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DEC-T8-MRFA-D

September 1968

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Document:	Monitor
Order Number:	DEC-T8-MRFA-D
Revision:
Pages:	68
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OCR Text

TIME-SHARING SYSTEM
TSS/B Monitor
for the
PDP-B
PDP-B/I

For additional copies order No. DEC-T8-MRFA-D from Program Library, Digital Equipment
Corporation, Maynard, Mass.

Price $3.00

DIGITAL EQUIPMENT CORPORATION. MAYNARD, MASSACHUSETTS

First Printi ng, September 1968

The reader's attention is invited to the last two pages of this manual.
The How To Obtain Revisions and Corrections offers the reader a means
of keeping up-to-date with DEC's software. The Reader's Comments
card, when filled in and returned, is beneficial to both the reader
and DEC. Each card received is considered when documenting subsequent manuals, and where the comments imply or ask for assistance,
a knowledgeable DEC representative will contact the reader.

ACK NOWLEDGMENT
We wish to thank Dr. John McCarthy and his associates at the
Stanford Computation Center for their permission to use some
parts of the THOR User's Manual which describes a time-sharing
system for the PDP -1 computer.

CONTENTS
Page
CHAPTER 1
INTRODUCTION
1.1

Monitor Functions

1-1

1.2

TSS/8 User and Console

1-1

1.3

System Program Library

1-3

1.4

User Programs

1-3

1.5

User Files

1-4

1.6

System Configuration

1-4

1.6.1

Minimum Hardware Requirements

1-5

1.6.2

Hardware Options

1-5

1.6.3

Data Communication System, Type 680/1

1-6

CHAPTER 2
THE TSS/8 MONITOR
2.1

Monitor Services

2-1

2.2

Character and Data Flow

2-3

2.2.1

Character Transmission

2-4

2.2.2

General Input Routine

2-4

2.3

Permission and Switchboard Tables

2-5

2.3. 1

Permission Table

2-6

2.3.2

Switchboard Table

2-6
CHAPTER 3
MONITOR COMMANDS

3.1

Loggi ng In and Out

3-2

3.2

Console Manipulation

3-2

3.3

Device Allocation

3-3

3.4

Fi I e Control

3-3

3.5

Control of User Programs

3-5

3.5.1

Saving and Restoring Binary User Programs

3-6

3.6

Switchboard

3-7

3.7

Inter-System Communication

3-9

iii

CONTENTS (Cont)
Page
CHAPTER 4
INPUT/OUTPUT TRANSFER INSTRUCTIONS

4. 1

Program Control

4-1

4.2

File Control

4-9

4.3

Input Buffer Control

4-14

4.4

Output Buffer Control

4-16

4.5

High-Speed Paper Tape Reader

4-18

4.6

High-Speed Paper Tape Punch

4-19

4.7

DECtape

4-20

4.8

Automatic line Printer

4-21

4.9

Incremental Plotter

4-23

4.10

Card Reader

4-24
CHAPTER 5
ERROR DIAGNOSTICS

5. 1

User Program

5-1

5.2

System Interpreter

5-1
APPENDIX A
TSS/8 CHARACTER SET
APPENDIX B
SUMMARY OF COMMANDS

APPENDIX C
SUMMARY OF lOT INSTRUCTIONS
APPENDIX D
REQUIRED MODIFICATIONS
APPENDIX E
STORAGE ALLOCATION
ILLUSTRATIONS

1-1

User Console

1-2

Users Console Keyboard

1-2

1-3

System Configuration

1-5

2-1

Character and Data Flow

2-3

2-2

Permission Table

2-5

ILLUSTRATIONS (Cont)
Page

2-3

Switchboard Table

2-5

E-l

TSS/8 Storage Map

E-l

E-2

File Directories

E-2

HOW TO OBTAIN REVISIONS AND CORRECTIONS

Notification of changes and revisions to currently available Digital software and of
new software manuals is available from the DEC Program Library for the PDP-5, 8,
8/s, 81t, 8/L, UNC-8, the PDP-4, 7, and 9 is currently published in DECUSCOPE,
the magazine of the Digital Equipment Computer User's Society (DECUS). This information appears in a section of DECUSCOPE called "Digital Small Computer News".
Revised software products and documents are shipped only after the Program Library
receives a speci fic request from a user.
DECUSCOPE is distributed periodically to both DECUS members and to non-members
who request it. If you are not now receiving this information, you are urged to
return the request form below so that your name will be placed on the mailing list.

r- I

To: Decus Office,
Digita I Equi pment Corporati on,
Maynard, Mass. 01754

o Please send DEC US installation membership information.
o Please send DECUS individual membership information.
o Please add my name to the DECUSCOPE non-member mailing list.
Name _ __
Company
Address ________________ _

(Zip Code)

CHAPTER 1
INTRODUCTION

TSS/8 (Time-Sharing System for the PDP-8;1 Computer) is a general purpose stand-alone,
time-sharing system offering each of up to 32 users a comprehensive library of system, utility, and
service programs which provide facilities for compiling, assembling, editing, loading, saving, calling,
1
2
and debugging user programs on-line, and also two conversational languages, FOCAL and BASIC-8 •
The minimum hardware configuration is designed for eight users and includes the following:
a modified PDP-8/I or PDP-8 with 8K words of core memory, a RFOS Disk, a PT8/1 high-speed paper
tape reader, and Teletype control units for data communication (either four PTOSs or one 680/1 per
system). See Section 1.6 for a complete list of possible optional devices and for the configuration for
systems accommodating up to 32 users.
By segregating the central processing operations from the time-consuming interactions with
the human users, the computer can in effect work on a number of programs simultaneously. Giving
only a fraction of a second at a time to each program or task, the computer can deal with many users
seemingly at once, as if each had the computer to himself. The execution of various programs are
interspersed without interfering with one another and without detectable delays in the responses to the
individual users.

1.1

MONITOR FUNCTIONS
The heart of this time-sharing system is a complex of subprograms called Monitor. Monitor

coordinates the operations of the various units, allocates the time and services of the computer to users
and controls their access to the system. The allocation function includes scheduling the user's requests,
transferring control of the central processor from one user to another, moving (swapping) programs in
and out of core memory, and managing the user's private files.

1.2

TSS/8 USER AND CONSOLE
A TSS/8 user is any person running a computer program within TSS/8. He has an account

number assigned to him by the person responsible for the system which determines his identity for TSS/8
and identifies his files on a permanent basis. When he is using the system this number also identifies

1 FOCAL (FOrmula CALculator) is an on-line conversational interpretive program developed
by Digital Equipment Corporation.
2 BASIC-8 is a modified version of the elementary algebraic language developed at
Dartmouth College.

1-1

his console, his individual disk swapping track (a contiguous 4K section of disk) for temporary storage
of active programs, and whatever other facilities he may be using at any given time.
While the user is logged into the system, he owns at least one console (Figure 1-1) and one
4K disk track. The console consists of a keyboard (Figure 1-2), which allows the user to type information to his user programs and Monitor, and an output device, usually a Teletype printer, whi ch furnishes typed copy of program and Monitor output and user input.

Figure 1-1

User Console

G)G)CDCDCD(DgG)G)G)C)Q®
@G)Q~CVGJQG)G:)~®@@
8G)(f)G)G)6)QG)G)~c)®88

8G)G)G)QG)G)QG)C)C)8
[

SPACE

Figure 1-2 Users Console Keyboard

1-2

]

1.3

SYSTEM PROGRAM UBRARY
A comprehensive library of programs is available to all TSS/8 users. The library provides

facilities for assembling, compiling, editing, and debugging user programs. Any of the system, utility,
and service programs can be called into use by typing, in response to the dot typed by Monitor, the
cOrrlmand R and the assigned name of the programs. For example,
.R FOCAL
brings FOCAL into core from the disk and al.ltomatically executes FOCAL so that it begins typing out
its Initial Dialogue.
The System Program Library contains the following programs:
a.

