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DEC-S8-OSSMB-A-D

May 1974

127 pages

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Document:	OS8 v3ssup
Order Number:	DEC-S8-OSSMB-A-D
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Pages:	127
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OCR Text

so~ware

support manual

digital equipment corporation

OS/8 SOFTWARE SUPPORT ~mNUAL

(Version 3)

DEC-S8-0SSMB-A-D

Order additional copies as:directed on the Software
Information page at the back of this document.

digital equip.ment corporation · maynard. massachusetts

First Printing, January 1973
Revised, June 1974

The information in this document is subject to change without notice
and should not be construed as a commitment by Digital Equipment
Corporation. Digital Equipment Corporation assumes no responsibility
for any errors that may appear in this manual.
The software described in this document is furnished to the purchaser
under a license for use on a single computer system and can be copied
(with inclusion of DIGITAL's copyright notice) only for use in such
system, except as may otherwise be provided in writing by DIGITAL.
Digital Equipment Corporation assumes no responsibility for the use
or reliability of its software on equipment that is not supplied by
DIGITAL.

The HOW TO OBTAIN SOFTWARE INFORMATION page, located at the back of
this document, explains the various services available to DIGITAL
software users.
The postage prepaid READER'S COMMENTS form on the last page of this
document requests the user's critical evaluation to assist us in
preparing future documentation.

The following are trademarks of Digital Equipment Corporation:
COP
COMPUTER LAB
COMSYST
COMTEX
DDT
DEC
DECCOMM
DECTAPE
DIBOL

DIGITAL
DNC
EDGRIN
EDUSYSTEM
FLIP CHIP
FOCAL
GLC-8
IDAC
IDACS

INDAC
KAlD
LAB-8
LAB-8/e
LAB-K
OMNIBUS
OS/8
PDP
PHA

PS/8
QUICKPOINT
RAO-8
RSTS
RSX
RTM
RT-ll
SABR
TYPESET 8
UNIBUS

PREFACE

The 8K Operating System (05/8)
is an extremely powerful program
development system.
05/8 greatly expands the capabilities of any 8K
pop-a, 8/I, 8/L, 8/E, or PDP-l2 computer having the necessary disk or
DECtape storage.
Use of 05/8, is described in detail in the 05/8
HANDBOOK (DEC-S8-0SHBA-A-D).
This manual covers a wide range of advanced topics pertinent to the
experienced user. In Chapter I the various basic system concepts are
described and terms are defined. Chapter 2 explains the process by
which user programs call upon the system for the performance of
important operations including loading device handlers, opening and
closing files, and chaining to other programs. Chapter 3 covers the
functions of the Command Decoder and the means by which the user
program can employ its services.
Chapter 4 explains the use and
operation of the device handlers in detail.
Chapter 5 covers the
details of "custom tailoring" a system, including how to write a
device handler for a non-standard device.
Technical information, intended to er"~~~ce the information in the OS/8
HANDBOOK, as well as this manual, can be found in t~e Appendices.
Appendix A details the 05/8 directory structure and g1ves standard
file format. Appendix B describes the system data base and gives the
layouts of the system areas. Appendix C gives a complete list of
system error messages.
Appendix D illustrates some useful advanced
techniques and programming "tricksn for use with the 05/8 system.
Appendix E is a complete list of the standard ASCII character codes
meaningful to 05/8. Finally, Appendix F describes a set of generalized
Tin _,...
.. +0; "".00'" i=,..._ ""'.0 "10..44...........
.... ~.o_ +-ho
,.,\,&w .....
. . . . ...... nC
....,.." 10. .,."p.,.+-o",
., U

....

1W1i;;J

. . ....,...

.....w~

iii

IIWII '-,.... ........

,.....,f"""\' .. ~":"',~~c::
"'-v ............... ~ .... ~

Page
OS/8 CONCEPTS ;'':rD TERMINOLOGY

1-1

1.1

SOFTWARE COMPO~~ENTS OF OS/8

1-1

l..-'

FILES

1-2

1.2.1
1.2.2
1.2.3
1.2.4

File Names and Extensions

1-2
1-2
1-3

CHAPTER 1

File Structured Devices
File Types
File Directories and Additional
Information Words

1-3

1.3
1.3.1
1.3.2
1.3.3

CORE CONTROL BLOCK
Program Starti~g Address
Job Status Word.
Software Core Size

1-4
1-4
1-5
1-6

1.4

DEVICE ~AMES ;'.~':D DEVICE NUMBERS

1-6

1.5

THE DEVICE AND FILENAME PSEUDO-OPS

1-7

USER SERVICE ROUTINE

2-1

2.1
2.1.1
2.1.2

CALLING THE USR
Standard USR Call
Direct and Indirect Calling Sequence

2-1
2-1
2-2

2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
2.2.7
2.2.8
2.2.9
2.2.10
2.2.11

SUMMARY OF USR FUNCTIONS
FETCH Device Handler
LOOKUP Permanent File
ENTER Output (Tentative) File
The CLOSE Function
Call Command Decoder (DECODE)
CHAIN Function
Signal User Error
Lock USR in Core (USRIN)
Dismiss USR from Core (USROUT)
Ascertain Device Information (INQUIRE)
RESET System Tables

2-3
2-4
2-5
2-6
2-8
2-9
2-10
2-11
2-12
2-12
2-13
2-14

THE COMMAND DECODER

3-1

3.1

COMMAND DECODER CONVENTION

3-1

3.2

COMMAND DECODER ERROR MESSAGES

3-3

3.3

CALLING THE COMMAND DECODER

3-3

3.4
3.4.1
3.4.2
3.4.3
3.4.4

COMMAND DECODER TABLES
Output Files
Input Files
Command Decoder Option Table
Example

3-4
3-4
3-5
3-6
3-7

CHAPTER 2

CHAPTER 3

Page
SPECIAL HODE OF THE COMMAND DECODER
Calling the Command Decoder Special Mode
Operation of the Command Decoder in Special
Mode

3-9

3.6

CCL AND THE COMMAND DECODER

3-10

3.7

USEFUL LOCATIONS IN BATCH

3-10

3.8

CCL TABLES

3-10

USING DEVICE HANDLERS

4-1

4.1

CALLING DEVICE HANDLERS

4-1

4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
4.2.S
4.2.9
4.2.10

DEVICE DEPENDENT OPERATIONS
Teletype (TTY)
High-Speed Paper Tape Reader (PTR)
High-Speed Paper Tape Punch (PTP)
Line Printer (LPT)
Cassettes
Card Reader (CDR)
TMSE Handler
File Structured Devices
TDSE DEC tape
KL8E Teletype Handler

4-4
4-4
4-4
4-5
4-5
4-6
4-7
4-8
4-11
4-11
4-12

RECONFIGURING THE OS/S SYSTEM

5-1

5.1

WRITING DEVICE HANDLERS

5-1

5.2

INSERTING DEVICE HANDLERS INTO OS/8

5-5

OS/8 FILE STRUCTURES

A-I

A.l
A.l.l
A.l.2
A.l.3

FILE DIRECTORIES
Directory Entries
Number and Size of OS/S Files
Sample Directory

A-I
A-2
A-3
A-3

A.2
A.2.1
A.2.2

FILE FORMATS
ASCII and Binary Files
Core Image (.SV format) Files
Relocatable FORTRAN Library File

A-4
A-4
A-5
A-7

DETAILED LAYOUT OF THE SYSTEM

B-1

B.l

LAYOUT OF THE SYSTEM DEVICE

B-1

B.2

LAYOUT OF THE 05/8 RESIDENT PROGRAM

B-2

B.3
B.3.1
B.3.2
B.3.3
B.3.4
B.3.5
B.3.6

SYSTEM DEVICE TABLES
Permanent Device Name Table
User Device Name Table
Device Handler Residency Table
Device Handler Information Table
Device Control Word Table
Device Length Table

B-4
B-4
B-4
B-5
B-5
B-6
B-7

3.5
3.5.1
3.5.2

CHAPTER 4

4.2.2

CHAPTER 5

APPENDIX A

A. 2. 3

APPENDIX B

3-8
3-9

Page

SYSTEM ERROR CCXDITIONS AND MESSAGES

C-l

C.l

SYSTEM HALTS

C-1

C.2

USR ERRORS

C-2

KEYBOARD MONITOR ERRORS

C-3

C.4

CCL ERROR MESSAGES

C-4

C.5

COMMAND DECODER ERRORS

C-7

PROGRAMMING NOTES

0-1

D.l

THE DEFAULT FILE STORAGE DEVICE, DSK

D-l

D.2

MODIFICATION TO CARD READER HANDLER

D-2

D.3

SUPPRESSION OF CARRIAGE RETURN/LINE FEED
IN FORTRAN

D-4

ACCESSING THE SYSTEM DATE IN A FORTRAN
PROGRAM

0-4

DETERMINING CORE SIZE ON PDP-8 FAMILY
COMPUTERS

0-5

USING PRTC12-F TO CONVERT OS/8 DECTAPES
TO OS/12 LINCTAPES

0-6

0.7
0.7.1
0.7.2

NOTES ON LOADING DEVICE HANDLERS
Problem with Multiple Input Files
Dynamically Loading Device Handlers

0-7
0-7
D-7

0.8

AVAILABLE LOCATIONS IN THE USR AREA

0-8

D.9

ACCESSING ADDITIONAL INFORMATION WORDS
IN OS/8
After a LOOKUP or ENTER
After a CLOSE
Rewriting the Current Directory Segment

0-9
0-9
D-9
D-9

APPENDIX C

APPENDIX D

0.4

0.5
0.6

D.9.l
D.9.2
D.9.3
D.10
D.10.l
D.10.2

SABR PROGRAMMING NOTES
Optimizing SABR Code
Calling the USR and Device Handler's from
SABR Code

0-12

APPENDIX E

CHARACTER CODES AND CONVENTIONS

E-l

APPENDIX F

OS/8 INPUT/OUTPUT ROUTINES

F-1

F.l

GENERAL DESCRIPTION

F-1

F.2

SUBROUTINE FUNCTIONS

F-1

F.3
F.3.l

SUBROUTINE PARAMETERS
Example
Subroutine Listing

F-3
F-3
F-5

F.3.2

vii

D-10

D-IO

CHAPTER 1

OS/8 CONCEPTS AND TERMINOLOGY

Before examining the details of the OS/8 system, the reader should
first be familiar with the simpler techniques and terms used within
the framework of the OS/8 system. The material in this chapter, along
with that contained in the OS/8 HANDBOOK, provides the tools needed to
pursue the later chapters.

1.1

SOFTWARE COMPONENTS OF OS/8

There are four main components of the OS/8 system:
1.

The Keyboard Monitor performs commands specified by the user
at the keyboard console. The nine Keyboard Monitor commands
(ASSIGN, DEASSIGN, GET, SAVE, ODT, RUN, R, START, and DATE)
are explained in Chapter 1 of the OS/8 HANDBOOK.
User programs can exit to the Keyboard Monitor by executing a
to location 7600 in field 0. All JMPs to 7600 must be
made with the DATA FIELD set to zero.
This saves the
contents of locations 0000 to 1777 in field 0 and loads the
Keyboard Monitor which could be called by a JMP to location
7605 in field O. In this latter case the contents of core are
not saved, which conserves some time.

JMP

Existing system programs, device handlers, and the Command
Decoder test for the CTRL/C character in the terminal input
buffer and~ on finding this character, abort the current
operation and perform a JMP to 7600 in field O. Thus, typing
CTRL/C is the conventional method of calling the Keyboard
Monitor from the console.
2.

Device handlers, which are subroutines for performing all
device-oriented input/output operations, can be utilized by
any program.
These subroutines have
standard
calling
sequences and "mask" from the user program the special
characteristics of the I/O device.
In this way, device
independent I/O is achieved.
A detailed description of
device handlers is found in Chapter 4.

The User Service Routine (USR)
is to a program what the
Keyboard Monitor is to the user. For example, programs can
request the USR to fetch device handlers, perform file
operations on any device, chain to another program, or call
the Command Decoder. A full description of the USR functions
is found in Chapter 2.

1-1

1.2

The Command Decoder interprets a command line typed by the
user to indicate input and output files and various options.
The command line format is described in detail in Chapter 1
of the OS/8 HANDBOOK. The Command Decoder removes the burden
of this repetitive operation from the userls program. A full
description of the Command Decoder's function is found in
Chapter 3.

Two other components, ABSLDR and ODT, are not logically part
of the 05/8 system. However, in the sources and listings,
ABSLDR is combined with the Keyboard Monitor and USR. ODT is
combined with the command decoder.

FILES

Files are basic units of the 05/8 system, and a thorough understanding
of file structure is required for its use. A file is any collection
of data to be treated as a unit.
The format of this data is
unimportant;
for example, 05/8 can manipulate several standard
formats, including ASCII files, binary files, and core image files.
The important consideration is that the data forms a single unit
within the system.

1.2.1

File Names and Extensions

individual file is identified by its file name and extension.
The
file name consists of up to six alphanumeric characters, optionally
followed by a two character extension. The extension is often used to
clarify the format of the data within the file. For example, an ASCII
file used as input to PAL8 might be given a PA extension, while a core
image file has a SV extension.
An

1.2.2

File Structured Devices

Devices that can be logically divided into a number of 256-word blocks
and have the ability to read and write from any desired block are
called file structured devices.
Disks and DECtapes
are
file
structured devices while a paper tape reader or terminal is not.
Cassettes and magnetic tapes form an intermediate case. They may be
treated directly as non-file structured devices, or the program MCPIP
may appear to be file structured.
The system device (SYS) in any 05/8 system is always file
as is the default storage device, DSK.

structured,

All 05/8 file structured devices must be logically divided into these
256-word blocks.
Hence, 256 words is considered the standard 05/8
block size. Some devices, like RK8, DECtape, and LINCtape, are
physically divided into blocks. These physical blocks should not be
confused with the logical 256-word blocks. For example, DECtapes must
be formatted with standard 129-word physical blocks. A logical 05/8

1-2

block consists of the first 128 words of two consecutive physical
DECtape blocks. The 129th word of every DECtape block is not used by
OS/8. Similarly, LINCtapes are formatted with 129 (or 128) words per
block but never 256, as this format is unacceptable to OS/8.
A given OS/8 file consists of one or more sequential blocks of 256
words each (consecutively numbered). A minimum of one block per file
is required, although a single file could occupy all of the blocks on
a device.

1.2.3

File Types

Three different types of files exist in the OS/8 system:
1.

"empty file" is a contiguous area of unused blocks.
files are created when permanent files are deleted.

Empty

A "tentative file" is a file that is open

to accept output
and has not yet been closed. Only one tentative file can be
open on any single device at one time.

i.'\

"permanent file" is a file that has been given a fixed size
and is no longer expandable.
A tentative file becomes
permanent when it is closed.

To further understand file types, consider what occurs when a file is
created.
Normally, the User Service Routine, in creating a tentative
file, first locates the largest empty file available and creates a
tentative file in ~~at space. This establishes the maxim~Ti space into
which the file can expand. The user program then writes data into the
tentative file. At the end of the data, the program calls the USR to
close the tentative file, making it a permanent file. The USR does so
and allocates whatever space remains on the end of the tentative file
to a new, smaller, empty file.

1.2.4

File Directories

~~d

Additional Information Words

To maintain records of the files on a device, 05/8 allocates blocks 1
through 6 of each file structured device as the file directory.
Entries in this directory inform the system of the name, size, and
location of each file, including all empty files and the tentative
file, if one exists. For a detailed description of the entries in the
file directory, see Appendix A.
Each entry in a directory can, optionally, have extra storage words
called
Additional Information Words.
The number of Additional
Information Words is determined at the time the directory is initially
created (normally by using the /S or /Z features of PIP: see Chapter
1 of the 05/8 HANDBOOK.
Whenever Additional Information Words are used, the first one for each
file entry is used to store the value of the System Date Word at the
time the file was created. OS/8 automatically uses one extra word per
entry for the date.
This value is set by executing a DATE command

1-3

(see Chapter 1 of the OS/8 HANDBOOK) which codes the current date into
memory location 07666 in the follow~ng format:

YEAR-1970
(0-7 )
A date word of 0 implies that no DATE command has been executed
the system initialization.

since

The values of Additional Information Words beyond the first are
user-defined.
See Appendix 0 for further information on Additional
Information Words.

1.3

CORE CONTROL BLOCK

Associated with each core image -file (SV file) is a block of data
called the Core Control Block. The Core Control Block is a table of
information containing the program's starting address, areas of core
into which the program is loaded, and the program's Job Status Word.
The Core Control Block is created at the time the program is loaded by
ABSLDR or other means and is written onto the SV file by the SAVE
operation. More information on the Core Control Block can be found in
the description of core image files in section A.2.2. Note that
specifying arguments to the SAVE command as described in Chapter 1 of
the 05/8 HANDBOOK, can alter the contents of the target program's Core
Control Block.
When a program is loaded, the starting address and Job Status Word are
read from the Core Control Block and saved in core. The Core Control
Block itself is saved in the last 200 (octal) words of block 37 on the
system device unless the program was loaded with the R (rather than
GET or RUN) command.

1.3.1

program Starting Address

The current starting address (used by the START command) is stored in
two words at locations 07744 and 07745. The format of these words is:
LOCATION

CONTENTS

07744

62n3

n is the field in
which to start.

07745

nnnn

Starting address of
the program.

NOTES

1-4

1.3.2

Job Status I''';ord

that
affect
OS/8
The Job Status ~';ord contains certain flags
operations, sucn as ~vhether :.:) save core when loading the USR or
The Job Status ~ord for the program currently in
Command Decoder.
at location
07746
and contains the following
core
is
saved
information:
Bit Condition
Bit

a =1

Meaning
File does not load into locations
rot' ...... ..,
U 1. ! ! ! =

00000

File does not load into locations
to ~1777.

~OOOO

.1. _ _

'Co

Bit 1

Bit 2 = 1

Program must be reloaded before
be restarted.

Bit 3

Program does not destroy the contents of
the highest existing memory field, an
optimization for the Batch system.

Bits 4

t.~ru

Bit 10

Locations 00000 to 01777 need not be
saved when calling the Command Decoder.

Bit 11

Locations 10000 to 11777 need
saved when calling the USR.

can

Reserved for future use.

not

When bit 2 of the Job status Word is 1, any attempt to perform a START
(without an explicit address) results in a
NO! !

error message being printed. As this bit is always zero in the Core
Control Block, the user program is expected to internally set this bit
(in location 7746) if a program is not restartable.
This could be
done as follows:
COP a
TAD I (7746

/LOAD JOB STATUS WORD

AND (6777
TAD (1000
DCA I (7746

/JOB IS NOT RESTARTABLE

The Job Status Word can be updated from the user's program or with the
ABSLDR /P option, thus providing optimization of tape (disk) motion.
More information on the Core Control Block can be found in the
description of Core Image (SV) files found in Appendix A.
Bit 3 of the JSW (Job Status Word) is used as an optimization for the
Batch operating system.
If a program can never cause the highest
existing memory field to be altered, this bit should be set.
For
example, EDIT, PIP, FORT, and SABR can never use memory above 8K.
Thus, they should set bit 3 of the JSW.
Programs such as ABSLDR,

1-5

LOADER, PAL8 and CREF can alter all of core. They should perhaps not
have bit 3 on. Note that the more core that exists, the more unlikely
it is that a program will destroy upper core. Thus, on 28K systems,
only the largest FORT~~ programs can alter field 6 and, in general,
bit 3 should be set.

1.3.3

Software Core Size

Location 07777 contains the software core size in bits 6-8. This
represents the highest memory field available for use by OS/8. If bits
6-8 contain 0, all of the available memory is used. Most OS/8 cusps
interrogate this word to determine how much memory is available. The
other bits of this location are reserved for use by BATCH and should
not be touched by user programs.

1.4

DEVICE NAMES AND DEVICE NUMBERS

The OS/8 system can accommodate up to 15 separate devices. In Chapter
1 of the OS/8 HANDBOOK the reader is introduced to the concept of
device names. Briefly, each device on the system is recognized by
either a permanent device name (such as PTR or DTAI) which is created
when the system is built, or a user-defined device name determined by
an ASSIGN command.
The system insures that the user-defined device
name takes precedence. For example •
• ASSIGN DSK DTA4
causes all future references to DTA4 to address the device DSK.
In calling the User Service Routine, a device can be alternatively
recognized by a device number. Each device on the system has a unique
predefined number in the range 1 to 17 (octal) assigned at the time
the system is generated.
Thus, user programs have the choice of
referring to a device by either name or number. Referencing a device
by name is preferable, as it maintains device independence for the
program.
Accessing devices by number should be done only when the appropriate
number has been obtained from a USR INQUIRE CALL. Except for SYS and
DSK, the OS/8 peripherals do not have fixed numbers; instead, device
numbers vary whenever BUILD is used to modify a system. Thus, it is
suggested that reference by name be used whenever possible.
To determine whether a device name is recognized in the system,
attempt to ASSIGN that device.
For example, to determine whether
LINCtape handlers are called LTA or DTA, perform:
• DEASSIGN
.AS LTAO
If the system responds with a dot (.), LTAO does indeed exist.
system responds with:

1-6

If the

LTAO :';OT AVAIL.iillLE
no device named

1.5

L~AO

is present.

