INTERDATA Operating System Disc DOS Reference Manual

DISC
Operating System
(DOS)
Reference Manual
€
EIN"TIERID ATA
DISC
Operating System
(DOS)
Reference Manual
Publication Number 29-293R01
INFORMATION CONTAINED IN THIS
MANUAL IS SUBJECT TO DESIGN
CHANGE OR PRODUCT IMPROVEMENT
© INTERDATA INC., 1972
All Rights Reserved
PRINTED IN US A.® JULY 1973
CHAPTER 1
CHAPTER 2
CHAPTER 3
DISC OPERATING SYSTEM
REFERENCE MANUAL
TABLE OF CONTENTS
SYSTEM CONCEPTS 2.020 1 0 00 0 0 0 0 0 0 0 0 0 0 00 a 0 0 0 0 0 00 a 00
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1,4
INTRODUCTION ... 6.200000 000 000 00 000000 0000 00000
FEATURES .....+. 466 01 a 6 6 8 40 00 0 00 8 1 8 0 6 00 0 000000 9
ELEMENTS OF THE SYSTEM a & +6 + + # $ #6 2 + A т &
1.3.1
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Executive ...omcoccooooacoooooaro oe ooo ooo
SUpervisOr...oreoroeoooooooooronao ne raoo ooo
Loader ..P.oscrcocserooooooreooroosooo o roo
Device Drivers. ......+.+..+.+00 0000 800 80000
User Programs 000000000000. 0.0.0.0. 0. 0. 0. 0 0.0.0. 0 0. 0®
Other Programs .......+.+.+. 0000000000 00000000
DOS Directory ................<ews0 0000006
Memory ..oosreroosocoroaooaosre oo or aooo roo «oo
M CONFIGURATION... | JA à #2
Hardware Configuration ......................
Disc Allocation....coo2oeooeocororecoroooeo roo
Security and Protection ....oososooscsorcocooaco ooo
Relationship to other Operating Systems. ..........
DOS OPERATIONS + E & à #% A #6 #6 E # # # & ss # + + 6 + +» 6 #v #6 #6 + 6 + 5 + 46 à » + & 5 à
2.
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2
2.3
2.4
INTRODUCTION . . +. +. 4.6 4 1 0080 60 0 6 1860600 00 0 000000
LOADING AND STARTING THE SYSTEM ....orecocoreoroo
2.2.1
2,2,2
Re-Starting at SYSGO “....................
Loading from Bulk Storage Devices .............
PROGRAM INTERRUPTS AND ERRORS ....ooosccacocorsoeco
2.3.1
3
RA
‚1 Commands for Mass Storage Devices
2
3
4
5
1/0 Device Errors 0000000000000. 00080080000
Privileged or Illegal Instruction ........0 e000
Arithmetic Fault Interrupts «ov ooo ev cv oo eo oo ess
TOR COMMAND PROCESSOR . ...Qo ocseaooaorodacoreo
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General Commands....oosocoscoososooorsooecoroca
1/0 Control Commands ,.,...0oeoowoocsosoerocerrrcorco
Summary of DOS Operator Commands ,...Q.eoeovosoo
Summary of DOS System Messages «oo cv evo v0 eee oo
APPLICATION PROGRAMMING 200000000000 00002 000.00. 000 005
3,1
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PROGRAMMING CONVENTIONS 000000000000 000000000000
3.1.1
Privileged Instructions „...0.00000 0000 00 00. 00.000
SUPERVISOR CALL + + & #6 6 +4 #6 46 4 46 # + PP OF PS PD BP SO PP + + +
INPUT/OUTPUT PROGRAMMING ....oerooococooooooraoro
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Examples of Data Transfers ....coooocoooooreooo
Teletype Input/Output ......eororecooreorcesocaoo
High Speed Paper Tape Reader Input . 0.0.00... 200
High Speed Paper Tape Punch Output .............
Card Reader Input. ....ceewoorocosorerecoornoocoo
Line Printer Output. 00.0.0000 000000 000.00. 0.00 2.08
Magnetic Tape Input/Output ......_oeococoocrocoo
Cassette Tape Input/Output. . . cc cv ve et ve veo vas
Disc Input/Output + oo oo vv veo sss nove oonoesos
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TABLE OF CONTENTS
(Continued)
3.3.10 Control Operations 2.0.0.0.00.00 000000000. 0.0.2000. 0.9 0.0.0.0. 0.0. 0.0.0800 3-11
3,4 SVC 2 - SERVICE FUNCTIONS (see Figure 3-3). 0000000000 000080. 0.0.2 000 3-13
3.5 SVC 3 - ENDOF JOB ...ooecoocoscorvororoaoareorocaoaco oo oro nao, 3-18
3.6 SVC 4 - EXECUTE COMMAND STATEMENT. ...osrocoreodcoocooooosgo0co 3-19
3.7 SVC 5- FETCHOVERLAY, ..Ñ.oococesococoroooraooaroaoooorara sr oo e reads 3-20
3.8 SVC 6 - CALLA PROGRAM...Q.ooescsconccsroocoro»rsoooaocoeooorocooroo 32/3-22
CHAPTER 4 SYSTEM USAGE ......+.0 60600000 0080004080 8 328 006 0 0 000 000008 4-1
4.1 INTRODUCTION 20000000000. 0.0.00. 0 0.0.0.0.0.0.0.0.2.0.0. 0.0.0.0. 0.0.0.0. 0.0.0. 0.0 8.0.08
4,2 MEMORY USAGE AND REQUIREMENTS 2000000000000 00 0.0.0 00.0. 0.0.0.2. 08
4,3 SYSTEM USAGE EXAMPLES 0000000000000 0000.08 2.4.0.0. 0.0.0 0.0. 0.0 0. 8.0 00
4.3.1 Establishing a Program on Disc ..eocoeoresocaryosrocooror esos
4. 3. 2 Assemblies with Disc Scratch. ...Ñ.ooeoseovoronroororeosaoseocooo
4.3.3 FORTRAN Compile and GO 2.000000 0000080000. 000.00. 0.0008
4.3.4 Cataloging and Batch Operations ......00000 000.00 000.2 000% 008
DISC FILE USE 0000000000 00000080008 0.0.0.0. 0. 0.000. 0.8.8.0. 0.08. 08.0.0. 8 000
PERFORMANCE TIMES .......00 000000008000 00600008 0000 10000 4-7 /4-8
4.6.1 Sequential Disc File Timing Chart . . . . . «cv vv vv ttt tev oe vv ena 4-7/4-8
4.6.2 Useful Time Estimates (Model 70). ........... Cee eee eee 4-7/4-8
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CHAPTER 5 DOS SYSTEM GENERATION AND MODIFICATION 00000000002 000000 2000 20.008 5-1
5.1 SYSTEM GENERATION 0000000000000 000.00. 0.00.00. 000.0.0.0.00 000.2 000
5.1.1 Introduction . 0004000000 0000. 0.600.009 008.000. 00.0.0080. 00088
5.1.2 Conditional Assembly Procedure using the Teletype
to Input SYSGEN StatementS 2....00.0000 0000 0.000.002. 0.0.0.0. 0 000 5-1
5.1.3 Conditional Assembly using Tape or Cards
to Input SYSGEN Statements ,..ooooosooscsoasodooodoaroo orero 5-3
5.1.4 Assembly Procedures to Add New Drivers ....eserecoaorosocnreo. 5-3
5.1.5 Sample DOS System Generation...._ecececooooscoreorrocsoosreroo 5-4
5.1.6 Adding User Written Drivers 0.0.0..0.0.0000 0.0000. 0.00. 0.02.00. 0. 0.0.00 5-5
ILLUSTRATIONS
Figure 1-1. DOS System Elements ....eoeooocsocararorvooreodsooareaaroresroaroce ro reo
Figure 1-2. DOS Memory Map ...cxesorocooscorooesonrsoogesooronraoe di e oantodo odon ee
Figure 1-3. Typical DOS Configuration ...0.00000000000 000.000. 0.0. 0.0.0. 2. 0.0.0.0... 0.0. 0.0.00 2 0 0.00
Figure 2-1. Core Map ...Qwssocsocscorecococooor eocacao ar or a orascordooco o 08. 0.0.0.0. 0. 0 8.8.0.0 ergo
Figure 3-1. Data Transfer Operations..,..eosesesorsoo:oseoororsoaredsoo ooanooear oarnooro
Figure 3-2. Control Operation Example. ..e.ocsssrocsoooooosoooaoao ooo oo ro oo aaoacaao
Figure 3-3. Parameter Blocks for SVC 2 Supervisor Calls ...e.eonneoorscooodsoaooradaoor e noo
Figure 3-4. Core Map ......++. 0004... 0002 80080 0 1 890 0 808 0 06 05 88 08 80000
Figure 5-1. A 0 00 000 1e 1000000000
Figure 5-2. I/O Logic Detailed FIOW. ....eorosrcorooorororoororoaroororaocareneroooo
00 = = = =n k= NW
TABLES
TABLE 1-1, OPERATING SYSTEM COMPARISON ...... 2200000 0000 000 0 000000000000. 1-7/1-8
TABLE 2-1. AVAILABLE EQUIPMENT ...ooocoroosorooorsorvaococorooreareooacreaoeo 2-11
TABLE 3-1. PRIVILEGED INSTRUCTIONS .. 202000 000 00 0 0 a 0 000 a 8 00 0 000000000000 3-1
TABLE 3-2. LOGICAL STATUS CODES RETURNED BY DOS, .......040 0000 000 8 4 000 8000 0 3-9
TABLE 3-3. CONSTANT TABLE + cv tv eo os osrosoosnrocssessscsssoesessenssscesss 3-16
TABLE 5-1, SYSTEM GENERATION STATEMENTS.........0. 000000 00000100 0000000000 5-2
APPENDICES
APPENDIX 1 APPROXIMATE NUMBER OF BYTES REQUIRED FOR
OPTIONAL SYSTEM MODULES. .. 2.440001 50 0 000 00 0 00 00 0 0 0 0 10 00100 6 A1/A2
CHAPTER 1
SYSTEM CONCEPTS
1.1 INTRODUCTION
The objective of an operating system is to provide a method of program management that, by establishing conventional
responses to external and internal stimuli, creates an environment in which user programs can function more nearly as
pure problem solvers. The Disc Operating System (DOS) creates such an environment. This manual describes the stan-
dards and conventions, and the convenience features of DOS that allow the user to program efficiently by concentrating
more on the problem at hand and less on the tasks of input/output processing and interrupt handling.
1.2 FEATURES
A significant feature of DOS is that it allows programs to be device independent. That is, I/O calls to DOS do not spec-
ify any device dependent information such as physical address and special format characters. Programs written to run
under DOS do not have to be modified when hardware is reconfigured or when new hardware is added. DOS fully sup-
ports the FORTRAN IV Compiler and the INTERDATA Assembler. It is a modularly organized system containing built-
in drivers for Teletype, Disc, High Speed Paper Tape Reader/Punch, Card Reader, Line Printer, Magnetic Tape, and
Cassette Tape. User written driver programs for special devices can easily be added to the system. DOS provides the
user with convenient and efficient methods of using an INTERDATA disc system, as a program preparation tool, a pro-
gram library, and an application data storage device. DOS, by means of a conditional generation procedure, may be
installed tailored to a user's hardware configuration; i.e., only those routines needed by the user are included in the
system,
Features of the Disc Operating System (DOS) are:
Concurrent Input/Output. I/O can be performed in both overlapped (I/O proceed) and non-overlapped (I/O Wait)
modes. All interrupts are automatically handled by the DOS executive.
Logical To Physical Device Independence. The user may, with minimum constraints, transfer logical control from
one physical device to another without modifying his program. Up to 16 user logical units (files) may be open at any
one time. The number of logical units available on a system can be established at System Generation time.
Batch Operation, Operator commands to DOS may be accepted from any input device including catalogued disc files,
allowing the user to batch job control statements. (e.g., FORTRAN Compile and GO operation, )
Named Files. The DOS allows the user to have up to 400 named files on a disc pack.
Allocation. DOS allows the user to initially allocate desired space to a disc file and automatically allocates further
disc space up to three cylinders to satisfy user requirements. This automatic overflow allocation is invisible to
the user.
File Manipulation. The DOS allows files to be named, examined, and manipulated. The user may copy a disc file
to another disc file, or may append a disc file to another disc file. In addition, files may be deleted and all files
may be listed with appropriate parameters.
1-1
File Attributes and Protection. Associated with each disc tile is a set of attributes which the user may specify.
These attributes include read and write protection plus data and file descriptors. The file protection feature allows
a user to save a file and protect against unauthorized access to that file,
Disc Access Methods. The DOS provides three access methods: sequential, random, and direct physical access.
Sequential mode is normally used to access records consecutively such as in compilations and assemblies whereas
random access mode allows accessing a particular record by specifying a logical record number. Random access
is useful in updating master files on disc and in accessing large tables that are kept on dise., Direct physical access
allows reference to logical sector numbers within a file, and permits rapid transfer of variable length records which
can be any number of sectors.
Variable Physical Record Length. The physical record size on disc may be varied at system generation time to
best suit the user's application. Physical record sizes may be 266, 512, 768, or 1,024 bytes. A small physical
record size is best suited for random applications, while a large record size increases throughput in sequential
operations,
Logical Record 1/0. DOS read and write requests to the disc are performed via logical records. DOS performs
all blocking and unblocking of physical records based on the specified logical record length of the file and the disc
physical record size. In all cases the user simply makes an I/O request for a read or write operation (specifying
the logical record number for random files).
Disc 1/0 via Supervisor Call, The user program performs all disc I/O via a SVC 1 instruction, which passes ap-
propriate parameters to the DOS executive. Specific operations which can be performed are described later but
basically the user specifies the operation as Read/Write, Wait/Proceed, Random/Sequential, or as a specific con-
trol operation (i.e., Rewind).
Disc 1/0 Buffering. To insure a minimum of accesses, the user may specify the length of the logical records with-
in a physical record as well as the access method. DOS determines if a logical record is already buffered in core
rather than do an unconditional access, and if a Write operation is requested, DOS places the logical record in the
DOS buffer and outputs the buffer only when necessary. In a sequential file, a Read operation is not performed prior
to sequential Write operations.
Overlays and Program Callable Programs. User programs running under the DOS can issue a SVC to fetch a named
overlay into memory or load a program and transfer control to that program. When an overlay is loaded, control is
returned to the main program. This capability is useful in FORTRAN programs which are too large for a memory
size but, when divided into a main program and one or more subroutines, can fit if the main program is resident and
the subroutines can overlay each other. The generation of overlays with the linkages to the main program and library
routines is handled by the OS Library Loader.
FORTRAN Programming with Random Accessing, A FORTRAN program may access a specific logical record by
calling a disc positioning subroutine (POSITN) prior to executing a Read or Write statement,
Disc Pack Interchange. The DOS allows the interchange of disc packs since all the disc pack control information
required by the DOS is resident on the disc pack.
DOS Bootstrap. A Bootstrap tape, Program Number 07-046, is provided for loading DOS from disc. A core image
of DOS is kept on Cylinder 0 of each disc pack.
System Generation. The user has the capability of tailoring his system to his own configuration and use, by means
of a System Generation assembly, thus assuring a compact DOS environment.
Compatibility. Programs which run under the INTERDATA Basic Operating System (BOSS) execute under DOS with
no modifications.
Operator Commands via Supervisor Call, DOS has a feature that allows operator commands to be executed via a
program supervisor call. A user program while running may, for example, allocate, open, and close files.
L.3 ELEMENTS OF THE SYSTEM
DOS is a modular system, made up of many elements which contribute to the whole system. The basic DOS modules—
he Executive, the Supervisor, the Loader-—and the various drivers combine to produce the complete DOS system. Re-
‘er to Figure 1-1.
