted
decimal form.
Internet Control Message Protocol (ICMP). A
protocol used by a gateway to communicate with a
source host, for example, to report an error in
datagram. It is an integral part of Internet Protocol
(IP).
Internet Protocol (IP). The protocol that provides
the interface from the higher level host–to–host
protocols to the local network protocols.
Addressing at this level is usually from host to host.
Internet Router. Enables an IP host to act as a
gateway for routing data between separate
networks that use a specific adapter.
1-76
Glossary
inter–process communication (IPC). (1.) Used
for programs to communicate data to each other
and to synchronize their activities. Semaphores,
signals, and internal message queues are common
methods of inter–process communication. (2.) In
Enhanced X-Windows, a communication path. See
also client.
interrupt. (1.) In data communications, to take an
action at a receiving station that causes the
sending station to end a transmission. (2.) To stop
a process temporarily. (3.) A signal sent by an I/O
device to the processor when an error has
occurred or when assistance is needed to complete
I/O. An interrupt usually suspends the running of
the program that is currently running. Contrast with
exception and signal.
interrupt–confirmation packet. In X.25
communications, a packet used to acknowledge
the receipt of an interrupt packet. See also packet.
interrupt packet. In X.25 communications, an
expedited packet that is allowed to overtake normal
data packets (which are delivered in sequence).
See also packet.
intrinsic function. In FORTRAN, a function that is
supplied with the run–time environment that
performs math, character, logical, or
bit–manipulation operations.
intrinsics. In Enhanced X-Windows, a set of
management mechanisms that provides for
constructing and interfacing between composite
widgets, their children, and other clients. Also,
intrinsics provide the ability to organize a collection
of widgets into an application.
inverse. A matrix that results from a mathematical
operation on a matrix such that the two matrices
can be multiplied together to obtain the unit matrix.
inverse transpose. The inverse of a matrix after it
has been transposed.
inverted index. An index into a bibliography
database that allows for direct access. This can be
compared to the thumb cuts of a dictionary, which
allow a user to move to the exact location of the
word being searched.
invocation stack. A list of programs linked
together as a result of programs calling other
programs within the same job. Synonymous with
program stack.
invoke. To start a command, procedure, or
program.
invoke ID. An integer used to distinguish one
(directory) operation from all other outstanding
ones.
IO. See IOU.
I/O. See input/output.
I/O channel. See input/output channel.
I/O configuration. The collection of channel paths,
control units, and I/O devices that attaches to the
processor unit.
I/O error. An error in the processing of input or
output device data.
I/O Stream Library. A C++ class library that
provides the facilities to deal with many varieties of
input and output.
IOCC. See input/output channel controller.
IOCDS. I/O configuration data set.
IOT fault. A signal (SIGIOT) that abnormally ends
a process.
IP address. An address in a network using the
Internet Protocol. It is a 32–bit integer usually
written in dotted decimal notation, where each
successive eight bits is translated to an integer and
separated from the other components using a dot.
IP socket. The port concatenated with the Internet
Protocol (IP) address.
IPC. See inter–process communication.
IPL. See initial program load.
IPL device. initial program load device.
ips. Inches per second, a measure of tape drive
speed and performance.
ISC. See initial sequence controller.
ISO. See International Standards Organization.
ISO 7776. The ISO description of
LAPB–compatible DTE data link procedures.
ISO 8208. See X.25.
isolation level. A field in the specification of an
open file descriptor (OFD) that determines the
degree to which operations performed with that
OFD are isolated from other operations using that
OFD. Operation isolation is achieved by the use of
locks obtained internally on behalf of each
operation. The value of this field determines how
locks are obtained and held on behalf of operations
performed using that OFD.
IOU (IO). Input/output unit.
ITE. In CDE, Internal Terminal Emulator. ITE allows
use of a bitmapped display as a terminal (through
command–line mode from the login screen).
IP. See Internet Protocol.
item. The data in one line of an indexed field.
Glossary
1-77
J
job number. A number assigned to a job as it
enters the system to distinguish the job from other
jobs.
Japanese Industry Standard (JIS). A standard of
coding character sets.
job queue. A list of jobs waiting to be processed
by the system.
Japanese Shift–In start delimiter. In SNA
Services, an optional feature supported by X.21
Physical Link Control.
journaled file system. The standard sequential
structure of database files used in this operating
system.
JIS. See Japanese Industry Standard.
journaling. (1) The process of recording changes
made in a physical file member in a journal. (2) The
process of recording information sequentially in a
database.
Java Language. A programming language based
on the C++ language and developed by Sun
Microsystems. Java was developed to include
methods for Internet data manipulation. Java
applications can be written once and run on any
machine having a Java Virtual Machine as part of
its operating system.
job. (1) A unit of work defined by a user to be
done by a system. The term ”job” sometimes refers
to a representation of the job, such as a set of
programs, files and control statements to the
operating system. (2) One or more related
procedures or programs grouped into a procedure,
identified by appropriate job control statements.
See also process.
1-78
Glossary
jump. In the running of a computer program, a
departure from the implicit or declared order in
which instructions are being run.
jumper. A connection on an adapter that changes
the operating characteristics of a device. For
example, it could set up the I/O address or interrupt
type of a port.
justify. To print a document with even right and left
margins.
K
kanji. A graphic character set consisting of
symbols used in Japanese ideographic alphabets.
katakana. A character set of symbols, used
primarily to write foreign words phonetically,
contained in one of the two common Japanese
phonetic alphabets.
Kb. Kilobit.
KB. Kilobyte.
K–byte. See kilobyte.
kernel. (1.) The part of an operating system that
contains programs for such tasks as input/output,
management and control of hardware, and the
scheduling of user tasks. (2.) The part of the Base
Operating System containing functions needed
frequently.
kernel device driver. See device head.
kernel dump. Synonym for system dump.
kernel mode. The state in which a process runs
kernel code. Contrast with user mode.
kernel parameters. Variables that specify how the
kernel allocates certain system resources.
Synonymous with system parameters.
kerning. The placement of characters such that
their bounding boxes (character boxes) overlap.
This allows for a more natural–looking spacing
between characters.
key. (1.) One or more characters used to identify a
record and establish the record’s order within an
indexed file. (2.) A unique identifier (of type key_t)
that names the particular interprocess
communications member. (3.) Identifies the name
of the shared library text image. (4.) An identifier
within a set of data elements. (5.) A character
string that matches a definition in a key table.
key click. See keyboard click.
key grabbing. In Enhanced X-Windows, keys on
the keyboard can be passively grabbed by a client.
Or the keyboard can be actively grabbed by the
client when a key is pressed. See also grab, button
grabbing, pointer grabbing, active grab and passive
grab.
key pad. A physical grouping of keys on a
keyboard such as the numeric key pad and the
cursor key pad.
bound the records to be selected, or by specifying
an individual key value for which all matching
records should be selected in a non–unique index.
keyboard. An input device consisting of various
keys that allows the user to input data, control
cursor and pointer locations, and to control the
dialog with the workstation.
keyboard click (key click). Transient pulses or
surges on a transmission line set up by the opening
or closing of keying circuit contacts.
keyboard grabbing. In Enhanced X-Windows, a
client can actively grab control of the keyboard and
key events will be sent to that client rather than the
client to which the events would normally have
been sent.
keyboard mapping. A list, usually in a profile, that
establishes a correspondence between each key
on the keyboard and the character displayed on a
display screen, or action taken by a program, when
that key is pressed. See also mapping.
keyboard send–receive. See keyboard
send–receive mode.
keyboard send–receive (KSR) mode. A mode in
which a graphics display emulates a standard
ASCII terminal during both input and output
functions.
keyboard traversal. An X widget resource that
allows users to move the keyboard focus and
activate user interface components using a key
sequence rather than a mouse.
keylock feature. (1.) A security feature in which a
lock and key can be used to restrict the use of the
display station. (2.) A program that restricts use of
the keyboard.
keysym. An encoding of a symbol on a keycap on
a keyboard.
keyword. (1.) A predefined word in a programming
language. A reserved word. (2.) In programming
languages, a lexical unit that characterizes some
language construct. A keyword normally has the
form of an identifier. (3.) A name or symbol that
identifies a parameter. (4.) Part of a command
operand that consists of a specific character string.
kg. See kilogram.
kill. An operating system command that stops a
process.
kill character. Character that deletes a line of
characters entered after a prompt.
key range. The two key fields signifying a range of
records to be processed sequentially. The range of
records is selected by specifying key values that
Glossary
1-79
kilobyte (K–byte). 1024 bytes in decimal notation
when referring to memory capacity; in all other
cases, it is defined as 1000.
kilogram (kg). One thousand grams; 2.2046
pounds.
kprocs. A kernel parameter that establishes the
maximum number of processes the kernel can run
simultaneously.
1-80
Glossary
KSR. See keyboard send–receive mode.
KTS. Key Telephone System. A private telephone
system requiring manual selection of outside lines.
kVA. Kilovolt–ampere, or 1000volt–amperes.
L
L1 cache. The first cache accessed when a
storage reference occurs.
L2 cache. The cache that is accessed, on certain
RISC System/6000 models, if the L1 cache lookup
results in a cache miss. Normally, the L2 cache is
larger and slower than the L1 cache, but faster
than RAM.
label. (1.) A name in the disk or diskette table of
contents that identifies a file. (2.) The field of an
instruction that assigns a symbolic name to the
location at which the instruction begins. (3.) In
programming languages, a construction naming a
statement and including an identifier. See also file
name. (4.) An identifier followed by a colon, used to
identify a statement in a program. Usually the
target of a goto or switch statement. See also
statement label.
labeled statement. (1.) A programming language
statement that contains one or more identifiers
followed by a colon and a statement. (2.) A
possibly empty statement immediately preceded by
a label.
LAN. See local area network.
leaders. An evenly spaced row of dots used in a
table of contents to guide the eye from the title to
the page number.
leaf. A page of text. See also page.
leaf delta. A set of changes to the source code
saved in the Source Code Control System (SCCS)
file.
leaf entry. A directory entry that has no
subordinates. It can be an alias entry or an object
entry.
leap seconds. An infrequent adjustment to UTC to
account for the irregularity of the earth’s rotation.
leased facility. Synonym for nonswitched line.
leaves. On a widget tree, widgets with no children.
See also widget tree.
LED. See light–emitting diodes.
left–adjust. The process of aligning lines of text at
the left margin or at a tab setting such that the
leftmost character in the line or file is in the leftmost
position.
left margin. The area on a page or screen
between the left edge and the leftmost character
position on the page or screen.
landscape display. A rectangular display wider
than it is high. See also portrait display.
length specification. A source language
specification of the number of bytes to be occupied
by a variable.
landscape left. A page orientation such that the
left side of the printed image is at the trailing edge
of the paper as it emerges from the printer.
letter. An uppercase or lowercase character from
the set A through Z.
landscape right. A page orientation such that the
right side of the printed image is at the trailing edge
of the paper as it emerges from the printer.
level. (1.) The version of a software application
program. (2.) See also higher layer. (3.) In X.25
communications, see also physical level, packet
level, and frame level.
LAP. See link–access procedures.
level 1. Synonym for physical level.
LAPB. Link–access procedure balanced. See also
link–access procedures.
level 2. Synonym for frame level.
last line mode. A command mode in the vi editor.
Enables the user to enter a command at the
bottom of the screen. See also text input mode.
level 3. Synonym for packet level.
lexical analyzer. A program that analyzes input
and breaks it into categories, such as numbers,
letters, or operators.
latency. The time from the initiation of an operation
until something actually starts happening (for
example, data transmission begins).
lexical element. In Ada language, an identifier, a
literal, a delimiter, or a comment.
layout. The arrangement of printed matter on the
page, including margins, line spacing, type
specification, header and footer information,
indents, and more. Synonymous with geometry.
lexical level. The depth to which routines are
nested within one another, which determines the
scope of the identifiers declared within those
routines.
lb. See pound.
lexical scope. The portion of a program or
segment unit in which a declaration applies. An
identifier declared in a routine is known within that
routine and within all nested routines. If a nested
LC. See link control.
LCN. See logical channel number.
Glossary
1-81
routine declares an item with the same name, the
outer item is not available in the nested routine.
license password. A string encoded with license
information for a software product.
library. (1.) A collection of functions, calls,
subroutines, or other data. (2.) A data file that
contains copies of a number of individual files and
control information that allows them to be accessed
individually. (3.) In Ada–language library
management, a database that stores the various
intermediate code files produced by the compiler
and records the dependency and order of
compilation information as required by the Ada
language specification. When compiling a unit that
depends on other (previously compiled) units, the
required dependency information (such as the
package specification of a unit that is included with
a with clause) is obtained from the library.
Similarly, when an Ada program unit is to be linked,
the library specifies the set of units that must be
included to create an executable image.
license server daemon. A software program that
administers licenses for software products, invoked
with the command netlsd. The netlsd command
can be found in the /usr/lib/netls/bin directory.
library component. In Ada language, a package
body, package specification, subprogram body,
subprogram specification, object form module, or
linked object module that resides in a library.
library list file. In Ada language, a text file
containing the name of one or more sublibraries
comprising an Ada program library.
library unit. In Ada language, one of five syntactic
entities: a subprogram declaration, a package
declaration, a generic declaration, a generic
instantiation, or a subprogram body in the case
where there is no corresponding subprogram
declaration. As the name implies, a library unit
resides in the Ada program library. The significance
of library units is that they may be referenced by
other independently compiled units. This reference
may either be explicit (referenced via a with
clause) or implicit (such as the reference of a
package body to its specification).
license. An instance of permission to use a
licensed software product or service. Sometimes, a
user needs more than one license to use a
product.
licensed product. A software product that has
been enabled by a software vendor for use with the
License Use Management system. Enablement
allows a vendor to enforce end–user compliance to
their license agreement.
License Use Management. A run–time
license–management application based on
Gradient Technologies’ Version 2.0.1 (Version
1.1.2a) of the Network Licensing System. The
system allows software vendors to bundle
compliance mechanisms with their software. In
tracking license usage, License Use Management
allows customers to easily comply with their
software license agreements.
License Use Management Test Product. The
product used by the ls_tv tool to verify that license
servers are working properly.
licensed program (LP). (1.) A software program
that remains the property of the manufacturer, for
which customers pay a license fee. (2.) A
separately priced program and its associated
materials that bear a copyright and are offered to
customers under the terms and conditions of a
licensing agreement.
lifetime analysis. The process of inspecting
references to variables to determine whether the
final assignment to a variable needs to be stored or
can be discarded.
ligature. Two (or occasionally more) characters
printed together so they are connected.
light–emitting diodes (LED). A semiconductor
chip that gives off visible or infrared light when
activated. An LED is often used to display operator
information.
license annotation. A special data string that
modifies the use of a license in a manner defined
by the vendor of the software product.
lighted programmable function keyboard
(LPFK). An input device used primarily in graphic
applications and that has lighted keys under control
of an application program.
license database. The database of licenses
maintained by a license server. The license
database file–lic_db–resides in the
/usr/lib/netls/conf directory.
limited interface. A set of system calls that
provides a limited function interface. See also
interface and extended interface.
license information. The information that
describes licenses. This information consists of the
product name, the product version, the number of
licenses, the license type, the start and end dates
of the licenses, the target type, the target ID, and a
time stamp.
1-82
Glossary
limited subset. A small part or simpler version of a
larger set of data or programs.
limited type. In Ada language, a type for which
neither assignment nor the predefined comparison
for equality is implicitly declared. All task types are
limited. A private type can be defined to be limited.
An equality operator can be explicitly declared for a
limited type.
linefeed. An ASCII character that causes an output
device to move forward one line.
line. (1.) A horizontal display on a screen. (2.) The
part of a data circuit that connects to data
circuit–terminating equipment (DCE), or to data
switching exchange (DSE), or that connects
several DCEs or DSEs. (3.) A string of characters
accepted by a system as a single block of input
from a workstation, such as all characters entered
before a carriage return. (4.) See X.25 line.
linestyle. The pattern used to draw a line. A
linestyle might be solid or broken into a pattern of
dashes.
line adapter. A functional unit that converts the
serial–by–bit input to a station. See also
communications line adapter.
line discipline. The asynchronous
communications user interface for a TTY, which
includes the POSIX and Berkeley line disciplines
as well as the compatibility mode of Version 2 of
the AIX operating system.
line editor. An editor that displays data one line at
a time and that allows data to be accessed and
modified only by entering commands.
line height. The vertical measurement of a line of
text, measured from the bottom of one line to the
bottom of the next line. Line height is usually
expressed in points.
line number. For the Ada–language debugger, a
line relative to the Ada compilation that contains
the specified compilation unit.
line of memory. The section of memory that
corresponds to a cache line, which corresponds to
a single virtual–memory address tag.
line pacing. The sending of a line followed by a
waiting interval before continuing transmission. See
also pacing.
line printer. A printer that prints output, one line of
characters at a time, as a unit. Output of line
printers is in constant–width characters.
line speed. (1.) The rate at which data is
transmitted from one point to another over a
telecommunication line. (2.) The number of binary
digits that can be sent over a telecommunication
line in one second, expressed in bits per second
(bps). Synonym for speed.
line switching. Synonym for circuit switching.
linear interpolation. A method of approximating
data values by assuming that they lie along a
straight line. Typically, the two end data points are
known. For example, if A is the value at a, and B is
the value at b, and a<t<b, then the value C at t is
(from the two–point formula): B – A divided by b –
a, multiplied by t – D, added to A.
linewidth. The width of a line in pixels.
link. (1.) In the file system, a connection between
an i–node and one or more file names associated
with it. (2.) In data communications, a transmission
medium and data link control component that
together transmit data between adjacent nodes.
(3.) In programming, the part of a program that
passes control and parameters between separate
portions of the computer program. (4.) To
interconnect items of data or portions of one or
more computer programs, such as linking object
programs by a linkage editor or linking data items
by pointers. (5.) See X.25 link. (6.) See hypertext
link.
link–access procedures (LAP or LAPB). In X.25
communications, the link level elements used for
data interchange between a DCE and a DTE
operating in user classes of service 8 to 11, as
specified in CCITT Recommendation X.1. LAPB is
a duplex, asynchronous, symmetric protocol, used
in point–to–point communication. See also LAPB.
link address. An address assigned at initialization
that identifies a channel or control unit and allows it
to send and receive frames and perform I/O
operations. A set of computers sharing a network
that does not include bridges of wide area network
links.
link anchor. The reference point giving the
location of a particular link.
link control (LC). See logical link control.
link descriptor. In ODM, a named variable of type
link used to define a relationship between an
object in an object class and an object in another
object class. See also descriptor.
link–editing. To create a loadable computer
program by means of a linkage editor.
link level. See frame level.
link station. The part of data link control that is
responsible for the transfer of data on a single
logical link.
link target. See target.
link trace. A sequential log of events that occur on
the link. This log can help determine the source of
a recurring error.
Glossary
1-83
linkable. The state of an Ada–language program
when all its compilation–unit dependencies have
been resolved. To produce an executable file, the
compiler does not need to do any translation of
Ada source; it only needs to call the linkage editor.
linkage editor. A program that resolves
cross–references between separately compiled
object modules and then assigns final addresses to
create a single relocatable load module. If a single
object module is linked, the linkage editor simply
makes it relocatable.
linker. See linkage editor.
LIS. Logical IP Subnet. An LIS is comprised of
some number of ATM stations. LISs are analogous
to traditional LAN segments.
LISP. A programming language designed for list
processing and used extensively for artificial
intelligence problems.
LISP code. Program instructions written in the
LISP programming language.
LISP mode. For text editors, a mode in which
symbols used in the LISP programming language,
such as ( (left parenthesis) and ]] (double right
bracket), are treated as symbols, not as editor
commands.
list. (1.) A data object consisting of a collection of
related records. (2.) An ordered set of data.
list–directed. In FORTRAN, an input/output
specification that uses a data list instead of a
FORMAT specification.
list–directed data. In FORTRAN, data that is
transferred between main storage and an I/O
device according to the length and type of variables
in the I/O list. See also formatted data.
list fields. See indexed fields.
listen. In the X.25 API, to be prepared to receive
incoming calls that satisfy criteria specified in an
entry in the routing list, through a specified X.25
port.
listen identifier. In the X.25 API, an identifier used
to listen for and receive an incoming call.
numeric literal, an enumeration literal, a character
literal, or a string literal.
literal string. A string that does not contain
pattern–matching characters and can therefore be
interpreted just as it is. Contrast with regular
expression.
little endian. An attribute of data representation
that reflects how multi–octet data are stored in
memory. In little endian representation, the lowest
addressed octet of a multi–octet data item is the
least significant. See also endian and big endian.
little endian order. The method of storage in
which integer values are stored least significant
byte first. See also big endian order.
LLB. See Local Location Broker.
llbd. The local location broker daemon.
LLC. See logical link control.
LMS. Line monitoring system.
LNS. See LU network services component.
load. (1.) To transfer programs or data from
storage into an area of memory where the program
can be run or where the data can be manipulated.
(2.) To place a diskette into a diskette drive. (3.) To
insert paper into a printer. See also call.
load level. The balance of work between
processing units, channels, or devices.
load module. See run file.
load–store bound. Where the delay in a series of
computations is caused by the amount of data that
must be loaded into registers or stored back into
memory.
loader. A program that reads run files into main
storage so that the files can be run.
local. (1.) Pertaining to a device, file, or system
that is accessed directly from your system, without
the use of a communications line. Contrast with
remote. (2.) Pertaining to information that is
defined and used only in one subdivision of a
computer program.
listening. Programs waiting for network
communication on a given socket are listening on
that socket. See also socket and port.
local address. The address specified for the
current network or host. The local address is
usually referred to as the local host address or the
local network address to differentiate the two types.
literal. (1.) A symbol or a quantity in a source
program that is itself data, rather than a reference
to data. (2.) In programming languages, a unit that
directly represents a value. For example, 14
represents the integer 14. (3.) In Ada language, a
literal represents a value literally, that is, by means
of letters and other characters. A literal is either a
local area network (LAN). (1.) A network in which
communications are limited to a moderate–sized
geographic area (1 to 10 km) such as a single
office building, warehouse, or campus. A local
network services a facility without the use of
common carrier facilities, although they may be
interconnected using common carriers. A local
1-84
Glossary
network depends upon a communications medium
capable of moderate to high data rate (1 to 20 M
bytes per second), and normally operates with a
consistently low error rate. (2.) A data network in
which serial transmission is used for direct data
communication among data stations.
local cell. The cell to which the local machine
belongs. See also foreign cell.
local echo. On a communications workstation, a
situation in which each signal is displayed twice,
once when entered at the local workstation and
again when returned over the communications link.
local host. In TCP/IP, the host on the network at
which a particular operator is working.
Synonymous with current host.
local listen. A link station at the local node that is
waiting for an incoming call from a remote station.
Local Location Broker (LLB). (1.) Part of the
NCS Location Broker. A server that maintains
information about objects on the local host. The
LLB also provides the Location Broker forwarding
facility. (2.) A service that provides an interface to
the global location broker from the License Use
Management server. The LLB daemon (llbd) has
no information about network–wide services. It runs
continuously in the background to intercept and
forward information to the glbd. See also Location
Broker and Location Broker Client Agent.
local name. A name that is meaningful and usable
only from within the cell where the entry exists. The
local name is a shortened form of a global name.
Local names begin with the prefix /.: and do not
contain a cell name.
local pacing. Pacing generated by the local
system in an attempt to control the output from the
remote system that is input to the local system.
See also pacing.
local scope. A name declared in a block has local
scope and can only be used in that block.
local storage. A device accessed directly (without
telecommunications) from the user’s system,
where information can be retained and later
retrieved.
locality of reference. The degree to which a
running program makes use of a compact range of
addresses for instructions and/or data.
Location Broker. In NCS, a set of software
including the Local Location Broker, the Global
Location Broker, and the Location Broker Client
Agent. The Location Broker maintains information
about the locations of objects. See also broker,
Local Location Broker, and Location Broker Client
Agent.
Location Broker Client Agent. Part of the NCS
Location Broker. Programs communicate with
Global Location Brokers and with remote Local
Location Brokers using the Location Broker Client
Agent. See also Local Location Broker and
Location Broker.
location code. A path from the adapter in the
processor through the signal cables and fan out
box, if there is one, to the device or workstation.
The code consists of four fields of information:
Drawer, Slot, Connector, and Port.
location counter. A counter in the assembler that
denotes the next byte available for code allocation.
The location counter assigns storage addresses to
program statements. See also instruction address
register.
locator. In computer graphics, an input device that
provides coordinate data; for example, a mouse,
tablet, or thumb wheel.
locator resolution. The density of points on a
locator device.
locator sample rate. The rate of input from a
locator device. Synonymous with sample rate.
lock. A mechanism with which a resource is
restricted for use by the holder of the lock. See also
record lock.
LOCK. See Lock Service.
Lock button. In CDE, a Front Panel control used
to lock the screen.
lock file. In multiprocess applications, a system file
on disk that the sharing processes use to control
their access to shared data or devices.
local variable. A symbol defined in one program
module or procedure that can only be used within
that program module or procedure.
Lock Service (LOCK). The component of Encina
Base that enables transactions to lock resources
before accessing or modifying them.
locale. A subset of a user’s environment that
defines conventions for a specified culture, such as
time formatting, numeric formatting, monetary
formatting, and character classification, conversion,
and collation.
log. (1.) To record. For example, to record all
messages on the system printer. (2.) A list of
messages, such as an error log. (3.) A collection of
messages or message segments placed in an
Glossary
1-85
auxiliary storage device for accounting or data
collections purposes.
log file. (1.) The text file that records messages
and errors from the license server, and sometimes
from licensed products, which resides in the
/usr/lib/netls/conf directory. (2.) In Ada language,
a file that contains a record of your commands and
comments and the debugger’s responses. This log
can be used for later analysis, for documenting
program behavior, or for making comparisons after
program modification.
log force. An action that causes all pending log
records to be written to permanent storage. A log
force is usually associated with committing a
transaction, and ensures that the log records
associated with that transaction are actually
present in the log. Until a log force is done, these
records might only be stored in memory and might,
therefore, be vulnerable to system failures.
log force groups. A logical association of the log
records associated with different processes.
Grouping the log records associated with all
processes spawned by a specific transaction
provides a convenient way to ensure that all of the
log records associated with any processes acting
on behalf of a specific transaction can be referred
to with a single expression or operation.
log in. (1.) To begin a session at a display station.
(2.) The act of gaining access to a computer
system by entering identification and authentication
information at the workstation.
log off. To end a session with a computer system
at a display station.
log on. See log in.
log out. See log off.
log record. A predefined structure into which the
log data is formatted. Records have a specific size
and format, and contain a certain set of related
information. A log record can be identified by its log
sequence number (LSN).
logger. (1.) A functional unit that records events
and physical conditions, usually with respect to
time. (2.) A program that enables a user entity to
log in (for example, identify itself, its purpose, and
time of entry) and log off with the corresponding
data. This enables the appropriate accounting
procedures to be carried out in accordance with the
operating system.
logical channel. In X.25 communications, a
means of two–way simultaneous transmissions
across a data link, comprising associated send and
receive channels. A logical channel can represent
the path that data travels from its origin to the
network or from the network to its destination. See
also channel.
logical channel number (LCN). An umber that
uniquely identifies a logical channel.
logical constant. A constant with a value of true or
false.
logical device. (1.) A file for conducting input or
output with a physical device. (2.) A file for
mapping user I/O between virtual and real devices.
logical expression. An expression consisting of
logical operators, relational operators, or both that
can be evaluated to a value of either true or false.
logical link. The logical connection between an
application on the S/370 and an application on the
workstation.
logical link control (LLC). In a local area network,
the protocol that governs the assembling of
transmission frames and their exchange between
data stations, independently of the medium access
control protocol. See also medium access control.
logical name. A name assigned to a device that
distinguishes it from all other device instances in
the system. It is the name used to refer to a
particular device. For example, ”tok0” can refer to a
token–ring adapter. This is the same as ”device
name,” which is a field in the Customized Devices
Object Class. See also device name.
log volume. An abstract representation of disk
space that is used for storage by the Encina log
server. There are two types of log volumes:
permanent and archival. Permanent volumes can
be stored on file or disk devices. Archival volumes
can only be stored on file devices. Internal log
server data and log file groups must be stored on
permanent volumes. Log archive groups must be
stored on archival volumes. See also volume,
logical volume, and physical volume.
logical network. A subnetwork of machines set up
to function as a whole and separate network. A
logical network usually functions as a subnetwork
of a larger physical network.
logarithm. A mathematical operation related to the
base of a numbering system.
logical partition (LP). (1.) One to three physical
partitions (copies). The number of logical partitions
1-86
Glossary
logical operation. An operation that follows the
rules of Boolean logic.
logical operator. A symbol that represents an
operation, such as AND, OR, or NOT, on logical
expressions.
within a logical volume is variable. (2.) A fixed–size
portion of a logical volume. A logical partition is the
same size as the physical partitions in its volume
group. Unless the logical volume of which it is a
part is mirrored, each logical partition corresponds
to, and its contents are stored on, a single physical
partition. See also logical volume.
logical primary. A primary that can have a value of
true or false.
logical resource. A software construct, such as a
lock or a buffer, that is required for the execution of
a program and is in limited supply.
logical storage. A conceptual storage layout in
which an application maps first into logical
addresses, which are then mapped into real
addresses by control blocks.
logical type. A data type that contains the values
of true and false.
logical unit (LU). (1.) A type of network
addressable unit that enables end users to
communicate with each other and gain access to
network resources. (2.) In SNA, a port through
which an end user accesses the SNA network to
communicate with another user, and through which
the end user accesses the functions provided by
system services control points (SSCPs). An LU can
support at least two sessions, one with an SSCP
and one with another LU, and may be capable of
supporting many sessions with other LUs.
Logical Unit Type 1 (LU1). An SNA session that
supports communication between an application
and multiple input/output devices. This
communication could occur in an interactive or
batch environment.
Logical Unit Type 2 (LU2). An SNA session that
uses a 3270 device data stream to support
communication between an application and a
display.
Logical Unit Type 3 (LU3). An SNA session that
uses a 3270 device data stream to support
communication between an application and a
printer.
Logical Unit Type 6.2 (LU6.2). (1.) An SNA
session between two applications in a distributed
data processing environment. (2.) The LU type
used for SNA advanced program–to–program
communications (APPC). See also peer–to–peer
communications.
logical volume (LV). (1.) A collection of physical
partitions organized into logical partitions all
contained in a single volume group. Logical
volumes are expandable and can span several
physical volumes in a volume group. (2.) A set of
logical partitions, each of which is stored on one or
more physical partitions from one or more of the
physical volumes of a given volume group. A
logical volume has a device name (of the form
/dev/hdn) and contains a single file system. See
also log volume, migration installation, logical
partition, and volume group.
Logical Volume Manager (LVM). Manages disk
space at a logical level. It controls fixed–disk
resources by mapping data between logical and
physical storage and by allowing data to span
multiple disks and to be discontiguous, replicated,
and dynamically expanded.
login directory. The directory you access when
you first log in to the system.
login name. A string of characters that uniquely
identifies a user to the system.
login session. The period of time during which a
user of a workstation can communicate with an
interactive system, usually the elapsed time
between log in and log off.
login shell. The shell that is started when a user
logs into the computer system. The login shell for a
particular user is determined by the entry in the
/etc/passwd file for that user. See also shell.
long. (1.) In ODM, a terminal descriptor type used
to define a variable as a signed 4–byte number.
See also terminal descriptor. (2.) A signed 4–byte
number.
long constant. A 4–byte integer constant followed
by the letter ”l” or ”L.”
long queue status. Synonym for long status.
long status. A detailed, multiline status that
contains more information about each job than the
normal short status. Synonymous with long queue
status.
loop. (1.) A sequence of instructions performed
repeatedly until an ending condition is reached. (2.)
A closed unidirectional signal path connecting input
and output devices to a system.
loop collapse. In nested array–processing loops,
an optimization that collapses the nested loops into
a single loop with an iteration count that is the
product of the iteration counts of the original loops,
and that adjusts array indices appropriately.
loop defactorizing. An optimization that removes
an invariant factor from a loop that sums
calculations into a scalar. The summation scalar
can be multiplied by the factor on exit from the
loop.
loop elimination. A form of loop unrolling in which
the loop is completely unrolled, and references to
Glossary
1-87
loop index within the unrolled loop are replaced by
constant values.
loop fusion. An optimization that takes the bodies
of loops with identical iteration counts and fuses
them into a single loop.
loop nest reordering. An optimization that
changes the order of loops within a loop nest, to
achieve stride minimization or to eliminate data
dependencies.
loop overhead. The CPU time used by a loop that
cannot be attributed to computations within the
loop.
loop peeling. An optimization that improves the
performance of a loop that maps an array to a
cylindrical coordinate system.
loop rerolling. An optimization that transforms
user–unrolled loops into their original, unrolled
equivalents, so that other optimizations can be
attempted.
loop unrolling. An optimization that increases the
step of a loop, and duplicates the expressions
within a loop to reflect the increase in the step. This
can improve instruction scheduling and memory
access time.
looping statement. A statement that runs any
number of times, depending on the value of a
specified expression.
low–order. Least significant; rightmost. For
example, in a 32–bit register (0 through 31), bit 31
is the low–order bit.
LP. See licensed program.
LPFK. See lighted programmable function
keyboard.
LPM. Lines per minute. The number of lines a
printer can print in one minute.
LPR. Line Printer Server.
LQ. Letter quality.
LRU. Least recently used.
ls_admin. In License Use Management, the
software program used to modify a license server
database, invoked with the command ls_admin,
which is located in the /usr/lib/netls/bin directory.
1-88
Glossary
ls_rpt. In License Use Management, the software
program that reports on the history of license
server events, invoked with the command ls_rpt,
which is located in the /usr/lib/netls/bin directory.
ls_stat. In License Use Management, the software
program that reports on the status of licenses,
invoked with the command ls_stat, located in the
/usr/lib/netls/bin directory.
ls_tv. In License Use Management, the network
license server daemon test and verification tool,
invoked with the command ls_tv, located in the
/usr/lib/netls/bin directory.
lsb. Least significant bit
LSB. Least significant byte.
LU. See logical unit.
LU1. See Logical Unit Type 1.
LU2. See Logical Unit Type 2.
LU3. See Logical Unit Type 3.
LU6.2. See Logical Unit Type 6.2.
LU, dependent. A logical unit that cannot start a
conversation but must wait for the host system to
start the conversation.
LU, independent. A logical unit that can start a
conversation with another logical unit.
LU–LU session. In SNA Services, a session
between two logical units (LUs) of the same type
that supports communication between two end
users, or between an end user and an LU services
component.
LU network services component (LNS). Begins
and ends LU–LU sessions in response to requests
from the resource manager and from the remote
LU. It also activates and deactivates CP–LU
sessions.
lvalue. (1.) An expression that represents a data
object that can be both examined and altered. (2.)
The left–hand part of an expression.
LV. See logical volume.
LVM. See Logical Volume Manager.
M
m. See meter.
MAC. (1.) See medium access control. (2.)
Mandatory Access Control.
machine execution state. A state that indicates
the machine is shut down, booting, or running. This
state is one of two machine states.
machine instruction. (1.) A binary number that
directs the operation of a processor. Compilers and
assembler convert source instructions to machine
instructions. (2.) An instruction of a machine
language. Synonym for computer instruction and
computer language.
machine language. A language that can be used
directly by a computer without intermediate
processing. The final output of the compilation
process is a load module containing machine
language instructions. Synonym for computer
language.
machine object. An entry in the Network
Installation Management database that represents
a machine configuration.
machine state. A state that identifies the machine
execution state and control state for each machine.
machine word. Synonym for word. See also
computer language.
macro. (1.) A label that is declared at the start of a
program or file. The label can then be used to
represent the values assigned to the label in the
declaration. (2.) A name or label used in place of a
number of other names. (3.) The sequence of
instructions or statements that a macrogenerator
runs when replacing a macro instruction. (4.) A set
of statements defining the name of, format of, and
conditions for generating a sequence of assembler
statements from a single source statement. (5.) A
series of Ada–language debugger commands that
execute in sequence when you call the macro. With
the macro option, you can define and manipulate
new debugger commands. See also routine,
statement function, and subroutine.
macro call. A single instruction that, when
executed, causes the execution of a predefined
sequence of instructions in the same source
language.
macro instruction. See macro call and macro.
macro processor. A program that converts macro
instructions into specified values.
magic number. A numeric or string constant in a
file that indicates the file type.
mail. Correspondence in the form of messages
transmitted between workstations over a network.
Synonymous with electronic mail.
mail box. A storage location in a network to which
messages for a user are sent.
mail drop. The file into which messages are first
received.
Mailer. In CDE, an application that enables you to
send, receive, and compose electronic mail
messages.
mailer. The program that does the actual delivery
of mail.
mailer container. In CDE, the electronic mail box
and filing system that contains all mail messages.
Once a message is put in a container, you can
display, modify, delete, print, include, forward, and
reply to it.
Mailer control. In CDE, the Front Panel control
used to start the Mailer software application.
Dropping a file on the control loads the file into the
Mailer Compose window.
main. In FORTRAN, the default name given to a
main program if one was not supplied by the
programmer.
main function. A function that has the identifier
main. Each C language program must have
exactly one function named main. This function is
the main program of a C language program.
Main Panel. In CDE, the portion of the Front Panel
excluding the subpanels.
main program. (1.) The first program unit to
receive control when a program is run. Contrast
with subprogram. (2.) A program that performs
primary functions, passing control to routines and
subroutines for the performance of more specific
functions.
main storage. (1.) Program–addressable storage
or memory from which instructions and other data
can be loaded directly into registers for subsequent
running or processing. Synonymous with system
memory. (2.) The part of internal storage into which
instructions and other data must be loaded for
running or processing. (3.) The part of the
processing unit where programs are run.
mainframe. A large computer, particularly one to
which other computers can be connected so that
they can share facilities the mainframe provides.
The term usually refers to hardware only.
maintenance analysis procedure (MAP).
Documentation used by customer engineers and
by service representatives to repair equipment. A
Glossary
1-89
MAP contains yes/no questions and procedures
that direct the user to the failing part of the
equipment.
maintenance level update. The service updates
(fixes and enhancements) that are necessary to
upgrade the Base Operating System (BOS) or an
optional software product to the current release
level. See also service update.
maintenance mode. State in which a product or
system can be serviced. Synonymous with service
mode.
maintenance system. A special version of the
operating system that is loaded from diskette and
used to perform system management tasks.
major device number. A system identification
number for each device or type of device. The
major device, minor device, and channel numbers
uniquely identify a hardware device. See also
minor device number.
managed children. In Enhanced X-Windows,
children in which the managed field has a value of
True can have their layout (geometry) changed so
that they can be repositioned and resized.
managed window. See managed children.
manager. See device manager.