THE DEVICE fu'lD FILENAME PSEUDO-OPS

Several of the USR functions take device names or file names as
arguments.
To simplify the task of generating these arguments, the
DEVICE and FILENAME pseudo-ops have been added to the PAL8 Assembler.
A device name consists of a two word block, containing
four
alphanumeric characters in six-bit ASCII format. A block in this
format can be created by the DEVICE pseudo-op as follows:
DEVICE DTAI
generates the following two words:
0424
0161
Similarly, the FILENAME pseudo-op creates a four word block, the first
three words of which contain the file name and the fourth word of
which contains the file extension. For example:
FILENAME PIP.SV
generates the following four words:
2011
2000
0000
2326
Note that positions for characters 4 through 6 are filled with zeros.
The DEVICE and FILENAME
following chapters.

pseudo-ops

1-7

are

used

examples

the

CHAPTER 2
USER SERVICE ROUTINE

The User Service Routine, or USR, is a collection of subroutines which
perform the operations of opening and closing files, loading device
handlers, program chaining, and calling the Command Decoder. The USR
provides these functions not only for the system itself, but for all
programs running under the OS/8 system.

2.1

CALLING THE USR

Performing any USR function is as simple as g~v~ng a JMS followed by
the proper arguments.
Calls to the USR take a standardized calling
sequence. This standard call should be studied before progressing to
the operation of the various USR functions.

2.1.1

standard USR Call

In the remainder of this chapter, the following
referenced:

calling

sequence

TAD VAL

The contents of the AC is applicable
some cases only.

CDF N

Where N is the value of the current
progr~" field multiplied by 10 (octal).

CIF 10
JMS I

(USR

Where USR is either 7700 or
section 2.1.2).

0200,

(see

FUNCTION

This word contains an integer from 1 to
13
(octal)
indicating
which
USR
operation is to be performed.

ARG(l)

The number and meaning of these argument
words varies with the particular USR
function to be performed.

error return

When applicable, this
address for all errors.

normal return

The operation was successful. The AC is
cleared and the data field is set to
current field.

2-1

the

return

This calling sequence can change =~om function to function.
For
example, some functions take no value in the AC and others have fewer
or greater numbers of arguments.
Nonetheless, this format
is
generally followed.
The value of the data field preceding the JMS to the USR is
exceedingly important.
The data field MUST be set to the current
field, and the instruction field MUST be set to 1. Note that a CDF is
not explicitly required if the data field is already correct. When a
doubt exists as to the data field setting, an explicit CDF should be
executed.
There are three other restrictions which apply to all
follows:
1.

USR

calls,

The USR can never be called from any address between
and 11777. Attempting to do so results in the:
MONITOR ERROR 4 AT xxxxx

10000

(ILLEGAL USR CALL)

message and termination of program execution. The value of
xxxxx is the address of the calling sequence (in all such
MONITOR ERROR messages).

2.1.2

Several USR calls take address pointers as arguments.
These
pointers always refer to data in the same memory field as the
call.

When calling the USR from field 1, these address pointers
must never refer to data that lies in the area 10000 to
11777.

Direct and Indirect Calling Sequence

A user program can call the USR in two ways. First, by performing a
JMS to location 17700 In this case, locations 10000 to 11777 are saved
on a special area on the system device, and the USR is then loaded
into 10000 to 11777. When the USR operation is completed, locations
10000 to 11777 are restored to their previous values.
N~E

By setting bit 11 of the Job Status Word
to a 1, the user can avoid this saving
and restoring of core when preserving
core is unnecessary.
Alternatively, a program can opt to keep the USR permanently resident
in core at locations 10000 to 11777 by using the USRIN function (see
section 2.2.8). Once the USR has been brought into core, a USR call
can be made by performing a JMS to location 10200. This is the most
efficient way of calling the USR.
When USR operations have been
completed, the program restores locations 10000 to 11777 to their
initial state by executing the US ROUT function, if necessary (see
section 2.2.9).

2-2

2.2

Summary of USR Functions
Function
Code

operation

Name

into
device ha~dler
cors.
address of the
the
entry

FETCH

Loads a
Returns
handler.

LOOKUP

Searches the file directory on
any
device to locate a specified permanent

file.
3

ENTER

Creates and opens for output a tentative
file on a specified device.

Closes the currently open tentative file
on the specified device and becomes a
permanent file.
Also, any
previous
permanent file with the same file name
and extension is deleted.

DECODE

Calls the Command Decoder. The function
of the Command Decoder is described in
Chapter 3.

CHAIN

Loads a specified core image file
the system device and starts it.

ERROR

Prints an error message of the form USER
ERROR n AT LOCATION xxxxx.

USRIN

Loads the USR into core.
Subsequent
calls to the USR are by an effective JMS
to location 10200.

US ROUT

Dismisses the USR from core and restores
the previous contents of locations 10000
to 11777.

INQUIRE

Ascertains whether a given device exists
and,
if so, whether its handler is in
core.

RESET

Resets system tables
cleared state.

14-17

their

from

initial

Not currently
used,
these
request
numbers are reserved for future use.

An attempt to call the USR with a code greater than 13
(octal) will
currently cause a Monitor Error 4 message to be printed and the
program to be aborted.

2-3

Function Code = 1

FETCH Device Handler

2.2.1

Device handlers must be loaded into core so as to be available to the
USR and user program for I/O ooerations on that device. Before
performing a LOOKUP, ENTER, or CLOSE function on any device, the
handler for that device must be loaded by FETCH.
The FETCH function takes two distinct forms:
1.

Load a device handler corresponding to a given device name.

Load a device handler corresponding to a given device number.

First, the following is an example of loading a handler by
memory field 0:
CLA

COF 0
CIF 10
JMS I (USR
1
DEVICE DTA3
6001
JMP ERR

name

from

/AC MUST BE CLEAR
/DF = CURRENT FIELD
/IF = 1
/FUNCTION CODE = 1
IGENERATES TWO WORDS: ARG(l)
/AND ARG(2)
/ARG (3)
IERROR RETURN
INORMAL RETURN

•
•
ARG(l) and ARG(2) contain the device name in standard format.
If the
normal return is taken, ARG(2)
is changed to the device number
corresponding to the device loaded.
ARG(3)
contains the following
information:
Bits 0 to 4 contain the page number into which the handler is
loaded.
Bit 11 is 0 if the user program
handler.

can

only

I-page

Bit 11 is 1 if there is room for a 2-page handler.
Notice that in the example above, the handler for DTA3 is to be loaded
into locations 6000 to 6177. If necessary, a two page handler could be
loaded; the second page would be placed in locations 6200 to 6377.
After a normal return, ARG(3) is changed to contain the entry point of
the handler.
A different set of arguments is used to fetch a device
number. The following is an example of this form:
TAD VAL
COF 0
elF 10
JMS I (USR
1

6001
JMP ERR

lAC IS NOT ZERO

IOF = CURRENT FIELD
IF = 1

/FUNCTION CODE = 1
IARG(l)
/ERROR RETURN
INORMAL RETURN

2-4

handler

On entry to the USR, ~he AC con~a~ns the device number in bits 8 to 11
(bit a to 7 are ignored). The format for ARG(l) is the same as that
for ARG(3) in the previous example.
Following a normal return ARG(l)
is replaced with the entry point of the handler.
The conditions that can cause an error return to occur in
are as follows:

both

cases

There is no device corresponding to the given device name
device number, or

attempt was made to load a two page ha~dler into one page~
If this is an attempt to load the handler by name, the
contents of ARG(2) have been changed already to the internal
device number.

In addition, one of the following Honitor errors
followed by a return to the Keyboard Monitor:
Error l\1essage

can

printed,

Meaning

MONITOR ERROR 4 AT xxxxx
(ILLEGAL USR CALL)

Results if bits 8 to 11 of the AC
are zero
(and bits 0 to 7 are
non-zero).

MONITOR ERROR 5 AT xxxxx
(I/O ERROR ON SYS)

Results if a read error occurs
while loading the device handler.

The FETCH function checks to see if the handler is in core, and if

it
is not, then the handler and all co-resident handlers are loaded.
w-nile the FETCH operation ~s essentially a simple one, the user should
be aware of the following points:

Device handlers are always loaded into memory field O.

The entry point that is returned may not be on the page
desired.
This would happen if the handler were already
resident.

Never attempt to load a handler into the 7600 page or into
page O. Never load a two page handler into the 7400 page.

For more information on using device handlers, see Chapter 4.
NOTE
Two or
more
device
handlers
are
"co-resident"
when
they
are
both
included in the same one or two core
pages.
For example,
the paper tape
reader
and
punch
routines
are
co-resident, as are the eight DECtape
handler routines.

2.2.2

LOOKUP Permanent file

Function Code

This request locates a permanent file entry on a given device, if
exists. An example of a typical LOOKUP would be:

2-5

one

TAD VAL
CDF o
CIF 10
JMS I (USR
2

ILOAD DEVICE I-;UMBER
IDF=CURRENT FIELD
lIP = 1

IFUNCTION CODE = 2
IARG(l), POINTS TO FILE NAME
/ARG (2)
o
/ERROR RETURN
JMP ERR
/NORMAL RETURN
FILENAME PROG.PA
NAME

NAME,

This request looks up a permanent file entry with the name PROG.PA.
The device number on which the lookup is to be performed is in AC bit
8 to 11. ARG(l) contains a pointer to the file name.
Note that the
file name block must be in the same memory field as the call, and that
it cannot be in locations 10000 to 11777. The device handler must have
been previously loaded into core.
If the normal return is taken,
ARG(l} is changed to the starting block of the file and ARG(2)
contains the file length in blocks as a negative number. If the
device specified is a readable, non-file structured device (for
example, the papertape reader), then ARG{l) and ARG(2) contain the
file length in blocks as a negative number. If the device specified
is a readable, non-file structured device (for example, the paper tape
reader), then ARG(l) and ARG(2) are both set to zero.
If the error return is taken, ARG(l) and ARG(2)
following conditions cause an error return:

are

The device specified is a write-only device.

The file specified was not found.

In addition, specifying illegal arguments
following monitor errors, followed by a
Monitor:
Error Message

unchanged.

can cause
return to

The

one of the
the Keyboard

Meaning

MONITOR ERROR 2 AT xxxxx
(DIRECTORY I/O ERROR)

Results if an I/O error occurred
while reading the device directory.

MONITOR ERROR 3 AT xxxxx
(DEVICE HANDLER NOT IN CORE)

Results if the device handler for
the specified device is not in
core.

MONITOR ERROR 4 AT xxxxx
(ILLEGAL USR CALL)

Results if bits 8 to 11 of
are zero.

the

The LOOKUP function is the standard method of opening a permanent file
for input.

2.2.3

ENTER Output (Tentative) File

Function Code = 3

The ENTER function is used to create a tentative file entry to be used
for output. An example of a typical ENTER function is as follows:
TAD VAL
CDF 0
CIF 10

/AC IS NOT ZERO
/DF = CURRENT FIELD
/IF = 1

2-6

J:·IS

(USR

/FUNCTION CODE = 3
/ARG(l) POINTS TO FILE NANE
/ARG (2)
/ERROR PETURN

3
:~fu\1E

o
JHP ERROR

/NORM_2)..L RETURN

NAME,

FILENAME PROG.LS

Bits 8 to 11 of the AC contain the device number of the selected
device:
~~e
device handler for this device must be loaded into core
before performing an ENTER function.
If bits 0 to 7 of the AC are
non-zero, this value is considered to be a declaration of the maximum
length of the file.
The ENTER function searches the file directory
for the smallest empty file that contains at least the declared number
of blocks.
If bits a to 7 of the AC are zero,
the ENTER function
locates the largest available empty file.
On a normal return, the contents of ARG(I)
are replaced with the
starting block of the file.
The 2's complement of the actual length
of the created tentative file in blocks (which can be equal to or
greater than the requested length)
replaces ARG(2).
If the file
directory contains any Additional Information Words, the system DATE
(location 17666)
is written as the first Additional Information Word
of the newly created tentative file at this time.

NOTE
If

the

selected

device

not

file

structured but permits output operations
(e.g., the high speed -punch), the ENTER
operation
always succeeds.
In this
case, ARG(I) and ARG(2) are both zeroed
on return.
If the error return is taken, ARG(I) and ARG(2}
follo\-ling conditions cause an error return:
,

J..

are

The device specified by bits 8 to 11 of the

unchanged.

The

is a read only

device.
2.

No empty file exists which
requirement.

satisfies

the

Another tentative file is already active on this device (only
one output file can be active at any given time).

The first word of the file name was 0 (an illegal file nruTle).

In addition, one of the following monitor errors can
by a return to the Keyboard Monitor:
Error Hessage

requested

occur,

length

followed

Meaning

BONITOR ERROR 2 AT xxxxx
(DIRECTORY I/O ERROR)

Result if an I/O error occurred
while reading or writing the device
directory"

HONITOR ERROR 3 AT xxxxx
(DEVICE HANDLER NOT IN CORE)

Results if the device handler for
the specified device is not in
core.

2-7

Error Message

Meaning

!·10NITOR ERROR 4 AT xxxxx
(ILLEGAL USR CALL)

Results if AC bits 8 to 11 are
zero.

NONITOR ERROR 5 AT xxxxx
(I/O ERROR ON SYS)

Read error on the system device
while bringing in the overlay code
for the ENTER function.

HONITOR ERROR 6 AT xxxxx
(DIRECTORY OVERFLOW)

Results if a directory overflow
occurred (no room for tentative
file entry in directory).

2.2.4

The CLOSE Function

Function Code = 4

The CLOSE function has a dual purpose: first, it is used to close the
current active tentative file, making it a permanent file. Second,
when a tentative file becomes permanent it is necessary to remove any
permanent file having the same name; this operation is also performed
by the CLOSE function. An example of CLOSE usage follows:
TAD VAL
CDF 0
CIF 10
JMS I (USR

4
NAME

15
JMP ERR

/GET DEVICE NUMBER
/DF=CURRENT FIELD
IIF=l
IFUNCTION CODE = 4
IARG(l)
IARG(2)
IERROR RETURN
INORMAL RETURN

FILENAME PROG.LS

NAME,

The device number is contained in AC bits 8 to 11 when calling the
USR.
ARG(l)
is a pointer to the name of the file to be deleted and
(ARG(2) contains the number of blocks to be used for the new permanent
file.
The normal sequence of operations on an output file is:
1.

FETCH the device handler for the output device.

ENTER the tentative file on the output device, getting the
starting block and the maximum number of blocks available for
the file.

Perform the actual output using the device handler, keeping
track of how many blocks are written, and checking to insure
that the file does not exceed the available space.

CLOSE the tentative file, making it permanent.
The CLOSE
operation would always use the same file name as the ENTER
performed in step 2. The closing file length would have been
computed in step 3.

After a normal return from CLOSE, the active tentative file is
permanent and any permanent file having the specified file name
already stored on the device is deleted.
If the specified device is a
non-file structured device that permits output (the paper tape punch,
for example) the CLOSE function will always succeed.

2-8

~;OTE

The user must be careful to specify the
same file names ~o the ENTER and the
CLOSE functions.
?ailure to do so can
cause
several
permanent files with
identical names to
appear
in
the
directory.
If CLOSE is intended only to
be used to delete some existing file,
then the number of blocks, ARG(2) should
be zero.
The following conditions cause the error return to be taken:

The device specified by bits 8 to 11 of the AC is a read only
device.

There is neither an active tentative file to be made into a
permanent file, nor a permanent file with the specified name
to be deleted.

In addition, one of the following :10ni tor errors can occur:
Meaning

Error Message

2.2.5

MONITOR ERROR 1 AT xxxxx
(CLOSE ,ERROR)

Results if the length specified by
ARG(2) exceeded the allotted space.

MONITOR ERROR 2 AT xxxxx
(DIRECTORY I/O ERROR)

Results if an I/O error occurred
while reading or writing the device
directory.

MONITOR ERROR 3 AT xxxxx
(DEVICE HANDLER NOT IN CORE)

Results if the device handler for
the specified device is not in
core.

MONITOR ERROR 4 AT xxxxx
(ILLEGAL USR CALL)

Results if AC bits 8 to 11 are
zero.

Call Command Decoder (DECODE)

Function Code = 5

The DECODE function causes the USR to load and execute the Command
Decoder.
The Command Decoder accepts (from the Teletype) a list of
input and output devices and files, along with various options.
The
Command Decoder performs a LOOKUP on all input files,
sets up
necessary tables in the top page of field 1, and returns to the user
program. These operations are described in detail in Chapter 3, which
shoud be read before attempting to use the DECODE function.
A typical call to the Command Decoder looks as follows:
CDF 0
CIF 10
JMS I (USR
5
2001

/DF=CURRENT FIELD
/IF=l
/FUNCTION CODE = 5
IARG(1),

ASSU~.ED

INPUT EXTENSION

/ARG(2), ZERO TO PRESERVE ALL
/TENTATlVE FILES
/NORMAL RETURN

2-9

ARG(l) is the assumed input extension, in the preceding example it is
".PA". On return from the Command Decoder, information is stored in
tables located in the top page of memory field 1. The DECODE function
also resets all system tables as in the RESET function (see RESET
function, section 2,2,11)
if ARG(2)
is 0 all currently active
tentative files remain open:
if ARG(2) is non-zero all tentative
files are deleted and the normal return is to ARG(2)
instead of
ARG(2)+1.
The DECODE function has no error return (Command Decoder error
messages are given in Chapter 3). However, the following Monitor error
can occur:
Meaning

Error Message
MONITOR ERROR 5 AT xxxxx
(I/O ERROR ON SYS)

2.2.6

CHAIN Function

I/O error occurred while reading or
writing on the system device.

Function Code = 6

The CHAIN function permits a program to load and start another program
with the restriction that the program chained to must be a core image
(.SV) file located on the system device. A typical implementation of
the CHAIN function looks as follows:
IDF=CURRENT FIELD
IIF-l

COF 0

elF 10
JMS I

(USR

BLOCK

/FUNCTION CODE
6
/ARG (1), TARTING BLOCK NUMBER

There is no normal or error return from CHAIN.
monitor error can occur:
Error Message

However, the following

Meaning

MONITOR ERROR 5 AT xxxxx
(I/O ERROR ON SYS)

I/O error occurred while reading or
writing on the system device.

CHAIN ERR

If an attempt is made to CHAIN to a
file which is not a core image
(.SV) file. Control returns to the
keyboard monitor.

The CHAIN function loads a core image file located on the system
device beginning at the block number specified as ARG(l) (which is
normally determined by performing a LOOKUP on the desired file name).
Once loaded, the program is started at an address one greater than the
starting address specified by the program's Core Control Block.
CHAIN automatically performs a USROUT function (see section 2.2.9) to
dismiss the USR from core, and a RESET to clear all system tables see
section 2.2.11), but CHAIN does not delete tentative files.
The areas of core altered by the CHAIN function are determined by the
contents of the Core Control Block of the core image file loaded by
CHAIN. The Core Control Block for the file is set up by other ABSLDR
or LOADER programs. It can be modified by performing a SAVE command
with specific arguments. Every page of core in which at least one

2-10

location was saved is loaded.
If the page is one of the "odd
numbered" pages (pages 1, 3, etc,; locations 0200 to 0377, 0600
to
0777, etc.), the previous page is always loaded.
In addition, CHAIN
always alters the contents of locations 07200 to 07577.

CHAIN destroys a necessary part of the
OoT resident breakpoint routine. Thus
be
an OoT breakpoint should
never
maintained across a CHAIN.
With the above exceptions, programs can pass data back and forth in
core while chaining. For example, FORTRAN programs normally leave the
COMMON area in memory field 1 unchanged. This COMMON area can then be
accessed by the program activated by the CHAIN.
2.2.7

Function Code = 7

Signal User ERROR

The USR can be called to print a user error
The following is a possible ERROR call:
CoF 0
CIF 10
JMS I (USR
7

loF
IIF

message

for

program.

= CURRENT FIELD
=1

IFUNCTION CODE
7
IARG(l), ERROR NUMBER

THE ERROR function causes a message of the form:
USER ERROR n AT xxxxx

to be printed. Here n is the error number given as ARG(l); n must be
between 0 and 11 (octal), and xxxxx is the address of ARG(l). If
ARG(I) in the sample call above was at location 500 in field 0, the
message:
USER ERROR 2 AT 00500
would be printed. Following the message, the USR returns
the Keyboard Monitor, preserving the user program intact.
The error number is arbitrary.
meanings:

Two numbers

Error Message

have

control

currently

assigned

Meaning

USER ERROR 0 AT xxxxx

During a RUN, GET, or R command,
this error message indicates that
an error occurred while loading the
core image.

USER ERROR 1 AT xxxxx

While executing a FORTRAN or SABR
program, this error indicates that
a call was made to a subroutine
that was not loaded.

2-11

2.2.8

Function Code

Lock USR in Core (USRIN)

= 10

When making a number of calls to the USR it is advantageous for a
program to avoid reloading the USR each time a USR call is made. The
USR can be brought into core and kept there for subsequent use by the
USRIN function. The calling sequence for the USRIN function looks as
follows:
COP 0
CIP 10
JMS I (7700
10

•

/DP = CURRENT FIELD
/IF = 1
/FUNCTION CODE = 10
/NORMAL RETURN

THE USRIN function saves the contents of locations 10000 to 11777 on
the system scratch blocks" provided the calling program loads into
this area as indicated by the current JSW, and loads the USR, then
returns control to the user program.
N~E

If bit 11 of the current Job Status Word
is a one, the USRIN function will not
save the contents of locations 10000
thru 11777.

2.2.9

Dismiss USR from Core (USROUT)

Function Code

= 11

When a program has loaded the USR into core with the USRIN function
and no longer wants or needs the USR in core, the USROUT function is
used to restore the original contents of locations 10000 to 11777. The
calling sequence for the USROUT function is as follows:
COP 0
CIP 10
JMS I

•

(200

/DP = CURRENT FIELD
/IP = 1
/00 N~ JMS TO 17700!!
/PUNCTION CODE
11
/NORMAL RETURN

The US ROUT function and the USRIN function
are
complementary
operations.
Subsequent calls to the USR must be made by performing a
JMS to location 7700 in field 1.
N~E

If bit 11 of the current Job Status Word
is a 1, the contents of core are not
changed by the USROUT function.
In this
case US ROUT is a redundant operation
since core was not preserved by the
USRIN function.

