Glossary - Audentia
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Glossary
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We acknowledge the right of proprietors of trademarks mentioned in this book.
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About This Book
This glossary provides definitions of specialized terms used in the documentation library for
the AIX operating system. 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:
The Information Technology Vocabulary, developed by Subcommittee 1 of the International
Organization for Standardization and the International Electrotechnical Commission
(ISO/IEC JTC1/SC1).
The American National Standard Dictionary for Information Systems, copyright 1990 by the
American National Standards Institute (ANSI).
The IBM Dictionary of Computing, copyright 1999 by International Business Machines
Corporation.
ISO 9000
ISO 9000 registered quality systems were used in the development and manufacturing of
this product.
Preface
iii
iv
Glossary
Glossary: Contents
About This Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iii
Chapter 1. Special Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1
Chapter 2. Alphabetical List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A ......................................................................
B ......................................................................
C ......................................................................
D ......................................................................
E ......................................................................
F ......................................................................
G ......................................................................
H ......................................................................
I .......................................................................
J .......................................................................
K ......................................................................
L ......................................................................
M ......................................................................
N ......................................................................
O ......................................................................
P ......................................................................
Q ......................................................................
R ......................................................................
S ......................................................................
T ......................................................................
U ......................................................................
V ......................................................................
W ......................................................................
X ......................................................................
Y ......................................................................
Z ......................................................................
2-3
2-3
2-17
2-28
2-60
2-78
2-89
2-99
2-105
2-110
2-123
2-124
2-126
2-139
2-150
2-158
2-166
2-192
2-194
2-209
2-237
2-250
2-255
2-261
2-266
2-268
2-269
Contents
v
vi
Glossary
Chapter 1. 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 on page 2-216 and
HCONuser on page 2-106.
$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.
Special Characters
1-1
1-2
Glossary
Chapter 2. Alphabetical List
A
A
See ampere on page 2-9
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 on page 2-206.
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 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.
access
To obtain data from or to put data in storage.
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 on page 2-71.
A
2-3
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 on page 2-173.
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 on page 2-173.
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 on page 2-4.
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.
2-4
Glossary
ACL
See access control list on page 2-3.
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 on page 2-5.
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 on page 2-5.
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 on page 2-171. See also gateway on page 2-99.
active grab
In Enhanced X–Windows, a grab actually owned by the grabbing client.
Contrast with passive grab on page 2-171. See also button grabbing on
page 2-17 and grab on page 2-102.
actual parameter
The actual value passed to a routine. Contrast with formal parameter on
page 2-94.
ACU
See automatic calling unit on page 2-15 or auto–call unit on page 2-15.
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 on page 2-43 and
card on page 2-31.
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.
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.
A
2-5
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 unique code assigned to each device or
workstation connected to a network. See also network user address on
page 2-153.
(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 on page
2-182.
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 on page 2-189 .
address field
The part of a packet containing addressing information. See also packet on
page 2-166.
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 on page 2-234 and user address list on page 2-253.
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 on page 2-214.
adjust
The process of moving text to fit between the left and right margins.
ADK (Application Developer’s Kit)
The component of the iFOR/LS 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.
ADU
See automatic dialing unit on page 2-15.
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
2-6
Glossary
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 on page 2-80.
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.
Common Desktop Environment
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) on page 2-7.
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) on page 2-7.
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) on page 2-7.
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.
(4) An assumed or actual association between two data entities, or between
a data entity and a pointer.
A
2-7
aliasing
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) displa
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 on page
2-34. See also bitmapped display on page 2-19.
allocate
(1) To assign a resource, such as a disk file or a diskette file, to perform a
specific task. Contrast with deallocate on page 2-63.
(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 on page 2-8.
alphanumeric character
Consisting of letters, numbers, and often other symbols, such as
punctuation marks and mathematical symbols. See also alphabetic
character on page 2-8.
alphanumeric set
Character set composed of uppercase and lowercase letters and numbers,
but no symbols. See also alphanumeric character on page 2-8.
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 iFOR/LS 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.
2-8
Glossary
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.
amp
See ampere on page 2-9.
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.
annotation
See license annotation on page 2-128.
anonymous union
A union in C++ without a class name. It must not be followed by a
declarator.
ANSI
See American National Standards Institute on page 2-9.
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 on page 2-8.
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 on page 2-10.
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 on page 2-6.
append
(1) The action that causes data to be added to the end of existing data.
(2) In word 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.
A
2-9
Application Developer’s Kit
See ADK on page 2-6.
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 on page 2-5.
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 serve
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 on page 2-244 and service transaction program on
page 2-216.
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.
apply
2-10
Glossary
(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 on page 2-43 and
reject on page 2-198.
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.
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 on page
2-206.
archive
(1) To store programs and data for safekeeping.
(2) A copy of one or more files or a copy of a database that is saved in case
the original data is damaged or lost.
archive library A place where programs are stored for safekeeping.
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 on page 2-11 and
arithmetic operator on page 2-11.
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 on page 2-11 and arithmetic
operator on page 2-11.
arithmetic object
An integral object or objects having the float, double, or long double type.
The C 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 on page 2-11 and arithmetic constant on page
2-11.
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 on page 2-6.
A
2-11
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.
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 on
page 2-8.
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 on page
2-8.
ASCII flat file
See flat file on page 2-92.
ASCIIZ format A string ending with a null character.
ASN.1
See Abstract Syntax Notation One on page 2-3.
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
the instructions of the machine and whose data structures correspond
directly to the storage and registers of the machine.
assembly program
Synonym for assembler on page 2-12.
2-12
Glossary
assertion
See program assertion on page 2-187.
assignment compatible
Indicates whether the type of a value allows it to be assigned to a variable.
See also compatible types on page 2-44.
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 language, 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 on page 2-13.
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
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 on page 2-219. See also start–stop on page 2-225.
ATE
See Asynchronous Terminal Emulation on page 2-13.
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 on
page 2-266.
A
2-13
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 on page 2-6.
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 on page 2-176.
(3) In devices, a characteristic of a defined or configured device.
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 on page 2-14, value on page 2-255, and resource value on
page 2-203.
attribute value See attribute on page 2-14, value on page 2-255, and resource value on
page 2-203.
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.
2-14
Glossary
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 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 on page 2-141.
auto–call unit (ACU)
In X.25 communications, a device that automatically makes and answers
calls.
autodialer
See automatic dialing unit on page 2-15.
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 1.3.3 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 on page 2-226.
autonomous system
A group of networks and gateways for which one administrative authority
has responsibility. An autonomous system can be small or very large.
A
2-15
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 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 on page 2-16.
autopush
A STREAMS mechanism that enables a prespecified list of modules to be
pushed automatically onto the stream when a STREAMS device is opened.
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 on page 2-193.
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
2-16
Glossary
In Performance Toolbox, a tool used to analyze performance recordings.
B
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.
back up
To copy information, usually onto diskette or tape, for safekeeping.
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 on page 2-17.
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 on page 2-94.
See also program level on page 2-187.
(2) In CDE, the underlying area of a window on which elements, such as
buttons and lists, are displayed.
background activity
See background process on page 2-17.
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 on page 2-94.
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 on page 2-94.
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
Pertaining to a system, device, file, or facility that can be used in the event
of a malfunction or loss of data.
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.
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.
backup format file
A file in backup format.
B
2-17
backup system
See dump on page 2-76 and restore on page 2-204.
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 on page 2-18.
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 on page 2-18.
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 on page 2-71.
base register
A general purpose register that the programmer chooses to contain a base
address. Synonym for base address register. See also index on page 2-113.
base scalar type
In Pascal, the type from which a set type or subrange type is derived. See
also subrange scalar type on page 2-231.
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.
2-18
Glossary
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 on
page 2-141.
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 on page 2-18.
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 UNIX system
over a dedicated line or a telephone line. See also UNIX–to–UNIX Copy
Program on page 2-252 and UUCP login ID on page 2-254.
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
curves, and Cardinal splines all differ in that they have different bases.
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 on page 2-17.
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 on page 2-118.
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 on
page 2-22.
B
2-19
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 on page 2-20.
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 on page 2-19.
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 on
page 2-169.
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 on page 2-217.
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 on page
2-80 and little endian on page 2-131.
big endian order
The method of storage in which integer values are stored most significant
byte first. See also little endian order on page 2-131.
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 on page 2-220.
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 on page
2-39.
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 on page
2-239.
binary constant
A constant that is made up of one or more binary digits.
2-20
Glossary
binary digit
Synonym for bit on page 2-22.
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 on page 2-19.
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 on page
2-250.
(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 on page 2-219.
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 on page 2-17.
(3) For information on how to set a binding, see also set on page 2-217.
BIND
See bind session on page 2-17.
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 on page 2-154 and communications authority password on
page 2-44.
bind session (BIND)
In SNA products, a request to activate a session between two logical units.
See also bind on page 2-18.
binder
See linkage editor on page 2-130.
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 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.
B
2-21
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 on page 2-17.
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 on page 2-19.
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 on page 2-103.
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 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 on page 2-8.
bits per character
The number of bits in a data character.
blank common In FORTRAN, an unnamed common block.
2-22
blind folio
A document in which the pages of the document are counted but not
numbered. See also folio on page 2-93, dropped folio on page 2-76, and
expressed folio on page 2-86.
blit
Bit block transfer.
Glossary
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 file system, described by an i–node.
(2) A device that is accessed by means of a device driver.
block file
A file listing the usage of blocks on a disk. See also special file on page
2-223 and character special file on page 2-34.
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 on page 2-34.
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 on page 2-225.
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 on page 2-19.
BNC
A connector used with some coaxial cables.
BNU
See Basic Networking Utilities on page 2-19.
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 on page 2-75
and emphasized on page 2-79.
B
2-23
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 on page 2-114.
boot block
In a file system, the first block where the bootstrap program resides. See
also bootstrap block on page 2-22.
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 on page 2-18.
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 on page 2-33 and clipping on page 2-38.
bounds violation
An attempt to access an array using an index or pointer that references
storage outside of the array.
2-24
box
A line enclosure around text or a table.
bpi
Bits per inch, a measure of linear density for storage products.
Glossary
bps
Bits per second. In serial transmission, the instantaneous bit speed with
which a device or channel transmits a character. See also baud on page
2-19.
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 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 on page 2-99.
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.
B
2-25
broadband channel
A data transmission channel 6 MHz wide. Synonym for wide band channel
on page 2-261.
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 on page 2-133.
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 on page 2-17.
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 on page 2-169.
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 on page 2-22.
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.
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.
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.
2-26
Glossary
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–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.
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.
button grabbing
Enacting an active grab using a mouse button. See also grab on page
2-102, pointer grabbing on page 2-177, key grabbing on page 2-124,
passive grab on page 2-171, and active grab on page 2-5.
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 on page 2-22.
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.
B
2-27
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.
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.
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.
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 on page 2-265.
(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.
cache hit
A processor storage reference that is satisfied by information from a cache.
cache line
The cache component that is normally loaded, stored, and interrogated
during cache lookup. See also set associativity on page 2-217.
cache line tag The information kept with each cache line to identify the part of virtual
storage it contains.
2-28
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.
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.
Glossary
CAD/CAM
Computer–Aided Design/Computer–Aided Manufacturing.
CAI
See computer–aided instruction on page 2-47.
Calculator
In CDE, a software application that mimics the function of a handheld
calculator.
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 on page 2-131.
(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 on
page 2-166.
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 on page 2-40.
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 on page 2-166.
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 on page
2-166.
call user data (CUD)
In X.25 communications, data optionally included in the call–request packet
by the user application.
callback
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 on page 2-28. See also callback
routines on page 2-29.
callback function
Synonym for callback on page 2-29.
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.
C
2-29
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 on page 2-29.
called
In X.25 communications, an adjective applied to the location or user to
which a call is made.
called address extension
See address extension on page 2-6.
called DLS user
The data link service (DLS) user in connection mode that processes
requests for connections from other DLS users.