Manager class. In AIXwindows, a metaclass that
provides the resources and functionality to
implement certain features, such as a keyboard
interface and traversal mechanism. It is built from
the Core, Composite, and Constraint classes.
mangling. The encoding, during compilation, of
C++ identifiers such as function and variable
names to include type and scoping information.
The linker uses these mangled names to ensure
type–safe linkage.
format specified by the transmission programs.
Only LU6.2 sessions allow mapped conversation; it
is used primarily for application transaction
programs. Contrast with basic conversation.
mapped file. (1.) A file that can be accessed
through direct memory operations instead of being
read from disk each time it is accessed. (2.) A file
on the fixed disk that is accessed as if it is in
memory.
mapping. (1.) In Enhanced X-Windows, a window
on which a map call has been performed. Mapping
makes a window visible if there are no obscuring or
occluding windows. (2.) A list, usually in a profile,
that establishes a correspondence between items
in two groups. For example, a keyboard mapping
can establish what character is displayed when a
certain key is pressed. See also keyboard mapping
and profile.
margin. Left and right border of text on a screen or
hardcopy page.
mark block. In Pascal, a dynamic block header
that designates a subheap within a heap.
marker. (1.) A visual symbol within a
non–interactive pane indicating the location of the
cursor when the pane was last interactive. (2.) In
computer graphics, a glyph with a specified
appearance that is used to identify a particular
location.
marshal. In NCS, to copy data into a Remote
Procedure Call (RPC) packet. Stubs perform
marshalling. Contrast with unmarshal. See also
stub.
mask. (1.) A pattern of characters that controls the
keeping, deleting, or testing of portions of another
pattern of characters or bits, usually through an
AND or OR operation. (2.) To apply a mask.
manual call. In data communications, a line type
that requires the operator to place a call over a
switched line. Contrast with auto–call.
master. The only machine in the NIM environment
that has permission to remotely execute
commands on other NIM clients.
manual dialing. In making an ATE connection,
dialing the number manually over a telephone line.
master dump table. A structure containing dump
table entries generated by kernel components. The
dump program uses this table to locate data
structures that should be included in a dump.
map. See mapping.
MAP. See maintenance analysis procedure.
mapped. In Enhanced X-Windows, a window is
said to be mapped if a map call has been
performed on it.
mapped conversation. A temporary connection
between an application program and an advanced
program–to–program communication (APPC)
session in which the system provides all the
protocol information. It allows the two programs to
exchange data records of any length and in any
1-90
Glossary
master file. (1.) A collection of permanent
information, such as a customer address file. (2.) A
file that is used as an authority in a given job and
that is relatively permanent, even though its
contents may change.
master processor. The first processor started at
boot time in a multiprocessor system.
master server. In a network installation
environment, the server that has permissions to
execute commands on all other machines in the
environment. The master server is designed to
manage the network, client, and resource objects
in the network installation database.
matrix. (1.) A rectangular array of elements
arranged in rows and columns that can be
manipulated based on matrix algebra rules. (2.) In
computers, a logic network in the form of an array
of input and output leads with logic elements joined
at some of their intersections. (3.) By extension, an
array of any number of dimensions.
matrix stack. In GL, a stack of matrices with
hardware and software support. The top matrix on
the stack is the current transformation matrix, and
all points passed through the graphics pipeline are
multiplied by that matrix. It is a concatenation of the
current modeling and viewing transformations. See
also current transformation matrix.
maximum transfer unit (MTU). (1.) The maximum
number of bytes that an Internet Protocol (IP)
datagram can contain. (2.) The largest amount of
data that can be transmitted in a single frame for a
particular network interface.
Mb. Megabit.
MB. Megabyte.
M–bit. In X.25 communications, the bit in a data
packet that indicates that there is more data to
follow in another data packet (when a message is
too large for one packet).
mbuf. A small (256–byte) buffer provided by the
mbuf management facility to the various layers of
communication software in AIX.
M–byte. See megabyte.
MC. See MCU.
MCU (MC). Memory control unit.
medium access control. In a local area network,
the protocol that governs communication on the
transmission medium without concern for the
physical characteristics of the medium. However, it
takes into account the topological aspects of the
network, to enable the exchange of data between
data stations. See also logical link control.
megabyte (MB). Loosely, one million bytes. When
referring to semiconductor memory capacity, two to
the twentieth power; 1 048 576 in decimal notation.
When referring to media device storage, a
megabyte is ten to the sixth power (1 000 000).
megahertz (MHz). A unit of measure of frequency.
One megahertz equals 1 000 000 hertz.
member. (1.) A data object in a structure, a union,
or a library. (2.) Synonym for element. (3) A C++
data object or function in a structure, union or
class. Members can also be classes,
enumerations, bit fields and type names.
member function. C++ Operators and functions
that are declared as members of a class. A
member function has access to the private and
protected data members and member functions of
an object of its class. Member functions are also
called methods.
memory. (1.) Program–addressable memory from
which instructions and other data can be loaded
directly into registers for subsequent running or
processing. (2.) Memory on electronic chips.
Examples of memory are random access memory,
read–only memory, or registers. See also storage.
memory deallocation. To free up memory that has
been previously allocated for a specific purpose.
memory dump. The means by which the computer
system records its state at the time of a failure.
memory image. The logical layout of the parts of a
process in memory.
memory leak. A software bug in which the
program allocates memory, loses track of it, and
then allocates some more. If the program is
long–running, it can eventually tie up large
amounts of real memory and paging space.
System performance gradually deteriorates; the
program that finally fails due to lack of resource
may not be the culprit. Memory leaks in kernel
extensions that allocate pinned memory may be
particularly costly.
memory load control. A VMM facility, added in
AIX Version 3.2, that detects memory
over–commitment and temporarily reduces the
number of running processes, thus avoiding
thrashing.
memory over–commitment. A condition in which
the number of virtual–memory pages being used
by the currently running programs exceeds the
number of real–memory page frames available to
hold them. If the over–commitment is large or
sustained, system performance suffers.
menu. A displayed list of items from which an
operator can make a selection.
menu bar. A rectangular area at the top of the
client area of a window that contains the titles of
the standard pull–down menus for that application.
menu cursor. In AIXwindows, the cursor defined
for a particular menu. Each type of cursor is
identified by an ID number.
menu pane. The physical window containing a
pop–up menu listing a group of options to be
chosen by the user. See also pane.
Glossary
1-91
menu system. An interactive interface that lists
related software options in a manner that expedites
review and selection by the user.
message. (1.) Information from the system that
informs the user of a condition that may affect
further processing of a current program. (2.) An
error indication, or any brief information that a
program writes to standard error or a queue. (3.)
Information sent from one user in a multiuser
operating system to another. (4.) A general method
of communication between two processes. (5.) A
group of characters and control bit sequences
transferred as an entity. (6.) One or more linked
blocks of data or information, with associated
STREAMS control structures containing a message
type. Messages are the only means of
communicating within a stream.
message control block. In the X.25 API, the
structure used to indicate what type of packet has
arrived and to point to the structure that contains
the packet information.
message queue. A linked list of messages
connected to a QUEUE.
message queue ID (msqid). An identifier assigned
to a message queue for use within a particular
process. It is similar in use to a file descriptor of a
file.
message type. A defined set of values identifying
the contents of a message.
metaclass. (1.) In AIXwindows and Enhanced
X-Windows, an object class that does not
instantiate widgets or gadgets but is capable of
passing a unique set of inheritable resources to the
subclasses beneath it in the class hierarchy. Each
instance of a widget subclass has the features
common to that widget class and exports these
features to child widgets of that class. Included in
this class are Core, Composite, Constraint,
Primitive, Button, Manager, MenuMgr, and
MenuPane. (2.) In SOM, a class whose instances
are classes. In SOM, any class descended from
SOMClass is a metaclass. The methods a class
inherits from its metaclass are sometimes called
class methods (in Smalltalk) or factory methods (in
Objective–C) or constructors. See also class
method.
metaclass incompatibility. In SOM, a situation
where a subclass does not include all of the class
variables or respond to all of the class methods of
its ancestor classes. This situation can easily arise
in OOP systems that allow programmers to
explicitly specify metaclasses, but is not allowed to
occur in SOM. Instead, SOM automatically
prevents this by creating and using derived
metaclasses whenever necessary.
1-92
Glossary
metadata. The structural data associated with the
file system, such as the organization of directories,
inode tables, and links. Metadata is not data
supplied by a user; it is information about the
structure of user data.
meter (m). A linear measurement that equals
1.0936 yards, 3.2808 feet, or 39.3696 inches.
method. (1.) In Enhanced X-Windows, the
functions or procedures that a widget itself
implements. (2.) In ODM, executable code
associated with an object and defined as the value
of a method descriptor for the object. The method
can be a command, program, or shell script. See
also method descriptor. (3.) An object–oriented
programming term synonymous with member
function. (4.) In SOM, a combination of a procedure
and a name, such that many different procedures
can be associated with the same name. In
object–oriented programming, invoking a method
on an object causes the object to execute a
specific method procedure. The process of
determining which method procedure to execute
when a method is invoked on an object is called
method resolution. (The CORBA standard uses the
term ”operation” for method invocation). SOM
supports two different kinds of methods: static
methods and dynamic methods. See also static
method and dynamic method.
method descriptor. In ODM, a named variable of
type method used to define a method or operation
to associate with an object. The method can be any
executable code such as a command, program, or
shell script. See also method and descriptor.
method ID. In SOM, a number representing a
zero–terminated string by which SOM uniquely
represents a method name. See also somId.
method procedure. In SOM, a function or
procedure, written in an arbitrary programming
language, that implements a method of a class. A
method procedure is defined by the class
implementor within the implementation template file
generated by the SOM Compiler.
method prototype. In SOM, a method declaration
that includes the types of the arguments. Based on
method definitions in an IDL source file, the SOM
Compiler generates method prototypes in the
implementation template. A class implementor
uses the method prototype as a basis for writing
the corresponding method procedure code. The
method prototype also shows all arguments and
their types that are required to invoke the method
from a client program.
method resolution. In SOM, the process of
selecting a particular method procedure, given a
method name and an object instance. The process
results in selecting the particular
function/procedure that implements the abstract
method in a way appropriate for the designated
object. SOM supports a variety of
method–resolution mechanisms, including offset
method resolution, name–lookup resolution, and
dispatch–function resolution.
method table. In SOM, a table of pointers to the
method procedures that implement the methods
that an object supports. See also method token.
method token. In SOM, a value that identifies a
specific method introduced by a class. A method
token is used during method resolution to locate
the method procedure that implements the
identified method. The two basic
method–resolution procedures are somResolve
(which takes as arguments an object and a method
token, and returns a pointer to a procedure that
implements the identified method on the given
object) and somClassResolve (which takes as
arguments a class and a method token, and
returns a pointer to a procedure that implements
the identified method on an instance of the given
class). See also method table.
MHz. See megahertz.
MIB Variable. A managed object that is defined in
the Management Information Base (MIB). The
managed object is defined by a textual name and a
corresponding object identifier, a syntax, an access
mode, a status, and a description of the semantics
of the managed object. The MIB Variable contains
pertinent management information that is
accessible as defined by the access mode.
Micro Channel architecture. The I/O channel
used on the POWERstation and POWERserver
system units.
microdocument. A document within a frame that
has its own properties and shares components with
the main document.
migration installation. An installation method for
upgrading AIX Version 3.2 or later to the current
release while preserving the existing root volume
group. This method preserves the /usr, /tmp, /var,
and / (root) file systems, as well as the root volume
group, logical volumes, and system configuration
files. Migration is the default installation method for,
and can only be used on, an AIX Version 3.2 or
later machine. See also root volume group and
logical volume.
mil. A measurement of thickness: 1/1000 inch.
millisecond. A measurement of time: 1/1000 of a
second.
minimally consistent. Said of an object that
satisfies various conditions set forth in the definition
of its class.
minor device number. A number that specifies
various types of information about a particular
device. For example, a number that distinguishes
between several printers of same type. See also
major device number.
mirroring. The creation of a mirror image of a
primitive.
mixed string. A string consisting of a mixture of
DBCS characters and single–byte characters.
mm. (1.) A package of macros for manuscript
preparation that supports the eqn and troff
commands or the neqn and nroff commands and
features annotation, footnoting, indexing, and
tables by supporting the tbl command. (2.)
Millimeter.
mnemonic. (1.) A symbol chosen to help the user
remember the significance of the symbol. (2.) The
field of an assembler instruction that contains the
acronym or abbreviation for a machine instruction.
(3.) In CDE, a single, underlined character in a
command. The mnemonic indicates that you can
choose the command by typing that letter.
Mnemonics are used most commonly in menu
commands; however, other buttons may also have
mnemonics.
mnemonic overstrike. A nonstandard character
created by printing one character on top of another
to represent a nonprinting character.
modal. The state in which a secondary window
receives keyboard or pointer input that it does not
pass on to its associated window.
modal dialog. In AIXwindows, a Dialog widget
that interrupts the work session to solicit input from
the user.
modal interaction. The communication between
separate modes or functions.
modal pop–up. In Enhanced X-Windows, a
window that normally is not visible to the window
manager and available only after the manager is
turned off. This pop–up disables user–event
processing except for events that occur in the
dialog box.
mode. (1.) A method of operation. (2.) In SNA data
communications, the set of rules and protocols to
be used for a session. (3.) In the M–Video Capture
Adapter, a method of operation such as live or
overlay capture. (4.) For Ada programming, see
parameter.
Glossary
1-93
model number. In Ada language, an exactly
representable value of a real type. Operations of a
real type are defined in terms of operations on the
model numbers of the type. The properties of the
model numbers and of their operations are the
minimal properties preserved by all
implementations of the real type.
modeless dialog. In AIXwindows, a Dialog widget
that solicits input from the user but does not
interrupt the work session.
modeless pop–up. In Enhanced X-Windows, a
window that is normally visible and is controlled by
the window manager.
modeling coordinates, modeling space. In GL,
the coordinate system in which all drawing
primitives do their drawing. The user can select the
position and orientation of the modeling space with
regard to the world space by means of translations,
rotations, scales, or generalized transformations.
The relation between modeling coordinates and
world coordinates is determined by the modeling
matrix. Modeling coordinates are a useful
conceptual device when drawing complex or
repetitive scenes. For instance, a paper clip can be
defined once in modeling coordinates, and then
drawn hundreds of times by moving the modeling
coordinates around in world space. See also eye
coordinates, screen coordinates, world
coordinates, and transformation.
modem (modulator–demodulator). A device that
converts digital data from a computer to an analog
signal that can be transmitted on a
telecommunication line, and converts the analog
signal received to digital data for the computer.
modem eliminator. A device that connects a
workstation directly to a computer port through a
wired connector with a specific pin arrangement.
When two devices both function as DTEs (data
terminal equipment), the cable that connects them
must transmit send and receive signals using a
modem eliminator. Synonymous with null modem.
mode name. (1.) The name of an entry in the login
mode table. (2.) In SNA, identifies the set of rules
and protocols to be used for the session.
mode word. An i–node field that describes the
type and state of the i–node.
modification number. The modification level of a
program, which is an indicator of changes that do
not affect the external interface of the program. The
version, release, modification, and fix levels
together comprise the program level, fix number,
release number, and version number.
modifier. (1.) Word or quantifier used to change an
instruction causing the execution of an instruction
1-94
Glossary
different from the original one. Consequently, the
same instruction, successively changed by a
modifier, can be used repetitively to carry out a
different operation each time it is used. (2.) In
SOM, any of a set of statements that control how a
class, an attribute, or a method will be
implemented. Modifiers can be defined in the
implementation statement of a SOM IDL source
file. The implementation statement is a
SOM–unique extension of the CORBA
specification. [User–defined modifiers can also be
specified for use by user–written emitters or to
store information in the Interface Repository, which
can then be accessed via methods provided by the
Interface Repository Framework.]
modifier key. In CDE, a key that when pressed
and held along with another key or mouse button
changes the meaning of the second key or mouse
click. Control, Alt, and Shift are examples.
modifier keys. In Enhanced X-Windows, keys
such as Shift, Shift Lock, Control, Alt, Caps Lock,
and Meta.
modulation. Changing the frequency or size of
one signal by using the frequency or size of
another signal.
modulator–demodulator. See modem.
module. (1.) A discrete programming unit that
usually performs a specific task or set of tasks.
Modules are subroutines and calling programs that
are assembled separately, then linked to make a
complete program. (2.) In programming languages,
a language construct that consists of procedures or
data declarations and that interact with other such
constructs. (3.) A packaged functional hardware
unit designed for use with other components. (4.)
Synonym for program unit. (5.) See also run file.
(6.) Software that performs functions on messages
as they flow between stream head and driver. A
module is the STREAMS counterpart to the
commands in a shell pipeline except that a module
contains a pair of functions that allow independent
bidirectional (downstream and upstream) data flow
and processing. (7.) In SOM, the organizational
structure required within an IDL source file that
contains interface declarations for two (or more)
classes that are not a class–metaclass pair. Such
interfaces must be grouped within a module
declaration. See also object module.
MOM. See monitor mode.
mond. See monitor scheduling daemon.
monitor. (1.) A device that observes and verifies
operations of a data processing system. (2.) A
functional unit that observes and records selected
activities for analysis within a data processing
system. Possible uses are to show significant
departures from the norm or to determine levels of
utilization or particular functional units. (3.)
Synonym for display.
MS–DOS. Microsoft Disk Operating System.
monitor mode (MOM). A mode in which an
application program can directly access the display
adapter.
multibyte control. One of the two types of controls
valid in a character stream data. Synonym for
escape sequence.
monitor scheduling daemon. A process that runs
on an application server and provides clients with
links to processing agents as needed
multicast address. A multicast address, for FDDI,
is an address with the high order bit in the
high–order byte of the address set. This type of
address allows a user to have multiple stations on
a ring set to the same address. If a packet is sent
to a multicast address, all stations with that
address receive the packet. A multicast address is
sometimes referred to as a group address.
monochrome. A special case of static gray in
which there are only two color map entries. Some
monochrome adapters can display shades of gray
in the Gray Scale Adapter.
monochrome display. A display device that has
only one color. See also gray scale.
more–data bit. See M–bit.
mount. To make a file system accessible.
mouse. A hand–held locator that a user operates
by moving it on a flat surface. It allows the user to
select objects and scroll the display screen by
pressing buttons.
mouse button 1. On a mouse, the leftmost button
when configured for right–handed use; the
rightmost button when configured for left–handed
use. Mouse button 1 is primarily used for selection,
and is the default button for the ”click” instruction.
mouse button 2. On a three–button mouse, the
middle button. On a two–button mouse, the right
button if configured for right–handed use or the left
button if configured for left–handed use. Mouse
button 2 has two modes: Transfer and Adjust.
mouse button 3. On a mouse, the rightmost
button when configured for right–handed use; the
leftmost button when configured for left–handed
use. Mouse button 3 activates pop–up menus.
mouse pointer. A symbol on the screen (such as
an arrow or hand) that follows the movement of the
mouse as the user moves it.
mouse scaling. The distance the cursor moves
relative to the mouse movement. The scaling factor
is either 1:1 or 2:1.
mouse threshold. An operating system parameter
that determines the amount of horizontal or vertical
mouse movements required to move the cursor on
the screen.
msqid. See message queue ID.
MTU. See maximum transfer unit.
multidrop. (1.) Stations connected to a multipoint
channel at one location. (2.) A network
configuration in which there are one or more
intermediate nodes on the path between a central
node and an endpoint node.
multihomed machine. A machine that has more
than one configured network adapter and more
than one host name.
multihomed server. A server that has more than
one network interface running.
multiline. More than one communications line.
multimode optical fiber. A graded–index or
step–index optical fiber that allows more than one
bound mode to propagate. Contrast with
single–mode optical fiber.
multiple inheritance. An object–oriented
programming technique implemented in C++
through derivation, in which the derived class
inherits members from more than one base class.
multiplex. To interleave or simultaneously transmit
two or more messages on a single channel.
multiplexed device. (1.) A device that takes
several input signals and combines them into a
single output signal so that each of the input
signals can be recovered. (2.) A device capable of
interleaving events of two or more activities or
capable of distributing events of an interleaved
sequence to the respective activities.
multiplexer. See multiplexed device.
multipoint. Pertaining to communication among
more than two stations over a single
telecommunications line.
ms. A package of macros for manuscript and
thesis preparation that features automatic footnote
numbering and bibliography capabilities.
multipoint link. A circuit that interconnects several
stations.
msb. Most significant bit.
multitasking. A mode of operation that provides
for concurrent performance or interleaved
MSB. Most significant byte.
Glossary
1-95
processing of two or more tasks. Synonym for
tasking.
multiuser mode. A mode of operation that enables
two or more users to use the services of a
processor within a given period of time. The usage
is usually serial unless otherwise specified.
mutex. Jargon for mutual exclusion lock. Use of
this type of lock excludes all threads other than the
lock holder from any access whatsoever to the
locked resource.
mutual exclusion mechanism. A means for
preventing two separately executing pieces of code
1-96
Glossary
from interfering with each other’s use of a particular
data object. For example, if one thread is executing
a function that modifies a shared data structure,
then the application may need to prevent other
threads from attempting to read the data
simultaneously, before the modifications are
complete.
MVS. Multiple Virtual Storage.
MVS/TSO. A type of operating system used on a
System/370 computer.
mwm. AIXwindows window manager. See also
window manager.
N
n. See en.
NA. Not applicable.
name. (1.) A sequence of 1 to 250 alphanumeric
characters, the first of which must be alphabetic,
that identifies a data object. (2.) In Ada language, a
name is a construct that stands for an entity: it is
said that the name denotes the entity, and that the
entity is the meaning of the name. See also
declaration and prefix. (3.) In C++, a name is
commonly referred to as an identifier. However,
syntactically, a name can be an identifier, operator
function name, conversion function name,
destructor name, or qualified name. See also
symbolic name.
name–lookup method resolution. Similar to the
method resolution techniques employed by
Objective–C and Smalltalk. In SOM, it is
significantly slower than offset resolution.
Name–lookup resolution, unlike offset resolution,
can be used when the name of the method to be
invoked is not known until run time, or the method
is added to the class interface at run time, or the
name of the class introducing the method is not
known until run time.
name resolution. The process of translating
(resolving) a symbolic name into its more efficient
Internet address.
name server. A host that provides name resolution
for a network. Name servers translate symbolic
names assigned to networks and hosts into the
efficient Internet addresses used by machines.
name string. A character string that identifies one
of a variety of objects such as an icon, a resource,
or a font.
named common. In FORTRAN, a separate
common block consisting of variables and arrays
and given a name.
named pipe. A pipe that an application opens by
name in order to write data into or read data from
the pipe. By convention, named pipes are placed in
the /dev directory and are treated as special files.
Using a named pipe facilitates communication
between a sending process and a receiving
process.
naming scope. See scope.
NaN. See not–a–number.
national language support. Conversion
subroutines for languages other than American
English that translate between various character
sets and date and time string formats. Synonymous
with international character support.
national terminal number (NTN). In X.25
communications, the 1– to 12–digit number that
follows the country code in the network user
address.
natural or social science format. The style of
bibliography entry favored by writers in the natural
and social sciences.
navigation keys. In CDE, the keyboard keys used
to move the current location of the cursor. These
include the arrow keys (with or without the Control
key); the Tab key (with or without the Control or
Shift keys); the Begin and End keys (with or without
the Control key); and the Page Up and Page Down
keys.
NCA. See Network Computing Architecture.
NCCF. See Network Communications Control
Facility.
NCK. See Network Computing Kernel.
NCS. See Network Computing System.
NCS cell. A logical concept of grouping together
one or more machines in an NCS network. Any
node belonging to an alternate cell may only have
their license requests satisfied by License Use
Management servers in that cell. Nodes outside the
cell may not make license requests to servers in
another cell. Two types of cells, default and
alternate, are used to provide two ways of
accessing License Use Management servers.
NDC. See normalized device coordinates.
negative response. In data communications, a
reply indicating that data was not received correctly
or that a command was incorrect or unacceptable.
negotiation. In X.25 communications, the process
by which two DTEs establish the packet size,
packet window size, and throughput class to be
used during a call procedure. Contrast with
validation.
neighbor gateway. One of the peers acquired by
an exterior gateway. All exterior gateways do not
communicate with all other exterior gateways.
Instead, they acquire neighbors through which they
communicate.
nest. (4.) To incorporate a structure or structures
into a structure of the same kind. (5.) To place
subroutines or data in other subroutines or data at
a different hierarchical level. Therefore, the
subroutines can be run as recursive subroutines or
so that the data can be accessed recursively. (6.) A
self–contained software element that completely
Glossary
1-97
encompasses a similar software element is said to
have that similar element ”nested” within it.
Examples include software loops (the nested loop)
nested within larger loops (the nesting loop) and
submenus nested within menus.
nested class. A C++ class defined within the
scope of another class.
nested DO. In FORTRAN, a DO loop or DO
statement in which the range is entirely contained
within the range of another DO loop.
nested transaction. A transaction begun within
the scope of another transaction. These are also
referred to as subtransactions.
NETASCII. Eight–bit ASCII with the first bit always
set high, for error checking.
NetBios. Network Version of Basic Input/Output
System.
NetLS. See License Use Management.
netlsd. The command used to invoke the network
license server daemon.
network. A collection of data processing products
that are connected by communication lines for
information exchange between locations.
network adapter. Circuitry that allows devices to
communicate with other devices on the network.
network address. (1.) The part of an address
indicating a specific network. A complete address
for a machine on a network consists of the network
address and the host address. (2.) In NCS, a
unique identifier (within an address family) for a
specific host on a network or an internet. The
network address is sufficient to identify a host, but
does not identify a communication end point within
the host.
Procedure Call runtime library and the Location
Broker. NCS is the underlying communications
protocol used by License Use Management to
transmit licensing transactions between clients and
servers. Messages are broadcast from clients to
the NCS–managed network.
Network File System (NFS). A distributed file
system that enables users to access files and
directories located on remote computers and treat
those files and directories as if they were local.
NFS is independent of machine types, operating
systems, and network architectures through the
use of remote procedure calls (RPC).
Network Information Center (NIC). The
publication distribution center for DARPA TCP/IP
information.
Network Installation Management (NIM). An
environment that provides installation and
configuration of software within a network interface.
network interface. The software that formats
packets at the network layer into packets that
specific network adapters can understand and
transmit.
Network License System. See License Use
Management.
network management. The conceptual control
element of a data station that interfaces with all of
the layers of that data station and is responsible for
the setting and resetting control parameters,
obtaining reports of error conditions, and
determining if the station should be connected to or
disconnected from the medium.
network mask (netmask). A 32–bit mask used to
identify the most local portion of a local area
network (LAN).
network boot image. A boot image that supports
standalone, diskless, and dataless machines.
network object. An entry in the Network
Installation Management database that represents
a local area network.
Network Communications Control Facility
(NCCF). A licensed program that serves as a base
for command processors that can monitor, control,
and improve the operation of a network.
network protocol. A communications protocol
from the Network Layer of the OSI network
architecture, such as the Internet Protocol (IP).
Network Computing Architecture (NCA). A set of
protocols and architectures that support distributed
computing.
Network Computing Kernel (NCK). The
combination of the RPC runtime library and the
Location Broker, which contain the necessary
pieces required to run distributed applications.
Network Computing System (NCS). A set of
software tools developed by Apollo Computer Inc.
that conform to the Network Computing
Architecture. These tools include the Remote
1-98
Glossary
network provider. In X.25 communications, the
organization, often a PTT, that provides a public
network.
network state. A state that indicates either that the
network object can participate in NIM operations or
an error in the definition of the network object.
network terminating unit (NTU). In X.25
communications, the point of access to the
network.
Network Time Protocol (NTP).
Internet–recommended time standard.
network user . A kernel–level protocol or
user–level application that accesses the services of
the network layer.
network user address (NUA). In X.25
communications, the X.121 address containing up
to 15 binary code digits.
network user identification (NUI). (1.) The facility
that enables the transmitting DTE to provide billing,
security, or management information on a per–call
basis to the DCE. (2.) The NUI can identify a
network user independent of the port being used.
See also address.
new. In C++, a keyword identifying a free store
allocation operator. The new operator may be used
to create class objects.
new installation. An installation method used
when the fixed disk or disks you are installing BOS
onto are empty. A hard disk is considered empty if
it does not contain any data or if it contains data
not in a volume group.
new–line character (NL). A control character that
causes the print or display position to move down
one line. This character is represented by ’\n’ in the
C language. Usually a carriage return is implicitly
associated with an NL.
new–process image. A new program laid over the
current program by the exec subroutine.
next. The dialog management action for
dependent workstations that causes the next
portion of a data object to be presented.
NFS. See Network File System.
NIC. See Network Information Center.
nice value. A number that is used to bias the
priority of a process. A higher number results in a
lower priority.
nickname. Synonym for alias.
NIM. See Network Installation Management.
NIM routing. The information that defines which
networks in the NIM environment can communicate
with each other and which gateways they use to
facilitate that communication. NIM routing is used
to represent the TCP/IP routine that exists for the
LANs in the overall network environment.
NIS. Network Information Service. A distributed
database that allows you to maintain consistent
configuration files throughout your network.
NL. See new–line character.
node. (1.) A computer connected to a network. (2.)
An end point of a link, or a junction common to two
or more links in a network. Nodes can be
processors, controllers, or workstations, and they
can vary in routing and other functional capabilities.
(3.) In Systems Network Architecture the portion of
a hardware component, along with its associated
software components, that implements the
functions of the seven architectural layers (SNA).
(4.) In a tree structure, a point at which subordinate
items of data originate.
node ID. A unique string of characters that
identifies the node on a network.
node verification. An additional level of security
beyond that provided by the network addressing
scheme. Node verification helps to ensure that a
connection reaches the correct remote station. It is
available on LU6.2 connections only. See also
BIND password.
nodelock file. The text file at a user node (rather
than at a license server node) where nodelocked
licenses are added. The nodelock file is located in
the /usr/lib/netls/conf directory.
nodelocked license. A type of license locked to a
specific node so that the product may only be used
at that node. The license server does not
administer nodelocked licenses.
nodes. Systems connected in a network to form a
monitor cell.
no–input zone. Synonym for dead zone.
noise. (1.) A disturbance that affects a signal and
potentially distorts the information carried by that
signal. (2.) Random variations of the characteristics
of any entity, such as voltage, current, or data.
(3.)A random signal of known statistical properties
of amplitude, distribution, and spectral density.
nolock lock. A dummy lock mode that is used
when a lock mode must be supplied, but when
actually locking the data is not required. Functions
specifying this lock mode can read data even when
it is currently locked by other operations or
transactions, enabling dirty reads to be performed.
This type of lock is operationally consistent, which
means that using it to lock and read a value will
return an actual value that was correct at some
moment in time, but is not transactionally
consistent.
nondeterministic program. A program whose
results cannot be determined by analyzing the
source code. A program that does not initialize
variables before their first use is nondeterministic,
because the value of an uninitialized variable can
change between runs of the program.
nonexecutable program unit. In FORTRAN, a
block data subprogram.
nonexecutable statement. A statement that
describes the characteristics of a program unit,
Glossary
1-99
data, editing information, or statement functions,
but does not cause any action to be taken.
non–extended result. An exception notification
that does not have any data defined in the
result_ext file of the dlc_getx_arg structure.
non–printing character. Synonym for control
character.
non–productive. Data traffic on the media that is
only made up of repetitive control information and
does not contain end user data.
non–return–to–zero (NRZ). A binary code system
in which a signal condition must be sustained for
the full time interval and does not revert to a
standby or quiescent state between signal
elements. Using NRZ permits the maximum data
signaling rate on the channel, which should be
twice the band width, according to Nyquist’s
theorem.
nonspacing character. See diacritic.
nonspacing character sequence. For accented
characters, a two–part sequence consisting of a
valid diacritic followed by an alphabetic character
or a space. The system converts the sequence into
a single code point that results in the alphabetic
character with the specified diacritic mark.
nonswitched line. (1.) A connection between
computers or devices that does not have to be
established by dialing. (2.) A dedicated line.
Synonym for leased facility. Contrast with switched
line.
nonswitched network. On a network, a
connection between computers or devices that
does not have to be established by dialing.
nonterminal symbol. The structure that the parser
recognizes.
nonvolatile random access memory (NVRAM).
Random access memory (storage) that retains its
contents after the electrical power to the machine is
shut off. A specific part of NVRAM is set aside for
use by the system ROS for the boot device list.
nonzero. A value that is not equal to zero.
normalized device coordinates (NDC). In GL,
coordinates in the range from –1 to 1. All primitives
that draw within the unit cube are visible on the
screen (unless masked by the screen mask). See
also transformation and unit cube.
not–a–number (NaN). In binary floating–point
computations, a value, not interpreted as a
mathematical value, that contains a mask state and
a sequence of binary digits.
notify flag. A parameter that indicates whether a
reply is required at that point in an event loop.
nroff. A typesetting utility originally designed to
drive Teletype model 37 printing workstations. It
now drives a wide variety of backspacing and
non–backspacing tty–type line printers and
tty–emulating printers.
NRZ. See non–return–to–zero.
NS. Network Systems. Also, Network Services.
NSA. Next station addressing.
NSI. Name Service Interface.
NTN. See national terminal number.
NTP. See Network Time Protocol.
NTSC. A national television industry broadcasting
standard as defined by the National Television
Standard Committee used in the USA, Canada,
Japan, and other countries. A video display and
timing format that is the American broadcast
standard. Most video tape recorders record and
play back NTSC signals. Specialized hardware is
required to convert from RGB monitor outputs to an
NTSC signal. See also PAL and SECAM.
NTSC signal. A signal as defined by the National
Television Standard Committee. Also called
composite video.
NTU. See network terminating unit.
NUA. See network user address.
NUI. See network user identification.
NUL. See null character.
normal attachment stop. See normal stop.
NUL character. In XPG4 system interface, a
character with all bits set to zero.
normal mode. See multiuser mode.
null. Empty, having no value, containing nothing.
normal port. A port that is asynchronous and
allows users to log in. No outgoing use of the port
is allowed while it is enabled.
NULL. In the C language, a pointer guaranteed not
to point to a data object.
normal stop. One of two ways to stop an
attachment. (The other way is a forced stop.) If the
attachments or any of their connections are in a
pending state, SNA Services rejects the normal
stop attachment action.
1-100
Glossary
null character (NUL). (1.) The hex 00 character
used to represent the absence of a printed or
displayed character. (2.) A control character used
to accomplish media–fill or time–fill that can be
inserted into or removed from a sequence of
characters without affecting the meaning of the
sequence. (3.)A control character used to delimit a
string of characters.
null character string. Two consecutive single
quotation marks that specify a character string
consisting of characters.
null modem. See modem eliminator.
null signal. A signal parameter of 0 (zero).
null statement. A statement that consists of a
semicolon.
null–terminated. Having a zero byte at the end. In
the C language, character strings are stored this
way internally.
numeric. Pertaining to any of the digits 0 through
9.
numeric error. A situation where the result of a
real or integer expression exceeds a compiler’s
limits (or limits imposed by the programming
language) for such expressions.
numeric literal. A numeric character or string of
characters whose value is implicit in the characters
themselves. For example, 777 is literal as well as
the value of the of the number 777. A numeric
literal can contain any of the numeric digits 0
through 9, a plus or minus sign, and a decimal
point. Contrast with character literal.
NURBS. (Non–Uniform Rational B–spline). A
parametric surface that can be trimmed with
nonuniform rational B–spline curves and piecewise
linear curves. See also trimming loops.
NVRAM. See nonvolatile random access memory.
numeric character. See digit.
numeric constant. A constant that expresses an
integer, real, or complex number.
Glossary
1-101
O
O. Organization.
object. (1.) In the NIM environment, an entry in the
NIM database that represents a machine, network,
or resource. (2.) In Enhanced X-Windows, a
software abstraction consisting of private data and
private and public routines that operate on the
private data. Users of the abstraction can interact
with the object only through calls to the public
routines of the objects. (3.) In ODM, an instance or
member of an object class, conceptually similar to
a structure that is a member or an array of
structures. See also object class. (4.) In Pascal,
synonymous with data object. (5.) In GL,
synonymous with display list. A sequence of
drawing commands that have been compiled into a
unit. Conceptually, a display list is like a macro; it
can be invoked multiple times simply by referring to
its name. The object can be instantiated at different
locations, sizes, and orientations by appropriate
use of the transformation matrices. For instance,
series of polygons arranged in the shape of a bolt
can be compiled into an object. The bolt can then
be drawn multiple times by invoking its display list.
(6.) In NCS, an entity that is manipulated by
well–defined operations. Disk files, printers, and
array processors are examples of objects. Objects
are accessed though interfaces. Every object has a
type. (7.) In Ada language, an object contains a
value. A program creates an object either by
elaborating an object declaration or by evaluating
an allocator. The declaration or allocator specifies a
type for the object: the object can only contain
values of that type. See also constant and variable.
(8.) In C++, a region of storage. An object is
created in C++ when a variable is defined or new is
invoked. An object is destroyed when it goes out of
scope. (9.) In XDS, anything in some ‘‘world,’’
generally the world of telecommunications and
information processing or some part thereof, that is
identifiable (can be named) and for which the DIB
contains some information. (10.) In XOM, any of
the complex information objects created,
examined, modified, or destroyed by means of the
interface. (11.) In SOM, an entity that has state (its
data values) and behavior (its methods). An object
is one of the elements of data and function that
programs create, manipulate, pass as arguments,
and so forth. An object is a way to encapsulate
state and behavior. Encapsulation permits many
aspects of the implementation of an object to
change without affecting client programs that
depend on the object’s behavior. In SOM, objects
are created by other objects called classes. (12.) In
CDE, any logical piece of data that has associated
1-102
Glossary
behavior. For example, in File Manager, files,
folders, actions, and applications are all considered
objects. Each type of object has specific associated
actions. Typically, each object is represented as an
icon. See also type UUID .
object adapter (OA). In SOM, a CORBA term
denoting the primary interface a server
implementation uses to access ORB functions; in
particular, it defines the mechanisms that a server
uses to interact with DSOM, and vice versa. This
includes server activation/deactivation, dispatching
of methods, and authentication of the principal
making a call. The basic object adapter described
by CORBA is defined by the BOA (basic object
adapter) abstract class; DSOM’s primary object
adapter implementation is provided by the SOMOA
(SOM Object Adapter) class.
object class. In ODM, a stored collection of
objects with the same definition, conceptually
similar to an array of structures. See also object,
terminal descriptor, and class.