2-12

2.2.10

Ascertain Device

Informa~ion

(INQUIRE) Function Code

= 12

On some occasions a user may wish to determine what internal device
number corresponas to a g~ven device na~e or whether the device
handler for a specified device is in core, without actually performing
a FETCH operation.
INQUIPE performs these operations for the usere
The function call for INQUIRE closely resembles the FETCH handler
call.
INQUIRE, like FETCH, has two distinct forms:

Obtain the device number corresponding to a given device name
and determine if the handler for that device is in core
(example shown below).

Determine if the handler
number is in core.

corresponding

given

device

An example of the INQUIRE call is shown below:
CLA
CDF 0
CIF 10
JHS I (USR
12
DEVICE DTA3

o
JMP ERR

/AC HUST BE CLEAR
/DF = CURRENT FIELD
/IF = 1
/FUNCTION CODE = 12
IGENERATES TWO WORDS:
IARG(l) AND ARG(2)
/ARG(3)
/ERROR RETURN

INORMAL RETURN

ARG(l) and ARG(2) contain the device name in standard format.
When
the normal return is taken ARG(2) is changed to the device number
corresponding to the given name, and ARG(3) contains either the entry
point of the device handler if i t is already in core, or zero if the
corresponding device handler has not yet been loaded.

A slightly different set of argwuents

USed

about

device by its device number:
TAD VAL
COF 0
CIF 10
JMS I (USR
12
0

JMP ERR

lAC IS NON-ZERO
/DF = CURRENT FIELD

IIF = 1
IFUNCTION CODE = 12
IARG(I)
/ERROR RETURN
/NORMAL RETURN

On entry to INQUIRE, AC bits 8 to 11 contain the device number.

2-13

NOTE
If AC bits a to 7 are non-zero, and bits
8 to 11 are zero
(an illegal device
number) a:
MONITOR ERROR 4 AT xxxxx
message is printed and program execution
is terminated.
On normal return ARG(l) is set to the entry point of the device
handler if it is already in core, or zero if the corresponding device
handler has not yet been loaded. The error return in both cases is
taken only if there is no device corresponding to the device name or
number specified.

2.2.11

Function Code

RESET System Tables

= 13

There are certain occasions when it is desired to reset the system
tables, effectively removing from core all device handlers except the
system handler. An example of the RESET function is shown below:
COF 0
CIF 10
JMS I (USR
13

/OF = CURRENT FIELD
/IF
1

/FUNCTION CODE
13
/0 PRESERVES TENTATIVE FILES
/NORMAL RETURN

RESET zeros all entries except the one for the system device in the
Device Handler Residency Table
(see section B.3.3, removing all
device handlers, other than that for the system device, from core.
This should be done anytime a user program modifies any page in which
a device handler was loaded.
RESET has the additional function of deleting all currently active
tentative files (files that have been entered but not closed). This is
accomplished by zeroing bits 9 through 11 of every entry in the Device
Control Word Table (see section B.3.5).
If RESET is to be used in this last fashion,
to delete all active
tentative files, then ARG(l) must be non-zero and the normal return is
to ARG(l) rather than to ARG(I)+I. For example,
the' following call
would serve this purpose
COF a
CIF 10
JMS I (USR
13
CLA CMA

/OF:CURRENT FIELD
/IF = 1
/FUNCTION CODE
/NON-ZERO:

= 13

The normal return would execute the CLA CMA and all active tentative
files on all devices would be deleted. The Keyboard Monitor currently
does not reset the Monitor tables.
If user programs which do not call
the Command Decoder are used,
it is wise to do a RESET operation
before loading device handlers. The RESET will ensure that the proper
handler will be loaded into core.

2-14

CHAPTER 3
THE CO~~D DECODER

05/8 provides a powerful subroutine called the Command Decoder for use
by all system programs. The Command Decoder is normally called when a
program starts running. When called, the Command Decoder prints an *
and then accepts a command line from the console Teletype that
includes a list of I/O devices,
file names, and various option
specifications.
The Command Decoder validates the command line for
accuracy, performs a LOOKUP on all input files, and sets up various
tables for the calling program.
The operations performed by the Command Decoder greatly simplify the
initialization routines of all 05/8 programs. Also, since command
lines all have a standard basic structure, the Command Decoder makes
learning to use 05/8 much easier.

3.1

COMMAND DECODER CONVENTIONS

Chapter 1 of the OS/8 H&~DBOOK describes the syntax for the conmuu,d
line in detail.
A brief synopsis is given here only to clarify the
later discussion in this chapter.
The command line has the following general form:
*output files

< input files/

(options)

There can be 0 to 3 output files and 0 to 9 input files specified.
Output File Format

Meaning

EXPLE.EX

Output to a file named EXPLE.EX on
device
DSK
(the
default file
storage device).

LPT:

Output to the LPT.
generally
specifies
structured device.

DTA2:EXPLE.EX

Output to a file named EXPLE.EX
device DTA2.

DTA2:EXPLE.EX[99]

Output to a file named EXPLE.EX on
device DTA2. A maximum output file
size of 99 blocks is specified.

null

No output specified.

This format
a non-file

An input file specification has one of the following forms:

3-1

:'leaning

Input File Format
DTA2 : I~lPUT

Input from a file named I~PUT.df on
device DTA2.
"df" is the assumed
input file extension specified in
the Command Decoder.

DTA2:INPUT.EX

Input from a file named INPUT.EX on
device
DTA2.
In this case .EX
overrides the assumed input file
extension.

INPUT.EX

Input from a file named INPUT.EX.
If there is no previously specified
input device, input is from device
DSK,
the
default file storage
device;
otherwise,
the
input
device is the same as the last
specified input device.

PTR:

Input from device PTRi
name
is
needed
for
structured devices.

DTA2:

Input from device DTA2 treated as a
non-file structured device, as, for
example, in the PIP command line:

no file
non-file

*TTY:/L<DTA2:
In both of the last two formats, no
LOOKUP operation is performed since
the device is
assumed
to
be
non-file structured.
null

Repeats input from the previous
device specified (must not be first
in input list, and must refer to a
non-file structured device). For
example:

* <PTR:"
(two null files)
indicates that
three paper tapes are to be loaded.
NOTE
Whenever a file extension is left off an
input file specification, the Command
Decoder first performs a LOOKUP for the
given name appending a specified assumed
extension.
If the LOOKUP fails,
a
second LOOKUP is made for the file
appending a null (zero) extension.

3-2

The Command Decoder verifies that the specified device names,
file
names, and extensions consist only of the characters A through Z and a
through 9. If not, a syntax error is generated and the command line is
considered to be valid.
There are two kinds of options that can be specified:
first,
alphanumeric option switches are denoted by a single alphanumeric
character preceded by a slash (I) or a string of characters enclosed
in parentheses;
secondly, a numeric option can be specified as an
octal number from 1 to 37777777 preceded by an equal sign
(=). These
options are passed to ~~e user progrw~ and are interpreted differently
by each program.
Finally, the Command Decoder permits the command line to be terminated
by either the RETURN or ALT MODE key. This information is also passed
to the user program.

3.2

COMMAND DECODER ERROR MESSAGES

If an error in the command line is detected by the Command Decoder,
one of the following error messages is printed. After the error
message, the Command Decoder starts a new line, prints an *, and waits
for another command line. The erroneous command is ignored.
Error Message

3.3

MeaninC!

ILLEGAL SYNTAX

The command
incorrectly.

line

TOO MANY FILES

More than three output files or
nine input files were specified.
(Or in special mode, more than 1
output file or more than 5 input
files. )

device DOES NOT EXIST

The specified device name does not
correspond to any permanent device
name or any user assigned device
name.

name NOT FOUND

The specified input file name was
not found on the selected device.

formatted

CALLING THE COMMAND DECODER

The Command Decoder is initiated by the DECODE function of the USR.
DECODE causes the contents of locations 0 to 1777 of field 0 to be
saved on the system scratch blocks, and Command Decoder to be brought
into that area of core and started. When the command line has been
entered and properly interpreted, the Command Decoder exits to the
USR, which restores the original contents of a to 1777 and returns to
the calling program.

3-3

N~E

By setting bit 10 of the Job Status Word
to a 1 the user can avoid this saving
and restoring of core for programs that
do not occupy locations 0 to 1777.
The DECODE call can reside in the area between 0000 to 1777 and
function correctly. A typical call would appear as follows:

still

CDF 0
ISET DATA FIELD TO CURRENT FIELD
CIF 10
IINSTRUCTION FIELD MUST BE 1
JMS I (USR IUSR=7700 IF USR IS NOT IN CORE
lOR USR=0200 IF USRIN WAS PERFORMED
5
IDECODE FUNCTION = 5
IARG(l) ,ASSUMED INPUT EXTENSION
2001
o
/ARG(2) ,ZERO TO PRESERVE
/ALL TENTATIVE FILES
INORMAL RETURN

ARG(l) is the assumed input extension. If an input file name is given
with no specified extension, the Command Decoder first performs a
LOOKUP for a file having the given name with the assumed extension.
If the LOOKUP fails, the Command Decoder performs a second LOOKUP for
a file having the given name and a null (zero) extension.
In this
example, the assumed input extension is -.PA-.
DECODE performs an automatic RESET operation (see section 2.2.11) to
remove from core all device handlers except those equivalent to the
system device. As in the RESET function, if ARG(2) is zero all
currently
active tentative files are preserved.
If ARG(2) is
non-zero, all tentative files are deleted and DECODE returns to ARG(2)
instead of ARG(2)+1.
As the Command Decoder normally handles all of its own
is no error return from the DECODE operation.

3.4

errors,

there

COMMAND DECODER TABLES

The Command decoder sets up various tables in the top page of field
that describe the command line typed to the user program.

3.4.1

Output Files

There is room for three entries in the output file table that begins
at location 17600. Each entry is five words long and has the following
format:

3-4

USER SPECIFIED
FILE LENGTH

WORD 1

10 11

4 BIT-DEVICE

NUMBER

I
i

WORD 2

FILE NAME
CHARACTER 1

FILE NAME
CHARACTER 2

WORD 3

FILE NAME
CHARACTER 3

FILE NAME
CHARACTER 4

FILE NAME
CHARACTER 5

FILE NAME

CHARACTER 6

FILE EXTENSION
CHARACTER 1

FILE EXTENSION
CHARACTER 2

} FILE EXTENSION

WORD 4
WORD 5

OUTPUT FILE NAME

( 6 CHARACTERS
I

2 CHARACTERS

Bits 0 to 7 of word 1 in each entry contain the file length, if the
file length was specified with the square bracket construction in the
command line. Otherwise, those bits are zero
8

The entry for the first output file is in locations 17600 to 17604,
the second is in locations 17605 to 17611, and the third is in
locations 17612 to 17616. If word 1 of any entry is zero, the
corresponding output file was not specified. A zero in word 2 means
that no file name was specified.
Also, if word 5 of any entry is zero no file extension was specified
for ~~e corresponding file. It is left to the user program to take
the proper action in these cases.
These entries are
function.

3.4.2

format

that

acceptable

the

ENTER

Input Files

There is room for nine entries in the input file table that begins at
location 17617. Each entry is two words long and has the following
format:
0

WORD 1

MINUS FILE

10 11

4-BIT DEVICE

I NUMBER

LENGTH

WORD 2

: STARTING BLOCK OF FILE

Bits 0 to 7 of word 1 contain the file length as a negative number.
Thus, 377 (octal) in these bits is a length of one block, 376 (octal)
is a length of two blocks, etc.
If bits 0 to 7 are zero, the
specified file has a length greater than or equal to 256 blocks or a
non-file structured device was specified.

3-5

~OTE

This restriction to 255 blocks of actual
specified size can cause some problems
if the program has no way of detecting
end-of-file conditions.
For example,
PIP cannot copy in image mode any file
on a file structured device that is
greater than 255 blocks long, although
it can handle in IA orlB modes (ASCII or
Binary) files of unlimited size. In IA
orlB modes PIP will detect the CTRL/Z
marking the end-of-file.
If this is liable to be a problem, it is
suggested that the user program employ
~e special mode of the Command
Decoder
described in section 3.5 ard F~rfor.m its
own LOOKUP on the input files to obtain
the exact file length.
The two-word input file list entries beginning at odd numbered
locations from 17617 to 17637 inclusive. If location 17617 is zero,
no input files were indicated in the command line. If less than nine
input files were specified, the unused entries in the input file list
are zeroed (location 17641 is always set to zero to provide a
terminator even when no files are specified).

3.4.3

Command Decoder Option Table

Five words are reserved beginning at location 17642 to store the
various options specified in the command line. The format of these
five words is as follows:

17642

10 11

HIGH ORDER 11 BITS F
a N OPTIONS
B

17644 M N

V W X

17645 Y

17643 A

17646 LOW ORDER 12 BITS OF

= > OPTIONS

Each of these bits corresponds to one of the possible alphanumeric
option switches.
The corresponding bit is 1 if the switch was
specified, 0 otherwise.

3-6

NOTE
If no = n option is specified, the
Command Decoder zeroes 17646 and bits 1
to 11

Thus,

17642.

meaningless
cannot tell
specified.

since
that

the
any

typing

user program
option
was

Bit 0 of location 17642 is 0 if the
cc~~~d
line
was
terminated bv a
carriage return, 1 if it was terminated
by an ALT MODE.

3.4.4

Example

To clarify some of the preceding, consider the interpretation
following command line:

the

*BIN[10]<PTR:"DTA2:PARA,MAIN /L=14200$
If this command line is typed to PALS, it would cause assembly of a
program consisting of four separate parts: two paper tapes, one file
named PARA.PA (or just PARA) on DTA2, and one file named MAIN.PA (or
just MAXN) also on DTA2. The binary output is placed on a file named
BIN.BN on device DSK, for which only 10 blocks need be allocated.
No
listing is generated.
In addition, automatic loading of the binary
output is specified by the /L option, with the starting address given
as 4200 in field 1. Finally, the line is terminated by the ALTNODE key
(which echoes as $) causing a return to the Keyboard Monitor after the
program is loaded.
In the case of this example, the Command Decoder returns to PALS
the following values in the system tables:
NOTE

The entries for PTR (where no input file
name is specified) have a starting block
number and file size of zero.
This is
always true of the input table for a
non-file structured device, or a file
structured device on which no file name
is given.

3-7

with

17600

II 0242

0211

lFILE NAME IS BIN

1600

0000
1760 4

0000

NULL EXTENSION

~~ I

1760 5

REMAINING ENTRIES
IN OUTPUT TABLES
ARE ZERO

1761 6
1761 7

~ FIRST PTR INPUT

0016

0000
1762 0
1762 1

0016

0000
1762 2
1762 3

DSK: IS DEVICE NUMBER 2

I
I

DAT2: PARA PA IS 5 BLOCKS LONG,
BEGINNING AT 100(8)

7667

0100

1762 4
1762 5

OTA2: MAIN PA IS 256 (10) OR MORE
BLOCKS LONG, BEGINNING AT BLOCK 105(8)

0007

0105

17626
17627
c:~

17641

3.5

17642

4001

17643

0001

17644

0000

17645

0000

17646

4200

SECOND PTR INPUT

REMAINING ENTRIES
IN INPUT TABLES
ARE ZERO.

- LINE WAS TERMINATED BY ALT MODE
/L WAS ONLY OPTION SWITCH
PECIFIED

- = 14200 WAS SPECIFIED

SPECIAL MODE OF THE COMMAND DECODER

Occasionally the user program does not want the Command Decoder to
perform the LOOKUP on input files, leaving this option to the user
program itself. Programs such as format conversion routines which
access non-standard file structures could use this special format.
If
the input files were not OS/8 format, a command decoder LOOKUP
operation would fail. The capability to handle this case is provided

3-8

in the OS/8 Command Decoder. This capability is generally referred to
as the "special mode" of the Command Decoder.

3.5.1

Calling the Command Decoder Special Mode

The special mode call to the Command Decoder is identical to the
standard DECODE call except that the assumed input file extension,
specified by ARG(l), is equal to 5200. The value 5200 corresponds to
an assumed extension of "*"1 which is illegal. Therefore, the
special mode of the Command Decoder in no way conflicts with the
normal mode.

3.5.2

Operation of the Command Decoder in Special Mode

In special mode the Command Decoder is loaded and inputs a command
as usual. The appearance of the command line is altered by the
special mode in these respects:

line

Only one output file can be specified.

No more than five input files can be specified,
the nine acceptable in normal mode.

The characters asterisk (*) and question mark (1)
are leqal
in file names and extensions, both in input files and on
output files.
It is strongly suggested that these characters
be tested by the user program and treated either as special
options or as illegal file names. The user program must be
careful not to ENTER an output file with an asterisk or
question mark in its name as such a file cannot easily be
manipulated or deleted by the standard system programs.

rather

than

The output and option table set up by the Command Decoder is not
altered in special mode. Entries in the input table are changed to

. . . '-_ &_, '~".''' . .
I..~lt::

,-r

.L.U.Jo..Jo.uW.Jo.U'':J

.;:""'....,.,..~ ... .

... ~ .... " ....... .

c:,

WORD 1
NORD 2
WORD 3
WORD 4
~vORD

10 11

4-BIT DeVICE
NUMBER

BITS 0-7 ARE
ALNAYS 0

CHARACTER 1

FILE ~AME
CHARACTER 2

FILE NAt-IE
CHARACTER 3

FILE NAME
CHARACTER 4

FILE NAME
CHARACTER 5

FILE NAME
CHARACTER 6

FILE EXTENSION
CHARACTER 1

I t FILE EXTENSION
I ~ 2 CHARACTERS

FILE NA.ft.1E

)

3-9

INPUT FILE NAME
6 CHARACTER

The table entry for the first input file is in locations 17605 to
17611; the second in locations 17612 to 17616: the third in locations
17617 to 17623; the fourth in locations 17624 to 17630: and the fifth
in locations 17631 to 17635. A zero in word 1 terminates the list of
input files.
If word 2 of an entry is zero, no input file name was
specified.
The 05/8 batch generating system
decoder in special mode.

3.6

will

allow

calls

the

command

CCL AND THE COMMAND DECODER

CCL uses its own copy of the Command Decoder instead of the copy
available from the monitor. Thus, the CCL Command Decoder has several
options not available via standard USR calls to the 05/8 Command
Decoder, e.g., multiple default extensions.

3.7

USEFUL LOCATIONS IN BATCH

BATCH will run whenever bit 0 of location 07777 is a 1. The user may
wish to access the following useful locations in BATCH. The locations
are in the highest memory field available to 05/8:
BATERR = 7000

JMP here to abort BATCH.

BATOUT = 7400

JMS here to print character

in AC in BATCH log.
BATSPL = 7200

3. 8

JMS here to permi t spooling
with default extension in AC.

ceL TABLES

A description of all tables used by CCL is included in the file CCL.PA
supplied to all users of 05/8 version 3.

3-10

CHAPTER 4
USING DEVICE HANDLERS

A device handler is a system subroutine that is used by all parts of
the OS/8 system and by all standard system programs to perform I/O
transfers. All device handlers are called in the same way and they
all perform the same basic operation: reading or writing a specified
number of 128 word records beginning at a selected core address.
These subroutines effectively mask the unique characteristics of
different I/O devices from the calling programJ thus, programs that
use device handlers properly are effectively wdevice independent-.
Changing devices involves merely changing the device handlers used for

I/O.
OS/8 device handlers have another important feature. They are able to
transfer a number of records as a single operation. On a device like
DECtape this permits many bks of data to be transferred without
stopping the tape motion.
On a disk, a single operation could
transfer an entire track or more.
This capability significantly
increases the speed of operation of OS/8 programs, such as PIP, that
have large buffer areas.
N~E

The word "record w is defined to mean 128
words of data;
thus, an OS/8 block
consists of two 128 word records.

4.1

CALLING DEVICE HANDLERS

Device handlers are loaded into a user selected area in memory field 0
by the FETCH function. FETCH returns in ARG(l) the entry point of the
handler loaded. The handler is called by performing a JMS to the
specified entry point address. It has the following format:
COF N
CIF 0
JMS I ENTRY
ARG(l)
ARG(2)
ARG(3)

/WHERE N IS THE VALUE OF THE CURRENT
/PROGRAM INSTRUCTION FIELD TIMES 10 (OCTAL)
/DEVICE HANDLER ALWAYS IN FIELD 0
/FUNCTION CONTROL WORD
/BUFFER ADDRESS
/STARTING BLOCK NUMBER

4-1

/ERROR RETU~~
/NORMAL RETU~~ (I/O TRANSFER COMPLETE)

JMP ERR

ENTRY 0

/ENTRY CONTAINS THE ENTRY POINT OF THE
/HANDLER, DETERMINED WHEN LOADED BY FETCH

As with calls to the USR, it is important that the data field is
to the current program field before teldevice handler is called.
exit from the device handler, the data field will remain set to
current program field.
ARG(l) is the
information:

function

control

word,

and

contains

the

set
On
the

following

Contents

Bits
Bit 0

o for an input operation,
operation.

Bits 1 to 5

The number of 128 word records
to
be
transferred.
If bits 1-5 are zero and the
device is non-file structured (i.e., TTY,
LPT, etc.) the operation is device dependent.
If the device is file structured
(SYS,
DECtape, disk, etc.), a read/write of 40
(octal) pages is performed.

Bits 6 to 8

The memory field in which the transfer is
be performed.