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 on page 2-229.
calling
In X.25 communications, an adjective applied to the location or user that
makes a call.
calling address
See network user address on page 2-153.
calling address extension
See address extension on page 2-6.
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.
2-30
Glossary
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.
caption
Text associated with, and describing, a table or figure.
capture
To digitize an image into the video memory of the M–Video Capture
Adapter.
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 on page 2-5.
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 on page 2-169.
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 on page 2-52.
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.
C
2-31
cast
In C language, an expression that converts the value of the operand to a
specified scalar data type (the operator).
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 on page 2-68.
CBEMA
Computer and Business Equipment Manufacturers Association.
CCITT
Comite Consultatif International Telegraphique et Telephonique. See also
Consultative Committee on International Telegraphy and Telephone on
page 2-51.
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 on page 2-63.
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.
2-32
CDSPI
Cell Directory Service Portable Interface.
CDSTL
See connect data set to line on page 2-49.
Glossary
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 on page 2-132.
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 on page 2-47.
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 on page 2-134.
channel control word
See CCW on page 2-32.
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 on page 2-239.
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 on
page 2-17.
C
2-33
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 on page 2-34.
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 on page 2-8.
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 on page 2-98.
(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 on page 2-157.
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 on page 2-34, block file on page 2-20, special file on page
2-223 , and block special file on page 2-20.
character string
A sequence of consecutive characters. In the C programming language, a
string must be null–terminated.
2-34
Glossary
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
on page 2-62.
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.
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 on page 2-105 and expect–send sequence on page 2-85.
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 on page 2-170.
(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 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 on page 2-36.
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.
C
2-35
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 on page 2-35.
children
Plural of child on page 2-35.
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 on page 2-58.
CID
See connection identifier on page 2-50.
ciphertext
The output of an encryption function. Encryption transforms plaintext into
ciphertext.
circuit
See virtual circuit on page 2-258.
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 on page 2-167.
C–ISAM
C–language Indexed Sequential Access Method.
CLA
See communications line adapter on page 2-43.
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 on page 2-262 and class record on page
2-37.
(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 on page 2-158.
(5) In Workload Management, a collection of processes (and their
associated threads) that have a single set of resource limitation values and
target shares applied to them.
class assignment rule
Indicates what set of process attribute values determine which class a
process is assigned to.
class key
2-36
Glossary
One of the C++ keywords: class, struct, and union.
class library
A collection of C++ classes.
class member operators
Used to access C++ class members through class objects or pointers to
class objects. They are ., –>, .*, and –>*.
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 record
A particular widget record that contains the data objects pertaining to the
class of any given widget. See also record on page 2-196, widget record on
page 2-262, and class on page 2-36.
class scope
The scope of C++ class members.
class template A blueprint describing how a set of related C++ classes can be
constructed.
class tier
The tier value of Workload Management classes specify which classes are
most important. If no tier value is used, all classes are equally important.
Resource limits (including the resource targets) of all classes in a higher tier
are favored over those of classes in any lower tier.
classification mechanism
A set of Workload Management class assignment rules that determine the
classes to which processes are assigned.
CLAW
See Common Link Access to Workstation on page 2-43.
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 cause
See cause code on page 2-32.
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 on page 2-40 .
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 on page 2-166.
clear diagnostic
See diagnostic code on page 2-68.
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 on page 2-166.
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 on page 2-166.
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2-37
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 on page 2-120.
(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 on page 2-38.
(5) In NCS, a program that uses an interface to make remote procedure
calls (RPCs).
client agent
See Location Broker Client Agent on page 2-133.
client application
A type of application. See also client on page 2-38 and application on page
2-9.
client program A program that uses a C++ class. The program is said to be a client of the
class.
client–side caching
A high–speed buffer storage that contains frequently accessed information
associated with a client application. The primary 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
2-38
Glossary
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 on page 2-39, fine clipping on page
2-91, gross clipping on page 2-103, screenmask on page 2-210, bounding
box on page 2-17, culling on page 2-57, transformation on page 2-245, and
window on page 2-263.
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 on page 2-103, clipping on page
2-38 and frustum on page 2-97.
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 on page 2-39.
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 on page 2-161.
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 on page 2-20 and optional
facility on page 2-162.
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. (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.
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2-39
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 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 on page 2-40 and
extended character on page 2-86.
(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 on page 2-40 and
extended character on page 2-86.
code segment See segment on page 2-213.
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
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 on
page 2-198.
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.
2-40
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 channel. This can be a
clear collision, call collision, or reset collision. See also clear collision on
page 2-37.
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.
Glossary
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 on page 2-41.
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 on
page 2-205.
color palette
Synonym for color map on page 2-41.
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 on page 2-41.
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.
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2-41
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 on
page 2-119. See also shell on page 2-218.
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 on page 2-240.
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.
2-42
Glossary
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 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 on
page 2-10 and contrast with reject on page 2-198 and remove on page
2-201.
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 on page
2-5.
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2-43
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 on page 2-17.
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.
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 on page 2-266.
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 on page 2-129.
communications link
See data link on page 2-61.
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 on page 2-45. See also unit on
page 2-251.
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.
2-44
Glossary
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 on page 2-44 and external variable on page 2-88.
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 on page 2-120.
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 on page 2-45.
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.
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2-45
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 on page 2-262.
Composite widget class
In Enhanced X–Windows, a metaclass that does not instantiate any widgets
of its own but provides the resources 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.
2-46
Glossary
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 on page 2-47.
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 on
page 2-139.
computer language
Synonym for machine language on page 2-139 and machine instruction on
page 2-139.
computer word
Synonym for word on page 2-263.
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.
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2-47
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 on page 2-92.
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).
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.
condition variable
A synchronization object used in conjunction with a mutex. A condition
variable allows a thread to block until some event happens.
2-48
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.
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 on page 2-58 and system
customization on page 2-220.
Glossary
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).
configure
To describe to a system the devices, optional features, and program
products installed on a system.
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.
confirm
In X.25 communications, to respond to the arrival of a clear–indication or
reset–indication packet.
CONFIRM
A request that asks the remote transaction program to tell whether the last
transmission was received successfully.
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 on page 2-94.
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.
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2-49
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 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.
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.
2-50
Glossary
connectionless packet delivery
A method of data packet delivery that treats each packet of 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
on page 2-220.
console bell
Synonym for BEL on page 2-20.
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 on page 2-255. For Ada programming, see
also object on page 2-158.
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 on page 2-93.
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.
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.
constraint widget
In Enhanced X–Windows, a widget that is a subclass of a composite widget.
It manages the geometry of its children based on constraints associated
with each child.
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.
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.
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contact port
Synonym for well–known port on page 2-261.
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 on page 2-45.
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 on page 2-226. See
also cascading menu on page 2-31.
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.
2-52
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 on page 2-96.
control block
A storage area used by a program to hold control information.
Glossary
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 key followed by another
key on the keyboard, that performs a function or makes a special character.
control path
The set of line, hardware, and control disciplines that determine the current
characteristics of a particular TTY.
control point profile name
The name of the control point profile that defines the node ID of the physical
unit associated with the attachment.
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.
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2-53
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 on page 2-54.
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. Convenience
functions are included in the AIXwindows Toolkit.
convenience interface
An interface created by an AIXwindows convenience creation subroutine.
See also convenience creation subroutine on page 2-54.
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.
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 on page 2-216.
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 on page 2-244.
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.
2-54
Glossary
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.
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 on page 2-262.
corequisite
A product or update that must be installed concurrently with another
specified product or update.
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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 on page 2-53.
CPS
Characters per second.
CPU
See central processing unit on page 2-33.
CPU lock
See nodelocked license on page 2-154.
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 on page 2-30.
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 on page 2-216
and system date on page 2-220.
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.
2-56
CRQ
See call request on page 2-29.
CRT
See cathode ray tube on page 2-32.
CSC
See core sequence controller on page 2-39.
CSMA/CD
See carrier sense multiple access with collision detection on page 2-31.
CSX
Host–based diagnostics program.
Glossary
C–stub
The part of the DUA that implements the connection with the
communications network.
CTC
Channel–to–channel.
CTS
Clear to send. Used with EIA–232 protocol.
CUD
See call user data on page 2-29.
CUG
See closed user group on page 2-39.
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 on page 2-38 and pruning on page 2-174.
(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.
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.
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.
current host
Synonym for local host on page 2-132.
current line
The line on which the cursor is located.
current record (1) The record pointed to by the current line pointer.
(2) The record that is currently available to the program.
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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 on
page 2-108.
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 on page 2-245 and matrix stack on page 2-142.
current window
The window to which the system directs the output from graphics routines.
See also window on page 2-263.
current working directory
Synonym for current directory on page 2-57.
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 on page 2-48. See also system
customization on page 2-220.
2-58
Glossary
customization profile
A file containing the descriptions of optional changes to the default settings
of a device or a software program. See also profile on page 2-186.
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 on
page 2-49.
Customized Database
An entity within the ODM that contains configuration data for defined or
available devices in the system. See also Device Configuration Database
on page 2-67 and Predefined Database on page 2-181.
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 on page 2-53.
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.
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D
DAC
See digital–to–analog converter on page 2-69.
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.
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.
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 on page 2-19.
data cache
A cache for providing data to the processor faster than it can be obtained
from RAM.
data cache unit (DCU)
See cache on page 2-28.
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 establish, maintain, and end a
connection, and the signal conversion and coding between the data
terminal equipment (DTE) and the line.
data communications
See communications on page 2-43.
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 on page
2-38. Contrast with data supplier on page 2-62.
2-60
Glossary
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.
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 on
page 2-266.
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 on page 2-96. See also packet level on page
2-167 , physical level on page 2-175.
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 on page
2-158.
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 on page
2-166.
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.
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2-61
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 on page 2-227.
data supplier
In Performance Toolbox, a program that supplies statistics across a
network. Synonymous with server. Contrast with data consumer on page
2-60.
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 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 on page 2-35
and type on page 2-248.
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.
2-62
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 on page 2-63.
DB
Database.
DBA
See direct–bus attached on page 2-70.
DBCS
See Double–Byte Character Set on page 2-74.
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 on page 2-63.
Glossary
DCD
Data carrier detect used with EIA–232 protocol. See also CD on page 2-32
and decode on page 2-64.
DCE
See Distributed Computing Environment on page 2-73 and
data–circuit–terminating equipment on page 2-60.
DCN
Distributed Computer Network.
DCU
Data cache unit. See also cache on page 2-28.
DD
See device driver on page 2-68.
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 on
page 2-8.
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.
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.
D
2-63
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 on page 2-64, simple name on page 2-219, scope on page 2-210,
and name on page 2-150.
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 on page 2-64.
decode
(1) To convert data by reversing the effect of some previous encoding.
(2) To interpret a code. See also DCD on page 2-63.
default
A value, attribute, or option that is assumed when no alternative is
specified by the user. See also d efault value on page 2-65.
default accelerators
See accelerator on page 2-3.
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 iFOR/LS configurations because it allows all
other iFOR/LS 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.
2-64
Glossary
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 on page 2-65.
default label
See label on page 2-126.
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 on page 2-64 and default initialization on page 2-65.
defaults file
See default files on page 2-65.
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 on page 2-65.
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 on page 2-82.
(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 on page 2-62.
delta
The finite increment of a variable.
D
2-65
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 on page 2-60.
denote
See declaration on page 2-64.
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.
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 on page
2-182
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 on page 2-80.
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 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 on page 2-170.
DES
See Data Encryption Standard on page 2-61
descendant
See child on page 2-35.
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.
2-66
Glossary
descriptor
(1) In ODM, a named and typed variable that defines a single characteristic
of an object. See also terminal descriptor on page 2-239, link descriptor on
page 2-130, and method descriptor on page 2-144.
(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.
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 on page 2-68.
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 on page 2-181 and Customized Database on page
2-29.
device definition
Information about a device that is in the Customized Database including
attributes and connection locations.
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.”
D
2-67
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.