Binary (BIN) Loader - used to load user programs into core memory from the console.

b. Symbolic Tape Editor - used to prepare, edit, and generate symbolic (source) programs
and program tapes from the console.
c. PAL III Symbolic Assembler - used to translate source programs written in the PAL III
language into object programs.
d. MACRO-8 Assembler - used to translate source programs written in the MACRO-8
language, containing macros and literals, into object programs.
e. Dynamic Debugging Technique (DDT-8) - used to aid the user in correcting errors in
stored user programs by allowing him to execute small sections at a time, to stop execution where he
wishes, and to change portions of his program, using the symbolic language of the source program or
machine language. The user may create an octal program using the DEPOSIT command.
Octal Debugging Technique (ODT -8) - used for the same purpose as DDT -8 (above)
f.
except that the user communicates in the octal representation of his program. ODT -8 requires less
core area than DDT -8, and can be loaded in either the upper or lower portion of core, depending
upon where the user's progralTl is loaded.
g. FORTRAN (4K) - used to compile and operate a user program written in the 4K version
of the FORTRAN language; compilation requires only one pass through the compiler.
h. FOCAL (FOrmula CALculator) - an on-line, conversational, interpretive program used to
solve complex numerical problems; used as a programming tool by students, engineers, and scientists.
i.
BASIC-8 - an elementary algebraic language, is an on-line, service program similar
to FOCAL used to solve complex numerical problems.

1.4

USER PROGRAMS
A user program is any program being run in user mode by TSS/8. When a user program is

being run by TSS/8 it is swapped into core memory from the user's disk track. Several programs may
be run by a regular process of bringing a program into core from the disk, allowing it to execute for a
short time, marking the state in which its execution is stopped, returning it to the disk, and picking up
the next user program.

1-3

User programs are serviced regularly on a "round-robin" basis. After a user program has been
executed, it is placed last in the order of user programs waiting to run. Each program is allowed to run
one quantum of time and then it is exchanged for the next user program. If only one program is in a
condition to run, it is allowed to run without interruption.
There are three ways in which a user can place a binary program on his disk track.

1.5

He may prepare an octal program at a console using a debugging program such as DDT -8,

He may load a previously saved core image, or

He may load the binary output file of a previous assembly or compilation.

USER ALES
Disk storage is divided into logical areas called files.

new files and extending, contracting, and destroying old files.

Facilities are available for creating
Files may contain textual information,

binary core images, or data in any standard format. The user can also protect his files against unauthorized access.
A user file directory (see Appendix E) ;s assigned to each user by the person responsible for
the system before the user first logs into the system. The user file directory is associated with the job
number assigned to the user by the Monitor each time the user logs in.
Files are composed of segments of disk storage. A segment can consist of from 200 to
8
20008 words. Files are at least one segment long and grow by adding additional segments to the end
of the file.

Each user may have access to up to four active files at any time. An internal fi Ie number,

through 3, is associated with each of the user's active fi les, and commands then operate in terms of

the internal file numbers. With this feature, a user may attach one of his files to an internal file number and then load system and utility programs which operate on his file without having to explicitly
call the file for each system or utility program used.

1.6

SYSTEM CONAGURATION
Depending upon the hardware configuration of a particular TSS/8, there can be from 1 to

32 users working with the system simultaneously. Each user has, in addition to system software, the
following resources: at least 4K words of core memory for execution of programs, and a corresponding
4K disk track for temporary storage of his core image.

1-4

1 .6. 1

Minimum Hardware Requirements
The minimum equipment requirements of the system are listed below (see Figure 1-3).
PDP-8/1 or PDP-8 with KT08/1 Time-Sharing Modifications
MC8/I-A Memory Extension Control and 4096 words
RF08 Disk Control
RS08 Disk
PT08 Asynchronous Line Interfaces, Dual (4)
PT8/1 High-Speed Paper Tape Reader
KE8/1 Automatic Multiply-Divider
CAB 8/IA Option Cabinet

(TELETYPE MODEL
33 OR 35)

CONSOLE CONTROL
680/1 OR PT08 'S

C
L

CPU

4K CORE

EXTRA
4K CORE

Figure 1-3

1.6.2

System Configuration

Hardware Options
The system can have a maximum of 32K of core memory. As additional fields of core mem-

ory are added they permit overlapping the running time of one user program with the swapping time of
another, expanding the resident Monitor to buffer a larger number of consoles, and reducing the amount
of Monitor overlay required.
With a minimum of 12K of core memory, the following options are available.
a.
file storage.
b.

Up to three DECdisks can be appended to increase the number of active users and their
Up to eight DECtapes can be appended for the use of private DECtapes by users.

1-5

Memory Parity

Extended Arithmetic Element (PDP-8/I only)

Power Failure

1 High-Speed Paper Tape Punch

1 Card Reader

1 Incremental Plotter

i•
I.

1.6.3

Li ne Pri Ilter
1 DA 10 Interface (PDP-10)
Bit Synchronous Communication Unit (Type 637)

1 Line Frequency Clock (required with PT08 1s)

32 Teletype Controls (PT08 1s or 680/1)

Data Communication System, Type 680/1
The Data Communication System, Type 680/1, is used in full duplex mode. It consists of a

Data Line Interface Unit (DL8/1), a Serial Line Multiplexer Unit (685), and other devices connected
to form a data link and message switching system between the user consoles and the central processor.

1-6

CHAPTER 2
THE TSS/8 MONITOR

2.1

MONITOR SERVICES
The TSS/8 Monitor is composed of the following routines:
lOT Trap Handler

Error Message Handler

Scheduler

Buffer Handler

Storage Allocator

680 Service

Overlay Control

Disk Service

System Interpreter

Optional Device Service

Fi Ie Control
With the above routines, Monitor provides services which may be divided into three broad categories:
a.

Device Service

Scheduling and Activation

Communication

On an interrupt basis the Device Service routines receive information from all input devices,
parcel that information out to the appropriate buffers, and inform the Activation routine when a user
program must be activated to receive its information. The Device Service routines accept output from
user progralT'S, buffer it, and send it to output devices whenever they are able to receive it.
Activation is handled by a "round-robin" scheduling algorithm with the exception that programs with disk requests pending are run out of tum to optimize disk usage. The Activation routine
decides whether to remove the current program from core, and if so, which program is to be run next.
A user program is, at any point in time, in one of the following states.
a. Running - The user program is in execution. It continues execution until its quantum
has expired or until it issues an input/output (I/O) request that cannot be satisfied immediately.
b. Active - The user program is ready to run and will be swapped into core when its turn
comes. A program can become active when
(1) An output buffer is almost empty, thus assuring continuous output of information,
(2) An input buffer is almost full,
(3) Input requested by a user has arrived,
(4) A user determined activation condition has been satisfied, or
(5) When the user commands the system to begin execution.
c. Waiting - In this state, the program would be active except that it is waiting for the
completion of some I/o request or special condition.
d. Dormant - The program is not being entered into the "round-robin." The user may be
communicating with Monitor or the program may be dismissed for a variety of user determined reasons.

2-1

A program may be swapped out of core memory for any of the following reasons.
a.

The quantum has expired; the program moves from the running state to the active state.

b. The program has requested the quantum be termi nated; the program moves from the
running state to the active state.
c. The program has fi lied an output buffer, has requested input and the input buffer is
empty, or has requested a special dismissal condition; the program moves from the running state to
the waiting state.
d. The program has tri ed to execute an i lIega I i nstructi on; the program moves from the
running state to the dormant state.
Monitor checks all incoming characters for the call (CTRL/B) character. When the call
character is encountered, Monitor routes all subsequent characters up to and including the first carriage
return (CR) to its System Interpreter's input buffer. Monitor's System Interpreter routine performs the
foil owi ng servi ces.
a. Verifies the user's name and account number when he logs in and provides him with a
disk track to store user programs. It releases facilities owned by the user when he logs out.
b.

Parcels out extra consoles and input/output devices.

Provides commands for creating, opening, and maintaining the user's files.

d. Allows the user to save all or part of his binary user program for future use and reference,
and restores it with its state unchanged.
e.

Provides accounting of console time and user program run time.

f.
Provides the user with information about the state of his program while running, as well
as information about the state of the character control tables.
g.

Provides commands for calling the various utility programs.

Communications to the System Interpreter are automatically duplexed. That is, all characters
from a keyboard to the System Interpreter appear on that console's printer, regardless of the switchboard
setting. (See Section 2.3.)
The System Interpreter may be receiving messages from many keyboards and user programs,
therefore, it must be run often. Consequently, it occupies its private position in the "round-robin,"
being activated whenever there are characters in its input buffer.
Monitor has two Phantom routines: Error and File Control. Phantoms are privileged routines
which run in place of a regular user program in the "round-robin." The time the Phantom takes to
perform its service is charged to that user program lIpon which it is servicing.
The Error Phantom prints all error messages for running user programs. Printing a lengthy
error message may require several quanta; the use of the Error Phantom punishes the user responsible
for the error and no one else.
The File Control Phantom handles such modifications to the file directory as creating,
lengthening, renaming, and destroying files. This Phantom is brought into operation when a user program executes certain lOT instructions or when Monitor is acting for the user program.