Bits 9 to 11

Device dependent bits, can be left zero.
Currently only bit 11 is used, on DEC tape
bit 11 determines the direction in which the
tape is started.
If bit 11 is 0, the tape
starts in reverse. If bit 11 is 1, the tape
starts forward.
All other handlers ignore
these bits at present (except TM8E and TA8E).

for

output

N~E

Starting forward saves time as long as
the block number, ARG(3), is about seven
or more blocks greater than the number
of the block at which the tape is
currently positioned.
ARG(2) is the starting location of the transfer buffer.
ARG(3) is ~e number of the block on which the transfer is to begin.
The user program initially 'determines this value by performing a
LOOKUP or ENTER operation.
After each transfer the user program
should itself add to the current block number the actual number of
blocks transferred, equal to one-half the number of 128 word records
specified, rounded up if the number of records was odd.
There are two kinds of error returns: fatal and non-fatal.
When an
error return occurs and the contents of the AC are negative, the error
is fatal. A fatal error can be caused by a parity error on input, a
write lock error on output, or an attempt to write on a read-only

4-2

device (or vice versa • The meaning can vary from device to device,
but in all cases
t
is serious enough to indicate that the data
transferred, if any, s invalid.
When an error return occurs and the contents of the AC are greater
than or equal to zero, a non-fatal error has occurred. This error
always indicates detection of the logical end-of-file.
For example,
when the paper tape reader handler detects the end of a paper tape it
inserts a CTRL/Z code in the buffer and takes the error exit with the
AC equal to zero.
While all non-file structured input devices can
detect the end-of-file condition, no file structured device can;
furthermore, no device handler takes the non-ratal error return when
doing output.
The following restrictions apply to the use of device handlers:
1.

If bits 1 to 5 of the function control word, ARG(l), are
zero, a transfer of 40
(octal) pages or an entire memory
field is indicated. Care must be used to ensure that the
handler is not overlaid in this call. This only applies to
file-structured handlers.

The user program must never specify an input into locations
07600 to 07777, 17600 to 17777, or 27600-27777, or the
page(s) in which the device handler itself resides.
In
general, 7600-7777 in every memory field are reserved for use
by system software. Those areas should be used with caution.

Note that the amount of data transferred is given as a number

128

word

records,

exactly

one

half of a~ OS/8 block.

Attempting to output an odd number of records can change the
contents of the last 128 words of the last block written.
For example, outputting 128 words to a block on the RK8 disk
causes the last 128 words of the block to be filled with
zeroes.
4.

The specified buffer address does not have to begin at the
start of a page. The specified buffer cannot overlap fields,
rather the address will "wrap around" memory; For example, a
write of 2 pages starting at location 07600 would cause
locations 07600-07777 and 00000-00177 of field 0 to be
written.

If bits 1-5 of the function control word ARG(l) are zero, a
device-dependent operation occurs. Users should not expect a
40-page (full field) transfer of data. The CLOSE operation
of the USR calls the handler with bits 1-5 and 9-11 of the
function control word O. This condition means
'perform any
special
close
operations desired'. Non-file structured
handlers which need no special handling on the conclusion of
data transfers should treat this case as a NOP. Examples of
usage of such special codes:
LPT - perform a form feed
CSAn, MTAn - write two file marks

4-3

4.2

DEVICE DEPENDENT OPERATIONS

This section describes briefly the operation of certain standard OS/8
device
handlers,
including
normal
operation,
any
special
initialization operations for block 0, terminating conditions, and
response to control characters typed at the keyboard.
Further
information on device handlers can be found in Chapter 5.

4.2.1

l-Page Terminal (TTY)
1.

(AS33)

Normal Operation
This handler inputs characters from the terminal keyboard and
packs them into the buffer or unpacks characters from the
buffer and outputs them to the console terminal.
On input, characters are echoed as they are typed. Following
a carriage return, a line feed character is inserted into the
input buffer and printed on the terminal.

Initialization for Block 0
None.

Terminating Conditions
On input, detection of a CTRL/Z causes a CTRL/Z (octal code
232) to be placed in the input buffer, the remaining words of
the buffer to be- filled with zeros, and a non-fatal error to
be returned.
On output, detection of a CTRL/Z character in
the output buffer causes output to be terminated and the
normal return to be taken.
There are no fatal errors
associated with the l-page terminal handler.

Terminal Interaction
CTRL/C forces a return to the Keyboard Monitor.
CTRL/
forces an end-of-file on input (see 3). CTRL/O terminates
printing of the contents of the current buffer on output.

4.2.2

High-Speed Paper Tape Reader (PTR)
1.

Normal Operation
This handler inputs characters from the high-speed paper tape
reader and packs them into the buffer.

Initialization for Block 0
The handler prints an up-arrow (t) on the terminal and waits
for the user to load the paper tape reader. By typing any
single character (except CTRL/C) the user initiates reading
of the paper tape.

4-4

~;OTE

On some terminals, up-arrow is replaced
,r,) character.

by the circumflex

Terminating Conditions
Detection of an end-of-tape condition, indicated by the
failure to get a character in a specified period of time,
causes a CTRL!Z to be entered in the buffer, the remaining
words of the buffer to be filled with zeros, and a non-fatal
error to be returned. Attempting output to the paper tape
reader causes a fatal error to be returned.

Terminal Interaction
Typing CTRL/C forces a return to the Keyboard Monitor.

4.2.3

High-Speed Paper Tape Punch (PTP)
1.

Normal Operation
This handler unpacks characters from the
punches them on the paper tape punch.

output

buffer

and

Initialization for Block a
None.

Terminating Conditions
Attempting to input from the paper tape punch causes a fatal
error
to be returned.
There are no non-fatal errors
associated with this handler.

Typing CTRL/C forces a return to the Keyboard Monitor, but
only when actual punching has begun, or if tC is typed before
punching commences. If the punch is off line,
tC is only
effective immediately before punching would begin.

4.2.4

Line Printer (LPT)

(LPSV)

Normal Operation
This handler unpacks characters from the buffer and prints
them on the line printer.
The characters horizontal tab
(ASCII 211)
causes sufficient spaces to be inserted to
position the next character at a "tab stop" (every eighth
column, by definition). The character vertical tab
(ASCII
213) causes a skip to the next paper position for vertical
tabulation if the -line printer- hardware provides
that
feature.
The character form feed (ASCII 214) causes a skip
to the top of the next page. Finally, the handler maintains
a record of the current print column and starts a new line
after 80 or 128 columns have been printed.
This handler
4-5

functions properly only on ASCII data. The handler for the
LS8E line printer handler utilizes the expand~d character
capability of the printer.
If a 216 (CTRL/N) character
appears anywhere in a line of text, the entire line is
printed in the expanded character mode. The 216 must be used
on a line-by-line basis.
2.

Initialization for Block 0
Before printing begins, the line printer handler
form feed to sp~ce to the top of the next page.

issues

Terminating Condition
On detection of a CTRL/Z character in the buffer, the line
printer handler issues a form feed and immediately takes the
normal return. Attempting to input from the line printer
forces a fatal error to be returned. A fatal error is also
returned if the line printer error flag is set. There are no
non-fatal errors associated with the line printer handler.

Terminal Interaction
Typing CTRL/C forces a return to the Keyboard Monitor.

Patching the LPSV Handler
The following patches are available for the LPSV line printer
handler.
reI. lac 0: set to -printer width-l (i.e. set to -121(octal)
for an 80 column line
printer)
reI. lac

1: set to 4

the
for
LV8E
printers
for the LPOE and
printers

set to 14
reI. lac 2: set to -40

LS8E

to convert lower case to
upper case
if your printer can print
lower case

set to 0

4.2.5

line

Cassettes
1.

Normal Operation
This handler performs character I/O between the cassettes and
the buffer.
It treats cassettes as a non-file structured
device. Data appears on cassette in 192-byte records.

Initialization for Block 0
On input the cassette is rewound. On output the cassette
rewound and a file gap is written.

Terminating Condition

4-6

end-of-file on input is a software error.

Terminal Interaction

Typing C':'RL/C forces a return to the Keyboard
5.

Special Codes (device dependent features)
If the handler is called with bits 1-5 of the function word
The meaning of these codes
are as follows;

=0, then bits 10-11 are examined.

o
1

2
3

write a file gap
rewind also, then write a file gap if bit 0=1
space backwards one record
skip one file (direction depends on bit 0)
NOTE
The handler neither reads nor writes
standard files.
It is merely a paper
tape replacement. It writes raw data
(organized into 192-byte records) onto
the cassettes starting at the beginning;
and then later reads it back.

The source is already in OS/8 BUILD format. The handler has only two
entry points (for drives A and B of a controller). The decision as to
which controller it uses is made at assembly time by changing the
symbol code. The result is as follows:
CODE

DEVICE NAME

HANDLER

DEVICE CODE

TA8A

A:CSAO
B:CSAI

TA8B

A:CSA2
B:CSA3

TA8C

A:CSA4
B:CSAS

TA8D

A:CSA6
B:CSA7

The handler has the internal device code of 27 (see Table 2-12
Chapter 2 of the OS/8 HANDBOOK. The handler is two pages long.

4.2.6

Card Reader (CDR)
1.

Normal Operation
This handler reads characters from the card reader and packs
them into the input buffer. Trailing spaces (blank col~~~s)
on a card are deleted from input.
The handler can accept
only alphanumeric format data on cards (the DEC029 standard
card codes are used).

4-7

Initialization for Block 0
None.

Terminating Conditions
A card which contains an underline character in column 1 (an
0-8-5
punch)
with the rema~n~ng columns blank is an
end-of-file card. In addition, after reading each card the
handler checks to see if a CTRL/Z was typed at the keyboard.
After either an end-of-file card or a CTRL/Z being typed, a
CTRL/Z is inserted in the buffer, the remaining words of the
input buffer are filled with zeros, and a non-fatal error is
returned.
Attempting to output to the card reader causes a
fatal error to be returned.

Terminal Interaction
Typing CTRL/C forces a return to the Keyboard Monitor.
Typing CTRL/Z forces an end-of-file to occur (see 3.).

4.2.7

TM8-E Handler
1.

Normal Operation:
When the handler is used in its normal mode, single-file
mode, magtapes may consist of exactly one file. It starts at
the beginning of the tape and consists of consecutive records
until an end-of-file mark (EOF) is reached. In this sense, a
magtape is similar to one big paper tape. This is the same
way that OS/8 currently treats cassettes.
Since the capacity of magtapes is so big, provisions have
been made for storing multiple files per tape. In such a
structure, several files may exist on one magtape. They are
unlabeled and are separated from each other by a single file
mark. The last one is followed by two file marks.
Each
'file' looks like a paper tape.
It is referenced in a
non-file structured manner.
The magtape handler must be
altered first to work in file mode. Then the magtape must bepositioned to exactly the correct spot where· the read or
write operation will commence.
This may be done with any
program using the auxiliary capabilities of the magtape
handler (described below), or the positioner program, CAMP.
To read a file, the handler must be positioned to just before
the first data record of that file. To write file #1, rewind
the tape (i.e., be at BOT). To write file In, (n>l) the
handler should be positioned after the (n-l)st file mark on
the tape. Previous file n and all files past it then become
unreadable (non-existent).
A.

Device-Dependent Capabilities:
The TM8-E handler has several auxiliary features which
may be invoked by a user program which calls the handler
in a device-dependent manner. These features all rely on
the contents of bits 9-11 of the function word (argument
1 of the handler call) and some require argument 3 in
addition.

4-8

These features are brought to life whenever the handler
called ..... ith a page count of a (bits 1-5 of the
function word). Call bits 9-11 of the function word, the
Special Function Register (SFR) for short, and also refer
to bit 0 of the fQ~ction word as the direction bite
If
the page count is not 0, the contents of the SFR is
ignored.

If the page count is 0, then the SFR together with the
direction bit (and possibly argument 3) determine what
special function to perform, as follows:
OPERATION

CLOSE.

Rewind.

Space forward/reverse records.
The direction to
space is determined by the direction bit (0 means
space forward, 1 means space reverse). The negative
(two's complement) of the number of records to space
over is given by argument 3 of the handler call.
(-1
means space past one record, 0 means 4096 records.)
The error return is taken if either a file mark or
BOT is encountered. In such cases, you would be left
positioned at the beginning of a file.

Space forward/reverse files. The direction to space
is determined by ~~e direction bit (0 means space
forward, 1 means space reverse). The negative of the
number of file marks to space past is given by
argument 3 (-1 means space past one file mark,
0
means 4096 file marks). In reverse mode, the tape is
left positioned at the end of a file,
an error is
given if BOT is encountered. In forward mode, the
tape is left positioned at the beginning of a file.
If EOD is reached, the handler automatically performs
a backspace record to leave you between the two file
marks; no error is given.

Rewind the unit and put drive off-line.

Write a single EOF.

Special read/write function.
The direction bit
(as
usual) determines read or write
(0 means read, 1
means write). The specified
I/O
operation
is
performed
between
the user's buffer (start is
specified by argument 2) and the very next magtape
record.
Only one record is transferred and the
user's buffer must be large enough to contain it.
The record length is specified by the negative of
argument 3 (in words). 0 means a record length of
4096.

Unused .. Reserved for future use ..
currently acts as a No-OP.

Write two EOF's.

In each case, the unit affected is determined
point.

4-9

specified:

the

handler

entry

Other Common Operations:
(a) To backspace n files, use special code 3 to pass over
n+l file marks backwards, then use special code 2 to
advance (forward) over one record (EOF) ignoring the
EOF error.
(b) To advance to EOO, first perform a backspace of one
record (or perform a rewind to play safe) then use
special code 3 to advance over 4096 files in the
forward direction (argument 3=0).

Special Handling for Block 0
If the handler is called to read or write block 0, it will
first perform a rewind. This feature can be patched out if
desired by altering relative location 1 from a 0 to a 1. This
altered handler should be operating in file mode. The
original handler should be operating in single-file mode.
A.

Special Handling for CLOSE:
A close operation is signaled to the handler by calling
it with a function word which has a page count of 0 (bits
1-5) and which has bits 9-11 all zeroes. This is how the
USR CLOSE operation calls the handler (OS/8 V3 only.
This causes the handler to write two successive file
marks on the tape. Two successive EOF's is the software
indication of end-of-data (EOD).

Restrictions:
In single-file mode, should not have more than 4095
blocks because on trying to write the 4096th block, the
handler will think it's writing block 0 and perform a
rewind.
This restriction does not apply when using the
handler in file-mode: but beware, some cusps, such as
PIP, are suspected to behave strangely on block 4096 of
non-file-structured devices.

Terminating Conditions
None.

Keyboard Interaction:
Typing tC on the keyboard while the handler is in operation
causes the handler to abort and return to the 05/8 keyboard
monitor via location 7600. Such action is ill-advised since
it leaves the magtape without an end-of-file indicator.

Error Conditions:
On a hard error, the handler takes the error return (with a
negative AC) and the AC contains the contents of the main
status register, as follows:

4-10

Bit on

Xeaning

Error flag
Tape rewinding

Select error
Parity error (vertical, longitudinal, or

C~)

5
6

7
8
9
10
11

4.2.8

EOF
Record length incorrect
Data request late
EaT
File protect
Read compare error
Illegal function

File-Structured Devices
1.

Normal Operation
(DECtape, LINCtape, TD8E DECtape, DF32, RF08, and RK8, RK8E)
These handlers transfer data directly between the device
the buffer.

and

Initialization for Block 0
None.

Terminating Conditions

A fatal error is returned whenever the transfer causes one of
the error flags in the device status reqister to be set. For
example, a fatal error would result if a parity error
occurred on input, or a write lock error occurred on output.
The device handlers generally try three times to perform the
operation before giving up and returning a fatal error.
There are no non-fatal errors associated with file structured
devices.

Terminal Interaction
Typing CTRL/C forces a return to the Keyboard Monitor.
NOTE
The system device handler
respond to a typed CTRL/C.

4.2.9

does

NOT

TD8E DECtape

TD8E DECtape is the new accumulator transfer DECtape. Since 05/8 is a
noninterrupt driven system, TD8E DECtape has data transfer rates
equivalent to those for TCOS DECtape; however, the interrupt should
never be used with the TDSE. Device handlers for T08 DEC tape are
supplied as a standard part of 05/8. Each pair of drives (0, and 1,' 2
and 3, etc.) requires a 2-page device handler. Thus, to have all

4-11

eight TD8E drives in the system at one time will require four separate
handlers.
Thus for TD8E, it is wise to restrict usage to those units
that physically exist. Also, the tape drives are hardwired to select
one of two possible unit numbers: thus, the first pair of drives
installed must be called units 0 to 1. Any others numbers will cause a
SELECT error.
In this case, the computer hangs until the correct
drive is selected.

4.2.10

KL8E Terminal Handler

Listed are the features of the KL8E
conditional are marked by an asterisk:

handler.

Those

that

are

It reads a line at a time. Whenever the user types CR, it
enters CR, LF into the buffer: it echoes CR, LF: and then
pads the remainder of the buffer with nulls and returns to
the calling program. The characters get put into the buffer,
one character per wQrd. Thus every third character is a null
as far as 05/8 is concerned.

RUBOUT deletes the previous character. It echoes as either a
back slash (\> or as the character rubbed out, depending on
assembly parameters. RUBOUT at the beginning of a line acts
as tU.

CTRL/U echoes as tU and erases the current line, allowing the
user to retype it.
(It also echoes CR, LF.) The buffer
pointer is reset to the beginning of the buffer.

CTRL/Z echoes as tZ (followed by CR, LF) and signals
end-of-input.
The tZ enters the buffer and the remainder of
the buffer is padded with nulls. The error return is taken
with a positive AC (non-fatal error).

Nulls are ignored.

*6.

The altmode characters (octal 175 and 176) are
escapes (octal 33).

*7.

Lower-case characters typed may be automatically converted to
upper case.

CTRL/C echoes as tC and returns
monitor via location 07600.

On output:

control

converted

the

keyboard

(either normal output or when echoing input)

CTRL/C on keyboard echoes as tC and returns
keyboard monitor via location 7600.

CTRL/O on keyboard stops further echoing. All echoing ceases
(through possibly many buffer loads) until either the handler
is reloaded into core or the user types a character other
than to on the keyboard. Not operative during input.

tS causes the handler to stop sending to the terminal.
No
characters are lost and outputting resumes when a to is
typed.
ts and to do not echo.
These characters are

4-12

control

the

operative only upon output. On input, they are treated like
any other input characters. This is very useful on high
speed CRT displays.

Nulls are ignored.

*5.

Lower case ~~aracters may be optionally printed as upper case
and flagged with an apostrophe.

*6.

Tabs may be handled in one of three manners:
a.

Output as actual tabs,

Output as actual tab followed by padding of two rubouts,

Output as the correct number of spaces to bring the
to the start of the next tab stop.

text

Whenever the output line reaches the end of the physical line
(length set at assembly time), the handler automatically
performs a carriage-return line-feed.

*8.

The escape character (octal 33) prints as a dollar sign.

*9.

The handler may be set to delay about 16 rns after typing any
character (specified at assembly time), for example, line
feed.

*10.

Control characters are printed as their corresponding
preceded by an up-arrow. Thus CTRL/K prints as tK.

4-13

letter

CHAPTER 5
RECONFIGURING THE 05/8 SYSTEM

It is some~1mes necessary to construct an OS/8 system from scratch r or
to make a new peripheral device available to 05/8. Both of these tasks
are a part of reconfiguring the 05/8 system.
05/8 BUILD r which is
described in detail in Chapter 2 of the 05/8 HANDBOOK r allows the user
quickly and easily to build a new system or to alter the device
complement of an existing system.

5.1

WRITING DEVICE HANDLERS

A device handler is a page-independent subroutine one or two pages
long.
The device handler must run properly in any single page or two
contiguous pages in field 0 (except 0000 to 0177 or 7600 to 7777). All
device handlers have the same calling sequence:

CDF N
elF 0
JMS I ENTRY
FUNCTION

BUFFER
BLOCK
ERROR
NORMAL

IN IS CURRENT FIELD TIMES 10 (OCTAL)
/DEVICE HANDLER LOCATED IN FIELD 0
/ENTRY IS DETERMINED BY SR "FETCH"
IFUNCTION IS BROKEN DOWN AS FOLLOWS:
/BIT 0 - 0 FOR READ
/BIT 0 = 1 FOR WRITE
/BITS 1 TO 5 = NUMBER OF PGS TO TRANSFER
/BITS 6 TO 8 = FIELD FOR TRANSFER
/BITS 9 TO 11 = DEVICE DEPENDENT BITS
/CORE ADDRESS OF TRANSFER BUFFER
/BLOCK NUMBER TO START TRANSFER
/ERROR RETURN, AC)=O MEANS END-OF-FILE
AC(O MEANS FATAL ERROR
/NORMAL RETURN

The device handler reads or writes a number of 128 word records
beginning at the selected block. In general, device handlers should
conform to the following standards:
1.

On normal return from a device handler the AC is zero and the
DATA FIELD is always restored to its original entry value.

Although the starting block number has true significance only
for file structured devices r handlers for non-file structured
devices can check the block number and perform initialization
if the block number is zero. For example, the line printer
handler outputs a form feed before 'printing when
the
specified block number is zero.

Handlers should be written to be as foolproof as possible
checking for the most common errors in the calling program.

5-1

Examples of typical user errors are: calling handler with
non-zero AC (always perform a CLA in the handler): trying to
read on a write only device, or trying to write on a read
only device (gives a fatal error return): specifying 0 pages
to be transferred (accept as meaning no actual transfer is to
take place): or attempting to access a nonexistent block
(gives a fatal error return).
4.

Device handlers normally check to see if a CTRL/C (ASCII 203)
has been typed at the system console by the user.
If one
has, the handler aborts I/O and JMP's to location 7600 in
field O. The seven low order bits of the keyboard should be
checked for a 3 so as to allow parity terminals. KRS should
be used over KRB so that any paper tape in the reader will
not be advanced if its character is not tC.