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 on page
2-135.
device number The reference number assigned to any external device.
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.
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.
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 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.
2-68
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 on page 2-67.
DFT
See distributed function terminal on page 2-73.
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.
Glossary
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 on page 2-32.
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.
dial
(1) A computer input device that allows a user to set parameter values.
Dials are a type of valuator. See also valuator on page 2-255.
(2) An I/O device used to input variables by way of thumbwheels.
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).”
dial–code
In BNU, a code representing a telephone number or portion of a telephone
number.
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.
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 on page 2-69.
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 on page 2-69.
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.
D
2-69
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.
direct–bus attached
Used in relation to the fixed disk drives attached directly to the system
board rather then through a SCSI adapter card.
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.
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 visibility See visibility on page 2-259.
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.
2-70
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 on page 2-223.
(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 on page 2-71.
Glossary
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.
disable
(1) To make nonfunctional. In interactive communications, to disconnect or
stop a subsystem. Contrast with enable on page 2-79.
(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 on page 2-91 and shortest–job–next on page
2-219.
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 on page 2-3, base permission on page 2-18, and
extended permission on page 2-87.
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.
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 on page 2-74.
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.
D
2-71
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 method
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 on page
2-147.
display device See display on page 2-72.
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 PostScript (DPS)
Extension to X server created by Adobe.
display screen The part of the display device that displays information visually.
Synonymous with terminal screen. See also screen on page 2-210.
display session
A 3270 Host Connection Program 2.1 and 1.3.2 (HCON) mode of operation
during interaction with a host computer that emulates a 3278/79 terminal
display.
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.
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.
2-72
Glossary
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 on page 2-96.
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.
distributed transaction
A transaction which can update data in many user processes on many
machines.
distribution medium
The medium on which the operating system software, a licensed program,
or 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 on page 2-61.
DLE
See data link escape character on page 2-61.
DLPI
Data Link Provider Interface.
DLS
Data link service.
D
2-73
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 on page 2-71.
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
on page 2-219.
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
2-74
Glossary
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 on page 2-167.
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 of
double–strike is emphasized printing. See also boldface on page 2-18 and
emphasized on page 2-79.
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 on page 2-72.
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 on page 2-77.
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.
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.
D
2-75
dropped folio
A page numbering style in which the page number is printed at the foot of
the page. See also folio on page 2-93, blind folio on page 2-19, and
expressed folio on page 2-86.
dropping locks Releasing the locks that a transaction holds on data.
DSI
See data storage interrupt on page 2-61.
DSR
Data set ready; used with EIA–232 protocol. See your modem manual for
more information.
DTE
See data terminal equipment on page 2-62.
DTR
See data terminal ready on page 2-62.
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 on page
2-94.
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
on page 2-105.
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 on page 2-72.
dyadic operator
Synonym for binary operator on page 2-20.
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 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.
2-76
Glossary
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 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 on page 2-228.
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.
D
2-77
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 on page 2-86.
EBCDIC character
Any one of the symbols included in the 8–bit EBCDIC set.
EC
Engineering Change level.
ECB
(1) See event control bit on page 2-83.
(2) Event control block.
(3) Electronic codebook.
ECC
(1) See error–checking and correction on page 2-82.
(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 original login ID. All discretionary access
decisions are based on the effective user ID.
2-78
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.
Glossary
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 on page 2-139.
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 on page 2-143.
(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 on page 2-79.
embedded blanks
Blanks that are surrounded by any other characters.
EMC
See electromagnetic compatibility on page 2-79.
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 on page 2-18 and double–strike
on page 2-75.
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 on page
2-79.
enable
(1) To make functional.
(2) In interactive communications, to load and start a subsystem. Contrast
with disable on page 2-71.
E
2-79
encapsulation 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.
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 on page 2-20 and little endian on
page 2-131.
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 on page 2-6.
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 on page 2-7.
enqueue
To place items in a queue. Contrast with dequeue on page 2-66.
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 on page 2-83.
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 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.
entry poin
(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.
2-80
Glossary
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 on
page 2-81.
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 on page 2-81.
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 named collection of logical and physical resources used to support the
performance of a function.
(3) In Common Desktop Environment, the set of rule files, resources, and
message files that define the appearance and behavior of a specific
desktop configuration.
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 on page 2-80 or Entry Point Vector.
E
2-81
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 on page 2-65.
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 on page 2-82.
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 on page 2-69.
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
2-82
Glossary
Identifies whether an error log entry is for a permanent failure, temporary
failure, performance degradation, impending loss of availability, or
undetermined failure.
ESC
See escape character on page 2-83.
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 on
page 2-251.
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 on page 2-81.
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 on page 2-29.
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 mask
In computer graphics, the set of event types that a client requests relative
to a window.
E
2-83
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.
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
on page 2-120 and signal on page 2-219. See also handler on page 2-105
and trap handler on page 2-246.
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++.
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 on page 2-217.
exec
To overlay the current process with another executable program. See also
fork on page 2-94.
EXEC
Remote Command Execution Protocol.
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.
2-84
Glossary
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 on page 2-105 and chat
script on page 2-35.
expedited data negotiation
In X.25 communications, an optional CCITT–specified facility.
expedited data transfer
In X.25 communications, an optional CCITT–specified facility.
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 on page 2-111.
(2) To copy data onto removable media.
E
2-85
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 on page 2-93,
blind folio on page 2-19, and dropped folio on page 2-76.
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 on page 2-6.
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 on page 2-40 and code point on page 2-40.
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 Server. These calls contain an extra
parameter on the call (a pointer to the structure containing extra function
requests). See also interface on page 2-119 and limited interface on page
2-129.
2-86
Glossary
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 on page 2-71.
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
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.
external function
In FORTRAN, synonymous with external routine on page 2-88.
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 on page 2-88.
E
2-87
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
on page 2-45.
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 on page 2-146, primitive
coordinates on page 2-184, world coordinates on page 2-265, screen
coordinates on page 2-210, and transformation on page 2-245.
eye space
2-88
Glossary
Synonym for eye coordinates on page 2-88.
F
F
Fahrenheit.
facilities
See optional facilities on page 2-162.
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.
fake target nam
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 on page
2-162.
FCC
Federal Communications Commission.
FCFS
See first–come–first–served on page 2-91.
FD
Full duplex. See duplex on page 2-76.
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 on page 2-76.
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 video, a field is one–half of a frame. Fields are drawn 60 times per
second. See also structured field on page 2-229.
field of view
In GL, the extent of the area which is under view. The field of view is
defined by the viewing matrix on page 2-257 in use.
F
2-89
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 on page 2-91.
file
(1) A collection of related data that is stored and retrieved by an assigned
name. Contrast with special file on page 2-223.
(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 on
page 2-91.
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) on page 2-217.
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
on page 2-114.
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 on page 2-141.
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 on page
2-126.
file name substitution
The process in which the shell recognizing a word (character string) that
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 on page 2-90.
file specification (filespec)
he name and location of a file. A file specification consists of a drive
specifier, a path name, and a file name.
2-90
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.
Glossary
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 on page 2-90.
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 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 on page 2-38 and gross clipping on page 2-103.
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 on page 2-91. Contrast with shortest–job–next on page
2-219. See also discipline on page 2-71.
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 on page 2-91.
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.
F
2-91
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 on page 2-187, modification
number on page 2-141, release number on page 2-199, version on page
2-256, and version number on page 2-257.
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.
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.
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 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 on page 2-196.
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 on page 2-91.
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 optional sign (+
or –), and one or more digits (0 through 9).
2-92
Glossary
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
on page 2-226.
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 on page 2-48.
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 on page 2-93.
floating–point exception
See exception on page 2-84.
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 on page 2-93.
floating point type
See real type on page 2-196.
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 on page 2-96.
FM Header
Function Management Header.
focus window Synonym for input focus on page 2-115.
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 the
letters.
(2) To translate the lowercase characters of a character string into
uppercase. See also constant folding on page 2-51.
(3) To place on the next line a portion of a line that does not fit on the line.
Contrast with truncate on page 2-247.
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 on page 2-19,
dropped folio on page 2-76, and expressed folio on page 2-86.
F
2-93
font
(1) A set of characters in a particular style. See also raster font on page
2-194 and primitive font on page 2-184.
(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 on page 2-94.
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
on page 2-94.
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 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 on page 2-17.
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 on page 2-17.
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 on page 2-17.
foreign cell
A cell other than the one to which the local machine belongs. See also
local cell on page 2-132.
foreign host
Synonym for remote host on page 2-200.
fork
To create and start a child process. See also exec on page 2-84.
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 on page
2-49 and dummy argument on page 2-76. For Ada programming, see also
parameter on page 2-169. Contrast with actual parameter on page 2-5.
2-94
Glossary
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 on page 2-94.
formatted data Data that is transferred between main storage and an input/output device
according to a specified format. See also list–directed data on page 2-131
and format on page 2-95.
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 on page 2-95.
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 on page 2-194.
F
2-95
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 on page 2-61 and
level 2. See also level on page 2-127, packet level on page 2-167, and
physical level on page 2-175.
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 on page
2-167.
frame window In X.25 communications, the number of frames that can be outstanding
without acknowledgment. See also packet window on page 2-167 and
window on page 2-263.
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 on page 2-96.
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
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 on page 2-52.
2-96
Glossary
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 on page
2-39.
FTP
File Transfer Program. See also File Transfer Protocol on page 2-91.
full backup
Backup copies of all the files on the system. Contrast with incremental
backup on page 2-112.
full duplex (FDX)
Synonym for duplex on page 2-76.
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 on page 2-105.
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 on page
2-97, path name on page 2-172, and relative path name on page 2-199.
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 on page 2-263.
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 on page 2-97.
function
(1) A specific purpose of an entity, or its characteristic action.
(2) A machine action such as 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 on page 2-185. For Ada programming, see
also subprogram on page 2-230.
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).
F
2-97
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 on
page 2-34.
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 on page 2-97.
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.
2-98
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 on page 2-98.
FXU (FX)
Fixed–point unit.
Glossary
G
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.
gadget ID
In AIXwindows, a unique identification number assigned to each instance
of a gadget used within a given graphical interface.
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 on
page 2-99.
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 on page
2-99. 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 on page 2-5.
(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 on page 2-25.
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 on page 2-210.
GB
See gigabyte on page 2-101.
GC
See graphics context on page 2-102.
GC caching
In Enhanced X–Windows, allows independent change requests to be
merged into one protocol request.
GContext
See graphics context on page 2-102.
GCP
Graphics Control Processor.
GCR
Group Code Recording, a magnetic tape recording format with a density of
6250 bpi.
GDA
Global Directory Agent.
GDLC
See generic data link control on page 2-100.
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 on
page 2-198.
G
2-99
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 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. on page 2-116.
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 on page 2-188 or stroke text on page
2-228.
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 on page 2-126 and geometry management.
geometry management
Synonymous with geometry on page 2-100.
2-100
GGP
See Gateway–to–Gateway Protocol on page 2-99.
ghost icon
An icon that indicates that a file is missing.
Glossary
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.
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.
GID
See group number on page 2-103.
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 on page 2-101.
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 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.
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.
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.
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.
Global Location Broker (GLB)
Part of the NCS Location Broker. A server that maintains global information
about objects on a network or an internet.
global variable A symbol defined in one program module but used in other independently
assembled program modules.
globbing
Synonym for file name substitution on page 2-90.
glossary window
A window that contains a glossary term.
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.
G
2-101
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 on page 2-99.
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 on page 2-5 , passive grab
on page 2-171 , button grabbing on page 2-17 , pointer grabbing on page
2-177, and key grabbing on page 2-124.
(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.
grab handles (or handles)
In CDE, the small squares displayed at the corners and midpoints of a
selected graphic element.
grammar rules The structure rules in a parser program. See also parser on page 2-170.
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.
graphic character
A character that can be displayed or printed.
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.
2-102
Glossary
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.
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 on page 2-19 and window gravity on page
2-263.