2-2

2.2

CHARACTER AND DATA FLOW
When a user logs into the system his account number is associated with a job number, and

that job number is then associated with a disk swapping track and the console(s) he owns. The account
number establishes ownership of the input buffer attached to the user program on his disk track and the
output buffers attached to the printers of his consoles.
Monitor provides for communication among the users, user programs, and Monitor. Data
communication is illustrated in Figure 2-1. Communication is provided through the lOT instructions.
When a program executes certain lOT instructions, Monitor picks up locations in the user program as
parameters to service routines. These routines may simulate input/output to the on-line device, control
or release ownership of devices, handle character communication, or return information to the user
program by filling registers within the program. Through lOT instructions, the user program can make
its wants known and Monitor can inform the user program of any variation in the time-sharing system.

9
ISK
TRACKS

,
SWAPPING

REQUEST FOR SPECIAL
SERVICE OR I/O

USER

CONSOLE

USFR __

PRC

CHARACTER
CO"TROL TABLES

I.~

...

...J

GENERAL

KEyBOARD

f-- -- INPUT- - f--

cr
~

ROUTINE

PRINTER
CDM~A"D

LANGUAGE
AND
SERV'CE

RFQII.-q FOR
SI·
...
SERVICE

Ok :._

OTHER

Fi gure 2-1

I/O

Ie---

Character and Data Flow

2-3

PHANTOM
SERVICE

2.2.1

Character Transmission
The input/output transfer instructions provide character transmission. Characters are gener-

ated by users typing at keyboards or by user programs typing out. Characters go into input buffers to be
read by user programs or to output buffers to be printed on Teletype printers. A switchboard device sets
up useful character transmission paths, whereby any character source (keyboard and program) may, with
permission, send to any character sink (input and output buffer). To insure that unwanted connections
are not made, using the appropriate command to Monitor the user owning any character sink may grant
or deny permission for connection into that sink.
A console may be thought of as two disassociated devices, a keyboard and a printer. To each
printer there is an associated character output buffer numbered I ike the consoles, O-K. When a character is placed into output buffer number n, Monitor causes that character to be printed on printer
number n.
Each job has an associated character input buffer numbered like the job, O-P. When user
program number n executes a keyboard input lOT, the next character waiting in input buffer number
n is placed in the user program's accumulator (AC).

This character may be a data character,

the source of the last data character, or the time that the last data character was placed in the
input buffer.

2.2.2

General Input Routine
The General Input Routine (GIR) provides and controls character input to user programs.

Programs vary in how promptly they must pay attention to incoming characters. In the preparation of
a file, characters are added to the input buffer when typed; when the input buffer gets full the program
receives all the characters at once and transmits them to the disk. In this case, the user's program
is activated only when the input buffer gets full. With a program whose operation is controlled from
the keyboard, however, every character typed goes directly to and influences the program's action.
Through lOTs, the user program can specify under which conditions the input characters
will cause the program to be activated. These conditions are called delimiters. A delimiter may be
some specific ;'ype of character appearing in the input or it may be a change in the source of characters;
the input buffer becoming full is always a delimiter.
GIR places all incoming characters in the user's input buffer until a delimiter is encountered.
When a delimiter appears, the user program is always alerted and usually activated to receive all the
characters in the input buffer. This is done by setting the delimiter bit (status register 1) to one. If
the Wait Mask (see Chapter 4, Set Wait Mask) is set to one, the user program will be activated.

2-4

2.3

PERMISSION AND SWITCHBOARD TABLES
Characters originating from any keyboard or from any user program typing out can, with

permission, be placed in any or all of the K output buffers or any or all of the P input buffers. The
Permission Table is the device with which a user controls which character sources may place characters
in which of his buffers; the Switchboard Table controls the actual routing of these characters.
The Permission and Switchboard Tables are organized as matrices (see Figures 2-2 and 2-3).
The rows represent character sources, that is, keyboards and programs typing out. The columns represent
character sinks, that is, input and output buffers. Along the rows are the K keyboards and P programs.
Along the columns are the P input buffers and the K output buffers.

J "PUT

KEyBOARD
INPUT

PROG"."
OUTPUT

BUFFERS

OUTPUT

BUffERS

R. ,.

R.l

S.Y

S.l

Figure 2-2

Permission Table

INPUT

OUTPUT

KEyBOARD

BUFFERS

INPUT

P.W

P,X

PROGAM
OUTPUT

o.w

o.x

Figure 2-3

Switchboard Table

2-5

2.3.1

Permission Table
The Permission Table acts as the matrix of permitted connections. For example, if the bit R,

Y is a one, it means that the owner of input buffer number Y allows keyboard number R to place characters in it. Similarly, if bit S,Z is a one, it means that the OWner of output buffer number Z (printer
Z) has agreed to allow job number S to type out characters onto printer Z. In general, if a bit in the
Permission Table is a one, the owner of the entity specified by the column has granted permission for
the entity specified by the row to place characters in his sink.
The fact that permission for a given character routing has been establ ished does not necessarily mean that characters automatically flow along that route. A route to a buffer is not established
unless the owner of the keyboard or program sets the Switchboard Table.

2.3.2

Switchboard Table
The Switchboard Table acts as a matrix of requests by the owner of a character source that

characters emitted by that source appear in some sink. If bit Q, W is a one, characters coming from
program number Q typing out will appear in input buffer number W. Similarly, if bit P,X is a one,
characters typed on keyboard number P will appear in the output buffer of printer number X. In general,
if a bit in the Switchboard Table is a one, characters emitted by the source specified by the row will
appear in the sink specified by the column. Attempts to set bits in the Switchboard Table are automatically checked against the Permission Table. Only if the corresponding bit in the Permission Table is a
one will the system allow that bit to be set in the Switchboard Table. The Switchboard Table may be
regarded as the final arbiter of character routing.
Bits in the Permission and Switchboard Tables may be set, reset, and read by using Monitor
commands or by an lOT instruction which the system executes interpretively.
The Permission and Switchboard Tables are automatically set up for normal use when a user
logs into the system. This configuration is:
a.

The user gives permission for his keyboard to send characters to his user program's input

buffer.
b. The user gives permission for his keyboard to send characters to his printer's output
buffer (this condition is known as duplexing). Whether the characters actually appear depends upon
the corresponding Switchboard setting. Normally, the Switchboard is not set to handle the input before it is printed.
c. The user gives permission for his program to type characters to its own input buffer.
(The Switchboard determines whether characters typed out will in fact be sent to the input buffer.)
d.

The user gives permission for his program to send characters to his printer's output buffer.

2-6

e. The Switchboard is set so that characters from the user's keyboard will be placed in the
user program's input buffer.
f. The Switchboard is set so that characters typed out by the user program will be placed
in the program's output buffer.
The user is, of course, free to modify and add to these settings.
The Switchboard generality finds application in:
a. Duplexing - Characters typed at a keyboard can be printed on any console without user
program intervention.
b. Interprogram Communication - User programs can communicate with each other and
with Monitor. Thus, several user programs may run as one system coordinating their separate tasks
through character communication.
c. Interconsole Communication - Users at consoles can set up general links for conferences,
teaching, monitoring, or for any other reason.
d. Multiple Consoles - User programs may receive characters from and send characters to
more than one console. This allows a user program to act as a time-sharing system within TSS/8, controlling its own set of consoles, as in teaching machine monitors.

2-7

CHAPTER 3
MONITOR COMMANDS

A Monitor command is a string of characters terminated by a semicolon (;) or a carriage
return (RETURN key). Commands to Monitor are typed on the Teletype keyboard by the user or output
by the user program, with each command beginning with a command name. In some cases, the command
name is the entire command, in which case it is followed directly by a terminator. In other cases, the
command name is followed by a space, one or more parameters, and then a terminator. For example,
• TIME

(requesting the time of day. This command was terminated by the
RETURN key)

• TIME C1

(requesting the processing time used by job C1. Terminated by the
RETURN key)

Only enough characters need be typed in the command name to uniquely identify the command name.
For example,
LOGI

for LOGIN

LOGO

for LOGOUT

More than one command may be typed on a line, with all but the last command being terminated by a semicolon; the last command is terminated by the RETURN key. For example,
.OPEN C1 Sl C2; LOAD C 1 Sl; START C1
(The abbreviated parameters are explained below.)