Device handlers should be able to detect standard error
conditions
like
checksum
or parity errors.
Whenever
possible, several attempts to perform the transfer should be
made before aborting I/O and taking the error exit. In
addition, when operator intervention is required, the handler
would normally wait for the action rather than take a fatal
error exit. For example, if the paper tape punch is not
turned on, the PTP handler waits for the punch to be turned
on.

By convention, in any handler for a device (like DECtape)
that can search either forward or backward for a block, Bit
11 of the function word (one of the device-dependent bits)
controls the starting direction of the search. Bit 11 is a 1
if the starting direction is forward and a 0 if it is
reverse.
The other two device dependent bits are not
assigned any significance at the present time.

Remember that the user specifies a multiple of 128 words to
transfer, whereas the transfer starts at the beginning of a
128 or 256 word block. This means that the handler must
provide that capability of reading or writing the first half
of a block. Writing the first half of the block causes the
contents of the second half of the block to be altered. For
example, writing 128 words to the RK8 disk (256 word blocks)
causes the second half of the block to be filled with zeroes.
This is usually done by the hardware controller.

The entry point to a two page device handler must be
first page.

A number of handlers (maximum of 15 decimal) can be included
in the one or two pages of code. Where more than one handler
is included in a single handler subroutine, the handlers are
called co-resident. Co-resident handlers are always brought
into core together. For example, all eight DECtape handlers
fit
into
one pageJ
hence, the DECtape handlers are
co-resident. One restriction on co-resident handlers is that
if they are two pages long all entry points must be in the
first page"';

10.

The USR, while doing file OP'"·' rations , maintains in core the
last directory block reac,". n order to reduce the number of
directory reads necessary. . '!1e proper functioning of this
feature depends on the fact that every handler for a

5-2

the

file-structured device on a single system has a unique entry
point relative to the beginning of the handler. The relative
entry points currently assigned for file structured handlers
are:
Relative Entry Points

Device Handlers
System Device Handler
DECtape, LINCtape or TD8E DECtape
RKAO
RKAl
RKA2
RKA3

RK08 or DF32
Reserved for user
11.

7
10 to 17
20'
21
22
23
24
40 to 67

If the device is block oriented (such as DECtape, LINCtape,
or Disk), then the handler transfers data directly with no
alteration. However, if the device is character oriented
(such as a paper tape reader, Teletype, or line printer), the
handler is required to pack characters into the buffer on
input and unpack them on output. The standard 05/8 character
packing format puts three a-bit characters into two words as
follows:
I ~ " ." . ,.

WORD 1
WORD 2

.. ~ ~

CHARACTER 3
BITS 0-3

CHARACTER 1

I~O~

CHARACTE"R 3
BITS 4-7

I--

CHARACTER 2

For example, the 3 characters IABCI would be
words as follows:

packed

into

Word 1: 6301
Word 2: 1702
When packing characters on input, the character CTRL/Z (octal
232) is inserted at the logical end-of-file (for example, at
the end of the tape in the paper tape reader handler).
Following CTRLh) the remaining words of the input buffer
should be zeroed.
12.

A close operation should be performed by non-file structured
handlers if bits 1-5 and 9-11 of the function word are O.

The device handler, whether one or two pages long, must be completely
page independent:
it must be capable of executing in any page(s} in
field 0, except page 0 and 7600 to 7777. Page independent code can
have no address constants. Writing one page handlers is relatively
easy, since the addressing structure of the pop-a is essentially page
independent. Writing page relocatab1e code for two pages, however, is
considerably more difficult, as the two pages must communicate.
The
usual technique utilized in writing two page handlers is to include
some initialization code which includes a JMS.
This replaces that
location by an address on the page the handler was loaded on. Using
this, the handler can then determine where the relevant pieces of code
are in core.

5-3

As an example, the following is the initialization procedure performed
the TD8E DECtape routine. This is by no means the only technique
that is possible, but it is a workable solution.

*200
/EXECUTED CODE
JINIT,

JMP INIT

/START INITIALIZATION

•

INIT,
BASE,

JMS.
TAD CRDQAD
SPA
JMP NXINIT
TAD INIT
DCA CRDQAD
ISZ .-1
ISZ BASE
JMP BASE

/FOUND OUT WHERE WE ARE.
/INIT GETS ADDRESS OF BASE
/NEGATIVE TERMINATES LIST
/INITIALIZE SECOND PAGE
/NOW UPDATE THE LIST OF
/ADDRESS DEPENDENT LOCATIONS
/POINT TO NEXT ELEMENT
/NEXT INPUT VALUE
/LOOP OVER INPUT TABLE.

CRDQAD,
CINIT2,
CSELCT,
CXUNIT,
BUFF,

R4LINE-BASE
INIT2-BASE
SELECT-BASE
XUNIT-BASE
4000
•
•

/THESE ARE ALL POSITIVE DIFFERENCES,
/SINCE THE ROUTINES INDICATED ARE
/IN THE SECOND AGE. AFTER
/INITIALIZATION~ CRDOAD POINTS TO
/THE ACTUAL ADDRESS OF R4LINE, ETC.
/THE 4000 IN BUFF TERMINATES
/TBE FIRST INITIALIZATION.
/MORE PAGE INDEPENDENT CODE

•

NXINIT,
BASE2,

INIT2,
INIT3,

JMS I CINIT2 /INITIALIZE SECOND PAGE
DCA JINIT
/CLEAR OUT JINIT. NO MORE
JMP JINIT
/RELOCATING IS NEEDED UNTIL THE
/HANDLER IS LOADED INTO CORE GAIN.
*400
/SECOND PAGE OF HANDLER

/ADDRESS OF BASE2 GOES HERE

TAD CTRY3
SNA
JMP I INIT2
TAD INIT2
DCA CTRY3
ISZ .-1
ISZ INIT3
JMP INIT3

/A 0 TERMINATES THIS LIST
/ADD VALUE OF BASE2 TO LIST
/PUT BACK INTO LIST
/NEXT LOC. TABLE

•
•
CTRY3,
CRWCOM,
XBUFF,

TRY3-BASE2
/THIS LIST GETS VALUE OF BASE2
TRWCOM-BSSE2 /ADDED IN TO POINT TO THE REAL
o
/ROUTINE.

5-4

Writing 2 page independent code can be expensive in terms of core
required.
The routines should be set up in such a way as to minimize
communication between the two pages.
Some other points to keep in
mind are:
1.

Relocation code is once-only code. It is done once when the
handler is loaded and need never be done again until the
handler is re-loaded from the system device.
For this
reason, the relocation code can be placed in a buffer area or
setup in temporary scratch locations which are later used as

temporarj storage.

5.2

A useful hint is that a JMP into the next page of code is not
required.
The code can just as easily fall through 377 into
400. This may save a few locations of relocation code.

Useful techniques for writing 2-page handlers can be found in
the source of the KL8E handler.

INSERTING DEVICE HANDLERS INTO OS/8

After the handler has been written and thoroughly debugged as a
stand-alone routine, it can be integrated into the 05/8 Monitor, where
it will become a resident device handler.
To accomplish
the
integration, use 05/8 BUILD, described thoroughly in the BUILD section
in Chapter 2 of the 05/8 HANDBOOK.
Notes for writing system handlers system handlers may be integrated
into BUILD just like non-system handlers with the following additional
notes:
1.

Body of system handler should be origined to 200 but must
start with a 2 BLOCK 7. Entry point must be at relative
location 7 (corresponds to location 7607).

Name of system handler must be SYS.

Each handler entry point has an a-word handler
associated with it. The following additions. apply:
a.

block

word 5: bits 9-11 should normally be O.
If the device can have multiple platters
(like RF08)
then this field specifies maximum number of platters
allowed. Each platter above first bumps internal DCB
code by 1.
word 6: bit 0=1 means system device is two pages long.
The second page is origined into 400 but resides in
field 2 location 7600. Bit 1=1 if entry point is SYS.
Bit 2=1 if entry point is coresident with SYS.
word 7:

must be 0

word 10: number of blocks in device.
Immediately
following the header records is the code for the
deviceis bootstrap.
This is preceded by minus ~~e
number of words in the bootstrap. No origins may appear
in this code.
It must be less than 47 locations long.

5-5

APPE~mIX

OS/8 FILE STRUCTURES

A.l

FILE DI?~CTORIES

Blocks 1 through 6 on all file structured devices are reserved for the
file directory of that device.
Six blocks are always allocated,
though all are not necess~rily active at any given time. To minimize
the number of directory reads and writes necessary, OS/8 fills one
directory block completely before overflowing onto a second block=
Thus the user with only a few files can perform directory LOOKUPs and
ENTERs faster than one with many files.
The directory blocks are each structured according
format:
ENTRY

the

following

Locations 0 through 4 of each directory block are called
header.

the

segment

MINUS THE NUMBER OF ENTRIES
IN THIS SEGMENT
THE STARTING BLOCK NUMBER

! OF THE FIRST FILE IN THIS

I SEGMENT

,
2

LINK TO NEXT SEGMENT-ZERO
IF NO NEXT SEGMENT

FLAG WORD-POINTS TO LAST WORD
OF TENTATIVE FILE ENTRY IN
THIS SEGMENT
DIRECTORY SEGMENTS ARE ALWAYS
LOADED INTO LOCATIONS 11400
TO 117777 BY THE USR~ THIS
POINTER IS EITHER 0 OR BETWEEN
1400 TO 1777.

MINUS THE NUMBER OF
ADDITIONAL INFORMATION WORDS
THE NUMBER OF ADDITIONAL
INFORMATION WORDS SPECIFIED
MUST BE THE SAME IN ALL
DIRECTORY SEGMENTS

BEGINNING OF FILE ENTRIES

J
377

END
OF DIRECTORY BLOCK
____________________________

(8)1~

A-I

A.l.1

Directory Entries

There are three types of file directory entries. They are PERMANENT
FILE ENTRY, EMPTY FILE ENTRY, and TENTATIVE FILE ENTRY. A permanent
file entry appears as follows:
Contents

Location

~Jotes

FILE :~ANE
CHARAC':'ER "-"
FILE ~A}!E
FILE NAHE
I
1
CH.P~RACTER 4
! THE FILE KANE AND EXTENSION
CHARF.CTER 3
---------F--I-L-E-I'-;P.1-lE----l / F.RE PACKED IN SIXBIT ASCII
FILE NF"l-m
(i.e., "A" would be .0'1)
2
CHARAC':'ER 5
CHF.RP~CTER 6
!I

FILE NANE

CHA~ACTER

~.---.-

-I

I
FILE EXTE!-:SION FILE EXTENSION
CHARACTER 2
i j
CHARAC':'ER 1

1< N, THE

~UMBER OF ADDITIONAL
INFORNATION WORDS, IS GIVEN
ADDITIONAL
~: BY WORD 4 OF THE DIRECTORY
HEADER.
\.-.
INFORHATION
~
WORD 4 OF THE ENTRY
-:-'/____~W~O~R~D~S~___________~I'I, IS EITHER 0 OR THE CREATION
I
' I DATE OF THE FILE.
I

-4)

N+3+-______________________________

N+41 MINUS FILE LENGTH IN BLOCKS
NOTE
If word 3 is zero, the given file has
null extension.

An empty file entry appears as follows:
Location

Contents

ENTRY IS ALWAYS

MINUS THE NUMBER OF BLOCKS
IN THIS EMPTY FILE

.0'~g~

A tentative file entry appears as a permanent file entry with a length
of zero.
It is always immediately followed by an empty file entry.
When the tentative file is entered in a directory, location 3 in the'
segment header becomes a pointer to this entry. The CLOSE function
inserts the length word of the tentative file entry, making it a
permanent file,
and adjusts the length of the following empty file
entry (deleting that entry if the length becomes zero).
Whether or not there is a tentative file open on any device is
determined by examination of bits 9 to 11 of the system Device Control
Word Table (see section B.3.5) not the contents of' location 3 in the
segment header.
Zeroing these bits in the Device Control 'Word Table
makes the active tentative file on the device inactive. The next time
that the system has to write the directory segment, the inactive

A-2

tentative file ent~J is removed. ~he distinction between active and
inactive tentative files is marie so that 05/8 can avoid spending the
time required to perform an extra read and write of the device
directory.

A.l.2

Number and Size of 05/8 Files

All files on an 05/8 device must occupy a contiguous group of blocks
on the device. The length of any file is indicated in its directory

entry; and the starting

block

the

file

deduced

adding

together word 1 of the segment header and the lengths of all files
whose entries precede it in the directory segment.
Each directory segment must have enough unused words at the end to
accommodate a permanent file entry (N+5 words, where N is the number
of Additional Information Words). Thus, if N is the number of
Additional Information Words the maximum number of permanent file
entries in anyone segment is:
256-7 -

MIN = (

244-N

(N+5)

] =
N+7

[-]

N+7

with N=l, MAX=40, and MIN=30. Since there are six segments in the
directory, the maximum number of files possible (with N=l) would be
240.
Finally, 05/8 devices are limited to 4095 blocks, each block being 256
words long. Thus, the maximum size of any single 05i8 file structured
device is 1,048,320 words. Blocks 0 through 6 of the device are
unavailable for file storage; therefore, the largest possible file is
4088 blocks long, or 1,046,528 words.

A.l.3

Sample Directory

The initial directory written when the OS/8 system is built
follows:

A-3

looks

o
SEGHE~T

HEADER

PEID-!ANENT
FILE
ENTRY

EHPTY
FILE
ENTRY

7776

iJ~70

FILE

,00~~

:,IO

0~~0

7777

r 5

0102

2314

STORAG~

C~~Rm~
~
... i".
J....,

-Y
r>.

;DDITIONAL DIRECTORY SEGr':;ENTS

O:.--JE ADDITIONAL

I:~FORHATIO:-J

'dORD

FILE NAME IS "ABSLDR"

~422

lto

2326

537~

DATE IS 10/31/70

7773

LENGTH IS FIVE BLOCKS

FILE EXTENSION IS .SV

[13
~14

ELOCK -0
18 *

EHPTY FILE
6534

LENGTH IS 12448 (67610)BLOCKS THIS IS DEPENDENT ON THE SYSTEM
DEVICE GSED.
676 IS THE VALUE
FOR A DECTAPE SYSTEM

*This leaves room fer the OS/8 System
Areas.

A.2

FILE FORMATS

There are three different standard
associated system programs:

file

formats

ASCII and Binary files.

Core Image files (.SV format).

Relocatable FORTRAN library files
current example of this format).

used

05/8

and

(LIB8.RL

the

only

NOTE
Binary files can contain either absolute
binary data (i.e., output from PAL8) or
relocatable binary data (i.e., output
from SABR).
A.2.l

ASCII and Binary Files

ASCII and Binary files are packed three characters into two words,
follows:
CHARI~C':'ER

WORD 1

CHARACTER 1

BITS 0-3
CHARACTER 3
BITS 4-7

WORD 2

CHARACTER 2

11
The following conventions are used by OS/8 system programs:

In ASCII files the character NULL (ASCII 000)
is always
ignored. Most programs only examine the low-order 7 bits, in
ASCII files. The parity bit is usually ignored:
do not
assume that this bit is set or that data transfers will
preserve it (image mode transfers, always preserve it).
A-4

In Binary files the binary data must be preceded by one or
more frames of leader/trailer code
(ASCII 200 code). The
first character of binary data must be either 100 to 177
(octal) (an origin setting for absolute binary files), 240 to
257 (octal)
(a COMMON declaration frame for relocatable
binary files), UL 300 (octal), which is an origin setting.
The end of binary data is indicated by one or more frames of
leader/trailer code.

ASCII and Binary files are terminated by a CTRL/Z code (ASCII
232). In binary files, a CTRL/Z code data rather than

end-af-file.

A.2.2

Core Image (.SV Format) Files

A core image file consists of a header by the actual core image.
The
header block is called the Core Control Block. The Core Control Block
consists of the first 128 words of the 256 word block reserved for
that purpose.
The second 128 words are unused. The Core Control
Block is formatted as follows:

Notes

Contents

Location

CORE CONTROL BLOCK

l1INUS THE NUMBER OF CORE SEGr-lENTS

I
I

62N3 WHERE N IS THE
t-- STARTING
FIELD

CDF CIF (STARTING FIELD)
~----------------------------------~
STARTING ADDRESS
JOB STATUS

~10RD

CONTROL DOUBLE WORDS

2K +3
377

J (K IS THE i-JUMBER OF

A-5

CORE SEGHENTS)
REMAINDER OF BLOCK
IS GNUSED

The format of the Job Status Word is as follows:
Meaning

Bit Condition
Bit 0=1

File does not load into locations 0
in field O.

1777

Bit 1 = 1

File does not load into locations 0
in field 1.

1777

Bit 2 = 1

Program must be reloaded
restarted.

Bit 3 = 1

Program never uses above SK. This
when Batch processing is active.

Bit 10 = 1

Locations 0 to 1777 in field 0 need not be
preserved when the Command Decoder is called.

Bit 11 = 1

Locations 0 to 1777 in field 1 need
preserved when the USR is called.

before

can
is

be
used

not

The Core Segment Doublewords control the reading and writing of the
associated areas of core. The format of each entry is as follows:
Contents

Location

CORE ORIGIN

Notes
l-1ULTIPLE OF

~-T------------------~~----------~-----------1
NUMBER OF PAGES
I
FIELD

TO LOAD

TO LOAD
5

4~~ 8

BITS ~ AND 9-11
ARE ZERO

The core 'origin must be a mUltiple of 400 (octal). The Core Seqment
Control Doublewords are sorted within the header block in order of
decreasing field and increasing origin within the same field.
There
can be no more than 32 (decimal) Core Segment Control Doublewords in
any Core Control Block.
The Core Control Block for the program at the time it is loaded into
core is always saved in words 200 (octal) through 377 (octal) of block
37 (octal) (one of the system scratch blocks) on the system device.
It is placed there by the GET and RUN operations or by the ABSLDR or
LOADER programs. This Core Control Block is used when performing a
SAVE without arguments.
NOTE
The R command differs from the RUN
command
in that the program's Core
Control Block is not written onto the
scratch area when using the R command.
In order to SAVE a program that has been
loaded by the R command all of the
arguments of the SAVE command must be
explicitly stated.

A-6

A.2.3

Relocatable

FORT~~

Library ?ile

FORTRfu~ library consists of a
library directory block
followed by relocatable binary segments. The .directory block has the
following format:

A relocatable

CH2

CHI

CH4
CH3
--------+---------i

,.,

Notes

Contents

Location

NAME OF ENTRY IN
SIXBIT ASCII PADDED
VJITE TPAILING BLANKS

("'UC::
eH6
~-------+----------.~'J
LOAD POINTER
,-,.L.a...."

{:' ADDITIONAL ENTRIES

~
t-~--1I)
~

I
I

DENOTES END OF
NAME ENTRIES

LOADER CONTROL WORD(S)
--.END OF LOADER CONTROL
WORDS FOR THIS ENTRY

377 8

------~f

CI--;- "

The Load Pointer is a number between 0 and 377
(octal) which points
(relative to the beginning of the block) to an array of Loader Control
Words. The Loader Control Words have the following information:

NUMBER OF PAGES OCCUPIED
BY THIS SEGMENT AFTER LOADING

(STARTING BLOCK OF RELOCATABLE BINARY DATA)
(DIRECTORY BLOCK #)-1

There can be one or more Loader Control Words for each entry.
The
Loader Control Words for an entry are terminated by a word of zero.
The following is a simple directory-block.

A-7

Contents

Location

1117
1
2

4040

0376

LOAD POINTER FOR "IOHI!

0530 )

1124

NAME OF ENTRY IS "EXIT

5
6

4040

0373

0000

12
13

0000

LOAD POINTER FOR "EXIT"

0000 )

LOADER
373
CONTROL
WORDS FO
"EXIT"
374
LOADER
375
CONTROL {376
WORDS FORo 377
"IOH"
8
°

NAME OF ENTRY IS "IOH ___ "

1040

MARKS

END OF ENTRIES

0000

l....-

0207
0411
0000
2400
0000

A-a

(RELATIVE BLOCK 1~8) (ONE
PAGE LONG)
(RELATIVE BLOCK 12 ) (TWO
8
PAGES LONG)
(RELATIVE BLOCK 1) (12 PAGES
8
LONG)

APPENDIX B
DETAILED LAYOUT OF THE SYSTEM

This appendix covers three topics: the reserved areas on the system
device, the resident portion of 05/8, and the various system tables.

B.l

LAYOUT OF THE SYSTEM DEVICE

The first 70 octal blocks (14K words) on the system device
reserved by the OS/8 system. These blocks are used as follows:
Block(s) in Octal

o
1-6
7-12
13-15
16-25
26

27-50
51-53
54-55
56

57
60-63

64
65
66
67

are

Contents
System Bootstrap Routine
Device Directory
Keyboard Monitor
User Service Routine
Device Handlers
ENTER Processor for USR
System Scratch Blocks
Command Decoder
SAVE and DATE Overlays
Monitor Error Routine
CHAIN Processor for USR
SYSTEM ODT
Reserved for System Expansion
CCL Reminiscences
12K TD8E Resident code
CCL Overlay

File storage begins with block 70 (octal).
The system scratch blocks are used for preserving the contents of core
when the Keyboard Monitor, USR, Command Decoder, or ODT are loaded.
In addition, various system programs use the scratch area.
Most
importantly, the SAVE command expects the Core Control Block to be
loaded in words 200 (octal) to 377 (octal) of block 37 (octal). The
Core Control Block is stored at those locations by the GET or RUN
command or by the ABSLDR or LOADER program.

B-1

A detailed breakdown of system scratch block usage follows:
contents

Block(s) in Octal

B.2

27-32

The conten~s of locatic~s lODOO ~o 11777 are
saved in ~~is area when the USR is loaded.