Object Class Table (OCT). A recurring attribute of
the directory schema with the description of the
object classes permitted.
object code. (1.) Instructions that are able to be
run by a machine, usually generated by a compiler
from source code written in a higher–level
language (such as C language). For programs that
must be linked, object code consists of relocatable
machine code. (2.) Output from a compiler or
assembler that is itself executable machine code or
is suitable for processing to produce executable
machine code. Contrast with source code.
Object Data Manager (ODM). A data manager
intended for the storage of system data. The ODM
is used for many system management functions.
Information used in many commands and SMIT
functions is stored and maintained in the ODM as
objects with associated characteristics.
object definition. See class.
object file. (1.) A member file in an object library.
(2.) The primary output of a compiler or assembler,
which can be processed by the binder (ld) to
produce an executable file. The names of object
files normally end in .o.
object handle. In graphical files, the start point of
an arc or lines object.
object identifier. A value (distinguishable from all
other such values) that is associated with an
information object. (X.208)
object implementation. See implementation.
object instance. See instance and object.
object library. An area on a direct access storage
device used to store object programs and routines.
object management. The creation, examination,
modification, and deletion of potentially complex
information objects.
object module. (1.) A portion of an object program
suitable for input to a linkage editor. (2.) A set of
instructions in machine language produced by a
compiler from a source program. See also module.
object–oriented programming. A programming
approach based on the concepts of data
abstraction and inheritance. Unlike procedural
programming techniques, object–oriented
programming concentrates not on how something
is accomplished but instead on what data objects
comprise the problem and how they are
manipulated.
object program. A fully compiled or assembled
program that is ready to be loaded into the
computer. Synonymous with target program.
object reference. In SOM, a CORBA term
denoting the information needed to reliably identify
a particular object. This concept is implemented in
DSOM with a proxy object in a client process, or a
SOMDObject in a server process. See also proxy
object, server object, and SOMDObject.
object request broker (ORB). See ORB.
object space. The space in which a graphics
object is defined. A convenient point is chosen as
the origin and the object is defined relative to this
point. When an object is rendered by a call to the
callobj subroutine, it is rendered in modeling
coordinates, and the object space becomes (for
that moment) the same as the modeling space.
object type. In CDE, a desktop mechanism used
to associate particular data files with the
appropriate applications and actions. Object typing
defines the criteria for typing the file (such as name
or contents), the appearance (the icon used in File
Manager), and the behavior of the object (for
example, what happens when you double–click it).
object UUID. A UUID that identifies a particular
object. Both the RPC runtime library and the
Location Broker in NCS use object UUIDs to
identify objects. See also Universal Unique
Identifier (UUID).
obscure. In Enhanced X-Windows, (1.) A state of
being for a window. A window is obscured if
another window is in front of it making the obscured
window partially viewable. Window B is obscured
by window A if both are viewable InputOutput
windows and A is higher in the global stacking
order and the rectangle defined by the outside
edges of A intersects the rectangle defined by the
outside edges of B. Window borders are included
in the calculation, and a window can be obscured
and yet still have visible regions. (2.) An action one
window does to another when it partially obstructs
the viewing of the other. Window A obscures
window B if both are viewable InputOutput
windows, A is higher in the global stacking order,
and the rectangle defined by the outside edges of
A intersects the rectangle defined by the outside
edges of B. Contrast with widget visibility.
occlude. In Enhanced X-Windows, (1.) A state of
being for a window. A window is occluded if the
view of it is completely obstructed by another
window. Window B is occluded by window A if both
are mapped, A is higher in the global stacking
order, and if no part of the border of B is viewable.
A fine distinction exists between ”occlude” and
”obscure.” Window borders are included in the
calculation. InputOnly windows never obscure
other windows but can occlude other windows. (2.)
An action one window does to another when it
completely obstructs the view of the other. Contrast
with widget visibility.
OCS. On–Card Sequencer.
OCT. See Object Class Table.
octal. (1.) A base–eight numbering system. (2.)
Pertaining to a fixed–radix numeration having a
radix of eight.
octal constant. The digit 0 (zero) followed by any
digits 0 through 7.
octet. (1.) A group of 8 bits (also known as a byte).
(2.) Pertaining to a selection, condition, or choice
that has eight potential values or states. See also
octet string.
octet string. A string made up of octets. See also
octet.
ODM. See Object Data Manager.
off–hook. Activated, with regard to a telephone
set. On a public switched system, a data set that
automatically answers is said to go off–hook.
Contrast with on–hook.
offline. (1.) Pertaining to the operation of a
functional unit when it is not under the direct control
of a computer. (2.) Neither controlled directly by nor
communicating with the computer. Contrast with
online.
offset. (1.) In Pascal, the selection mechanism in
the SPACE data type; an element is selected by
placing an integer value in brackets. The origin of
SPACE is based on zero. (2.) In publications, the
indentation of all lines of a block of text following
the first line.
Glossary
1-103
offset method resolution. The default mechanism
for performing method resolution in SOM, because
it is the fastest (nearly as fast as an ordinary
procedure call). It is roughly equivalent to the C++
”virtual function” concept. Using offset method
resolution requires that the name of the method to
be invoked must be known at compile time, the
name of the class that introduces the method must
be known at compile time (although not necessarily
by the programmer), and the method to be invoked
must be a static method.
OIDL. The original language used for declaring
SOM classes. The acronym stands for Object
Interface Definition Language. OIDL is still
supported by SOM release 2, but it does not
include the ability to specify multiple inheritance
classes.
OM. See XOM.
on–hook. Deactivated, in regard to a telephone
set. A telephone not in use is ”on–hook.” Contrast
with off–hook.
On Item help. In CDE, when you choose On Item
from the Help menu, the cursor changes to a
question mark and you can obtain information
about a particular command, operation, dialog box,
or control by clicking that object.
On Item Help control. In CDE, Front Panel control
used to access item help information on the Front
Panel.
one–copy serializable. The consistency property
of the SOM Replication Framework which states
that the concurrent execution of methods on a
replicated object is equivalent to the serial
execution of those same methods on a
nonreplicated object.
one–way channel. In X.25 communications, a
logical channel that allows incoming calls only or
outgoing calls only. Contrast with two–way channel.
ones complement. The diminished radix
complement in the pure binary numeration system.
The ones complement is derived by replacing all of
the zeros with ones and all of the ones with zeros
in a binary number. In a ones complement system,
the ones complement of a number n is –n. See
also twos complement.
online. (1.) Being controlled directly by or directly
communicating with the computer. Contrast with
offline. (2.) Pertaining to the operation of a
functional unit when under the direct control of a
computer.
op code. See operation code.
opaque. See opaque data type.
1-104
Glossary
opaque data structure. A data structure used
internally by one functional unit of code but
exported for limited external use in another
functional unit of code. The external uses must
avoid accessing the structure’s components or
making assumptions about its constitution.
opaque data type. In XDR, bytes of a fixed size
that are not interpreted as they pass through the
data streams between computers.
opaque structure. A data item or data type whose
structure is hidden from the code that is handling it.
open. To make a file available to a program for
processing. Contrast with close.
Open Systems Interconnection (OSI). (1.) The
interconnection of open systems in accordance
with specific ISO standards. (2.) The use of
standardized procedures to enable the
interconnection of data processing systems.
operand. (1.) An instruction field that represents
data (or the location of data) to be manipulated or
operated upon. Not all instructions require an
operand field. (2.) An identifier, constant, or
expression that is grouped with an operator. (3.) An
entity on which an operation is performed. (4.)
Information entered with a command name that
defines the data on which a command processor
operates and that controls the running of the
command processor.
operating system (OS). A set of programs that
control how the system works. Controls the running
of programs and provides such services as
resource allocation, scheduling, input and output
control, and data management.
operation. (1.) A specific action (such as add,
multiply, or shift) that the computer performs when
requested. (2.) In NCS, a procedure through which
an object is accessed or manipulated. An operation
is defined syntactically by its name and its
parameters but not by its implementation. (3.) In
Ada language, an operation is an elementary
action associated with one or more types. It is
either implicitly declared by the declaration of the
type, or it is a subprogram that has a parameter or
result of the type.
operation code (op code). A numeric code that
tells the processor which operation to perform.
operation logging. In the SOM Replication
Framework, a technique for maintaining
consistency among replicas of a replicated object,
whereby the execution of a method that updates
the object is repeated at the site of each replica.
operator. (1.) A symbol (such as +, –, or *) that
represents an operation (in this case, addition,
subtraction, multiplication). (2.) A person who
operates a device. (3.) In Ada language, an
operator is an operation which has one or two
operands. A unary operator is written before an
operand; a binary operator is written between two
operands. This notation is a special kind of function
call. An operator can be declared as a function.
Many operators are implicitly declared by the
declaration of a type (for example, most type
declarations imply the declaration of the equality
operator for values of the type).
operator function. An overloaded C++ operator
that is either a member of a class or takes at least
one argument that is a class type or a reference to
a class type.
optimization. The process of achieving improved
run–time performance or reduced code size of an
application. Optimization can be performed by a
compiler, by a preprocessor, or through
hand–tuning of source code.
optimize. To improve the speed of a program or to
reduce the use of storage during processing.
optimized unit. An Ada–language compilation unit
that has been processed by one or more of the
compiler’s optimizing phases. Some source–level
information is unavailable to the debugger when it
examines the unit. You can use an optimized unit in
the same contexts as the corresponding
unoptimized unit. Optimized and unoptimized units
can be mixed within an Ada program.
option. (1.) An item of either hardware or software
that may be purchased in addition to the basic
system. An option can include cables, an adapter,
a warranty, and other items. (2.) A specification in a
statement that can influence the running of the
statement. (3.) An installable unit of a software
package. Software product options are separately
installable units that can operate independently
from other options of that software package.
option button. In CDE Desktop, a
diamond–shaped button that allows you to select
from a number of options.
optional facilities. In X.25 communications,
facilities that may or may not be offered by the
network provider to which customers choose
whether or not to subscribe. See also closed user
group, fast select, reverse charging, and
throughput–class negotiation.
optional software. Also referred to as optional
software products. Software that is not
automatically installed on your system when you
install the Base Operating System (BOS). Optional
software can be products packaged and sold with
BOS. Optional software can also be separately
purchased software products that are specially
ordered and not sold as part of BOS. In either
case, BOS must be installed on your system before
you can install optional software.
ORB (object request broker). In SOM, a CORBA
term designating the means by which objects
transparently make requests (that is, invoke
methods) and receive responses from objects,
whether they are local or remote. With SOMobjects
Developer Toolkit and Runtimes, this functionality is
implemented in the DSOM Framework. Thus, the
DSOM (Distributed SOM) system is an ORB. See
also BOA (basic object adapter) class and SOMOA
(SOM object adapter) class.
ordinal number. One of the counting numbers,
used to indicate position.
ordinal type. A type in which members can be
counted to indicate position.
ORed. Having the logical OR operation performed.
organization. Data that associates a named set of
users who can be granted common access rights
that are usually associated with administrative
policy. Also, the third field of a subject identifier.
orphaned files. Files that cannot be reached by
the fsck command.
orthographic projection. A representation in
which the lines of a projection are parallel.
Orthographic projections lack perspective
foreshortening and its accompanying sense of
depth realism. Because they are simple to draw,
orthographic projections are often used by
draftsmen. See also perspective projection.
OS. See operating system.
OS/2. Operating System/2.
OSF. Open Software Foundation.
OSI. See Open Systems Interconnection.
OSPF. Open Shortest Path First routing protocol.
OSS. OSI Session Service.
OU. Organizational Unit.
outgoing call. In X.25 communications, a call
being made to another data terminal equipment
(DTE).
output. (1.) The result of processing data. (2.)
Pertaining to a functional unit or channel involved
in an output process, or to the data or involved in
such a process. (3.) Data transferred from storage
to an output device. (4.) In Pascal, a predefined
standard file definition.
Glossary
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output buffer. In Enhanced X-Windows, an area
used by the Xlib library to store requests.
output device. A physical device that a computer
uses to present data to a user. Synonymous with
output unit.
output file. (1.) A file that a program opens so that
it can write to that file. (2.) A file that contains the
results of processing.
output handler. The program module responsible
for distributing data generated by a process or
subprocess.
output list. A list of variables from which values
are written to a file or device.
output mode. An open mode in which records can
be written to a file.
output redirection. The specification of an output
destination other than the standard one.
output stream. Messages and other output data
that an operating system or a processing program
displays on output devices.
output unit. Synonym for output device.
overflow. (1.) That portion of an operation’s result
that exceeds the capacity of the intended unit of
storage. (2.) In a register, the loss of one or more
of the leftmost whole–number digits because the
result of an operation exceeded the size of the
register.
overflow condition. (1.) A condition that occurs
when a portion of an operation’s result exceeds the
capacity of the intended unit of storage. (2.) A
condition that occurs when the overflow line on a
page has been printed or passed.
overflow line. The line specified as the last line to
be printed on a page.
overlay. (1.) To write over (and therefore destroy)
an existing file. (2.) A program segment that is
loaded into main storage, replacing all or part of a
previously loaded program segment. (3.)
Repeatedly using the same areas of internal
storage during different states of a program. (4.) In
DPS, a collection of predefined data such as lines,
shading, text, boxes, or logos that can be merged
with variable data while printing on a page. (5.) In
the M–Video Capture Adapter, the replacement of
specified pixels of one source with pixels from
another source such as memory pixels overlaid on
live images.
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Glossary
overlay planes. One or more bit planes in a
display buffer that are used to create visual data
(text, graphics, and so on) that overlays the visual
data in the frame buffer in a nondestructive
manner. Rather than a background color, overlay
planes are transparent.
overloading. (1.) In Ada language, an identifier
can have several alternative meanings at a given
point in the program text: this property is called
overloading. For example, an overloaded
enumeration literal can be an identifier that
appears in the definitions of two or more
enumeration types. The effective meaning of an
overloaded identifier is determined by the context.
Subprograms, aggregates, allocators, and string
literals can also be overloaded. (2.) In C++, a
capability that allows you to redefine functions and
most standard C++ operators when the functions
and operators are used with class types.
override. (1.) A parameter or value that replaces a
previous parameter or value. (2.) To replace a
parameter or value. (3.) In SOM, the technique by
which a class replaces (redefines) the
implementation of a method that it inherits from
one of its parent classes. An overriding method can
elect to call the parent class’s method procedure as
part of its own implementation. (Such a call is
known as a parent method call.)
overscan. A characteristic of display monitors
where a number of lines and horizontal pixels
delivered to the monitor exceed the visible display
space of the screen.
overstriking. A method of generating special
characters by typing one character and then,
without moving the print head to the next character
position, typing the second character on top of the
first.
overwrite. To record into an area of storage so that
the data that was previously stored there is
destroyed.
overwrite mode. A form of system operation that
replaces existing characters with characters typed
at the keyboard.
owner. The user who has the highest level of
access authority to a data object or action, as
defined by the object or action; usually the creator
of the object.
ownership. The creator or namer of an entity.
P
pacing. (1.) A technique used by a receiving
component to control the rate of transmission by
sending a component to prevent overrun. (2.) A file
transfer protocol required by some systems. It
controls data transmission by waiting for a
specified character, or waiting a specified number
of seconds between lines. This protocol prevents
the loss of data when the block size is too large or
data is sent too quickly for the system to process.
See also line pacing, local pacing, receive pacing,
and remote pacing.
pacing response. In SNA Services, an indicator
that signifies the readiness of a receiving
component to accept another pacing group. The
indicator is carried in a response header (RH) for
session–level pacing, and in a transmission header
(TH) for virtual–route pacing.
pack loop. A loop that packs active cells of a
sparse array into successive cells in another array,
so that the resulting array contains no empty cells
between its first and last active cells.
package. (1.) An installable unit of a software
product. Software product packages are separately
installable units that can operate independently
from other packages of that software product. (2.)
In Ada language, specifies a group of logically
related entities, such as types, objects of those
types, and subprograms with parameters of those
types. It is written as a package declaration and a
package body. The package declaration has a
visible part, containing the declarations of all
entities that can be explicitly used outside the
package. It may also have a private part containing
structural details that complete the specification of
the visible entities, but which are irrelevant to the
user of the package. The package body contains
implementations of subprograms (and possibly
tasks as other packages) that have been specified
in the package declaration. A package is one of the
kinds of program unit. See also private part.
package closure. The set of classes that need to
be supported to be able to create all possible
instances of all classes defined in the package.
packet. In data communications, a sequence of
binary digits, including data and control signals,
that is transmitted and switched as a composite
whole. The data, call control signals, and error
control information are arranged in a specific
format. See also call–accepted packet,
call–connected packet, call–request packet,
clear–confirmation packet, clear–indication packet,
clear–request packet, data packet, incoming–call
packet, interrupt packet, interrupt–confirmation
packet, reset–request packet, reset–confirmation
packet, address field, and restart–confirmation
packet.
packet assembler/disassembler (PAD). In X.25
communications, equipment used for connecting
asynchronous (start/stop) devices to an X.25
network.
packet header. In X.25 communications, control
information at the start of the packet; the contents
of the packet depend on the packet type.
packet level. In X.25 communications, the packet
format and control procedures for the exchange of
packets containing control information and user
data between the data terminal equipment (DTE)
and the data circuit–terminating equipment (DCE).
Synonymous with level 3. See also level, frame
level, datalink level, and physical level.
packet–level interface. In X.25 communications,
the level of the DTE/DCE interface in packet mode
operation relating to the exchange of data and
signaling, where this information is contained in
packets. See also frame–level interface.
packet mode operation. Synonym for packet
switching.
packet size. In X.25 communications, in the
context of data packets, refers to the length of the
user data.
packet switching. Routing and transferring data
by addressing packets so that a channel is
occupied only during packet transmission. On
completion of the transmission, the channel is
available for transfer of other packets. Synonymous
with packet mode operation. See also circuit
switching.
packet window. In X.25 communications, the
number of packets that can be outstanding without
acknowledgment. See also frame window and
window.
packing. In AIXwindows and Enhanced
X-Windows, the grouping of children objects within
a parent container object. If the children are closely
packed, the common distance between their
borders is minimal; if they are loosely packed, the
common distance border–to–border is maximized.
pad. (1.) To fill unused positions in a field with
dummy data, usually zeros or blanks. (2.) A device
used to introduce transmission loss into a circuit. It
can be inserted to introduce loss or match
impedances.
padding. Bytes inserted in the data stream to
maintain alignment of the protocol requests on
natural boundaries. Padding increases the ease of
portability to some machine architectures.
Glossary
1-107
page. (1.) A block of instructions, data, or both. (2.)
The number of lines that can fit into a window. (3.)
In a virtual storage system, a fixed–length block
that has a virtual address and is transferred as a
unit between real storage and auxiliary storage.
(4.) A contiguous 4096–byte portion of a
virtual–memory segment. The offset of each page
from the beginning of the segment is an integral
multiple of 4096. See also leaf.
page cluster. A type of memory buffer that is
constructed from a full memory page (normally
4096 bytes).
page fault. (1.) A program interruption that occurs
when an active page refers to a page that is not in
memory. (2.) An interrupt that occurs when the
processor attempts to access a virtual–memory
page that is not in real memory.
page frame. (1.) In real storage, a storage location
having the size of a page. (2.) An area of main
storage that contains a page. (3.) A
4096–contiguous–byte portion of real memory that
is used to hold a virtual–memory page.
page frame table. A table, contained in real
memory, that contains the real memory locations of
all currently defined pages.
pagination. (1.) The process of adjusting text to fit
within page margins. (2.) In word processing, the
automatic arrangement of text according to a
preset number of page layout parameters.
paging. (1.) The action of transferring instructions,
data, or both between real storage and external
page storage. (2.) Moving data between memory
and a mass storage device as the data is needed.
(3.) In System/370 virtual storage systems, the
process of transferring pages between real storage
and external page storage.
paging device. A disk device used to store pages
of memory that are not currently in real memory.
paging space. Disk storage for information that is
resident in virtual memory but is not currently being
accessed.
paint. In computer graphics, to shade an area of a
display image.
PAL. (1.) Programmable array logic. (2.) A national
television industry broadcasting standard used in
Europe and some other countries. See also NTSC
and SECAM.
PAL signal. A phase analog lock signal, also
called composite video. The European standard for
composite video.
palette. (1.) Location for building customized
components and parenting them with other
components. Subsequently, components can be
1-108
Glossary
reused by copying and moving them to other
interfaces. (2.) In CDE, a range of graphically
displayed choices, such as colors or collections of
tools, that you can select in an application.
pane. On a display screen, the inner portion of a
window used to present information to the user. A
window can consist of one or more panes. See
also menu pane.
panel. (1.) A set of logically related information
displayed on the screen for the purpose of
communicating information to or from a computer
user. (2.) A group of one or more panes that are
treated as a unit. The panes of a panel are
displayed together, erased together, and usually
represent a unit of information to a person using
the application. A panel is represented on the
display as a rectangular area tiled (completely
filled) with panes.
panning. (1.) In computer graphics, the viewing of
an image that is too large to fit on a single screen
by moving from one part of the image to another.
(2.) Progressively translating an entire display
image to give the visual impression of lateral
movement of the image.
paragraph. (1.) Text that is separated from other
text by blank lines. (2.) In word processing, one or
more sentences that maybe preceded by or
followed by an appropriate indicator.
parallel channel. Communications protocol
between controller and mainframe processors.
parallel device. A device that can perform two or
more concurrent activities. Contrast with serial
device.
parallel processing. The condition in which
multiple tasks are being performed simultaneously
within the same activity. Contrast with serial
processing.
parallel transmission. (1.) Transmitting all bits of
a character simultaneously. (2.) In data
communication, the simultaneous transmission of a
number of signal elements that constitute the same
telegraph or data signal.
parameter. (1.) Information that the user supplies
to a panel, command, or function. (2.) A variable
that is given a constant value for a specified
application. (3.) Data passed between programs or
procedures. (4.) In Ada language, a parameter is
one of the named entities associated with a
subprogram, entry, or generic unit, and used to
communicate with the corresponding subprogram
body, accept statement or generic body. A formal
parameter is an identifier used to denote the
named entity within the body. An actual parameter
is the particular entity associated with the
corresponding formal parameter by a subprogram
call, entry call, or generic instantiation. The mode
of a formal parameter specifies whether the
associated actual parameter supplies a value for
the formal parameter, or the formal supplies a
value for the actual parameter, or both. The
association of actual parameters with formal
parameters can be specified by named
associations, by positional associations, or by a
combination of these. See also formal parameter
and mode.
parameter block. A block of memory that contains
specific parameters for an ioctl operation.
parameter declaration. Description of a value that
a function receives. A parameter declaration
determines the storage class and the data type of
the value.
parametric bicubic surface. A surface defined by
three equations. The x equation is: x(u,v) =
a11u3v3 + a12u3v3 + a13u3v + a14u3 + a21u2v3
+ a22u2v2 + a23u2v + a24u2 + a31uv3 + a32uv2 +
a33uv + a34u + a41v3 + a42v2 + a43v + a44. The
equations for y and z are similar. The points on a
bicubic patch are defined by varying the
parameters u and v from 0 to 1. If one parameter is
held constant and the other is varied from 0 to 1,
the result is a cubic curve. If w(u,v)=1 for all u,v, the
bicubic surface is called ”ordinary,” but if w(u,v)
varies as a function of u,v, then the surface is
called ”rational.” See also homogeneous
coordinates.
parametric component. In AIXwindows, a simple
mechanism that delivers all the functions
necessary for most applications, yet is easier and
less time consuming to build.
parametric cubic curve. A curve defined by the
equation: x(t) = axt3 + bxt2 + cxt + dx; y(t) = ayt3 +
byt2 + cyt + dy; z(t) = azt3 + bzt2 + czt + dz; w(t) =
awt3 + bwt2 + cwt + dw. Where x, y, z, and w are
cubic polynomials. The parameter t typically varies
between 0 and 1. Such a curve is considered
rational only if a(w), b(w), or c(w) is not equal to 0;
otherwise, it is simply an ordinary parametric curve.
See also B–spline cubic curve, Bezier cubic curve,
and cardinal spline cubic curve.
parent. (1.) A process that has spawned a child
process using the fork primitive. (2.) Pertaining to a
secured resource, either a file or library, whose
user list is shared with one or more files or libraries.
Contrast with child. (3.) In AIXwindows and
Enhanced X-Windows, a graphical object that
controls one or more smaller graphical objects
attached to it. The smaller graphical objects are
called children, and they are automatically deleted
when their parent is deleted. (4.) In Ada language,
the associated specification of a package body or
subprogram body. The parent of a subunit is the
body in which it was declared.
parent class. In SOM, a class from which another
class inherits instance methods, attributes, and
instance variables. A parent class is sometimes
called a base class or superclass.
parent device. A hierarchical location term. It
indicates what device the device you are
concerned with connects to. For example, the
parent device of an SCSI disk might be an SCSI
adapter.
parent directory. The directory one level above
the current directory. See also parent folder.
parent folder. In CDE, a folder that contains
subfolders and files. When discussing
command–line activities, this may be called the
parent directory. See also subfolder.
parent ID. The character sequence identifying the
graphical object that controls smaller graphical
objects, called children.
parent method call. In SOM, a technique where
an overriding method calls the method procedure
of its parent class as part of its own
implementation.
parent type. For Ada programming, see derived
type.
parent window. In Enhanced X-Windows, the
window that controls the size and location of its
children. If a window has children, it is a parent
window.
parity bit. A binary digit (bit) appended to a group
of binary digits to make the sum of all digits in the
group either always odd (odd parity) or always
even (even parity).
parity check. A test to determine whether the
number of ones (or zeros) in an array of binary
digits is odd or even.
parity error. A transmission error that occurs when
the received data does not have the parity
expected by the receiving system. This error is
usually caused by the sending and receiving
systems having different parity settings.
parse. (1.) In systems with time sharing, to analyze
the operands entered with a command and create
a parameter list for the command processor from
the information. (2.) Before a command line
interpreter can convert an operating–system
command into an executable form of machine
code, the command must be broken down into
easily coded elements, or ”parsed”, by the
interpreter.
Glossary
1-109
parser. A program that interprets user input and
determines what to do with the input. See also
grammar rules.
information is contained indefinitely in the routing
tables and is included in any routing information
that is transmitted. Contrast with active gateway.
participant. An application is a participant in a
transaction when it either initiates the transaction or
receives a request on behalf of that transaction.
passive grab. In Enhanced X-Windows, grabbing
a key or button is a passive grab. The grab
becomes an active grab when the key or button is
actually pressed. Contrast with active grab. See
also grab, button grabbing, pointer grabbing, and
key grabbing.
partition. (1.) A logical division of storage on a
fixed disk. (2.) A fixed–size division of storage.
partner. In data communications, the remote
application program or the remote computer.
Pascal. A high–level, general–purpose
programming language. Programs written in Pascal
are block–structured, consisting of independent
routines.
pass–by–CONST. In Pascal, the
parameter–passing mechanism by which the
address of a variable is passed to the called
routine. The called routine is not permitted to
modify the formal parameter. Synonymous with
pass–by–read–only–reference.
pass–by–read–only–reference. Synonym for
pass–by–CONST.
pass–by–read/write–reference. Synonym for
pass–by–VAR.
pass–by–value. In Pascal, the parameter–passing
mechanism by which a copy of the value of the
actual parameter is passed to the called routine. If
the called routine modifies the formal parameter,
the corresponding actual parameter is not affected.
pass–by–VAR. In Pascal, the parameter–passing
mechanism by which the address of a variable is
passed to the called routine. If the called routine
modifies the formal parameter, the corresponding
actual parameter is also changed. Synonymous
with pass–by–read/write–reference.
pass–through function. The ability to pass data
through a program transparently, without alteration.
pass–through mode. The mode of use provided
by the VM/Pass–ThroughFacility, which allows VM
display station users to interactively access a VM
system, including the one to which the terminal is
attached. It also allows users to access non–PVM
systems that support Remote 3270 Binary
Synchronous Communication (BSC) display
stations and 4300 processors having the Remote
Operator Console Facility (ROCF). A user can
access, log on to, and use another system in a
defined network as though the user’s local terminal
were directly connected to that system. PVM
activities become transparent to the user once
logged on to the target system.
passive gateway. A gateway that does not
exchange routing information. Its routing
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Glossary
password. (1.) A string of characters known only
to the user and the system. The user must specify
the correct password to gain access to a system
and the data stored with it. (2.) A string encoded
with information about a software vendor (vendor
password) or about a software product (product
password).
password security. The process of requiring a
user to enter a password to log in to a system.
patch. A parametric bicubic surface.
path. (1.) In SNA, the series of path control
network components traversed by the information
exchanged between two network addressable units
(NAUs). A path consists of a series of path control
elements, data link control elements, and links. (2.)
In a network, any route between any two nodes.
(3.) In a database, a sequence of segment
occurrences from the root segment to an individual
segment. (4.) In the InfoExplorer program, the list
of articles you followed to get to the article that is
currently displayed. (5.) In CDE, a text string that
specifies the hierarchical location of a folder
(directory).
path list. The structure, or the corresponding
parameter, containing the full path name for a file.
path name. A file name specifying all directories
leading to the file. See also full path name and
relative path name.
pattern. (1.) A regular expression or series of
regular expressions that define the search pattern.
(2.) In GL, a 16x16, 32x32, or 64x64 array of bits
defining the texturing of polygons on the system
display.
pattern–action. When the awk command finds a
pattern in an input data file that matches a line in
the program file, it performs the associated action
on that line.
pattern address. Reference to a line by a string
contained within the line, rather than by a
numerical or symbolic address. A pattern address
can be a character string or a regular expression.
See also symbolic address.
pattern matching. Specifying a pattern of
characters that the system should find.
pattern–matching character. Special characters
such as * (asterisk) or ? (question mark) that can
be used in a file specification to match one or more
characters. For example, placing a ? in a file
specification means that any character can be in
that position. Synonymous with wildcard.
pattern strings. Strings of regular expressions
composed of special pattern–matching characters.
The pattern strings can be used in addresses to
specify lines and, in some subcommands, portions
of a line.
PBX. Private Branch Exchange. A private
telephone system that performs automatic
selection of outside lines.
PC. Personal computer.
PCI. Programmed Control Interrupt.
PCM. Physical Connection Management.
PCS. See programmable character set.
PDN. See public data network.
PE. Phrase Encoded, a magnetic tape recording
format with a density of 1600 bpi.
peak rate. The maximum speed at which a device
could operate under ideal conditions, if its designer
were choosing the workload.
peer–to–peer communications. Pertaining to
data communications between two nodes that have
equal status in the interchange. Either node can
begin the conversation. See also Logical Unit Type
6.2.
peer trust. A type of trust relationship established
between two cells by means of a secret key shared
by mutual authentication surrogates maintained by
the two cells. A peer trust relationship enables
principals in the one cell to communicate securely
with principals in the other.
pel. See picture element.
pending. Waiting, as in an operation that is
pending.
pending state. A condition of a server program in
which it has received a request for an action (start,
stop, or suspend) but has not yet performed that
action.
PEP. Packet Exchange Protocol. A datagram
service that is implemented by a user–level library,
using IDP datagram sockets.
per–process data area. In kernel mode, a portion
of the user process stack segment. This area is
paged with the process and it contains process
information such as the current directory of files
opened by the process or input in I/O mode. This
information occupies the top of the stack segment.
See also user block and user structure.
peripheral device. With respect to a particular
processing unit, any equipment that can
communicate directly with that unit.
peripheral unit. See peripheral device.
permanence. A basic property of transaction
processing systems. This term means that once a
transaction has committed, the modifications made
to data by that transaction must be permanent.
Subsequent transactions requesting the data
modified by a previous transaction must always
see the new data. These changes must be
preservable even in the event of a system failure.
permanent error. An error that cannot be
eliminated by retrying an operation.
permanent link. A connection below a multiplexer
that can exist without having an open controlling
stream associated with it.
permanent storage. A storage device whose
contents cannot be modified.
permanent virtual circuit (PVC). In X.25
communications, a virtual circuit that has a logical
channel permanently assigned to it at each DTE.
Call–establishment protocols are not required.
Contrast with switched virtual circuit. See also
virtual circuit.
permission. The modes of access to a protected
object.
permission code. A three–digit octal code or a
nine–letter alphabetic code that indicates access
permissions. The access permissions are read,
write, and run. See also access permission.
permission field. One of the three–character
fields within the permissions column of a directory
list. The permission field indicates the read, write,
and run permissions for the file or directory owner,
for the group, and for all others.
permissions. Codes that determine how the file
can be used by any users who work on the system.
In CDE Desktop, a set of flags that determine a
user’s access to files and directories, which you
can see using the Properties... command on the
File menu.
persistence. In Display PostScript (DPS), a
specified character set that is used for all
subsequent text segments in a compound string
until a new character set is encountered.
persistent data. Data which retains its value
across multiple runs of transactional applications,
regardless of system failures or restarts.
Glossary
1-111
persistent object. In SOM, an object whose state
can be preserved beyond the termination of the
process that created it. Typically, such objects are
stored in files.
persistent segment. A segment whose pages
have permanent locations on disk, rather than
temporary slots in the paging space.
perspective projection. A technique used to
achieve realism when drawing primitives. In a
perspective projection, the lines of projection meet
at the viewpoint; thus, the size of a primitive varies
inversely with its distance from the source
projection. The farther a primitive or part of a
primitive is from the viewer, the smaller it will be
drawn. This effect, known as perspective
foreshortening, is similar to the effect achieved by
photography and by the human visual system. See
also orthographic projection.
peta. Two to the fiftieth power.
PEX. A protocol for supporting three–dimensional
graphics.
PEXlib. A programmer’s interface to the PEX
protocol.
PFM. See program fault management.
phase. (1.) One of several stages of file system
checking and repair performed by the fsck
command. (2.) A distinct part of a process in which
related operations are performed. (3.) A part of a
sort and merge program, such as sort phase and
merge phase. (4.) A part of a data call.
phase modulation. Altering the phase of a carrier
signal to convey data signals.
PHIGS. See Programmers’ Hierarchical Interactive
Graphics System.
phototypesetter. A typesetting machine that
operates by projecting light through film matrices of
the type characters upon light–sensitive paper or
film.
physical block. See block.
physical data block. See block.
physical device. See device.
physical file. (1.) An indexed file containing data
for which one or more alternative indexes have
been created. (2.) A database file that describes
how data are to be presented or received from a
program and how data are actually stored in the
database. A physical file contains one record
format and one or more members.
physical layer. The lowest layer of network design
as specified by the ISO Open System
Interconnection (OSI) reference model. This layer
1-112
Glossary
is responsible for interfacing with the medium,
detecting and generating signals on the medium,
and converting and processing signals received
from the medium and from the data link layer. See
also physical level.
physical level. In X.25 communications, the
mechanical, electrical, functional, and procedural
media used to activate, maintain, and deactivate
the physical link between the data terminal
equipment (DTE) and the data circuit–terminating
equipment (DCE). Synonymous with level 1. See
also level, frame level, data–link level, packet level,
and physical layer.
physical network. A network of machines linked
by physical network cabling, modems, or other
hardware. A physical network can contain one or
several logical networks.
physical partition (PP). The smallest unit of
disk–space allocation for a logical volume. The
physical partition is contiguous space on a physical
volume. A fixed–size portion of a physical volume.
One or more physical partitions constitute the
underlying physical storage medium for a logical
partition.
physical unit (PU). In SNA, a set of programs that
control the actual physical hardware associated
with a node.
physical volume (PV). (1.) The portion of a single
unit of storage accessible to a single read/write
mechanism; for example, a drum, a disk pack, or
part of a disk storage module. (2.) A read–write
fixed disk physically attached to a computer. The
actual storage space provided by a single
fixed–disk drive. See also log volume.
picking. In computer graphics, a method for
finding out what primitives are being drawn near
the cursor on the display screen. See also hit,
picking region, selecting, and selecting region.
picking region. A rectangular volume around the
cursor that is sensitive to picking events. If a
drawing primitive draws within this volume, a pick
event is reported. The width and height of the
region can be set by the user. If the z–buffer is
enabled, the depth of the region is the entire
z–buffer. See also hit, selecting, picking, and
selecting region.
picture. A pixmap used for displaying CDE
Desktop icons, background patterns, and controls.
picture element (pel). (1.) In computer graphics,
the smallest element of a display space that can be
assigned color and intensity independently. (2.) A
point in the frame buffer or on the display. See also
pixel.
PID. See process ID.
piecewise linear curve. A list of coordinate pairs
in the parameter space for the Non–Uniform
Rational B–Spline (NURBS) surface. These points
are connected with straight lines to form a path.
pin. (1.) An area of memory reserved for certain
functions. (2.) One of the connectors in an adapter
plug.
PIO. See programmable input/output operation.
PIP. See Program Initialization Parameters.
pipe. (1.) To direct the data so that the output from
one process becomes the input to another process.
The standard output of one command can be
connected to the standard input of another with the
pipe operator ( | ). Two commands connected in
this way constitute a pipeline. (2.) A one–way
communication path between a sending process
and a receiving process. See also pipeline.
pipeline. (1.) A direct, one–way connection
between two or more processes. (2.) A serial
arrangement of processors or a serial arrangement
of registers within a processor. Each processor or
register performs part of a task and passes results
to the next processor. Several parts of different
tasks can be performed at the same time. (3.) To
perform processes in a series. (4.) For increased
processing speed, to start the running of an
instruction sequence before the previous
instruction sequence is completed. See also pipe.
pipeline options. In GL, variables that control the
flow of processing in the graphics pipeline. For
instance, lighting is a pipeline option. If lighting is
turned on, the color of a primitive is obtained by
evaluating the lighting equations. If lighting is
turned off, the last color specified is used. Other
pipeline options are the back–facing flag, the
shade–model flag, the depth–cueing flag, the
picking flag, the color–mode (color index or RGB)
flag, the z–buffer flag (enables or disables drawing
to the z–buffer), and so on. See also attribute.
pitch. A unit of width of typewriter type, based on
the number of times a letter can be set in a linear
inch. For example, 10–pitch type has 10 characters
per inch.
pixel. A rectangular picture element. The smallest
element used to compose an image, a single dot. A
display screen is composed of an array of pixels. In
a black–and–white system, pixels are turned on
and off to form images. In a color system, each
pixel has three components: red, green, and blue.