NOTE
Commands are executed when the RETURN key is typed,
which explains why the last command on a line must be
terminated by the RETURN key.
As shown in the above examples, each command or line of commands is typed after the dot
typed by Monitor. The dot is typed by Monitor when it is ready and available to accept commands
from the user.
Parameters may be typed as octal numbers, decimal numbers, character strings, or single
letters. In the following descriptions of Monitor commands the parameters are coded as follows.
C1, C2,

represent octal numbers

D1, D2,

represent decimal numbers

S 1,

S2,

represent character strings

Ll,

L2,

represent single letters

3-1

3.1

LOGGING IN AND OUT
Logging in and out of TSS/8 is a function performed by Monitor's System Interpreter routine.

When a console is in the free state, a prospective user may attempt to log into the system.
LOGIN Cl Sl;

This is a request by a user to log into the system. If the console from
which the command is typed is free, there is an available disk track,
and the two parameters following the command LOGIN form a legitimate account number and password, then the user wi II be logged into
the system.
Cl is the user's account number
S 1 is the user's password
At the time of login, the Switchboard is initialized to the normal
operation setting. However, Mon itor diverts all characters typed to
the System Interpreter until the user gives a command that indicates
otherwise.

3.2

LOGOUT;

This is a request by a user to logout of the system. It disconnects all
consoles and disk tracks that he owns, places his programs in the free
state, and resets the Switchboard. It also writes an account record
on the disk showing how much computing time (processing time) and
console time was used by the user's program(s).

TIME Cl;

This is a request for Monitor to type out the computing (processing)
time used since login. If job Cl is not specified, the job owning the
console is assumed. If requested before login and if no job is specified, the time-of-day is typed. If, at any time, job 0 is specified,
the ti me-of-day is typed.

CONSOLE MANIPULATION
ASSIGN K Cl;

This is a request for console number Cl to be added to those consoles
already owned by the requesting user.
K denotes console
Cl is the console number
If the console is free, it will be given to the user and the user's
Switchboard settings will be augmented by those additional entries
which put the new console in the normal state with respect to its
own printer and the program on the user's disk track. Cross settings
for inter-console connectiorts are left to the user's discretion.

SLAVE Cl;

This command causes console number Cl to be slaved. This means
that console number Cl will be unable to communicate with Monitor,
and the system will ignore the call (CTRL/B) character from that
console. However, the console may serve as an input/output device
for the user's program. Monitor checks to make sure that the requesting user owns the console he wishes to slave. It is illegal to slave
every console that a user owns.

3-2

3.3

UNSLAVE Cl;

This command restores a slaved console to normal status. After this
command, console number Cl will be able to communicate with
Monitor. The user must own the consol e to unslave it.

RELEASE K C 1;

This command releases console number Cl and puts it in the free
state. Monitor checks to make sure that the requesting user owns
the console he wishes to release. When the console is released,
the Switchboard is reset and the input and output buffers are cleared.
The user must own the console to release it.

DEVICE ALLOCATION
ASSIGN Ll;

This is a request for access to the devi ce specified by Ll.
Ll = R
P
C
L
I

for paper tape reader
for paper tape punch
for card reader
for I i!"le pri nter
for incremental plotter

If device Ll is not busy, it will be allocated to the user program
issuing the command. If device Ll is busy, the job number of the
user having possession is returned. A RELEASE Ll; or LOGOUT;
will release the device.

ASSIGN D Cl;

This command is the same as ASSIGN Ll;
D denotes DECtape unit
C 1 is the unit number of the DECtape unit

RELEASE L1;
RELEASE K Cl;
RELEASE D Cl;

3.4

Each of these commands will annul the current assignment of the
specified device.

FILE CONTROL
OPEN Cl Sl C2;

This command establishes association between an internal file number and a file. After this command is given, the file of account
C2 with the name Sl is associated with internal file number Cl.
The internal file number specified must be between zero and three
inclusive. If C2 is not specified, the account number of the current user is assumed.

CLOSE Sl;

This command closes the files specified by Sl.
Sl is a list of internal file numbers separated by spaces
After this command is given, no writing can be done on the files
specified, and the associations between the internal file numbers
and the files are broken.

3-3

CREATE 51;

This command causes Monitor to create a new file which is to have
the name 51, if there is available file storage. At the time of
creation, Monitor will enter the name of the new file and the date
of creation into the owner's file directory (see Appendix E) and set
the protection mask to 17. Example:
CREATE NEWF;

RENAME C1 51;

This command renames a file. The file to be renamed must be already open and associated with internal file number C1. Its new
name will become 51. Example:
RENAME 1 FOO;

REDUCE C1 01;

asks Monitor to create a new file
named NEWF. If there is no more
file storage, Monitor will so inform
the user (see Chapter 5).

assume that file NEWF has been
opened to internal file number 1;
this command will change the name
of that file from NEWF to FOO.

This command reduces the length of a file. The file which is to be
shortened must be open and associated with internal file number C1 •
01 is the number of segments to be removed from the end of
the file.
If 01 is greater than or equal to the number of segments in the fi Ie,
the file is deleted from the directory. Example:
REDUCE 2 2;

EXTEND C1 01;

assume file TT13 is opened to internal
file number 2; this command then removes 2 segments from its end and
returns those segments to free storage.

This command extends the length of a file. The file which is to be
lengthened must be open and associated with internal file number
C1.
01 is the number of segments to be added to the end of the
file.
If there is space available, Monitor will lengthen the file as
requested.

PROTECT C 1 C2;

This command changes the file protection mask of a file. The file
to be protected must be open and associated with internal file
number C1.
C2 is the new file protection mask.
For file protection, the 12-bit account number is partitioned into
a project number (high order 7 bits) and a programmer number {low
order 5 bits}. Examples:
C2 = 1

read protect against users whose project number
differs from owner's

3-4

C2 = 2

write protect against users whose project number
differs from owner's

C2 = 4

read protect against users whose project number is
same as owner's

C2 = 10 write protect against users whose project number is
same as owner IS
C2 can be the sum of any of the above values.
This command is illegal for all users except the owner. Example:
PROTECT 1 3;

F C1;

read and write protect internal file 1
against access by any user whose project number differs from the owner IS.

This command causes Monitor to print out the current state of the
association of the user's internal file number C1 with the file. The
response format is
C1 Sl C2 D1
where
C1 is the owner's account number
S 1 is the file name
C2 is the protection mask
D 1 is the number of segments

3.5

CONTROL OF USER PROGRAMS
START C1;

This command begins execution of a user program at location C1.
In addition, the command resets the Switchboard so that all characters typed from either a keyboard or program directed into the
user program's input buffer are no longer intercepted by the System
Interpreter. The accumulator (AC) and link are cleared and the
user's interrupt system is turned off.

START;

This command restarts a user program. If Monitor has been called
during the execution of the user program, the complete state of the
program is saved including the location of the next instruction to
be executed. When the START command is giV'en, the programls
state is restored and the program continues execution where it left
off. As in the START C1; command, characters intended for the
user programls input buffer are no longer intercepted by the System
Interpreter.

DEPOSIT C1 C2 ••• Cn; This command stores C2 in location C1, C3 in location C1+1,
Cn in location C1+n-1.

... ,

n is equal to or less than 10 decimal.

A user can load a binary user program using the DEPOSIT command,
although it is much easier using DDT -8. This command is useful
when making small patches to stored programs.

3-5

EXAMINE Cl 01;

This command causes Monitor to type the contents of the 01 locations
starting at location Cl.
01 is equal to or less than 10 decimal.
If 01 is not specified, the contents of location Cl is typed.

3.5. 1

Saving and Restoring Binary User Programs
The SAVE, LOAD, R and RUN commands leave file Sl open on internal file 3, turn the

user's interrupt system off, and reset the Wait Mask to its initial value.
SAVE Sl;
SAVE Sl Cl;
SAVE Sl Cl C2;
SAVE Sl Cl C2 C3;

These commands write portions of the user's core image onto a file
whose name is Sl.
C1

is the fj Ie address of the first word to be written; if
not specified, the entire 4K is written on the first
4096 words of the fi Ie.

is the core address of the first word to be written; if
not specified, all 4096 words are written.

is the core address of the last word to be written; if
not specified, 7777 is assumed.