33-36

The contents of locations 0 to 1777 are saved
in
this area when the Command Decoder,
Keyboard Monitor, or ODT is loaded.

Words 200 (octal) to 377 (octal) of this
block contain the Core Control Block for the
last program loaded by the GET or
RUN
command, or the ABSLDR or LOADER program.

40-47

Used as scratch storage
LOADER programs.

Reserved for future expansion.

the

ABSLDR

and

LAYOUT OF THE 05/8 RESIDENT PROGRAM

The top core pages in fields 0, 1, and 2 are used by the resident
portion of OS/8 and are not accessable by the user. As a general
rule, system and user programs should never destroy the contents of
locations 7600 to 7777 of any field.
The resident portion of OS/8 is structured as follows:
Location
7600

Contents

Notes

WRITE OPER..2\TION

~ NON-DESTRUCTIVE
ENTRY TO PS/8

7605

JMP TO FIELD 1 FOR READ

DESTRUCTIVE
ENTRY TO PS/8

SYSTEM DEVICE HANDLER

ENTRY TO SYSTEM
DEVICE HANDLER

7607
~~r-""

/(
7743
7744
7745

CURRENT STARTING ADDRESS

7746

JOB STATUS 'Y]ORD

7747

~ MUST

ALWAYS BE ZERO

7750
RESERVED FOR DATA BREAK
LOCATIONS
7755
7756

,'fJ.-._ _ _ _-JT

..- THE KEYBOARD MONITOR

-- PROGRAM SETUP AREA

7777

B-2

AND ODT MODIFY THIS
AREA

TOP PAGE OF FIELD 1

7600
7616
7617
7641

10 't '"

7645
7646
7647

OUTPUT FILE LIST (3 E);TRIESl,[J-.,

INPUT FILE LIST
(MAXIHUM 9 ENTRIES)

~~:;~~::;:~:;;:=:F

..,rA'l

7677
7700

----------------------------~I

~
ri

7643

7665
7666
7667

:Jotes

Contents

Location

~ MARKS END
OF LIST

~~ii~~~- JI .~REA

DEVICE HANDLER
RESIDENCY TABLE
SYSTEM DATE WORD

COMMAND
DECODER

[

7740
7741

7757
7760
7776
7777
Systems built around TD8E DECtape without the Read-Only-Memory option
use 7600 in field 2 as an extension of the system device handler.
TOP PAGE OF FIELD 2.
7600

Used
only
for
12K
TD8E
systems.
Part
of
system
handler resides here in that
case.
7773
7774
Four words reserved for BATCH
use if machine has exactly
12K. Contains pointers into
input file.
7777
If the machine has more than 12K, the top 4 location
the last field are reserved for use by BATCH.

(7774-7777)

If a ROM (Read-Only-Memory) is being used with an 8K TD8E system,
locations 7400-7777 of field 7 are inaccessible to the user. That
core is used for system handler functions.

B-3

B.3

SYSTEM DEVICE TABLES

Each device is described to the system by entries in five system
tables.
Each of these tables is fifteen words long, where the device
number is the index into the table. The five tables are described
below.

B.3.l

Permanent Device Name Table

Entries in this table specify the permanent name of each device.
The
entries are computed by encoding the actual four-character device name
in a single word as follows:
1.

The device name is expressed as two words in the standard
DEVICE format.
For example, if the device name were "PTR"
the two words would be:
WORD 1: 2024
WORD 2: 2200
Note that when the device name is left
inserted to fill four characters.

justified;

O's

are

A single word is created by adding together these two words.

If word 2 is non-zero, bit 0 of the resulting word is forced
to be a one. For example, the table entry for "PTR" would be
4224.

An entry of zero means that there is no device for
device number.

the

corresponding

NME

Conventionally, device names
consist
only of the characters A to z and 0 to
9. The first character of the device
name should be alphabetic. The coding
used makes all one and two character
device names unique; however, names of
more than two characters are not unique.
For example, "PTR" and "RTP" have the
same encoding.
The Permanent Device Name able is fifteen locations long; it resides
in the USR. When the USR is in core the beginning of the table is in
field 1 at a location the address of which is contained in location
10036.

B.3.2

User Device Name Table

Entries are made in this table whenever the user performs an ASSIGN
and are restored to zero by a DEASSIGN. These entries have the same
format as those in the Permanent Device Name Table.
The User Device Name Table resides in locations 17741 through 17757.

B-4

B.3.3

Device Handler Residency Table

When a device handler is loaded by the USR, the entry in this table
for the device loaded (and entries for all devices whose handlers are
co-resident, if any) is set to contain the entry point for the device
handler.
Entries ether ~~~~ those that contain an address above 7600
(thus referring to the system handler) are restored to 0 when a RESET,
DECODE or CHAIN function is executed. When a program exits to the
Keyboard Monitor this table is not cleared.
The Keyboard Monitor
Commands GET, RUN, R, SAVE, and START (with no explicit address) clear
this table.
NOTE
Since the system device handler
is
always resident the first entry (SYS is
always device number 1) in the Device
Handler Residency Table is always 7607
(the entry point of the system device
handler).
The Device Handler Residency Table resides in locations 17647
17665.

B.3.4

through

Device Handler Information Table

Each entry in this table contains all the information needed by the
USR to load the corresponding handler. The format of these entries is
as follows:
Bit Condition

Meaning

Bits 0 = 1

If this is a two page device handler.

Bits 1 to 4

Contain the relative block location of
the device handler record on the system
device. This is computed by subtracting
15 (octal)
(one less than the first
device handler block) from the actual
block number.

Bits 5 to 11

Contain the offset of the handler entry
point from the beginning of the page.
Note that the entry points to
all
handlers must be in the first page.

If an entry is 0 the corresponding device handler is not saved in any
of the device handler storage·blocks. This is always true of device
number 1 (the system device) and for all device numbers that are not
used in a given configuration. The Device Handler Information Table
is 15 locations long and resides in the USR. When the USR is in core
the beginning of the table is in field 1 at a location the address of
which is contained in location 10037.

B-5

B.3.5

Device Control Word Table

Entries in this table specify special
device
characteristics,
including the physical device type. The entry format is as follows:
Bit Condition

=1
Bit 1 = 1
Bit 2 = 1

Meaning
If the device is file-structured.

Bit 0

If the device is read-only.
If the device is write-only.

Bits 3 to 8

Contain the physical
(described below),

Bits 9 to 11

For file structured devices, these bits
contain the directory block number of
the currently active tentative file.
If
bits 9 to 11 are zero, there is no
active tentative file on the device.
For non-file structured devices, bits 9
to 11 are always zero. Bits 9 to 11 are
reset to zero by the commands GET, RUN,
R, SAVE, START
(with
no
explicit
address)
and optionally by the USR
functions RESET and DECODE.

device

type

code

The device type is a number between 0 and 77 (octal), of which 0
through 20
(octal) are currently assigned to existing devices, as
follows:
Device Code

1
2
3
4
5
6

7
10
11
12
13
14
15
16
17
20
21
22
23
24
25-26
27
30
31-37
40-57

Device
Teletype
High-speed paper tape reader
High-speed paper tape punch
Card Reader
Line Printer
RKS Disk
256K Disk (RFOS)
512K Disk (RFOS + RSOS)
76SK Disk (RFOS + 2 RSOS's)
1024k disk (RFOS + 3 RSOS's)
32K Disk (DF32)
64K Disk (DF32 + DS32)
96K Disk (DF32 + 2 DS32's)
l2SK Disk (OF32 + 3 DS32's)
OECtape
LINCtape (PDP-12 only)
TMSE Magnetic Tape
TDSE DECtape
BATCH handler
RKSE Disk
NULL
reserved for future disks
TASE Cassette
VRl2 Scope
reserved for future use by DEC
reserved for use by users

B-6

The Device Control Word
17776.

B.3.6

Table

resides

locations

17760

through

Device L~~g~~ Table

There is a sixth table that is not normally considered part of the
system tables.
This is the Device Length Table and is used only by
PIP to perform the IZ
(zero directory)
and IS
(compress device)
options. This table is 64 locations long, one entry for each possible
device type. In ~~is table an entry of 0 means that the corresponding
device is non-file structured 1
otherwise the entry contains the
negative of the number of available 256-word blocks on the device.
For example, the entry for a 256K disk would be 6000
2000 (octal), or 1024 (decimal), 256-word blocks).

(octal)

{minus

The Device Length Table resides in PIP. When PIP is brought into core
the Device Length Table is in locations 13600 to 13677. When new
device types are added to the system this table should be patched with
DDT to reflect ~,e device length of the new device.
A similar table occurs in RESORC which the user may wish to patch.
It
is located in field 0 locations 2000-2377 and contains 64 four-word
entries 1 one entry for each device type. Words 1 and 2 of an entry
are the names of the device (in sixbit) and word 3 is the negative of
the number. Word 4 of the entry should be 0 for non-standard devices.

B-7

APPENDIX C
SYSTEM ERROR CONDITIONS AND MESSAGES

This is a summary of all error messages that are a result of system
errors.
These errors are also described in the relevant sections of
this manual and in the OS/8 HANDBOOK.

C.I

SYSTEM HALTS

Errors that occur as a result of a major I/O failure on the system
device can cause a system halt to occur. These are as follows:
Value of PC

Meaning

00601

A read error occurred while attempting to
load ODT. Return to the Keyboard Monitor by
restarting at 07605.

07461

An error occurred

07605

An error occurred while attempting

while reading a program
into core during a CHAIN.
Return to the
Keyboard Monitor by restarting at 07605.

to write
Keyboard Monitor area onto the system
scratch blocks.
Verify that the
system
device is not WRITE LOCKed and restart at
location 07600 to try again.
~~e

07702

A user program has performed a JMS to 7700 in
field O. This is a result of trying to call
the USR without first performing a CIF 10. As
location 07700 has been destroyed, the user
must re-bootstrap the system.

07764

A read error occurred while
loading
a
program.
Return to the Keyboard Monitor by
restarting at 07605.

07772

A read error ocurred on the system scratch
area while loading a program. Return to the
Keyboard Monitor by restarting at 07605.

C-I

10066

An input error occurred while

restore the USR.
Return to
Monitor by restarting at 07605.

attempting to
the Keyboard

10256

A read error occurred while attempting
load the Monitor by restarting at 07605.

17676

An error occurred while attempting to read
the Keyboard Monitor from the system device.
Try again be restarting at location 07605. DO
NOT PRESS CONTINUE.

17721

An error occurred while saving the USR area.
Verify that the system device is not WRITE
LOCKed, and press CONTINUE to try again.

17727

An error occurred while attempting to read
the USR from the system device.
Return to
the Keyboard Monitor by restarting at 07605.

17736

An error occurred while reading the scratch
blocks to restore the USR area. Return to
the Keyboard Monitor by restarting at 07605.

Also, there is one halt in the LOADER program:
00005

A parity error occurred

when attempting to
overlay the LOADER from-the system scratch
blocks. Return to the Keyboard Monitor by
restarting at 07605, and try again.

After retrying the operation which caused the failure, if the error
persists, it is the result of a hardware malfunction or a parity error
in the system area. Run the appropriate diagnostic program to check
the device and rebuild the system.

C.2

USR ERRORS

Fatal errors that occur during operation of the USR cause the message:
MONITOR ERROR n AT xxxxx
to be printed. In these cases, the value "n" describes the error and
"xxxxx" " is the address of the call to the USR that caused the error.
The six Monitor errors are:
Message

.Meaning

MONITOR ERROR 1 AT xxxxx
[CLOSE ERROR]

File length
too large.

MONITOR ERROR 2 AT xxxxx
[DIRECTORY I/O ERROR]

An I/O

in CLOSE

function is

error occurred while attempting to read
or
write
a
directory block. This is generally
caused by the device being WRITE
LOCKed.

C-2

~he

MONITOR ERROR 3 AT xxxxx
[DEVICE HANDLER NOT IN CORE]

device handler required for a
=ile operation
(LOOKUP,
ENTER,
CLOSE) is not in core.

MONITOR ERROR 4 AT xxxxx
[ILLEGAL USR CALL]

Illegal call to the USRI either an
attempt has been made to call the
USR from locations 10000 to 11777
or a device number of zero was
specified.

MONITOR ERROR 5 AT xxxxx
[I/O ERROR ON SYS]

I/O error occurred while reading or
or writing on the syste~ device.
Verify that the system device is
not WRITE LOCKed.

MONITOR ERROR 6 AT xxxxx
[DIRECTORY OVERFLOW]

Directory overflow occurred (see
section A.l.2 for limitations on
number of directory entries).

In addition to the MONITOR ERROR messages, system
can use the USR to print:

and

user

programs

USER ERROR n AT xxxxx
by using the ERROR function.
In this case the value of "n"
user-defined and "xxxxx" is the address of the call to the USR.

currently, two USER ERROR numbers have been assigned:

Meaning

Message
USER ERROR 0 AT xxxxx

USER ERROR 1 AT xxxxx

While running a FORTRAN or SABR
program, an attempt was made to
call a subroutine that had not been

I/O
error
occurred
while
attempting to load a program with
the GET, RUN, or R command.

loaded.
If an I/O error is made during the monitor CHAIN function the message
CHAIN ERR
is generated, and control returns to the keyboard.
Following either a MONITOR ERROR message or a USER ERROR message the
USR exits to the keyboard Monitor: the current contents of core are
preserved and bit 2 of the Job Status Word is set to a 1 to prevent
continuing from the error.

C.3

KEYBOARD MONITOR ERRORS

In addition to the USR errors described previously, the following
errors can occur after a command is given to the Keyboard Monitor:

C-3

Meaning

Message
aaaa?

The Keyboard Monitor cannot interpret
the command "aaaa". For example if the
user types HELLO the system will respond
HELLO?

BAD ARGS

Arguments to
a
SAVE
inconsistent, or illegal.

BAD CORE IMAGE

The file requested with an R, RUN, or
GET command is not a core image file.

BAD DATE

Improper syntax in a DATE command.

device NOT AVAILABLE

The permanent device name specified in
an ASSIGN, SAVE, RUN, or GET command
does not exist.

ILLEGAL ARG

The SAVE command
correctly.

name NOT FOUND

The file name specified was not located
on the device indicated. This error can
also be caused by trying to RUN or GET
from an output only device.

NOll

A START

was

command

not

are

expressed

command
(with
no
address
is prohibited when bit 2 of
the Job Status Word (location 07746) is
a 1.

specified)

e.4

NO CCLI

Command was a valid CCL command
CCL.SV is not on the system.

SAVE ERROR

SYSTEM ERR

TOO FEW ARGS

but

I/O error occurred while saving the
program.
The contents of core remain
intact.

error occurred while doing I/O to the
system device.

argument
command.

has

been

omitted

from

eCL ERROR MESSAGES
Message

Meaning

BAD DEVICE

The device specified in a eCL command is
not
of
the
correct
form,
(e.g.,
DTAO.PA:).

BAD EXTENSION

Either an
extension
was
specified
without a file name (e.g., DTAl:.PA) or
two extensions were specified (e.g.,
DTA1:FILE.PA.BN).

e-4

BAD MONITOR

The version of the Keyboard Monitor
being used is not compatible with ceL.
A new version of the monitor must be
obtained from Digital before eeL can be
used.

BAD NUMBER

A eeL command
which
uses
the
#
construction does not have the full
l6-digit specification that is required.

BAD RECOLLECTION

An attempt was made to use a previously
remembered argument when no argument was
saved.
This error occurs
when
no
argument was previously saved or when
the DATE command has been used since the
argument was saved.

BAD SWITCH OPTION

The character used with a slash
(I)
to
indicate
an option is not a legal
option.

CANNOT CHANGE CORE
CAPACITY WHILE RUNNING
BATCH

A CORE command was issued while the
BATCH program was running.

%CANT REMEMBER

The argument specified in a eeL command
line is too long to be remembered or an
I/O error occurred.

CCL 3X OVERLAY &

The version of CCL being used is not
compatible wi~~ the Keyboard Monitor
present on the system. Type R CCL to
retry.

MONITOR INCOMPATIBLE

COMMAND LINE OVERFLOW

The command line specified with the @
construction is more than 512 characters
in length.

COMMAND TOO LONG

The length of a text argument in a

MUNG

command is too long.
CONTRADICTOR SWITCHES

Either two CCL processor switches were
specified
in the same command line
(e.g., FILE-PA-FT) or the file extension
and the processor switch do not agree
(e.g., FILE.FT-BA).

name DOES NOT EXIST

The device with the name given
present on the OS/8 system.

ERROR IN COMMAND

A command not entered directly from the
console terminal is not a legal CCL
command. This error occurs when the
argument of a UA, UB, or UC command was
not a legal command.

ILLEGAL

* OR ?

not

* or- ? was used in a CCL command that
does
not
accept
the
wild
card
construction. Only CCL commands that
run FOTP or DIRECT allow the wild card
construction.

C-5

ILLEGAL SYNTAX

The eeL command
incorrectly.

line

was

INPUT ERROR READING
INDIRECT FILE

CCL cannot read the file specified with
the @ construction.

I/O ERROR ON SYS:

An error occurred while doing I/O to the

formatted

system
device.
The system must
be
restarted
at
7600
or
7605.
Do
not press CONT. as that will
surely
cause further errors.
I/O ERROR TRYING TO
RECALL

An I/O error occurred while CCL was
trying to remember an argument.

NO CCL!

CCL.SV is
device.

NOT ENOUGH CORE

The number specified in a CORE command
is larger than the number of 4K core
banks on the system.

name NOT FOUND

The file with the name given is not
present on the specified device, or the
user tried to input from an output-only
device.

'SUPERCEDED

The file specified in a MAKE command
already
exists.
This is a warning
message indicating that the file is
being replaced.

SWITCH NOT ALLOWED HERE

Either a CCL option was specified on the
left side of the < or was used when not
allowed. For example: COMPARE FlLE-NB.

TOO MANY FILES

To many files were
command.

C-6

not

present

included

the

system

CeL

C.5

COMMAND DECODER ERRORS

The following errors are printed by the Command Decoder.
After the
error message, the Command Decoder starts a new line, prints a * and
waits for &~other co~mand line~ The erroneous command is ignored.
Message

Meaning

ILLEGAL SYNTAX

The
command
incorrectly.

TOO MANY FILES

More than three output files or nine
input
files were specified (regular
mode)
or > 1 output or > 5 input
(special mode).

name NOT FOUND

The specified input file name
found on the device indicated.

C-7

line

formatted

was

not

APPENDIX D
PROGRAMMING NOTES

This appendix is a potpourri of ideas and techniques that have proven
useful in programming the PDP-8. OS/8 users may find some use in their
own programs for the techniques mentioned here.
D.l

The Default File Storage Device, DSK

0.2

Modification to Card Reader Handler

0.3

Suppression of Carriage Return/Line Feed in FORTRAN I/O

0.4

Accessing the System Date in a FORTRAN Program

0.5

Determining Core Size on PDP-8 Family Computers

0.6

Using PRTCl2-F to Convert OS/8 DECtapes to OS/12 LINCtapes

0.7

Notes on Loading Device Handlers

0.8

Available Locations in the USR Area

0.9

Accessing Additional Information Words in 05/8

0.10 SABR Programming Notes

0.1

THE DEFAULT FILE STORAGE DEVICE, DSK

The Command Decoder, as noted earlier, makes certain assumptions about
the I/O device where none is explicitly stated. Namely, on all output
files where no device name is given, the device DSK is assumed.
On
the first input file where no device name is given, DSK is assumed.
Subsequent input files assume the same device as the previous input
file. This convention was adopted to simplify typing command lines.
The permanent device name DSK is assigned when the system is built.
On all standard systems, DSK is equivalent to SYS. A useful technique
is to use the ASSIGN command to redefine the meaning of DSK
temporarily.
For example, where device DTAO is equivalent to DSK and

0-1

it becomes desirable to change DSK to DTAl, the following command
be given:

can

.ASSIGN DTAl DSK
DTAl remains the default file storage device until it is assigned a
This technique is
new name or a DEASSIGN command is executed.
considerably easier to use than rebuilding the entire system.
If 'DSK' has not been assigned via the ASSIGN command, then 'DSK'
always exists and has internal device number 2. User programs wishing
to use DSK should do an INQUIRE to find its number in case the
operator has re-assigned it.

0.2

MODIFICATION TO CARD READER HANDLER

The standard card reader handler for OS/8 uses the DEC029 standard
card codes.
Some installations may prefer to use the DEC026 codes
instead. This can be done by changing the card conversion codes with
the BUILD command ALTER.
1.

Call OS/8 BUILD by typing:
RUN SYS BUILD
in response to the dot printed by the Keyboard Monitor.

Load the card reader handler as described on page 2-42 of the
OS/8 HANDBOOK.

Use the ALTER command (see page
to make the following changes:

2-49 of the

104
105
106

3203
4007
3502

7735
4076
0774

114
115
116

7514
0577
3637

3314
1002
0305

124
125
126
127

0104
1211
3374 .
0641

3204
1273
3606
1341

134
135
136

7316
3410
1376

3716
1175
3401

CHANGE RELATIVE LOCATION

OS/8

HANDBOOK)

The new system will have modified card codes.
Note that this procedure does not affect FORTRAN run time card input
with READ (3,n). The conversion table for FORTRAN is UTILTY.SB on
source DECtape #2. (DEC-S8-0SYSB-A-UA2)

D-2

026 PUNCH CARD CODES
Octal 8-bit
CODE

DEC026
CODE

300

301
302
303
304
305
306
307

8-4
12-1
12-2
12-3
12-4
12-5
12-6
12-7

310
311
312
313
314
315
316
317

12-8
12-9
11-1
11-2
11-3
11-4
11-5
11-6

0
1
2
3
4
5
6
7

320
321
322
323
324
325
326
327

11-7
11-8
11-9
0-2
0-3
0-4
0-5
0-6

8
9

330
331
332
333
334
335
336
337

0-7
0-8
0-9
11-8-5
8-7
12-8-5
8-5
8-2

Octal 8-bit
CODE

DEC026
CODE

240
241
242
243
244
245
246
247

BLANK
12-8-7
0-8-5
0-8-6
11-8-3

SPACE

0-8-7

11-8-7
8-6

250
251
252
253
254
255
256
257

0-8-4
12-8-4
11-8-4
12
0-8-3
11
12-8-3
0-1

(
)

260
261
262
263
264
265
266
267

0
1
2
3
4
5
6

270
271
272
273
274
275
276
277

8
9
11-8-2
0-8-2
12-8-6
8-3
11-8-6
12-8-2

CHARACTER

#
$

,
<

=
>

NOTE
On some IBM 026 Keyboards this character
is graphically represented as 0 •
A card containing an
8-2 in column 1
with all remaining columns blank is an
end-of-fi1e card.