The intensity of each component can be controlled.
See also picture element.
pixel map. A three–dimensional array of bits. A
pixel map can be thought of as a two–dimensional
array of pixels, with each pixel being a value from
zero to 2 to the N –1, with N as the depth of the
pixel map. Synonym for pixmap.
pixel value. In Enhanced X-Windows, the number
of bit planes used in a particular window or pixmap.
For a window, a pixel value indexes a color map
and derives an actual color to be displayed. A pixel
is an N–bit value, where N is the number of bit
planes (the depth) used in a particular window or
pixmap.
pixmap. (1.) Synonym for pixel map. (2.) In
AIXwindows and Enhanced X-Windows, a data
type to which icons (originally created as bitmaps)
are converted. Once this conversion takes place,
the appropriate AIXwindows subroutines can
generate pixmaps through references to an
.Xdefaults file (by name) and through an argument
list (by pixmap). See also image cache.
placeholder. An object, component or file that only
exists to mark the position of an intended entity.
plaintext. The input to an encryption function or
the output of a decryption function. Decryption
transforms ciphertext into plaintext.
plane. When a pixmap or window is thought of as a
stack of bitmaps, each bitmap is called a plane or
bit plane.
plane mask. (1.) Determines which of the display
adapter storage places are modified by the output
functions. (2.) In Enhanced X-Windows, a bit mask
restricting graphics operations to affect a subset of
bit planes. It is stored in a graphics context.
Graphics operations can be restricted to affect only
a subset of bit planes of a destination.
platen. The support mechanism for paper on a
printer, commonly cylindrical, against which printing
mechanisms strike to produce an impression.
playing back. In Encina, the actions of the
Recovery Service when a TP system using
recoverable data is restarted. When started, the
Recovery Service plays back log records for
transactions that have prepared but which were not
actually committed, guaranteeing that the state of
that recoverable data reflects the records
maintained by the TP system.
PList. An array of pointers with a suite of
operations for adding and removing elements in
various ways.
plotter. A hard copy device, attached to the system
with cables, that prints two–dimensional graphs
and charts.
plug. A device that connects the wires of an
electrical circuit to an electrical source. The plug is
designed to be inserted into a jack.
Glossary
1-113
PMF. Parameter management frame.
PMP. See Preventive Maintenance Package.
contention, determine operational status, or
determine readiness to send or receive data.
PMR. See Problem Management Record.
polyline. In computer graphics, a sequence of
adjoining lines.
point. (1.) A unit of typesetting measure equal to
0.01384 inch (0.3505 mm), or about 1/72 of an
inch. There are 12 points per pica. (2.) In CDE, to
move the mouse until the pointer rests on a
particular screen element or area.
polymarker. In computer graphics, a sequence of
markers. The definition of the marker includes
specific attributes such as color, style, width,
height, pattern, and origin.
point–handle. A point within a graphic object.
point–to–point link. A switched or nonswitched
link that connects a single remote link station to a
node or to another station.
pointer. (1.) A variable that holds the address of a
data object. (2.) A physical or symbolic identifier of
a unique target. (3.) In computer graphics, the
device attached to the cursor and tracked on the
screen.
pointer grabbing. In Enhanced X-Windows, a
client can actively grab control of the pointer so that
button and motion events will be sent to that client
rather than the client to which the events normally
would have been sent. See also grab, button
grabbing, and key grabbing.
pointer to member. Used to access the address of
nonstatic members of a C++ class.
pointer type. A data type that defines variables
containing addresses and, sometimes, other
information about variables.
pointing. Positioning the pointing cursor on a
displayed object. The action of lining up the mouse
pointer so that the pointer lies on top of something.
pointing device. In Enhanced X-Windows, a
device with effective dimensional motion, usually a
mouse. One visible cursor is defined by the Core
protocol, and it tracks whatever pointing device is
attached as the pointer.
polar coordinates. A coordinate system in which
positions are measured as a distance from the
origin and an angle from some reference direction
(usually, counterclockwise from the x–axis).
poll. (1.) In data communications, an interrogation
that determines whether a station is ready to
transmit information. (2.) To run a polling
sequence.
polled I/O devices. Devices (keyboard, mouse,
button, dials) whose current values are read by the
user process.
polling. (1.) On a multipoint connection or a
point–to–point connection, the process whereby
data stations are invited, one at a time, to transmit
data. (2.) Interrogation of devices so as to avoid
1-114
Glossary
polymorphic functions. Functions that can be
applied to objects of more than one data type. C++
implements polymorphic functions in two ways:
overloaded functions (calls are resolved at compile
time); and virtual functions (calls are resolved at
run–time).
polymorphism. An object–oriented programming
feature that may take on different meanings in
different systems. Under various definitions of
polymorphism, (a) a method or procedure call can
be executed using arguments of a variety of types,
or (b) the same variable can assume values of
different types at different times, or (c) a method
name can denote more than one method
procedure. The SOM system reflects the third
definition (for example, when a SOM class
overrides a parent class definition of a method to
change its behavior). The term literally means
”having many forms.”
pop. A term used when a module that is
immediately below the stream head is removed.
pop–down. In Enhanced X-Windows, an action
referring to a type of widget that closes when a
pointer button is released.
pop up. (1.) In Enhanced X-Windows, a box on the
display screen that displays information or asks
you to make choices. (2.) In Enhanced X-Windows,
an action referring to a type of widget that opens
automatically when a pointer button is held down
within certain windows. (3.) To use a widget to
create a window outside the window hierarchy
defined by the widget tree.
pop–up cascade. In Enhanced X-Windows,
several spring–loaded pop–ups emanating in
succession from one modal pop–up.
pop–up child. In Enhanced X-Windows, a child on
the pop–up list.
pop–up list. A list of pop–up children stored in a
widget.
pop–up menu. (1.) Synonym for popup. (2.) In
AIXwindows, a type of MenuPane widget that
appears as the result of some user action (usually
clicking a mouse button) and then disappears when
the action is completed. (3.) The interface definition
for translation actions. (4.) In CDE, a menu that,
when requested, is displayed next to the object
with which it is associated. Pop–up menus are
usually displayed by clicking mouse button 3 or
pressing Shift+F10.
pop–up widget. In Enhanced X-Windows, a
window child of the root that is attached to its
widget parent differently than the normal widget; a
pop–up widget is not geometrically constrained by
its parent widget.
pop–up window. Any window that opens
automatically when activated. See also pop–up.
popdown. In AIXwindows, the manner in which a
type of MenuPane widget disappears suddenly
(pops down) in the display when some user action
(usually clicking a mouse button) is completed.
popup. In AIXwindows, the manner in which a type
of MenuPane widget appears suddenly (pops up)
in the display as the result of some user action
(usually clicking a mouse button). Synonym for
pop–up menu. See also pop–up window.
POR. See power–on reset.
port. (1.) A part of the system unit or remote
controller to which cables for external devices
(display stations, terminals, or printers) are
attached. The port is an access point for data entry
(input) to or exit from (data output) a computer
system. (2.) An entrance to or exit from a network.
(3.) To make the programming changes necessary
to allow a program that runs on one type of
computer to run on another type of computer. (4.)
In NCS, a specific communications end point within
a host. A port is identified by a port number. See
also socket and listening.
portability. The characteristic that determines
whether a source program can be compiled and
run on computers of different architectures without
requiring recoding.
abcdefghijklmnopqrstuvwxyz
0123456789._–
The last three characters are the period,
underscore, and hyphen characters, respectively.
The hyphen must not be used as the first character
of a portable file name. Uppercase and lowercase
letters retain their unique identities between
conforming implementations. In the case of a
portable path name, the slash character can also
be used.
Portable Operating System Interface For
Computer Environments (POSIX). An IEEE
standard for computer operating systems.
portrait display. A rectangular display that is taller
than it is wide. See also landscape display.
portrait upside–down. A page orientation such
that the top of the printed image is at the trailing
edge of the paper as it emerges from the printer.
POS registers. Programmable Option Select
registers. A set of registers that allow the software
to automatically configure devices on the Micro
Channel bus at the time the machine is turned on.
These registers allow the setup software (which is
run at the time the machine is turned on) to
automatically identify the adapter and to set up
various parameters on the adapter such as its
starting address and interrupt level.
position. (1.) Any location in a string that may be
occupied by an element and that is identified by a
serial number. (2.) The location of a character in a
series, as in a record, a displayed message, or a
computer printout.
position (within an attribute). The ordinal position
of one value relative to another.
position (within a string). The ordinal position of
one element of a string relative to another.
portable character set. In the XPG4 system
interface, the collection of characters present in all
locales supported by XSI–conformant systems: Or
ABCDEFGHIJKLMNOPQRSTUVWXYZ
positional association. In Ada language,
specifies the association of an item with a position
in a list, by using the same position in the text to
specify the item.
abcdefghijklmnopqrstuvwxyz
positional parameter. (1.) A shell facility that
assigns values from the command line to variables
in a program. (2.) A parameter that must appear in
a specified location relative to other positional
parameters.
0123456789!#%^&*()_+–={}[] :”~;’‘<>?,.|\/@$
Also included are the alert, backspace, tab,
newline, vertical–tab, form–feed, carriage–return,
space characters, and the null character, NUL.
portable file name character set. In the XPG4
system interface, the set of characters from which
portable file names are constructed. For a file
name to be portable across implementations of the
XPG4 and ISO POSIX–1 standard, it must consist
only of the following characters:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
POSIX. See Portable Operating System Interface
For Computer Environments.
post. The action required to make a pop–up or
pull–down menu appear. This action is normally a
click or button press on one of the mouse buttons.
POST. See power–on self–test.
Glossary
1-115
post processor. A computer program that effects
some final computation or organization. In text
formatting, a postprocessor command translates
the output of the nroff and troff commands for use
on certain printers, typesetters, or
phototypesetters.
posted event. A notification sent to the DLC by its
attached device handler by way of the e_post
system call.
PostScript. A graphics language used to drive
output of text and graphics. Trademark of Adobe
Systems, Inc.
pound (lb). Unit of measurement for weight equal
to 16 ounces or 454 grams.
power factor. The ratio of power consumed to the
volt amps (apparent power).
power–on light. The light on the operator panel
that indicates that the DC power in the system unit
is functioning.
power–on reset (POR). A key sequence that
restarts the operating system (or other program)
without turning off the electrical power of the
system.
power–on self–test (POST). A series of internal
diagnostic tests activated each time the system
power is turned on.
the number of digits that are printed or displayed.
(4.) The number of straight line segments used to
approximate one segment of a spline.
preconnected file. A unit or file that was defined
at installation time. For example, standard input
and standard output are preconnected files.
Predefined Connection Object Class. Specifies
the kind of connections that can be made to a
device and where.
predefined convention. In FORTRAN, the implied
type and length specification of a data item based
on the initial character of its name, when no explicit
specification is given. The initial characters I
through N imply type integer of length 4; the initial
characters A through H, O through Z, $, and _
imply type real of length 4.
predefined database. Contains configuration data
for all possible devices supported by the system.
See also Device Configuration Database and
Customized Database.
Predefined Devices Object Class. Represents
each device type, as determined by class,
subclass, and type. The Predefined Devices Object
Class contains basic information about the devices,
such as device method names and how to access
the information contained in the other object
classes.
PPA (physical point of attachment). The point at
which a system attaches itself to a physical
communications medium.
predicate. Boolean logic term denoting a logical
expression that determines the state of some
variables. For example, a predicate can be an
expression stating that ”variable A must have the
value 3.” The control expression used in
conjunction with condition variables is based upon
a predicate. Use a condition variable to wait for
some predicate to become true, for example, to
wait for something to be in a queue.
PPA identifier. An identifier of a particular physical
medium over which communication occurs.
preferential CUG. In X.25 communications, the
default closed user group.
P(R). In X.25 communications, the packet receive
sequence number.
prefix. In Ada language, used as the first part of
certain kinds of name. A prefix is either a function
call or a name. See also name.
power requirement. The actual power consumed
by a computer system, measured in watts.
power source. The minimum acceptable rating of
the electrical circuit providing power to a computer
system, measured in volt amps (kVA).
pragma. In Ada language, conveys information to
the compiler.
precedence. (1.) The priority system for grouping
different types of operators with their operands. (2.)
In programming languages, an order relation
defining the sequence of the application of
operators within an expression.
precision. (1.) A measure of the ability to
distinguish between nearly equal values. See also
single precision and double precision. (2.) The
degree of discrimination with which a quantity is
stated. For example, a three–digit numeral
discriminates among 1000 possibilities. (3.) In GL,
1-116
Glossary
preinstalled. Software that is installed by the
manufacturer and ready to use.
premultiplication. In GL, matrix multiplication on
the left. If a matrix M is premultiplied by a matrix T,
the result is TM.
preprocessor. (1.) A functional unit that effects
preparatory computation or organization. (2.) In
emulation, a program that converts data from the
format of an emulated system to the format
accepted by an emulator. (3.)A program that
examines the source program for preprocessor
statements, which are then run, resulting in the
alteration of the source program. (4.)A program
that modifies, and possibly optimizes, source
programs before they are processed by a compiler.
preprocessor statement. In C language, a
statement that begins with the # (pound sign) and
contains instructions that the preprocessor
interprets.
prerequisite. A software product or a service
update that must be installed before another
software product or service update is installed. If
you attempt to install software products or service
updates without the required prerequisite software,
a system message displays the names of required
prerequisite software. Contrast with dependent.
presentation address. An unambiguous name
that is used to identify a set of presentation service
access points. Loosely, it is the network address of
an OSI service. See also address.
Presentation Service Access Point (PSAP).
Address of an OSI communications partner. It
addresses an application in a computer.
presentation space. An array that contains the
data and attributes associated with a window.
preservation installation. An installation method
used when a previous version of BOS is installed
on your system and you want to preserve the user
data in the root volume group. However, this
method overwrites the /usr, /tmp, /var,and /(root)
file systems, so any user data in these directories
is lost. System configuration must be done after
doing a preservation installation.
Preventive Maintenance Package (PMP). A
maintenance level update for your system. A PMP
includes updates for the Base Operating System
(BOS) and for each optional software product that
is installed on your system.
primary. An irreducible unit of data. For example, a
single constant, variable, or array element.
Primary Enterprise Systems Connection
Manager. In multiple ESCM environments, the
source of ESCM commands.
primary expression. An identifier, parenthesized
expression, function call, array element
specification, structure member specification, or
union member specification.
primary group. In concurrent groups, the group
that is assigned to the files that you create.
primary language. The primary locale you want
your system to use for screen information.
primary navigation article. The general, top–level
unit of software documentation.
primary representation. The form in which the
service supplies an attribute value to the client.
primary selected text. A text group selected as a
primary target or destination, especially text
selected within a text field that can be passed to a
function. Also, the first block of text specified in a
function or statement. See also primary selection.
primary selection. In AIXwindows, the text
selected in a widget. The primary selection has a
value retrieved by the XmTextGetSelection
function. See also primary selected text.
primary slow poll. A technique used by primary
link stations to reduce nonproductive polling of a
secondary link station.
primary station. (1.) On a point–to–point channel,
the station that gains control of the channel first.
On a multipoint channel, the station controlling
communications. (2.) In high level data link control
(HLDC), the part of a data station that supports the
primary control functions of the data link, generates
commands for transmission, and interprets
received responses. (3.) In SNA, the station on an
SDLC data link that is responsible for control of the
data link. There can be only one primary station on
a data link. All traffic over the data link is between
the primary station and a secondary station.
prime file. In Pascal, a file containing precompiled
declarations in the internal table format of the
Pascal compiler. Prime files are used to initialize
the internal tables of the compiler before
compilation begins.
primitive. A drawing command, such as arc, line,
circle, polygon, or charstr. Such commands are
called primitives because they are not made up of
smaller parts, and because they are the basic
pieces out of which more complex scenes can be
composed. Also used to describe the figures
created by drawing commands.
Primitive. In Enhanced X-Windows, the Primitive
class provides the resources and functionality for
the low–level widgets that are managed by the
manager class. Primitive class widgets cannot
have normal child widgets but they can have
pop–up child widgets.
primitive coordinates. The space in which a
primitive is defined. A convenient point is chosen
as the origin and the primitive is defined relative to
this point. Synonym for primitive space. See also
eye coordinates, screen coordinates, and world
coordinates.
primitive font. A font in which characters are
defined as primitives. Like all other primitives,
Glossary
1-117
primitive font characters can be scaled and rotated.
See also raster font and font.
primitive space. Synonym for primitive
coordinates.
primitive widget. In Enhanced X-Windows, a
widget that instantiates its own children of a known
class and does not expect external clients to do so.
Primitive widgets do not have general geometry
management methods. Primitive widgets that
instantiate children are responsible for all
operations requiring downward traversal below
themselves. See also widget.
principal identifier. The name used to identify a
principal uniquely.
Print Manager. In CDE, a software application that
shows all the printers on your system.
print queue. A file containing a list of the names of
files waiting to be printed.
print server. In CDE, a host computer to which
one or more printers are connected, or the UNIX
process that manages those printers.
printer. A device externally attached to the system
unit, used to print system output on paper.
Printer control. In CDE, the Front Panel control
used to start the Printer software application.
Dropping a file on the control displays a dialog box
you can use to print the file to the default printer.
Printer Jobs. In CDE, a software application that
provides information about jobs on a single printer.
printer session. A 3270 Host Connection Program
2.1 and 1.3.2 for AIX (HCON) mode of operation
during interaction with a host computer that
emulates a 3286/87 printer.
printing device. Any printer or other device that
prints, such as a typewriter–like device or a plotter.
printout. Information from the computer produced
by a printer.
priority. (1.) A rank assigned to a task that
determines its precedence in receiving system
resources, the CPU in particular. (2.) The relative
significance of one job to other jobs in competing
for allocation of resources. The importance or
urgency of a process.
priority number. A number that establishes the
relative priority of printer requests.
priority value. A number maintained by the
scheduler for each process that indicates the
priority of that process. The smaller the priority
value of the process, the higher its priority.
1-118
Glossary
privacy. A protection level that may be specified in
secure RPC communications and that encrypts
RPC argument values.
private. A private member of a C++ class is only
accessible to member functions and friends of that
class.
private object. (1.) In XDS, an OM object created
in a workspace using the object management
functions. (2.) In XOM, an object that is
represented in an unspecified fashion.
private part. For Ada programming, see package.
private type. In Ada language, a type whose
structure and set of values are clearly defined, but
not directly available to the user of the type. A
private type is known only by its discriminants (if
any) and by the set of operations defined for it. A
private type and its applicable operations are
defined in the visible part of a package, or in a
generic formal part. Assignment, equality, and
inequality are also defined for private types, unless
the private type is limited.
privileged instructions. System control
instructions that can only run in the processor’s
privileged, or supervisor, state. Privileged
instructions generally manipulate virtual machines
or the memory manager and are not used
ordinarily by application programmers. See also
privileged state.
privileged state. A hardware protection state in
which the processor can run privileged instructions.
Contrast with unprivileged state. See also
privileged instructions.
privileged user. A user logged into an account
with root user authority.
problem determination. The process of identifying
the source of a problem. Often this process
identifies programs, equipment, data
communications facilities, or user errors as the
source of the problem.
problem determination procedure. A prescribed
sequence of steps aimed at recovery from, or
circumvention of, problem conditions.
Problem Management Record (PMR). A number
assigned by a support center to a reported
problem.
problem state. (1.) One of two virtual machine
protection states that run in the unprivileged state
of the processor. User–written application
programs typically run in the problem state. (2.) A
state during which the processing unit cannot run
input/output and other privileged instructions.
procedure. (1.) See shell procedure. (2.) In a
programming language, a block, with or without
formal parameters, that is initiated by means of a
procedure call. (3.) The description of the actions
taken to solve a problem. (4.) A set of related
control statements that cause one or more
programs to be performed. (5.) Synonym for
function. (6.) For Ada programming, see
subprogram.
procedure address. The location of a particular
program procedure in the AIXwindows Toolkit.
process. (1.) A sequence of actions required to
produce a desired result. (2.) An entity receiving a
portion of the processor’s time for running a
program. (3.) An activity within the system that is
started by a command, a shell program, or another
process. When a program is running, it is called a
process. (4.) In a computer system, a unique, finite
course of events defined by its purpose or by its
effect, achieved under given conditions. (5.) Any
operation or combination of operations on data. (6.)
In the operating system, the current state of a
program that is running. This includes a memory
image, the program data, variables used, general
register values, the status of opened files used,
and the current directory. Programs running in a
process must be either operating system programs
or user programs. See also job.
process accounting. An analysis of how each
process uses the processing unit, memory, and I/O
resources.
process concurrency. The degree to which a
given process has multiple dispatchable threads at
all times.
process group. Each process in the system is a
member of a process group that is identified by a
process group ID. This grouping permits the
signaling of related groups of processes. A newly
created process joins the process group of its
creator.
process ID (PID). A unique number assigned to a
process that is running.
process image. See new–process image.
process lock. Allows the calling process to lock or
unlock both its text and data segments into
memory.
process pacing. See pacing.
process table. A kernel data structure that
contains relevant information about all processes in
the system.
processing agent. A thread within an application
server that handles remote procedure calls from
clients.
processing unit. A functional unit within a
computer that is responsible for a certain aspect of
processing.
processor affinity. The degree to which a thread
is likely to be dispatched to the same physical
processor on which it last ran.
product. A software product is made up of
software packages that are separately installable.
product ID. An integer that identifies a vendor’s
licensed software product; by means of product
IDs, the license server distinguishes among
products of the same vendor.
product password. A string encoded with
information about licenses for a software product.
Product passwords are of two types: license
passwords and compound passwords.
profile. (1.) A file containing customized settings
for a system or user. (2.) Data describing the
significant features of a user, program, or device.
(3.) In security, a description of the characteristics
of an entity to which access is controlled. (4.) A
description of the control available to a particular
network operator. See also customization profile
and mapping.
program. (1.) A file containing a set of instructions
that conform to a particular programming language
syntax. (2.) A sequence of instructions suitable for
processing by a computer. Processing can include
the use of an assembler, compiler, interpreter, or
translator to prepare the program for running, and
to run it. (3.) In programming languages, a logical
assembly of one or more interrelated modules. In
Ada language, a program is composed of a
number of compilation units, one of which is a
subprogram called the main program. Execution of
the program consists of execution of the main
program, which may invoke subprograms declared
in the other compilation units of the program. (4.)
To design, write, and test computer programs.
program assertion. A mathematical statement
used in attempts to verify program corrections. In
the graphics operating system, the assert
subroutine tests program assertions.
program counter. A register in the processing unit
that guides the computer through the program.
Synonym for instruction address register.
Glossary
1-119
program fault management (PFM). A subsystem
of NCS that allows a user to set up cleanup
routines when an application does not successfully
complete.
Program Initialization Parameters (PIP). Data
passed to a program when it starts running. This
data modifies the actions taken by that program or
the environment in which that program runs.
program level. The version, release, modification,
and fix levels of a program. See also fix number,
modification number, release number, version,
background, and version number.
program stack. Synonym for invocation stack.
program temporary fix (PTF). A temporary
solution to, or bypass of, a defect in a current
release of a licensed program.
program text. The part of a program that is able to
be run. See text.
program–text segment. A virtual–memory
segment that contains the executable instructions
of an application program. A program–text
segment is identified by the occurrence of an
instruction–cache miss in that segment.
program unit. A main program or a subprogram.
In Ada programming, a program unit is any one of
a generic unit, package, subprogram, or task unit.
Synonymous with module. See also segment unit.
programmable character set (PCS). A geometric
text font. Synonymous with stroke text. See also
geometric text.
programmable input/output operation. The
transfer of data between the processor and an I/O
device or memory address space as part of an I/O
instruction. The I/O instruction designates the
address of the control logic, the command to be
performed and the processor register location into
or from which the data is transferred.
programmable terminal. (1.) A user workstation
that has computational capabilities. (2.) A
workstation that can be programmed to performed
user–determined functions.
programmatic interface. In AIXwindows, an
application created in such a manner that it will
operate in a multiclient environment with other
applications running concurrently. Clients
communicate with the window manager through
Xlib calls or libraries built upon Xlib.
Programmers’ Hierarchical Interactive Graphics
System (PHIGS). An ANSI and ISO standard.
PHIGS defines an application programming
interface designed for interactive two–dimensional
1-120
Glossary
and three–dimensional graphics applications using
retained data structures.
PROM. Programmable read–only memory.
prompt. A displayed symbol or message that
requests information or operator action.
propagation time. The time necessary for a signal
to travel from one point to another on a
communications line.
property. (1.) In Enhanced X-Windows, the name,
type, data format, and data associated with a
window. By using properties, clients and a window
manager share information, such as resize hints,
program names, and icon formats. It is a
general–purpose naming mechanism for clients.
The protocol does not interpret properties. (2.)
Public information (that is, information available to
any client) that is associated with a window.
property list. In Enhanced X-Windows, the list of
properties that are defined for a particular window.
protected. A protected member of a C++ class is
accessible to member functions and friends of that
class, or member functions and friends of classes
derived from that class.
protected field. A displayed field in which a user
cannot enter, modify, or erase data.
protection. An arrangement for restricting access
to or use of all or part of a computer system.
protection level. The degree to which secure
network communications are protected.
protocol. (1.) In SNA and SNA Services, the
meaning of, and the sequencing rules for, requests
and responses used for managing a network,
transferring data, and synchronizing the states of
network components. (2.) A set of semantic and
syntactic rules that determines the behavior of
functional units in achieving communication. (3.) A
mutually agreed–upon mechanism for
communicating between clients to accomplish
certain actions.
protocol boundaries. The set of SNA verbs
supported by SNA Services LU6.2.
protocol family. A set of related communications
protocols; for example, the Department of Defense
Internet Protocols. All members of a protocol family
use a common addressing mechanism to identify
end points. Synonymous with address family. See
also socket address.
protocol port. A unique host identifier used by
transport protocols to specify a destination within a
host.
prototype file. The first file in a new file system
that contains tokens. These include the name of
the bootstrap program, the size of the created file
system, and the specifications of the root file.
PTN. See public telephone network.
proxy object. In DSOM, a SOM object in the
client’s address space that represents a remote
object. The proxy object has the same interface as
the remote object, but each method invoked on the
proxy is overridden by a dispatch method that
forwards the invocation request to the remote
object. Under DSOM, a proxy object is created
dynamically and automatically in the client
whenever a remote method returns a pointer to an
object that happens to be remote. See also object
reference.
PU. See physical unit.
pruning. In GL, eliminating the drawing of parts of
the display list because a bounding box test shows
that they are not visible. See also culling.
P(S). In X.25 communications, the packet send
sequence number.
PSAP. See Presentation Service Access Point.
PSDN (packet–switching data network) . A
PSDN is an interconnecting set of switching nodes
that enables subscribers to exchange data using a
standard protocol and packet–switching
technology. Such a network carries messages
divided into packets over circuits that are shared by
many network users. A single physical line into an
office can handle many concurrent connections.
pseudo device. A software–based device; for
example, a pty device.
Pseudo–PostScript. A graphics language, similar
to PostScript, used to drive output of text and
graphics.
pseudo terminal (PTY). A special file in the /dev
directory that effectively functions as a keyboard
and display device to software that uses the
Berkeley line discipline. A pseudo terminal consists
of a pair of character devices, referred to as the
”master” and ”slave.” The slave device (/dev/pts) is
manipulated by another process through the
master half (/dev/ptc) of the pseudo terminal.
pseudocolor. In Enhanced X-Windows, (1.) A
class of color map in which a pixel value indexes
the color map entry to produce independent red,
green, and blue values. That is, the color map is
viewed as an array of triples (RGB values). The
RGB values can be changed dynamically. This is
mutually exclusive to the direct color color map
class. (2.) Also PseudoColor, a value.
PSN. See public switched network.
PSTN. See public switched telephone network.
PTT. Post, Telegraph, and Telephone authority.
PTY. See pseudo terminal.
public. A public member of a C++ class is
accessible to all functions.
public data network (PDN). A communications
common carrier network providing data
communications services over switched or
nonswitched lines.
public directory. In BNU, the directory
(/var/spool/uucppublic) that is open to all BNU
users. The public directory is used to transfer files
and programs among systems linked by BNU or
other versions of the UNIX–to–UNIX Copy Program
(UUCP).
public node. Any node that does not run Monitor
system components or servers. For example, client
applications run on public nodes.
public switched network (PSN). A
communications service through which users can
be connected by dialing specific service address
numbers.
public switched telephone network (PSTN). A
communications common carrier network that
provides voice and data communications services
over switched lines.
public telephone network (PTN). A
communications common carrier network that
provides voice and data communications services
over switched or nonswitched lines.
puck. A device used to select a particular location
on a tablet.
pull installation. In the Network Installation
Management environment, an installation that is
initiated from a target.
pulldown. The manner in which a MenuPane
widget gives the appearance of being ”pulled
down” from a MenuBar widget as the result of
some user action (usually clicking a mouse button).
pulldown menu. A type of MenuPane widget that
gives the appearance of being ”pulled down” from
a MenuBar widget as the result of some user
action (usually clicking a mouse button).
pure virtual function. A virtual function is declared
pure by replacing the function definition with ’=0;’.
purported name. A construct that is syntactically a
name, but that has not yet been shown to be a
valid name.
PTF. See program temporary fix.
Glossary
1-121
push. A term used when a module is inserted in a
stream immediately below the stream head.
push button. A rounded–corner rectangle with text
inside. Push buttons are used in dialog boxes for
actions that occur immediately when the push
button is selected.
push installation. In the Network Installation
Management environment, an installation that is
initiated from a machine other that the target.
push permissions. Permissions that enable
remote execution of commands.
pushable module. A module between the stream
head and the driver. A driver is a non–pushable
module and a stream head includes a
non–pushable module.
PUT. Program update tape.
1-122
Glossary
PUT 2.0 or PUT 2.1. In SNA, a peripheral node that
has limited addressing and path control routing
capabilities. A PUT 2.0 node depends on subarea
nodes (PUT 4 and PUT 5) to translate between its
local addressing and network addressing. PUT 2.0
does not support the full capabilities of LU6.2; PUT
2.1 does. SNA Services operates only as either a
PUT 2.0 or a PUT 2.1 peripheral node.
PUT 4 or PUT 5. A subarea node that provides
network–wide addressing and control data flow
within a subarea (the subarea node and all
peripheral nodes connected to it). PUT 4 does not
contain an SSCP component; PUT 5 does. SNA
Services cannot perform the functions of a PUT 4
or a PUT 5 subarea node.
PVC. See permanent virtual circuit.
Q
Q–bit. In X.25 communications, the bit in a data
packet that can be set by the sending DTE to
qualify the user data in some way that is
meaningful to the receiving DTE.
qdaemon. The daemon process that maintains a
list of outstanding jobs and sends them to the
specified device at the appropriate time.
QIC. Quarter–inch cartridge.
QID. Queue identifier.
QLLC. See qualified logical link control.
qualified class name. Any class name or class
name qualified with one or more :: (scope)
operators.
qualified expression. In Ada language, an
expression preceded by an indication of its type or
subtype. Such qualification is used when, in its
absence, the expression might be ambiguous (for
example as a consequence of overloading).
qualified logical link control (QLLC). A data link
control protocol that enables SNA–to–SNA
communications over an X.25 network.
quantization. The subdivision of the range of
values of a variable into a finite number of
nonoverlapping, but not necessarily equal intervals.
Each interval is represented by an assigned value.
quantum. A subrange in quantization.
quark. In Enhanced X-Windows, synonym for
string.
query. (1.) The action of searching data for
desired information. (2.) In data communications,
the process by which a master station asks a slave
station to identify itself and to give its status. (3.) In
interactive systems, an operation at a workstation
that elicits a response from the system. (4.) A
request for information from a file based on specific
conditions.
queue. (1.) A line or list formed by items waiting to
be processed. (2.) To form or arrange in a queue.
queue device. A logical device defining
characteristics of a physical device attached to a
queue.
queue element. A block of data or an item in a
queue.
queue stanza. Defines a queue for one or more
devices to which jobs can be queued.
qualified name. (1.) A name made unique by the
addition of one or more qualifiers. (2.) A data name
explicitly accompanied by a specification of the
class to which it belongs in a specified
classification system. (3.) In C++, used to qualify a
nonclass type name such as a member by its class
name.
queued I/O devices. Devices (keyboard, mouse,
button, dials) whose changes are recorded in the
event queue.
qualified type name. Used to reduce complex
class name syntax by using typedefs to represent
qualified class names.
quit. A key, command, or action that tells the
system to return to a previous state or stop a
process.
qualifier. (1.) A unique name used to identify
another name. (2.)A modifier that makes a name
unique. (3.) All names in a qualified name other
than the rightmost, which is called the simple
name.
quote. To mask the special meaning of certain
characters, causing the characters to be taken
literally.
qualifier bit. See Q–bit.
quality of service negotiation. An optional
CCITT–specified facility.
quiet system. A system on which no processes
are running other than the process whose
performance is being timed, and from which all
communications devices have been disconnected.
QWERTY keyboard. A keyboard having the
standard keyboard layout. The term is derived from
the sequence of the first six keys in the first row of
alphabetic keys. See also AZERTY keyboard.
Glossary
1-123
individual key value for which all matching records
should be selected in a nonunique index.
R
race condition. For the signal subroutine, the
condition in which the signal occurs while the signal
action is set to the SIG_DFL value, and the
signal–catching function has not yet established
itself as the catcher for this signal.
radio box. Special configuration of toggle buttons
within a row column manager widget.
radio button. Indicates a fixed set of choices. Only
one of the buttons in the set can be selected at a
time. A circle with text beside it. The circle is
partially filled when a choice is selected.
radio frequency interference. A signal (noise)
that is radiated or conducted from one electronic
circuit or device the may cause incorrect operation
interference in another electronic circuit or device.
An electronic circuit or device can be an emitter of
electromagnetic interference (EMI) or susceptible
to electromagnetic interference.
raise. To make the stacking order of a window
higher.
raising an exception. For Ada programming, see
exception.
RAM. Random access memory. Specifically, the
memory used for system memory. Sometimes this
memory is referred to as main storage.
random access. An access mode in which records
can be read from, written to, or removed from a file
in any order.
random file access. Location of a record that
matches a specific index key value. Random
access of the records in a file requires that the file
have a unique index and that each record have a
unique index key value.
range. In Ada language, a contiguous set of values
of a scalar type. A range is specified by giving the
lower and upper bounds for the values. A value in
the range is said to belong to the range.
range constraint. In Ada language, a range
constraint of a type specifies a range, and thereby
determines the subset of the values of the type that
belong to the range.
range of a DO loop. Those statements that
physically follow a DO statement, up to and
including the final statement specified by the DO
statement.
range of records. Multiple records to be
processed sequentially. A range of records is
selected by specifying key values that bound the
records to be selected, or by specifying an
1-124
Glossary
raster. The area of the video display that is
covered by sweeping the electron beam of the
display horizontally and vertically. Normally the
electronics of the display sweep each line
horizontally from top to bottom and return to the top
during the vertical retrace interval. See also frame
buffer.
raster font. A font in which the characters are
defined directly by the raster bit map. See also font
and primitive font.
raster graphics. Computer graphics in which a
display image is composed of an array of pixels
arranged in rows and columns.
raster mosaics. An area in annotated text fonts
that contains a definition for each character in the
font.
raster subsystem. That part of the system
concerned with an image after it has been
transformed and scaled to screen coordinates. It
includes scan conversion and display.
raw device. A device that treats data I/O as a
continuous stream, without consideration for the
data’s logical structure. For example, I/O for fixed
disks and streaming tapes occurs in units of bytes
that have no relationship to characters.
raw I/O. Character–oriented access to a block
device not utilizing in–core buffers.
raw tape device. See raw device.
RC. Routing control.
RCM. (1) See real–time control microcode. (2)
Rendering Context Manager.
RCS. See Revision Control System.
RD. Receive Data used with EIA–232 protocol.
read access. An access right that grants the ability
to view CDS data.
read–only file. Pertaining to file system mounting,
a condition that allows data to be read but not
copied, printed, or modified.
Read Only Storage (ROS) menus. The menus
displayed by system ROS on a target. Information
used in booting the target is provided by the user to
the ROS menus.
read queue. A message queue in a module or
driver containing messages moving upstream.
Associated with input from a driver.
readers and writers. In the SOM Replication
Framework, different processes can access the
same replicated object in different modes. A
”reader” is a process that does not intend to update
the object, but wants to continually watch the object
as other processes update it. A ”writer” is a process
that wants to update the object, as well as
continually watch the updates performed by others.
real constant. A string of decimal digits that
expresses a real number. A real constant must
contain either a decimal point, a decimal exponent,
or both.
real device. The actual device hardware.
real group ID. For each user, the group ID defined
in the password file.
real memory. The active physical memory on any
system. Contrast with virtual memory.
real number. (1.) A number that contains a
decimal point and is stored in fixed–point or
floating–point format. (2.) A number that can be
represented by a finite or infinite numeral in a
fixed–radix numeration system.
real operation. Any operation on Ada
floating–point or fixed–point values.
real page number. This field in the translation
control word (TWC) contains the real page address
that the bus address is mapped to in system
memory.
real storage. Storage directly accessible to the
processor from which instructions can be run and
from which instructions can fetch data.
real time. (1.) The time elapsed between the
loading of a program and its completion. (2.)
Pertaining to the processing of data by a computer
in connection with another process outside the
computer, according to time requirements imposed
by the outside process. (3.) Used to describe
systems that operate in conversational mode and
processes that can be influenced by human
intervention while in progress. (4.) Pertaining to an
application, such as a process control system or a
computer–assisted instruction system, in which
response to input is fast enough to affect
subsequent input.
real–time control microcode (RCM). In X.25
communications, the microcode that runs on the
X.25 Interface Co-Processor/2 to provide control
functions.
real–time system. A system that receives and
processes data so the data or result is available for
immediate use.
real type. (1.) An arithmetic data type that can
approximate the values of real numbers. (2.) In
Ada language, a real type is a type whose values
represent approximations to the real numbers.
There are two kinds of real type: fixed point types
are specified by absolute error bound; floating point
types are specified by a relative error bound
expressed as a number of significant decimal
digits.
real user ID. (1.) Identifies the user who was
authenticated the last time the login command or
su command was used. (2.) For each user, the
user ID that is specified in the /etc/passwd file.
realm. A cell, considered exclusively from the point
of view of security; this term is used in Kerberos
specifications.
rebinding. Reestablishing a communications
channel for making remote procedure calls after
that channel has been closed.
reboot. To reinitialize the execution of a program
by repeating the initial program load (IPL)
operation.