OPERATOR
L
TTY OR
BATCH INPUT
SUPERVISOR
(COMMAND PROCESSOR)
4 4
SVCICALLS
DOS
RESIDENT SVC
LOADER DEVICE
oa
DRIVER
EXECUTIVE
USER SVC
PROGRAM DEVICE
DRIVER
|| DEVICE
DRIVER
INTERRUPT SERVICE
Figure 1-1. DOS System Elements
1.3.1 Executive
The executive handles all internal interrupts; supervisor call, arithmetic fault, illegal instruction, queue termination,
ind machine malfunction. In its handling of the supervisor call interrupt, it services all requests and initiates all 1/0
»perations. The executive is always entered as the result of an internal interrupt. All executive routines exit to the
1ser program state (PSW Bit 7 set).
1.3.2 Supervisor
This module is responsible for operator message logging, and for operator command processing. The supervisor issues
SVC calls to the executive portion of DOS. Operator commands are provided for:
System Initialization - PACK
Program Execution Controls - LOAD, CONTINUE, BIAS, START, TRANSFER, RUN, CLOSE, HALT
Device Controls - BSFM, FRFM, REWIND, WTFM, ASSIGN, LIST UNITS
Operator Debug Aides - OPEN, REPLACE, PLUS, MINUS
Disc File Management - ALLOCATE, ATTRIBUTE, DELETE, LIST, ACTIVATE, POSITION
System Utility - COPY
1.3.3 Loader
The DOS resident loader can be called by the operator or by a running program. It loads programs from the system li-
brary or any sequential device.
1. 3.4 Device Drivers
These routines, the unique coding sequences that control actual I/O transfers, are activated and terminated by the exec-
utive, Drivers are written such that interrupts are disabled for the shortest possible period of time, thus enabling the
system to remain responsive to external interrupts even while the executive is running, thus increasing throughput.
1.3.5 User Programs
A user program may consist of a single program, or it may include a main program and a number of subprograms and
overlays. User programs may be permanently resident in memory, or they may be loaded from the system library as
required. The total number of user programs allowed in memory at any given time is limited only by the amount of
memory available, but only one program may be in execution at any given time.
1.3.6 Other Programs
The OS Library Loader accepts its own set of operator commands and runs as a user program under DOS. It loads,
links, edits and produces object modules and overlays. The Hex Debug program contains features useful for debugging
(i. e., breakpoints) and various utility features such as memory save and memory dump. For details on these programs
see the appropriate program descriptions.
1.3.7 DOS Directory
The DOS Directory is a sequential file on Cylinder 1 of each disc pack containing the parameter information of all named
files on that pack. It is used by the supervisor for file management operations.
1.3.8 Memory
Figure 1-2 shows a typical memory map for a DOS System. DOS itself occupies the lower memory locations, Within
this area are the permanently resident system modules.
COMMON
ÉD
GET STORAGE AREA
USER
PROGRAM
AREA
DEVICE DRIVERS
DOS RESIDENT LOADER
DOS
SUPERVISOR AND EXECUTIVE
DEDICA TED
MEMORY LOCATIONS
CTOP (TOP OF COMMON)
COMBOT (BOTTOM OF COMMON)
UTOP (USER TOP OF MEMORY)
LDBIAS (UPDATED LOADER BIAS)
UBOT (USER BOTTOM OF MEMORY) =
SUPTOP (SUPERVISOR TOP)
SYSGO X'2D0'
Figure 1-2. DOS Memory Map
1-5
1.4 SYSTEM CONFIGURATION
1.4.1 Hardware Configuration
The minimum hardware configuration to support DOS with DISC is:
Model 5, 50, 70, 74 or 80 Processor
16KB Memory
Teletypewriter
Disc Controller with one Disc File (on a Selector Channel)
Refer to Figure 1-3 for a typical DOS configuration.
24KB
MEMORY BUS
MODEL 70 SELECTOR
CHANNEL
SELECTOR CHANNEL BUS
TTY MAGNETIC DISC
TAPES
CASSETTE | |PTR/P | CR HIGH SPEED LOW SPEED
| LP LP
Figure 1-3. Typical DOS Configuration
Other devices supported by DOS are:
1 High Speed Paper Tape Reader or Reader /Punch
1 Card Reader
2 Line Printers (high speed and/or low speed printers)
4 9-Track Magnetic Tapes (requires Selector Channel)
3 Additional Disc Files on the same disc controller
4 INTERTAPE Cassette units
1 Additional Teletype
Refer to Chapter 5 for System Generation (SYSGEN) and configuration details.
NOTES
1. In a Model 50 system generation, DOS provides trap
routines for performing RR format multiply and divide
instructions (X'0C' and X'0D'). These instructions are
normally illegal on a Model 50 Processor.
2. In a Model 74 system generation, DOS allows drivers
within DOS to perform the list instruction ATL SPTR,
LIOTRM (X'6470',X'035A").
1-6
1.4.2 Disc Allocation
DOS organizes a disc pack as follows:
Cylinder 0
Bootstrap Loader, 07-046.
Cylinder 1
- The DOS file directory is kept here, and is updated by the DOS supervisor.
- DOS itself is made resident on Cylinder 0, and can be loaded by the RTOS Bulk Storage
Cylinders 2 to 202 - (404 for double density drives) - These cylinders are available for allocation to named user
files.
1.4.3 Security and Protection
User disc files may be protected against both unwanted writes and reads. For more complete protection, files may be
assigned names with non-printing characters.
1.4.4 Relationship to other Operating Systems
DOS is one of several operating systems offered by INTERDATA which include the BOSS family of operating systems
Table 1-1 shows a comparison of data and features on INTERDA TA oper-
and the Real Time Operating System (RTOS).
ating systems.
TABLE 1-1. OPERATING SYSTEM COMPARISON
BOSS/4B BOSS/4A BOSS DOS RTOS
PROGRAM NUMBER 03-021 03-020 03-019 03-022 03-017
REFERENCE DOCUMENT | 29-216 29-216 29-292 29-293 29-240
CPU all except all except 5, 50, 70, 5, 70, 74, 5, 70,
3 3 74,80 50,80 80
1/0 METHOD WAIT INTERRUPT WAIT INTERRUPT INTERRUPT
CONTROLLED CONTROLLED CONTROLLED
BULK STORAGE NOT NOT YES YES (DISC YES
SUPPORTED | SUPPORTED FILE MANAGEMENT)
SIZE 3KB 4. 5КВ SOURCE SOURCE OBJECT
SYSGENABLE | SYSGENABLE SYSGENABLE
2.5-4. 5KB 4-10KB 16KB MIN,
BOSS/4B and BOSS/4A contain similar basic features, differing mainly in the I/O handling procedure. BOSS, an out-
growth of and replacement for BOSS/4B, includes disc and drum support. RTOS is a comprehensive Real Time Oper-
ating System which includes multiprogramming capability among other extensive features. DOS replaces BOSS/4A as
an interrupt driven system.
1-7/1-8
CHAPTER 2
DOS OPERATIONS
2.1 INTRODUCTION
During the period of program development, it is desirable to work with a communicative system that allows and encour-
ages operator intervention. The ability for operator communication is necessary in a system used for program develop-
ment, report generation, or data reduction. To meet these needs, DOS provides a comprehensive set of operator com-
mands in addition to its other features.
2.2 LOADING AND STARTING THE SYSTEM
Loading DOS for the first time, or reloading DOS from a device other than disc, requires the use of either the General
Loader, INTERDATA Program 06-025, or the Relocating Loader, INTERDATA Program 06-024. Either of these pro-
grams can be used to load the DOS object program produced by the System Generation process described in Chapter 5.
DOS is an absolute program that includes all the standard DOS modules and any user written modules required for the
particular system. Once this program has been loaded without error, the message "DOS" is printed on the Teletype
and DOS is ready to receive operator command input. All logical units are assigned to the system Teletype.
2.2.1 Re-Starting at SYSGO
To re-start at SYSGO, address location X'02D0', place the Processor in the Run mode, and depress the Execute switch,
This activates an initialize routine that performs the following actions.
1. It does a non-destructive top of memory search and sets an address in the memory map to indicate that all
memory above the top of DOS is available for loading user programs.
2. It disables the Memory Protect Controller if one is in the system.
3. It places the console Teletype in the Read mode, after logging the message "DOS", to indicate that the sys-
tem is ready. All logical unit assignments remain unchanged.
2.2.2 Loading from Bulk Storage Devices
Once DOS has been initially loaded and written to a disc, via a PACK initialize command, the core image copy can be
reloaded with the RTOS Bulk Storage Bootstrap Program 07-046. This program reads the core image of DOS into mem-
ory and starts the system at SYSGO. This loader is loaded with the 50 Sequence. Location X'007A' must contain the
disc file device number.
2.3 PROGRAM INTERRUPTS AND ERRORS
While user programs are running they may inadvertently generate error conditions that require some action by the sys-
tem. The action taken by the system depends on the severity of the error condition. I/O device errors may also occur.
When they do, the system does not log a message. Instead, the executive passes device status to the calling program
and leaves it to the program to output a message.
When a memory parity or power failure occurs, DOS logs the message:
ММ хххххххх
where xxxxxxxx is the PSW where the parity error occurred. Once the message is logged, DOS is ready to receive op-
erator command input. An interrupted user program may be resumed by entering CONTINUE.
NOTES
1. A program interrupted by a power failure may not be able
to be restarted if I/O was in progress at the time of the
power failure,
2. On systems without the AUTO RESTART option, the opera-
tor is required to depress the EXECUTE (RUN) switch to
enter DOS command mode.
2.3.1 1/0 Device Errors
When an 1/0 device error occurs, the system returns a halfword of error information to the program. The first byte of
this halfword is an encoded error status; the second byte is the device address. Many programs log a message to the
console device that includes the error condition and device address, such as:
I/O ERR xxpa
where xx is the error status and pa is the device address. The error status conditions are:
1. X'A0' - Device unavailable, Check to insure the davice is on-line and functioning properly. If the device ad-
dress is that of a non-existent device, check the logical unit assignments.
2. X'CO' — Illegal operation. Check the logical unit assignments. This type of error occurs if, for instance, a
Write operation is attempted on a read only device.
3. X'90' - End of medium. The action to be taken depends on the program. For example, it may mean mounting
a new tape.
4, X'84' - Unrecoverable data error; i.e., parity fail. Action depends on the type of program. It may be enough
to reassign logical units,
5. X'88' - End of file. On magnetic tape devices or disc, the program has read through an End of File Mark. Ac-
tion to be taken depends on the program.
2-2
2.3.2 Privileged or Illegal Instruction
If a program attempts to execute an instruction for which the operation code is illegal or privileged, the system responds
by aborting the program and logging the message:
I] XXXXXXXX
where xxxxxxxx is the PSW where the instruction occurred. This message also occurs if a user program attempts a
supervisor call with an invalid logical unit number.
2.3.3 Arithmetic Fault Interrupts
There are two types of arithmetic fault interrupts, fixed point and floating point. DOS logs one of the following messages
and continues the interrupted program at the next instruction.
Fixed Point Divide Fault:
Floatinz Point Arithmetic Fault:
where XXXXxxxxX is the interrupted PSW.
2-3
2.4 OPERATOR COMMAND PROCESSOR
The operator command Processor (supervisor) interprets and acts upon directives received from the operator through
the Teletype or other system input devices. If the system Teletype is the command input device DOS types an '*' indi-
cating that it is ready to accept command input. Characters are read as typed and passed to the supervisor. If a back
arrow is typed (e—), the previous character is deleted. If a hash mark is typed (#), the current line is deleted, After
72 characters have been typed, or when a Carriage Return is recognized, the supervisor is activated. Operator com-
mands consist of at least ona command word such as:
START
Only the first two characters of the command word need be typed. The command is interpreted on the basis of these two
characters and anything between them and the first blank is ignored. Some commands require one or more operands,
which are separated from the command word by a single blank,
ASsign XXXX
Multiple operands must be separated by commas, for example:
ASsign XXXX, YYYY, ZZZZ
In some commands there are optional operands which come at the end of the operand string, The notation used to de-
scribe these commands is:
TR XXXX[, YYYY]
indicating that if the operand is not used, the preceding comma must also be left out. In some cases, there is more
than one optional operand. These operands may be left out optionally from right to left.
A Llocate XXX [, YYYY, ZZZZ, DDDD |
If for any reason, such as a misspelled command or incorrect operand, the supervisor cannot react to the command, it
returns with the message:
2.4.1 Commands for Mass Storage Devices
The following commands relate to disc based files. They enable the operator to define, redefine, and examine the limit.
of mass storage files. Each disc pack on the system may be divided into as many as 200 (400 if double density) separate
files. The files are named by the user. Each name contains from one to six printing or non-printing characters. Com
bining the file name with the device address of the disc pack completes the identification of the file.
2-4
ALLOCATE
The ALLOCATE command is used to reserve a named area on a particular physical disc pack. It may also be used to
assign a file to a specific logical unit number at the time of allocation.
AL NNNNNN [, UPP, CCC, LLLL]
where NNNNNN is the name to be assigned to the disc file.
U is an optional logical unit to which the file is to be assigned.
PP is the physical disc pack address in hex (default value X'C6').
CCC is the decimal number of cylinders to be allocated to the file (default value 1).
LLLL is the decimal logical record length of the file in bytes (default value 108).
Note that 108 has been chosen as the default value for LLLL because program object records are 108 bytes long, and
occur often in system operations.
Examples:
AL SOURCE, 3Cs, 20, 80 Allocate a 20 cylinder file called SOURCE on pack C6, assign to logical unit 3
with a record length of 80.
AL OBJECT, C6, 2 Allocate a 2 cylinder file called OBJECT on pack C6 with a record length of 108.
AL OBJECT, D6 Allocate a 1 cylinder file called OBJECT on pack D6 with a record length of 108.
AL OBJECT Allocate a 1 cylinder file called OBJECT on pack C6 with a record length of 108.
An ALLOCATE command may generate the following messages if error conditions are recognized.
NA-ERR NNNNNN already occurs on the specified disc pack.
LU-ERR U is invalid.
PU-ERR PP is invalid (must be C6, D6, E6, or F6).
CY-ERR The number of cylinders to be allocated (CCC) do not exist contiguously on the specified disc
pack. (200 cylinders are available on a single density disc pack.)
RL-ERR LLLL is larger than the SYSGEN value for disc physical record length.
Programming Note:
To calculate the number of cylinders needed for initial allocation of a file, the following approximation may be used:
C = INT N*P ) +1
256+ D*INT(P/L)
where C = approximate number of cylinders required.
N = number of records in the file.
L = logical record length in bytes.
P = disc physical record length (usually 256; established at system generation).
D = sector density (48 for single density disc).
(96 for double density disc).
and the function INT refers to the integer portion of the value within the parenthesis.
2-5
Beyond the initial allocation, DOS automatically allocates up to three overflow cylinders for sequential files and for ran-
dom files if accesses are within three cylinders of the initial allocation. The user is not informed immediately when
overflow cylinders have been allocated. The user may determine file overflow status by using the LIST command. Over-
flow cylinders are only allocated on Write operations, and never for files using the direct physical access method. If
overflow cylinders cannot be allocated, because of the above conditions, or because no free cylinders remain, EOM sta-
tus is returned to the user.
ACTIVATE
This command assigns a previously allocated named disc file to a logical unit number.
AC NNNNNN, U[PP, A]
where NNNNNN is the name of the disc file to be activated.
U is the logical unit number.
PP is the optional physical disc pack number (default value is C6).
A is an optional modifier indicating the file is to be opened at the next available unused record. This re-
sults in an append operation for sequential files. If A is not specified, the file is opened at logical re-
cord 0 (a logical rewind).
Examples:
AC SOURCE, 3D6, A Assign file SOURCE on pack D6 to logical unit 3 using the file append feature.
AC OBJECT, 2D6 Assign file OBJECT on pack D6 to logical unit 2,
AC OBJ, 2 Assign file OBJ on pack C6 to logical unit 2.
An ACTIVATE command may generate the following messages if error conditions are recognized:
NA-ERR NNNNNN does not exist of the specified disc pack.
LU-ERR U is invalid.
PU-ERR PP is invalid (must be C6, D6, E6, or F6).
Programming Note:
After activation, a file remains assigned to a logical unit until the logical unit is reassigned or the PACK command is
given.