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 on page
2-147.
grayed
A characteristic of a command or option that is listed on a menu or list box
but cannot be chosen.
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 on page 2-38, fine clipping on page 2-91, and clipping planes on
page 2-39.
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 on page 2-103.
G
2-103
guard expressions
Expressions placed at the beginning of Boolean expressions to check that
other operations can be done.
2-104
Glossary
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 on page 2-76.
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 on page 2-97.
half–session
A component that provides data flow control and transmission control at
one end of a session.
halfword
A contiguous sequence of bits or characters that constitutes half a
computer word and can be addressed as a unit. Contrast with word on page
2-263.
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.
handler
A software routine that controls a program’s reaction to specific external
events, such as an interrupt handler. For Ada programming, see exception
on page 2-84.
handshaking
The process used by modems and equipment, before transmitting data, to
establish an electrical path and synchronization. See also chat script on
page 2-35 and expect–send sequence on page 2-85.
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 on page 2-92.
hard–disk drive
See fixed–disk drive on page 2-92.
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 on
page 2-221.
hash codes
Format in which data is stored in compressed form.
hash signature The fixed–length bit string resulting from hashing a character string.
Character strings may be compared quickly by comparing their hash
signatures.
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.
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.
H
2-105
HCON
See 3270 Host Connection Program 2.1 and 1.3.3. on page 1-1
HCONMRI
3270 Host Connection Program 2.1 and 1.3.3 Message Catalog.
HCONuser
A user who has been given the special permissions necessary to use the
3270 Host Connection Program 2.1 and 1.3.3 (HCON). See also 3270 Host
Connection Program 2.1 and 1.3.3 on page 1-1.
HD
See half duplex on page 2-105.
HDLC
See high–level data link control on page 2-107.
HDR
See header label on page 2-106.
HDX
See half duplex on page 2-105.
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.
header file
A text file that contains declarations used by a group of functions or users.
Synonymous with include file on page 2-112.
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.
2-106
Help Viewer
In CDE, the software application that displays online help.
help volume
In CDE, a complete body of help information about a subject.
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 on page 2-107.
Glossary
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 on page 2-234.
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 on page 2-269.
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 on page
2-127.
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.
H
2-107
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 on page 2-175, picking region on page 2-175,
selecting region on page 2-213, and selecting on page 2-213.
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 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 on page 2-222.
Hollerith constant
In FORTRAN, a string of any characters capable of representation in the
processor and preceded by n H, where n is the number of characters in the
string.
HOME
See $HOME on page 1-1.
home cell
See local cell on page 2-132.
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 on page 2-58.
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 on page 2-169.
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.
hooking routines
Functions that connect with the library but remain outside the library;
protocol extension procedures. Synonym for stub on page 2-229.
hop count
2-108
Glossary
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.
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 on page 2-109.
hypertext link A connection between one piece of online information and another. See
also hypertext on page 2-109.
Hz
See hertz on page 2-106.
H
2-109
I
IAR
See instruction address register on page 2-117.
IC
See ICU on page 2-110.
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 on page 2-110.
ICCCM
Inter–Client Communications Conventions manual. See also ICCC on page
2-110.
ICMP
See Internet Control Message Protocol on page 2-120.
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 Common Desktop Environment, 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.
icon box
In AIXwindows, a window used as a visual storage area for icons
representing minimized windows.
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.
2-110
iconify
See icon on page 2-110.
ICU (IC)
Instruction cache unit.
ID
Identification. See identifier on page 2-110.
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 the resource. An identifier can be used
over any connection to name the resource.
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.
IDP
Internet Datagram Protocol. A simple, unreliable datagram protocol, which
is used to support the SOCK_DGRAM abstraction for the Internet Protocol
family.
IEEE
Institute of Electrical and Electronics Engineers.
Glossary
IEEE 754
Binary Floating Point Standard.
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 on page 2-114 and superblock on page 2-218.
illegal
A violation of an architecture rule that an implementation is required to
report. See also unpredictable on page 2-252.
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 on page 2-176.
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.
I
2-111
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 on page
2-85.
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 on page 2-112.
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 on page 2-115.
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 on page 2-106. See also
include statement on page 2-112.
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 on page 2-112.
incoming call
In X.25 communications, a call arriving at the data terminal equipment
(DTE).
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 on page
2-166.
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 on page 2-97.
2-112
Glossary
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 on page 2-18.
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.
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.
indexed instruction
An instruction that uses an indexed address.
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.
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
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.
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2-113
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.
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 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 on page 2-114.
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 on page 2-114.
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 on page 2-90. See also
i–list on page 2-111 and i–node number on page 2-114.
i–node number A number specifying a particular i–node file in the file system. See also
i–node on page 2-114.
inodetab
2-114
Glossary
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, DVD 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 on
page 2-112.
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.
I
2-115
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 Common Desktop Environment, the point at which text is inserted when
you type. It usually appears as a flashing vertical line or underline.
2-116
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.
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.
Glossary
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 on page
2-262 and instance record on page 2-116. For Ada programming, see
generic unit on page 2-100.
(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 record
A particular widget record that contains the data objects pertaining to the
identity of any given widget as an instance. See also record on page 2-196,
widget record on page 2-262, and instance on page 2-116.
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 on page 2-187. See also location counter on page 2-133.
I
2-117
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 on page 2-117.
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 on page
2-19.
2-118
Glossary
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 on page 2-42.
(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 on page 2-218.
(5) A set of operations. The Network Computing Architecture specifies a
Network Interface Definition Language for defining interfaces. See also
extended interface on page 2-86 and limited interface on page 2-129.
interface, extended
See extended interface on page 2-86.
interface icon Any pictorial representation of a selection choice appearing within an
interface.
interface, limited
See limited interface on page 2-129.
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.
interlanguage call
In a program written in a given language, any reference to a procedure
written in a different language.
intermediate data type
Any of the basic data types in terms of which the other, substantive data
types of the interface are defined.
intermediate nodes
On the widget tree, widgets with one or more children. See also widget tree
on page 2-262.
intern
The procedure of defining an atom.
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 on page 2-150.
International Standards Organization (ISO)
An international body that standardizes goods and services. For Enhanced
X–Windows, standards relating to character sets and fonts.
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2-119
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.
internetwork
Any wide area network connecting more than one network.
interoperability
Ability of a system or a product to work with other systems or products
without special effort on the part of the customer. Becomes a quality of
increasing importance for information technology products as the concept
that ”the network is the computer” becomes a reality.
interpreted routine
A routine that decodes instructions written as pseudocodes and
immediately executes those instructions. See also compile on page 2-44.
interpreter
A tool that allows a program to be run immediately, without recompiling or
relinking.
interprocedural analysis
The process of inspecting referenced procedures for information on
relationships between arguments, returned values, and global data.
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 on
page 2-38.
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 on page 2-84 and signal on page 2-219.
interrupt–confirmation packet
In X.25 communications, a packet used to acknowledge the receipt of an
interrupt packet. See also packet on page 2-166.
2-120
Glossary
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 on
page 2-166.
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 on page 2-121.
I/O
See input/output on page 2-115.
I/O channel
See input/output channel on page 2-115.
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. on page 2-115
IOCDS
I/O configuration data set.
IOT fault
A signal (SIGIOT) that abnormally ends a process.
IOU (IO)
Input/output unit.
IP
See Internet Protocol on page 2-120.
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 on page 2-120.
IPL
See initial program load on page 2-114.
IPL device
initial program load device.
I
2-121
ips
Inches per second, a measure of tape drive speed and performance.
ISC
See initial sequence controller on page 2-114.
ISO
See International Standards Organization on page 2-119.
ISO 7776
The ISO description of LAPB–compatible DTE data link procedures.
ISO 8208
See X.25 on page 2-266.
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.
2-122
ITE
In CDE, Internal Terminal Emulator. ITE allows use of a bitmapped display
as a terminal (through command–line mode from the login screen).
item
The data in one line of an indexed field.
Glossary
J
Japanese Industry Standard (JIS)
A standard of coding character sets.
Japanese Shift–In start delimiter
In SNA Server, an optional feature supported by X.21 Physical Link Control.
JIS
See Japanese Industry Standard on page 2-123.
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 on page
2-186.
job number
A number assigned to a job as it enters the system to distinguish the job
from other jobs.
job queue
A list of jobs waiting to be processed by the system.
journaled file system
The standard sequential structure of database files used in this operating
system.
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.
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.
J
2-123
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 on page 2-125.
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 on page 2-68.
kernel dump
Synonym for system dump on page 2-220.
kernel mode
The state in which a process runs kernel code. Contrast with user mode on
page 2-254.
kernel parameters
Variables that specify how the kernel allocates certain system resources.
Synonymous with system parameters.
2-124
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 on page 2-124.
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 on page 2-102, button grabbing on page
2-17, pointer grabbing on page 2-177, active grab on page 2-5 and passive
grab on page 2-171.
key pad
A physical grouping of keys on a keyboard such as the numeric key pad
and the cursor key pad.
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
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.
Glossary
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 on
page 2-141.
keyboard send–receive
See keyboard send–receive mode on page 2-125.
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 on page 2-125.
kill
An operating system command that stops a process.
kill character
Character that deletes a line of characters entered after a prompt.
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.
KSR
See keyboard send–receive mode on page 2-125.
KTS
Key Telephone System. A private telephone system requiring manual
selection of outside lines.
kVA
Kilovolt–ampere, or 1000volt–amperes.
K
2-125
L
L1 cache
The first cache accessed when a storage reference occurs.
L2 cache
The cache that is accessed, on certain ESCALA 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 on page 2-90.
(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 on page 2-225.
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 on page 2-132.
landscape display
A rectangular display wider than it is high. See also portrait display on page
2-180.
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.
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.
LAP
See link–access procedures on page 2-130.
LAPB
Link–access procedure balanced. See also link–access procedures on
page 2-130.
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 on page 2-240.
2-126
latency
The time from the initiation of an operation until something actually starts
happening (for example, data transmission begins).
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 on page 2-100.
lb
See pound on page 2-181.
LC
See link control on page 2-130.
LCN
See logical channel number on page 2-134.
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 on page 2-167.
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.
Glossary
leap seconds
An infrequent adjustment to UTC to account for the irregularity of the
earth’s rotation.
leased facility Synonym for nonswitched line on page 2-155.
leaves
On a widget tree, widgets with no children. See also widget tree on page
2-262.
LED
See light–emitting diodes on page 2-129.
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.
length specification
A source language specification of the number of bytes to be occupied by a
variable.
letter
An uppercase or lowercase character from the set A through Z.
level
(1) The version of a software application program.
(2) See also higher layer on page 2-107.
(3) In X.25 communications, see also physical level on page 2-175, packet
level on page 2-167, and frame level on page 2-96.
level 1
Synonym for physical level on page 2-175.
level 2
Synonym for frame level on page 2-96.
level 3
Synonym for packet level on page 2-167.
lexical analyzer
A program that analyzes input and breaks it into categories, such as
numbers, letters, or operators.
lexical element In Ada language, an identifier, a literal, a delimiter, or a comment.
lexical level
The depth to which routines are nested within one another, which
determines the scope of the identifiers declared within those routines.
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 routine declares an item with the same name,
the outer item is not available in the nested routine.
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.
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.
L
2-127
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.
license annotation
A special data string that modifies the use of a license in a manner defined
by the vendor of the software product.
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.
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.
license password
A string encoded with license information for a software product.
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.
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.
iFOR/LS
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, iFOR/LS allows
customers to easily comply with their software license agreements.
iFOR/LS 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
2-128
Glossary
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.
lighted programmable function keyboard (LPFK)
An input device used primarily in graphic applications and that has lighted
keys under control of an application program.
limited interface
A set of system calls that provides a limited function interface. See also
interface on page 2-119 and extended interface on page 2-86.
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.
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 on page 2-266.
line adapter
A functional unit that converts the serial–by–bit input to a station. See also
communications line adapter on page 2-43.
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 on page 2-166.
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 on page 2-36.