REC. See Lock Service.
receive. In X.25 communications, to take an
incoming packet (such as an incoming–call packet
or a data packet) from the buffer.
receive pacing. In SNA, the pacing of message
units that a component is receiving. Contrast with
send pacing. See also pacing.
receive time out. In data communications, a
condition that occurs when no data is received in a
given period of time.
recognized private operating agency (RPOA). A
private X.25 network that can optionally be
selected by the user at call setup time to carry the
X.25 traffic.
Recommendation X.25. See X.25.
record. (1.) In programming languages, an
aggregate that consists of data objects, possibly
with different attributes, that usually have identifiers
attached to them. (2.) A set of data treated as a
unit. (3.) A collection of fields treated as a unit. See
also class record, widget record, and instance
record.
record lock. A lock that prevents some or all of a
file from being written to or read. See also lock.
record name. A data name for a record described
in a record description entry.
record type. (1.) The classification of records in a
file. (2.) In Ada language, a value of a record type
consists of components are usually of different
types or subtypes. For each component of a record
value or record object, the definition of the record
type specifies an identifier that uniquely determines
the component within the record.
Glossary
1-125
recording instrument. In Performance Toolbox,
an instrument with the ability to show the statistics
for a system resource over a period of time.
Recording instruments typically have a time scale
with the current time to the right. The values plotted
are moved to the left as new readings are received.
Types of graphs used to plot these recordings
include line, area, skyline, and bar graphs. Contrast
with state instrument.
recoverable data. Data whose values persist
across system shutdowns and failures. Changes
made to recoverable data are permanent
regardless of system problems. Logging changes
to recoverable data is the most common method
used to ensure permanence. The changes to that
data recorded in the log can always be replayed to
bring that data to a valid state.
recovery procedure. (1.) An action performed by
the operator when an error message appears on
the display screen. This action usually permits the
program to continue or permits the operator to run
the next job. (2.) The method of returning the
system to the point where a major system error
occurred and running the recent critical jobs again.
(3.) A process in which a specified data station
attempts to resolve conflicting erroneous conditions
arising during the transfer of data.
rectangle. A rectangle specified by [x,y,w,h]
has an infinitely thin outline path with corners at
[x,y][x+w,y][x+w,y+h] and [x,y+h] . In
XGSL , when a rectangle is filled, the lower–right
edges are not drawn. For example, if w=h=0,
nothing would be drawn; if w=h=1, a single pixel
would be drawn.
recurring attribute. An attribute with several
attribute values.
recursion. (1.) Using a function to define itself. (2.)
Performing an operation in several steps, with each
step using the output of the preceding step.
redirect. To divert data from a process to a file or
device to which it would not normally go.
redirecting control. Transferring an operation to a
specified client. Used when window managers or
client programs enforce window layout policy to
prevent attempts to change the size or position of a
window.
redispatch stub. In SOM, a procedure,
corresponding to a particular method, which has
the same signature as the method’s procedure but
which invokes somDispatch to dispatch the
method. The somOverrideMtab method can be
used to replace the procedure pointers in a class’s
method table with the corresponding redispatch
stubs. This is done when overriding somDispatch
to customize method resolution so that all static
1-126
Glossary
method invocations will be routed through
somDispatch for selection of an appropriate
method procedure. (Dynamic methods have no
entries in the method table, so they cannot be
supported with redispatch functionality.)
Reduced Instruction Set Computer (RISC). A
class of computer designs that uses a relatively
small set of frequently used instructions that
execute in one cycle.
reentrant service. A service that is safe to call
from multiple threads in parallel. If a service is
reentrant, there is no burden placed on calling
routines to serialize their access or take other
explicit precautions. See also thread–serial service,
and thread–synchronous service.
refer. A bibliographic preprocessor for the nroff
and troff commands. ”Refer” is designed for
literature citations, and it supports data entry,
indexing, sorting, retrieval, printing, citations, and
either footnote or endnote numbering.
reference bit. A bit in each page frame table entry
that denotes that the corresponding page has been
accessed (either read from or written to) since the
last time the operating system cleared the page.
reference count. In an i–node, a record of the total
number of directory entries that refer to the i–node.
reference data. In SOM, application–specific data
that a server uses to identify or describe an object
in DSOM. The data, represented by a sequence of
up to 1024 bytes, is registered with DSOM when a
server creates an object reference. A server can
later ask DSOM to return the reference data
associated with an object reference. See also
object reference.
reference monitor. Code that controls access to
an object.
reference widget. The parent widget that
searched for children satisfied the search criteria.
refresh rate. The rate at which the monitor is
refreshed. A 60 Hz monitor is redrawn 60 times per
second. Synonymous with vertical retrace.
region. An area within a bitmap, a pixmap, a
screen, or a window.
Region. An arbitrary set of pixel locations. The Xlib
library provides subroutines for manipulating
regions. The opaque type Region is defined in the
<X11/Xutil.h> header file.
register. (1.) A storage device having a specified
storage capacity such as a bit, byte, or computer
word, and that is usually intended for a special
purpose. See also general purpose register. (2.) In
NCS, to make an interface known to the RPC run
time library and, thereby, available to clients
through the RPC mechanism. The rpc_$register
call registers an interface. (3.) In NCS, to enter an
object and its location in the Location Broker
database. The lb_$register call registers an object
with the Location Broker. A program can use
Location Broker lookup calls to determine the
location of a registered object.
registration. The creation of an object in the
network installation database that uniquely
identifies a client, network, or resource in the
network installation environment to the master
server.
Registry database. A database of information
about persons, groups, organizations, and
accounts.
regular expression. (1.) A set of characters, meta
characters, and operators that define a string or
group of strings in a search pattern. (2.) A string
containing wildcard characters and operations that
define a set of one or more possible strings.
Contrast with literal string. See also collating
element and subpattern.
reject. To cause portions of applied updates from
becoming permanent parts of the product, based
on the results of a test period. When you reject an
applied service update, the update’s files are
deleted and the software vital product data
(SWVPD) information is changed to indicate that
the update is no longer on the system. The
previous version of the software, if there is one, is
restored and becomes the active version of the
software. Contrast with apply and commit.
relational expression. (1.) A logical statement that
describes the relationship (such as greater than or
equal) of two arithmetic expressions or data items.
(2.) An expression that consists of an arithmetic
expression followed by a relational operator,
followed by another arithmetic expression, and that
can be reduced to a value that is true or false.
relational operator. (1.) The reserved words or
symbols used to express a relational condition or a
relational expression. (2.) An operator that
compares two operands and yields a Boolean
value.
relational transformation. A transformation that
changes an arithmetic relational expression into the
negation of its logical complement. For example, a
relational transformation of A>B is NOT(A<=B).
relative address. (1.) An address specified relative
to a base address. (2.) An address counted relative
to a symbol. When a program is relocated, the
addresses themselves change, but the relative
addresses remain the same.
relative directory. A directory whose name begins
with a ./ (dot and a slash).
Relative Distinguished Name (RDN). A set of
Attribute Value Assertions (AVAs), each of which is
true, concerning the distinguished values of a
particular entry.
relative drawing commands. In computer
graphics, commands that draw relative to the
current graphics position as opposed to being
drawn at absolute locations.
relative file. A file organized as an array of
fixed–length slots. Records can be inserted in the
first free slot found from the beginning or end of the
file, or can be explicitly positioned in a certain slot
in the file, identified by its relative slot number
(RSN).
relative path name. The name of a directory or file
expressed as a sequence of directories followed by
a file name, beginning from the current directory.
Relative path names do not begin with a / (slash)
but are relative to the current directory. See also
path name and full path name.
relative record number. A number that expresses
the location of a record in relation to a base
position in the file containing it.
relative slot number (RSN). The number of the
slot occupied by a record in a relative file. The RSN
is part of the user’s data record. Each record in a
relative file contains a field that holds its RSN.
relative time. A discrete time interval that is
usually added to or subtracted from an absolute
time.
release number. The release level of a program,
which is an indicator of changes to the external
programming interface of the program. The
version, release, modification, and fix levels
together comprise the program level or version of a
program. See also fix number, modification
number, version number, program level and
version.
release update package. A set of selective
enhancements, filesets, and new versions of
optional software products available since the last
release of the operating system. Also included is a
maintenance level package for each software
package.
reliable stream delivery. A type of packet delivery
that allows an application program on one machine
to connect to an application program on another
machine. The stream actually contains many
packets of data that are sent one at a time to the
receiving machine.
Glossary
1-127
relocatable. (1.) A value, expression, or address
that does not have to be changed when the
program is relocated. (2.) Attribute of a set of
codes whose address constants can be altered to
make up for a change in origin.
remote. Pertaining to a system or device that is
accessed through a communications line. Contrast
with local.
remote access data processing. Synonym for
teleprocessing.
remote connection. A communications link
between the local system and a remote system or
device.
remote host. Any host on the network except the
one at which a particular operator is working.
Synonymous with foreign host.
remote job entry (RJE). Submission of a job
through an input unit that has access to a computer
through a data link.
remote login. Initiating a session on a system that
is accessed through a communications line.
remote pacing. Pacing generated by the remote
system attempting to control the output of the local
system. See also pacing.
remote print. Issuing print jobs to one machine
(client) to print on another machine (server) on a
network.
remote procedure call (RPC). The calling of a
remote operation between processes on different
hosts or on the same host.
Remote Procedure Call run–time library. The set
of rpc_$ system calls that NCS provides to
implement a remote procedure call mechanism.
Remote Statistics Interface (RSi). In
Performance Toolbox, the Manager API which
allows an application program to access statistics
from remote nodes (or the local host) through a
network interface.
remote system. A system that is connected to
your system through a communication line.
remote transaction program name (RTPN). The
name of a transaction program at the other
(remote) end of a conversation.
removable storage device. Any storage device
defined during system configuration to be an
optional part of the system DASD. A removable
storage device can be removed from the system
anytime during normal operation.
remove. For a software option, the deletion of the
option and all of its applied or committed updates
from the system. The software vital product data
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Glossary
(SWVPD) information is changed to indicate that
the option has been removed from the system.
Depending on the option, system configuration
information is also cleaned up, although this is not
always complete. If a previous version, release, or
level of the option is on the system, the system will
not restore the previous version. Only an option
with its updates can be removed. Updates cannot
be removed by themselves. Contrast with commit.
renaming declaration. In Ada language, declares
another name for an entity.
render. To create an image on a visual display
from data that describes the scene.
rendezvous. In Ada language, the interaction that
occurs between two parallel tasks when one task
has called an entry of the other task, and a
corresponding accept statement is being executed
by the other task on behalf of the calling task.
repage fault. A page fault on a virtual–memory
page that is known to have been read from disk
”recently.”
reparent. When a widget is moved between
interface windows, it is reassigned to the parent
widget in the new location, and automatically
acquires the inheritable attributes of the new
parent.
repeat factor. In GL, the magnification with which
the linestyle pattern is used.
repetitive tiling operation. In XGSL, an operation
that consists of repeatedly copying a 16x16–pixel
tile rectangle (pointed to by the tile pixel map data
address) to fill a rectangle area of a size specified
by the H and W parameters of this call. The format
defined in the flags field of the tile pixel map
structure defines the format of the tile data.
replica. In SOM, when an object is replicated
among a set of processes (using the Replication
Framework), each process is said to have a replica
of the object. From the view point of any application
model, the replicas together represent a single
object.
reply. (1.) A response to an inquiry. (2.) In SNA, a
request unit sent only in reaction to a received
request unit. For example, Quiesce Complete is the
reply sent after receipt of Quiesce At End of Chain.
(3.) In Enhanced X-Windows, the way information
requested by a client program is sent back to the
client. Both events and replies are multiplexed on
the same connection. Most requests do not
generate replies; some generate multiple replies.
representation clause. In Ada language, a clause
that directs the compiler in the selection of the
mapping of a type, an object, or a task onto
features of the underlying machine that executes a
program. In some cases, representation clauses
completely specify the mapping; in other cases,
they provide criteria for choosing a mapping.
request. (1.) A directive, by means of a basic
transmission unit, from an access method that
causes the network control program to perform a
data–transfer operation or auxiliary operation. (2.)
In SNA, a message unit that signals initiation of an
action or protocol. (3.) In Enhanced X-Windows, a
command to the server to send a single block of
data over a connection. (4.) In text formatting, a
request is a built–in command recognized by the
formatters.
requester. A display station or interactive
communications session that requests a program
to be run.
required list. In Enhanced X-Windows, an ordered
list containing a subset of the installed color maps.
required parameter. A parameter having no value
automatically supplied. The user must provide a
value.
required value. Synonym for required parameter.
requisite. A software product or a service update
that must be installed with another software
product or service update. If you attempt to install
software products or service updates without the
required requisite software, a system message
displays the names of required requisite software.
reserved character. A character or symbol that
has a special (non–literal) meaning unless quoted.
reserved word. A word that is defined in a
programming language for a special purpose, and
that must not appear as a user–declared identifier.
reset. (1.) To cause a counter to take the state
corresponding to a specified initial number. (2.) To
put all or part of a data processing device back to a
prescribed state. (3.) On a virtual circuit,
reinitialization of data flow control. (4.) To return a
device or circuit to a clear state. (5.) In X.25
communications, to reinitialize the flow of control
on a virtual circuit, which eliminates all data that
may be in transit for the virtual circuit at the time of
resetting.
reset cause. See cause code.
reset collision. See collision.
reset–confirmation packet. In X.25
communications, a packet transmitted by the data
terminal equipment (DTE) to inform the data
circuit–terminating equipment (DCE) that a reset
operation has been processed. See also packet.
reset diagnostic. See diagnostic code.
reset packet . A packet used to reset a virtual
circuit at the interface between the data terminal
equipment (DTE) and the data circuit–terminating
equipment.
reset–request packet. In X.25 communications, a
packet used for the resetting of a virtual circuit at
the DTE/DCE interface. See also packet.
resize border. In CDE, a control used to change
the size of a window or a pane in a window.
resolution. The process or capability of making
the individual parts of objects on screen
distinguishable, especially regarding font
generation. The number of dots that can be
displayed on the screen. Used to determine the
clarity of a graphic image.
resolver routine. A kernel process used to resolve
symbolic host names into Internet addresses. The
method the routine uses to resolve names depends
on whether the local network is organized as a flat
network or as a hierarchical network.
resource. (1.) In NIM, any file, directory, file
system, or device that is required to perform a NIM
operation. (2.) In Enhanced X-Windows, items such
as windows, pixmaps, cursors, fonts, graphics
contexts, and color maps are known as resources.
Each has a unique identifier associated with it for
naming purposes. The lifetime of a resource is
bounded by the lifetime of the connection over
which the resource was created. (3.) In Enhanced
X-Windows, a named piece of data in a widget that
can be set by a client, by an application, or by user
defaults. (4.) In AIXwindows and Enhanced
X-Windows, a unique characteristic of appearance
or behavior that is associated with one specific
class of graphical object. Resources can be passed
downward (inherited) by each subclass that is
downstream from a higher–level class in the class
hierarchy.
resource database. The database assembled for
a particular combination of display, host, and
application. It can contain information from several
sources.
resource identifier (rid). In Enhanced X-Windows,
an integer returned to an application program that
identifies a resource that has been allocated for the
program’s use.
resource manager. A component that manages
application data. Resource managers communicate
with application servers.
Glossary
1-129
resource object. A resource used in the Network
Installation Management environment that
represents a file or directory.
resource outage. The inability to obtain the
necessary resources, such as links, buffers, or
control block storage.
resource pair. See resource value.
resource state. A state that indicates that the
resource is either available or unavailable for use.
resource string. A parameter, such as a part of
the program name, that identifies an application’s
resources.
resource value. Resources determine a widget or
window’s operation and attributes, such as color
and behavior. The resource is associated with a
value list that gives the specific values for each
resource. See also attribute.
resource value string. A parameter containing the
default value to be used if a specific resource has
not been set.
response. (1.) An answer to an inquiry. (2.) In
SNA, a message unit that acknowledges receipt of
a request; a response consists of a response
header (RH), a response unit (RU), or both.
response time. (1.)The time it takes for a data
communications system to respond to a request.
For example, if you enter a customer number on a
workstation keyboard, response time begins when
you press the last key and ends when the first
character of your answer is displayed at the
workstation. (2.) The time from the initiation of an
operation until its initiator has enough information
to proceed.
restart–confirmation packet. In X.25
communications, a call supervision packet
transmitted by a DCE to confirm that the link has
been restarted. See also packet.
restart–indication packet. In X.25
communications, a call supervision packet
transmitted by a DCE to indicate to a DTE that a
restart–request has been received.
restart–request packet. In X.25 communications,
a call supervision packet transmitted by a DTE to
request that a link be restarted.
restore. To return to an original value or image; for
example, to restore a library from diskette.
restricted response. In X.25 communications,
when restricted response is specified for a
fast–select call, the call must be cleared; it may not
be accepted.
1-130
Glossary
restricted shell. Shell providing controlled, limited
access to specified users.
result. An entity produced by an operation.
retransmit. To repeat the transmission of a
message or segment of a message.
retrieval time. The time interval required to locate
data in storage and read it for subsequent
processing.
retry. To try the operation that caused the device
error message again.
return code. (1.) A value that is returned to a
program to indicate the results of an operation
issued by that program. (2.) A code used to
influence the running of succeeding instructions.
Synonymous with return value.
return statement. A programming language
control statement that contains the word return
followed by an optional expression and a
semicolon.
return value. Synonym for return code.
reverse charging. In X.25 communications, an
optional facility that allows a DTE to request that
the cost of a call it makes be charged to the called
DTE. See also optional facilities.
reverse video. A form of highlighting a character,
field, or cursor by reversing the color of the
character, field, or cursor with its background. For
example, changing a red character on a black
background to a black character on a red
background.
Revision Control System (RCS). Manages
multiple revisions of text files. Designed to control
frequently revised text, such as programs, form
letters, and papers. It features automatic
identification, storage, logging, retrieval, and
merging of file revisions. See also Source Code
Control System.
revision text. See version identifier.
rewind. To select an earlier item, rather than the
next or current item, from an argument list.
RFC. Request for comments.
RFI. See radio frequency interference.
RGB color. A color value scale that is composed of
the primary values (red, green, and blue).
RGB mode. A configuration of the hardware that
allows values stored in the frame buffer to be
interpreted as packed RGB values. The values
found in the frame buffer are passed directly to the
red, green, and blue guns of the display monitor.
The values are not passed through the color map
first. (However, each color is sent individually
through the gamma ramp to make a final correction
to its intensity.) See also color map mode.
RGB signal. Red/green/blue signal.
RGB value. The set of red, green, and blue
intensities that compose a color is that color’s RGB
value.
RGBA value. In GL, the set of red, green, blue,
and alpha intensities that compose a color. Alpha
values are available only on machines having
alpha bitplanes.
RIC. Realtime interface coprocessor.
rid. See resource identifier.
right–hand rule. If the right hand is wrapped
around the axis of rotation, the fingers curl in the
same direction as positive rotation, and the thumb
points in the same direction as the axis of rotation.
A right–handed rotation is counter–clockwise.
right margin. The area between the rightmost text
character and the right edge of the display or
paper.
ring. (1.) A method used to distribute data in a
LAN. (2.) In FDDI, two or more stations connected
by a physical medium wherein information is
passed sequentially between active stations, each
station is turn examining or copying and repeating
the information, finally returning it to the originating
station. See also ring network.
ring buffer. An application–defined buffer in which
monitor mode input is placed. An application places
data from input devices in the buffer. The ring
buffer mechanism dramatically shortens the input
data path from the input device to the application.
ring network. (1.) A network in which every node
has two branches connected to it. (2.) A network
configuration in which devices are connected by
unidirectional transmission links to form a closed
path. See also ring.
RIP. See Routing Information Protocol.
RISC. See Reduced Instruction Set Computer.
RJE. See remote job entry.
RMT. Ring management.
RNR frame. In X.25 communications, a
receive–not–ready frame. Contrast with RR frame.
RNR packet. In X.25 communications, a
receive–not–ready packet. Contrast with RR
packet.
rolled back. Undoing any modifications performed
on behalf of a transaction which does not complete
(is aborted). Any changes made by a transaction
which is aborted, for whatever reason, must be
undone. Once a transaction is rolled back, no
evidence that the transaction was ever attempted
remains outside of records in the transaction
processing system’s log. See also abort.
roller ball. The sphere inside a mechanical mouse
that contacts a desktop or other hard surface.
ROM. Read–only memory.
Roman font. The ordinary type style. In many
typefaces, this is the default font, governing most
text. It most often is used to turn off italics or
boldface.
Roman numerals. Numbers formed from
traditional combinations of Roman letters, either
uppercase (I, II, III, IV, and so on) or lowercase (i,
ii, iii, iv, and so on). See also Arabic numerals.
root. (1.) The user name for the system user with
the most authority. (2.) In Enhanced X-Windows,
(a.) The screen on which the window is created.
The root of a pixmap or GContext is the same as
the root of the drawable used when the pixmap or
GContext was created. The root of a pixmap or
graphics context is the same as the root of
whatever drawable was used when the pixmap or
graphics context was created. The root of a window
is the root window under which the window was
created. (b.) On the widget tree, the Shell widget
returned by the XtInitialize or
XtCreateApplicationShell subroutine. (3.) In
AIXwindows, the Shell widget is the root of the
widget tree hierarchy that is maintained within any
given application interface. See also widget tree.
root device. The device on which the root file
system resides.
root directory. The directory (/) that contains all
other directories in the system.
root file system. The basic file system, onto which
all other file systems can be mounted. The root file
system contains the operating system files that get
the rest of the system running.
root segment. (1.) In an overlay operation, the
part of a program that must remain in main storage
when other overlay segments are run; the first
segment of a program with overlays. The root
segment remains in main storage at all times while
the program is being run. (2.) In a hierarchical
database, the highest segment in the tree
structure.
Glossary
1-131
root user. The person who has unrestricted ability
to access and modify any part of the operating
system, usually the user who manages the system.
See also root user authority.
row–major order. A way of storing array elements
such that the rightmost subscript varies most
rapidly as memory–adjacent elements are
accessed.
root user authority. The unrestricted ability to
access and modify any part of the operating
system, usually associated with the user who
manages the system. See also root user.
RPC. See remote procedure call.
root volume group (rootvg). A volume group
containing the Base Operating System (BOS). See
also migration installation.
RPOA. See recognized private operating agency.
root window. In a graphics environment, each
screen has a root window covering it. This window
cannot be reconfigured or unmapped, but
otherwise performs like any other window. A root
window has no parent.
ROS. Remote Operation Service.
ROSE. Remote Operation Service Elements.
rotation. In computer graphics, the transformation
of a primitive by rotating it about an axis. See also
transformation.
route. A path defined for sending data across a
network.
routine. A set of statements in a program causing
the system to perform an operation or a series of
related operations. See also macro and subroutine.
routing. (1.) The assignment of the path by which
a message will reach its destination. (2.) In SNA,
the forwarding of a message unit along a particular
path through a network as determined by
parameters carried in the message unit, such as
the destination network address in a transmission
header. (3.) In X.25 communications, the process
by which a packet gets to the intended user.
Routing Information Protocol (RIP). A variant of
the XeroxNS Routing Information Protocol, used to
maintain current kernel routing table entries.
routing list. The list that associates user names
with network user addresses and other information,
for the purpose of directing incoming X.25 calls.
routing table. The table holding a list of valid
paths through which hosts can communicate with
other hosts. The routing table can hold static routes
and dynamic routes.
row. A horizontal arrangement of characters or
other expressions.
row column manager. A widget that contains
toggle buttons or push buttons. It updates its
property that accounts for menu history, which
allows it to determine which toggle button was
selected last.
1-132
Glossary
rpm. Revolutions per minute.
RPN. See real page number.
RPQ. Request for Price Quotation.
RR. (1.) Resource Record (DNS). (2.) Round Robin
(scheduling).
RR frame. In X.25 communications, a
receive–ready frame. Contrast with RNR frame.
RR packet. In X.25 communications, a packet
used by a DTE or by a DCE to indicate that it is
ready to receive data packets within the window.
Contrast with RNR packet.
RS–232C. See EIA–232D.
RS–422A. See EIA–422A.
RSi. See Remote Statistics Interface.
RTI. Response type indicator.
RTPN. See remote transaction program name.
RTS. Ready to Send used with EIA–232 Protocol.
rubber–band outline. A window with a moveable
outline.
rule file. A file containing rules determining the
appearance and behavior of CDE Desktop.
run. (1.) A performance of one or more jobs or
programs. (2.) To cause a program, utility, or other
machine function to be performed.
run file. The output of the linkage editor. A
program file in a format that is suitable for being
loaded into main storage and run. See also
module.
run–time algorithm selection. An optimization
technique in which the parameters to an operation
are evaluated to determine which of several
equivalent algorithms will perform the operation
most efficiently.
run–time checks. Error checking that occurs while
an Ada program runs. If an error is detected, the
program raises an exception.
run–time environment. A collection of subroutines
and shell variables that provide commonly used
functions and information for system components.
run–time monitor. The part of the Monitor that
manages transactional client and server
applications that take input from users and service
requests.
running state. The condition of a machine when
users can login and use the machine.
RW lock. Abbreviation for read shared/write
exclusive lock. Any number of threads can hold the
lock simultaneously for reading, but if a thread
holds the lock for writing, all other threads are
excluded from reading or writing the locked
resource.
Glossary
1-133
S
S–connector. The type of connector used with
super–video. Similar to the Y/C connector. It is a
4–pin–min din–type connector.
S–video. Super–video. Used to improve the quality
of a video image, a technique that maintains
separate Y/C signals before recording on magnetic
tape or displaying on a monitor.
SABM. See set asynchronous balanced mode.
SAK. See secure attention key.
sample rate. Synonym for locator sample rate.
SAP. See service access point.
SAS. Single–attachment station. A station that
connects only to the primary ring by way of a wiring
concentrator or connects to one other SAS in a
back–to–back wiring configuration.
sash. In CDE, a box on a separator or split bar that
enables you to increase or decrease the size of a
window pane using the mouse. You can navigate to
the sash using the keyboard.
satisfy. For Ada programming, see constraint and
subtype.
scaling. (1.) In computer graphics, enlarging or
reducing all or part of a display image by
multiplying the coordinates of the image by a
constant value. (2.) In programming, indicating the
number of digit positions in object code to be
occupied by the fractional portion of a fixed–point
or floating–point constant. (3.) In GL, uniform
stretching of a primitive along an axis.
scaling factor. The throughput of a workload on a
multiprocessor divided by the throughput of that
workload on a comparable uniprocessor (not on a
single–processor SMP system).
scan. (1.) To examine sequentially, part by part.
(2.) To search records for a specified character
string or syntax error.
scan code. Raw input from the keyboard.
scan conversion. The process of generating pixel
information into the frame buffer from an
application program.
scanline. (1.) A list of pixel or bit values viewed as
a horizontal row (all values have the same y
coordinate). The values are ordered by increasing
the x coordinate. As part of an image, the next
scanline is ordered by increasing the y coordinate.
(2.) A visible line produced on a display by one
horizontal sweep of the electron beam of a cathode
ray tube.
saved user ID. The user ID that is acquired when
running a setuid program. The saved user ID is the
same as the owner of the file that ran. If the file that
ran was not setuid, the saved user ID is set to the
effective user ID of the parent.
scanline order. An image represented by
scanlines ordered by increasing the y coordinate.
saveset. A list of window clients that should not be
destroyed when a connection is closed and should
be remapped or unmapped. Usually used by
window managers to avoid lost windows if the
manager is ended abnormally.
scatter. For input and output operations, to read
data from a device and locate it in noncontiguous
memory addresses. Contrast with gather.
scalability. The ability of a workload to benefit from
a multiprocessor environment.
scalar. An arithmetic object or enumerated object.
scalar type. A type that defines a variable
containing a single value at run time. Contrast with
structured type. In Ada programming, an object or
value of a scalar type does not have components.
A scalar type is either a discrete type or a real type.
The values of a scalar type are ordered.
scale. Increments of measure used by the nroff
and troff commands. All supported scales are
converted for the typesetter into a scale called
machine units (u).
scale factor. (1.) A number indicating the position
of the decimal point in a real number. (2.) A
number used as a multiplier in scaling.
1-134
Glossary
scanned image. An image that is examined
sequentially, part by part.
SCCS. See Source Code Control System and
Revision Control System.
SCCS delta. A set of changes made to an SCCS
file. Creating a new delta saves only the changes
made.
SCCS identification (SID). In SCCS, a number
assigned to each version of a program.
scheduling policy. The set of rules that govern
when a thread will lose control of the CPU and
which thread will get control next.
scope. (1.) That part of a source program in which
a variable can communicate its value. (2.) The
portion of a program within which a declaration
applies. For Ada programming, see declaration.
(3.) In SOM, that portion of a program within which
an identifier name has ”visibility” and denotes a
unique variable. In SOM, an IDL source file forms a
scope. An identifier can only be defined once within
a scope; identifiers can be redefined within a
nested scope. In a .idl file, modules, interface
statements, structures, unions, methods, and
exceptions form nested scopes.
scope operator (::). Defines the scope for the right
argument in C++. If the left argument is blank, the
scope is global. If the left argument is a class
name, then the scope is within that class.
scratch file. A file, usually used as a work file, that
exists temporarily, until the end of the program that
uses it.
screen. (1.) See display screen. (2.) In the
extended curses library, a special type of window
that is as large as the workstation screen. (3.) In
Enhanced X-Windows, a server can provide
several independent screens that typically have
physically independent monitors (display screens).
This is the expected configuration when there is
only a single keyboard and pointer shared among
the screens. A screen structure contains the
information about that screen and is linked to the
display structure.
screen capture. The storage of a screen display
as a text or graphics file on disk.
screen coordinates. The coordinate system that
defines the display screen. In GL, distances are
measured in units of pixels, and the origin is in the
lower left–hand corner. On most systems the
screen size is 1024 pixels high by 1280 pixels
wide. The viewport defines the mapping from
normalized device coordinates to screen
coordinates. Synonymous with screen space. See
also eye coordinates, primitive coordinates,
modeling coordinates, world coordinates, and
transformation.
screen lock. In CDE, a function that locks the
workstation screen, barring further input until the
valid user password is entered.
Screen Saver. In CDE, a choice that, after a
specified time period, switches off the workstation
display or varies the images that are displayed,
thereby prolonging the life of the screen.
screen space. Synonym for screen coordinates.
screenmask. In GL, a rectangular area of the
screen to which all drawing operations are clipped.
It is normally set equal to the viewport and to the
window. A screenmask is useful for character
clipping. See also clipping.
script file. In the Ada debugger, a file that contains
a series of commands that can be used to drive the
debugger. Script files are useful for debugging
large, complex programs when you may not be
able to complete a debugging session in one
sitting.
scroll. To move text vertically or horizontally in
order to view information that is outside the display
or pane boundaries.
scroll bar. The horizontal and vertical bars in the
border of a directory window that allow you to scroll
the files to see what is beyond the border of the
window. A graphical device consisting of a slider,
scroll area, and scroll arrows. A user changes the
view by sliding the slider up or down in the scroll
area or by pressing one of the scroll arrows. This
causes the view to scroll up or down in the window
adjacent to the scroll bar.
scroll region. In AIXwindows, the rectangular
portion of a ScrollBar widget that contains two
arrows and a slider.
scrolled list. A list that is scrolled. See also scroll.
scrolled text. Text that is scrolled. See also scroll.
scrolling. The horizontal or vertical movement of
graphic or text information presented on a display
screen.
SCSI Adapter. See Small Computer Systems
Interface Adapter.
sdb. See symbolic debugger.
SDLC. See synchronous data link control.
SDLC primary station. A station that has
responsibility for the data link. It issues commands
to secondary stations.
SDLC secondary station. A station that responds
to requests from another station (the primary
station) and has little control over data link
operations.
SDT. See static debugger trap.
seal. To encrypt a record containing several fields
in such a way that the fields cannot be modified
without either knowledge of the encryption key or
leaving evidence of tampering.
search. The action of scanning a set of data
elements to locate all instances of a particular item,
such as a text string or a file name.
search loop. An array–processing loop used to
perform a table lookup or to find exceptional values
within an array.
SECAM. A national television industry
broadcasting standard used in France, USSR, and
some other countries. See also NTSC and PAL.
second–level interrupt handler (SLIH). A
device–dependent routine that handles the
Glossary
1-135
processing of an interrupt from a specific adapter.
An SLIH is called by the first–level interrupt handler
(FLIH) associated with that interrupt level.
secondary key. A key field of a record that defines
a secondary index.
secondary representation. A second form, an
alternative to the primary representation, in which
the client may supply an attribute value to the
service.
secondary station. A data station that runs data
link control functions as instructed by the primary
station. It interprets received commands and
generates responses for transmission.
secondary unit. In Ada language, the body of a
library unit (such as a subprogram body, package
body, generic body, or subprogram body) or a
subunit. All compilation units that are not library
units are secondary units. Secondary units are not
subject to reference by other independently
compiled units and can be thought of as the
hidden implementation of a library unit or separate
declaration.
secondary window. A window of short duration
such as a dialog box. The window is only displayed
for a short time, usually just long enough to convey
some information or get some operational
directions.
section. In the vi editor, text that follows a section
heading as defined by the sect= option.
sector. (1.) The smallest amount of information
that can be written to or read from a disk or
diskette during a single read or write operation. (2.)
On disk or diskette storage, an addressable
subdivision of a track used to record one block of a
program or data.
secure attention key (SAK). A key sequence that
ends all processes associated with a terminal to
provide a trusted path for secure communication
with the TCB. The SAK sequence is Ctrl–x followed
by Ctrl–r.
secure node. A node that is capable of running
one or more application servers and one or more
Monitor system components, normally a highly
trusted machine.
security. The protection of data, system
operations, and devices from accidental or
intentional ruin, damage, or exposure.
seek pointer. A data structure that contains the
offset of the current location in a character file or
device.
segment. (1.) A contiguous area of virtual storage
allocated to a job or system task. A program
segment can be run by itself, even if the whole
1-136
Glossary
program is not in main storage. (2.) Virtual memory
is divided into segments that are
linearly–addressable spaces of one or more
4KB–byte pages up to a maximum size of 2 to the
28th power bytes. (3.) The information that can be
addressed via a single, unique segment–register
value (256MB). (4.) A portion of a computer
program that can be run as an entity without the
entire program being maintained in system
memory. (5.) A group of display elements. (6.) In
Enhanced X-Windows, one or more lines that are
drawn but not necessarily connected at the end
points.
segment flag. The segflag parameter of the
fp_open kernel service that indicates whether the
path parameter is located in user space or in kernel
space.
segment registers. Registers in the system that
hold the actual addresses of the memory segments
currently in use.
segment unit. In Pascal, an independently
compilable piece of code containing routines linked
with the program unit. See also program unit.
segmentation fault. A memory addressing
exception. Occurs when a memory location is
referenced that has not been allocated to the
referencing process. An out–of–bounds array
reference or incorrect use of a pointer can cause a
segmentation fault.
segmenting of BIUs. An optional function of path
control that divides a basic information unit (BIU)
received from transmission control into two or more
path information units (PIUs). The first PIU contains
the request header of the BIU and usually part of
the response unit (RU). The remaining PIU or PIUs
contain the remaining parts of the RU.
select. (1.) To choose a button on the display
screen. (2.) To place the cursor on an object (name
or command) and press the Select (left) button on
the mouse or the Select key on the keyboard. (3.)
To indicate the item or items the next command
you choose will affect. The item may be highlighted
to confirm your selection. Selecting does not
actually carry out the command.
selected component. In Ada language, a name
consisting of a prefix and of an identifier called the
selector. Selected components are used to denote
record components, entries, and objects
designated by access values; they are also used
as expanded names.
selecting. In GL, a method for finding what
primitives are being drawn in a given volume in
three–dimensional space. See also hit, selecting
region, picking, and picking region.
selecting region. In GL, a rhomboid–shaped
volume in world coordinates that is sensitive to
selecting events. If a drawing primitive draws within
this region, a select event is reported. See also hit,
selecting, picking, transformation, and picking
region.
selection. (1.) Addressing a workstation or a
component on a selective calling circuit. (2.) The
process by which a computer requests a station to
send it a message. (3.) See also addressing. (4.) In
Enhanced X-Windows, an indirect property of a
dynamic type maintained by the client (the owner)
but belonging to the user. It is not private to a
particular window subhierarchy or a particular set
of clients. When a client asks for the contents of a
selection, it specifies a target type. This target type
can be used to control the transmitted
representation of the contents.
selection area. In AIXwindows, a portion of a
RowColumn widget over which the mouse pointer
can be placed to select other widgets.
selection criteria. In the select subroutine, the
readlist, writelist, and exceptlist parameter
values that specify what to check for reading,
writing, and exceptions.
selection range. See key range.
selector. (1.) In Pascal, the term in a CASE
statement that, once evaluated, determines which
of the possible branches of the CASE statement
are processed. (2.) For Ada programming, see
selected component.
semantic. The relationships of characters or
groups of characters to their meanings,
independent of the manner of their interpretation
and use.
semantic error. A compile–time error caused by
incorrect definition of constants and identifiers. See
also syntax error.
semaphore. (1.) Entity used to control access to
system resources. Processes can be locked to a
resource with semaphores if the processes follow
certain programming conventions. (2.) Provides a
general method of communication between two
processes that is an extension of the features of
signals.
semaphore ID (semid). An integer that points to a
set of semaphores and a data structure that
contains information about the semaphores.
semid. See semaphore ID.
send pacing. In SNA, the pacing of message units
that a component is sending. Contrast with receive
pacing.
sense code. A value sent or received, or a
negative response to indicate what error occurred.
sentence. In the vi editor, text that is separated
from other text by a . (period), ! (exclamation point),
or ? (question mark) followed by two spaces.
separator. A punctuation character that separates
parts of a command or file, or that delimits
character strings.
sequential access. (1.) An access method in
which records are read from, written to, or removed
from a file based on the logical order of the records
in the file. (2.) The facility to obtain data from or
enter data into a storage device so that the process
depends on the location of the data and on a
reference to data previously accessed.
sequential file access. The location of a range of
records through key values and the subsequent
processing of them in some order related to those
key values. The index of the file need not be
unique.
sequential I/O model. A model of the operating
system for all accesses to system network
resources. When SNA supports this model, it
simplifies access to the network, allows programs
to be designed for portability, and allows programs
to use network resources through redirection.
serial device. A device that performs functions
sequentially, such as a serial printer that prints one
character at a time. Contrast with parallel device.
serial port. A port used for a serial device. See
also serial device.
serial processing. Pertaining to the sequential or
consecutive running of two or more processes in a
single device, such as a channel or processing
unit. Contrast with parallel processing.
serial transmission. Transmitting each bit of a
data character separately over the same electrical
path.
serializability. A basic property of transaction
processing systems, this refers to the idea that the
exchange and modification of information by
transactions must be able to be synchronized and
appear as though multiple, simultaneous
transactions are actually a series of sequential
requests. Data being changed by a transaction, or
upon which a transaction depends, must be
shielded from other transactions until the first
transaction completes.
serialize. (1.) To change from parallel–by–byte to
serial–by–bit. (2.) In XDR, to convert a particular
machine representation to XDR format.