2-6
PACK
This utility command has two forms:
1. PA PP (CHANGE PACK)
where PP is the physical disc address, indicating to the system that a disc pack has been changed on drive PP. Any
logical units that were previously assigned to disc files on the removed pack are now assigned to the system Teletype,
thus insuring against accidental destruction of data on the new pack.
2. PA PPA (INITIALIZE PACK)
initializes the disc pack with device address PP. The entire file directory and allocation map are zeroed (Cylinder 1),
thus any previous data on the disc can no longer be referenced by the system. The initialize command also checks all
cylinders to determine if the defective track bit is set. Defective cylinders are flagged as "in-use" in the cylinder al-
location map, thus making them non-allocatable. In addition, initialization outputs a core image of DOS to Cylinder 0,
thus making DOS available for bootstrap loading. Before using the pack initialize command on a disc pack for the first
time, the pack should be formatted with Disc Test/Format Program 06-122,
If PP is not C6, D6, E6, or F6, then the message PU-ERR is logged on the console.
ATTRIBUTE
This command is used to define certain characteristics of a disc file.
AT NNNNNN, XX sX aX, [, PP]
where NNNNNN is the name of a previously allocated disc file.
X1X9X3X4 is the required attribute value of one to four hex digits. If one digit is present, it is assumed to be X4.
If two digits are present, they are assumed to be X3X4, etc.
PP is the optional physical pack number (C6 is the default value).
Description of Attributes:
Hex digit Xj = unused
Hex digit Xo = unused
Hex digit Xg = 0 sequential
1 random (access method)
2 direct physical
Hex digit X4 = 0 unprotected
1 write protected (file protection)
2 read protected
2-7
Programming Notes:
When a disc file is allocated, the default atiributes are 0000. File attributes may be changed later by the ATTRIBUTE
command. This command causes the attribute to be immediately changed on the disc directory. If the file has already
been activated, a reactivation is not necessary to reflect the new attributes, If a SVC 1 attempts to write to a write pro-
tected file or read from a read protected file, illegal function status is returned to the caller. Attributes XxX and X
may be specified for information purposes but are not presently used in system operation. Unspecified attribute digits
are set to zero.
The sequential or random nature of a data transfer is determined by the SVC making the request. The sequential and
random file attributes are used only to aid system efficiency; i.e., sequential Write operation to files with sequential
attributes do not cause a preceding read.
When a file is designated as direct physical, two rules hold for all 1/0 transfers.
1. The random address supplied by the SVC is assumed to be the starting logical sector of the data transfer
within the file.
2. The length of the data transfer is determined by the starting and ending addresses of the SVC call.
Examples:
AT SOURCE, 11, D6 Make file SOURCE on pack D6 a write protected, random file.
AT OBJ, 0 Unprotect file OBJ on pack C6.
The ATTRIBUTE command may generate the following messages if error conditions are recognized.
NA-ERR NNNNNN does not exist on the specified disc pack.
AT-ERR invalid attribute (X1XoXg3X4 is invalid).
PU-ERR PP is invalid (must be C6, D6, E6, or F6).
DELETE
This command removes a file from the disc pack library and releases its cylinders for use by subsequent allocations.
DE NNNNNN [, PP]
where NNNNNN must be a currently allocated file.
PP is an optional physical pack address (C6 is the default value).
NOTE
A read or write protected file may not be deleted. The
attribute must be changed to remove protect status.
Examples:
DE SOURCE, D6 Delete file SOURCE on pack D6.
DE OBJ Delete file OBJ on pack C6.
The DELETE command may generate the following messages if error conditions are recognized.
NA-ERR NNNNNN does not exist of the specified disc pack.
AT-ERR File NNNNNN is protected.
PU-ERR PP is invalid (must be C6, D6, E6, or F6).
CLOSE
CL
The CLOSE command performs the following two functions.
1. If the DOS disc buffer contains any logical records that have been written to/from a user program and not
physically written on the disc, then these records are written on the disc.
2. The file parameter information for any currently activated files are updated on the disc library. If a disc
file is assigned to more than one logical unit, the parameter information of the highest logical unit is used
to update the library.
Programming Note:
A SVC EOJ causes a close operation to occur. If a program using disc is terminated by an SVC PAUSE, a console inter-
rupt, or any means other than a SVC EOJ, a CLOSE command may be needed to insure that all initiated disc transfers
have been physically completed.
LIST
LI U[PP]
This command lists the entire file directory for physical disc device address PP (default value is C6) on a list device
whose logical unit is U. The following is the heading and format for the List printout. Each file prints one line of data:
NAME CYL RECL USED ATRB OV
NNNNNN CCC LLLL DDDD XXXX O
where NNNNNN is the file name.
CCC is the decimal number of cylinders initially allocated.
LLLL is the decimal logical record length.
DDDD is the decimal number of records used (sequential files only); last logical record written (direct and ran-
dom files).
XXXX is the hex attribute halfword.
O is the number of overflow cylinders in use.
2-9
Example:
LI 3C6
NAME CYL RECL USED ATRB OV
SOURCE 15 80 2010 0001 0
OBJECT 1 108 150 0000 1
RUN
RU NNNNNN[, PP]
This command instructs DOS to load an object program contained on file NNNNNN on physical pack PP (default value i
C6). After loading, DOS transfers to the origin of the program or the program transfer address, if specified.
The RUN command resets the loader bias to UBOT before loading.
Example:
RU FORTRN (Execute FORTRN on pack C6.)
The RUN command may generate the following messages if error conditions are recognized.
NA-ERR NNNNNN does not exist of the specified pack.
PU-ERR PP is invalid (must be C6, D6, E6, or F6).
2.4.2 General Commands
ASSIGN
This command establishes the logical to physical relationship required for all non-disc I/O calls in DOS. (Its disc
counterpart is ACTIVATE.)
The format is:
AS UPP[, UPP, UPP, UPP
where U is the logical unit number
PP is the physical device address in hexadecimal notation.
DOS allows logical unit Numbers 0 through F, The physical device addresses recognized by DOS are maintained in 1
Available Equipment Table (see Table 2-1) which is created by the system generation procedure (see Chapter 5). (T
Available Equipment Table is referenced AETAB in the DOS listing.)
TABLE 2-1. TYPICAL AVAILABLE EQUIPMENT
DEVICE ADDRESS
(HEXADECIMAL) DEVICE
02 Teletype Keyboard/Printer
03 High Speed Paper Tape Reader
04 Card Reader
13 High Speed Paper Tape Reader/Punch
| 62 Line Printer
85 Magnetic Tape (9 Track)
95 Magnetic Tape (9 Track)
FF Teletype Reader/Punch
00 Null Device
45 Cassette Tape
59 Cassette Tape
B6 Disc Controller
An example of the ASSIGN command is:
ASSIGN 213,500
This command establishes a relationship between logical unit 2 and physical address 13 so that all program references
to logical unit 2 are directed to the DOS driver program for physical device 13, and causes logical unit 5 to be associated
with the Null device which suppresses all I/O activity related to logical unit 5.
The ASSIGN command:
ASSIGN O1FF
associates logical unit 01 with the Teletype Reader/Punch device. This is not actually a separate device with physical
address FF. It is a fictitious device whose use directs DOS to a special entry point in the Teletype driver to perform
tape operations. This mechanism provides users with only Teletype 1/0, to obtain Assembler and FORTRAN listings
in which the source input is not interleaved with the list output. If a second Teletype has been SYSGENed into the system
the TTY Reader/Punch device number is X'FE',
Logical unit assignments remain in force until changed by another ASSIGN, ACTIVATE or PACK command. Logical units
0 through F may be assigned to any physical device for which there is an entry in the Available Equipment Table. If an
ASSIGN command references a logical unit greater than F, or an unrecognized physical device address, DOS rejects the
command and types out a question mark, More than one logical unit may be assigned to one physical device, but a single
logical unit cannot be assigned to more than one physical device. If this is attempted, only the final assignment remains
in force,
BIAS and LOAD
The BIAS command sets a constant in DOS (LDBIAS in listing), which is used by the DOS resident loader as the origin c
relocatable object programs. Its format is:
BI xxxx
where xxxx is the desired program origin expressed in hexadecimal notation.
The LOAD command activates the DOS resident loader. Its format is:
IO U
where U refers to a logical unit that has previously been assigned to a physical device, Figure 2-1 shows the effects oi
the LOAD and BIAS commands.
Го
(А) f ero? (B) ero. (C) стор
Le BOT | com о COMMON
COMB
(Los!
1 UTI
USER
PROGRAM
LDBIAS
LDBIAS ВОт
UBIT
UTOP Tes
UTOP
Dos DOS DOS
X'0000' Xx '0000' x'0000'
CORE MAP - DOS CORE MAP CORE MAP - USER PROGRAM
LOADED AND INITIALIZED BIAS SET BY BIAS COMMAND PREPARED BY OS LIBRARY
LDBIAS = UBOT LOADER LOADED BY DOS
RESIDENT LOADER
NOTE:
CTOP = TOP OF CORE
COMBOT = BOTTOM OF COMMON
UTOP = TOP OF USER PROGRAM
LOBIAS = LOAD BIAS
UBOT: BOTTOM OF USER CORE AREA
Figure 2-1. Core Map
Use of the BIAS Command. When DOS is first loaded or when it is reinitialized, the Load Bias Constant (LDBIAS) is s
equal to the first available memory address above the top of DOS, see Figure 2-1(A). When the BIAS command is ente
LDBIAS is set equal to the operand value, see Figure 2-1(B), For example:
BIAS 1500
sets LDBIAS to hexadecimal 1500. Use of the BIAS command is optional. The loader uses the current value of LDBI/
as the origin of relocatable programs and updates the value after each load. DOS permits a BIAS value to be set such
that the user may overlay a section of DOS from location LOKUP to SUPTOP, to allow loading of large user programs
If the user does not want to overlay DOS he must enter a value at or above SUPTOP.
2-12
Use of the LOAD Command. The LOAD command must be preceded by an ASSIGN or ACTIVATE command. For exam-
ple:
ASSIGN 713 or AC OBJECT, 7
LOAD 7
assigns logical unit 7 to a physical file or device, and executes the resident loader with instructions to load from logical
unit 7. This sequence shows the ASSIGN command immediately before the LOAD command. This is not a requirement.
The only requirement is that a valid assignment be in force at the time the LOAD command is entered.
Loader Operation. The DOS resident loader loads binary object programs in loader format as generated by the Assem-
bler, OS Library Loader and Hex Debug. Either zoned programs, labeled M08 or M09, or non-zoned programs labeled
M16 or M17 can be loaded. The resident loader also loads binary data in loader format from 9 Track Magnetic Tape or
disc. The loader performs all loader functions, including relocation and forward reference chaining, except the follow-
ing:
1. EXTRNS and Common references (from a compiled FORTRAN program) cause the message LD ERR to be
typed out. The Load operation terminates, and DOS waits for command input from the Console Teletype.
2. ENTRYs and LABELs are ignored. These items are passed over by the loader and the operator is given no
indication or message.
3. Transfer addresses, if specified, are stored by the loader, but transfer to the loaded program does not occur
at the completion of the load. The stored transfer address can be used in conjunction with the START com-
mand described below.
As soon as the resident loader is properly activated, it types out the message:
BIAS xxxx
where xxxx is the current value of the Load Bias Constant. During the load process, it types out the message:
LD ERR
EOJ
if the load address is less than location LOKUP in DOS, It types out the message:
SEQ ERR
PAUSE
if it detects a sequence error in the input records. If it computes a checksum that does not agree with that of the input
record, it types out the message:
CKSM ERR
PAUSE
2-13
Following either sequence or checksum errors, the operator can reposition the input device, if paper tape, and resume
the Load operation by typing CONTINUE. If the calculated load address at any time exceeds the top of core (CTOP in
Figure 2-1), the message:
MEM FULL
EOJ
is typed out. If an 1/0 error occurs during the load, the loader types out the message:
I/O ERR xxx
PAUSE
where xxxx is the error status and device address (see Chapter 3). The I/O can be retried by typing CONTINUE. At
the end of each load, the loader types out the message:
END xxxx
EOJ
where xxxx is the adjusted value of the Load Bias (LDBIAS), see Figure 2-1(C).
BIAS commands with no operand field or with an operand less than location LOKUP in DOS are rejected with a question
mark. For especially large user programs the user has the means of overlaying several utility routines near the top of
DOS, from location LOKUP to the top of DOS (UBOT). The user should refer to the DOS listing for the routines that lie
between location LOKUP and location UBOT. I the user loads a program below location SUPTOP, he must reload DOS
before using any commands in Section 2, 4, 1.
START
The START command causes DOS to transfer control to a previously loaded user program. The format is:
ST xxx
where xxxx is the hexadecimal address of the first instruction to be executed.
The operand field (starting address) is optional in the START command. If it is omitted, DOS starts the program at the
transfer address specified on loading. If no transfer address has been specified, DOS transfers control to the instructio
located at the first halfword above DOS (UBOT in listing), When the user program is started, all internal and external
interrupts are enabled. The following table describes the PSW bits of the user program state.
RIT MFANING VALUE
у WAI'l STATE 0
1 EXTERNAL INTERRUPT ENABLE 1
2 MACIINE MALFUNCTION INTERRUPT ENARILFE 1
3 FIXED POINT DIVIDE. FAULT INTERRUPT ENABLE 1
4 AUTOMATIC 1/0 SERVICE F NABLE 1
5 FLOATING POINT ARITHMETIC FAULT INTE RRIJPT ENABLE 1
6 CHANNEL TERMINATION INI FRRUP'T ENABLE 1
7 РН) СТ МОРЕ 1
8-15 0
The starting address specified by the START command must not be less than the value of location LOKUP in DOS (except
zero, which is interpreted as "no operand"), If the starting address is less than LOKUP, DOS rejects the command and
types out a question mark.
2-14
@ (At sign)
The @ suspends a currently running user program, The format is:
@
Upon receipt of a @ command, DOS types PAUSE and suspends the user program. The user Program Status Word and
registers are saved, and any 1/0 in progress is allowed to go to completion. The program can be restarted with the
CONTINUE command described in the following paragraph. The @ command can be entered at any time after the START
command and before the program terminates itself with an END OF JOB supervisor call (see Chapter 3). If the @ com-
mand is entered at any other time, it is rejected with a question mark.
CONTINUE
The CONTINUE command causes a previously suspended program to be restarted at the next instruction as indicated by
the saved user Program Status Word. The format is:
CO
The CONTINUE command can be entered after a programmed halt (SVC PAUSE), a memory parity interrupt, or after the
@ operator command,
OPEN, REPLACE, PLUS, and MINUS
These commands are used to examine and replace specified core locations. The format of the OPEN command is:
OP xxxx
where xxxx is the address, in hexadecimal, of a core location. DOS responds by typing out the contents of the specified
location. For example:
OPEN 12F0 (Entered by operator to open location 12F0.)
4300 (Contents of 12F0 typed out by DOS, )
When DOS is loaded, the address of the currently open location is set to zero. Any subsequent OPEN command may
change this address, but DOS does not reset it on initialization or restart. The format of the REPLACE command is:
RE xxxx
where xxxx is the value, in hexadecimal, that is to replace the contents of the currently open location. The REPLACE
command is usually preceded by an OPEN command, For example:
OPEN 12F0 (Entered by operator to open location 12F0. )
4300 (Contents of 12F0 typed out by DOS. )
REPLACE 4130 (4130 replaces 4300 in location 12F0. )
2-15
The PLUS (+) and MINUS (-) commands have the format + and -. They are used with the OPEN and REPLACE commands
to open the next location or the preceding location. For example:
OPEN 12F0 (Entered by operator to open location 12F0.)
4300 (Contents of 12F0 typed out by DOS.)
REPLACE 4130 (4130 replaces 4300 in location 12F0.)
+ (Entered by operator to open location 12F2. )
13D8 (Contents of 12F2 typed out by DOS.)
OPEN 12F0 (Entered by operator to open location 12F 0.)
4130 (Contents of 12F0 typed out by DOS.)
- (Entered by operator to open location 12EE.)
12F8 (Contents of 12EE typed out by DOS.)