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.
linefeed
An ASCII character that causes an output device to move forward one line.
linestyle
The pattern used to draw a line. A linestyle might be solid or broken into a
pattern of dashes.
L
2-129
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 on page 2-266. (6.) See hypertext link on page 2-109.
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
on page 2-126.
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 on page 2-135.
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 on page 2-67.
link–editing
To create a loadable computer program by means of a linkage editor.
link level
See frame level on page 2-96.
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 on page 2-237.
link trace
A sequential log of events that occur on the link. This log can help
determine the source of a recurring error.
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.
2-130
linker
See linkage editor on page 2-130.
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.
Glossary
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 on page 2-94.
list fields
See indexed fields on page 2-113.
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.
listening
Programs waiting for network communication on a given socket are
listening on that socket. See also socket on page 2-221 and port on page
2-179.
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 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 on
page 2-198.
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 on page
2-80 and big endian on page 2-20.
little endian order
The method of storage in which integer values are stored least significant
byte first. See also big endian order on page 2-20.
LLB
See Local Location Broker on page 2-132.
llbd
The local location broker daemon.
LLC
See logical link control on page 2-135.
LMS
Line monitoring system.
LNS
See LU network services component on page 2-138.
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 on page 2-29.
load level
The balance of work between processing units, channels, or devices.
load module
See run file on page 2-208.
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.
L
2-131
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 on
page 2-200.
(2) Pertaining to information that is defined and used only in one subdivision
of a computer program.
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.
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 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 on page
2-94.
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 iFOR/LS 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 on page
2-133 and Location Broker Client Agent on page 2-133.
2-132
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 on
page 2-166.
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.
local variable
A symbol defined in one program module or procedure that can only be
used within that program module or procedure.
Glossary
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
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 on
page 2-18, Local Location Broker on page 2-132, and Location Broker
Client Agent on page 2-133.
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 on page
2-132 and Location Broker on page 2-133.
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 on page 2-117.
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 on page 2-197.
LOCK
See Lock Service on page 2-133.
Lock button
In CDE, a Front Panel control used to lock the screen.
lock file
n multiprocess applications, a system file on disk that the sharing
processes use to control their access to shared data or devices.
Lock Service (LOCK)
The component of Encina Base that enables transactions to lock resources
before accessing or modifying them.
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 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.
L
2-133
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 on page 2-134.
log out
See log off on page 2-134.
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).
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 on page 2-259, logical
volume on page 2-136, and physical volume on page 2-175.
logarithm
A mathematical operation related to the base of a numbering system.
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 on page
2-33.
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
2-134
Glossary
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 on page 2-142.
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 on page 2-68.
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.
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.
logical partition (LP)
(1) One to three physical partitions (copies). The number of logical
partitions 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
on page 2-136.
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.
L
2-135
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 on page
2-172.
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 on page 2-134,
migration installation on page 2-145, logical partition on page 2-135, and
volume group on page 2-259.
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 on page 2-218.
long
(1) In ODM, a terminal descriptor type used to define a variable as a signed
4–byte number. See also terminal descriptor on page 2-239. (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 on page 2-136.
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.
2-136
Glossary
loop elimination
A form of loop unrolling in which the loop is completely unrolled, and
references to 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 on page 2-128.
LPFK
See lighted programmable function keyboard on page 2-129.
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.
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 on page 2-135.
LU1
See Logical Unit Type 1 on page 2-135.
LU2
See Logical Unit Type 2 on page 2-135.
LU3
See Logical Unit Type 3 on page 2-135.
L
2-137
LU6.2
See Logical Unit Type 6.2 on page 2-134.
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 Server, 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.
2-138
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 on page 2-136.
LVM
See Logical Volume Manager on page 2-136.
Glossary
M
m
See meter on page 2-144.
MAC
(1) See medium access control on page 2-142.
(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
on page 2-47 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 on page 2-263. See also computer language on page
2-47.
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 on page 2-207,
statement function on page 2-225, and subroutine on page 2-231.
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 on page 2-139 and macro on page 2-139.
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.
M
2-139
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 on page 2-230.
(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 on page 2-220.
(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 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 on page 2-216.
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 on page 2-145.
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.
2-140
Glossary
managed window
See managed children on page 2-140.
manager
See device manager on page 2-68.
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.
manual call
In data communications, a line type that requires the operator to place a
call over a switched line. Contrast with auto–call on page 2-15.
manual dialing In making an ATE connection, dialing the number manually over a
telephone line.
map
See mapping on page 2-141.
MAP
See maintenance analysis procedure on page 2-140.
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 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 on page 2-19.
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 on page 2-125 and profile on page 2-186.
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 on page 2-252. See also stub
on page 2-229.
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.
M
2-141
master
The only machine in the NIM environment that has permission to remotely
execute commands on other NIM clients.
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.
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 on page 2-42.
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 the operating system.
M–byte
See megabyte on page 2-142.
MC
See MCU on page 2-142.
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 on page 2-135.
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).
2-142
Glossary
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 on page 2-79.
(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 on page 2-227.
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 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 on page 2-168.
menu system
An interactive interface that lists related software options in a manner that
expedites review and selection by the user.
M
2-143
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
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.
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 on page
2-144.
(3) An object–oriented programming term synonymous with member
function.
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 on
page 2-144 and descriptor on page 2-67.
2-144
MHz
See megahertz on page 2-143.
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.
Glossary
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 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. See also root volume group on page 2-206
and logical volume on page 2-136.
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 on page 2-140.
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.
M
2-145
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 on page 2-169.
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
on page 2-88, screen coordinates on page 2-210, world coordinates on
page 2-265, and transformation on page 2-245.
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 on page
2-187, fix number on page 2-92, release number on page 2-199, and
version number on page 2-257.
modifier
2-146
Glossary
Word or quantifier used to change an instruction causing the execution of
an instruction 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.
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 on page 2-146.
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 on page 2-187.
(5) See also run file on page 2-208.
(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.
MOM
See monitor mode on page 2-147.
mond
See monitor scheduling daemon on page 2-147.
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 on page 2-72.
monitor mode (MOM)
A mode in which an application program can directly access the display
adapter.
monitor scheduling daemon
A process that runs on an application server and provides clients with links
to processing agents as needed
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 on page
2-103.
more–data bit See M–bit on page 2-142.
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.
M
2-147
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 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.
ms
A package of macros for manuscript and thesis preparation that features
automatic footnote numbering and bibliography capabilities.
msb
Most significant bit.
MSB
Most significant byte.
MS–DOS
Microsoft Disk Operating System.
msqid
See message queue ID on page 2-144.
MTU
See maximum transfer unit on page 2-142.
multibyte control
One of the two types of controls valid in a character stream data. Synonym
for escape sequence on page 2-83.
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.
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 on page 2-219.
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.
2-148
Glossary
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 on page 2-149.
multipoint
Pertaining to communication among more than two stations over a single
telecommunications line.
multipoint link A circuit that interconnects several stations.
multitasking
A mode of operation that provides for concurrent performance or
interleaved 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 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 on page 2-239.
M
2-149
N
n
See en on page 2-79.
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 on page 2-64 and prefix on page 2-182.
(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 on page 2-219.
name–lookup method resolution
Similar to the method resolution techniques employed by Objective–C and
Smalltalk.
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 on page 2-210.
NaN
See not–a–number on page 2-155.
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
2-150
Glossary
See Network Computing Architecture on page 2-151.
NCCF
See Network Communications Control Facility on page 2-152.
NCK
See Network Computing Kernel on page 2-152.
NCS
See Network Computing System on page 2-152.
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 iFOR/LS servers.
NDC
See normalized device coordinates on page 2-155.
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 on page 2-255.
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
(1) To incorporate a structure or structures into a structure of the same
kind.
(2) 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.
(3) A self–contained software element that completely 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 iFOR/LS on page 2-128.
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.
N
2-151
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.
network boot image
A boot image that supports standalone, diskless, and dataless machines.
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 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
Procedure Call runtime library and the Location Broker. NCS is the
underlying communications protocol used by iFOR/LS 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 iFOR/LS on page 2-128.
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 object An entry in the Network Installation Management (NIM) database that
represents a local area network.
network protocol
A communications protocol from the Network Layer of the OSI network
architecture, such as the Internet Protocol (IP).
2-152
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 on page 2-6.
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 on page 2-152.
NIC
See Network Information Center on page 2-152.
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 on page 2-7.
NIM
See Network Installation Management on page 2-152.
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 on page 2-153.
N
2-153
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 on page 2-17.
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 on page 2-63.
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, 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 on page 2-52.
2-154
Glossary
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 on page 2-68.
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
on page 2-218.
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.
normal attachment stop
See normal stop on page 2-155.
normal mode
See multiuser mode on page 2-149.
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.
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.
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 on page 2-245 and unit cube on page
2-251.
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.
N
2-155
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 on page 2-155.
NS
Network Systems. Also, Network Services.
NSA
Next station addressing.
NSI
Name Service Interface.
NTN
See national terminal number on page 2-150.
NTP
See Network Time Protocol on page 2-153.
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 on page 2-168 and SECAM on
page 2-212.
NTSC signal
A signal as defined by the National Television Standard Committee. Also
called composite video.
NTU
See network terminating unit on page 2-153.
NUA
See network user address on page 2-153.
NUI
See network user identification on page 2-153.
NUL
See null character on page 2-156.
NUL character In XPG4 system interface, a character with all bits set to zero.
null
Empty, having no value, containing nothing.
NULL
In the C language, a pointer guaranteed not to point to a data object.
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 on page 2-141.
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 character
See digit. on page 2-69
numeric constant
A constant that expresses an integer, real, or complex number.
2-156
Glossary
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 on page 2-34.
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 on page
2-246.
NVRAM
See nonvolatile random access memory on page 2-155.
N
2-157
O
O
Organization.
object
(1) In the Network Installation Management (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 on page 2-158.
(4) In Pascal, synonymous with data object on page 2-61.
(5) In GL, synonymous with display list on page 2-72. 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 on page 2-51
and variable on page 2-251.
(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 CDE, any logical piece of data that has associated 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 on
page 2-249.
object class
In ODM, a stored collection of objects with the same definition,
conceptually similar to an array of structures. See also object on page
2-158, terminal descriptor on page 2-239, and class on page 2-36.
Object Class Table (OCT)
A recurring attribute of the directory schema with the description of the
object classes permitted.
2-158
Glossary
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 on page 2-222.
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 on page 2-36.
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 instance
See instance on page 2-116 and object on page 2-158.
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 on page 2-147.
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 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).
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2-159
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) on page 2-251.
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 on page 2-262.
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 on page 2-262.
OCS
On–Card Sequencer.
OCT
See Object Class Table on page 2-158.
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.
2-160
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 on page 2-160.
octet string
See Object Data Manager on page 2-159.
ODM
See Object Data Manager on page 2-159.
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 on page 2-160.
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 on page 2-161.
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.
OM
See XOM on page 2-267.
on–hook
Deactivated, in regard to a telephone set. A telephone not in use is
”on–hook.” Contrast with off–hook on page 2-160.
Glossary
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–way channel
In X.25 communications, a logical channel that allows incoming calls only or
outgoing calls only. Contrast with two–way channel on page 2-248.
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 on page 2-248.
online
(1) Being controlled directly by or directly communicating with the
computer. Contrast with offline on page 2-160.
(2) Pertaining to the operation of a functional unit when under the direct
control of a computer.
op code
See operation code on page 2-162.
opaque
See opaque data type on page 2-161.
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 on
page 2-39.
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.
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2-161
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.
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 Common Desktop Environment, 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 on page 2-39, fast select on page 2-89, reverse
charging on page 2-204, and throughput–class negotiation on page 2-241.
2-162
Glossary
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.
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 on page
2-174.
OS
See operating system on page 2-161.
OS/2
Operating System/2.
OSF
Open Software Foundation.
OSI
See Open Systems Interconnection on page 2-161.
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.
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.
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2-163
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 on page 2-163.
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.