Glossary
1-137
server. (1.) An application program that usually
runs in the background (daemon) and is controlled
by the System Program Controller. (2.) On a
network, the computer that contains the data or
provides the facilities to be accessed by other
computers on the network. (3.) A program that
handles protocol, queuing, routing, and other tasks
necessary for data transfer between devices in a
computer system. (4.) In Enhanced X-Windows,
provides the basic windowing mechanism. It
handles IPC connections from clients,
de–multiplexes graphics requests onto screens,
and multiplexes input back to clients. (5.) In NCS, a
process that exports one or more interfaces to one
or more objects, and whose procedures can be
invoked from remote hosts. (6.) In DSOM, a
process, running in a distributed environment, that
executes the implementation of an object. DSOM
provides a default server implementation that can
dynamically load SOM class libraries, create SOM
objects, and make those objects accessible to
clients. Developers can also write
application–specific servers for use with DSOM.
server grabbing. When a client seizes the server
for exclusive use to prevent processing requests
from other client connections until the grab is
complete. This is typically a transient state for such
things as rubber–banding and pop–up menus or to
run requests indivisibly.
server object. In DSOM, every server has an
object that defines methods for managing objects
in that server. These methods include object
creation, object destruction, and maintaining
mappings between object references and the
objects they reference. A server object must be an
instance of the class SOMDServer (or one of its
subclasses). See also object reference and
SOMDObject.
server reporting. A protocol for servers to report
to the cell manager contact by previously unknown
clients, for the purpose of registration.
service access point (SAP). In the Ethernet
logical link profile, the address for the transaction
program on the local system. This address is a
hexadecimal value.
service controls. A group of parameters, applied
to all directory operations, that direct or constrain
the provision of the service.
service mode. Synonym for maintenance mode.
service request number (SRN). A group of
numbers used by service technicians to determine
the failing area of the system.
service transaction program. (1.) A program that
provides a function internal to SNA Services. (2.) A
transaction program implemented by a transaction
1-138
Glossary
processing system. Service transaction programs
perform such functions as providing access to
remote data bases and remote queues. See also
application transaction program and transaction
program.
service update. Software that corrects a defect in
or adds new function to the Base Operating
System (BOS) or to an optional software product.
See also maintenance level update.
session. (1.) The period of time during which
programs or devices can communicate with each
other. (2.) A name for a type of resource that
controls local LUs, remote LUs, modes, and
attachments. (3.) In network architecture, an
association of facilities that establish, maintain, and
release connections for communication between
stations. (4.) The period of time during which the
user of a workstation can communicate with an
interactive system, usually elapsed time between
login and logoff. (5.) In SNA, a logical connection
between two network addressable units (NAUs)
that can be activated, tailored to provide various
protocols, and deactivated as requested. (6.) In
remote communications, a period of
communication with a remote system or host
system.
session date. The date associated with a session.
See also creation date and system date.
session key. Used in Kerberos specifications. See
also conversation key.
session–level pacing. In SNA, a flow control
technique in which a receiving half–session
controls the data transfer rate (the rate at which it
receives request units). It is used to prevent
overloading a receiver with unprocessed requests,
when the sender can generate requests faster than
the receiver can process them.
Session Manager. In CDE, a software application
that controls saving sessions, restoring sessions,
screen locking and unlocking, and the use of
screen savers. When a session is saved, the state
of the desktop environment (location of icons, size
and location of open windows, open/closed status
of applications, current color palette, and so on) is
preserved so that it can be restored at the next
login.
session profile. For the 3270 Host Connection
Program 2.1 and 1.3.2 for AIX, a profile describing
the characteristics of a session between a client
system and a System/370 host computer. See also
3270 Host Connection Program 2.1 and 1.3.2 for
AIX and profile.
session records. In the accounting system, a
record (produced from log in and log off records) of
time connected and line usage for connected
display stations.
Shadowing is accomplished by using the macro
SOM_SubstituteClass.
session server. In CDE, a system that provides
networked sessions. Session files reside on the
session server and are used whenever you log in
to a system on the network.
shared library. A library created by the ld
command that contains at least one subroutine that
can be used by multiple processes. Programs and
subroutines are linked as before, but the code
common to different subroutines is combined in
one library file that can be loaded at run time and
shared by many programs. A key to identify the
shared library file is left in the header of each
subroutine.
set. In NCS, to associate an allocated Remote
Procedure Call (RPC) handle with a specific socket
address. See also bind.
set–associative cache. A cache in which two or
four (or more) lines correspond to each possible
value of the virtual–address field that identifies the
line to be interrogated during cache lookup.
set associativity. An aspect of cache design that
determines how many cache lines can be
associated with a given memory location. A cache
that is four–way set associative can contain a given
memory location in one of four cache lines. See
also cache line.
set asynchronous balance mode (SABM). A link
control frame.
set flags. Flags that can be put into effect with the
shell set command.
set–group–ID mode bit. In setting file access
permissions, sets the effective and saved group
IDs of the process to the group ID of the file on
execution.
set–user–ID mode bit. In setting file access
permissions, sets the effective and saved user IDs
of the process to the owner ID of the file on
execution.
setgid. See set–group–ID mode bit.
setuid. See set–user–ID mode bit.
severity code. A code that indicates how serious
an error condition is.
shadow. A darkened area below a window and to
its right, or above it and to its left, which represents
the shadow a window might cast.
shadow color. The shaded area around or behind
a dialog box.
shadow widget. An opaque pointer to a structure
created each time a widget is created; it identifies
the widgets in the interface. Also called swidget.
shadowing. In the SOM Emitter Framework, a
technique that is required when any of the entry
classes are subclassed. Shadowing causes
instances of the new subclass(es) (rather than
instances of the original entry classes) to be used
as input for building the object graph, without
requiring a recompile of emitter framework code.
shared locks. Shared locks are a type of lock in
which multiple transactions can simultaneously lock
a data item for reading. See also exclusive lock.
shared memory. An area of memory
simultaneously accessible to more than one
cooperating process.
shared memory ID (shmid). An identifier assigned
to the shared segment for use within a particular
process. See also file descriptor.
shared port. A port used by communications
applications (for example, UUCP) to ensure
exclusive access to a port.
Shared Product Object Tree (SPOT). (1.) A
version of the /usr file system that diskless clients
mount as their own /usr directory. (2.) For NIM, a
/usr file system or an equivalent file system that is
exported by servers in the NIM environment for
remote client use.
shell. (1.) A software interface between a user and
the operating system of a computer. Shell
programs interpret commands and user
interactions on devices such as keyboards,
pointing devices, and touch–sensitive screens and
communicate them to the operating system. (2.)
Software that allows a kernel program to run under
different operating system environments. (3.) The
command interpreter that provides a user interface
to the kernel. See also shell program and
command interpreter. Synonymous with interface.
(4.) A shell is a command interpreter that acts as
an interface between users and the operating
system. A shell can contain another shell nested
inside it, in which case, the outer shell is the parent
shell and the inner shell is the child. (5.) In
AIXwindows, Shell widgets are top–level widgets
that are internal and cannot be instantiated, but
they provide the necessary interface with the
window manager. See also shell widget.
shell box. A geometry management technique
where a type of bounding box can have only one
child that is exactly the same size as the shell.
Glossary
1-139
shell command names. Operating–system
commands.
divided by the elapsed time, representing a rate
per second.
shell control command. A command that enables
the user to pass control to various parts of a shell
procedure, or to control how a procedure ends.
SID. SCCS identification. The name assigned to a
delta.
shell procedure. A series of commands, combined
in a file, that carry out a particular function when
the file is run or when the file is specified as a value
to the sh command. Synonymous with shell script.
shell program. A program that accepts and
interprets commands for the operating system.
Synonym for shell.
side effect. An undesirable result caused by
altering the values of nonlocal variables by a
procedure or function.
sign–off. To end a session at a display station.
sign–on. To begin a session at a display station.
shell script. Synonym for shell procedure.
signal. (1.) A simple method of communication
between two processes. One process can inform
the other process when an event occurs. (2.) In
operating system operations, a method of
inter–process communication that simulates
software interrupts. Contrast with exception and
interrupt.
shell variables. Facilities of the shell program for
assigning variable values to constant names.
signal handler. A subroutine called when a signal
occurs.
shell widget. In Enhanced X-Windows, holds the
top–level widgets that communicate directly with
the window manager. These widgets do not have
parents. Synonymous with shell. See also widget.
signal mask. Defines the set of signals currently
blocked from delivery to a process.
shell prompt. The character string on the
command line indicating that the system can
accept a command (typically the $ character).
shielded twisted pair. A transmission medium of
two twisted conductors with a foil or braid shield.
Shift–Japanese Industrial Standard (SJIS). An
encoding scheme consisting of single bytes and
double bytes used for character encoding. Because
of the large number of characters in Japanese and
other Asian languages, the 8–bit byte is not
sufficient for character encoding.
shmid. See shared memory ID.
short. In ODM, a terminal descriptor type used to
define a variable as a signed 2–byte number. See
also terminal descriptor.
short circuiting. The evaluation of Boolean
expressions with AND and OR such that the right
operand is not evaluated if the result of the
operation can be determined by evaluating the left
operand. The evaluation of the expression is
always from left to right.
short status. Status output in abbreviated form
(short form) from the spooling subsystem.
shortest–job–next (SJN). A method of queueing
jobs where the shortest jobs are printed first.
Contrast with first–come–first–served. See also
discipline.
signal stack. An alternate stack on which signals
are to be processed.
signature. In SOM, the collection of types
associated with a method (the type of its return
value, if any, as well as the number, order, and type
of each of its arguments).
signed. Information is digitally signed by
appending to it an enciphered summary of the
information. This is used to ensure the integrity of
the data, the authenticity of the originator, and the
unambiguous relationship between the originator
and the data.
Simple Mail Transfer Protocol (SMTP). A
protocol, typically used over a network, in which the
objective is to transfer mail. SMTP is used by the
sendmail command to accept and receive mail.
simple name. For Ada programming, see
declaration and name.
simultaneous peripheral operation online. See
spooling.
single buffer mode. . In GL, a mode in which the
frame buffer bitplanes are organized into a single
large frame buffer. This frame buffer is the one
currently displayed and is also the one in which all
drawing occurs. See also double buffer mode.
sibling. Children of the same parent window.
single–byte control codes. ASCII codes 0
through 31 (0x00 through 0x1f) and delete (0x7f).
SiCounter. In Performance Toolbox, a value that is
incremented continuously. Instruments show the
delta (change) in the value between observations,
single–mode optical fiber. An optical fiber in
which only the lowest–order bound mode (which
can consist of a pair of orthogonally polarized
1-140
Glossary
fields) can propagate at the wavelength of interest.
Contrast with multimode optical fiber.
single–precision. (1.) The use of one computer
word to represent a number, in accordance with the
required precision. (2.) The specification that
causes a floating–point value to be stored in the
short format. See also precision.
single–processor SMP. A system designed to
handle two or more processors, running the SMP
version of the operating system, which has been
configured with a single processor. Contrast with
uniprocessor.
single–shift control. In codepage switching,
control codes that shift to another page for a single
character; nonlocking shifts.
SiQuantity value. In Performance Toolbox,
represents a level, such as memory used or
available disk space. The actual observation value
is shown by instruments.
sister class object. In SOM, a duplicate of a class
object that is created in order to save a copy of the
class’s original method table before replacing the
method table to customize method resolution. The
sister class object is created so that some original
method procedures can be called by the
replacement method procedures.
size. The screen management action that changes
the size of a window.
size field. In an i–node, a field that indicates the
size, in bytes, of the file associated with the i–node.
SJIS. See Shift–Japanese Industrial Standard.
SJN. See shortest–job–next.
skew. The time difference between two clocks or
clock values.
SLA. Serial Link Adapter. See also SOCC.
sleeping process. A process that is waiting for
input or output to complete, time slices, an event to
occur, or signals from other processes. When a
process is sleeping, it can be paged out of memory.
slider. (1.) In AIXwindows, a small interactive
graphical object connected to an XmScrollBar bar
widget. The slider controls the vertical or horizontal
movement of text information or graphics across
the display screen. (2.) A control that uses a track
and arm to set a value from among the available
values. The position of the arm (or a separate
indicator) gives the currently set value.
SLIH. See second–level interrupt handler.
SLIP. Serial Line Interface Protocol. The protocol
that TCP/IP uses when operating through a serial
connection.
slot. A long electrical socket inside the system unit
into which an electronic circuit board (card) is
installed.
slow list. A list of secondary stations on a
multidrop network that, due to their inactivity, are
polled less often by the primary station.
small caps. See caps.
Small Computer Systems Interface Adapter
(SCSI Adapter). An adapter that supports the
attachment of various direct–access storage
devices and tape drives to the system unit.
small word. In the vi editor, a contiguous set of
alphanumeric characters bounded on at least one
end with a character that is not a blank, a tab, or a
new–line indicator. For example, in the word isn’t,
the two sets of characters isn and t are small
words. Contrast with big word.
SMIT. System Management Interface Tool.
SMP. See symmetrical multiprocessor system.
SMP efficient. Avoidance in a program of any
action that would cause functional or performance
problems in an SMP environment. A program that
is described as SMP efficient is generally assumed
to be SMP safe as well. An SMP–efficient program
has usually undergone additional changes to
minimize incipient bottlenecks.
SMP exploiting. Adding features to a program that
are specifically intended to make effective use of
an SMP environment. A program that is described
as SMP exploiting is generally assumed to be SMP
safe and SMP efficient as well.
SMP safe. Avoidance in a program of any action,
such as unserialized access to shared data, that
would cause functional problems in an SMP
environment. This term, when used alone, usually
refers to a program that has undergone only the
minimum changes necessary for correct
functioning in an SMP environment.
SMT. Station management.
SMTP. See Simple Mail Transfer Protocol.
SNA. See System Network Architecture.
SNA network. The part of a user–application
network that conforms to the formats and protocols
of System Network Architecture (SNA). It enables
reliable transfer of data among end users and
provides protocols for controlling the resources of
various network configurations. The SNA network
consists of network addressable units (NAUs),
boundary–function components, and the path
control network.
SNBU. See switched network backup.
Glossary
1-141
SNMP. Simple Network Management Protocol. A
protocol used by network hosts to exchange
information in the management of networks. SNMP
network management is based on the client–server
model that is widely used in TCP/IP–based network
applications.
SNOBOL. A programming language designed for
string processing and pattern matching.
SOCC. Serial Optical Channel Converter. A
220–Mbit/sec optical point–to–point link.
social science format. See natural or social
science format.
socket. (1.) A unique host identifier created by the
concatenation of a port identifier with a TCP/IP
address. (2.) A port identifier. (3.) A 16–bit port
number. (4.) In NCS, a port on a specific host; a
communications end point that is accessible
through a protocol family’s addressing mechanism.
A socket is identified by a socket address. See also
socket address, port, and listening.
socket address. A data structure that uniquely
identifies a specific communications end point. A
socket address consists of a port number and a
network address. It also specifies the protocol
family. See also protocol family.
Sockets class. A SOM class that provides a
common communications interface to Distributed
SOM, the Replication Framework, and the Event
Management Framework. The Sockets class
provides the base interfaces (patterned after
TCP/IP sockets); the subclasses TCPIPSockets,
NBSockets, and IPXSockets provide actual
implementations for TCP/IP , Netbios, and Netware
IPX/SPX, respectively.
software. Programs, procedures, rules, and any
associated documentation pertaining to the
operation of a system. Contrast with hardware.
software configuration. The processing required
to make installed software ready to use.
software installation. The process of restoring
software from external media to a local file system.
The software can require further processing, or
configuration, before it is ready to use.
software keyboard. A table mapping a raw
keystroke to a display symbol, predefined function
or string. Software keyboards that are shipped with
the operating system are associated with
languages (U.S. English, U.K. English, Danish,
Japanese, and so on).
software keyboard map. A table that maps a
keystroke to a character or to a predefined function
such as a tab.
1-142
Glossary
Software Vital Product Data (SWVPD).
Information that uniquely defines system,
hardware, software, and microcode elements of a
processing system.
SOM. See System Object Model.
SOM Compiler. A tool provided by the SOM Toolkit
that takes as input the interface definition file for a
class (the .idl file) and produces a set of binding
files that make it more convenient to implement
and use SOM classes.
SOM–derived metaclass. See derived metaclass.
SOMClass. One of the three primitive class objects
of the SOM run–time environment. SOMClass is
the root (meta)class from which all subsequent
metaclasses are derived. SOMClass defines the
essential behavior common to all SOM class
objects.
SOMClassMgr. One of the three primitive class
objects of the SOM run–time environment. During
SOM initialization, a single instance (object) of
SOMClassMgr is created, called
SOMClassMgrObject. This object maintains a
directory of all SOM classes that exist within the
current process, and it assists with dynamic loading
and unloading of class libraries.
SOMDObject. The SOM class that implements the
notion of a CORBA ”object reference” in DSOM. An
instance of SOMDObject contains information
about an object’s server implementation and
interface, as well as a user–supplied identifier. See
also object reference.
somId. In SOM, a pointer to a number that
uniquely represents a zero–terminated string. Such
pointers are declared as type somId. In SOM,
somId’s are used to represent method names,
class names, and so forth. See also method ID.
SOMOA (SOM object adapter) class. In DSOM, a
class that dispatches methods on a server’s
objects, using the SOM Compiler and run–time
support. The SOMOA class implements methods
defined in the abstract BOA class (its base class).
See also BOA class and ORB (object request
broker).
SOMObject. One of the three primitive class
objects of the SOM run–time environment.
SOMObject is the root class for all SOM
(sub)classes. SOMObject defines the essential
behavior common to all SOM objects.
somSelf. In SOM, within method procedures in the
implementation file for a class, a parameter
pointing to the target object that is an instance of
the class being implemented. It is local to the
method procedure.
spaces for future addition of data. See also hole in
a file
somThis. In SOM, within method procedures, a
local variable that points to a data structure
containing the instance variables introduced by the
class. If no instance variables are specified in the
SOM IDL source file, then the somThis assignment
statement is commented out by the SOM Compiler.
SPC. See System Program Controller.
sort. To rearrange some or all of a group of items,
based upon the contents or characteristics of those
items.
source. (1.) A system, a program within a system,
or a device that makes a request to a target.
Contrast with target. (2.) In advanced
program–to–program communications, the system
or program that starts jobs on another system.
source code. The input to a compiler or
assembler, written in a source language. Contrast
with object code.
Source Code Control System (SCCS). A program
for maintaining version control for the source files
of a developing program. It stores the changes
made to a file instead of the changed file, thus
allowing several versions of the same file to exist in
the system. See also Revision Control System.
source documents. Verbal information produced
concurrently with the original software, by the
original development company.
source file. A file that contains source statements
for such items as high–level language programs
and data description specifications. A file
containing input data or commands.
source module. See source program.
source program. A computer program expressed
in a source language.
source statement. A statement written in a
programming language.
space. (1.) A site intended for storage of data,
such as a location in a storage medium. (2.) A
basic unit of area, usually the size of a single
character. (3.) One or more space characters. (4.)
In a neutral circuit, an impulse that causes the loop
to open or causes absence of signal. In a polar
circuit, it causes the loop current to flow in a
direction opposite to that for a mark impulse. A
space impulse is equal to a binary zero.
sparse array. An array in which few of the defined
cells are used.
sparse file. A file that is created with a length
greater than the data it contains, leaving empty
special character. A character other than a letter
or number. For example, *, +, and % are special
characters.
special file. Used in the operating system to
provide an interface to input/output devices. There
is at least one special file for each device
connected to the computer. Contrast with directory
and file. See also block file and character special
file.
specific. The attribute types that may appear in an
instance of a given class, but not in an instance of
its superclasses.
specification statement. In FORTRAN, one of the
set of statements that provide the compiler with
information about the data used in the source
program and how to allocate storage.
specifiers. Used in C++ declarations to indicate
storage class, fundamental data type, and other
properties of the object or function being declared.
speed. The baud rate. Synonym for line speed.
SPI. Stub programming interface. A private RPC
runtime interface whose routines are unavailable to
application code.
spill area. A storage area used to save the
contents of registers.
Spmi. See System Performance Measurement
Interface.
spool file. (1.) A disk file containing output that has
been saved for later printing. (2.) Files used in the
transmission of data among devices.
spooler. A synonym for the queueing system that
pertains to its use for queueing print jobs.
spooling (simultaneous peripheral operation
online). (1.) The use of auxiliary storage as a
buffer storage. This reduces processing delays
when transferring data between peripheral
equipment and the processors of a computer. (2.)
Reading and writing input and output streams on
an intermediate device in a format convenient for
later processing. (3.) Performing a peripheral
operation such as printing while the computer is
busy with other work.
SPOT. See Shared Product Object Tree.
SPP. Sequence packet protocol. The primary
transport–layer protocol in the Xerox Network
Systems. It provides reliable, flow–controlled,
Glossary
1-143
two–way transmission of data for an application
program. It is a byte–stream protocol used to
support the SOCK_STREAM abstraction. The SPP
protocol uses the standard Network System (NS)
address formats.
spring–loaded pop–up. A kind of widget, such as
a menu, that is not visible to the window manager.
The spring–loaded pop–up disables user–event
processing except for events that occur in the
menu.
SRC. System Resource Controller.
SRF. Standard record format.
SRN. See Service request number.
SRT. See Structure Rule Table.
SSCP. See system services control point.
stack. (1.) An area in storage that stores
temporary register information and return
addresses of subroutines. (2.) A list constructed
and maintained so that the last data element stored
is the first data element retrieved. (3.) In kernel
mode, an area that is paged with the user process.
The kernel maintains a stack for each process. It
saves the process information such as the call
chain and local variables used by the kernel for the
user process.
stack buffer. A storage area that stores retrievable
data in sequence. The last text stored is the first
text removed.
stack overflow. An error condition in DOS that
results from an insufficient number of stack frames,
which are used by DOS to handle hardware
interrupts.
stack pointer. A register providing the current
location of the stack.
stack traceback. The calling sequence that
indicates the path taken by a process to get to its
current location.
stacked tape. A bootable tape with multiple
software images.
stacking order. The relationship between sibling
windows that stack on top of each other.
stage. One of a series of steps to enter a ged
subcommand that typically ends with < cr >
(carriage return). Each subcommand consists of a
subset of stages, including command line, text,
points, pivot, and destination.
standalone. A machine in the network installation
environment that accesses all required resources
locally.
standalone shell. A limited version of the shell
program used for system maintenance.
1-144
Glossary
standalone system. See standalone workstation.
standalone workstation. A workstation that can
perform tasks without being connected to other
resources such as servers or host systems.
standard error (STDERR). The place where many
programs place error messages.
standard input (STDIN). The primary source of
data going into a command. Standard input comes
from the keyboard unless redirection or piping is
used, in which case standard input can be from a
file or the output from another command.
Standard I/O Board. The Standard I/O Board
provides a group of I/O functions that are basic to
most system units. Common standard I/O functions
are keyboard, tablet, speaker, mouse, serial port,
parallel port and diskette adapter.
standard output (STDOUT). The primary
destination of data coming from a command.
Standard output goes to the display unless
redirection or piping is used, in which case
standard output can be to a file or another
command.
standard screen. In the extended curses library, a
memory image of the screen to which the routines
make changes.
standout mode. The general–purpose highlighting
mechanism used by the terminfo structure.
stanza. A group of lines in a file that together have
a common function or define a part of the system.
Stanzas are usually separated by blank lines or
colons, and each stanza has a name.
start method. Takes the device from the stopped
state to the available state. The start method
applies only to devices that support the optional
stopped state.
start–stop. Asynchronous transmission in which a
group of signals representing a character is
preceded by a start element and followed by a stop
element. See also asynchronous transmission.
startup set. A grouping of application servers that
can be thought of as a single unit for administration
purposes.
state. (1.) A state in which the circuit remains until
application of a suitable pulse. (2.) One of the
separate, restartable portions into which the
runacct command (the main daily accounting shell
procedure) breaks its processing. (3.) In SOM, the
data (attributes, instance variables and their
values) associated with an object. See also
behavior.
state information. Information about the current
state of the appearance and behavior of a widget
or gadget. This information is recorded within each
individual widget and gadget and updated as
necessary.
state instrument. In Performance Toolbox, a state
instrument shows the latest statistics for a system
resource, optionally as a weighted average. While
it does not show the statistics over time, some
state instruments collect this data in case you want
to change the instrument to a recording instrument.
Types of graphs used to plot these recordings
include state bar, state light, pie chart, and
speedometer. Contrast with recording instrument.
statement. (1.) An instruction in a program or
procedure. (2.) In programming languages, a
language construct that represents a step in a
sequence of actions or a set of declarations. See
also block statement. In Ada language, a statement
specifies one or more actions to be performed
during the execution of a program.
statement function. In FORTRAN, a name,
followed by a list of dummy arguments, that is
equated to an arithmetic, logical, or character
expression, and that can be substituted for the
expression throughout the program. See also
macro.
statement function definition. In FORTRAN, a
statement that defines a statement function. Its
form is a statement function followed by = (equal
sign) followed by an arithmetic, logical, or character
expression.
statement label. In FORTRAN, a number
containing one to five decimal digits that is used to
identify a statement. A statement label is usually
used to transfer control, define the range of a DO
loop, or refer to a FORMAT statement. See also
label.
statement number. See statement label.
static. (1.) A style of creating pop–ups. (2.) In C++,
a keyword used for defining the scope and linkage
of variables and functions. For internal variables,
the variable has block scope and retains its value
between function calls. For external values, the
variable has file scope and retains its value within
the source file. For class variables, the variable is
shared by all objects of the class and retains its
value within the entire program.
static binding. Binding that occurs at compilation
time based on the resolution of overloaded
functions.
static debugger trap (SDT). A trap instruction
placed in a predefined point in code that calls the
debug program. The trap instruction causes a
program check when run and, as a result of the
program check, the debug program is activated.
static display. In text formatting, when the nroff
command finds a block of text in the input file that
has been specified as a static display, it places the
text on the current page only if there is room for the
entire block. If there is not enough room, the nroff
command starts a new page and places the block
of text there. See also floating display.
static linking. Linking of a program in which library
procedures are incorporated into the load module,
instead of being dynamically loaded from their
library each time the program is run.
static memory. Allocated memory of fixed size.
static method. In SOM, any method that can be
accessed through offset method resolution. Any
method declared in the IDL specification of a class
is a static method. See also method and dynamic
method.
static routing. A method of setting paths between
hosts, networks, or both by manually entering
routes into the routing table. Static routes are not
affected by routing daemons and must be updated
manually.
static variable. A variable that is allocated as soon
as a program starts running and that remains
allocated until the program stops. Normal scoping
rules apply to the variable. Contrast with automatic
variable.
station. (1.) A computer or device that can send or
receive data. (2.) An input or output point of a
system that uses telecommunication facilities, such
as one or more systems, computers, workstations,
devices, and associated programs at a particular
location that can send or receive data over a
telecommunication line. (3.) A location on a device
at which an operation is performed. (4.) In FDDI,
an addressable logical and physical attachment in
a ring capable of transmitting, receiving, and
repeating information. (5.) In SNA, a link station.
statistic line. In Performance Toolbox, the lines in
a list that represent a specific value. Contrast with
context line.
status. (1.) The current condition or state of a
program or device. For example, the status of a
printer. (2.) The condition of the hardware or
software, usually represented in a status code. (3.)
In Enhanced X-Windows, many Xlib subroutines
return a success status. If the subroutine does not
succeed, however, its values are not disturbed.
STDERR. See standard error.
STDIN. See standard input.
STDOUT. See standard output.
steal (a page frame). The act (by the Virtual
Memory Manager) of reallocating a real–memory
Glossary
1-145
page frame that contains a virtual–memory page
that is being used by a currently executing
program.
sticky bit. An access permission bit that causes an
executable program to remain on the swap area of
the disk. Only someone with root authority can set
the sticky bit. This bit is also used on directories to
indicate that only file owners can link or unlink files
in that directory.
stipple. A bitmap used to tile a region. A stipple
pattern serves as an additional clip mask for a fill
operation with the foreground color.
stop bit. (1.) In start–stop transmission, a signal at
the end of a character that prepares the receiving
device for reception of a subsequent character. (2.)
A signal to a receiving mechanism to wait for the
next signal.
stop method. Takes the device from the available
state to the stopped state. The stop method applies
only to devices that support the optional stopped
state.
stop record. In Performance Toolbox, a special
type of value record which signals that recording
was stopped for a set of statistics and gives the
time it happened. This allows programs using the
recording file to distinguish between gaps in the
recording and variances in the recording interval.
stopped state. Allows a device to be made
unavailable but still have its device driver loaded
and bound in the kernel and still be known by the
device driver.
storage. (1.) The location of saved information. (2.)
In contrast to memory, the saving of information on
physical devices such as disk or tape. See also
memory. (3.) A unit into which recorded text can be
entered, retained, and processed, and from which
it can be retrieved. (4.) The action of placing data
into a storage device.
storage class specifier. A storage class keyword.
One of the following C++ keywords: auto, register,
static, or extern.
storage device. (1.) A functional unit for storing
and retrieving data. (2.) A facility into which data
can be retained.
store. To place information in a storage device (in
memory or onto a diskette, fixed disk, or tape), so
that it is available for retrieval and updating.
stream. (1.) Sequential input or output from an
open file descriptor. (2.) A continuous stream of
data elements being transmitted, or intended for
transmission, using a defined format. (3.) All data
transmitted through a data channel in a single read
or write operation. Synonym for data stream. (4.)
1-146
Glossary
The kernel aggregate created by connecting
STREAMS components, resulting from an
application of the STREAM mechanism. The
primary components are a stream head, a driver,
and zero or more pushable modules between the
stream head and driver. A stream forms a full
duplex processing and data transfer path in the
kernel, between a user process and a driver. A
stream is analogous to a shell pipeline except that
data flow and processing are bidirectional.
stream buffer. A C++ stream buffer is a buffer
between the ultimate consumer and the I/O Stream
Library functions that format data. It is implemented
in the I/O Stream Library by the streambuf class
and the classes derived from streambuf.
stream collection. A method of collecting auditing
data that writes audit records to a circular buffer
within the kernel. The data can be displayed, or
printed to provide a paper audit trail, or converted
into bin records.
stream editor. The sed command, which modifies
lines from a specified file, according to an edit
script, and writes them to a standard output.
stream end. The end of the stream furthest from
the user process. The stream end contains the
driver.
stream head. The end of the stream closest to the
user process. The stream head provides the
interface between the stream and the user
process. The principal functions of the stream head
are processing STREAMS–related system calls,
and bidirectional transfer of data and information
between a user process and messages in
STREAMS’ kernel space.
streaming tape device. See streaming tape drive.
streaming tape drive. A magnetic tape unit that
stores large amounts of data and is designed to
make a nonstop dump or restore of magnetic disks
without using interblock gaps.
STREAMS. A kernel mechanism that supports
development of network services and data
communication drivers. It defines interface
standards for character input and output within the
kernel, and between the kernel and user level. The
STREAMS mechanism comprises integral
functions, utility routines, kernel facilities, and a set
of structures.
strength reduction. An optimization that replaces
an arithmetic operation with a functionally
equivalent arithmetic optimization of lesser
strength. For example, 4*2 can be transformed into
4+4.
strict type checking. Checking data types for
compliance with the rules of C language more
strictly than the C compiler, such as with the lint
program.
stride. The relationship between the layout of an
array’s elements in memory and the order in which
those elements are accessed. A stride of 1 means
that memory–adjacent array elements are
accessed on successive iterations of an
array–processing loop. A stride of N means that for
each array element accessed, N–1
memory–adjacent elements are skipped over
before the next accessed element.
string. (1.) A linear sequence of entities such as
characters or physical elements. Examples of
strings are alphabetic string, binary element string,
bit string, character string, search string, and
symbol string. (2.) In Pascal, an object of the
predefined type STRING. (3.) The form of data
used in programming languages for storing and
manipulating text. In C language code, a string is
treated as a one–dimensional array of type char.
string constant. Characters enclosed in double
quotation marks.
string register. A register that holds a defined
string value to be called by a token. See also
token.
string value. Value of specified string. In
AIXwindows, the value of a string that identifies a
Text widget.
stroke text. Synonym for programmable character
set and geometric text.
structure. A variable that contains an ordered
group of data objects. Unlike an array, the data
objects within a structure can have varied data
types.
Structure Rule Table (SRT). A recurring attribute
of the directory schema with the description of the
permitted structures of distinguished names.
structure tag. The identifier that names a structure
data type.
structured field. A mechanism that permits
variable length data to be encoded for transmission
in the data stream. See also field.
structured file. (1.) A special type of INed file that
contains specialized data, such as information
about the structure of the data in the file, and
history information about changes that have been
made to the file. Structured files can contain
hierarchical data that is displayed and edited by
using forms. (2.) In Encina, a file with data
organized into a specific format that is usually
record–oriented.
structured file system. The collection of data
managed by a single structured file server (SFS).
All access to a structured file system is through a
single server, using a special type of file descriptor
(OFD) that identifies the file system and its
organization.
structured programming. A technique for
organizing computer programs in hierarchical
modules, making programs easier to debug,
modify, and replace. Typically, all modules have a
single entry point and a single exit point. Control is
passed downward through the structure without
unconditional branches to higher levels of the
structure.
structured type. Any of several data types that
define variables having multiple values; for
example, records and arrays. Each value is a
component of the structured type. Contrast with
scalar type.
stub. (1.) In NCS, a program module that transfers
remote procedure calls and responses between a
client and a server. Stubs perform marshalling,
unmarshalling, and data format conversion. Both
clients and servers have stubs. The compiler
generates client and server stub code from an
interface definition. See also marshal. (2.) Hooking
functions used as extensions to the protocol to
generate protocol requests for Enhanced
X-Windows. Synonym for hooking routines. (3.)
The RPC calls produced by the compiler when an
interface is defined. Two sets of stubs are
produced, client stubs and server stubs. The
application code calls the stub, and the RPC
mechanism translates this into a call to the
appropriate function on the remote machine.
stub procedures. Method procedures in the
implementation template generated by the SOM
Compiler. They are procedures whose bodies are
largely vacuous, to be filled in by the implementor.
Style Manager. In CDE, the software application
used to customize some of the visual elements and
system device behaviors of the workspace
environment, including colors and fonts, and
keyboard, mouse, window, and session start–up
behaviors.
stylus. A device used to select a particular location
on a tablet.
subaddress. In X.25 communications, the
unallocated digits at the end of the national
terminal number (NTN). If the network provider
allocates all digits to the NTN, there can be no
subaddress.
subarea node. In data communications, a node
that uses network addresses for routing, and
whose routing tables are affected by changes in
Glossary
1-147
the configuration of the network. Subarea nodes
can provide boundary function support for
peripheral nodes.
subchannel. A logical communications path
defined in S/370 architecture to perform transfers
to a given device.
subclass. (1.) A class of widgets that inherits
resources from a higher class. (2.) In SOM, a class
that inherits instance methods, attributes, and
instance variables directly from another class,
called the parent class, base class, superclass, or
indirectly from an ancestor class. A subclass may
also be called a child class or derived class.
subclassing. In SOM, the process whereby a new
class, as it is created (or derived), inherits instance
methods, attributes, and instance variables from
one or more previously defined ancestor classes.
The immediate parent class(es) of a new class
must be specified in the class’s interface
declaration. See also inheritance.
subcommand. A request for an operation that is
within the scope of work requested by a previously
issued command.
subcomponent. In Ada language, either a
component, or a component of another
subcomponent.
subdirectory. In the file system hierarchy, a
directory contained within another directory.
subfolder. In CDE, a folder contained within
another folder (sometimes called the parent folder).
When discussing command–line activities, this may
be called a subdirectory.
subheap. In Pascal, part of a heap delimited by a
call to MARK. Subheaps are treated in a stack–like
manner within a heap.
subhost. A communications system that controls
attached workstations in addition to communicating
with another (usually higher–level) system.
subject identifier (SID). A string that identifies a
user or set of users. Each SID consists of three
fields in the form person.group.organization. In an
account, each field must have a specific value; in a
ACL entry, one or more fields may be a wildcard.
submenu. A menu accessed from another menu
by a ––> symbol. A related menu that can only be
reached from a main menu. In AIXwindows, one
example of a submenu is an XmCascadeMenu
widget that appears from the side of an
XmPopupMenu widget when the mouse pointer is
dragged sideways across a main menu item.
subnet. One of a group of multiple logical network
divisions of a single network, such as can be
1-148
Glossary
created by the TCP/IP Interface Program.
Synonymous with subnetwork.
subnet address. The subdivided part of the local
host address, which has been reserved for
indicating the subnet. Subnet addressing allows an
autonomous system made up of multiple networks
to share the same Internet network address.
subnet address mask. A bit mask used by a local
system to determine whether a destination is on
the same network as the source or if the
destination can be reached directly through one of
the local interfaces.
subnetwork. Synonym for subnet.
subobject. An object that is in a subordinate
relationship to a given object.
subpanel. In CDE, an extension of the Front Panel
that slides up providing access to additional
elements. Subpanels usually contain groups of
related elements.
subpattern. A discrete element of a regular
expression.
subprocess. A process initiated by another
process. Control is transferred back to the main
process after the subprocess finishes running.
subprogram. (1.) A program called by another
program, such as a subshell. (2.) In FORTRAN, a
program unit that has a FUNCTION,
SUBROUTINE, or BLOCK DATA statement as its
first statement. Contrast with main program. (3.) In
Ada language, a subprogram is either a procedure
or a function. A procedure specifies a sequence of
actions and is invoked by a procedure call
statement. A function specifies a sequence of
actions and also returns a value called the result,
and so a function call is an expression. A
subprogram is written as a subprogram
declaration, which specifies its name, formal
parameters, and (for a function) its result; and a
subprogram body which specifies the sequence of
actions. The subprogram call specifies the actual
parameters that are to be associated with the
formal parameters. A subprogram is one of the
kinds of program unit. See also function and
procedure.
subrange scalar type. In Pascal, a type that
defines a variable whose value is restricted to
some subset of values of a base scalar type. See
also base scalar type.
subroutine. (1.) A sequenced set of statements or
coded instructions that can be used in one or more
computer programs and at one or more points in a
computer program. (2.) A routine that can be part
of another routine. See also routine. (3.) A request
by an active process for a service by the system
kernel. See also macro.