2.4.3 1/0 Control Commands
There are four operator commands which allow the operator to control magnetic tape, cassette, or disc from the syster
console. They all have a single operand which is the logical unit assigned to the desired physical device.
The commands are:
Write File Mark WF U
Skip Forward to File Mark FF U
Backspace to File Mark BF U (Magnetic Tape and Cassette only; rewinds a disc file)
Rewind RW U
where U is the logical unit number,
These commands are ignored if an improper device is specified. For disc files a logical record consisting of X'1313' i
written as a file mark.
LIST LOGICAL UNIT
This command, which has the form:
LU [U]
which lists all the logical to physical assignments of DOS on a list device specified by logical unit U. If U is omitted tl
Teletype is assumed as the list device. ‘The output heading and format is as follows:
LU PU NAME
U PP NNNNNN
where U is the hexadecimal logical unit number.
PP is the physical device number,
NNNNNN is the file name if a disc file.
2-16
Example:
AS 162 Assign logical unit 1 to the line printer.
LUI List logical unit assignments on the line printer.
LU PU NAME
0 02
1 62
2 C6 SOURCE
3 D6 OBJECT
TRANSFER
The TRANSFER command is used to allow the supervisor to read command input from devices other than the Teletype
(i. e., job control batch input). It also allows the user to log input commands on a list device if desired. The TRANS-
FER command has the form:
тв [01,05]
where U, is the logical unit of the new command input device and Us is the logical unit of the command log device. If
U, is omitted, no logging occurs. If Uy is omitted, command input control is returned to the Console Teletype.
Examples:
AS 204,162 Assign the card reader and the line printer.
TR 2,1 Transfer to card reader, log on line printer.
TR 2 Stop logging.
TR Transfer back to TTY.
Note that several conditions cause control to be unconditionally returned to the Teletype:
1. An error in the command input statement.
2. An I/O error on any device involved in the command.
3. A SVC PAUSE.
4. Re-starting DOS at SYSGO.
Uy may be assigned to any input device, while U, may be assigned to any output device.
Note that a command input logging feature has been added to the OS Library Loader (03-030) which corresponds to the
log feature of the TRANSFER command. The Library Loader accepts the command:
LG XUU
where UU is the logical unit of the log device. The digit X is used to suppress the message 'LOADER' after each com-
mand in cases where commands are not being read from the Teletype. If X=0 the 'LOADER' message is not suppressed;
if X=1 the 'LOADER' message is suppressed.
All Loader commands read from the Loader command input unit (logical unit 5) are logged on the specified logical unit.
If U=0, then no logging will occur.
Examples:
DOS AS 504,362
Commands TR 5,3
ST
LOADER | LG 103
Commands LG 3
LG O
COPY
The COPY command allows the user to copy a file from any input device to any output device. The command is:
CP U,,U,
where U, is the logical unit of the input device.
Us is the logical unit of the output device.
, DDDD [,A ]
Assign card reader and line printer.
Transfer to the card reader.
Start loader.
Log loader commands on printer, and suppresses 'LOADER' messag
Continue logging and restore 'LOADER' message.
Stop logging.
DDDD is the input logical record length (decimal).
A is an optional modifier indicating termination of the COPY operation only on recognition of a file mark (dise,
magnetic tape and cassette only).
If DDDD is zero, DOS assumes the input file to be 108 byte loader format records and terminates the COPY operation
after a single program has been copied (the end program record has been recognized). If DDDD is specified, DOS
assumes ASCII or binary data and terminates the COPY operation on an END statement (B¥......BEND), If the modi-
fier "A" is specified, the COPY operation is terminated only by a file mark. If an output disc file does not have suffi-
cient logical record length, then data up to the disc files record length is transferred. If DDDD is less than an input
disc file's record length, the DDDD bytes are transferred.
POSSIBLE
SOURCE DEVICES
Card Reader
HSPTR
TTY Reader/Keyboard
Magnetic Tape
Disc
Cassette Tape
Examples:
AS 104,262, 485
AC SOURCE, 5
AC LIBRY,6
AC SCRT, 7
CP 1,2,80
CP 6,4,0,A
CP 5,7,80
Note that the COPY command issues a SVC 2 GET STORAGE to obtain a buffer area.
to the length of the logical record being copied.
2-18
POSSIBLE
DESTINATION DEVICES
Line Printer
HSPTP
TTY Punch/Printer
Magnetic Tape
Disc
Cassette Tape
Assign the card reader, line printer and magnetic tape.
Activate disc files.
ASCII card to print, 80 columns.
Copy entire program library on disc to tape.
Copy ASCII disc to disc,
The length of the buffer is equal
POSITION
This command may be used to position a file to a subfile contained within it. The beginning of a subfile is defined by a
label record.
**NNNNNN
where NNNNNN is the name of the subfile. NNNNNN may be from one to six characters, with trailing blanks.
The POSITION command is of the form:
PO NNNNNN, U
where NNNNNN is the desired name, and U is the logical unit of the device containing the subfile. The POSITION com-
mand searches from the point where the file is positioned until the subfile NNNNNN is found or until an EOF or EOM
condition is encountered. If either of the later conditions occur, the message I/O ERR XXXX is logged on the Teletype.
If subfile NNNNNN is found, DOS returns to command mode, and the file remains positioned at the record following the
label record.
Example:
The user wishes to create a disc file (JOBCTL) containing several job control programs, each having a unique name. A
card deck may appear as follows:
**JOBCT1
AS 104,213, 362
AC SCRT, 4
RU ASMBLR
TR 0
** JOBC T2
PA C6,A
AL SCRT, C6, 30,80
TR 0
** JOBCT3
END
After copying his card deck to file JOBCTL, the user may, for example, execute the second job control program by the
following commands:
AC JOBCTL, 3
PO JOBCT2, 3
TR 3
The POSITION command may also be used for source programs, user data files, etc., and on any input device. It allows
the user to group large numbers of small files on a single disc file, resulting in more efficient usage of the disc.
2-19
2-20
2.4.4 Summary of DOS Operator Commands
ALLOCATE
ACTIVATE
PACK
ATTRIBUTE
DELETE
CLOSE
LIST PACK
RUN
ASSIGN
BIAS
START
CONTINUE
OPEN
REPLACE
PLUS
MINUS
HALT
WRITE FILE MARK
SKIP FORWARD FILE MARK
BACKSPACE TO FILE MARK
REWIND
LIST UNITS
AL NNNNNN[, UPP,CCC, LLLL]
File name, logical and disc physical unit, number of cylinders, logical re-
cord length.
AC NNNNNN, U[PP, A]
File name, logical and disc physical unit, file append modifier.
PA PP[,A]
Disc physical unit, pack initialize modifier.
AT NNNNNN, Xx [ PP]
File name, attribute halfword, disc physical unit.
DE NNNNNN [, PP]
File name, disc physical unit.
CL
LI U[PP]
List device logical unit, disc physical unit.
RU NNNNNN[, PP]
File name, disc physical unit.
AS UPP[, UPP, UPP, UPP]
Logical unit, physical unit other than disc.
BI XXXX
Program origin location.
LO U
Load device logical unit.
ST [хххх ]
Address of first instruction to be executed.
CO
OP XXXX
Memory address to be examined.
RE XXXX
Value to be replaced.
+
@
WF U
FF U
BF U
RW U
Logical unit of desired device.
LU [u]
Logical unit of list device,
TRANSFER TR [U, U]
Logical unit of input device, logical unit of log device.
COPY CP U,U, [DDDD,A |
Logical unit of input device, logical unit of output device, logical record
length, file mark termination modifier.
POSITION PO NNNNNN, U
Subfile name, logical unit.
2.4.5 Summary of DOS System Messages
EXEC MESSAGES
ILLEGAL INSTRUCTION II XXXXXXXX
PARITY/POWER FAILURE MM XXXXXXXX
FIXED PT DIVIDE FAULT FD XXXXXXXX
FLT PT ARITHMETIC FAULT DF XXXXXXXX
END OF JOB EOJ
PROGRAMMED HALT PAUSE
RESIDENT LOADER MESSAGES
BIAS VALUE BIAS XXXX
LOAD ERROR LD ERR
SEQUENCE ERROR SEQ ERR
CHECKSUM ERROR CKSM ERR
MEMORY FULL MEM FULL
INPUT/OUTPUT ERROR I/O ERR XXXX
END PROGRAM ADDRESS END XXXX
SUPERVISOR MESSAGES
INPUT/OUTPUT ERROR I/O ERR XXXX
COMMAND INPUT ERROR ?
FILE NAME ERROR NA-ERR
LOGICAL UNIT ERROR LU-ERR
PHYSICAL UNIT ERROR PU-ERR
ATTRIBUTE ERROR AT-ERR
NUMBER OF CYLINDERS ERROR CY-ERR
RECORD LENGTH ERROR RL-ERR
DOS
READY FOR COMMAND INPUT {
*
2-21/2-22
CHAPTER 3
APPLICATION PROGRAMMING
3.1 PROGRAMMING CONVENTIONS
Programs written to execute within the framework of DOS must adhere to certain established conventions to preserve
the integrity of the system and to make the best use of the I/O and other supervisor services performed by DOS.
3.1.1 Privileged Instructions
The major constraint on user programming deals with the use of instructions that affect the status of the system. Be-
cause DOS controls all I/O and interrupts, user programs must not issue any instructions related to I/O functions or
any instructions that change the current program status, All user programs run with external interrupts enabled, but
selected internal interrupts may be disabled by a special request to the system. Table 3-1 lists the Privileged instruc-
tions. Use of these instructions results in an illegal instruction interrupt.
TABLE 3-1. PRIVILEGED INSTRUCTIONS
LPSW SINT
EPSR AL
WBR WB
RBR RB
WHR WH
RHR RH
WDR WD
RDR RD
SSR SS
OCR OC
AIR Al
3.2 SUPERVISOR CALL
User programs must have a means of accessing peripheral devices and, in general, of communicating with the system
in a dignified manner. INTERDATA's answer is the supervisor call interrupt, an interrupt generated by the task itself
whenever it executes a Supervisor Call instruction. The format of the Supervisor Call instruction is:
SVC R1,A(X2)
The hardware interprets the R1 field as a value rather than a register designation. It uses this value to index to 1 of 16
unique locations for servicing the interrupt. The A(X2) field, an address, is saved in a special location from which the
servicing routine can retrieve it. DOS does not use all of the 16 possible variations on the Supervisor Call instruction.
It recognizes only six, and uses codes in the location specified by the A(X2) field to achieve further variations. Those
not recognized are treated as illegal instructions. A summary of DOS supervisor calls follows:
SVC 1,A(X2) INPUT/OUTPUT OPERA TIONS
SVC 2, A(X2) CODE 1 - PAUSE
CODE 2 - GET STORAGE
CODE 3 - RELEASE STORAGE
CODE 4 - SET STATUS
CODE 5 - FETCH POINTER
CODE 6 - UNPACK
CODE 7 - LOG MESSAGE
SVC 3,0 END OF JOB
SVC 4, A(X2) EXECUTE JOB CONTROL STATEMENT
SVC 5, A(X2) FETCH OVERLAY
SVC 6, A(X2) CALL A USER PROGRAM
Assigning these functions to the various supervisor calls is arbitrary. BOSS uses SVC 1 for I/O, SVC 3 for End of Job,
and SVC 2 for all other supervisory services. These calls are retained in DOS for the sake of compatibility. The other
calls were given unique SVC numbers to make them easier to use and easier to remember.
3-2
3.3 INPUT/OUTPUT PROGRAMMING
All supervisor calls that initiate operations on peripheral devices have two things in common. First, the first operand
of the Supervisor Call instruction has a value of one; and second, the parameter block pointed to by the second operand
consists of at least a function code and a logical unit, for example:
SVC 1, PARBLK 1/0 SUPERVISOR CALL
PARBLK DC Х'хххх' FUNCTION CODE AND LOGICAL UNIT
. ADDITIONAL
. PARAMETERS
. AS REQUIRED
The logical unit number, which occupies the second byte of the 'FUNCTION CODE LOGICAL UNIT' halfword, identifies,
through the logical unit table, the peripheral device involved in the requested operation. Since DOS allows up to 16 log-
ical units, this byte may have any value between X'00' and the number of logical units specified at SYSGEN time.
If an invalid logical unit is specified, the illegal instruction message II xxxxxxxx is logged and the program is suspended.
(XXXXXXXxx=PSW of the invalid supervisor call.)
The first byte of the "FUNCTION CODE AND LOGICAL UNIT' halfword contains a value that, upon interpretation by the
system, specifies the type of I/O operation. The most general interpretation of this byte hinges on the condition of its
first bit, Bit 0. Setting this bit (Bit 0=1) indicates to the system that the program is requesting a control operation,
such as Rewind, Backspace, or Write File Mark. Since these operations are meaningful only when applied to devices
capable of performing the requested action, explanation of the control function is deferred to the sections on individual
device characteristics. It is sufficient to say that, if a control function is requested of a device incapable of respond-
ing, the request is ignored.
If Bit 0 of the function byte is reset (Bit 0=0), the system infers that the program is requesting a data transfer. The en-
coded value of Bits 1 through 6 of the function byte indicates the type of transfer (read or write), and the modifying options
selected by the program, Setting Bit 1 of the function byte indicates a Read operation. Setting Bit 2, a Write operation.
Bits 3 through 5 indicate the optional modifiers chosen. Bits 6 and 7 are not used, and should always be zero. The op-
tional modifiers offered are: ASCH or binary, wait or proceed, and random or sequential. The following list shows the
various operations and options together with their binary and hexadecimal values.
OPERATION/OPTION BINARY HEXADECIMAL
Read 0100 0000 Х'40'
Write 0010 0000 Х'20'
Binary 0001 0000 X'10'
ASCII 0000 0000 X'00'
Wait 0000 1000 X'08'
Proceed 0000 0000 X'00'
Random 0000 0100 Х'04'
Sequential 0000 0000 X'00'
In the binary and hexadecimal values already given, it is assumed that all bits in the function code other than the one
that identifies the operation or option are zero. This was done to show the cumulative nature of these values. A coding
example best illustrates this:
READ EQU X'4000'
BINARY EQU X'1000'
WAIT EQU X'0800'
LU EQU X'0003'
SVC 1, PARBIK 1/0 SUPERVISOR CALL
PARBLK DC READ+BINARY+WAIT+LU FUNCTION CODE AND LOGICAL UNIT
The code generated by the constant defined at PARBLK would be equal to X'4000' + X'1000' + X'0800' + X'0003' or X'5803
The binary representation of this constant is 0101 1000 0000 0011, in which Bits 1, 3 and 4 of the function code are set
to indicate read binary and wait. The value of three in the low order byte indicates that the operation is to be performed
on the device associated with logical unit 3.
The significance of the ASCII or binary and random or sequential options is covered in the discussions on the individual
devices for which they are significant. The wait or proceed option pertains to all devices, and their interpretations are
as follows. I/O and wait causes the user program to go into the I/O wait state until the data transfer is complete or
terminated for some reason. I/O and proceed causes the program to wait until the transfer can be started, but then al-
lows the task to continue execution while the transfer is going on. The following programming examples show how these
options may be used.
If the program specifies a function code of zero, the system returns illegal function status. If the program specifies
both read and write, read is assumed, and the callers Condition Code is set to zero.
3.3.1 Examples of Data Transfers
As shown in Figure 3-1, Read and Write operations require at least three, and possibly four, additional halfwords in the
parameter block of the Supervisor Call instruction. For example:
SVC 1, PARBLK 1/0 SUPERVISOR CALL
PARBLK DC X'xxxx" FUNCTION CODE AND LOGICAL UNIT
DC Х'хххх' STATUS AND DEVICE NUMBER
DC A(START) ADDRESS OF FIRST DATA BYTE
DC A(END) ADDRESS OF LAST DATA BYTE
DC RANDOM RANDOM ACCESS ADDRESS
START DS N DATA BUFFER
END EQU *-1 ADDRESS OF LAST BYTE
3-4
SVC 1, A(X2)
0 78 1112 1516 31
El X2 A
0 15
A+(X2) —e| FUNCTION CODE L.U.