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.
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.
2-164
Glossary
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.
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2-165
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 on page 2-129, local pacing on page 2-132,
receive pacing on page 2-196, and remote pacing on page 2-200.
pacing response
In SNA Server, 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 on page 2-185.
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 on page 2-29,
call–connected packet on page 2-29, call–request packet on page 2-29,
clear–confirmation packet on page 2-37, clear–indication packet on page
2-37, clear–request packet on page 2-37, data packet on page 2-61,
incoming–call packet on page 2-112, interrupt packet on page 2-121,
interrupt–confirmation packet on page 2-120, reset–request packet on page
2-202, reset–confirmation packet on page 2-202, address field on page 2-6,
and restart–confirmation packet on page 2-204.
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.
2-166
Glossary
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 on page 2-127,
frame level on page 2-96, datalink level on page 2-61, and physical level on
page 2-175.
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 on page
2-96.
packet mode operation
Synonym for packet switching on page 2-167.
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 on
page 2-36.
packet window In X.25 communications, the number of packets that can be outstanding
without acknowledgment. See also frame window on page 2-96 and window
on page 2-263.
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.
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 on page 2-126.
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.
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2-167
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 on page 2-156 and SECAM on page
2-212.
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 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 on page 2-143.
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 on page 2-215.
parallel processing
The condition in which multiple tasks are being performed simultaneously
within the same activity. Contrast with serial processing on page 2-215.
2-168
Glossary
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 on page 2-94 and mode on page 2-146.
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 on page 2-108.
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 on page 2-20, Bezier cubic curve on page
2-20, and cardinal spline cubic curve on page 2-31.
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2-169
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 on page
2-35.
(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 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
on page 2-170.
parent folder
In CDE, a folder that contains subfolders and files. When discussing
command–line activities, this may be called the parent directory on page
2-170. See also subfolder on page 2-230.
parent ID
The character sequence identifying the graphical object that controls
smaller graphical objects, called children.
parent type
For Ada programming, see derived type on page 2-66.
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.
2-170
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.
parser
A program that interprets user input and determines what to do with the
input. See also grammar rules on page 2-102.
participant
An application is a participant in a transaction when it either initiates the
transaction or receives a request on behalf of that transaction.
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.
Glossary
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 on page 2-171.
pass–by–read/write–reference
Synonym for pass–by–VAR on page 2-171.
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
information is contained indefinitely in the routing tables and is included in
any routing information that is transmitted. Contrast with active gateway on
page 2-5.
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 on page 2-5. See also grab on page 2-102, button
grabbing on page 2-17, pointer grabbing on page 2-177, and key grabbing
on page 2-124.
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.
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patch
(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 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 on page 2-97 and relative path name on page 2-199.
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 on page 2-233.
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 on page 2-188.
PDN
See public data network on page 2-175.
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 on page 2-134.
2-172
Glossary
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 on page 2-175.
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 on
page 2-253 and user structure on page 2-254.
peripheral device
With respect to a particular processing unit, any equipment that can
communicate directly with that unit.
peripheral unit See peripheral device on page 2-173.
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 on page 2-218. See also
virtual circuit on page 2-258.
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 on page 2-3.
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 Common Desktop Environment, 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.
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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
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 on page 2-163.
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 on page 2-187.
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 on page
2-188.
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 on page 2-19.
physical data block
See block on page 2-19.
physical device
See device on page 2-67.
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 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 on page 2-175.
2-174
Glossary
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 on page 2-127, frame level on page 2-96, data–link level on page
2-61, packet level on page 2-167, and physical layer on page 2-174.
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 on
page 2-134.
picking
In computer graphics, a method for finding out what primitives are being
drawn near the cursor on the display screen. See also hit on page 2-108,
picking region on page 2-175, selecting on page 2-213, and selecting
region on page 2-213.
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 on page
2-108, selecting on page 2-213, picking on page 2-175, and selecting
region on page 2-213.
picture
A pixmap used for displaying Common Desktop Environment 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 on page
2-176.
PID
See process ID on page 2-186.
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 on page 2-188.
PIP
See Program Initialization Parameters on page 2-187.
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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 on page 2-176.
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 on page 2-176.
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 on page
2-14.
2-176
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 on
page 2-175.
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 on
page 2-176.
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 on page 2-176.
(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 on page 2-111.
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.
Glossary
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.
PMF
Parameter management frame.
PMP
See Preventive Maintenance Package on page 2-183.
PMR
See Problem Management Record on page 2-185.
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.
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 on page
2-102, button grabbing on page 2-17, and key grabbing on page 2-124.
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.
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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 contention, determine operational
status, or determine readiness to send or receive data.
polyline
In computer graphics, a sequence of adjoining lines.
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.
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.
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.
2-178
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.
Glossary
pop–up menu (1) Synonym for popup on page 2-178.
(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 on
page 2-178.
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 on page 2-179. See
also pop–up window on page 2-179.
POR
See power–on reset on page 2-181.
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 on page 2-221 and listening on
page 2-131.
portability
The characteristic that determines whether a source program can be
compiled and run on computers of different architectures without requiring
recoding.
portable character set
In the XPG4 system interface, the collection of characters present in all
locales supported by XSI–conformant systems: Or
ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz
0123456789!#%^&*()_+–={}[] :”~;’‘?,.|\/@$
Also included are the alert, backspace, tab, newline, vertical–tab, form–feed,
carriage–return, space characters, and the null character, NUL.
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2-179
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
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 on page 2-126.
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.
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.
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.
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.
POSIX
See Portable Operating System Interface For Computer Environments on
page 2-180.
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 on page 2-181.
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.
2-180
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.
Glossary
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.
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).
PPA (physical point of attachment)
The point at which a system attaches itself to a physical communications
medium.
PPA identifier An identifier of a particular physical medium over which communication
occurs.
P(R)
In X.25 communications, the packet receive sequence number.
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 on page 2-220 and double precision on page
2-75.
(2) The degree of discrimination with which a quantity is stated. For
example, a three–digit numeral discriminates among 1000 possibilities.
(3) In GL, 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 on page 2-67 and
Customized Database on page 2-29.
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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.
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.
preferential CUG
In X.25 communications, the default closed user group.
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 on page 2-150.
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 on page 2-66.
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 on page 2-6.
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.
2-182
Glossary
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
on page 2-183.
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 on page 2-183.
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.
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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 on page 2-88, screen
coordinates on page 2-210, and world coordinates on page 2-265.
primitive font
A font in which characters are defined as primitives. Like all other
primitives, primitive font characters can be scaled and rotated. See also
raster font on page 2-194 and font on page 2-94.
primitive space
Synonym for primitive coordinates on page 2-184.
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 on page 2-262.
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 1.3.3 (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.
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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.
privacy
A protection level that may be specified in secure RPC communications
and that encrypts RPC argument values.
Glossary
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 on page 2-166.
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 on page 2-185.
privileged state
A hardware protection state in which the processor can run privileged
instructions. Contrast with unprivileged state on page 2-252. See also
privileged instructions on page 2-185.
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 on page 2-218.
(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 on page 2-97.
(6) For Ada programming, see subprogram on page 2-230.
procedure address
The location of a particular program procedure in the AIXwindows Toolkit.
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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 on page 2-123.
process accounting
An analysis of how each process uses the processing unit, memory, and I/O
resources.
process attribute value
In Workload Management, process attribute values include user ID, group
ID, and application pathname.
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 on page 2-153.
process lock
Allows the calling process to lock or unlock both its text and data segments
into memory.
process pacing
See pacing on page 2-166.
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.
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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.
Glossary
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 on page 2-59 and mapping on page 2-141.
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 on page 2-117.
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 on page 2-92, modification number on page 2-141, release number
on page 2-199, version on page 2-256, background on page 2-17, and
version number on page 2-257
program stack Synonym for invocation stack on page 2-121.
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 on page 2-239.
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 on page 2-147. See also segment unit on page 2-213.
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programmable character set (PCS)
A geometric text font. Synonymous with stroke text. See also geometric text
on page 2-100.
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 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
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Glossary
(1) In SNA and SNA Server, 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 on page 2-221.
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.
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 on page
2-57.
P(S)
In X.25 communications, the packet send sequence number.
PSAP
See Presentation Service Access Point on page 2-182.
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, 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.
PSN
See public switched network on page 2-175.
PSTN
See public switched telephone network on page 2-190.
PTF
See program temporary fix on page 2-187.
PTN
See public telephone network on page 2-190.
PTT
Post, Telegraph, and Telephone authority.
PTY
See pseudo terminal on page 2-189.
PU
See physical unit on page 2-175.
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.
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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.
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
2-190
Glossary
Program update tape.
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 on page 2-173.
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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 on page 2-192.
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.
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.
qualified type name
Used to reduce complex class name syntax by using typedefs to represent
qualified class names.
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.
qualifier bit
See Q–bit on page 2-192.
quality of service negotiation
An optional CCITT–specified facility.
2-192
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 on page 2-228.
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.
Glossary
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.
queued I/O devices
Devices (keyboard, mouse, button, dials) whose changes are recorded in
the event queue.
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.
quit
A key, command, or action that tells the system to return to a previous state
or stop a process.
quote
To mask the special meaning of certain characters, causing the characters
to be taken literally.
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 on page 2-16.
Q
2-193
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 alongside, 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 on page 2-84.
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 individual key value for which all matching records should
be selected in a nonunique index.
2-194
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 on page 2-95.
raster font
A font in which the characters are defined directly by the raster bit map.
See also font on page 2-94 and primitive font on page 2-184.
Glossary
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 on page 2-195.
RC
Routing control.
RCM
(1) See real–time control microcode on page 2-196.
(2) Rendering Context Manager.
RCS
See Revision Control System on page 2-205.
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.
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
on page 2-258.
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.
R
2-195
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 on page 2-133.
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 on page 2-214. See also pacing on page 2-166.
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 on page 2-266.
record
2-196
Glossary
(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 on page 2-37, widget record on page 2-262, and
instance record on page 2-116.
record lock
A lock that prevents some or all of a file from being written to or read. See
also lock on page 2-133.
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.
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 on page 2-225.
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.
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 on
page 2-240, and thread–synchronous service on page 2-240.
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2-197
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 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 on page 2-99.
(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 on page 2-131.
See also collating element on page 2-40 and subpattern on page 2-230.
reject.
2-198
Glossary
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 on page 2-10 and commit on page 2-43.
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 on page 2-172 and full path name on page 2-97.
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 on page 2-92, modification number on
page 2-141, version number on page 2-257, program level on page 2-187
and version on page 2-256.
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2-199
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.
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 on page 2-132.
remote access data processing
Synonym for teleprocessing on page 2-238.
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 on page 2-166.
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.
2-200
Glossary
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
(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
on page 2-43.
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.
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.
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2-201
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 on page 2-202.
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 on page 2-32.
reset collision See collision on page 2-40.
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 on page 2-166.
reset diagnostic
See diagnostic code on page 2-68.
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 on page 2-166.
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.
2-202
Glossary
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 limitation values
A set of values that Workload Management attempts to maintain for a set of
resource utilization values. The resource limitation values are independent
of the resource limits specified with setrlimit().
resource manager
A component that manages application data. Resource managers
communicate with application servers.
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 on page 2-203.
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 target share
The shares of a resource that should be available to a Workload
Management class. These shares are used with other class shares to
determine the desired distribution of the resources between classes.
resource utilization value
The amount of a resource that a process is currently using in a system. See
also scope of resource collection on page 2-210.
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 on page
2-14.
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2-203
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 on page 2-166.
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.
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 on page 2-204.
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 on page 2-162.
reverse video
2-204
Glossary
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 on page 2-222.
revision text
See version identifier on page 2-257.
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 on page 2-194.
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 on page 2-41.
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 on page 2-203.
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 on page 2-205.
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 on
page 2-205.
RIP
See Routing Information Protocol on page 2-207.
RISC
See Reduced Instruction Set Computer on page 2-197.
RJE
See remote job entry on page 2-200.