D-3

CHARACTER
@
A

B
C
D
E
F
G

H
I
J

K
L

M
N
0

P
Q

S
T

u
V

w
X

y
Z
[

\
]

0.3

SUPPRESSION OF CARRIAGE RETURN/LINE FEED IN FORTRAN

It is often desirable to suppress the automatic carriage return/line
feed
(CR/LF)
following FORTRAN WRITE statements to achieve an easily
readable text. The following three methods in OS/8 FORTRAN can be
used to achieve this result:
1.

Follow the I/O list of a WRITE statement with a comma.
the following statements:
100
101

Thus,

WRITE (1,100) N,
FORMAT (lX,lSHTHE VALUE OF A(,I2,SH)4IS )
READ (l,lOl)A(N)
FORMAT (F8.4)

result in the following single line (assume N has a value
12 and a value of 147.83 is being input):

THE VALUE OF A(12) IS 147.83
2.

Use of an empty field print statement enables a text to be
printed without a following CR/LF when there is no variable
to be printed. For example:
102

WRITE (1,102)IDUMMY,
FORMAT ('DESIRED TEXT',IO)

READ statement using break character, as follows:

101

READ (1,101) IA,IB,IC
FORMAT ('A=',Il,'B=',Il,'C=J,Il)

results in no CR/LF after each phrase is printed.
the output is all printed on a single line.

0.4

That

is,

ACCESSING THE SYSTEM DATE IN A FORTRAN PROGRAM

The availability of the system Date word in location 17666 is useful
to many 05/8 programs. The following FORTRAN program illustrates how
the Date can be accessed in SABR code:
C

PROGRAM PRINTS THE CURRENT DATE

DUMMY DATE

S
S

TAD I DATE

S
5

TAD TEMP
AND (7

5
5
5

DCA\IYR
TAD TEMP
RAR;RTR
AND (37
DCA \IDAY
TAD TEMP
CLL RAL;RTL;RTL
AND (17
DCA \IMO
WRITE (1,100) IMO,IDAY,IYR
FORMAT (/'DATE:
'I2'-I2-197'I1/)

S
S

5
S

S
100

DCA TEMP

D-4

S
SDATE,
S
STEMP,

0.5

CALL EXIT
CPAGE 2
6211
7666
0

DETERMINING CORE SIZE ON PDP-8 FAMILY COMPUTERS

Many times system programs need to determine the amount of core
available to them at run time. For example, the 05/8 system programs
LOADER, PAL8, and CREF perform this calculation.
Because
of
differences in the extended memory control of POP-8 family computers,
subroutines that work on one machine might not work on another.
The following three conditions cause the most difficulty:

On a POP-8 with an extended memory control, addressing
nonexistent
memory
from field 0 causes the following
instruction to be skipped and
the
contents
of
the
corresponding field 0 location to be executed. For example:
COF 70
TAD I (X)
HLT

/NONEXISTENT FIELD
/EXECUTED LOCATION X
/THIS INSTRUCTION SKIPPED

•

•
X,

•

CLA CLL CML RAR

/LOAD 4000

The preceding code causes 4000 to be loaded into the AC and
the HLT instruction to be skipped when executed on a PDP-8.
2.

On a PDP-12 with an odd number of 4K banks (12K, 20K,
2aX),
all reads in the first nonexistent field load zeros. Reads
to higher fields, as wel·l as all reads to nonexistent memory
on a machine with an even number of 4K banks load all one
bits.

The PDP-8/L normally treats all CDF's to fields 2 through 7
as NOP's.
(It tests bits 6 to 7 of all CDF and CIF
instructions for D's before executing the lOT.)
However,
there is a special 12K option for the PDP-8/L called a BM08.
With this option a CDF to field 2 is valid, but a COF's to
fields 4 through 7 remain NOP's.

For those who are interested, the following subroutine has been tested
on the PDP-8, 8/5, 8/L, 8/I, S/E, PDP-12, and LINC-8 computers. For
the purpose of this example, it is assembled at 00200.
/SUBROUTINE TO DETERMINE CORE SIZE.
/THIS SUBROUTINE WORKS ON ANY POP-8 FAMILY
/COMPUTER. THE VALUE, FROM 1 TO 10 (OCTAL),
/OF THE FIRST NON-EXISTENT MEMORY FIELD IS
/RETURNED IN THE AC.
/NOTE -- THIS ROUTINE MUST BE PLACED IN FIELD 0

D-5

0200 0000
0201 7300
0201 6201
0203 1237
0204 7006
0205 7004
0206 0217
0207 1232
0210 3211
0211 6201
0201 1635
0213 7000
0214 3211
0215 1213
0216 3635
0217 0070
0020 1635
0221 7400
0022 1221
0223 1236
0224 7640
0225 5232
0226 1211
0227 3635
0230 2237
0231 5202
0232 6201
0233 1237
0234 5600
0235 0221
0236 1400
0237 0001

0.6

':':::ORE ,

CORD,

CLA eLL
CDF 0
CORSIZ
TAD
RTL

/(NEEDED FOR PDP-8L)
/GET FIELD TO TEST

RAL

COR1,
COR2,

COR70,
CORX,

COR70
AND
COREX
TAD
DCA
.+1
CDF
\N
CORLOC
TAD I
NOP
CORl
DCA
COR2
TAD
CORLOC
DCA I
70
CORLOC
TAD I
7400
CORX
TAD
CORV
TAD
SZA CLA
COREX
JMP
CORl
TAD
CORLOC
DCA I
CORSIZ
ISZ
CORO
JMP

COREX,

CDFO
TAD
JMP I
CORLOC, CORX
CORV,
1400
CORSIZ, 1

CORSIZ
CORE

/MASK USEFUL BITS
/SET UP CDF TO FIELD
/N IS FIELD TO TES~
/SAVE CURRENT CONTENTS
/(HACK FOR PDP-81)
/7000 IS A "GOOD" PATTERN
/(HACK FOR PDP-8.,ND-OP)
/TRY TO READ BACK 7000
/(HACK FOR PDP-8,.NO-OP)
/GUARD AGAINST "WRAP AROUND"
/TAD (1400)
/NON-EXISTENT FIELD EXIT
/RESTORE CONTENTS DESTROYED
/TRY NEXT HIGHER FIELD
/LEAVE WITH DATA FIELD 0
/lST NON-EXISTENT FIELD
/ADDRESS TO TEST IN EACH IELD
/7000+7400+1400=0
/CURRENT FIELD TO TEST

USING PRTC12-F TO CONVERT 05/8 DECTAPES TO 05/12 LINCTAPES

Many users of OS/8 on the PDP-12 will be interested in the fact that,
since 05/8 uses an identical file structure on all devices, PDP-8
DECtape in OS/8 format may be directly copied to 05/8 LINCtapes by the
PRTC12-F program.
The PRTC12-F program uses the PDP-12 TC12-F hardware option to read
DECtapes and convert these tapes to LINCtape. This hardware option is
required to read DECtapes on the PDP-12
THE PRTC12-F program is described in the document DEC-12-YIYA-D. This
document describes the program operation in detail, and must be read
before attempting to use PRTC12-F. The operations that convert OS/8
format DECtapes are as follows:
1.

Mount the OS/8 DECtape on unit 1 and a PDP-12
formatted with 129 words per block on unit 2.

When the READ questionnaire is displayed, respond as follows
(responses are underlined:
the character )
stands for
carriage return and
stands for line feed):

READ 1777 )
BLOCKS
TAPE FORMAT A )
UNIT 1 )

0-6

LINCtape

STARTING ~vITH BLOCK 0) +
etc.
3.

~fuen

the
follows:

~'lRITE

questionnaire

displayed,

respond

NRITE THE RESULT
IN TAPE FORMAT B)
ON UNIT 2)
STARTING AT BLOCK 0) +
etc.
D.7

NOTES ON LOADING DEVICE HANDLERS

D.7.1

Problem with Multiple Input Files

There is a problem associated with reusing Device Handler
OS/8. This problem is best illustrated by an example:

areas

Assume a program has reserved locations 1000-1377 for its input
handler and locations 7400-7577 for its output handler. If the
program gives a USR FETCH command to load the DTAI handler as an input
device handler, all 8 DECtape handlers will load into 1000-1377, since
they are all co-resident. If another FETCH is issued to load the DTA2
handler as an output device handler, that handler will not be loaded,
because it shares space with the DTAl handler currently in core. This
is fine -- however, if the user now switches input devices and FETCHes
the paper tape reader handler as an input device handler it will
destroy the DTA2 handler and the next attempt to output using the DTA2
handler will produce errors. There are two ways to get around ~~is
problem.

Always assign the handler which you expect to stay in core
the longest first. Most programs can process more than one
input file per program step (e.g., an assembly pass is one
program step) but only one output file~ therefore, they
assign the output handler before any of the input handlers.
In the above example, the problem would be eliminated if the
DTA2 handler were assigned first.

Always give a USR RESET call before each FETCH.
Obviously,
this call should not delete any open output files. This
means that the USR will always load the new handler, even if
another copy is in core.
The user must FETCH the output
handler again before issuing the USR CLOSE call, otherwise
the USR will determine that the output handler is not in core
and give a HONITOR ERROR 3 message.

8K FORTRAN uses this second method for device-independent I/O
time.

D.7.2

run

Dynamically Loading Device Handlers

Some programs which use dynamic core allocations will want to use OS/8
Device h~~dlers but cannot afford to always allocate the maximum of
two pages per handler. The following is a subroutine which loads a
device handler dynamically, returning its entry in the AC. It assumes
that the name of the handler is in locations NAMEI and NAME2, and a

D-7

subroutine GETPAG exists uhich -;ets a page :rom the Dottom of
available field ~ of storage and re~urns its address in the AC.
This
example subroutine runs in field : and can only be called from field
1, but can be rewritten for any other possibility.
ASSIGN, ;J
TAD NAME 1
DCA Nl
TAD NAME 2
/MOVE DEVICE NAME INTO "INQUIRE" COMMAND
DCA N2
CDF CIF l~
JMS I (7700
/USRIN - FORCE USR INTO CORE
10
JMS I (200
12
/INQUIRE
o
Nl,
o
N2,
o
LOCI,
JMP ASSERR
/NO SUCH DEVICE - QUIT
TAD LOCl
SZA
/IS THE HANDLER ALREADY IN CORE?
JMP I ASSIGN /YES - RETURN ITS ENTRY POINT
JMS GETPAG
/GET A PAGE DYNAMICALLY
DCA LOC2
/LOAD DEVICE NUMBER
ASSTRY, TAD N2
JMS I (200
/FETCH
1
/PAGE TO FETCH INTO
o
LOC2,
JMP TWOPAG
/FAlLED - MUST BE A TWO-PAGE HANDLER
TAD LOC2·
JMP I ASSIGN /RETURN ENTRY POINT
/GET ANOTHER PAGE
TWOPAG, JMS GETPAG
ISZ LOC2
/SET "TWO PAGE HANDLER ALLOWED" BIT
CLA

JMP ASSTRY
ASSERR,

0.8

.....

/FETCH WILL SUCCEED THIS TIME
/ERROR ROUTINE

AVAILABLE LOCATIONS IN THE USR AREA

A few programs may need additional storage space in field 1 when the
USR is ~n core.
A number of locations in the USR area (10000 to
11777) are available and may be used whenever the USR is in core. The
locations are as follows:
1.

Locations 10000 to 10006 are available for scratch
and/or ODT breakpoint usage, without restriction.

All auto-index registers (locations 10010 to 10017)
may be
used, but these locations are destroyed by USR operations.

Location 10020 to 10037 may be used as scratch
no restrictions.

Locations 11400 to 11777 are used by the USR to preserve the
last directory segment read while performing a LOOKUP, ENTER,
or CLOSE operation.
Location 10007 contains a key specifying
which segment of which device is currently in core.

0-8

storage

with

Any user program may use locations 11400 to 11777 as scratch
storage as long as location 10007 is set to 0 before the
first use.
Of course, the LOOKUP, ENTER,
and
CLOSE
operations will read a directory segment into 11400 to 11777
and set 100007 to a non-zero value again.

D.9

ACCESSING ADDITIONAL INFORMATION WORDS IN OS/8

In all of these cases, the USR must have been previously brought
core with ~~e USRIN fQnction e

0.9.1

into

After a LOOKUP or ENTER

After a LOOKUP or ENTER, location 10017 points to the length word of
the file entry. To get a pointer to the first Additional Information
Word, a program would execute the following code:
CDF 10
TAD I (1404

/GET # OF ADDITIONAL INFORMATION WORDS
/FROM DIRECTORY

SNA

JMP NONE

/NO ADDITIONAL INFORMATION WORDS

TAD I (0017
DCA POINTER
•
•
•
·POINTER" now points to the first Additional Information Word.

0.9.2

After a CLOSE

Because CLOSE is a legal operation even if no output file is present,
it ~s not suggested ~~at Additional Inforruation Words be modified
following a CLOSE. To alter the Additional Information Words of a
permanent file, do a LOOKUP to get the directory segment into core,
then alter the words and rewrite the directory segment.

D.9.3

Rewriting the Current Directory Segment

Whenever a user program changes t..'1e Additional Information Words of a
file, it must rewrite the directory segment containing that file entry
in order to make sure the changes are permanently recorded.
The following code, which must be in field 1, will rewrite the current
directory segment:
CDF 10
TAD 7
AND {7
DCA SEGNO
CIF 0
JMS I 51

/CODE IS IN FIELD 1
/GET DIRECTORY KEY WORD
/EXTRACT SEGMENT NUMBER
/LOC 51 POINTS TO THE DEVICE HANDLER

0-9

SEGNO,

4210
1400
0
JMP

/WRITE OPERATION
/DIRECTORY SEGMENT CORE ADDRESS
ERROR

/ERROR REWRITING DIRECTORY

Location 10051 will always point to the device handler entry point
used to read in the last directory segment, following a LOOKUP or
ENTER operation.

D.I0

SABR PROGRAMMING NOTES

D.I0.1

optimizing SABR Code

There are two types of users who will be using the SABR assembler
those who like the convenience of page-boundary-independent code and
are willing to pay the price for it, and those who need a relocatable
assembler but are still very location conscious. These optimizing
hints are directed to the latter user.
One way to beat th7 high cost of non-paged code is to Page It
Yourself.
This 1S done by using the LAP (Leave Automatic Paging)
pseudo-op and the PAGE pseudo-op to force paging where needed.
This
saves 2 to 4 instructions per page from elimination of the page
escape. In addition, the fact that the program must be properly
segmented may save a considerable amount.
Wasted core may be reduced by eliminating the ever-present CDP
instructions which SABR inserts into a program. This is done by using
"fake indirects". Define the following op codes:
OPDEF
OPDEP
OPDEF
OPDEF
•
•
•

ANDl 0400
TADl 1400
lSZl 2400
DCAl 3400

These codes correspond to the PDP-8 memory reference instructions but
they include an indirect bit. The difference can best be appreciated
by an example:
If X is off-page, the sequence
LABEL,

SZA

DCA X

is assembled by SABR into
LABEL,

SZA
JMS
SKP

DCA I (X)

or four instructions and one literal.

0-10

The sequence

PX,

LABEL,

SZA

DCAI PX
assembles into three instructions for a saving of 40 percent.
Note,
however, that the user must be sure that the data field will be
correct when the code at LABEL is encountered.
Alse note that ~~e
SABR assumes that the Data Field is equal to the Instruction Field
after a JMS instruction, so subroutine returns should not use the JMPI
op code.
The standard method to fetch a scalar integer argument of a subroutine
in SABR is:
Code
IARG,
SUBR,

DUMMY X

BLOCK 2
TAD I SUBR
DCA X

INC SUBR'
TAD I SUBR

DCA X'
INC SUBR'
TAD I X
DCA IARG

•
•
•

BLOCK 2

This code requires 19 words of core and takes
microseconds to execute. The following sequence:

several

Code
IARG,
SUBR,

o
BLOCK 2
TAD I SUBR
DCA X
INC SUBR'
TADI SUBR'
DCA IARG
INC SUBR'
HLT
/THIS IS A CDF
TAD I IARG
DCA IARG

•
takes only 14 words and executes in approximately

0-11

the

hundred

D.10.2

Calling the USR and Device Handlers from SABR Code

One important thing to remember is that any code which calls the USR
must not reside in locations 10000 to 11777. Therefore, any SABR
routine which calls the USR must be loaded into a field other than 1
or above location 2000 in field 1. To call the USR from SABR use the
sequence:
CPAGE n
6212
JMS 7700
REQUEST
ARGUMENTS
ERROR RETURN

/N=7+(# OF ARGUMENTS)
/CIF 10
lOR 200 IF USR IN CORE
/OPTIONAL DEPENDING ON REQUEST
IOPTIONAL DEPENDING ON REQUEST

To call a device handler from SABR use the sequence:
CPAGE12
6202
JMS I HAND
FUNCT
ADDR
BLOCK
ERROR RETURN
SKP
HAND,

110 IF "HAND" IN PAGE 0
/CIF 0
/00 NOT USE JMSI

/"HAND" MUST BE ON SAME PAGE

lAS CALL, OR IN PAGE 011

0-12

APPENDIX E
CHARACTER CODES AND CONVENTIONS

Table E-l contains a list of the control characters used by OS/8 and
associated system programs.
Table E-2 contains the OS/8 character
set, which is a subset of the complete ASCII code, the unlisted codes
are generally not used by OS/8 or the system programs. Note the
following:
1.

On some terminals, the character back-arrow (~) is replaced
by an underline ()
character, and the up-arrow (t) is
replaced by circumflex (~).

Some terminals use parity codes rather than forcing the
leading bit of the 8-bit character code to be a 1. To avoid
problems, OS/8 system programs always ignore the parity bit
during ASCII input.

as/8 does not handle lower case characters (octal codes 341
through 372). The exceptions to this are the editors, EDIT
and TECO. The KL8E and LPSV handlers can be modified to
handle lower case.
Table E-1
OS/8 Control Characters

Octal
8-bit
Code

Character
Name

Remarks

000

null

Ignored in ASCII input.

200

leader/trailer

Leader/trailer code precedes and
follows the data portion of binary
files.

203

CTRL/C

OS/8 break character, forces return
to Keyboard Monitor, echoed as tC.

207

BELL

CTRL/G.

211

CTRL/I, horizontal tabulation.

212

LINE FEED

Used as a control character by
Command Decoder and ODT.

213

CTRL/K, vertical tabulation.

214

FORM

CTRL/L, form feed.

E-1

the

Table E-~ (Cant.)
OS/8 Cont~c~ Characters
Octal

a-bit

Character
Name

I Code

Remarks

I--------------------------------------------------------------------~

I 215

RETURN

Carriage return, generally echoed
as carriage return followed by a
line feed.
Used only on LS8E
Puts current line
character mode.

216

line
into

printer.
expanded

217

CTRL/O

Break Character, used to suppress
Teletype output, echoed as to.

225

CTRL/U

Delete current input
as tU.

232

CTRL/Z

End-of-File character for all ASCII
and binary files
(in relocatable
binary files CTRL/Z is
not
a
terminator if it occurs before the
trailer code).

233

ESC

ESCape replaces ALTMODE on some
terminals.
Considered equivalent
to ALTMODE.

375

ALTMODE

Special
break
Teletype input.

376

PREFIX

PREFIX replaces ALTMODE on some
terminals.
Considered equivalent
to ALTMODE.

377

RUBOUT

Key is labeled DELETE on
some
terminals.
Deletes the previous
character typed.

E-2

line,

character

echoed

for

Table E-2
ASCII Charac~er Codes
octal
8-bit
Code

Code

Punched
Card
Code

240

blank

11-8-2
8 .... 7
8-3
11-8-3
0-8-3

241
I

6-bit

...... "'"

"It"

243

244
245

43
44

45
46

247

8-5

250
251

246

252
253

254
255
256
257

260
261
262
263

264
265

266
267

52
53

54
55
56

60
61

62
63

2
3

64
65

4
5
6
7

67
70
71

272

273
274

304

(
)

12-8-3
0-1

271

300
301
302
303

0-8-3

#
$
%
&

270

275
276
277

12-8-5

11-8-5
11-8-4
12-8-6

Character
Representation

8
9
8-2

I 11-8-6

74
75
76
77

8-6
II 0-8-6

8-4

01
02
03
04

12-8-4

0-8-7

I 12-1

6
7
8

colon
semicolon
less than
equals
greater than
question mark

at sign

12-2

12-3
12-4

10
11

12-8
12-9

H
I

310
311

opening parenthesis
closing parenthesis
asterisk
plus
conuna
minus sign or hyphen
period or decimal point
slash

space (non-printing)
exclamation point
quotation marks
number sign
dollar sign
percent
ampersand
apostrophe or acute
accent

I 12-5
12-6
II 12-7

305
306
307

Remarks

E
F

E-3

Table E-2 (Cont.)
ASCII Character Codes
Punched
Card
Code

Octal
8-bit
Code

6-bit
Code

312
313
314
315
316
317

12
13
14
15
16
17

11-1
11-2
11-3
11-4
11-5
11-6

320
321
322
323
324
325
326
327

20
21
22
23
24
25
26
27

11-7
11-8
11-9
0-2
0-3
0-4
0-5
0-6

330
331
332
333
334
335
336
337

30
31
32
33
34
35
36
37

0-7
0-8
0-9
12-8-2
11-8-7
0-8-2
12-8-7
0-8-5

Character
Representation

Remarks

L
M

N
0

P
Q

R
S
T
U

w
X
y
Z
[

opening bracket,SHIFT/K
backs1ash, SHIFT/L
closing bracket, SHIFT/M
circumflex
underline - BOF signal

]
....