STATUS DEV. ADDR
A (START)
A (END)
RANDOM ACCESS ADDRESS
0 READ | WRITE | BINARY | WAIT | RANDOM 0
FUNCTION CODE
OPERATION BINARY HEX
WRITE ASCII AND PROCEED 0010 0000 | 20
WRITE RANDOM AND PROCEED | 0010 0100] 24
WRITE ASCII AND WAIT 0010 1000] 28
WRITE RANDOM AND WAIT 0010 1100] 2c
WRITE BINARY AND PROCEED | 0011 0000] 30
WRITE BINARY AND WAIT 0011 1000| 38
READ ASCII AND PROCEED 0100 0000| 40
READ RANDOM AND PROCEED | 0100 0100| 44
READ ASCII AND WAIT 0100 1000| 48
READ RANDOM AND WAIT 0100 1100] 4C
READ BINARY AND PROCEED | 0101 0000] 50
READ BINARY AND WAIT 0101 1000] 56
Figure 3-1. Data Transfer Operations
The operating system uses the first byte of the 'STATUS AND DEVICE ADDRESS' halfword to return ending status to
the user upon completion of the I/O operation. If the system is able to complete the transfer as requested, it stores a
value of zero in this byte (and in the byte immediately following). If anything is wrong with the device before the trans-
fer, or if anything goes wrong during the transfer, the system stores a negative value (Bit 0=1) in this byte. In addition,
it stores the physical address of the device in the byte immediately following. With these items of information, the pro-
gram can analyze the error condition and issue an intelligent message to the operator, who would more readily recog-
nize a physical address rather than a logical unit number.
following conditions.
CONDITION
LINARY
on (0) MI
Device Unavailable 1010 0000
E M 1001 0000
e ETror 0100
The status returned to the program indicates any one of the
TCM
Cr
Х'А0'
X'90'
X'88!
LU
In general, if End of Medium, End of File, or Unrecoverable Error is indicated, then some data may have been trans-
ferred. If Illegal Function is indicated, then no data has been transferred. If Device Unavailable is indicated, and if
no other bits are set, then again, no data has been transferred. Specific interpretations of these conditions, as they
apply to various devices, are discussed in the following sections on individual device characteristics.
The third and fourth halfwords of the I/O parameter block specify the starting and ending addresses of the user's buffer
area.
The "RANDOM ACCESS ADDRESS" pertains only to disc and is discussed in the section on individual device character-
istics.
3-5
The following examples illustrate the general programming techniques for handling data transfers. The first example
uses I/O and wait.
SVC 1, PARBLK 1/0 SUPERVISOR CALL
LH RO, STAT GET STATUS IN GENERAL REGISTER ZERO
BM ERROR BRANCH IF NEGATIVE TO ERROR ROUTINE
PARBLK DC X'4806' FUNCTION CODE AND LOGICAL UNIT
* CALLS FOR READ ASCII AND WAIT ON LOGICAL UNIT SIX
STAT DS 2 RESERVED FOR STATUS AND DEVICE NUMBER
DC A(START) STARTING ADDRESS OF BUFFER
DC A(END) ENDING ADDRESS OF BUFFER
START DS N START OF BUFFER, LENGTH =N
END EQU * 1 FINAL BUFFER ADDRESS
In this example, the program requests that the system read ASCII data into the specified buffer and suspend the task
until the transfer is complete. In general, specifying wait in an I/O call causes the program to go into the 1/0 wait
state and remain there until the data transfer is complete. There are two exceptions to this rule: if the function is
illegal, as would be the case if logical unit 6 were assigned to the line printer; or if the device is unavailable, as would
be the case if logical unit 6 were assigned to a non-existant device, or to an inoperative device. If either of these excep-
tions apply, the user program resumes execution. Thus, the coding for ERROR might look like the following:
ERROR THI R0,X'4000' TEST STATUS FOR ILLEGAL FUNCTION
BNZ ILLFUN BRANCH IF ILLEGAL
THI R0,X'2000' TEST STATUS FOR DEVICE UNAVAILABLE
BNZ DEVUNV BRANCH IF UNAVAILABLE
THI RO, Х'хххх' TEST OTHER ERROR CONDITIONS
Note that the program uses a define storage to reserve a location for the status and device address. This is acceptable
when using I/O and wait because the contents of this halfword will always be changed by the system. Upon return to the
program, it contains zero if the transfer was successful or a negative value and the device number if the transfer failed.
Another example illustrates the use of calls to read and proceed that allow processing to overlap I/O.
SVC 1, PBLK1 FIRST 1/0 SUPERVISOR CALL FIRST BUFFER
LOOP SVC 1, PBLK2 SECOND SUPERVISOR CALL SECOND BUFFER
LH RO, STAT1 CHECK STATUS OF FIRST CALL
BM ERROR BRANCH ON ERROR STATUS
BAL Rx, PROC BRANCH AND LINK TO PROCESS FIRST BUFFER
SVC 1, PBLK1 REFILL FIRST BUFFER
LH RO, STAT2 CHECK STATUS OF SECOND CALL
BM ERROR BRANCH ON ERROR STATUS
BAL Rx, PROC BRANCH AND LINK PROCESS SECOND BUFFER
B LOOP REFILL SECOND BUFFER
PBLK1 DC X'4002' READ ASCII PROCEED LOGICAL UNIT TWO
STAT1 DS 2 RESERVED LOCATION FOR STATUS AND DEVICE NUMBER
DC A(STARTI1) START OF BUFFER NUMBER ONE
DC A(END1) END OF BUFFER NUMBER ONE
PBLK2 DC X'4002' READ ASCII PROCEED LOGICAL UNIT TWO
STAT2 DS 2 RESERVED FOR STATUS AND DEVICE NUMBER
DC A(START?) START OF SECOND BUFFER
DC A(END2) END OF SECOND BUFFER
3-6
In this example, the program issues three supervisor calls that refer to two parameter blocks. All the calls request
Read ASCII and Proceed on logical unit 2. As soon as the data transfer for the first call is started, the program re-
sumes execution. At the second supervisor call, if the first transfer is still not complete, the task is put in the 1/0
wait state. When the second call can be processed, the program is again allowed to proceed. At this noint, since the
system was able to start a second transfer on logical unit 2, the program knows that the first transfer is complete. It
checks the status and processes the data.
It then issues a third call to refill the first buffer. If the second call is not complete, the program again goes into the
wait state. When the second transfer is complete, the system starts processing the third call and the program can pro-
ceed with the knowledge that the second buffer is full. It checks the status, processes the data, and loops back to re-
peat the sequence.
3.3.2 Teletype Input/Output
DOS supports all Teletypes as ASR Teletypes. If an ASR Teletype is used with the system, it is treated as two separate
devices—a keyboard printer, and a reader/punch. The system distinguishes between these two on the basis of device
assignment. Valid operations with the keyboard/printer are read, write, and wait. ASCII must always be specified on
Read and Write operations. Wait and proceed are optional.
When data is read from the keyboard, it is masked to seven bit ASCII before being stored in the user's buffer. Delete
characters are ignored. The transfer terminates when the buffer is full or when a Carriage Return is found in the data
stream. Upon termination, the system automatically outputs a Carriage Return and Line Feed to the printer. If the
transfer terminates because a Carriage Return character is found in the input stream, this character goes into the user
buffer. Typing the hash mark character (#) causes the previous characters in the input stream to be ignored. The sys-
tem outputs a Carriage Return and Line Feed, and the Read operation is restarted.
On output to the printer, data is sent to the printer until the user buffer is exhausted, or until a Carriage Return char-
acter is found in the data stream. On termination of the transfer, the system automatically transmits a Carriage Re-
turn and Line Feed.
Valid operations on the reader/punch are read, write, and wait. All options, ASCII or binary, wait or proceed are al-
lowed.
In processing a read ASCII request on the paper tape reader, the system first outputs an X-ON character. It then trans-
fers the data into the user's buffer ignoring blank tape and delete characters. Input characters are masked to seven bit
ASCII before being placed in the buffer. Tapes are read in the blocked mode so data is not printed while being read.
The transfer stops when the buffer is full or when a Carriage Return character is found in the data. Ifa Carriage Re-
turn is found, it is placed in the buffer. On termination, the system continues to advance the tape until it finds a delete
character or a blank. It then outputs an X-OFF character to stop the tape.
On a request for an ASCH write to the Teletype punch, the system first outputs a RUB OUT character, a TAPE ON char-
acter, two more RUB OUT characters, and eight frames of blank tape. This is followed by the user's buffer. The trans-
fer stops when the user's buffer is exhausted or when a Carriage Return character is found in the output stream. On
termination, the system outputs a Carriage Return character (if not already output by the user), a Line Feed character,
TAPE OFF, and RUBOUT. Printable ASCII characters output to the Teletype punch are printed at the same time the
tape is being punched.
Binary Read operations on the Teletype reader start with an X-ON character output by the system. The tape is then ad-
vanced until the first non-zero character is found. If this character is X'F0', subsequent characters punched on the tape
are read into the user's buffer until it is full. If this character is anything other than X'F0', the system assumes that
the tape is punched in non-printing ASCII. In this case, the characters are read, stripped of their zone bits, and packed
into the user's buffer. This process continues until the user's buffer is full. Invalid ASCII=zoned characters are ignored.
After the buffer is full, the tape advances to the first blank character. On both types of binary reads, if the buffer length
is shorter than the record length, overflow is lost. If the buffer length is greater than the record length, data may be
garbled. The system terminates binary Read operations by sending an X-OFF character to the reader.
3-7
For binary writes on the Teletype punch, the system first sends out a RUB OUT character, TAPE ON, two more RUB
OUT characters, and eight frames of blank leader. This is followed by the user's buffer. As it is output, the data is
converted to non-printing ASCII characters which require two frames of punched tape for each data byte. This operatio:
terminates when the end of the buffer is reached. The system then outputs TAPE OFF followed by a RUB OUT characte
Two error conditions can be returned to programs using the Teletype for 1/0. These are Device Unavailable (X'A0') ап
Illegal Operation (X'C0'). Device Unavailable is returned if the Teletype is off-line at the time of the request, or if the
Break key is depressed during the transfer. The system returns Illegal Operation status if the program attempts binar
operations on the keyboard/printer.
3.3.3 High Speed Paper Tape Reader Input
The High Speed Paper Tape Reader, operating under DOS, can accept read and wait commands. ASCII or binary, wait
or proceed are optional with Read operations.
On ASCII input, the system ignores blank tape and delete characters. The characters are masked to seven bit ASCII
before being placed in the buffer. The operation terminates when the buffer is full or if a Carriage Return character is
found in the input stream. On termination, the tape continues to advance until blank tape or a delete character is found
Overflow data is lost.
The system returns an error status of Device Unavailable (X'A0') if the reader is off-line at the time of the call. It re-
turns Illegal Operation (X'C0') if a Write operation is attempted. (Write operations are legal on combined reader/punc
devices that share the same device address.) The High Speed Paper Tape Reader ignores control commands. Refer i
Table 3-2.
3.3.4 High Speed Paper Tape Punch Output
The High Speed Paper Tape Punch accepts write and wait commands. ASCII or binary, wait or proceed, are optional.
For ASCII output, the system first sends out eight frames of blank tape as an inter-record gap. It follows this with th
contents of the buffer. The output terminates when the buffer is exhausted or if a Carriage Return is found in the data
stream. The system automatically outputs a Carriage Return and Line Feed immediately following the user's data. I
the user's buffer includes a Carriage Return character, this is sent to the punch followed by a system provided line fe
For binary output, the system sends out eight frames of blank tape followed immediately by the data from the user's t
fer in eight bit format. The operation terminates when the buffer is exhausted.
The system returns Device Unavailable status (X'A0') to the program if the device is off-line at the time of the call, «
if it goes off-line during an operation. The High Speed Paper Tape Punch ignores control commands. Refer to Table
3-2.
3.3.5 Card Reader Input
The Card Reader accepts read and wait commands. ASCII or binary, wait or proceed, are optional with read comm:
On ASCII input, the system converts each card column (12 bits) into one seven bit ASCII character. Illegal codes ge
erate an asterisk (*) character. Each read command causes a maximum of 80 characters to be stored in the user's
buffer. If the buffer is less than 80 characters in length, overflow is lost.
TABLE 3-2. LOGICAL STATUS CODES RETURNED BY DOS
DEVICE HEX. VALUE CAUSE
Teletype Keyboard/ 00 NO ERRORS or a function was ignored,
Printer co ILLEGAL FUNCTION: an incorrect function code (i.e. write binary
to the printer or read binary from the Keyboard... ).
AO DEVICE UNAVAILABLE: Break key was depressed or an off-line
condition was detected.
Teletype Reader/ 00 NO ERRORS or a function was ignored.
Punch CoO ILLEGAL FUNCTION: as described above.
AO DEVICE UNAVAILABLE: as described above.
High Speed Paper 00 NO ERRORS or a function was ignored.
Tape Reader/ co ILLEGAL FUNCTION: a write operation was attempted on a reader
Punch only system.
АО DEVICE UNAVAILABLE: an off-line condition was detected.
Card Reader 00 NO ERRORS or a function was ignored.
co ILLEGAL FUNCTION: a Write operation was specified.
Ао DEVICE UNAVAILABLE: an off-line condition was detected.
Line Printer 00 NO ERRORS or a function was ignored.
co ILLEGAL FUNCTIONS: a Read operation was specified or a write
binary operation was attempted.
AO DEVICE UNAVAILABLE: either the DU bit or the EX bit was
detected.
Magnetic Tape or 00 NO ERRORS
Cassette Tape Co ILLEGAL FUNCTION: a Write operation was specified to a write
protected device.
AO DEVICE UNAVAILABLE: an off-line condition was detected.
90 END-OF-MEDIUM: an end-of-tape or a beginning-of-tape condition
was detected.
88 END-OF-FILE: an end-of-file condition was detected. (file mark)
84 UNRECOVERABLE ERROR: a parity error was detected on a Read
or Write operation (ten retrys are attempted before this status is
returned).
Disc 00 NO ERRORS
co ILLEGAL FUNCTION: a Read or Write operation has been attempted
on a file with a read or write protect attribute, or a Write operation
has been attempted on a file with hardware write protect enabled.
AO DEVICE UNAVAILABLE: the user has attempted to use a physical file
where an off-line condition, a seek-incomplete, an overrun error or a
write check condition was detected
90 END-OF-MEDIUM: file overflow condition has occurred on a direct
physical file, or on a file where three overflow cylinders have already
been allocated, or at a time when no unused cylinders are available
for overflow allocation.
88 END-OF-FILE: an end-of-file condition was detected. (file mark)
84 UNRECOVERABLE ERROR: a parity error was detected on a read
operation (five rereads are attempted before this status is returned) or
a defective track condition has occurred.
For binary input, the system transfers twelve bits of data as read from each card column into the buffer. Two bytes of
data result from each card column, with six bits of data right justified in each byte. If the buffer is less than 160 bytes
in length, overflow data is lost.
Device Unavailable status is returned to the program if the Card Reader is off-line at the time of a read request. It is
also returned if the device malfunctions during an operation. After receipt of Device Unavailable status, the program
should notify the operator and then attempt to reread the card into the same buffer. The system returns Illegal Opera-
tion status if a program attempts to write to the card reader. The Card Reader ignores all control commands. Refer
to Table 3-2.
3.3.6 Line Printer Output
The Line Printer accepts write and wait commands. ASCII must always be specified with write commands. Wait or pro-
ceed are optional.
The system outputs the contents of the user buffer. The operation terminates when the end of the buffer is reached or if
a Carriage Return character is found in the data stream. A Line Printer is capable of printing 132 characters per line.
If the user attempts to output more, the overflow is lost. On termination, the system causes the line to be printed on
the paper and the paper to be advanced one line. Form feed and other page control characters must be contained within
the user's buffer. Refer to the appropriate line printer manual for details.
Device Unavailable status is returned to the program if the printer is off-line at the time a write request is made. Ille-
gal Operation status (X'C0') is returned if the user attempts any read or a write binary operation. Control commands
are ignored. Refer to Table 3-2,
3.3.7 Magnetic Tape Input/Output
DOS supports nine track magnetic tape using the Selector Channel for data transfers. Read, Write, and wait and control
operations are allowed. Read and Write operations may specify wait or proceed. The ASCII or binary option has no sig-
nificance and sequential operations are always assumed.