RMT
Ring management.
R
2-205
RNR frame
In X.25 communications, a receive–not–ready frame. Contrast with RR
frame on page 2-195.
RNR packet
In X.25 communications, a receive–not–ready packet. Contrast with RR
packet on page 2-195.
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 on page 2-3.
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 on page 2-11.
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 on page 2-262.
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.
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 on page 2-206.
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 on page 2-206.
root volume group (rootvg)
A volume group containing the Base Operating System (BOS). See also
migration installation on page 2-145.
2-206
Glossary
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 on page 2-245.
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 on page 2-139
and subroutine on page 2-231.
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.
row–major order
A way of storing array elements such that the rightmost subscript varies
most rapidly as memory–adjacent elements are accessed.
RPC
See remote procedure call on page 2-200.
rpm
Revolutions per minute.
RPN
See real page number on page 2-195.
RPOA
See recognized private operating agency on page 2-196.
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
on page 2-206.
RR packet
n 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 on page 2-206.
RS–232C
See EIA–232D on page 2-78.
RS–422A
See EIA–422A on page 2-79.
R
2-207
RSi
See Remote Statistics Interface on page 2-200.
RTI
Response type indicator.
RTPN
See remote transaction program name on page 2-200.
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
Common Desktop Environment.
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 on page
2-147.
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.
2-208
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
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 on page 2-217
SAK
See secure attention key on page 2-212.
sample rate
Synonym for locator sample rate on page 2-133.
SAP
See service access point on page 2-215.
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 on page 2-51 and subtype on page
2-231.
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.
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.
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 on page 2-229. 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.
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.
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2-209
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.
scanline order An image represented by scanlines ordered by increasing the y coordinate.
scanned image
An image that is examined sequentially, part by part.
scatter
For input and output operations, to read data from a device and locate it in
noncontiguous memory addresses. Contrast with gather on page 2-99.
SCCS
See Source Code Control System on page 2-222 and Revision Control
System on page 2-205.
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 on page 2-64.
scope of resource collection
In Workload Management, the scope of resource collection specified for a
class determines how resource limits are applied to the processes in that
class. The scope levels can be set to class, process, user, or group.
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 on page 2-72.
(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.
2-210
Glossary
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 on page 2-88, primitive coordinates on page 2-184, modeling
coordinates on page 2-146, world coordinates on page 2-265, and
transformation on page 2-245.
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 on page 2-210.
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 on page 2-38.
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 on page 2-211.
scrolled text
Text that is scrolled. See also scroll on page 2-211.
scrolling
The horizontal or vertical movement of graphic or text information
presented on a display screen.
SCSI Adapter
See Small Computer Systems Interface Adapter on page 2-220.
sdb
See symbolic debugger on page 2-233.
SDLC
See synchronous data link control on page 2-219.
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 on page 2-226.
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.
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2-211
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 on page 2-156 and PAL
on page 2-168.
second–level interrupt handler (SLIH)
A device–dependent routine that handles the 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.
2-212
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.
Glossary
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 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 on page 2-187.
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 on page 2-108, selecting
region on page 2-213, picking on page 2-175, and picking region on page
2-175.
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 on page 2-108, selecting on page 2-213,
picking on page 2-175, transformation on page 2-245, and picking region on
page 2-175.
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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 on page 2-6.
(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 on page 2-124.
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 on page 2-213.
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 on page 2-219.
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 on page 2-214.
send pacing
In SNA, the pacing of message units that a component is sending. Contrast
with receive pacing on page 2-196.
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.
2-214
Glossary
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 on page 2-168.
serial port
A port used for a serial device. See also serial device on page 2-215.
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 on page 2-168.
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.
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.
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 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.
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2-215
service mode
Synonym for maintenance mode on page 2-140.
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 Server.
(2) A transaction program implemented by a transaction processing system.
Service transaction programs perform such functions as providing access to
remote data bases and remote queues. See also application transaction
program on page 2-10 and transaction program on page 2-244.
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 on page 2-140.
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 on page 2-56
and system date on page 2-220.
session key
Used in Kerberos specifications. See also conversation key on page 2-54.
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 1.3.3, a profile describing
the characteristics of a session between a client system and a System/370
host computer. See also 3270 Host Connection Program on page 1-1 and
profile on page 2-186.
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.
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.
2-216
Glossary
set
In NCS, to associate an allocated Remote Procedure Call (RPC) handle
with a specific socket address. See also bind on page 2-18.
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 on page 2-28.
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 on page 2-217.
setuid
See set–user–ID mode bit on page 2-217.
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.
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.
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 on
page 2-84.
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 on page 2-90.
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.
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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 on page 2-218 and command interpreter on page
2-42. Synonymous with interface on page 2-119.
(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 on page 2-218.
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.
shell command names
Operating–system commands.
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.
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.
shell prompt
The character string on the command line indicating that the system can
accept a command (typically the $ character).
shell script
Synonym for shell procedure on page 2-218.
shell variables Facilities of the shell program for assigning variable values to constant
names.
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 on page 2-218. See also widget on page 2-262.
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 on page 2-217.
short
In ODM, a terminal descriptor type used to define a variable as a signed
2–byte number. See also terminal descriptor on page 2-239.
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.
2-218
Glossary
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 on page 2-91. See also discipline on
page 2-71.
sibling
Children of the same parent window.
SiCounter
In Performance Toolbox, a value that is incremented continuously.
Instruments show the delta (change) in the value between observations,
divided by the elapsed time, representing a rate per second.
SID
SCCS identification. The name assigned to a delta.
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.
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
on page 2-84 and interrupt on page 2-120.
signal handler A subroutine called when a signal occurs.
signal mask
Defines the set of signals currently blocked from delivery to a process.
signal stack
An alternate stack on which signals are to be processed.
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 on page 2-64 and name on page
2-150.
simultaneous peripheral operation online
See spooling on page 2-223.
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 on page 2-74.
single–byte control codes
ASCII codes 0 through 31 (0x00 through 0x1f) and delete (0x7f).
single–mode optical fiber
An optical fiber in which only the lowest–order bound mode (which can
consist of a pair of orthogonally polarized fields) can propagate at the
wavelength of interest. Contrast with multimode optical fiber on page 2-148.
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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 on page 2-167.
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 on page 2-251.
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.
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 on page 2-218.
SJN
See shortest–job–next on page 2-219.
skew
The time difference between two clocks or clock values.
SLA
Serial Link Adapter. See also SOCC on page 2-221.
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 on page 2-212.
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 on page 2-31.
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.
2-220
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 on page 2-20.
SMIT
System Management Interface Tool.
SMP
See symmetrical multiprocessor system on page 2-233.
Glossary
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 on page 2-219.
SNA
See System Network Architecture on page 2-221.
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 on page 2-218.
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 on page 2-150.
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 on page 2-221,
port on page 2-179, and listening on page 2-131.
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 on page 2-189.
software
Programs, procedures, rules, and any associated documentation pertaining
to the operation of a system. Contrast with hardware on page 2-105.
software configuration
The processing required to make installed software ready to use.
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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.
Software Vital Product Data (SWVPD)
Information that uniquely defines system, hardware, software, and
microcode elements of a processing system.
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 on page 2-237.
(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 on page 2-159.
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 on page 2-205.
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 on page 2-222.
source program
A computer program expressed in a source language.
source statement
A statement written in a programming language.
2-222
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 spaces for future addition of data. See also hole in a file on page
2-108.
Glossary
SPC
See System Program Controller on page 2-235.
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 on page 2-70 and file on page 2-90. See
also block file on page 2-20 and character special file on page 2-34.
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 on page 2-129.
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 on page 2-235.
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 on page 2-217.
SPP
Sequence packet protocol. The primary transport–layer protocol in the
Xerox Network Systems. It provides reliable, flow–controlled, 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 on page 2-216.
SRT
See Structure Rule Table on page 2-228.
SSCP
See system services control point on page 2-221.
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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.
standalone system
See standalone workstation on page 2-224.
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.
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Glossary
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 on page 2-13.
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.
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 on page 2-197.
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
on page 2-20. 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 on
page 2-139.
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 on page 2-126.
statement number
See statement label on page 2-225.
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.
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2-225
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 on page 2-93.
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 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 on page 2-15.
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 on page 2-52.
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 on page 2-224.
STDIN
See standard input on page 2-224.
STDOUT
See standard output on page 2-224.
steal (a page frame)
The act (by the Virtual Memory Manager) of reallocating a real–memory
page frame that contains a virtual–memory page that is being used by a
currently executing program.
sticky bit
2-226
Glossary
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 on page 2-143.
(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 on page 2-62.
(4) 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.
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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 on page 2-228.
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 on page 2-242.
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 on page 2-188 and geometric
text on page 2-100.
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
2-228
Glossary
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 on page 2-89.
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 on page 2-209.
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 on page 2-141.
(2) Hooking functions used as extensions to the protocol to generate
protocol requests for Enhanced X–Windows. Synonym for hooking routines
on page 2-108.
(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.
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 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
A class of widgets that inherits resources from a higher class.
subcommand A request for an operation that is within the scope of work requested by a
previously issued command.
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2-229
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 on page 2-170). 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 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.
2-230
subnetwork
Synonym for subnet on page 2-230.
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 on page 2-198.
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
on page 2-140.
(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 on page 2-97 and procedure on page 2-185.
Glossary
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 on page
2-18.
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 on page
2-207.
(3) A request by an active process for a service by the system kernel. See
also macro on page 2-139.
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.
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.
subscript declarator
In an array definition or declaration, the bracketed expressions following the
array name. Specifies the number of elements in an array dimension.
subscript quantity
In FORTRAN, a component of a subscript. A subscript quantity is an integer
or real constant, variable, or expression.
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 on page 2-18.
subwidget
In AIXwindows and Enhanced X–Windows, a widget class directly beneath
a higher widget class in a widget–gadget hierarchy.
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2-231
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 (.).
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 on page 2-111.
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 on page 2-262.
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.
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 on page 2-206.
superuser authority
See root user authority on page 2-206.
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 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.
2-232
SVC
See switched virtual circuit on page 2-218 and Supervisor call on page
2-232.
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.
Glossary
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.
swidge
See shadow widget on page 2-217.
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
n data communications, a connection between computers or devices
established by dialing. Contrast with nonswitched line on page 2-155.
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 on page 2-173. See also virtual circuit on page 2-258.
SWVPD
See Software Vital Product Data on page 2-222.
symbol table
See parse on page 2-170.
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
on page 2-172.
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.
symbolic name
A unique name used to represent an entity such as a file or a data item.
See also name on page 2-150.
symmetrical multiprocessor (SMP) system
A system containing multiple processors that are essentially identical and
perform identical functions.
SYN
See synchronization character on page 2-219.
synchronization character (SYN)
In binary synchronous communications, the transmission control character
that provides a signal to the receiving station for timing.
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.
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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 on page 2-17.
(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 on page 2-13.
(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:
~ 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.
~ 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
on page 2-214.
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 on page 2-6 and user address list on page 2-253.
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 on page 2-51.
2-234
Glossary
system customization
Specifying the devices, programs, and users for a particular data
processing system. Contrast with configuration on page 2-48. See also
customization on page 2-58.
system date
The date assigned by the system user during setup and maintained by the
system. See creation date on page 2-56 and session date on page 2-216.
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 on page 2-140, 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 parameters
Synonym for kernel parameters on page 2-124.
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.
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).
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2-235
system prompt Synonym for command line on page 2-42. 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 on page 2-114.
system ROS
The piece of system microcode that is responsible for loading a boot
image.
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 on page 2-114.
2-236
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.
Glossary
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 on page 2-255.
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.
tape drive
A mechanism for moving magnetic tape and controlling its movement.
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 on page 2-222.
(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 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 program Synonym for object program on page 2-159.
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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 on page 2-149.
tbl
A preprocessor that formats tables for the nroff and troff commands.
TCB
See trusted computing base on page 2-247.
TCP
See Transmission Control Protocol on page 2-246.