NOTES

These are the DBC029 standard card codes.

On most DEC Teletypes circumflex is replaced by up-arrow (f).

A card containing 0-8-5 in column 1
columns blank is an end-of-file card.

On most DEC Teletypes underline

with

all

remaining

replaced

back-arrow

(+-) •

On some IBM 029 keyboards
cent sign (¢).

is graphically represented

On some IBM 029 keyboards \
logical NOT (-).

On some IBM 029 keyboards
vertical bar el>.

On a very few LP08 line printers, the character
is printed instead of backs lash.

On a very few LP08 line printers, the character heart
printed instead of underline.

10.

The character number sign on same terminals
pound sign (I).
E-4

graphically

represented

is graphically

represented

diamond

(0)

(~)

replaced

APPENDIX F
05/8 INPUT/OUTPUT ROUTINES

Appendix F describes a set of generalized I/O routines for use under
the 05/8 system. The routines presented here are used in all the 05/8
CUSPs (Commonly Used System~Prograrns) in more or less this form.
Variations are made depending on the particular application and how
errors are to be handled. The routines, as indicated, will work as
presented.
The routines work most efficiently in field 1, since CIF
10's are not necessary when addressing the Monitor, and the Command
Decoder tables are similarly available. Obviously the routines can be
modified to run in any memory field or core locations.

F.l

GENERAL DESCRIPTION

These subroutines assume that the Command Decoder tables have been set
up to indicate the proper I/O devices. The routines handle device
handler assignment without user interference.
All I/O is done by
simple subroutine calls.
The user program never needs to interface
with the Monitor or device handlers.
All buffering and internal
bookkeeping are performed by the routines. In these routines, it is
ass~~d ~~at

only one output device is

used

time,

i.e.,

~~e

output routine does not automatically set up for the next output
device. This modification can be made if desired. As many as nine
inputs are handled automatically.
When input from one device is
exhausted, the input routine will automatically utilize the next
device specified in the Command Decoder list of inputs.

F.2

SUBROUTINES FUNCTIONS

Following is a brief list of the subroutines and their functions.
ICHAR - Character input routine.
Call sequence:
ICHAR
ERROR RETURN
NORMAL RETURN

JMS

F-l

Error:
If AC)O, an EOF on input has occurred. No more
input is available. If AC(O, a device error has
occurred.
Normal:
8 bit character is in the AC.
OCHAR - Character output routine.

Call:
TAD CHAR /8 BIT CHARACTER
OCHAR
ERROR RETURN
NORMAL RETURN

JMS

Error:
AC(O implies a fatal error.
AC ) or = 0 implies that the hole
output was exceeded.

allotted

for

Normal:
AC-O. The character has been put into the device
output buffer.

IOPEN - Input initialize routine.
Call:
JMS IOPEN
RETURN

Return:
Input pointers reset. The next call to ICHAR
will read from the first device in the Command
Decoder input list.
OOPEN - Output initialize routine.
Call:
JMS OOPEN
ERROR RETURN
NORMAL RETURN

Error:
If AC> or = 0, no output device was specified.
If AC(O, an error occurred opening the file.
Normal:
An output file has been opened.

No action
the output was a non-file structured device.

F-2

OCLOSE - Output close routine.
Call:
JMS OCLOSE
ERROR RETURN
NORMAL RETURN
Error:
Either the closing length is too large for the
space allotted or an output error has occurred.
Normal:
The output file is now a permanent file
output device.

F.3

the

SUBROUTINE PARAMETERS

These subroutines handle device assignment and internal buffering
automatically. To accomplish this, certain parameters must be defined
at assembly time. These parameters specify all details of handler
location, and buffer size for the routines.
Parameter

Definition

INDUF =

Address of input buffer.

INCTL =

Input buffer control word.
See the section on
using device handlers for details of the control
word format.

OUBUF =

Output buffer address.

OUCTL =

Output buffer control word.
This must be
negative number to indicate a writs operation.

INRECS =

Number of input records in input buffer.
INCTL/256 (DECIMAL).

INDEVH =

Address of input device handler.

OUDEVH =

Address of output device handler.

INRECS =

The parameters can either be a part of the actual subroutine source,
or they can be contained in a separate parameter file to be assembled
with the subroutine file.
The latter approach provides greater
flexibility in using the routines.

F.3.l

Example

Following is a s~T.ple of ~~e use of ~~e subrolltines~
The program
simply calls the Command Decoder, and transfers input from the input
devices to the output file, closes the output, and exits.

F-3

FIELD 1
*2000
JMS I (7700
10
JMS I (200

CALLCD,

/LOCK MONITOR INTO CORE.
/CALL COMMAND DECODER
/TO PICK OPTIONS.

0
JMS I (IOPEN

OK,

TSTEOF,

CLOSE,

JMS I (OOPEN
SMA CLA
JMP OK
JMS TERR
TEXT /OPEN FAILED/
JMS I (ICHAR
JMP TSTEOF

/EITHER ERROR OR EOF.
/SAVE IT.

JMS I (OCHAR
JMP OUTERR
JMP OK
SMA CLA
JMP CLOSE
JMS TERR
TEXT /READ ERROR/
JMS I (OCLOSE
JMP CLERR

/CLOSE OUTPUT FILE.
/CLOSE ERROR

JMP CALLeD

/REXT.

OUTERR,

JMS TERR

CLERR,

TEXT /OUTPUT ERROR/
TERR
TEXT /CLOSE ERROR/

TERR,

/SETUP TO START LOOKING AT
/CD INPUT FILE.
/OPEN UP AN OUTPUT FILE.
/IF AC(O, WE HAD A FATAL
/TYPE ERROR. AC)O IS O.K.
/ERROR.

/TRANSFER THE CHARACTER
/OUTPUT ERROR
/TRANSFER UNTIL EOF FOUND.
/IF NEG., FATAL
/EOF. CLOSE OUTPUT

JMS

o
TAD I TERR
RTR;RTR;RTR
JMS TYPIT
TAD I TERR
JMS TYPIT
ISZ TERR
JMP TERR+1

TYPIT,

AND (77
SNA
JMP CRLF

CRLF,

TTYOUT,

TAD (300
JMS TTYOUT
JMP I TYPIT
TA (215
JMS TTYOUT
TAD (212
JMS TTYOUT
JMP CALLCD

TLS
TSF
JMP.-1; CLA; JMP I TTYOUT

F-4

F.3.2

Subroutine Listing

A listing of the routines follows.
The parameters are set up in such
a way as to allow them to be put into a separate file. Another
parameter, ORIGIN, determines the location of the routines.

F-S

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IDEVICE CONTROL TA~LE

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FIELD 1
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nUFLOaOUCTL&70 IOUTPUT SUFFER FIELD

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12/27/72

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13 - WAY UNPACKING S~ITCH

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INC •• UNPACK THE NEXT CHA~.
1010 LAST READ GIVE tOF ON THIS DEVICE?

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ITAKE EOF EXIT FROM ICHAR.
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IUPDATE

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(e232

115 IT A ·Z (EOF)?

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IYES •• ~OOK AT NEXT INPUT

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3350
3774
l013

DCA
DCA I

OlJ~:CNT

(OIJTINH
(OIJ!itTf

ISZ
OOIPEN
OOHETN, CDF Clf 10
JMP I
OOIPEN
OEFA.i.l, TAU I
OU7b00
ANIJ
(71b0
SNA tL.
Jf>IP
ONTEkR
TAD I
OUlbl2l0
AND
DCA

(17

OU1b0121
JMP
OUENTR
a ~JT Et( R, ClAC l l CML RAR
JMP
OOWETN
ONOFll., I5Z
(OUTINH

JMP

OOf<ETN

OUTor1P, '"
DCA

COF
TAO I
5ZA ClA
JMP
TAD
SNA
ISZ

~304

7451r1

OEI:All

JM:i I

7"40

'7~S4
17~~5

JMP

13501

17~5&

2300

17'157

1221

1 Hlb0

170&1

3302
1300

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11"'62

710&

170163

ell

7~0b

RTL

TAO
DCA

OUCTLW
1121

TAn
OUE.LEN
SNl SZA ClA
JMP I
UUTDMP
DI1CIHF, elF CDF o
CDF
10
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OUHNDL

1 H'I71.1

5~4"
b2~3

b211

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0000

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512l({l~

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171\1)4

2246

, 71l-, 1;,

""11ll

'::Ib4b
00~"

IANO TRY AGAIN
IINHIBIT OUTPUT
IDUMP OUTPUT BUFFER
ISTORE CONTROL WORD

IIF THIS IS FIRST WRITE, START THE
ISEARCH fORWARO ON DfCTAPE

RTL

ell. CML

1 '075
17016
17011

IMAKE IT 0

IGET STARTING BLOCK Of THIS
ITRANSFER

7120
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135~

17072

IGtTS SIZE OF HOLE AVAILABLE
/FAILUR!. SEE wHAT wt 010.
ICLEAR CLOSING LENuTH
IClEAR OUTPUT INHIBIT
ISt'r UP POINTERS

OUNO\llR
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t7~70

11013

115 OUTPUT INHIBITED?

1350
3350

700fo>

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170b4
1 '1065
1 H'lfl6
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12/21172

ICOMPUTE • OF RECORDS TO OUTPUT

AI~D

(11

TAO
DCA
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IUPDATE ClOSING LENGTH

OUCC~T

ISEE IF CLOSING LENGTH WILL UE
IBIGGER THAN OUTPUT HOLE

UUCTLw,

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IWIlL BE TOO BIG
100 THE WRITE

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PAl.8-V?
17~lb

1MB
lHH74715
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7&01

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(2e0

12/21/12

PAGE 3-1

IENTER THE OUTPUT FILE

1b01

IGETS STARTING BLOCK OF MOLE

PAL8.V7
171 !/.Ib

001.10

171~7

b211
1714
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17110
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~35~

12/27/72

PAGE '5

ICLSOE OUTPUT fILE

(OuTIN'"

IIF OUTPUT INHIBITED, CLOSE IS A NOP.
IA NOP
IDETERMINE If OUTPuT IS TO PTP
Ilf IT IS, DON'T OUTPUT A ~z.

4711

JMS 1

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(OTYPE

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1372
7"40
13&7
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5353
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JMS

53~3

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IERROR RETURN
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q7b~

FIL\..lP, JMS

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OCRET
COCHAR
OCRET
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5353

HIP

IFILL TO BOUNOARY WITH 0

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7110
13b5
1364
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7&40
5324
1163
137 'i

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IIF OUTPUT IS DIRECTORY OEVICE, fILL
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(77
I

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(OUO"CT

IARE WE UP TO BOUNDARY YET?

fILLIP
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lIS THERE A FULL WRITE LEFT?
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NOOUlMP
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IGET DEVICE NUMBER
ICLOSE THE OUTPUT FILE

, 7b01
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COF CIF 10
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IPOINTER TO fILE NAME
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7200
17200
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172~2

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PAGE
QUSETP, 0
TAD
CIA
DCA
TAD
DCA
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DCA
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12/27/72

PAGE 5-1

IINITIALIZE OUTPUT POINTERS
(OUCTLI!.3700
OUDwCT
(OU~UF

IDOUBLE WORD OUTPUT COUNT
IINITIALIZE WORD POINTER

OUPTR
OUJMPE
UUJMP

13 WAY UNPACK SwITCH

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0

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IPOINT TO NEXT BUFFEf1 WO~O
ISUMP DOUBLE COUNT AFTER
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IOuTPUT IT
IAN ERROR
IRESt:T OUTPUT POINTERS
IPOINT TO FIRST DOUBLE WORD
IPOttliT ouPTR TO SEcnND
INORMAL EXIT

OCI1AR

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12/27/72

PAGE &-1

TAD (elF CuF 0

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IOPEN OUTPUT FILE
IERROR. IF AC<0, IT WAS fATAL
INON FILE STRUCTURED OUTPUT

TEXT IOPtN FAIlEDI

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ICONTINUE UNTIL EOF.
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JMS TERR
TEXT IHEAD ERRORI

12040
12(1:41

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IREAO A C~ARACTER
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IIGNDRE BLANKS

CLOSL,

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PAGE 7-1

12/27/72

'TLS
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10 TERMINATES

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TTYOUT 2111

TY~lT

2075

12/27/72

PAGE 7 .. 2

INDEX
Additional information words, 1-3,
2-7, D-9
Alphanumeric option, Command
Decoder, 3-3
switches, 3-6
ALTMODE key, 3-3
Ascertain device information
(INQUIRE function), 2-13
ASCII character codes, E-2, E-3
ASCII files format, A-4
ASSIGN command, 1-6
Asterisk,caution in using, 3-9
Batch mode, 3-10
Batch operating system, 1-5
Binary file format, A-4
Block, core control, 1-4
Blocks
directory, A-I
system scratch, B-1
Blocks of words, 1-2, 1-3
BUILD program, 5-1
Call Command Decoder (DECODE
function), 2-10; 3-3
in Special Mode, 3-9
Calling device handlers, 4-1
Calling USR and device handlers
from SABR code, D=13
Card codes, DEC029, 4-7
Card Reader (CDR) operation, 4-7
Card Reader handler modification,
0-2
Carriage return/line feed suppression in FORTRAN, D-4
Cassettes operation, 4-6
CCL, 3~10
CCL error messages, C-4
CHAIN f.unction, 2 -1 0
Character codes
ASCII, E-2. E-3
OS/S, E-l
Character mode, expanded, 4-6
Character packing format, 5-S
Characters, lower case, E-l
Circumflex (~) character, 4-5
CLOSE function, 2-S, D-9
Code, non-paged, D-10
Command Decoder
calling, 3-3
conventions, 3-1
error messages, 3-3
errors summary, C-7
example, 3-6
options, 3-3

output files, 3-4
special mode, 3-S, 3-9
tables, 3-4
COMMON area, 2-12
Control characters, OS/S, E-l
Conventions
Command Decoder, 3-1
OS/8, E-l
Core control block, 1=4, 2=11, A-5
Core image files (.SV format), A-5
Core origin, A-6
Core segment doublewords, A-6
Core size, PDP-8 computers, D-5
software, 1-6
Co-resident device handlers, 2-6
Creating files, 1-3
Data exchange in core, 2-12
Data field value, 2-2
Data transfer, 4-1, 4-2
DATE command, 1-3, 2-7
DECODE function, 2-9
DECtape operation, 4-1
Default file storage device, DSK,
0-1
Deletinq tentative files, 2-14
Device control word table, B-6
Device dependent operations, 4-4
Device handler
entry point, 2-14, 5-8
information table, B-5
residency table, 2-15, B-5
Device handlers
device dependent operations, 4-4
Card Reader (CDR), 4-7
Cassettes operation, 4-6
High-Speed Paper Tape Punch
(PTP), 4-5
High-Speed Paper Tape Reader
(PTR), 4-4
file structured devices operation,
4-11
T08E DECtape, 4-11
TM8E Magtape, 4-8
Device handlers, 1-1
calling, 4-1
co-resident, 2-6
inserting into OS/S, 5-5
loading dynamically, D-7
notes on loading, D-7
writing, 5-1
Device length table, B-7
Device names and numbers, 1-6
DEVICE pseudo-op, 1-7
Devices, file structured, 1-2
DF32 disk operation, 4-11

INDEX-l

sirec~ call!~g sequence, ~SR, 2-2
Directorles, file, 1-3
sirectory block structure format,
A-I
Girectory entries, A-2
Directory example, A-3
Directory segment, rewriting, D-9
Directory, system, 5-4
Dismiss USR from core, 2-12
Dot (.) used as system response, 1-6
Doublewords, core segment, A-6

Empty file entry, A-2
Empty files, 1-3
End-of-file card, 4-7
End-of-file condition, 4-2, 4-3
ENTER output (tentative) file
function, 2-6, D-9
Entry points for device handlers,
5-2
ERROR function, 2-11
Error messages, Command Decoder,
3-3
Error messages summary, C-l
Error returns, device handler, 4-2
Exit to Keyboard Monitor, 1-1
Expanded character mode, 4-6
Extensions of file names, 1-2
FETCH device handler function, 2-4,
4-1
File creation, 1-3
File directories, A-I
block format, A-I
entries, A-2
example, A-4
formats, A-4
number, A-3
size, A-3
File extension, omission of, 3-2
File length restriction, Command
Decoder, 3-5
FILENAME pseudo-op, 1-7
Files, 1-2
additional information words, 1-3
devices, 1-2
directories, 1-3
names, 1-2
types, 1-3
File structured devices operation,
4-11
Formats for
character packing, 5-3
command line, 3-1
directory block structure, A-l
files, A-4
FORTRAN Library File, A-7
input file, 3-2
Job Status Word, A-6

Form feed, 4-5
FORTRAN Library File Format, A-7
Functions, USR see USR functions
High-Speed Paper Tape Punch (PTP)
operation, 4-5
High-Speed Paper Tape Reader (PTR)
operation, 4-4
Horizontal tab, 4-5
Indirect calling sequence, USR, 2-2
Information words, additional, 1-3,
2-7
accessing, D-10
Input file format, 3-2
Input files, Command Decoder, 3-5
Input/output r~utines, F-l
Input table, Command Decoder, 3-9
INQUIRE function, 2-13
Inserting device handlers into
OS/8, 5-10
Job Status Word, 1-5, A-6
Keyboard Monitor, 1-1
error summary, C-3
KL8E terminal handler, 4-12
LAP pseudo-oPr 0-10
Layouts for OS/8 system, B-1
LINCtape operation, 4-7
Line Printer (LPT) operation, 4-5,
4-6
Load and start subprogram, 2-11
Loading device handlers dynamically,
0-7
Lock USR in core (USRIN), 2-12
Lo~ical blocks, 1-2
LOOKUP permanent file function, 2-5,
0-9
Lower case characters, E-l
Names of devices, 1-6
Names of files, 1-2
Number and size of OS files, A-3
Numbers of devices, 1-6
Numeric option, Command Decoder, 3-3
OOT breakpoint, 2-11
Operations, device dependent, 4-3
Options
Command decoder, 3-3, 3-6
Origin of core, A-6
Output files, Command Decoder, 3-4

INDEX-2

PAGE pseudo-op, D-IO
Permanent device name
Permanent fi:e, 1-3
deletion, 2-8, 2-9
entry, A-2
Physical bloc%s, 1-2
PIP, 3-5

~able,

Tables
Command Decoder, 3-4
device centrel word, B-6
device handler information, B-5
device handler residency, B-5
device length, B-7
permanent device name, 3-4
system device, B-4
user device name, B-4
TD8E DEC tape
operation, 4-11
Teletype operation, 4-4
Tentative files, 1-3
closing: 2-8
deletion, 2-4
entry, A-2
Terminal handlers
I-page, 4-4
2-page, 4-12

B-4

Program, see specific subject

notes, D-l
PRTC12-F used to convert DECtapes
to LINCtapes, D-6
Pseudo-ops
DEVICE, 1-7
FILENAHE, 1=7
Punch card codes, DEC026, D-3
Prograrr~ing

Records (definition), 4-1
outputting odd number of, 4-3
RESET system table, 2-14
Resident program layout, B-2
RESORC, B-7
Restrictions to USR calls, 2-2
RETURN key, 3-3
RF08 disk
operation, 4-11
RK8E handlers, 4-11
ROM (Read-Only-Memory), B-3
SABR prograrrming notes, D-IO
SAVE command, 1-4, 2-11
Scratch blocks, B-1, B-2
Signal user ERROR function, 2-11
Size of OS files, A-3
Software components, 1-1
Software core size, 1-6
Special mode of Command Decoder,
3-8
calling, 3-9
operation, 3-9
Standard USR call, 2-1
restrictions, 2-2
START command, 1-4
Starting address of program, 1-4
Storage space, additional, D-9
Stcrage words, 1-3
Sul::routine
examples, F-4
functions, F-l, F-2
listing, F-5
parameters, F-3
Summary of USR functions, see USR
functions
.SV file, 1-4
System DATE, 2-7
System device layout, B-1
System devices, 1-6
System device table, B-4
System halts error messages
surrmary, C-l
System table values, Command
Decoder, 3-7

Up arrow (t) character, 4-4
User device name table, B-4
User Service Routine (USR) , 1-1,
2-1
available location in area, D-9
calling, 1-6, 2-1
calling sequences, 2-2
errors summary, C-2
restrictions on standard call,
2-2
USR functions
CHAIN, 2-10
CLOSE, 2-8
DECODE, 2-9
ENTER, 2-6
ERROR, 2-11
FETCH, 2-4
INQUORE, 2-13
LOOKUP, 2-5
RESET, 2-14
summary, 2-3
USRIN, 2-3, 2-12
USROUT, 2-2
Vertical tab, 4-5
Wrap around memory, 4-3
Writing device handlers, 5-1
Word blocks, 1-2

INDEX-3

OS/8 Software Support Manual
DEC-S8-0SSMB-A-D
READER'S
NOTE:

CO~ll~ENTS

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