Read requests cause eight bit data to be read from the tape directly into the user's buffer. The transfer stops when the
buffer is full or when the hardware senses an end of record condition, If a parity error occurs, the system attempts to
reread the record ten times before giving up. At the end of the reread operation, the tape is positioned in the inter-rec-
ord gap following the defective record.
If the buffer length is less than the record length, a parity error condition occurs.
Write requests cause eight bit data to be written from memory to the tape. The operation terminates when the buffer
limit is reached. If the tape is positioned at the beginning of tape marker when a write request is received, the system
writes a file mark and backspaces over it before starting the Write operation. The buffer limits specified for magnetic
tape transfers must start on an even byte boundary and end on an odd byte boundary.
When working with magnetic tape, all control commands are accepted. Rewind causes the tape to be positioned at the
beginning of tape marker. Backspacing one record moves the tape backward over one record and leaves it positioned in
the previous inter-record gap. Forward spacing one record positions the tape in the next inter-record gap. Skip for-
ward to file mark causes the tape to skip as many records as necessary to get it to the next file mark. The tape is posi-
tioned in the inter-record gap just beyond the file mark. Skip backward to file mark causes the tape to move backward
until it reaches a file mark. It goes past the file mark and stops in the preceding gap.
3-10
3.3.8 Cassette Tape Input/Output
For Cassette tape, read, write, and wait and control operations are allowed. Read and Write operations may specify
wait or proceed. The ASCII or binary option has no significance and sequential operations are always assumed.
Read requests cause eight bit data to be read from the cassette directly into the user's buffer. The transfer stops when
the buffer is full or when the hardware senses an end of record condition. If the buffer length is less than the record
length, overflow data is lost. If a parity error occurs, the system attempts to reread the record five times before giv-
ing up. At the end of the reread operation, the cassette is positioned in the inter-record gap following the defective
record.
Write requests cause eight bit data to be written from memory to the cassette. The operation terminates when the buf-
fer limit is reached. If the cassette is positioned at the beginning of tape marker when a write request is received, the
system writes a file mark and backspaces over it before starting the Write operation.
When working with cassette tape, all control commands are accepted. Rewind causes the tape to be positioned at the
beginning of the tape marker. Backspacing one record moves the tape backward over one record and leaves it positioned
in the previous inter-record gap. Forward spacing one record positions the cassette in the next inter-record gap. Skip
forward to file mark causes the cassette to skip as many records as necessary to get it to the next file mark. The tape
is positioned in the inter-record gap just beyond the file mark, Skip backward to file mark causes the tape to move
backward until it reaches a file mark. It goes past the file mark and stops in the preceding gap.
3.3.9 Disc Input/Output
Each disc on the system may be divided into many named files. Individual files are treated as separate physical devices.
The operator command 'ALLOCATE' defines the limits of each file on cylinder boundaries. A protect attribute can be
set up for the file that prevents unauthorized programs from accessing the data in it. Read, Write, wait and control op-
erations are allowed. Wait or proceed and random or sequential are optional,
The parameter block for disc I/O contains a halfword for random addressing. The random access address is a logical
record number relative to the start of the file. (Logical sector number for files attributed as "DIRECT PHYSICAL'.)
Within each file, the records are numbered from zero, and the system makes the conversion to absolute disc address.
For operations specified as sequential, the random access address is ignored.
The system maintains a current logical record address for each file. On a Read or Write operation, it increments the
current address to point to the next record. This allows programs to position the current record pointer using a random
access read or write and then continue the operation sequentially. For random and sequential accesses, the transfer
length is limited to the logical record length of the file as allocated. For direct physical transfer, the record length
may be any number of sectors as specified by the starting and ending addresses in the SVC parameter block. The start-
ing sector may be specified by a random access address (Bit 5 set in the function code).
3.3.10 Control Operations
When the first bit of the function byte is set, (Bit 0=1), the function code is interpreted by the system as a device con- _
trol operation. These operations apply to disc and magnetic tape devices. Bits 1 through 6 each designate a different
operation. Bit 7 is not used and should always be zero. Valid control codes are:
BIT OPERATION BINARY HEXADECIMAL
_
1 Rewind 1100 0000 X'CO'
2 Backspace One Record 1010 0000 X'A0'
3 Forward Space One Record 1001 0000 X'90'
4 Write File Mark 1000 1000 X'88'
5 Skip Forward to File Mark 1000 0100 X'84!
6 Backspace to File Mark 1000 0010 Х'82'
3-11
The system scans the function byte from left to right. It will therefore initiate the first operation for which it finds a
bit set. All control operations have an implied proceed. That is, the program goes into I/O wait only if the device is
busy at the time the supervisor call is issued. Once the call can be processed, the program is allowed to continue.
The following example illustrates a typical control operation (see Figure 3-2):
CONTROL OPERATIONS
REWIND BACKSPACE FORWARD SPACE | WRITE FILE [SKIP FORWARD BACKSPACE
ONE RECORD ONE RECORD MARK FILE MARK FILE MARK
MAG TAPE
AND CASSETTE|[«- - HARDWARE FUNCTIONS —
The Cur- |1 is subtracted 1 is added to the [Logical Record {The current logical] Same as
rent Logi- |from the Logical] Logical Record |of X'1313' half- jrecordpointer is set] REWIND
DISC cal Record{Record Pointer Pointer words is written [to one record beyond
Pointer is the first detected
Set to 0 file mark record
OTHER
DEVICES OPERATION IGNORED >
MORE SVC 1, PBLK1 1/0 SUPERVISOR CALL
LH RO,STATI STATUS IN REGISTER ZERO
BM ERRI1 BRANCH IF BAD
LH R1, START FIRST INPUT HALFWORD IN REGISTER ONE
CLHR R1, R2 COMPARE WITH END INDICATOR
BNE MORE MORE DATA TO INPUT
SVC 1, PBLK2 CONTROL SUPERVISOR CALL
LH RO, STAT2 STATUS IN REGISTER ZERO
BM ERR2 BRANCH FOR ERROR RECOVERY
PBLK1 DC Х'4804' READ AND WAIT, LOGICAL UNIT FOUR
STAT1 DS 2 STATUS AND DEVICE ADDRESS
DC A(START) BUFFER START
DC A(END) BUFFER END
PBLK2 DC X'C004' REWIND LOGICAL UNIT FOUR
STAT2 DS 2 STATUS AND DEVICE ADDRESS
Figure 3-2.
Control Operation Example
In this example, the program is reading records from logical unit 4. When it discovers that it has read the last record,
it issues a rewind command to logical unit 4 and immediately checks the status. If the status is zero, the operation has
been started, but is not necessarily complete. Subsequent operations with logical unit 4 (read, write, or control) are
delayed until the rewind is complete.
3-12
3.4 SVC 2 - SERVICE FUNCTIONS (see Figure 3-3)
SVC 2, A(X2)
| El | 2 | х2 | A | 0 | o | o 4
| | SET STATUS
PSW STATUS cc
о 15
| о | © | ° | ! | Pause о 15
— о о о 5 |
FETCH POINTER
о о о R |
о 15
о о 2
о 5
о о R | GET STORAGE
о | о | о | 6
NUMBER OF BYTES UNPACK
A (DESTINATION)
о 15 o 15
о | о | о |: | о | о | о | т
RELEASE STORAGE MESSAGE
NUMBER OF BYTES | NUMBER OF BYTES
MESSAGE
Figure 3-3. Parameter Blocks for SVC 2 Supervisor Calls
PAUSE
A program may occasionally find that it cannot continue without operator intervention. (A typical reason is trouble with
a peripheral device.) The Pause supervisor call allows the calling task to suspend itself until the operator takes some
action. The form of this call is:
SVC 2, PARBLK PAUSE SUPERVISOR CALL
PARBLK DC X'001' FUNCTION CODE FOR PAUSE
This call causes the user program to be suspended, and the word 'PAUSE' is sent to the Console Teletype. The opera-
tor, after taking whatever action may be required, can resume execution at the instruction immediately following the
supervisor call by entering the CONTINUE command.
GET STORAGE
The purpose of the Get Storage supervisor call is to give a task a way to provide temporary storage locations for sub-
routines it calls - especially FORTRAN Run Time Library sub-routines, which since they are reentrant, require stor-
age outside themselves.
SVC 2, PARBLK GET STORAGE
PARBLK DC X'0002' GET STORAGE CODE
DC X'000x' DESIGNATED REGISTER
DC N N=NUMBER OF BYTES
3-13
The starting address of the area is loaded into the register specified by the second halfword of the parameter block,
The third halfword of the parameter block must contain the number of bytes requested. Subsequent requests obtain new
areas. In processing the Get Storage request, DOS increments UTOP, a constant initially set to the top of the user pro-
gram exclusive of Common, by the amount of storage requested. It compares the new value to COMBOT, the address
of the bottom of Common (or top of core when Common is not used), which is used in conjunction with FORTRAN pro-
grams. If the new value is greater than the limit, DOS terminates the program with the message:
IF KXXXXXXX
where xxxxxxxx is the user Program Status Word whose Location Counter points to the supervisor call that caused the
termination. Figure 3-4(A) shows the effect of a Get Storage SVC.
(A) (B)
CTOP CTOP
COMMON COMMON
COMBOT COMBOT
UTOP furor
USER STORAGE LDBIAS
LDBIAS |
USER USER
PROGRAM PROGRAM
UBOT (SUPTOP) UBOT (SUPTOP)
BOSS BOSS
CORE MAP AFTER USER CORE MAP AFTER USER
PROGRAM REQUESTS STORAGE PROGRAM RELEASES STORAGE
Figure 3-4. Core Map
RELEASE STORAGE
The inverse of the Get Storage call is the Release Storage call. It releases storage previously obtained. The order in
which it releases core is the reverse of the order in which it was obtained. That is, the last obtained is the first re-
leased. Coding for this call is:
SVC 2, PARBLK RELEASE STORAGE SVC
PARBLK DC X'0003' RELEASE STORAGE CODE
DC N N=NUMBER OF BYTES
The system releases the number of bytes specified by the second halfword of the parameter block, and makes those
locations available for future Get Storage requests. The UTOP pointer is adjusted downward by this call.
If the value obtained is less than the value of SUPTOP, DOS terminates the program with the message:
I XXXXKXXX
where xxxxxxxx is the user Program Status Word whose Location Counter points to the supervisor call that causes the
termination. Figure 3-4(B) shows the effect of a Release Storage SVC.
3-14
SET STATUS
The usual Program Status Word for application tasks is set up to allow floating point and fixed point arithmetic inter-
rupts. At times, a task may choose not to be interrupted because of division by zero, or underflow/overflow. The Set
Status supervisor call allows a task to disable and enable floating point and fixed point interrupts. The coding for this
is:
SVC 2, PARBLK SET STATUS
PARBLK DC X'0004' SET STATUS CODE
DC X'xxxx" NEW STATUS
The second halfword of the parameter block indicates how arithmetic interrupts are to be handled. The following com-
binations are allowed:
X'0000' Disable Floating Point and Fixed Point
X'1400' Enable Floating Point and Fixed Point
X'0400' Enable Floating Point, Disable Fixed Point
X'1000' Disable Floating Point, Enable fixed Point
Execution of this call also sets the program's Condition Code to the value of the last hexadecimal digit of the new status,
A variation on this call allows the user to set only the Condition Code. It has the form:
SVC 2, PARBLK SET CONDITION CODE
PARBLK DC X'8004' SET CC CODE
DC X'xxxx" NEW CONDITION CODE
In this call, the Condition Code of the Program Status Word is set equal to the last four bits of the second halfword of
the parameter block. These calls manipulate the arithmetic interrupt enable bits and the Condition Code. They cannot
be used to set or reset other bits in the Program Status Word.
FETCH POINTER
This supervisor call returns to the caller the address of a table of constants contained with DOS. It has the form:
SVC 2, PARBLK FETCH POINTER
PARBLK DC X'0005' FETCH POINTER CODE
DC X'000x' REGISTER DEFINITION
3-15
The Fetch supervisor call places in the register specified by the second halfword of the parameter block the address
of CONTAB, a table of constants in DOS. This table is summarized in Table 3-3. The table contains addresses, such
as the Top of Core, which can be used by programs to communicate with the system and control storage allocation.
PARAMETER
CTOP
COMBOT
UTOP
UBOT
LDBIAS
XFRADR
UNPAK
TABLE 3-3. CONSTANT TABLE
CONTAB + 0 CTOP TOP OF CORE
+ 2 COMBOT BOTTOM OF COMMON
+ 4 UTOP USER AREA TOP |
+ 6 UBOT USER AREA BOTTOM
+ 8 LDBIAS LOAD BIAS
+A XFRADR TRANSFER ADDRESS
MEANING
Address of the last halfword within memory. This value is the highest addressable memory location.
Address of the first halfword within Common. This value, which is the lowest address used for Com-
mon, equals CTOP if Common is not used.
Address of the first halfword following the user program and storage area. This value, which is the
lowest available address for more storage, equals LDBIAS after a program is loaded, but no storage
is allocated.
Address of the first halfword following the DOS resident system.
Address of the location to be used for loading the next relocatable program. This value which defines
the first available halfword following the last program loaded, equals UBOT when no programs have
been loaded, or after DOS initialization.
Address of execution starting point for the last program loaded. This value equals zero if the last
program loaded did not specify a starting address.
The Unpack supervisor call converts a halfword binary constant into four ASCII hexadecimal characters. The constant
to be converted must first be loaded into General Register Zero. For example:
LH R0, CONST LOAD CONSTANT IN REGISTER ZERO
SVC 2, PARBLK UNPACK SUPERVISOR CALL
PARBLK DC X'0006" UNPACK CODE
DC A(DEST) DESTINATION ADDRESS
DEST DS 4 DESTINATION
In this case, the constant loaded into General Register Zero is converted into four ASCII hexadecimal digits. These
four bytes are then stored in consecutive locations starting at the address designated by the second halfword of the para-
meter block.
3-16
LOG MESSAGE
The Log Message supervisor call outputs a string of ASCII characters to the console device. The second halfword of the
parameter block contains the number of characters, followed immediately by the message. This supervisor call should
be used to output I/O error messages and operator instructions since the message always goes to the console device.
The following example of the use of the Log Message supervisor call illustrates a typical way of using several super-
visor calls already described.
SVC 1, PBLK1 1/0 SUPERVISOR CALL
LH R0, STATI GET STATUS AND DEVICE NUMBER IN RO
BM ERROR BRANCH ON ERROR
ERROR SVC 2, PBLK2 UNPACK CONTENTS OF REGISTER ZERO
SVC 2, PBLK3 LOG MESSAGE
SVC 2, PBLK4 PAUSE
B CONTIN RESUME EXECUTION AFTER PAUSE
PBLK1 DC X'4008! READ FROM LOGICAL UNIT 8
STAT1 DS 2 STATUS AND DEVICE NUMBER
DC A(START) STARTING ADDRESS OF BUFFER
DC END ENDING ADDRESS OF BUFFER
PBLK2 DC X'0006' UNPACK CODE
DC A(DEST) DESTINATION
PBLK3 DC X'0007' LOG MESSAGE CODE
DC 14 LENGTH OF MESSAGE
DC C'1/0 ERROR! MESSAGE TEXT
DEST DS 4 DESTINATION FOR UNPACK
PBLK4 DS X'0001' PAUSE
The parameter block for the Log Message supervisor call 'PBLK3' in the example, contains the function code, X'0007',
the number of characters in the message text, in the example (14), followed immediately by the text itself. Note that in
the example, the destination for the Unpack supervisor call follows the message text. The message produced by this
particular sequence of coding would be:
1/0 ERROR XXXX
where XXXX is the unpacked contents of General Register Zero; i.e., the logical status and physical device address
returned to the program after an unsuccessful Read operation. This message would be followed by:
PAUSE
indicating that the program has suspended itself.