Example:
SAVE NEWF;

writes core words 0 through m7 on
words 0 through 7777 of file NEWF.

LOAD C1 Sl;
LOAD Cl Sl C2;
LOAD C1 Sl C2 C3;
LOAD Cl Sl C2 C3 C4; These commands read certain portions of the file whose owner's
account number is Cl, and whose file name is Sl into core.
C2

is the file address of the first word to be read; if not
specified, words 0 through 7777 are read into words
o through 7777.

is the core address of the first word to be loaded; if
not specified, all 4096 words are loaded.

is the core address of the last word to be loaded; if
not specified, 7777 is assumed.

Example:
LOA. 0 NEWF 5 10 17; loads words 5 through 14 into words
10 through 17 respectively.
R Sl;

This command is equivalent to
OPEN 3 Sl 2; LOAD 2 Sl; START 0
which loads program Sl from the System Library (account 2) and
starts the program running. The accumulator (AC) and link are
cleared.

3-6

RUN Sl;

This command is equivalent to
OPEN 3 Sl; LOAD Sl; START 0
The accumulator (AC) and link are cleared.

RUN Cl Sl;

This command is equivalent to
OPEN 3 Sl Cl; LOAD Cl Sl; START 0
The accumulator (AC) and link are cleared.

3.6

S·,

This command stops the execution of the user program, saves its
complete state, and sets the Switchboard so that all characters
directed to the program's input buffer will be intercepted by
System Interpreter.

WHERE;

This command causes Monitor to type out the current state of a user
program's location counter, accumulator, I ink, and switch register.

USER;

This command causes Monitor to type out the number of the job and
devi ces owned by the user.

USER Cl;

This command causes Monitor to type out the numbers of the devices
owned by user Cl. If job 0 is specified, the numbers of unassigned
devi ces are typed.

SWITCH Cl;

This command sets the user's switch register to C 1.

SWITCHBOARD
Using Monitor commands the user may set, reset, and read any given bit in either the Per-

mission Table or the Switchboard Table. See Section 2.2.1 Character Transmission and Section 2.3
Permission and Switchboard Tables for a description of the meaning of bits in these tables.
SET L1 L2 Cl L3 C2;

This command sets a bit in either the Permission or Switchboard
Table to a one.

L1 = P
S
L2 = K
P
Cl
L3 = I

o
C2

denotes Permission Table
denotes Switchboard Table
denotes keyboard
denotes user program
is the octal number of the keyboard or program
denotes input buffer
denotes output buffer
is the octal number of the buffer which is to receive
the characters from the character source.

Monitor checks for appropriate ownership to decide whether it will
allow the connection to be made. The ownership of the character
source is used to determine legality in setting the Switchboard Table
while the ownership of the character sink is used in setting the Permission Table. Examples:

3-7

SET P K 13 0 12;

requests that keyboard number 13 be
given permission to write on the printer
(output buffer) of console 12.

SET S P 4 I 16;

informs Monitor that job number 4
would like to type out characters into
the input buffer of user program 16.
This request will be granted only if
user 16 has previously given permission
by SET P P 4 I 16; or by the equivalent
lOT instruction (SSP).

RESET Ll C2 Cl L3 C2; This command is identical in all respects to the SET command above
except that the bit indicated by the parameters will be set to zero
instead of one.
READ L1 L2 Cl L3 C2;

This command uses the same parameters to specify a bit in either the
Pennission or Switchboard Table as in the SET and RESET commands
above. Monitor will type out the value of the bit.

DUPLEX;

This command is a shorthand command to set the Switchboard Table
so that characters typed 011 the keyboard from which this command
is issued will appear on the printer of that console. Example:
DUPLEX;

ALLOW Cl;

This command is shorthand to indicate that a user is given permission
for keyboard number Cl to place characters in the output buffer of
his console. Example:
ALLOW 4

LINK Cl;

if the keyboard issuing this command
is number 16, then this command is
equivalent to SET S K 160 16;

assume that this command was issued
from keyboard number 27, then it is
equivalent to SET P K 40 27;

This command is given by a user who wishes to communicate with a
console other than the one at which he is setting. This command is
legal only if the owner of the console has set the Permission Table
so that he will accept characters from the requesting console into
his printer's output buffer. The command is shorthand for the command ALLOW Cl; followed by the command to set the Switchboard
so that characters from the requesting console will be placed in
output buffer number Cl. Example:
LINK 32;

3-8

assume that the console which issued
this command was number 7, then this
command would be legal OI1ly if the
owner of console number 32 had previously set the Pennission Table to
all ow keyboard 7 access to that output
buffer. He could have done this with
ALLOW 7; or by SET P K 7 0 32; or by

an equivalent lOT instruction executed
by his program. If that permission has
been granted, the LINK command is
equivalent to the following two Switchboard commands: SET P K 32 0 7;
(ALLOW 32) and SET S K 7 0 32;

3.7

INTER- SYSTEM COMMUNICATION
In those TSS/8 systems having a local connection to a PDP-10 Time-Sharing System or a

Synchronous Data Communication System (Type 637), the input to the user's input buffer and program
output is scanned for the character sequences CTRL/B CTRL/X and CTRL/B CTRL/Y, respectively. All
characters up to the next CTRL/B are diverted to the PDP-10 or 637 System, whichever the case may be.
Characters from the PDP-10 and 637 System are directed into the user's input buffer.

3-9

CHAPTER 4
INPUT/OUTPUT TRANSFER INSTRUCTIONS

Whenever a user program executes an input/output transfer (lOT) instruction (an instruction
of the form 6XXX) the system traps the instruction and transfers control to a system service or simulation
routine. These routines accomplish special tasks, set up parameters for the system, and perform input/
output for the user program.
lOT instructions may be separated by function into three types:
a. Input/output instructions available on the standard PDP-8/I without a time-sharing
monitor - when a user program executes one of these lOTs, TSS/8 simulates an input/output function
similar to the function of the lOT instruction on the standard PDP-8/1. Some standard PDP-8/1 lOT
instructions are illegal in TSS8 (see Appendix C for a summary of legal lOTs).
b. lOT instructions to request input/output service from TSS/8 unavailable on the standard
PDP-8/1 - these include requests for DECdisk, DECtape, high-speed paper tape reader and punch,
card reader, and console character handling.
c. lOT instructions which call subroutines to set user parameters or to alter the time-sharing
environment for a particular user program - an alteration may, for example, include requests to add
or release facilites or to change mode of character handling.
An lOT instruction usually acts as a subroutine call. Therefore, depending upon the specific
lOT instruction, parameters may be loaded into the accumulator (AC) before execution of the lOT. In
some cases, the parameter in the AC acts as a pointer to a parameter block in the user's program. If
the system has to return information to the user's program, it returns that information in the AC or in a
block of locations in the user's program (the beginning address of this block is in the AC).

4. 1

PROGRAM CONTROL
Check Status (CKS)

Octal Code: 6200

Operation: There are three status registers, STRO, STR1, and STR2. All three registers are
read by the CKS instruction, and the accumulator (AC) is cleared. Before executing CKS,
load the AC with the address of a 3-word block. Executing CKS will store in
Word 1:
Word 2:
Word 3:

STRO
STR1
STR2

The formats of these registers are:
STRO Bits

Run Bit

1
2

PI Enable
Source

Unconditional run (this bit is turned on when the program is
started by the System Interpreter)
ION has been executed by user program
Input buffer source is being recorded

4-1

STRO Bits

3
4
5
6
7
through

Time
Binary
JSIOT
JSIOTC

Input buffer time is being recorded
Card reader mode: alphanumeric (0), binary (1)
Non-resident lOT call (system use only)
Copy lOT results to user (system use only)

Error Code

Bits 7 through 11 specify a system error code

Timer
File 0
File 1
File 2
File 3
Delimiter
Keyboard
Telepri nter
Reader
Punch
Error
Wait

Time is up
Internal file 0 is not busy
Internal fi Ie 1 is not busy
Internal file 2 is not busy
Internal file 3 is not busy
There is a delimiter in the input buffer
There is a character in the input buffer
Output buffer is not full
Character in reader buffer
Punch buffer is not full
System error detected, code in bits 7 through 11 of STRO
Job is not waiting