Subroutine ID. A unique identification number
associated with each subroutine included in an
application.
subroutine switch table. Contains the address for
the specific handler routine that handles the
subroutine.
subscribe. In X.25 communications, to a rent an
X.25 line, specifying the required facilities.
subwidget. In AIXwindows and Enhanced
X-Windows, a widget class directly beneath a
higher widget class in a widget–gadget hierarchy.
suffix. (1.) A character string attached to the end
of a file name that helps identify its file type. (2.) A
code dialed by a caller who is already engaged in a
call. (3.) A part of a file name, added at the end,
separated from other suffixes or the base file name
by some punctuation, such as a period (.).
subscript. (1.) An integer or variable whose value
selects a particular element in a table or an array.
(2.) Characters printed one–half line below the
normal printing line.
superblock. In a file system layout, refers to Block
1, which is used to keep track of the file system
and is the most critical part of the file system. It
contains information about every allocation or
deallocation of a block in the file system. See also
i–list.
subscript declarator. In an array definition or
declaration, the bracketed expressions following
the array name. Specifies the number of elements
in an array dimension.
superclass. In AIXwindows and Enhanced
X-Windows, a class of widgets that passes
inheritable resources down the hierarchy to a lower
subclass. See also widget record.
subscript quantity. In FORTRAN, a component of
a subscript. A subscript quantity is an integer or
real constant, variable, or expression.
superclient. A diskless client with read and write
permission and root access to the remote
resources used by other clients. A superclient
installs and maintains optional software of Version
3.2 of the operating system on a non–Version 3.2
diskless server.
subserver. A system resource or program that is
directly controlled by a server program running
under control of the System Program Controller.
subset. (1.) A set each element of which is an
element of a specified other set. (2.) A variant form
of a programming language with fewer features or
more restrictions than the original language. (3.) In
telecommunications, a subscriber set such as a
telephone.
subshell. An instance of the shell program started
from an existing shell program.
substring. A contiguous subportion of a string.
subsystem. (1.) A secondary or subordinate
system, usually capable of operating independently
or synchronously with a controlling system. (2.) The
part of communications that handles the
requirements of the remote system, isolating most
system–dependent considerations from the
application program.
subtree. A lower–level directory structure.
subtype. (1.) An IOCINFO ioctl variable that
identifies the kind of DLC being queried. (2.) In Ada
language, a subtype of a type characterizes a
subset of the values of the type. The subset is
determined by a constraint on the type. Each value
in the set of values of a subtype belongs to the
subtype and satisfies the constraint determining the
subtype.
subunit. For Ada programming, see body.
superobject. An object that is in a superior
relationship to a given object.
superscalar. The capability to execute multiple
instructions in a given clock cycle.
superuser. See root user.
superuser authority. See root user authority.
supervisor. The part of the operating system
control program that coordinates the use of
resources, and maintains the flow of processing
unit operations.
supervisor call (SVC). An instruction that
interrupts the program being run and passes
control to the supervisor so it can perform a
specific service indicated by the instruction.
supporters. In Ada language, all the compilation
units required by the language to allow a unit to be
compiled. This consists of the unit’s imports, their
imports, and so on.
surface characteristics. Characteristics of the
style of a written document: readability, sentence
length and structure, word length and usage, verb
type, and sentence openers.
suspended state. (1.) A state in which the
resource is temporarily not receiving a request. A
start action request returns the resource to the
Glossary
1-149
state it was in prior to being suspended. (2.) A
software state in which a task is not dispatched by
the system and is not contending for the processor.
SVC. See switched virtual circuit and Supervisor
call.
swap interval. In GL, the amount of elapsed time
between frame buffer swaps. The system waits at
least the amount of time specified by the swap
interval subroutine before honoring a request to
exchange the front and back buffers. The swap
interval is measured in units of vertical retraces,
which occur every 30th of a second on most
systems. The swap interval is useful in achieving
smooth–flowing animation.
sections of the template (which are correspondingly
labeled as ”classS” or by a user–defined name).
symbol table. See parse.
symbolic address. A unique line address, such as
. (period) or $ (dollar sign), used in place of a line
number address to identify location of data. See
also pattern address.
symbolic debugger (sdb). A tool that aids in the
debugging of programs written in certain high–level
languages.
symbolic link. Type of file that contains the path
name of and acts as a pointer to another file or
directory.
swapping. (1.) Temporarily removing an active job
from main storage, saving it on disk, and
processing another job in the area of main storage
formerly occupied by the first job. (2.) In a system
with virtual storage, a paging technique that writes
the active pages of a job to auxiliary storage and
reads pages of another job from auxiliary storage
into real storage.
symbolic name. A unique name used to represent
an entity such as a file or a data item. See also
name.
swidget. See shadow widget.
synchronization character (SYN). In binary
synchronous communications, the transmission
control character that provides a signal to the
receiving station for timing.
switch. A command–line option.
switch expression. (1.) The expression that is
located between the keyword switch and the body
of a switch statement. (2.) In C language, the
controlling expression of a switch statement.
switch table. The table used by the file system to
locate the entry points of a character device.
switched line. In data communications, a
connection between computers or devices
established by dialing. Contrast with nonswitched
line.
switched network backup (SNBU). In data
communications, a technique that provides a
switched line connection when a nonswitched line
fails.
switched virtual circuit (SVC). In X.25
communications, a virtual circuit that is requested
by a virtual call. It is released when the virtual call
is cleared. Contrast with permanent virtual circuit.
See also virtual circuit.
SWVPD. See Software Vital Product Data.
symbol. In the SOM Emitter Framework, any of a
(standard or user–defined) set of names (such as,
className) that are used as placeholders when
building a text template to pattern the desired
emitter output. When a template is emitted, the
symbols are replaced with their corresponding
values from the emitter’s symbol table. Other
symbols (such as, classSN) have values that are
used by section–emitting methods to identify major
1-150
Glossary
symmetrical multiprocessor (SMP) system. A
system containing multiple processors that are
essentially identical and perform identical functions.
SYN. See synchronization character.
synchronous. (1.) Two or more processes that
depend upon the occurrences of specific events
such as common timing signals. (2.) Occurring with
a regular or predictable time relationship or
sequence.
synchronous data link control (SDLC). (1.) A
form of communications line control using
commands to control the transfer of data over a
communications line. Contrast with binary
synchronous communication. (2.) A discipline
conforming to subsets of the advanced data
communications control procedures (ADCCP) of
the ANSI and the HDLC of the International
Organization for Standardization. It manages
synchronous, code–transparent, serial–by–bit
information transfer over a link connection.
Transmission exchanges can be duplex or
half–duplex over switched or nonswitched links.
The configuration of the link connection may be
point–to–point, multipoint, or loop.
synchronous transmission. (1.) In data
communications, a method of transmission in
which the sending and receiving of characters is
controlled by timing signals. Contrast with
asynchronous transmission. (2.) Data transmission
in which the time of occurrence of each signal
representing a bit is related to a fixed time base.
syntax. (1.) The grammatical rules for constructing
a command, statement, or program. (2.) In XOM:
(a.) An OM syntax is any of various categories into
which the object management specification
statically groups values on the basis of their form.
These categories are additional to the OM type of
the value. (b.) A category into which an attribute
value is placed on the basis of its form.
syntax diagram. A diagram for a command that
displays how to enter the command on the
command line.
syntax error. A compile–time error caused by
incorrect syntax. See also semantic error.
syntax template. A lexical construct containing an
asterisk from which several attribute syntaxes can
be derived by substituting text for the asterisk.
system. The computer and its associated devices
and programs.
System/370 Host Interface Adapter (HIA). An
adapter that allows the attachment of a
POWERstation or POWERserver to a 5088
Graphics Control Unit.
system address list. The address list, controlled
by the system manager, that all users on the
system can use with the xtalk command to make
outgoing X.25 calls. See also address list and user
address list.
System Application Architecture FORTRAN
(SAA FORTRAN). A superset of the ANSI X3.p –
1978 FORTRAN 77 standard.
system board. The main circuit board in the
system unit that supports a variety of basic system
devices, such as a keyboard, a mouse, and so
forth. The system board also supplies other basic
system functions.
system call. A call by a program to an operating
system subroutine.
system console. A console, usually equipped with
a keyboard and display screen, that is used by an
operator to control and communicate with a
system. Synonymous with console.
system customization. Specifying the devices,
programs, and users for a particular data
processing system. Contrast with configuration.
See also customization.
system date. The date assigned by the system
user during setup and maintained by the system.
See creation date and session date.
system dump. A copy from storage of selected
data areas. Synonymous with kernel dump.
system image. The representation of a program
(and its related data) as it exists at the time it
resides in system memory.
system management. The tasks involved in
maintaining the system in good working order and
modifying the system to meet changing
requirements.
System Management Interface Tool (SMIT). A
set of menu–driven services that facilitate the
performance of such system tasks as software
installation and configuration, device configuration
and management, problem determination, and
storage management. SMIT is provided in both a
character–based curses interface and an
AIXwindows–based graphical user interface.
system memory. Synonymous with main storage,
but used in hardware to refer to semiconductor
memory (modules).
system menu. In AIXwindows, the pulldown in the
top left–hand corner of a window that allows users
to restore, move, size, minimize, and maximize the
window. It also allows users to exit the application
or to close a window. Also causes the appearance
of a dialog box to contain a list of the active
applications. With the optional split window
technique, the user views many parts of the same
object at one time.
System Network Architecture (SNA). (1.) An
architecture for controlling the transfer of
information in a data communications network. (2.)
The description of the logical structure, formats,
protocols, and operating sequences for transmitting
information units through, and controlling the
configuration and operation of networks.
system node. In the hierarchy of device locations,
this is the highest node. Every hardware device will
lead back to the system node if you follow the
connection path. For example, an SCSI disk is
connected to an SCSI adapter that is connected to
a bus that is connected to the system node.
System Object Model (SOM). Object–oriented
programming technology for building, packaging,
and manipulating binary class libraries.
system parameters. Synonym for kernel
parameters.
System Performance Measurement Interface
(Spmi). In the Performance Toolbox, the Agent API
that allows an application program to register
custom performance statistics about its own
performance or that of some other system
component. Once registered, the custom statistics
become available to any consumer of statistics,
local or remote. Also permits applications to access
statistics on the local system without using the
network interface. Such applications are called
local data–consumer programs.
Glossary
1-151
system profile. A file containing the default values
used in system operations.
System Program Controller (SPC). A system
program that controls the operation of other
application programs that run in the background
(daemons).
system prompt. Synonym for command line. The
system prompt is the symbol that appears at the
command line of an operating system. The system
prompt indicates that the operating system is ready
for the user to enter a command.
System Resource Controller (SRC). A set of
commands and subroutines used to create and
control subsystems. The SRC controls subsystem
processes using a common command line and the
C interface. The SRC is useful when you need a
common method to start, stop, and collect status
information on processes.
system restart. Synonym for initial program load.
system ROS. The piece of system microcode that
is responsible for loading a boot image.
1-152
Glossary
system services control point (SSCP). In SNA,
the focal point within an SNA network for managing
the configuration, coordinating network operator
and problem determination requests, and providing
directory support and other the session services for
network end users. Multiple SSCPs, cooperating as
peers, can divide the network into domains of
control, with each SSCP having a hierarchical
control relationship to the physical units and logical
units within its domain.
system startup. Synonym for initial program load.
system time. The amount of time that the
operating system spends providing services to an
application. System time includes time spent by the
operating system allocating storage or devices to
your program, and time spent processing operating
system calls your program makes.
system unit. The part of the system that contains
the processing unit.
system user. A person, device, or system that
uses the facilities of a computer system.
T
tab. To move a cursor to a preset location on a
display screen.
tab group. In AIXwindows, a means of organizing
XmPrimitive widgets into groups for more efficient
traversal within and between groups.
table. An array of data in which each item can be
unambiguously located by means of one or more
values.
tablet. A special flat surface with a mechanism for
indicating positions on it. A tablet is normally used
as a locator.
tablet origin. A point on a tablet to which all other
locations on the tablet correspond. The origin is
either the lower–left corner or the center of the
tablet.
tabulating window. In Performance Toolbox, a
special form of window that tabulates the values of
an instrument as data is received and can also
calculate a line with a weighted average for each
value.
tag. (1.) In GL, a marker in the display list used as
a location for display list editing. (2.) In Interleaf,
the alphanumeric name of an autonumber
reference. This name can be assigned by Interleaf
or by the writer; but it must match the autonumber
of the component it is referencing.
tag field. In Pascal, the field of a record that
defines the structure of the variant part. See also
variant part.
tag–in. A control line bus that passes signals from
the control unit to the host on the System 360/370
Parallel Channel Interface.
tag–out. A control line bus that passes signals
from the host to the control unit on the System
360/370 Parallel Channel Interface.
Tagged Input Format File (TIFF). A graphics file
format using bitmaps.
target is a node running the license server
daemon. (3.) For NIM, the client you are installing.
target file. A file created by the make program that
contains a completed program.
target object. (Or receiver.) In SOM, the object
responding to a method call. The target object is
always the first formal parameter of a method
procedure. For SOM’s C–language bindings, the
target object is the first argument provided to the
method invocation macro, _methodName.
target program. Synonym for object program.
task. (1.) A basic unit of work to be performed.
Some examples include a user task, a server task,
and a processor task. (2.) A process and the
procedures that run the process. (3.) In a
multiprogramming or multiprocessing environment,
one or more sequences of instructions treated by a
control program as an element of work to be
accomplished by a computer. (4.) In Ada language,
a task operates in parallel with other parts of the
program. It is written as a task specification (which
specifies the name of the task and the names and
formal parameters of its entries), and a task body
which defines its execution. A task unit is one of
the kinds of program unit. A task type is a type that
permits the subsequent declaration of any number
of similar tasks of the type. A value of a task type is
said to designate a task. (5.) A C++ task is a
lightweight, nonpreemptive routine that you can
use to simulate the operation of programs. Tasks
are nonpreemptive because only a single task is
executing at any one time. Tasks are lightweight
because less time and space are required to create
a task than a true operating–system process.
task ID. In Ada language, analphabetic label or
identification for a task. This label is determined by
the debugger TASKS option. A task ID is assigned
to each task that has not terminated.
Task Library. A C++ class library that provides the
facilities to write programs that are made up of
tasks.
tasking. Synonym for multitasking.
tape drive. A mechanism for moving magnetic
tape and controlling its movement.
tbl. A preprocessor that formats tables for the nroff
and troff commands.
target. (1.) A system, a program within a system,
or a device that interprets, rejects, or satisfies, and
replies to requests received from a source.
Contrast with source. (2.) The node at which a
password is to be installed. If the password
specifies a single nodelocked license, the target is
the node licensed to run the product. If the
password specifies multiple nodelocked licenses
(that is, a compound password for nodelocked
licenses), or licenses of any other type, then the
TCB. See trusted computing base.
TCP. See Transmission Control Protocol.
TCP/IP. See Transmission Control Protocol/Internet
Protocol.
TCW. Translation control word.
TD. Transmit Data used with EIA–232 Protocol.
Glossary
1-153
telecommunication. The transmission of control
signals and information between computer systems
at two or more locations over telecommunication
lines, or between a computer system and remote
devices.
teleprocessing. Processing data that is received
from or transmitted to a remote location by way of
communication channels. Synonym for remote
access data processing.
Telnet. In TCP/IP, the protocol that opens the
connection to the system.
template. (1.) A representation of a keyboard that
includes functions not engraved on the keyboard.
(2.) Each command line stored in the buffer. (3.) In
enhanced edit mode, a special character buffer
associated with the terminal. (4.) In Mailer, an
ASCII file you can create for conveniently including
frequently typed information, such as your name
and electronic mail address, in your mail
messages. (5.) A family of C++ classes or functions
with variable types.
template class. A C++ class instance generated
by a class template.
template function. A C++ function generated by a
function template.
temporary error. An error that requires an
operation to be retried a number of times before it
is successfully completed.
temporary scalar. In a source–level optimization,
a scalar that is used to temporarily hold the
contents of an array element or the result of a
computation to eliminate logically redundant stores
and loads of that element or result.
term. An expression that is a subportion of another
expression, usually composed of other subportions
by means of addition or subtraction.
terminal. (1.) A device, usually equipped with a
keyboard and a display device, capable of sending
and receiving information over a communications
line. See also workstation. (2.) In a system or
communications network, a point at which data can
either enter or leave. (3.) In curses and extended
curses, a special screen that represents what the
workstation’s display screen currently looks like.
The terminal screen is identified by a window
named curscr, which the user does not access
directly. Instead, users make changes to the stdscr
window (or a user–defined screen) and then the
refresh (or wrefresh) window to update the
terminal.
Terminal. In CDE, in the Front Panel, an item in
the Personal Applications subpanel used to open a
terminal window.
1-154
Glossary
terminal application. An application running at a
workstation (terminal).
terminal descriptor. In ODM, a named variable of
type short, long, binary, char, or vchar used to
define the basic data types in an ODM object class
definition. See also short, long, binary, char,
descriptor, vchar, and object class.
terminal emulator. A program that allows a device
such as a microcomputer or personal computer to
enter and receive data from a computer system as
if it were a particular type of attached terminal.
terminal mapping. To translate between a
standard character set and a terminal–specific
character set.
terminal screen. Synonym for display screen.
terminator. The part of the program product that
performs the action necessary to end a job or
program.
test mode. Mode employed in testing a new user
interface, in which the compiled application is used
to drive the interface. Allows building, modifying,
testing, and refining operations without having to
compile, link, and debug.
text. (1.) A type of data consisting of a set of
linguistic characters (letters, numbers, and
symbols) and formatting controls. (2.) The portion
of a program that is able to be run. (3.) In kernel
mode, contains kernel program code that runs. It is
read only by a user process. (4.) In ASCII and data
communications, a sequence of characters treated
as an entity when preceded by one start–of–text
and ended by one end–of–text communication
control character. See also program text. (5.) In
word processing, information intended for human
viewing that is presented in a two–dimensional
form, such as data printed on paper or displayed
on a screen. (6.) The part of a message that is not
the header or control information.
text buffer. A text storage area.
text cursor. A cursor that indicates where to type a
character. The text cursor is controlled by the
keyboard.
Text Editor. In CDE, the software application used
to create and edit documents.
text field. In CDE, a rectangular area in a window
where information is typed. Text fields with
keyboard focus have a blinking text insertion
cursor.
text formatting program. A program that
determines the manner in which data will be placed
on a page.
text indicators. Symbols at the bottom of the INed
window to show directions the user can scroll to
view additional portions of the file.
text input mode. Mode in which typed characters
are interpreted by an editor as text entered into a
file. See also command mode and last line mode.
text lock. Allows the calling process to lock or
unlock its text segments into memory.
text string. A sequence of characters
(alphanumeric or special) defined by the user.
text widget. A text editor for customizing user
interfaces and programmatic interfaces.
text wrap. See word wrap.
textport. In GL, a region on the display screen
used to present textual output from graphical or
nongraphical programs.
texture. A pattern used to fill rectangles, convex
polygons, arcs, and circles.
tftp. See Trivial File Transfer Protocol.
thermal output. The heating load that a computer
system places on the cooling system of the
building, measured in British Thermal Units (BTU).
this. A C++ keyword that identifies a special type
of pointer that references the class object in a
member function.
thrashing. A condition, caused by a high level of
memory over–commitment, in which the system is
spending all of its time writing out virtual–memory
pages and reading them back in. The application
programs make no progress because their pages
don’t stay in memory long enough to be used.
Memory load control is intended to avoid or stop
thrashing.
thread. The dispatchable entity in AIX Version 4.
Each thread represents the current execution state
of a single instance of a program. Each user thread
runs in the environment provided by a specific
process, but multiple threads may share the
resources owned by that process.
thread–serial service. A reentrant system service
is thread–serial if it blocks the current thread and
all other threads that attempt to call the same
service or other related services until the first call
returns. See also reentrant service.
thread–synchronous service. A reentrant system
service is thread–synchronous if it blocks only the
current thread and allows other threads to execute
the same operation during the block. See also
reentrant service.
threaded application. An application that
performs its function by simultaneously using
multiple execution paths (threads of control) within
a single address space.
threshold. (1.) A logic operator with the property
that if P is a statement, Q is a statement, R is a
statement, and so on, then the threshold of P, Q, R,
and so on, is true if at least N statements are true,
and false if less than N statements are true. N is a
specified nonnegative integer called the threshold
condition. (2.) In computer graphics, a level above
which all gray–scale image data can be
represented as white and below which all
gray–scale image data can be represented as
black.
throughput. The number of workload operations
that can be accomplished per unit of time.
throughput–class negotiation. In X.25
communications, an optional facility that allows a
DTE to negotiate the speed at which its packets
travel through the packet switching network. See
also optional facilities.
throw expression. An argument to the exception
being thrown.
TIC. Transfer in channel.
ticket. An application–transparent mechanism that
transmits the identity of an initiating principal to its
target. A simple ticket contains the principal’s
identity, a session key, a timestamp, and other
information, sealed using the target’s secret key. A
privilege ticket contains the same information as a
simple ticket, and also includes a privilege attribute
certificate. A ticket–granting ticket is a ticket to the
ticket–granting service; a service ticket is a ticket
for a specified service other than the
ticket–granting service.
TIDL. Transactional Interface Definition Language.
tie–down resistor. A resistor used to hold the
input to a logic function or gate to the low level.
One end of the resistor is connected to ground or
the appropriate negative voltage.
tie–up resistor. A resistor used to hold the input to
a logic function or gate to the high level. One end
of the resistor is connected to the appropriate
positive voltage.
TIFF. See Tagged Input Format File.
tile. (1.) A pixmap. (2.) To fill a region with a
pixmap. (3.) To replicate a pixmap in two
dimensions.
time slice. The interval between scheduled checks
by the CPU scheduler to see if a different thread
should be dispatched. Unscheduled checks may
occur as a result of interrupts or system calls.
Glossary
1-155
time stamp. (1.) A time value expressed in
milliseconds, typically since the last server reset.
Time–stamp values wrap around usually after 49.7
days. The server, once given its current time, is
represented by timestamp T and always interprets
time stamps from clients by treating half of the
time–stamp space as being earlier in time than T,
and half the time–stamp space as being later in
time than T. One timestamp value, represented by
the constant CurrentTime, is never generated by
the server. This value is reserved for use in
requests to represent the current server time. (2.)
Information added to a record or other form of data
that shows the date and time at which a computer
processed that record or data. (3.) An integer that
describes the date and time at which a set of
licenses was created. (4.) Records the date and
time when an Ada–language compilation unit was
last modified.
TIMED. Timed Server Protocol. A protocol used to
synchronize a host’s time with the time of other
hosts.
timeslicing. A mechanism by which running
threads are preempted at fixed intervals. This
ensures that every thread is allowed time to
execute.
timing loop. A loop placed around code whose
performance is to be timed, such that the timing
loop increases the number of executions of the
code within it to a time that can provide a
meaningful performance measurement.
title bar. The bar that appears across the top of a
window and that contains a file name or title. It can
be used for moving or activating the window.
TLB. See translation lookaside buffer.
TLB miss. A memory delay that occurs when a
memory location is referenced and the page that
contains that memory location does not have an
entry in the appropriate transition lookaside buffer
(instruction or data).
TLI. Transport Layer Interface.
TOD. Time of day.
toggle. (1.) A switching device such as a toggle
key on a keyboard. (2.) Pertaining to any device
having two stable states. (3.) To switch between
two modes on a computer or network.
toggle button. In AIXwindows and Enhanced
X-Windows, a graphical object that simulates a
real–world toggle switch; it switches sequentially
from one optional state to another.
token. (1.) The smallest independent unit of
meaning of a program as defined by either the
parser or the lexical analyzer. A token can contain
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Glossary
data, a language keyword, an identifier, or other
parts of a language syntax. (2.) In the m4
command, any string of letters and digits that the
m4 command recognizes. (3.) A type of macro that
the typesetting preprocessor replaces with an
assigned string value. See also string register. (4.)
In a local area network, the symbol of authority
passed among data stations to indicate the station
temporarily in control of the transmission medium.
token numbers. Nonnegative integers that
represent the names of tokens.
token ring. A type of local area network that was
developed under the auspices of the IEEE 802.5
Subcommittee. A token access procedure used
with a sequential (ring) topology.
Toolkit. In AIXwindows and Enhanced X-Windows,
a collection of C language data structures and
subroutines that collectively expedite the
development of graphical user interfaces for
compatible applications written in C language.
top–down. An approach to problem solving that
starts at the highest level of abstraction and
proceeds toward the lowest level.
top–level. In AIXwindows and Enhanced
X-Windows, pertaining to the widget classes at the
top level of a widget–gadget hierarchy.
top–level transaction. A transaction that does not
execute within the scope of another transaction. In
other words, a top–level transaction is the root of a
transaction family, even if it is the only transaction
in the family tree.
top–level widget. In AIXwindows and Enhanced
X-Windows, widget classes that are at or near the
top level of the object class hierarchy, which is
known as the Core class.
top–level window. In AIXwindows and Enhanced
X-Windows, the main window that contains all
other windows associated with a client application.
top shadow. In AIXwindows, an arrow band of
lighter color across the top of a rectangular
graphical object (a widget or gadget) that creates a
three–dimensional appearance when the object is
manipulated.
topic tree. In CDE, in a general help dialog box, an
expandable and contractible list of topics that can
be selected to display help information.
topological sort. A sorting file that sorts an
unordered list of ordered pairs.
tower. A set of physical address and protocol
information for a particular server. CDS uses this
information to locate the system on which a server
resides and to determine which protocols are
available at the server. Tower values are contained
in the CDS_Towers attribute associated with the
object entry that represents the server in the cell
namespace.
result. Some examples are the entry of a
customer’s deposit and the updating of the
customer’s balance. (2.) In a batch or remote batch
entry, a job or job step.
TPN. See transaction program name.
transaction family. Nested transactions that have
a common ancestor belong to the same transaction
family. All members of a transaction family commit
together and drop their locks simultaneously.
trace. (1.) To record data that provides a history of
events occurring in the system. (2.) A record of the
running of a computer program. It exhibits the
sequences in which the instructions were run. (3.)
To monitor system performance or aid in
debugging programs.
trace daemon. Reads from the trace device driver
and writes to the trace log file.
trace entry. Data recorded from a trace event.
trace ID. A unique identifier for a traced event.
trace log. A file where trace events are recorded.
trace table. A storage area that contains a record
of the performance of computer program
instructions.
trace template. Used by the trace formatter to
determine how the data contained in trace entries
should be formatted.
traceback. For the Ada debugger, a listing of the
routines that are in the call chain above the code
you are debugging. For example, if you set a
breakpoint within an Ada procedure and request a
call traceback, you see a list of all the procedures
that called your Ada procedure, in the order in
which they called it. All the calling procedures in
the call chain are listed up to, but not including, the
operating system calling the original highest level
routine.
track. (1.) A circular path on the surface of a fixed
disk or diskette on which information is
magnetically recorded and from which recorded
information is read. (2.) The path on a data
medium associated with a single reading or writing
component as the data medium moves past the
component.
trailer. The portion of a message that contains
control information. Trailers are used by the VAX
Trailer Encapsulation Protocol. Trailer
encapsulation allows the receiving host to receive
data on a page–aligned boundary, which is a
requirement for utilizing a page–mapped virtual
memory environment.
trailer page. A trailer page that follows a printed
file or a print job.
TRAN. Distributed Transaction Service.
transaction. (1.) An exchange between a
workstation and a program, two workstations, or
two programs that accomplish a particular action or
transaction ID. See transaction identifier.
transaction identifier. A unique identifier assigned
to each transaction, used to identify all actions
associated with that transaction.
transaction program. A program that processes
transactions in an SNA network. The two kinds of
transaction programs are application transaction
programs and service transaction programs. See
also conversion, application transaction program,
and service transaction program.
transaction program name (TPN). The name of
an application program that uses data
communications to send or receive data to or from
another application program.
transactional RPC. transactional remote
procedure call.
transcript. In remote communications, a file that
contains the written record of commands you enter
on the remote system and the remote system’s
response to those commands.
transfer. To send data to one place and to receive
data at another place.
transformation. In GL, a four–by–four matrix that
helps determine the location where
three–dimensional drawing will occur, the position
of the viewpoint (the viewer’s ”eye”), and the
amount of the scene encompassed and visible.
Transformations occur at four points within the
graphics pipeline: (1.) Modeling transformation,
which maps modeling coordinates into world
coordinates. All drawing primitives specify positions
that are presumed to be positions in modeling
coordinates. Modeling transformation can be used
to move the thing being drawn. (2.) Viewing
transformation, which maps from world coordinates
to viewer coordinates. The origin of the viewer
coordinate system can be thought of as the
location of the viewer’s ”eye,” and viewing
transformations can be used to move the ”eye”
around in world coordinates. (3.) Projection
transformation, which defines the boundaries of the
clipping region. A projection transformation maps
viewer coordinates to normalized device
coordinates, and the clipping plane boundaries are
at x = +/–w,y = +/–w, z= +/–w. Projection
transformations can be used to define what region
Glossary
1-157
of the world is visible on the screen. (4.) Viewport,
or NDC to DC transformation. The viewport
transformation is not a full–fledged four–by–four
transformation matrix; only three of the diagonal
elements in the matrix can be changed. The
viewport determines the mapping from normalized
device coordinates to screen (device) coordinates.
By default viewports are the same size as the
window, although this can be adjusted. See also
normalized device coordinates, modeling
coordinates, rotation, eye coordinates, screen
coordinates, selecting region, viewing matrix, world
coordinates, clipping, and current transformation
matrix.
transient. A program or subroutine that does not
reside in main storage.
transit delay. In X.25 communications, the time it
takes a packet to travel from one DTE to the other.
translation. (1.) The movement of something by a
certain distance. (2.) In computer graphics, the
moving of a display image in a straight line from
one location to another. See also transformation.
translation lookaside buffer (TLB) . A table in the
CPU that contains cross–references between the
virtual and real addresses of recently referenced
pages of memory.
translation table. (1.) A table that specifies the
mapping of events or event sequences to
procedure names. (2.) A string containing a list
translating the events to procedure calls.
translation table list. See translation table.
translations. Action procedures that are called for
an event or sequence of events.
transmission control characters. Special
characters included in a message to control
communication over a data link. For example, the
sending station and the receiving station use
transmission control characters to exchange
information. The receiving station uses
transmission control characters to indicate errors in
data it receives.
Transmission Control Protocol (TCP). A
communications protocol used in ARPA Internet
and any network following the U.S. Department of
Defense standards for inter–network protocol.
Provides a reliable host–to–host protocol between
hosts in packet–switched communications
networks and in interconnected systems of such
networks. It assumes that the Internet Protocol is
the underlying protocol.
Transmission Control Protocol/Internet
Protocol (TCP/IP). An industry–standard,
nonproprietary communication protocol suite that
allows connectivity between equipment from
1-158
Glossary
different manufacturers. Its development was
funded by the Department of Defense Advanced
Research Projects Agency. A communications
subsystem that allows you to set up local area and
wide area networks.
transmission services (TS). In SNA, a
specification in a session activation request for
transmission control (TC) protocols to be supported
by a particular session (such as session–level
pacing the usage of session–level requests). Each
transmission services request defined is identified
by a number.
transmit burst. A group of transmit packets that
are sent without an intervening receive or time–out
operation.
transparent. (1.) In communications, pertaining to
transmissions that cannot interfere with data link
control, regardless of format or content.
Transparent transmissions are unrecognized by
data link controls. (2.) In data transmission,
pertaining to information that the receiving program
or device does not recognize as transmission
control characters. (3.) Pertaining to operations or
data that are of no significance to the user.
transparent binding. A form of binding that allows
the client application to bind to any available server
exporting the desired interface
transparent mode. A method of binary
synchronous text transmission in which only
transmission control characters preceded by the
data link escape(DLE) character are processed as
transmission control characters.
Transport Layer. A network service that provides
end–to–end communications between two parties,
while hiding the details of the communications
network. The TCP and ISO TP4 transport protocols
provide full–duplex virtual circuits on which delivery
is reliable, error free, sequenced, and duplicate
free. UDP provides no guarantees (the
connectionless RPC protocol provides some
guarantees on top of UDP).
transport protocol. A communications protocol
from the Transport Layer of the OSI network
architecture, such as the Transmission Control
Protocol (TCP) or the User Datagram Protocol
(UDP).
trap. An unprogrammed, hardware–initiated,
conditional jump to a specific address. It occurs as
a result of an error or certain other conditions. A
record is made of the location from which the jump
occurred.
trap handler. A user–defined trap routine used
when a trap occurs. See also exception.
Trash Can. In CDE, a container for deleted files or
folders.
traversal. See keyboard traversal.
tree delta. A SCCS file that has a trunk, with
changes identified by a release and level, and with
one or more branches with deltas identified by an
SID.
tree structure. A hierarchical calling sequence that
consists of both a root segment and one or more
levels of the segments called by way of the root
segment.
tree view. In CDE, a view of a folder or files that
includes all lower–level folders in the search path.
triangular array. A two–dimensional array in which
active elements are found only on one side of a
hypothetical axis delineated by the first and last
elements of the array.
trimming loops. In GL, a set of oriented closed
curves used to set the boundaries of a NURBS
surface. See also NURBS.
Trivial File Transfer Protocol. Transfers files
between hosts using minimal protocol.
troff. A phototypesetting utility originally designed
to support a Graphics Systems phototypesetting
machine, but now capable of supporting a variety
of phototypesetters.
true color. In Enhanced X-Windows, (1.) A
degenerate case of direct color in which the
subfields in the pixel value directly encode the
corresponding RGB values. That is, the color map
has predefined read–only RGB values. The values
are typically near–linear increasing ramps. (2.) Also
TrueColor, a value. (3.) Refers to the use of 24–bits
per pixel direct RGB, where there are 8 bits (256
levels) of red, 8 bits (256 levels) of green, and 8
bits (256 levels) of blue, for a total of 256*256*256
or 16,777,216 different combinations of red, green,
and blue intensities. The number of different
colored pixels that can then be simultaneously
displayed is only limited by the number of pixels
displayable from the frame buffer.
truncate. (1.) To end a computational process in
accordance with some rule; for example, to end the
evaluation of a power series at a specified term.
(2.) To remove the beginning or ending elements of
a string. (3.) To drop data that cannot be printed or
displayed in the line width specified or available.
Contrast with fold. (4.) To shorten a field or
statement to a specified length.
trust peer. A characterization of one cell with
respect to another with which the cell maintains a
mutual authentication surrogate.
trusted computing base (TCB). The part of the
system that contains all the elements that support
the security policy of the system. The trusted
computing base includes all hardware, microcode,
and software that protect information on the
system.
trusted device. An IPL device such as a fixed disk
or diskette drive, where the IPL ROM code can find
an IPL record and IPL code.
trusted environment. A clean environment in
which all untrusted processes have been killed
order to ensure security for communications
between the user and the operating system.
trusted path. See trusted environment.
trusted process. A process in which a particular
standard of security has been met.
try block. A C++ block in which a known exception
is passed to a handler.
TS. See transmission services.
TSO Time Sharing Option.
tty. In the operating system, any device that uses
the termio standard terminal device interface. tty
devices typically perform input and output on a
character–by–character basis.
tty device. See tty.
tuning. See hand tuning.
turnaround. Changing a communications line from
transmit mode to receive mode, or from receive
mode to transmit mode.
twist. A rotation around the line of sight.
two and one–half dimension. See 2–1/2
dimension.
two–way channel. In X.25 communications, a
logical channel that allows both incoming and
outgoing calls. Contrast with one–way channel.
twos complement. The radix complement in the
pure binary numeration system. The twos
complement is derived by taking the ones
complement and then adding one to the resulting
number. In a twos complement system, the twos
complement of a number n is –n. See also ones
complement.
type. (1.) In Enhanced X-Windows, an arbitrary
atom used to identify the data. A type is solely for
the benefit of clients and is not interpreted by the
server. Enhanced X-Windows predefines type
atoms for many frequently used types. Clients also
can define new types. (2.) In Pascal, see data type.
(3.) In NCS, a class of object. All objects of a
Glossary
1-159
specific type can be accessed though the same
interface or interfaces. (4.) In Ada language, a type
characterizes both a set of values, and a set of
operations applicable to those values. A type
definition is a language construct that defines a
type. A particular type is either an access type, an
array type, a private type, a record type, a scalar
type, or a task type. (5.) In XOM, a category into
which attribute values are placed on the basis of
their purpose.
type compatibility. See compatible types.
type conversion. A routine or set of routines that
enables an application to change a specified string
of data from one declared type to another. In
AIXwindows programming, type conversion is
performed on strings using conversion information
contained in the MRM database.
type declaration. The specification of the type
and, optionally, the length of a variable or function
in a specification statement.
type definition. A definition of a name for a data
type.
1-160
Glossary
type identifier. The name given to a declared type.
See also type specifier.
type regrouping. An optimization that involves
reodering mixed–type expressions so that all
variables of a given type are grouped together.
type specifier. A name of a data type. See also
type identifier.
type style. The form of characters of a given size,
style, and design within the set of the same font.
type UUID. (1.) A UUID that permanently identifies
a particular type. Both the RPC run time library and
the Location Broker use type UUIDs to specify
types. (2.) In DCE RPC, the UUID that identifies a
particular type of object and an associated
manager. See also object and Universal Unique
Identifier UUID.
typematic key. A key that, when held down,
repeats its function multiple times.
U
UA. See unnumbered acknowledge.
UART. See Universal Asynchronous
Receive/Transmit.
ublock. See user block.
UCT. See Universal Coordinated Time.
UDP. See User Datagram Protocol.
UDP/IP. User Datagram Protocol/Internet Protocol.
UFS. See UNIX File System.
UI. See unnumbered information frame.