TCP/IP
See Transmission Control Protocol/Internet Protocol on page 2-246.
TCW
Translation control word.
TD
Transmit Data used with EIA–232 Protocol.
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.
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.
2-238
Glossary
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 on page 2-265.
(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.
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 on page 2-218, long on page 2-136, binary on page 2-17, char on
page 2-33, descriptor on page 2-67, vchar on page 2-256, and object class
on page 2-158.
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 on page 2-72.
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 on
page 2-187.
(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.
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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 on page 2-42 and last line mode on
page 2-126.
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 on page 2-263.
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 on page 2-247.
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 on page
2-197.
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 on page 2-197.
threaded application
An application that performs its function by simultaneously using multiple
execution paths (threads of control) within a single address space.
2-240
Glossary
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 on page 2-162.
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 on page 2-237.
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.
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.
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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 on page 2-245.
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 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 on page 2-228.
(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.
2-242
Glossary
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.
TPN
See transaction program name on page 2-244.
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.
T
2-243
transaction
(1) An exchange between a workstation and a program, two workstations,
or two programs that accomplish a particular action or 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.
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.
transaction ID See transaction identifier on page 2-244.
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 on page 2-54,
application transaction program on page 2-10, and service transaction program on page
2-216.
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.
2-244
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.
Glossary
transformation (1) 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 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 on
page 2-155, modeling coordinates on page 2-146, rotation on page 2-207,
eye coordinates on page 2-88, screen coordinates on page 2-210, selecting
region on page 2-213, viewing matrix on page 2-257, world coordinates on
page 2-265, clipping on page 2-38, and current transformation matrix on
page 2-42.
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 on page 2-245.
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 on page 2-245.
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.
T
2-245
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 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).
2-246
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
on page 2-84.
Trash Can
In CDE, a container for deleted files or folders.
traversal
See keyboard traversal on page 2-125.
Glossary
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 on page 2-157.
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 on page 2-93.
(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 on page 2-247.
T
2-247
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 on page 2-246.
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 on page 2-248.
tuning
See hand tuning on page 2-105.
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 on page 1-1.
two–way channel
In X.25 communications, a logical channel that allows both incoming and
outgoing calls. Contrast with one–way channel on page 2-161.
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 on page
2-161.
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 on page 2-62.
(3) In NCS, a class of object. All objects of a 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 on page 2-44.
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.
type identifier The name given to a declared type. See also type specifier on page 2-249.
2-248
Glossary
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 on page 2-248.
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 on page 2-158 and Universal Unique
Identifier UUID on page 2-251.
typematic key A key that, when held down, repeats its function multiple times.
T
2-249
U
UA
See unnumbered acknowledge on page 2-252.
UART
See Universal Asynchronous Receive/Transmit on page 2-251.
ublock
See user block on page 2-253.
UCT
See Universal Coordinated Time on page 2-251.
UDP
See User Datagram Protocol on page 2-253.
UDP/IP
User Datagram Protocol/Internet Protocol.
UFS
See UNIX File System on page 2-251.
UI
See unnumbered information frame on page 2-252.
UID
See user number on page 2-254 and AIXwindows User Interface Definition
on page 2-7.
UIL
See AIXwindows User Interface Language on page 2-7.
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 on page 2-20.
unblocked
In an Enterprise Systems Connection Director, the attribute that, when set,
establishes communications capability for a specific port. Contrast with
block on page 2-19.
unconditional branch
A branch that is taken every time it is encountered.
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.
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.
(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.
2-250
Glossary
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 on page 2-83.
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 on page 2-220.
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 on page 2-44.
(3) For Ada programming, synonym for compilation unit on page 2-45.
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 on page 2-155.
unit identifier
In FORTRAN, the number that specifies an external unit or internal file. The
number can be one of the following: an integer expression whose value
must be zero or positive, an * (asterisk) that corresponds to unit 5 for input
or unit 6 for output, or the name of a character array, character array
element, or character substring for an internal file.
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
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 on page
2-160 and type UUID on page 2-249.
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.
U
2-251
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 on page 2-19.
(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 on page 2-141.
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 on page
2-111.
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 on page 2-185.
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.
2-252
Glossary
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.
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 on page 2-4.
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 on page 2-6 and system address
list on page 2-234.
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 on page 2-173.
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 on page 2-254.
U
2-253
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 on page 2-254.
(2) A parameter that specifies the user ID under which the application or
transaction program runs. Contrast with user name on page 2-254.
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 on page 2-124.
user name
A string of characters that uniquely identifies a user to the system. Contrast
with user identification on page 2-254.
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) on
page 2-254.
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 on page 2-254.
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 on page 2-173 and user
block on page 2-253.
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 on page 2-251.
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 on page 2-253.
UUCP
See UNIX–to–UNIX Copy Program on page 2-252.
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 on page 2-19.
UUID
2-254
Glossary
See Universal Unique Identifier on page 2-251.
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 or the network 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 on page 2-151.
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 on page 2-69.
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 on page
2-14.
variable
(1) A name used to represent a data item whose value can change while
the program is running. Contrast with constant on page 2-51.
(2) In programming languages, a language object that can take different
values at different times.
(3) A quantity that can assume any of a given set of values.
(4) For Ada programming, see object on page 2-158.
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 on page 2-237.
VC
See virtual circuit on page 2-258.
V
2-255
vchar
In ODM, a terminal descriptor type used to define a variable as a
variable–length, null–terminated string. See also terminal descriptor on
page 2-239.
VCI
Virtual channel identifier in an ATM network.
VDD
See virtual device driver on page 2-257.
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 on page 2-92, program level on page 2-187, modification number
on page 2-141, release number on page 2-199, and version number on
page 2-257.
version control
The process by which the contents of each revision of software, hardware,
or documentation are accounted for.
2-256
Glossary
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 on page 2-92, modification
number on page 2-141, release number on page 2-199, version on page
2-256 and program level on page 2-187.
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.
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 on page 2-88.
viewing coordinates
Synonym for eye coordinates on page 2-88.
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 on
page 2-89, transformation on page 2-245, and world coordinates on page
2-265.
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.
V
2-257
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 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 on page 2-218 and permanent virtual circuit on page 2-173.
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 on page 2-68.
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 on page 2-195.
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 on page 2-258.
Virtual Storage Extended (VSE)
An operating system that is an extension of DOS. A VSE system consists of
licensed VSE/Advanced Functions 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.
2-258
Glossary
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 on page 2-166.
VLSI
Very large scale integration.
VLSI circuit
Very large scale integrated circuit.
VLT
See video lookup table on page 2-257.
VM
Virtual machine.
VM/CMS
A type of operating system used on a System/370 computer.
VMTP
See Versatile Message Transaction Protocol on page 2-256.
VOL
See Volume Service on page 2-260.
Vol ID
See Volume ID on page 2-260.
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 on
page 2-134.
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 on page 2-136.
V
2-259
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 label
An area on tape or disk that is used to identify the tape volume and its
owner.
Volume Service (VOL)
The component of Encina Base that addresses storage.
2-260
VPD
See Software Vital Product Data (SWVPD) on page 2-222.
VPI
Virtual path identifier in an ATM network.
VRAM
Video random–access memory.
VSE
See Virtual Storage Extended on page 2-258.
VSE/ESA
ee Virtual Storage Extended/Enterprise Systems Architecture on page
2-259.
VSE/SP
See Virtual Storage Extended/System Product on page 2-259.
VTAM
See Virtual Telecommunication Access Method on page 2-259.
VTL
Vendor Technology Logic
Glossary
W
WAN
See wide area network on page 2-261.
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 on page 2-261.
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 the operating system.
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 commands.
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.
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).
white space
Space characters, tab characters, and new–line characters.
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; therefore, it is capable of transmitting data at high speeds.
Synonym for broadband channel on page 2-20.
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.
W
2-261
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
on page 2-46, core widget on page 2-39, primitive widget on page 2-184,
and shell widget on page 2-218.
(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 on page 2-36.
widget gravity Synonym for window gravity on page 2-263.
widget hierarchy
Synonymous with widget tree on page 2-262.
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 on page 2-116.
widget menu
A menu that allows the user to perform any number of actions, such as
cutting, copying, and pasting, to selected widgets.
widget programmer
A programmer who adds new widgets to the Enhanced X-Windows (or
other) Toolkit.
widget record A collection of related data objects, such as variables and parameters,
associated with any given widget. See also instance record on page 2-116,
record on page 2-196, class record on page 2-37, and superclass on page
2-232.
widget tree
(1) The symbolic structure for Enhanced X-Windows Toolkit code. The
basic element is a widget class. See also leaves on page 2-127,
intermediate nodes on page 2-119, and root on page 2-206.
(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 on page 2-262.
widget visibility
Contrast with obscure on page 2-160 and occlude on page 2-160.
wildcard
2-262
Glossary
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 on page 2-38 and
current window on page 2-42
(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 on page 2-96 and packet
window on page 2-167.
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 on page 2-103.
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 Common Desktop Environment, 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 on page 2-149.
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 on page 2-45.
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 on page 2-105.
(2) A character string considered as a unit for a given purpose.
W
2-263
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 on page 2-57.
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 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.
workload concurrency
The degree to which the system approaches the ideal of always having as
many dispatchable threads as there are processors.
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.
2-264
Glossary
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 on page 2-239.
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 space to
screen space. Synonymous with world space. See also modeling
coordinates on page 2-146, eye coordinates on page 2-88, primitive
coordinates on page 2-184, screen coordinates on page 2-210, viewing
matrxi on page 2-257, and transformation on page 2-245.
world space
Synonym for world coordinates on page 2-265.
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 on
page 2-28.
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.
W
2-265
X
X Atom
An Enhanced X-Windows atom. See also atom on page 2-13.
X resource
In AIXwindows, synonymous with resource on page 2-203.
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.
2-266
X Server
See server on page 2-215.
X Toolkit
See AIXwindows Toolkit on page 2-7.
X–Windows
A network–transparent windowing system developed by MIT. It is the basis
for Enhanced X–Windows. See also X11 client on page 2-266.
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 on page 2-266.
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.
X.21 bis
A CCITT recommendation, defining the use on public data networks of
DTEs designed for interface to synchronous V series modems.
X.25
The 25th CCITT recommendation in the X series, defining the interface
between data terminal equipment and packet switching data networks.
X.25 adapter
Synonym for X.25 Interface Co-Processor/2 on page 0.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 on page 2-44.
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 on page
2-266 and data link on page 2-61.
X.25 network
A service providing packet–switched data transmission that conforms to
Recommendation X.25 adopted by the CCITT.
X.25 port
A device in the /dev directory that corresponds to an X.25 link. See also
X.25 link on page 2-266.
X.28
The CCITT recommendation that specifies the user interface between an
asynchronous (start/stop) device and a packet assembler/disassembler
(PAD).
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 on page 2-86.
xcomms
The command that provides a menu panel for other X.25 commands (the
xmanage, xroute, and xtalk commands).
Glossary
XDR
See External Data Representation on page 2-87.
XDS
The X/Open Directory Service.
XGSL
See Graphics Support Library on page 2-103.
XID
See exchange identification on page 2-84.
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.
Xlib
In Enhanced X–Windows, a C language subroutine library that client
programs use to interface with the windowing system.
Xlib call
See Xlib on page 2-267.
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 similar to the
TCP/IP suite. However, different packet formats and terminology are used.
XOM
X/Open Object Management.
xroute
The command that enables system managers to manage the X.25 routing
list
Xt intrinsics
See intrinsics on page 2-121.
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.
XTI
X/Open Transport Interface. A library implementation, as specified by
X/OPEN CAE 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.
XTISO
XTI over SOckets.
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 on page 2-269.
X
2-267
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
2-268
Glossary
To copy a word or line of text into memory.
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 on page 2-107.
Z format
The format of a pixmap organized as a set of pixel values in scanline order.
See also XY format on page 2-267.
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.
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.
Z
2-269
2-270
Glossary
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