11
STR1 Bits

o
1
2
3
4
5
6
7
8
9
10
11

STR2 Bits

o
1

2
3
4

5
6
7
8
9
10
11

Plotter
DTO Flag
DTO Error
DTl Flag
DTl Error

Plotter flag
DECtape flag unit 0
DECtape error flag unit 0
DECtape flag unit 1
DECtape error flag unit 1
Unused
Card Reader Character in card reader buffer
CR No Ready Card reader not ready
CR End File Card reader end of file
LP Error
Li ne pri nter error
LP Done
Line printer done
Unused

Set Interrupt Mask (SIM)

Octal Code: 6000

Operation: TSS/8 simulates the PDP-8 program interrupt system for the user. A user program
may request this mode of operation by executing the ION instruction. A simulated interrupt
wi II cause an i mmedi ate transfer to Iocati on 1 of the user program. The user's current location (Program Counter) before the interrupt, is stored in location 0 and the interrupt system

4-2

is disabled (bit 1 of STRO = 0). If the instruction following the ION is a JMP or JMS instruction, it is simulated by the system before returning control to the user's program.
The SIM instruction enables the user program to set those conditions which will
result in simulated program interrupts. The system provides a mask called the Program Interrupt Mask, which has the same format as the two status registers STR1 and STR2 (see CKS).
Before executing the SIM instruction, load the AC with the address of a 2-word
block containing the mask. After executing the SIM instruction, a bit match between the
status registers and the Program Interrupt Mask will result in a simulated interrupt if the
interrupt system is enabled. The user's program may do a CKS instruction to determine the
cause of the interrupt.
The Program Interrupt Mask is normally set to

0074
7677
and is reset only on LOGOUT. The AC is cleared by SIM.

Read Interrupt Mask (RIM)

Octal Code: 6003

Operation: The Program Interrupt Mask is read into two locations starting at the location
whose address is in the AC, and the AC is cleared.

Interrupt Turn On (ION)

Octal Code: 6001

Operation: This instruction enables TSS/8 to respond to a user program interrupt request by
setting bit 1 of STRO = 1. If the user interrupt is disabled (bit 1 of STRO = 0) when this instruction is given and the following instruction is a JMP or JMS instruction, TSS/8 executes
it, then enables the interrupt by returning control to the user program. This instruction has
no effect if given when the user interrupt is enabled.

Interrupt Turn Off (IOF)

Octal Code: 6002

Operation: This instruction disables the user program interrupt system by setting bit 1 of
STRO = O.

Set Wait Mask (SWM)

Octal Code: 6005

Operation: The user program may request to be dismissed until some condition has been met.
This is done by setting a mask through which the system will observe the status register of the
user program. Load the AC with the address of a 2-word block containing 1 bits in the desired

4-3

wait conditions. The two words are inclusively o Red with the wait mask and the AC is
cleared. In general, flag test lOTs whose skip condition is not met and requested I/O
operations which cannot be performed immediately, cause the program to be dismissed until
the condition is met.
For example, suppose it is desired tl-at the user program be dismissed until any
character is typed, then
TAD MASK
SWM
KSF
MASK,

0040
0000

would have the desired effect.
The normal setting of the Wait Mask is
0001
7767
and is reset on LOGIN, SAVE, LOAD, R and RUN commands.

Clear Wait Mask (CWM)

Octal Code: 6006

Operation: Same as Set Wait Mask (SWM) except that the selected bits are cleared and
the AC is cleared.

Read Wait Mask (RWM)

Octal Code: 6007

Operation: The contents of the user's Wait Mask are read into two successive locations beginning at the word whose address is in the AC, and the AC is cleared.

Wait (WAIT)

Octal Code: 6410

Operation: The user's program is dismissed until it is re-scheduled by some status bit;Wait
Mask match. The user may read the status registers to determine the restart conditions.

User (USE)

Octal Code: 6421

Operation: Return in the AC the number of the current job.

4-4

Console (CON)

Octal Code: 6422

Operation: Return in the AC the smallest unit number of the unslaved consoles assigned to
the job whose number is in the AC. If the AC is 0, the number of an unassigned console is
returned; if it does not exist, -1 is returned.

User Run Time (URT)

Octal Code: 6411

Operation: Returns the total run time of the user program in the two locations starting at the
location whose address is in the AC. The AC is cleared.

Ti me-Of-Day (TOD)

Octal Code: 6412

Operation: Returns the value of the System Clock in the two locations starting at the location whose address is in the AC. The AC is cleared.

Return Clock Rate (RCR)

Octal Code: 6413

Operation: The number of milliseconds per clock tick is returned in the AC.

Date (DATE)

Octal Code: 6414

Operation: Returns the date in the AC. The format of this 12-bit number is
DATE=((YEAR-1964)*12*(MONTH-1 »*31+DAY-1

Skip On TSS/8 (TSS)

Octal Code: 6420

Operation: This instruction is used by programs which run under both TSS/8 and a standard
PDP-8/I. Under TSS/8, the instruction following TSS will be skipped. On a standard
PDP-8/1, the lOT has the effect of a NOP instruction.

Halt (HLT)

Octa I Code: 7402

Operation: This instruction is used to stop the user program and to pass control to the System
Interpreter. Executing HLT is exactly equivalent to typing CTRL/B S RETURN. HLT may be
micro-coded with other group 2 IOTls (see Small Computer Handbook, C-800).

4-5

Quantum Synchronization (SYN)

Octal Code: 6415

Operation: Upon execution of this instruction, the system will dismiss the user program and
set it in the run state so that it will be run again next time through the "round-robin. "
Ordinari Iy, this instruction is used to insure a full time quantum to perform some critical
operation.

Set Timer (STM)

Octal Code: 6416

Operation: The system provides a clock time for each user program. By means of this lOT,
the timer may be set to "fire" after a specified number of clock ticks have elapsed.
Load the AC with the time in ticks to prime the timer. Upon execution of the STM
instruction, the system sets the timer to "fire" in the specified number of ticks, and turns the
timer bit (bit 0) in status register 1 to 0 and clears the AC. After the specified time has
elapsed, the system turns bit 0 back to 1.
The timer mechanism may be used three ways: 1) The user may set the time going
and use the CKS lOT to find out when the time is up 2) The timer may be used with the Wait
feature.
TAD C5000
STM
TAD MASK
SWM
MASK,
C5000,

/prime timer with 5000 ticks

ISet the Wait Mask to check bit 0
lof status register 1

4000
0000
5000

Here the user program will be dismissed until 5000 ticks have elapsed 3) The time may also
be used in conjunction with the interrupt system. In this case, an interrupt will occur after
the specified number of ticks.

Assign Device (ASD)

Octal Code: 6440

Operation: If the device specified by the contents of the AC is available, it will be assigned
to the user program and the AC cleared. Otherwise, the number of the user program having
the devi ce is placed in the AC. If the devi ce does not exist, 7777 is returned in the AC.
The left half of the AC specifies the device type and the right half specifies the
unit number.

4-6

AC Bits 0-5

AC Bits 6-11

0
40
40
40
40
40
40

K
0
1
2
3
4
N+5

Device
Console K
Paper tape reader
Paper tape punch
line printer
Plotter
Card Reader
DECtape unit N

This assignment is in effect until a corresponding REL instruction or LOGOUT is encountered.

Release Device (REL)

Octal Code: 6442

Operation: The device specified by the contents of the AC is released. If the device was
not assigned by ASD, the release is a NOP. Otherwise, the device is made available to
other users. The AC is cleared.

Octal Code: 6402

Slave A Console (SLV)

Operation: SLY enables a user program to slave a console belonging to the user. When a
console is slaved, the call (CTRL/B) character is treated as an ordinary character rather than
as the System Interpreter call character. Thi s means that the slaved conso Ie may not call the
System Interpreter.
Load the AC with the number of the console to be slaved, then execute SLV. If
the console specified does not belong to the user, this lOT will be considered illegal and the
AC will be non-zero. Otherwise, the AC is cleared.

Octal Code: 6403

Unslave A Console (UNS)

Operation: UNS removes a slaved console from the slave state. The call character resumes
its power to call the System Interpreter.
Load the AC with the number of the console to be released from the slave state,
then execute UNS. If the console specified is not a slave or does not belong to the user,
this lOT wi II be considered a NOP. The AC is cleared.