UID. See user number and AIXwindows User
Interface Definition.
UIL. See AIXwindows User Interface Language.
ultimate consumer. The target of data in an input
and output operation. An ultimate consumer can be
a file, a device, or an array of bytes in memory.
ultimate producer. The source of data in an input
and output operation. An ultimate producer can be
a file, a device, or an array of bytes in memory.
umask. The file–mode creation mask. The default
permissions that are set automatically when a file is
created. These defaults can be changed by
including an appropriate umask command in the
system profile.
unary expression. An expression that contains
one operand.
unary operator. An operator that represents an
operation on one operand. Contrast with binary
operator.
unblocked. In an Enterprise Systems Connection
Director, the attribute that, when set, establishes
communications capability for a specific port.
Contrast with block.
unconditional branch. A branch that is taken
every time it is encountered.
(2.) To cause a command to no longer recognized
by the current computer system.
underlying editor. A large editor program, such as
vi, of which another editor program, such as vedit,
is a limited subset.
unescaped. In an expression, a character that is
not preceded by an escape sequence and is
therefore interpreted as a control character. See
also escape sequence.
unformatted file. A file displayed with data that is
not arranged with particular characters.
unidirectional printing. A printing method in
which the print head on the printer prints only while
it moves in one direction, instead of also printing
while it moves in the opposite direction. This
method of printing usually produces higher–quality
print output.
union. A variable that can hold any one of several
data types, but only one data type at a time.
union tag. The identifier that names a union data
type.
uniprocessor. A system containing a single
processor. As used in this book, the phrase
”comparable uniprocessor” means a system
designed to have only a single processor, with the
same CPU–clock speed and cache capacity as the
SMP system being discussed, running a
uniprocessor version of the operating system.
Contrast with single–processor SMP system.
unit. (1.) In FORTRAN, a means of referring to a
file to use input/output statements. A unit can be
connected or not connected to a file. If connected,
it refers to the file. The connection is symmetric;
that is, if a unit is connected to a file, the file is
connected to the unit. (2.) See also compilable unit.
(3.) For Ada programming, synonym for
compilation unit.
unit cube. In GL, a volume defined by the
following planes: x = –1, x = 1, y=–1, y = 1, z = –1,
z=1. See also normalized device coordinates.
unconfigure. (1.) Indicates that a user is taking a
device from the available (configured) state to the
defined state. This is accomplished by running the
unconfigure method for a device. The device status
field in the Customized Devices Object Class would
reflect this action. (2.) To take out of use by the
current computer system.
unit identifier. In FORTRAN, the number that
specifies an external unit or internal file. The
number can be one of the following: (1.) an integer
expression whose value must be zero or positive,
(2.) an * (asterisk) that corresponds to unit 5 for
input or unit 6 for output, or (3.) the name of a
character array, character array element, or
character substring for an internal file.
undefine. (1.) Indicates that a user is taking a
device instance out of the system. This is
accomplished by running the undefine method for
the device. All information for the device in the
Customized Database is purged by this operation.
Universal Asynchronous Receive/Transmit. A
circuit used in asynchronous data communication
applications to provide all the necessary logic to
recover data in a serial–in parallel–out fashion and
Glossary
1-161
to transmit data in a parallel–in serial–out fashion.
It is usually full–duplex, that is, it can transmit and
receive simultaneously with the option to handle
various data work length.
Universal Coordinated Time (UCT). The new
standard term for worldwide time–telling that has
the same meaning as Greenwich Mean Time.
Universal Unique Identifier (UUID). A 128–bit
value used for identification. NCS uses UUIDs to
identify cells, interfaces, objects, and types. The
UUID for a cell, generated by the uuid_gen tool, is
completely unique, having been created based on
the unique system ID of the workstation and a time
stamp. Once generated, the cell UUID is placed in
the glb_obj.txt file. See also object UUID and type
UUID.
UNIX File System (UFS). A section of the UNIX
file tree that is physically contained on a single
device or disk partition and that can be separately
mounted, dismounted, and administered.
UNIX–to–UNIX Copy Program (UUCP). (1.) A
group of commands, programs, and files, present
on most UNIX systems, that allows the user to
communicate with another UNIX system over a
dedicated line or a telephone line. See also Basic
Networking Utilities. (2.) The command (uucp) that
starts file copying from one or more sources to a
single destination.
unmanaged widget. A widget whose size cannot
be changed.
unmapped window. A window that is not visible
on the screen.
unmarshal. In NCS, to copy data from a Remote
Procedure Call packet. Stubs perform
unmarshalling. Contrast with marshal.
unnumbered acknowledge (UA). A link control
frame.
unnumbered information (UI) frame. A frame in
unnumbered format, used to transfer unnumbered
control functions.
unpredictable. A violation of an architecture rule
that an implementation is not required to report.
Results can include an error report from a threads
call, the operating system, or the hardware; a hang
or deadlock of the program; or an incorrect
operation of the program without indication of error.
See also illegal.
unprivileged state. A hardware protection state in
which the processor can only run unprivileged
instructions. The processor’s unprivileged state
supports the virtual machine’s operating system
state and problem state. Contrast with privileged
state.
1-162
Glossary
unreachable code. Code that cannot be reached
during program execution. Unreachable code is
detected and removed as part of optimization.
unused subprograms. In Ada language,
subprograms unused only within the context of a
specific program or set of units. For example, a
program might call only a small subset of
subprograms in a utility package. The remaining
uncalled (unreachable) subprograms constitute
unreachable code in the context of that program.
unviewable. Pertaining to a mapped window with
an unmapped ancestor.
update. (1.) The procedure of modifying a program
or program option that exists on the mass storage
medium of a computer, making the program
executable, and ensuring that the modified
program interacts properly with all other affected
programs in the system. (2.) An improvement for
some part of the system. (3.) To add, change, or
delete items. (4.) To modify a master file with
current information according to a specified
procedure.
update propagation. An immediate attempt to
apply a change to all replicas of the CDS directory
in which the change was just made. An update
propagation delivers changes in a more efficient
and timely way than a skulk, which is the periodic
distribution of a whole collection of changes.
update script. A shell script or executable file
created by the developer of an application program
to update the program. The script file must follow
specific guidelines to be compatible with the
program update tools that are provided in the
operating system.
Update Timestamp (UTS). An attribute that
identifies the time at which the most recent change
was made to any attribute of a particular CDS
name. For directories, the UTS reflects changes
made only to attributes that apply to the directory
as a whole (not one of its replicas).
upgrade. Software that fixes a defect in a
previously released software product.
upgrade locks. Locks used instead of read locks
that announce the potential need to also modify the
protected data. If an application obtains a read lock
and possibly a write lock to the same data, an
upgrade lock is less likely to deadlock.
upload. To transfer data from one computer to
another. Typically, users upload from a small
computer to a larger one.
upstream. The direction from driver to stream
head.
usage bindings. The language–specific binding
files for a class that are generated by the SOM
Compiler for inclusion in client programs using the
class.
use clause. In Ada language, a clause that
achieves direct visibility of declarations that appear
in the visible parts of named packages.
use–once license. In License Use Management, a
type of license administrated by the license server
that can be used for a single instance of invoking a
product or of using a service. The license server
decrements the number of use–once licenses each
time the product is used.
user. (1.) The name associated with an account.
(2.) Anyone requiring the services of a computing
system.
user account. See account.
user address list. The address list that an
individual can use with the xtalk command to make
outgoing X.25 calls. See also address list and
system address list.
user area. The parts of main storage and disk
available to the user.
user block. A data structure maintained by the
kernel that contains system information about a
user process, such as its real and effective user
IDs, the list of open file descriptors, and
signal–handling settings. The user structure
(defined in the /usr/include/sys/user.h header file)
specifies the exact information that is kept in the
user block. See also per–process data area.
User Datagram Protocol (UDP). A packet–level
protocol built directly on the Internet Protocol layer.
UPD uses application–to–application programs
between host systems.
user data segment. In kernel mode, the virtual
memory segment that contains user data, which
consists of initialized data variables.
user–defined variable. A shell variable to which
the user assigns a character string as a value.
user file. A text file that specifies the users who
may (or may not) use licensed software products.
user ID. See user identification.
user identification (user ID). (1.) One to eight
alphanumeric characters, beginning with an
alphabetic, #, $, or > character, that identifies a
user. This string of characters limits the functions
and information the operator can use. Often, the
user ID can be substituted in commands that take a
user’s login name as a value. See also user
number. (2.) A parameter that specifies the user ID
under which the application or transaction program
runs. Contrast with user name.
user interface. The hardware, software, or both by
which a user communicates with a system,
program, or device. Examples are a keyboard,
mouse, command language, or windowing
subsystem.
user mode. A mode in which a process is carried
out in the user’s program rather than in the kernel.
Contrast with kernel mode.
user name. A string of characters that uniquely
identifies a user to the system. Contrast with user
identification.
user number (UID). A number that uniquely
identifies a user to the system. It is the internal
number associated with a user ID. See also user
identification (user ID).
user profile. A file in the user’s home directory
named .profile that contains shell commands that
set initial user–defined characteristics and defaults
for the login session.
user space. The address space seen by a process
in user mode. See also user structure.
user structure. In kernel mode, the data area that
contains information that must be accessible while
a process runs. One user structure is allocated for
each active process. See also per–process data
area and user block.
user time. The amount of time a program is
running in the CPU. Does not include time
associated with operating system services provided
to the program, the program’s I/O time, or time in
which other processes preempt the program’s use
of the CPU.
USOC–RJ11. A miniature telephone jack.
UTC. See Universal Coordinated Time.
utility. (1.) A service. In programming, a program
that performs a common service function. (2.) The
capability of a system, program, or device to
perform the functions for which it is designed.
UTS. See Update Timestamp.
UUCP. See UNIX–to–UNIX Copy Program.
UUCP login ID. A login name, provided with the
Basic Networking Utilities (BNU), that has complete
access to all BNU files and directories. See also
Basic Networking Utilities.
UUID. See Universal Unique Identifier.
Glossary
1-163
quantity that can assume any of a given set of
values. (4.) For Ada programming, see object.
V
V. Volt.
V.24. The 24th CCITT recommendation in the V
series, listing the definitions for interchange circuits
between a DTE and a DCE.
V.35. The 35th CCITT recommendation in the V
series, defining data transmission at 48 kilobits per
second using 60–180 kHz group band circuits.
v–node. Virtual i–node. An object in a file system
that represents a file. Unlike an i–node, there is no
one–to–one correspondence between a v–node
and the file system; multiple v–nodes can refer to a
single file (a single i–node). V–nodes are used to
communicate between the upper half of the file
system (the logical file system) and the file system
implementations (such as the journaled file system,
the network file system, and the CD–ROM file
system).
valid. (1.) Allowed. (2.) True, or conforming to an
appropriate standard or authority.
validation. In X.25 communications, the process
by which the receiving DTE accepts the packet
size, packet window size, and throughput class
sent by the sending DTE, on the conditions that
they are valid. Contrast with negotiation.
valuator. (1.) An input device that provides a scale
value; for example, a thumb wheel or a
potentiometer. (2.) In GL, an input/output device
that returns a value in a range. For example, a
mouse is logically two valuators: the x position and
the y position. See also dial.
value. (1.) A set of characters or a quantity
associated with a parameter or name. (2.) In
programming, the contents of a variable or a
storage location. (3.) A specific occurrence of an
attribute, such as blue for the attribute color. (4.) A
quantity assigned to a constant, variable,
parameter, or symbol. (5.) In XOM, an arbitrarily
complex information item that can be viewed as a
characteristic or property of an object. See also
attribute value.
value logging. In the SOM Replication
Framework, a technique for maintaining
consistency among replicas of a replicated object,
whereby the new value of the object is distributed
after the execution of a method that updates the
object.
variable. (1.) A name used to represent a data
item whose value can change while the program is
running. Contrast with constant. (2.) In
programming languages, a language object that
can take different values at different times. (3.) A
1-164
Glossary
variable length field. A field of varying length that
contains data prefaced by an internal, opaque field
providing the length of the field.
variable substitution. The ability to change and
display the values of variables in a string, replacing
a name of a variable with the value it represents.
variant part. In Pascal, the part of a record that
can vary from one instance of the record to
another. The variant part consists of alternate
sequences of fields that share the same physical
storage. In Ada language, a variant part of a record
specifies alternative record components,
depending on a discriminant of the record. Each
value of the discriminant establishes a particular
alternative of the variant part. See also tag field.
VC. See virtual circuit.
vchar. In ODM, a terminal descriptor type used to
define a variable as a variable–length,
null–terminated string. See also terminal descriptor.
VCI. Virtual channel identifier in an ATM network.
VDD. See virtual device driver.
vector. (1.) An array of one dimension. (2.) A
quantity usually characterized by an ordered set of
numbers. (3.) In computer graphics, a directed line
segment.
vector graphics. (1.) Graphics for which the
display images are generated from coordinates, as
opposed to an array of pixels. (2.) The most
common class of graphics, where all vector output
consists of lines and curves drawn point–to–point
by the output unit as ordered by the computer.
vector product. Another term for the vector cross
product. If a = (a1, a2, a3) and b = (b1, b2, b3) are
two three–dimensional vectors, the vector product
a times b = (a2b3–b2a3, a3b1–b3a1, a1b2–b1a2).
vendor ID. In License Use Management, the
identifier of a vendor of licensed products. By
means of vendor IDs, license servers can
distinguish among any number of vendors
established in a network. Vendor IDs are an
License Use Management–specific usage of
Network Computing System Universal Unique
Identifiers (UUIDs).
vendor password. In License Use Management, a
string encoded with information about a vendor
that, together with a vendor ID, establishes the
vendor of a licensed product in a license database.
verify. (1.) To confirm the correctness. (2.) To
determine whether a transcription of data or other
operation has been accomplished accurately. (3.)
In software installation, the verify procedure
instructs the system to verify the software you are
installing. The system confirms that your software
files are the correct length and contain the correct
number of digits and characters. If any errors are
reported, it might be necessary to install the
software product again. The verification process
can add a significant amount of time to the
installation process.
Versatile Message Transfer Protocol (VMTP). A
protocol that provides datagram communication
service at the user level. Unlike most programs that
use UDP/IP, programs using VMTP do not have to
implement time out, retransmission, or estimation
of network delays because the VMTP protocol
provides end–to–end datagram delivery.
version. A particular instance of an application
program or licensed program. The version, release,
modification, and fix levels of a program. The
version, release, modification, and fix levels
together comprise the program level or version of a
program. A new version of a program usually has
significant new code or functions compared to the
previous version. See also fix number, program
level, modification number, release number, and
version number.
version control. The process by which the
contents of each revision of software, hardware, or
documentation are accounted for.
version identifier. In License Use Management, a
string that identifies a version of a product; by
means of version identifiers, the license server
distinguishes among different versions of a
product.
version number. The version level of a program,
which is an indicator of the hardware and basic
operating system upon which the program
operates. The version, release, modification, and
fix levels together comprise the program level or
version of a program. See also fix number,
modification number, release number, version and
program level.
vertical retrace. (1.) The rate at which the monitor
is refreshed. A 60 Hz monitor is redrawn 60 times
per second. Synonymous with refresh rate. (2.)
The action of moving the electron beam from the
bottom to the top of the screen.
vertical retrace period. The amount of elapsed
time between retraces of the screen. All video
monitors use an electron beam to sweep the
phosphors at the face of the monitor. Because the
phosphors glow for only a brief period of time, the
entire screen must be reswept periodically by the
electron beam. On most monitors, this is done 30
times per second (30 Hz). Thus, the vertical retrace
period is 1/30 second.
vhandle. An identifier for each object in VEOS.
vhandles are used in graphics programming to
identify software objects specified in VEOS. The
vhandle can exist longer than the object that it
identifies. After a software object such as a swidget
is destroyed, the vhandle for that object remains
defined.
video lookup table (VLT). A colormap
implemented in hardware.
view–data paradigm. A SOM Replication
Framework construct similar to the
Model–View–Controller paradigm in SmallTalk. The
”view” object contains only presentation–specific
information, while the ”data” object contains the
state of the application. The ”view” and ”data” are
connected by means of an ”observation” protocol
that lets the ”view” be notified whenever the ”data”
changes.
viewable. Pertaining to a mapped window whose
ancestors are all mapped; not necessarily visible.
Graphics requests can be performed on a window
when it is not viewable, but output will not be
retained unless the server is maintaining backing
store.
viewer coordinates. Synonym for eye
coordinates.
viewing coordinates. Synonym for eye
coordinates.
viewing matrix. In GL, a matrix used to describe
the location of the viewer (the virtual eye looking
upon a scene) in relation to the world. See also
field of view, transformation, and world coordinates.
viewport. In GL, the mapping from normalized
device coordinates to device coordinates. The
viewport maps the unit cube x/w = +/–1, y/w = +/–1,
z/w = +/–1 to the screen space, as measured in
pixels. The viewport is the last transformation in the
graphics pipeline. The viewport can be smaller or
larger than the window and smaller or larger than
the screenmask, although in most applications, it is
the same size.
virtual address. The address of a location in
virtual storage. A virtual address must be translated
into a real address for the data or instruction it
addresses to be accessible to the CPU.
virtual call facility . In data communications, a
user facility in which a call–setup procedure and a
call–clearing procedure determine a period of
communication between two data terminal
equipment (DTEs) in which user data is transferred
Glossary
1-165
in the network in the packet mode of operation. All
user data is delivered from the network in the order
it is received by the network. It is the packet
network equivalent of a dialed line.
virtual circuit (VC). In X.25 communications,
those facilities provided by a network that give the
appearance to the user of an actual connection.
See also switched virtual circuit and permanent
virtual circuit.
virtual device. A device that appears to the user
as a separate entity, but is actually a shared portion
of a real device.
virtual device driver (VDD). Synonym for device
handler.
virtual file system (VFS). A remote file system
that has been mounted so that it is accessible to
the local user.
virtual function. A C++ member function that is
declared with the keyword virtual. The
implementation that is executed when you make a
call to a virtual function depends on the type of the
object for which it is called. This is determined at
run time.
virtual key binding. In AIXwindows, the
user–designed key definitions.
virtual memory. Addressable space that appears
to be real storage. From virtual storage,
instructions and data are mapped into real storage
locations. The size of virtual storage is limited by
the addressing scheme of the computer system
and by the amount of auxiliary storage available,
not by the actual number of system memory
locations. Contrast with real memory. Synonymous
with virtual storage.
virtual mount point. The directory or file in the file
tree where another file system is mounted. For
example, if /dev/hd9 is mounted on /fred , then
/fred is the virtual mount point.
virtual printer. A view of a printer that refers only
to the high–level data stream (such as ASCII or
PostScript) that the printer understands. It does not
include any information about how the printer
hardware is attached to the host computer or the
protocol used for transferring bytes of data to and
from the printer.
virtual printer definition. A set of attributes values
that describe a particular data stream for a
particular printer.
virtual storage. Synonym for virtual memory.
Virtual Storage Extended (VSE). An operating
system that is an extension of DOS. A VSE system
consists of licensed VSE/Advanced Functions
1-166
Glossary
support plus all programs required to meet the data
processing needs of the user. Together with the
hardware it controls, VSE forms a complete data
processing system. Its current version is called
VSE/ESA.
Virtual Storage Extended/Enterprise Systems
Architecture(VSE/ESA). The VSE operating
system operating in an ESA environment. ESA is
an extension to the System/370 architecture and
includes an advanced addressability feature that
provides access registers.
Virtual Storage Extended/System Product
(VSE/SP). A licensed program providing VSE
operating system support.
Virtual Telecommunication Access Method
(VTAM). A licensed program that controls
communication and data flow in an SNA network. It
provides single–domain, multiple–domain, and
interconnected network capability, and also
supports application programs and subsystems.
visibility. In Ada language, at a given point in a
program text, the declaration of an entity with a
certain identifier is said to be visible if the entity is
an acceptable meaning for an occurrence at that
point of the identifier. The declaration is visible by
selection at the place of the selector in a selected
component or at the place of the name in a named
association. Otherwise, the declaration is directly
visible, that is, if the identifier alone has that
meaning.
visible. (1.) A region of a window that is mapped
and not occluded on the screen by another window.
(2.) Visibility of C++ identifiers is based on scoping
rules and is independent of access.
visible part. For Ada programming, see package.
VLSI. Very large scale integration.
VLSI circuit. Very large scale integrated circuit.
VLT. See video lookup table.
VM. Virtual machine.
VM/CMS. A type of operating system used on a
System/370 computer.
VMTP. See Versatile Message Transaction
Protocol.
VOL. See Volume Service.
Vol ID. See Volume ID.
volatile attribute. The keyword volatile located in
a definition, declaration, or cast. It causes the C
language compiler to place the value of the data
object in storage and to reload this value at each
reference to the data object.
volatile register. In a C language program, a
register whose value on entry need not be
preserved when the called routine returns.
volume. (1.) A certain portion of data, together with
its data carrier, that can be handled conveniently as
a unit. (2.) The level of sound of the system. (3.)
The physical storage location of a file system. See
also log volume.
volume group (VG). A set of one or more physical
volumes from which space can be allocated to one
or more logical volumes. A collection of 1 to 32
physical volumes (read–write fixed–disk drives) of
varying size and type. See also logical volume.
Volume ID (Vol ID). A series of characters,
recorded on the diskette, used to identify the
diskette to the user and to the system.
Volume Service (VOL). The component of Encina
Base that addresses storage.
VPD. See Software Vital Product Data (SWVPD).
VPI. Virtual path identifier in an ATM network.
VRAM. Video random–access memory.
VSE. See Virtual Storage Extended.
VSE/ESA. See Virtual Storage
Extended/Enterprise Systems Architecture.
VSE/SP. See Virtual Storage Extended/System
Product.
VTAM. See Virtual Telecommunication Access
Method.
VTL. Vendor Technology Logic.
volume label. An area on tape or disk that is used
to identify the tape volume and its owner.
Glossary
1-167
therefore, it is capable of transmitting data at high
speeds. Synonym for broadband channel.
W
WAN. See wide area network.
WAN links. Communications connections between
groups of computers that are spread across a large
geographical distance. Modem connections, T1
lines, and satellite hookups are some common
examples. See also wide area network.
water mark. A limit value used in flow control.
Each queue has a high–water mark and a
low–water mark. The high–water mark value
indicates the upper limit related to the number of
bytes contained on the queue. When the
characters in a queue reach the high–water mark,
STREAMS causes another queue that attempts to
send a message to this queue to become blocked.
When the characters in this queue are reduced to
the low–water mark value, the other queue is
unblocked by STREAMS.
Web–based System Manager. A graphical user
interface (GUI) tool for managing AIX systems.
Based on the OO (Object Oriented) model,
Web–based System Manager enables users to
perform administration tasks by manipulating icons
representing objects in the system, as an
alternative to learning and remembering complex
AIX commands.
widening. An expansion of the size of a value (for
example, short to int) by padding bits located to
the left of the value with a copy of the sign bit.
widget. (1.) The fundamental data type of the
Enhanced X-Windows Toolkit. (2.) An object
providing a user–interface abstraction; for example,
Scrollbar widget. It is the combination of an
Enhanced X-Windows (or subwindow) and its
associated semantics. Logically, it is a rectangle
with associated input and output semantics,
although some can be input–only or output–only.
Each widget belongs to one widget class. A widget
implements procedures through its widget class
structure. See also composite widget, core widget,
primitive widget, and shell widget. (3.) A widget is a
graphic device capable of receiving input from the
keyboard and the mouse and communicating with
an application or another widget by means of a
callback. Every widget is a member of only one
class and always has a window associated with it.
widget class. The general group that a specific
widget belongs to, otherwise known as the widget
type. Physically, it is a pointer to a structure.
Synonymous with widget type. See also class.
widget gravity. Synonym for window gravity.
widget hierarchy. Synonymous with widget tree.
well–known host name. A conventional name
associated with an Internet Protocol address on a
particular network (for example, the nameserver
and timeserver servers).
well–known port. A conventional port assignment
used by hosts that support the same protocols,
whether or not the hosts are on the same network.
Synonymous with contact port.
widget ID. A unique identification number
associated with each widget instantiated in an
interface.
widget instance. A specific widget object as
opposed to a general widget class. It is composed
of a data structure containing instance–specific
values and another data structure containing
information applicable to all widgets of that class.
See also instance.
while statement. A C language looping statement
that contains the keyword while followed by an
expression in parentheses (the condition) and a
statement (the action).
widget menu. A menu that allows the user to
perform any number of actions, such as cutting,
copying, and pasting, to selected widgets.
white space. Space characters, tab characters,
and new–line characters.
widget programmer. A programmer who adds
new widgets to the Enhanced X-Windows (or other)
Toolkit.
wide area network (WAN). A network that
provides data communication capability in
geographic areas larger than those serviced by
local area networks. A network that includes
computers spread across a large geographical
distance, usually involving several cities, states, or
countries.
wide band channel. A communications channel
that has a greater bandwidth than a voice channel;
1-168
Glossary
widget record. A collection of related data objects,
such as variables and parameters, associated with
any given widget. See also instance record, record,
class record, and superclass.
widget tree. (1.) The symbolic structure for
Enhanced X-Windows Toolkit code. The basic
element is a widget class. See also leaves,
intermediate nodes, and root. (2.) A widget tree is a
hierarchy of widgets within a specific client
application. The Shell widget is the root of the
widget tree. Widgets with no children of any kind
are leaves of the tree. Synonymous with widget
hierarchy.
widget type. Synonym for widget class.
widget visibility. Contrast with obscure and
occlude.
wildcard. Special characters such as * (asterisk) or
? (question mark) that can be used to match one or
more characters. Synonymous with
pattern–matching character.
window. (1.) In AIXwindows, rectangular area of
the screen that can be moved about, placed on top
of or pulled under other windows, or iconized by
the user. (2.) In GL, all drawing inside the window
is done by the GL process that created that
window, and is totally under the control of that
process. However, the drawing of the window
borders together with the window
placement/iconization, is under the control of the
window manager; for example, the AIXwindows
Window Manager. For most simple GL programs,
the viewport and screenmask are set to the same
size as the window. Do not confuse an AIXwindows
subroutine with the GL window subroutine, which
defines a frustum in world space. See also clipping
and current window. (3.) In curses and extended
curses, the internal representation of what a
portion of the display may look like at some point in
time. Windows can be any size, from the entire
display screen to a single character. (4.) In data
communications, the number of data packets a
DTE or DCE can send across a logical channel
before waiting for authorization to send another
data packet. The window is the main mechanism of
pacing, or flow control, of packets. See also frame
window and packet window. (5.) In the INed editor,
an area within the display screen that can be
subdivided into a collection of contiguous panes
used to present data to the user.
window gravity. The attraction of a subwindow to
some part of its parent. Window gravity causes
subwindows to be automatically repositioned,
relative to an edge, corner, or center of a window
when resized. Synonymous with widget gravity.
See also gravity.
window icon. In CDE, a minimized window.
window ID. A unique identification number
associated with each newly opened window in an
AIXwindows or Enhanced X-Windows environment.
window manager. In CDE Desktop, the program
that displays and controls windows on your screen.
Software that manages the multiple windows
associated with AIXwindows and Enhanced
X-Windows. In a graphics environment, the client
that manipulates windows on a screen and
provides much of the user interface. See also
mwm.
Window Manager. In CDE, the software
application that provides users with the capability to
manipulate windows on the workspace; for
example, opening, resizing, moving, and closing
windows.
Window menu. In CDE, the menu displayed by
choosing the Window menu button. The menu
provides choices that manipulate the location or
size of the window, such as Move, Size, Minimize,
and Maximize.
Window menu button. In CDE, the control at the
upper left corner of a window, next to the title bar.
Choosing it displays the Window menu.
wire frame. A graphics surface–drawing technique
in which the edges and contours of a primitive are
represented by simple lines.
with clause. For Ada programming, see
compilation unit.
word. (1.) A contiguous series of 32 bits (four
bytes) in storage, addressable as a unit. The
address of the first byte of a word is evenly divisible
by four. Synonymous with fullword, machine word,
and computer word. Contrast with halfword. (2.) A
character string considered as a unit for a given
purpose.
word wrap. In word processing, a feature that
automatically moves text to the next line if the text
does not fit within the margins.
work area. In CDE, the part of a window where
controls and text appear.
work file. A file used for temporary storage of data
being processed.
working directory. Synonym for current directory.
working segment. A segment whose pages are
backed by slots in the disk paging space rather
than by a permanent location on disk.
working set. The parts of a program’s executable
code, data areas, or both that are being used
intensively and are therefore important to keep in
the fastest possible type of storage. Thus a
program’s instruction cache working set is the set
of program cache lines that need to be kept in the
instruction cache if the program is to run at
maximum speed.
workload. A sequence of requests, such as
commands, I/O operations, and subroutine–library
calls, that constitute the work being done by a
system. The term normally refers to a workload
Glossary
1-169
that has been captured in such a way as to be
repeatable (via shell scripts, remote terminal
emulators), so that it can be used to measure the
performance effect of changes to the system.
space to screen space. Synonymous with world
space. See also modeling coordinates, eye
coordinates, primitive coordinates, screen
coordinates, viewing matrxi, and transformation.
workload concurrency. The degree to which the
system approaches the ideal of always having as
many dispatchable threads as there are
processors.
world space. Synonym for world coordinates.
workspace. (1.) In XDS/XOM, a space in which
OM objects of certain OM classes can be created,
together with an implementation of the object
management functions that supports those OM
classes. (2.) In CDE, the current screen display, the
icons and windows it contains, and the unoccupied
screen area where icons can be placed.
workspace background. In CDE, the portion of
the display not covered by windows or icons.
workspace icon. In CDE, an icon that has been
copied from File Manager to the workspace.
workspace interface. The interface as realized,
for the dispatcher’s benefit, by each workspace
individually.
Workspace Manager. In CDE, the software
application that controls the size, placement, and
operation of windows within multiple workspaces.
Workspace menu. In CDE, the menu displayed by
pointing at an unoccupied area of the workspace
and clicking button 3 on the mouse.
workspace object. In CDE, an object that resides
in a workspace, rather than inside a viewer in a
window. Workspace objects include windows, icons
(minimized windows), and objects that have been
dragged from File Manager and Application
Manager and dropped on a workspace.
workspace switch. In CDE, a control that enables
you to select one workspace from among several
workspaces.
workspace switch area. In CDE, the rectangular
area in the center of the Front Panel that contains
the workspace switches, the Lock control, the Exit
button, and the busy light.
workstation. (1.) A configuration of input/output
equipment at which an operator works. (2.) A
terminal or microcomputer, usually one that is
connected to a mainframe or to a network, at which
a user can perform applications. See also terminal.
world coordinates. In GL, the user–defined
coordinate system in which an image is described.
Modeling commands are used to position primitives
in world space. Viewing and projection
transformations define the mapping of the world
1-170
Glossary
wrap around. (1.) The movement of the point of
reference in a file from the end of one line to the
beginning of the next, or from one end of a file to
the other. (2.) In display–based word processing
equipment, the automatic disposition of a printable
line of text onto two or more display lines,
necessitated by the horizontal limits of the display.
(3.) The continuation of an operation from the
maximum addressable location in storage to the
first addressable location. (4.) The continuation of
register addresses from the highest register
address to the lowest.
wrap test. A test that checks attachment or
controller circuitry without testing the device itself
by returning the output of the device as input.
Wrap To Fit. In CDE, in Text Editor, this setting
controls whether lines are automatically wrapped to
fit the window width as you enter text. If set, lines
wrap at the edge of the window. If not set, you must
press Return to end the line.
write–ahead logging. A logging mechanism
wherein all of the log records associated with a
transaction are written to the log before the
transaction actually commits. This guarantees that
those log records will be present in the log and can
therefore be used to restore recoverable data to a
correct state should the system fail at the exact
time of a transaction commit.
write back cache. In Enhanced X-Windows, GCs
cached by the library to allow merging independent
change requests into one protocol request. See
also cache.
write queue. The message queue in a module or
driver containing messages moving downstream.
Associated with output from a user process.
write verification. A mode in which the system
automatically performs a read operation after
performing a write operation. It then compares the
data to make sure they are the same.
writemask. A set of 8 or 12 bits (depending on the
frame buffer configuration), one bit for each
bitplane of the frame buffer. During any drawing
operation, only those planes enabled by a 1 (one)
in the bit mask can be altered. Planes set to 0
(zero) are marked read only.
writers. See readers and writers.
X
X.25 network. A service providing
packet–switched data transmission that conforms
to Recommendation X.25 adopted by the CCITT.
X Atom. An Enhanced X-Windows atom. See also
atom.
X.25 port. A device in the /dev directory that
corresponds to an X.25 link. See also X.25 link.
X resource. In AIXwindows, synonymous with
resource.
X.28. The CCITT recommendation that specifies
the user interface between an asynchronous
(start/stop) device and a packet
assembler/disassembler (PAD).
X resource file. In AIXwindows, an ASCII file that
includes the definition of all property values that
were specified as Public in the Widget Property
Editor. Such files are editable by the end user.
X Server. See server.
X Toolkit. See AIXwindows Toolkit.
X–Windows. A network–transparent windowing
system developed by MIT. It is the basis for
Enhanced X-Windows, which runs on the AIX
Operating System. See also X11 client.
X.3. The CCITT recommendation that specifies the
service provided to an asynchronous (start/stop)
device by a packet assembler/disassembler (PAD).
X11 client. An application that is compatible with
version X11 of Enhanced X-Windows. See also
X–Windows.
X.29. The CCITT recommendation that specifies
the user interface between a DTE and a remote
packet assembler/disassembler (PAD).
X.121. The 121st CCITT recommendation in the X
series, defining a convention for the network user
address (NUA).
XCOFF. See extended common object file format.
xcomms. The command that provides a menu
panel for other X.25 commands (the xmanage,
xroute, and xtalk commands).
XDR. See External Data Representation.
XDS. The X/Open Directory Service.
XGSL. See Graphics Support Library.
X.21. In data communications, the 21st CCITT
recommendation in the X series, defining the
connection of data terminal equipment to an X.21
public data network for digital leased and
circuit–switched services. In X.25 communications,
X.21 is available at the physical level only.
XID. See exchange identification.
X.21 bis. A CCITT recommendation, defining the
use on public data networks of DTEs designed for
interface to synchronous V series modems.
Xlib. In Enhanced X-Windows, a C language
subroutine library that client programs use to
interface with the windowing system.
X.25. The 25th CCITT recommendation in the X
series, defining the interface between data terminal
equipment and packet switching data networks.
Xlib call. See Xlib.
X.25 adapter. Synonym for X.25 Interface
Co-Processor/2.
X.25 Interface Co-Processor/2. The separately
orderable adapter card that attaches a system unit
to an X.25 packet switching data network.
Synonymous with X.25 adapter.
X.25 line. In X.25 communications, the physical
link between the DTE and the DCE, and the
service subscribed to. See also communications
line.
X.25 link. The X.25 line from the X.25 adapter to
the network terminating unit. In the X.25 API, a link
is equivalent to an X.25 port. See also X.25 port
and data link.
XID Node ID. A field that provides the node ID of
the physical unit. This value is the ID that is
exchanged with the remote physical unit when a
connection is first established during the XID
operation.
xmanage. The command that enables system
managers to manage X.25 ports.
Xmodem protocol. A communications protocol in
which messages are sent in blocks of 128
characters, surrounded by control characters. This
protocol also uses the checksum program for error
checking. The xmodem protocol can detect data
transmission errors and then retransmit the data.
xmonitor. The command that enables system
managers to monitor activity on X.25 ports.
xmpeek. A program that allows you to ask any
host about the status of its xmservd daemon.
XNS. Xerox Network Systems. The network
architecture developed by the Xerox Corporation in
the 1970s. The XNS Internet protocol suite is
Glossary
1-171
similar to the TCP/IP suite. However, different
packet formats and terminology are used.
xroute. The command that enables system
managers to manage the X.25 routing list.
Specification of X/Open Transport Interface and
fully conformant to X/OPEN and XPG4 Common
Application Environment (CAE) specification, that
defines a set of transport–level services that are
independent of any specific transport provider’s
protocol or its framework.
Xt intrinsics. See intrinsics.
XTISO. XTI over SOckets.
xtalk. The command that enables users to use
X.25 to converse with other users, exchange
messages and files, and manage X.25 address
lists.
XY format. The format of a pixmap organized as a
set of bitmaps representing individual bit planes
that appear in most–significant to least–significant
bit order. See also Z format.
XOM. X/Open Object Management.
XTI. X/Open Transport Interface. A library
implementation, as specified by X/OPEN CAE
1-172
Glossary
Y
Y/C signal. A yellow/chroma signal. Y(yellow)
represents luminance and C represents chroma
(color). The luminance contains both the image
detail and intensity levels, while the chroma has the
color information for the image.
yacc source file. File containing yacc
programming language code.
yank. To copy a word or line of text into memory.
Glossary
1-173
Z
z–buffer or z–buffering. In 3D computer graphics,
applies both to the device and the techniques
commonly used as an aid in removing hidden lines
and hidden surfaces. If z–buffering is enabled,
each pixel stores a depth value as well as a color
value. In simple terms, the depth can be thought of
as the distance from the viewer’s eye to the pixel.
Whenever a drawing routine tries to update a pixel,
it first checks the current pixel’s ”depth” or
”z–value” and will only update that pixel with new
values if the new pixel is closer than the current
pixel. The region of memory that stores the
z–values is also referred to as the z–buffer. See
also hidden surface.
Z format. The format of a pixmap organized as a
set of pixel values in scanline order. See also XY
format.
zero bit insertion and deletion. Inserting a zero
after every four 1–bits and then removing the zeros
to return the data to normal.
zero suppression. The removal or substitution of
blanks for leading zeros in a number. For example,
00057 becomes 57 when using zero suppression.
1-174
Glossary
zombie process. An ended process whose entry
remains in the process table, but to which a user or
kernel space is not allocated. A process becomes a
zombie process when it issues the exit subroutine
and the following circumstances occur: Its parent
process is not running a wait subroutine and has
not set its SIGCLD signal action to the SIG_IGN
value indicating that it does not intend to wait for its
children to finish.
zone of authority. The set of names managed by
a single name server.
zoom factor. A multiplier to determine the amount
of enlargement of a specified screen rectangle.
The x zoom factor determines the enlargement in
the x direction; the y zoom factor determines the
enlargement in the y direction.
zooming. In computer graphics, the progressive
scaling of a display image to give the visual
impression of going from a faraway view of an
image to a close–up view, or a close–up view to a
faraway view.
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