3-17
3.5 SVC 3 - END OF JOB
The End of Job supervisor call allows a program to terminate itself in an orderly manner. It is, following the program
logic, the last executable instruction. This call has the form:
SVC 3,0
Note that there is no parameter block associated with this call. If the program issuing this call has I/O in progress at
the time the call is made, the 1/0 is allowed to go to completion.
The End of Job SVC also causes all activated disc files to be closed. (see CLOSE command).
3-18
3.6 SVC 4 - EXECUTE COMMAND STATEMENT
This supervisor call allows the user to perform operator commands from within a running program.
The address field of the SVC 4 instruction points to an operator command statement in memory. Commands processed
by SVC 4 are of the same format as those input by an operator. Commands are represented internally in 7-bit ASCII
and must be terminated by either a blank (X'20') or a Carriage Return (X'0D'). If any errors are detected during the
processing of a command, the incorrect command and an error message is logged on the Console Teletype and DOS re-
tains control in the Command mode. The user may reenter the command and then enter CONTINUE to resume his pro-
gram.
Example:
SVC 4, PARBLK EXECUTE OPERATOR COMMAND
PARBLK DC C'AC OBJECT, 2' ACTIVATE A DISC FILE
While executing a SVC 4 the following conditions cause unconditional return to DOS command mode:
1. Execution of a TRANSFER command,
2. Execution of a SVC 2 PAUSE.
3-19
3.7 SVC 5 - FETCH OVERLAY
Any user program may be segmented into a trunk, or root section that resides in memory and any number of subrou-
tines, or overlays, that are brought into memory as required. This feature is especially useful in FORTRAN appli-
cations. (See Chapter 4 for application examples.) Overlays are loaded at a location above the root section. Overlays
can reference blank and labeled Common, and can reference routines in the reentrant library. Communication between
the root phase and overlays is through EXTRN and ENTRY statements. The following example illustrates the use of the
Fetch Overlay supervisor call:
SVC 5, PARBLK FETCH OVERLAY CALL
BAL RTN, OVERL1 BRANCH AND LINK TO OVERLAY
PARBLK DC C'OVERL1' SIX CHARACTER OVERLAY NAME
STAT DC X'0000' STATUS AND OPTIONS
DC X'0004' LOAD FROM LOGICAL UNIT 4
When this supervisor call is processed, the named overlay is brought into memory. The calling program must wait
until the overlay is loaded.
The device assigned to specified logical unit may be any sequential input device or file capable of binary read operations.
The complete overlay must be available on the device specified, (i.e., no check of the overlay name is performed).
A status of zero is always returned if control is returned to the caller. If an error occurs while the overlay is being
loaded, an appropriate error message is logged on the Console Teletype, and DOS returns to the command mode. The
following are the possible error messages that may occur (see Chapter 2 for detailed explanation). No recovery is al-
lowed from these conditions during overlay operations. The user should restart his program:
LD ERR
SEQ ERR
CKSM ERR
MEM FULL
1/0 ERR XXXX
3-20
3.8 SVC 6 - CALL A PROGRAM
This supervisor call allows application programs to exercise considerable control over the system by calling other pro-
grams.
The parameter block for the SVC is:
0 15
LU
BIAS
where LU is the logical unit of the device from which the program is loaded, LU must have been previously assigned to
a physical unit. For relocatable programs, the second halfword of the parameter block is the BIAS at which the program
is loaded. I the BIAS is zero, then the program is loaded at SUPTOP. Control is passed to the loaded program at the
BIAS specified in the parameter block. However, if the loaded program contained a transfer address, then control is
passed to this point. Absolute programs are loaded at their origin address.
If errors occur while the program is being loaded, the appropriate error message is logged on the Console Teletype,
and DOS returns control to the Command mode.
The following are the possible error messages that may occur. (See Chapter 2 for detailed explanation.)
LD ERR
SEQ ERR
CKSM ERR
MEM FULL
I/0 ERR XXXX
Example:
SVC 4, ASSIGN ASSIGN A FILE
SVC 6, PARBLK CALL A PROGRAM
ASSIGN DC C'AC OBJECT, 3'
PARBLK DC X 10003 LOAD FROM LOGICAL UNIT 3
DC х'0000' LOAD AT SUPTOP
3-21/3-22
CHAPTER 4
SYSTEM USAGE
4.1 INTRODUCTION
Efficient use of the system requires that the user take full advantage of the features inherent in DOS. This chapter pro-
vides the user with a look at various applications under DOS and thus familiarizes him with job control techniques.
4.2 MEMORY USAGE AND REQUIREMENTS
The actual size of DOS may vary from about 4KB to a maximum of 10KB depending upon the features included by the user
in his System Generation procedure. DOS may be system generated as a non-disc system, similar to the INTERDATA
Basic Operating System (BOSS/4A). Tor a full disc system the following memory is required for use of the major INTER-
DATA system software:
OS LIBRARY LOADER 16KB
OS ASSEMBLER 16KB
FORTRAN COMPILER 24KB
NOTE
To operate the OS Assembler on a 16KB system
it is necessary to overlay various utility routines
in DOS by setting the loader BIAS to location
LOKUP (see DOS listing) before loading the As-
sembler.
4-1
4,3 SYSTEM USAGE EXAMPLES
4.3.1 Establishing a Program on Disc
The following example demontrates how the user may establish a program on a disc file for convenient access. To place
the INTERDATA OS Assembler object tape on disc, Allocate a file on pack C6 as follows:
"AL ASMBLR, 1C6
Note that at the same time file ASMBLR is assigned to logical unit 1.
Assign logical unit 2 to the Paper Tape Reader:
*AS 213
With the COPY command, establish the Assembler on disc:
*CP 2,1,0
To conserve disc space, two or more programs may be placed on a single disc file, and may be searched for sequentially
and loaded by the OS Library Loader, or positioned via the Position command and loaded by the DOS loader.
4.3.2 Assemblies with Disc Scratch
Allocate a disc scratch file if one does not already exist.
*AL SCRT, C6, 20,80
Twenty cylinders are enough for a source deck of about 3000 cards. Assume the object program will he written to a disc
file called OBJECT, The following commands initiate the assembly,
*AS 104, 362 ASSIGN THE SOURCE INPUT AND LIST DEVICES TO THE CARD
READER AND LINE PRINTER RESPECTIVELY
*AC SCRT,4 ASSIGN THE SCRATCH DEVICE TO FILE SCRT
*AC OBJECT,2 ASSIGN THE BINARY OUTPUT DEVICE TO FILE OBJECT
*RU ASMBLR EXECUTE THE ASSEMBLER
NOTE
The Assembly OPTION card must have the SCRT
option specified.
4.3.3 FORTRAN Compile and Go
Assume the FORTRAN compiler, the OS Library Loader, and the FORTRAN Run Time Library have been established
on disc files FORTRN, LIBLDR and RUNTME respectively. The user wishes to compile and execute a FORTRAN source
program on cards. The FORTRAN program itself reads card input from logical unit 1, outputs object code on logical
unit 2, and prints output on logical unit 3.
*AS 104, 362 ASSIGN THE COMPILER SOURCE INPUT AND LIST DEVICE TO
THE CARD READER AND LINE PRINTER RESPECTIVELY
*AC OBJECT, 2 ASSIGN THE BINARY OUTPUT DEVICE TO DISC FILE OBJECT
*RU FORTRN EXECUTE THE FORTRAN COMPILER
*AC RUNTME, 6 ASSIGN THE RUN TIME LIBRARY
*RU LIBLDR EXECUTE THE LIBRARY LOADER
The following are commands to the OS Library Loader.
RE 2 REWIND LOGICAL UNIT 2
LO 2 LOAD FORTRAN OBJECT PROGRAM
ED 6 EDIT WITH THE RUN TIME LIBRARY
GO EXECUTE THE FORTRAN PROGRAM
4.3.4 Cataloging and Batch Operations
Using the previous example to demonstrate disc cataloging and a batch operation, allocate a disc file called JOBFTN to
hold the operator commands of the previous example.
*AL JOBFTN, C6, 1,80
Making the proper device assignments enables the cataloging of commands on file JOBFTN by the COPY command.
*AS 202 ASSIGN LOGICAL UNIT 2 TO THE TELETYPE
*AC JOBFTN, 5 ASSIGN JOBF TN TO LOGICAL UNIT 5
*CP 2,5,80 TYPE OUR COMMANDS ONTO THE DISC
The COPY function may be terminated by typing VEND.
To execute the job, transfer command input control to file JOBF TN, Note that JOBFTN is assigned to logical unit 5.
This is necessary because the OS Library Loader, which also reads commands in this job stream, always reads com-
mand input from logical unit 5.
*AC JOBFTN, 5
*TR 5 EXECUTE CATALOGUED JOB STREAM
4.4 OVERLAYS \
The subject of overlays is an important one for system planning. The use of overlays can substantially reduce the mem-
ory requirements for a system. There is no limit to the number of overlays a program may have.
Overlays should not call other overlays. They should always return to the root segment (main program) and allow it to
call the next overlay. If an overlay calls another overlay, the new overlay is loaded on top of (overlays) the first, and
program execution resumes from the location immediately following the Supervisor Call instruction in the first overlay.
This would not likely be the starting location for the new overlay.
Overlays and root segments can communicate with EXTRN and ENTRY statements. Overlays can reference subroutines
that are loaded with them or loaded with the main program. Overlays can reference both blank and labeled Common.
Overlays can be very helpful in conserving memory space. However, this saving is achieved by sacrificing time. Even
when disc is used as the system library, it takes time to load an overlay. For this reason, overlays should be used for
processing that is not time critical.
A feature has been added to OS Library Loader 03-030 to enable the establishing of overlays. This feature is described
in the Loader Descriptions Manual, Publication Number 29-231. It consists of a single command (OV), which informs
the Library Loader that the subroutine about to be linked is an overlay subroutine. It is this command that origins the
overlay subroutines such that they occupy a common area of memory. Overlays are established by using the OUT fea-
ture of the Library Loader. Established overlays are in absolute form.
As an example of overlay establishing procedures, assume a FORTRAN application program and two subroutines which
are to be linked as overlays. The program and its subroutines have been compiled and their object programs are on
paper tape. The main program calls the first overlay via logical unit 2 and the second via logical unit 3 using the IFETC
routine in the Run-Time Library. We begin by allocating disc files for the main program and the overlay subroutines,
and assigning them to logical units 1, 2 and 3, respectively.
*AL MAINP, 1C6
*AL OVERI1,2C6
*AL OVER2,3C6
*AC RUNTME, 6 ASSIGN THE RUN TIME LIBRARY
*AS 413 ASSIGN THE PAPER TAPE READER
*RU 1lLIBLDR EXECUTE THE LIBRARY LOADER
The following commands are read by the Library Loader.
OUT 1 SET THE OUT OPTION FOR LOGICAL UNIT 1
LO 4 LOAD THE MAIN PROGRAM
ED 6 EDIT WITH THE RUN TIME LIBRARY
XOUT
OV INDICATE AN OVERLAY TO BE LINKED
OUT 2 SET THE OUT OPTION FOR LOGICAL UNIT 2
LI 4 LINK FIRST OVERLAY
ED 6 EDIT WITH THE RUN TIME LIBRARY
XOUT
OV INDICATE ANOTHER OVERLAY IS TO BE LINKED
OUT 3 SET THE OUT OPTION FOR LOGICAL UNIT 3
LI 4 LINK SECOND OVERLAY
ED 6 EDIT WITH THE RUN TIME LIBRARY
XOUT TERMINATE OUT OPTION
EN TERMINATE LIBRARY LOADER
4-4
The main program and its overlays have been established and may be executed from disc by the following sequence of
commands.
*AC OVER], 2
*AC OVER2,3
*RU MAINP
NOTE
If an overlay is to be loaded more than once by a main
program, the overlay logical unit should be rewound by
the main program prior to loading the overlay (i.e., in
FORTRAN by a Call to subroutine REW),
4.5 DISC FILE USE
To demonstrate the use of sequential, random and direct physical access, the following sample problem is presented.
File A, which has been previously allocated by:
*AL FILEA, C6,1,10
is a sequential file that contains 200 10-byte records followed by a file mark. The first halfword of each record contains
a unique binary number from 0 to 199. We wish to copy File A to another file sorting by this binary number.
Allocate File B as follows:
*AI, FILEB,C6,1,10
and make FILEB random by:
*AT FILEB, 0010
Activate the files:
*AC FILEA,1
*AC FILEB, 2
The following sample program shows a procedure for writing File A to File B.
START SVC 1, READA READ FILE-A SEQUENTIAL
LH R0, READA+2 GET STATUS
BZS GOWRIT NO ERRORS IF 0
THI R0,X'100' CHECK FOR EOF
BNZ DONE YES, DONE
B ERROR NO, 1/0 ERROR
GOWRIT LH R0, BUFFER GET BINARY NUMBER (FIRST HALFWORD OF RECORD)
STH R0, RANADR MOVE TO RANDOM ADDRESS POINTER OF WRITE SVC
SVC 1, WRITEB WRITE FILE-B RANDOM
LH RO, WRITEB+2 CHECK STATUS
BM ERROR 1/0 ERROR IF MINUS
B START LOOP
READA DC X'4801" READ, WAIT, LOGICAL UNIT 1
DC 0 STATUS
DC BUFFER
DC BUFFER+9
WRITEB DC Х'2С02' WRITE, WAIT, RANDOM, LOGICAL UNIT 2
DC 0 STATUS
DC BUFFER
DC BUFFER+9
RANADR DC 0 RANDOM ADDRESS
BUFFER DS 10
Now that File B has been created, let us read the entire FILEB (2000 bytes) into memory at location TABLE with one
Read operation using the direct physical access method,
*AT
FILEB, 0020
The following code performs the desired read:
SVC
READB DC
DC
DC
DC
TABLE DS
1,READB
X'48 02"
0
TABLE
TABLE+1999
2000
Change the File B attribute to denote direct physical access.
READ, WAIT, LOGICAL UNIT 2
NOTE
Other access methods such as an index-sequential access
method may be implemented under DOS with the use of user
written subroutines.
These subroutines, upon receiving
control information (record keys, etc.) could perform the
actual SVC 1 1/0 calls to DOS,
4.6 PERFORMANCE TIMES
4.6.1 Sequential Disc File Timing Chart
This chart gives examples of the number of physical disc accesses required for transferring 1000 logical records.
PHYSICAL RECORD LENGTH
>
© 40
7
=]
a 80
C
О 10
O
=
150
E 5
<<
O 256
©
©
A 512
4.6.2 Useful Time Estimates (Model 70)
256 512 768 1024
167 184 53 40
334 1167 1112 184
500 1250 1143 1112
1000 | 334 [200 [167
10001500 | 334 {250
—— 11000 11000 1500
1/0 Driver Interrupt disable overhead time | 116 microseconds
Pack Initialize time
11. 5 seconds
Read time for 100 108 byte logical records
(256 byte physical record length)
2.5 seconds
Examples: An overlay consisting of 100 loader format records will take approximately three seconds to load from a
disc file.
To POSITN to the 100th record of an 80 byte record disc file will take approximately two seconds.
4-7/4-8
CHAPTER 5
DOS SYSTEM GENERATION AND MODIFICATION
5.1 SYSTEM GENERATION
5.1.1 Introduction
To provide the user with the flexibility of configuring DOS to conform to individual system requirements, a System Gen-
eration (SYSGEN) capability has been included. The user is provided with a complete object tape of DOS that includes all
DOS options, and DOS source paper tapes. DOS System Generation is accomplished by assembling the source version of
DOS with the appropriate control statements described in the following paragraphs. The user, by proper usage of these
control statements, may include or delete modules of DOS during the assembly process.
DOS is designed to have a modular command and I/O structure. Because of this, all drivers with the exception of the
TTY driver, and certain system commands, may be deleted, In addition, the number of available logical units or files
may be selected by the user. A facility is also provided for the addition of up to two special user-written drivers. (See
Section 5. 1.4.)
Addition or deletion of drivers to DOS during the assembly process are made via control instructions. An assembly IF
statement surrounds each module. The user must define, via EQU statements, the conditional variables for each module,
The SYSGEN statements are detailed in Table 5-1. The approximate size of modules within DOS is shown in Appendix 1.