Set Switchboard and Permission Tables (SSP)

Octal Code: 6404

Operation: SSP is used to set, reset, and read bits in the Switchboard and Permission Tables.
Its use mirrors the format of the Monitor commands for the same purpose.
Load the AC with the beginning address of a 3-word block:

4-7

Word 1:

Bits 0 and 1 contain 0, 1, 2, or 3

o
1

reset the bit in the table
read the bit in the table - the value of the bit is
returned in the AC after executing SSP

2
3

set the bit in the table
I ink - set both tables

Bit 9 contains 0 or 1

o
1

reference the Switchboard Table
reference the Permission Table

Bit 10 contains 0 or 1

o
1

reference the keyboard rows of the table
reference the programs typing out rows of the table

Bit 11 contains 0 or 1

o
1

reference the input columns of the table
reference the output columns of the table

Word 2:

contains the number of the keyboard or program typing out
to be referenced

Word 3:

contains the number of the input or output buffer to be
referenced

I f SSP is executed, the AC is set to 0, otherwise, to 7777. As an example of the
use of SSP to duplicate the effect of the Monitor command SET P K 1307; (set the Permission
Table to give permission for the keyboard of console 13 to type into the output buffer of console 7) execute the following sequence:
TAD ARRAY
SSP
ARRAY, .+1

4005
13

7
As an example of console linking, the Monitor command LINK 3; (set the Permission Table
to give permission for the keyboard of console 3 to type into the output buffer of this job
and set the Switchboard Table to route keyboard input to this job to the output buffer of
console 3) is equivalent to:

4-8

USE
CON
DCA TABLE+2
TAD TABLE
SSP
TABLE,

.+1
6000

Set Switch Register (SSW)

o cta I Code: 6430

Operation: Each user program has a switch register corresponding to the PDP-8/1 switch
register. This lOT stores the contents of the AC in the user's switch register, and the AC
is cleared.

OR With Switch Register (OSR)

Octal Code: 7404

Operation: The contents of the user's switch register are inclusively ORed into the AC.
OSR may be micro-coded with other group 2 lOT's (see Small Computer Handbook, C-800).

4.2

FILE CONTROL
All bulk data storage for user programs is on file on the disk. This area is referred to col-

lectively as file storage. A user program may read or write a file to handle bulk input/output of text
or binary information.
Files are composed of sequential segments of file storage. The size of a file segment is an
integer multiple of disk records specified at system initialization time. A record consists of 128 12-bit
machine words. Files are at least one segment long and grow by adding additional segments to the end
of the file. Each file is registered in the owner's file directory by a name which may be any string of
not more than six 6-bit characters.
Each user may refer to four files simultaneously. An internal file number (0, 1, 2, or 3) is
associated with each of the user program's active files. All references to file storage is by internal file
numbers. The act of associating an internal file number with a file referenced by an account number
and name is called "opening" the file.
All file lOTs that are successfully completed return to the user with the AC cleared. A nonzero AC indicates that an error was detected and the lOT was not performed. The error messages are
as follows:

4-9

AC = 4000
AC = 4400
AC = 5000
AC = 6000
AC = 7000
AC = 7400

The internal file specified is not open
The fi Ie is open to another user
The directory is full
Fi Ie protection violation
Fi Ie not found
Disk is full

Read File (RALE) and Write File (WFILE)

Octal Codes: 6603 and 6605

Operation: Once the association of a file with an internal file number has been made, these
lOTs allow the actual file reference to be made. They are illegal on a file that has not been
opened (associated with an internal file number).
To read or write a fi Ie, load the AC with the address of a 6-word block, then
execute the lOT. The format for the 6-word block is:
Word 1:

contains the high-order fi Ie word address

Word 2:

contains the internal file number

Word 3:

contains the negative of the number of words for the operation.
This number will be either the number of words to be read or
the number of words to be written.

Word 4:

contains a pointer to the beginning address -1 of a buffer located in the user program. On a read operation this buffer
will receive the information from the file; on a write operation this buffer holds the information that is to be sent to the
file.

Word 5:

contains the least significant 12 bits of the initial file word
address to begin the operation.

Word 6:

contains an error code:

o
1
2
3

if no error
if parity error
if file shorter than word count
if file not open
if protection violated

The read or write begins at the word specified by words 1 and 5. For example:
TAD X
WFILE

.+1

o
1
-200
6477
200
means, write 200 words starting at word 200 of the file that is associated with internal
file number 1 from a buffer starting at location 6500.

4-10

After the lOT is given, the file request is placed in the file request queue, and the
corresponding file-inactive bit is cleared in status register 1 for the user program. Execution
of the user program continues immediately without waiting for the file request to be completed. If the Wait Mask contains a 1 in the bit corresponding to the inactive bit for that
file, however, the user program wi II be dismissed unti I the fi Ie request has been completed.
The file queue is one deep for each of the user program's internal file numbers,
therefore, four different file requests may be overlapped if they refer to the four different
internal file numbers. An attempt to overlap a file request on the safTIe internal file number
will result in the user program being dismissed until the first request on that internal file
number has been completed. After completion of any file request, the corresponding file
inactive bit in status register 1 is set to 1 and the word count (word 3) and core address
(word 4) are updated, and the error code is set in word 6.

o cta I Code: 6600

Rename A File (REN)

Operation: REN is used to change the name of a file. Load the AC with the beginning
address of a 4-word block, where
Word 1:

contains the internal file number associated with the file
whose name is to be changed, that is, to rename a file one
must first open it, otherwise, REN is i II ega I.

Words 2 through 4:

contain the new name. This name is in 6-bit characters
packed two to a word.

Open A Fi Ie (OPEN)

o cta I Code: 6601

Operation: OPEN is used to associate a file with an internal file number. This process,
called "opening", is necessary since all file operations are in terms of the internal file
numbers. Before executing the OPEN lOT, load the AC with the beginning address of a
5-word block, where
Word 1:

contains the internal file number.

Word 2:

contains the account number of the owner of the file. If 0,
the account number of the current user is specified.

Word 3 through 5:

contain the name of the file to be opened. This name is in
6-bit characters packed two to a word.

If there was another file associated with the internal file number before the execution of

the OPEN lOT, it will be closed automatically before the new file is associated with the
internal file number.

4-11

Close A File (CLOS)

Octal Code: 6602

Operation: CLOS tenninates tl-e association between files and their internal file numbers.
Before executing CLOS, load the AC with a selection pattern for the internal file numbers
whose associated files are to be closed. The file is closed if bit I is 1, where I = bit 0, 1,

2, or 3.

Protect A File (PROT)

Octal Code: 6604

Operation: The owner of a file may protect his file from unauthorized attempts to access it
by using this instruction. Before executing PROT, load the AC with
Bits 5 through 6

Internal fi Ie number of the reserved file to be protected.

Bit 7

Write protect against owner.

Bit 8

Write protect against users whose project nUlTlber is same as
owner's.

Bit 9

Read protect against users whose project number is salTle as
owner's.

Bit 10

Write protect against users whose project number differs from
owner's.

Bit 11

Read protect against users whose project number differs from
owner's.

A file must be opened before it can be protected. PROT is legal only when performed by the
fi Ie owner, that is, the user who created the fi Ie. All attempts to access the fit e which
violate any of the protection flags will be considered illegal.

File Information (ANF)

Octal Code: 6613

Operation: FINF enables a user program to determine what file, if any, is associated with
an internal fi Ie number. Load the AC with the beginning address of a 7-word block, where
Word 1:

contains the internal file number for which the user program
wishes information.

Words 2 through 7 wi II contain the information that the system returns after executing FI NF.
Word 2:

contains the account number of the owner or zero if no file
is associated with the internal file number, that is, the file
is not open.

Words 3 through 5:

contain the name of the file in 6-bit code.

4-12

Word 6:

contains
Bit=l

Word 7:

Means

write protected against owner

write protected against users whose project number
is same as owner's

read protected against users whose project number
is same as owner's

write protected against users whose project number
differs from owner's

read protected agai nst users whose project number
differs from owner's

contains the number of segments that the file contains.

Create A Fi Ie (CRF)

Octal Code: 6610

Operation: The user may request the system to create a new file of one segment. The user
program provides the new name for the file. Load the AC with the beginning address of a
3-word block, where
Words 1 through 3:

contain the 6-character name.

If there is some reason why the request cannot be granted, the system will return a non-zero

error code in the AC. The protection of a newly created file is 17.