5.1.2 Conditional Assembly Procedure using the Teletype to input SYSGEN Statements
1. Load a DOS or BOSS object tape, with either the GENERAL or RELOCATING loader.
2. Load OS ASSEMBLER with the DOS or BOSS resident loader.
3. Make the desired device assignments (LU1 should be assigned to the Teletype).
4. Start the ASSEMBLER,
5. Type in an OPTION statement followed by the SYSGEN statements as described in Table 5.1, Note that the
SQCHK option should not be specified. For example:
OPT PASS?
SYSTTY EQU 2
PRINT EQU X62!
etc.
All SYSGEN control statements must be included or "undefined symbol" errors result during the assembly,
If new drivers are to be added, see Section 5.1.4.
6. After all control statements have been entered, the user types:
BPAUSE
Control is now passed to DOS where the user must now assiígn LU1 to the paper tape reader or TTY reader,
mount the DOS source paper tape, and type CONTINUE,
7. The ASSEMBLY process continues, Since the DOS source consists of five separate paper tapes, a PAUSE
statement ends each tape, so that the user may mount the next tape. The user types CONTINUE to resume
the assembly process. On Pass 2 (or Pass 3) of the assembly, the SYSGEN control information need not be
reentered.
5-1
TABLE 5-1, SYSTEM GENERATION STATEMENTS
SYSGEN STATEMENTS:
SYSTTY
HSPTR
CARD
PRINT
PRINT2
MAG1
MAG2
MAG3
MAG4
CAS1
CAS2
CAS3
CAS4
DSKCTL
SELCH
DSC1
DSC2
DSC3
DSC4
TTY2
SPENT1 |
SPENT2
COPY
NUMLGU
PHSRCL
NUMCYL
NUMSEC
MOD74
MOD50
Equate to System Teletype device address (normally X'02'); do not exclude.
Equate to High Speed Paper Tape Reader/Punch device address (normally X'13'); equate to 0 to exclude.
Equate to Card Reader device address (normally X'04'); equate to 0 to exclude,
Equate to Line Printer device address (normally X'62'); equate to 0 to exclude.
Same as above; used if a second line printer is on the system.
Equate to Magnetic Tape #1 device address (normally X'85'); equate to 0 to exclude,
Same as above; used if more than one magnetic tape is on the system.
Equate to Cassette Tape #1 device address (normally X'45'); equate to 0 to exclude,
Same as above; used if more than one cassette tape is on the system.
Equate to Disc Controller device address (normally X'B6'); equate to 0 to exclude,
Equate to Selector Channel device address (normally X'F0'); equate to 0 to exclude.
Equate to disc file #1 device address (normally X'C6'); equate to 0 to exclude.
Same as above; used if more than one disc file is on the system.
Equate to TTY device address if more than one TTY is on the system. Equate to 0 to exclude.
Equate to device address of special device; used for adding special drivers to system; equate to 0 if no
special drivers are to be added.
Equate to 1 to include the COPY utility in DOS; equate to 0 to exclude.
Equate to maximum number of logical units allowed in system (must be from 1 to 16).
Equate to the desired physical record in size for DOS logical disc 1/0 operations (must be 256, 512,
768, or 1, 024). For systems with sequential processing applications a large physical record size is
desirable. For random processing a small physical record size is more time efficient.
Equate to the number of cylinders available on a disc file (must be 200 or 400 cylinders).
Equate to the number of sectors per cylinder on disc (must be 0 for 48 sectors/cylinder, or 1 for 96
sectors /cylinder).
Equate to 1 if the Processor is an INTERDATA Model 74, otherwise equate to 0.
Equate to X'400' if the Processor in an INTERDATA Model 50, otherwise equate to 0.
5.1.3 Conditional Assembly using Tape or Cards to input SYSGEN Statements
1. Prepare the SYSGEN tape or deck. This tape or deck must begin with an OPTION statement and end with a
PAUSE statement. The SQCHK option should not be specified.
2. Load DOS or BOSS with the RELOCATING or GENERAL Loader.
3. Load the OS ASSEMBLER. Make the desired device assignments. LU1 should be assigned to the device
used to input the SYSGEN tape or deck.
4, Start the ASSEMBLER.
5. When the SYSGEN tape or deck has been processed, a PAUSE message is printed. The user should now
mount the DOS source tape, reassign LU1 if necessary, and type CONTINUE,
5.1.4 Assembly Procedures to Add New Drivers
1, Follow procedures in Section 5. 1.2, Steps 1-7, entering the SYSGEN statements as described in Table 5-1,
including the additional optional device number SPENT1 (and SPENT?2 if two drivers are being added).
2. At the end of the last DOS source tape, there is an additional pause prior to the END statement on the source
tape. At this pause, the user should place his driver source module(s) into the Assembler source input de-
vice and type CONTINUE to resume the assembly process.
The following rules for user driver source must be observed:
— The entry point for driver module 1 must be or be equated to ENTRY].
— The entry point for driver module 2 must be or be equated to ENTRY2.
— The user's source must end with the source statements
SUPTOP EQU *
END SYSGO
On second and third passes, SYSGEN EQU information need not be reentered but the user's source and END statement
must be re-read in second and third passes.
5-3
5.1.5 Sample DOS System Generation
Configuration:
Model 70
One Disc Controller with 1 Disc File
Card Reader
Teletype
Line Printer
Paper Tape Reader/Punch
Two Magnetic Tape Drives
SYSGEN Control Statements
SYSTTY
HSPTR
DSKCTL
NUMLGU
CARD
PRINT
PRINT2
МАС:
МАС2
МАСЗ
MAG4
CAS1
CAS2
CAS3
CAS4
TTY2
SPENTI
SPENT2
PHSRCL
NUMCYL
NUMSEC
OPT PASS2
EQU 2
EQU X'13'
EQU X'B6'
EQU 8
EQU 4
EQU X'62'
EQU 0
EQU X's5'
EQU X'95'
EQU 0
EQU 0
EQU 0
EQU 0
EQU 0
EQU 0
EQU 0
EQU 0
EQU 0
EQU 256
EQU 200
EQU 0
Console Teletype is device 2.
Paper tape reader/punch is device X'13',
Disc controller is device X'B6',
Eight logical units selected.
Card reader is device 4,
Line printer is device X'62'.
No second printer.
Magnetic Tape #1 is device X'85'.
Magnetic Tape #2 is device X'95'.
Only two magnetic tapes.
No cassettes.
No second Teletype.
No user drivers.
Disc physical record length is 256.
Number of cylinders per disc is 200.
Number of sectors per cylinder is 48.
SYSGEN Control Statements (continued)
MOD74 EQU 0 Processor not a Model 74.
MOD50 EQU 0 Processor not a Model 50,
SELCH EQU X'FO0!
COPY EQU 1
DSC1 EQU X'C6' One disc file.
DSC2 EQU 0
DSC3 EQU 0
DSC4 EQU 0
5.1.6 Adding User Written Drivers
Drivers for non-standard devices may be readily included in a DOS system providing these drivers are written to con-
form with the procedures used in the writing of standard drivers. Standard drivers are designed in such a way as to
minimize the period of time during which the external interrupt line must be disabled. DOS drivers consist of at least
two, and sometimes three, distinct parts. The first part, required in all drivers, is the initialize routine. In operation,
this part of the driver becomes a subroutine of the Executive, which runs with external interrupts enabled. The initialize
routine interprets the function code, checks buffer limits, and in general, performs any preliminary function that can be
done with interrupts enabled. The second part of the driver is the interrupt service routine, This is an independent rou-
tine, although it is assembled along with other parts of the driver. The third part which, depending on the type of device
and the needs of the user, may not be required, is the termination routine, Like the initialize routine, this becomes a
subroutine of the executive, It performs such functions as error identification, movement of data, code conversion, and
interpretation of final device status.
The user written driver routines can be added to the system, provided they use the same linkage conventions as INTER-
DATA supplied drivers. The DOS listing supplies several examples of driver programming. The user should refer to
the DOS drivers for examples of driver linkage logic. All driver programs must be entered through the supervisor.
The general flow is as follows (see Figure 5-1): (Refer to Figure 5-2 for detailed I/O logic flow.)
1. The user program issues a supervisor call for 1/0.
2. The supervisor saves the user registers, establishes the logical to physical relationship, loads the driver
registers with pertinent information from the Device Control Block (DCB) and branches to the driver. Ex-
ternal Interrupts are enabled upon initial entry to the driver.
3. The driver does any initial processing and verification necessary, and performs a BALR DVR, INTRET which
returns to the user program,
4, The driver now regains control (via the SINT instruction executed in subroutine SVCRET) with interrupts dis-
abled, The user may now activate his device and perform other BALR DVR, INTRET to await device inter-
rupts. (To exit from all resulting device interrupts, execute a BALR DVR, INTRET.)
5. When all device interrupts have been processed, the user performs the instruction ATL SPTR, LIOTRM (caus-
ing a queue termination interrupt) and exits via another BALR DVR, INTRET.,
6. The driver now regains control via the queue termination interrupt, with interrupts enabled. The user may
now do any termination processing, and make a final exit with the instruction BR UBSY.
As an example of driver logic, we will examine the card reader driver in a step by step manner. Refer to the DOS list-
ing to follow the logic.
9-5
A SVC read causes entry to the driver, with external interrupts enabled, at location CRDVR. After checking for Illegal
commands and bad device status, the driver executes a BALR DVR, INTRET which returns to the calling program. While
returning from the SVC, the executive executes a SINT 0(DEV) which causes an external interrupt and a return to the
driver at the instruction following BALR. With interrupts now disabled, the driver adjusts FBA, if necessary, and feeds
a card. DVR is now loaded to point to a routine called SENSE which checks the device status on every card column inter-
rupt. The driver branches to SENSE via BALR RTN, DVR. SENSE exits to the user via BTCR 8,INTRET if busy is high
(a column not available for reading). When a card column is ready for reading, an interrupt occurs, and control is passed
to SENSE (contents of DVR). Since busy is now low, SENSE executes BR RTN which, in turn, returns us to the RHR in-
struction in the card reader driver. After reading the column, code conversion is performed and the resulting byte is
stored in the user buffer (routine HTAXIT). The BXLE CBA, INTRTN instruction returns to wait for another column in-
terrupt if all requested columns have not been processed. If all columns have been read, it loads DVR to force a loop
waiting for EOM status. If no EOM status is sensed, the BFCR 2,INTRET exits to wait for another interrupt. I EOM
status is sensed, the driver performs an ATL SPTR, LIOTRM (subroutine HSRPDN) instruction which places the contents
of SPTR in a list and causes a queue termination interrupt. A BALR DVR,INTRET returns from the previous external
interrupt (EOM), and we return immediately following the BALR DVR, INTRET as a result of the queue termination in-
terrupt. At this time, external interrupts are enabled, and we may perform any desired termination processing. In this
case, there is none, so the driver completes the process with BR UBSY which frees the device for subsequent calls.
Each device driver requires a Device Control Block (DCB). The device control block is used to save the driver regis-
ters, and control entry to the driver from external interrupts. When user drivers are added to the system using SYS-
GEN statements SPENT1 and SPENT2, a DCB is automatically created for the user. All DCB's are of the form:
DCB DC 0,0, 0,0,0, 1,0, DEVISP, DEV, DEVBSY, UBSY1, 0,0, 0, 0,0
DEVISP DC 0,0,0 External interrupt PSW save area
STM 0, RSAVE Save user registers
LM 0,*-42 Load driver registers
BR DVR Go to driver
DEVISP is pointed to by the Interrupt Service Table (location X'D0'). The following is a breakdown of driver registers
and their uses.
CONSTANT
REG SYMBOLIC CONTENTS MEANING
0 DVR Driver re-entry address whenever a driver is exited; DVR should
be pointing to the return location.
1 INTRET SVCRET or INTRTN Address of the SVC return routine (first entry to driver) or the
external interrupt return routine (subsequent entries).
2 AX2 Pointer to the SYC parameter block.
3 FCN Contents of first halfword of SVC parameter block (function code
and logical unit).
4 CBA User buffer start address,
5 ONE 1 Constant of 1.
6 FBA User buffer end address.
7 SPTR A(DEVISP) Pointer to the interrupt service entry of the DCB.
8 DEV DEV Device number.
9 AET A(DEVBSY) Pointer to the device busy flag in the available equipment table.
10 UBSY A(UBSY1) Pointer to the common driver termination routine.
5-6
REG
CONSTANT
SYMBOLIC CONTENTS
11
12
13
14
15
ERRTN
ACO
AC1(RTN)
AC2
AC3
BAL DVR, INTRET
MEANING
Error status register,
General accumulator
General accumulator (subroutine return address).
General accumulator,
General accumulator.
| USER PROGRAM
SVC 1/0
DOS
EXECUTIVE
BRANCH
}
DRIVER EXTERNAL
INITIALIZATION INTERRUPTS
PHASE ENABLED
SINT
“ DRIVER EXTERNAL
INTERRUPT INTERRUPTS
SERVICE PHASE DISABLED
ATL
DRIVER EXTERNAL
TERMINATION INTERRUPT
PHASE ENABLED
LPSW
USER
PROGRAM
Figure 5-1. 1/0 Logic General Flow
5-7
PHASE I
PHASE II 3
2 | REGISTERS FROM DCB
USER
PROGRAM
| SVC | HANDLER
GET SVC PARAMETERS
FROM PARAMETER BLOCK
- LU
— FUNCTION
~ START/END ADDRESS
GET DCB ADDRESS
FROM LU TABLE
IF DEVICE IS BUSY
EXIT BACK TO SVC
TO HANG UP CALLER
GET DRIVER
MARK DEVICE BUSY
LU/DCB TABLE
A (DCB)
A(DCB)
A (DCB)
DEVICE DRIVER
BY THE ASSIGN
TABLE
MODIFIED
COMMAND
AVAILABLE EQUIPMENT TABLE
BUSY FLAG
— DEVICE NUMBER
<—j— ADORESS OF DRIVER INITIALIZATIGN SECTION
GO TO DVR
SAVE DRIVER
REGISTERS IN DCB
SET UP INT. SERV. PTR.
SINT O (DEV)
SET PSW WAIT BIT
IF I/O WAIT COMMAND
RETURN FROM
0 SVC TO USER
REGISTERS IN DCB
RESTORE
DRIVER
INITIALIZATION
SECTION
(ANY NECESSARY
HOUSEKEEPING)
DCB
SAVE USER REGISTERS
LOAD DRIVER REGISTERS
BRANCH TO DRIVER
| SAVE DRIVER
DRIVER INTERRUPT
SERVICE ROUTINES
1
USER REGISTERS
RETURN FROM
EXT INTERRUPT
/
PHASE III +
5-8
SET DEVICE NON BUSY
RESET USER WAIT FLAG
RESTORE USER REGISTER
RETURN FROM Q TERM
IF OPERATION
COMPLETE
ADD DCB ADDRESS
TO TOP OF LIST
(LIOTRM)
— ——_ Ee — SEE p— | Uli
TERMINATION
SECTION OF
DRIVER
INTERRUPT
PHASE 1
PHASE II
TERMINATION
PROCESSING
(OPTIONAL)
PHASE IIT TERMINATION PHASE
TV —D_“—od EE emf el — ein Se Sl A ei ———
INITIALIZATION PHASE
INTERRUPT SERVICE PHASE
LIOTRM
EXTERNAL
INTERRUPT
SAVE USER
REGISTERS
RTL DCB ADDR
LOAD DRIVER
REGISTERS
FROM DCB
BRANCH TO DVR
Figure 5-2. 1/0 Logic Detailed Flow
HSPTR
DSKCTL
NUMLGU
CARD
PRINT
MAG1
CASI
PHSRCL
MOD74
MOD50
COPY
APPENDIX 1
APPROXIMATE NUMBER OF BYTES REQUIRED
FOR OPTIONAL SYSGEN MODULES
171
3100 (includes all disc oriented operator commands)
32 per logical unit if DSKCTL specified
300
120
400
400
value specified in EQU statement
64
275
320
Al-1/A1-2
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