Extend A Fi Ie (EXT)

Octal Code: 6611

Operation: To extend the length of an existing file, that file must be currently open. Load
the AC with the beginning address of a 2-word block, where
Word 1:

contains the internal file number of the file to be extended.

Word 2:

contains the number of segments the system should append to
the fi Ie.

If for some reason the request to extend a file cannot be granted, the AC wi II contain 4000,

4400, 6000, or the number of segments it failed to append.

Reduce A File (RED)

Octal Code: 6612

Operation: To reduce the length of an existing file, that file must be currently open. Load
the AC with the beginning address of a 2-word block, where
Word 1:

contains the internal fi Ie number of the fi Ie to be reduced.

Word 2:

contains the number of segments to be removed.

This request will always be granted.

4-13

Segment Size (SIZE)

Octal Code: 6614

Operation: The number of words per segment is returned in the AC.

Account (ACT)

Octal Code: 6617

Operation: The account number of the job whose number is in the AC is returned in the AC.
If the AC is 0, the current job is assumed. If 0 is returned in the AC, the specified job does

not exist.

Who (WHO)

Octal Code: 6616

Operation: The account number and password of the current job are returned to the threeword block whose address is in the AC, and the AC is cleared.

4.3

INPUT BUFFER CONTROL
Set Keyboard Break (KSB)

o cta I Code: 6400

Operation: Rather than activate the user program to receive each character as it is placed
in the input buffer, TSS/8 saves time by activating the program only on certain conditions
specified by the user. These activation conditions are called delimiters. Before executing
KSB, load the AC with a 12-bit delimiter table. The format of the table is as follows:
(where each bit = 1)

4-14

When a bit in the table is set to 1, the user's program is activated if the condition the bit
represents is met by the incoming character, or if the input buffer becomes full. The del imiter
table is initialized to 3777 on LOGIN and ASSIGN. KSB clears the AC.

Set Buffer Control Flags (SBC)

Octal Code: 6401

Operation: SBC permits the user program to clear his input and output buffers and control
the recording of character time and source in his input buffer. Before executing SBC, load
the AC with the desired flags whose functions are
Bit

o
1
2

Clear output buffer
Clear input buffer
Record character source
Record character time

If bit 2=1, the source of each character in the input buffer is recorded in the following
character position. The source from which the character was generated is indicated by the
8-bit character as follows:

OXX
1XX
172
174
177

Console XX keyboard
User program XX typi ng out
637 typing out
PDP-l0 typing out
System Interpreter typing out

Bit 2 of status register 0 is set to 1. If AC bit 2=0, source recording in the input buffer is
suppressed and bit 2 of status register 0 is set to O.
If AC bit 3= 1, the time of receipt of each input character is recorded in the two
successive character positions following the character or following the source. If the time
is being recorded, bit 3 of status register 0 is set to 1.
If AC bit 3=0, time recording in the input buffer is suppressed and bit 3 of status
register 0 is set to O. The AC is cleared by SBC.

Skip On Keyboard Flag (KSF)

Octal Code: 6031

Operation: The keyboard flag is sensed, and if it contains a binary 1, the contents of the
PC is incremented by one so that the next sequential instruction is skipped. The keyboard
flag is bit 6 of status register 1, and it has a value of 1 whenever the input buffer is not
empty. If the keyboard flag is 0 and the keyboard wait flag (bit 6 of wait register 1) is 1,
the job is placed in the active state until the keyboard flag is 1. If the keyboard wait flag
is 0, control returns to the calling program immediately.
4-15

o cta I Code: 6032

Clear Keyboard Flag (KCC)
Event Ti me: 2

Operation: The AC is cleared, and if the input buffer is empty, the keyboard flag is cleared.

Read Keyboard Buffer Static (KRS)

o cta I Code: 6034

Event Time: 3
Operation: If the input buffer is not empty, the next character from the input buffer is
inclusively ORed into bits 4 through 11 of the AC. This is a static command in that neither
the AC nor the keyboard flag is cleared. If fhe input buffer is empty and the keyboard wait
flag is 0, no operation is performed and control returns immediately to the user's program.
If the keyboard wait flag is 1, the job is placed in the active state until the keyboard flag

is 1.

Read Keyboard Buffer Dynamic (KRB)

Octal Code: 6036

Event Time: 2, 3
Operation: Identical to KCC followed by KRS.

Read Keyboard String (K SR)

Octal Code: 6030

Operation: Before executing KSR, load the AC with the address of a 2-word block, where
Word 1:

contains the negative of the number of characters to read.

Word 2:

contains the address -1 of the first word of the buffer.

If the keyboard wait flag is 1, control does not return to the user program unti I a break

condition (see KSB) is satisfied or unti I the word count in word 1 is reduced to zero. If the
keyboard wait flag is 0, control returns to the user program immediately; control returns to
the location following the KSR, the negative of the number of characters remaining to be
transferred is in word 1, and word 2 points to the last character stored. The AC is cleared.

4.4

OUTPUT BUFFER CONTROL
Send A String (SAS)

Octal Code: 6040

Operation: To send a string, load the AC with the address of a 2-word block, where

4-16

Word 1:

contains the negative of the number of characters to be sent.

Word 2:

contains the address -1 of the first word of the string.

The characters are stored one per word right justified starting at the address specified by
word 2. Upon execution of SAS, the system takes only as many characters as will fit in the
output buffer. It then makes the appropriate adjustment to word 2 to indicate a new starting
address and to word 1 to indi cate the reduced character count; it returns to the instruction
following the SASe If the character count is reduced to zero, the instruction following the
SAS is skipped. The instruction following the SAS may contain a JMP .-1 to continue the
block transfer of Teletype characters. In this case, the user program will dismiss until the
Teletype output buffer is nearly empty. If the user wishes to avoid dismissal, he can place
a jump to another part of his program in the instruction following SAS. The AC is cleared
by SASe

Skip on Teleprinter Flag (TSF)

Octal Code: 6041

Event Time: 1
Operation: The teleprinter flag is sensed, and if it contains a binary 1, the contents of the
PC is incremented by one so that the next sequential instruction is skipped. The teleprinter
flag is bit 7 of status register 1, and has a value of 1 if the output buffer is not full. If the
teleprinter wait flag is 0, control returns to the user program immediately, otherwise, control returns when the teleprinter flag is 1.

Clear Teleprinter Flag (TCF)

o cta I Code: 6042

Event Time: 2
Operation: The teleprinter flag is cleared to zero.

Load Teleprinter And Print (TPC)

Octal Code: 6044

Event Time: 3
Operation: The character in bits 4 through 11 of the AC is typed out and routed through
the switchboard to all buffers connected to the user's program character output.

4-17

Load Teleprinter Sequence (TLS)

Octa I Code: 6046

Event Time: 2, 3
Operation: Same as TPC.
4.5

HIGH-SPEED PAPER TAPE READER
Skip On Reader Flag (RSF)

Octal Code: 6011

Event Time: 1
Operation: The reader flag is sensed, and if it contains a binary 1, the contents of the PC
is incremented by one so that the next sequential instruction is skipped. The reader flag is
bit 8 of status register 1, and has a value of 1 if the reader buffer is not empty. If the reader
wait flag in the wait mask is 1, the program is dismissed until the reader flag is 1, otherwise,
control returns to the user program immediately.
Read Reader Buffer (RRB)

Octal Code: 6012 or 6016

Event Ti me: 2
Operation: The contents of the reader buffer is transferred into bits 4 through 11 of the AC
and the reader flag is cleared if the reader buffer is empty. This instruction does not clear
the AC. If the reader buffer is empty and the reader wait flag is 1, the user program is dismissed unti I the reader flag is 1. If the reader buffer is empty and the reader wait flag is 0,
this lOT is a NOP.
Reader Fetch Character (RFC)

Octal Code: 6014

Event Ti me: 3
Operation: The reader flag and the Monitor reader buffer are both cleared, the reader is
started to fi" the Monitor reader buffer and the reader flag is set after the first character is
read.

Read Reader String (RRS)

Octal Code: 6010

Operation: RRS allows a user program to read a string of characters from the paper tape
reader. Before executing RRS, load the AC with the beginning address of a 2-word block,
where
Word 1:

contains the negative of the number of characters to read.

Word 2:

contains the address -1 of the first word of a buffer.

4-18

If the reader wait flag in the wait mask is 1, the program is dismissed unti I the transfer is

completed, otherwise, control returns to the user program immediately. The reader flag is
set to 1 when the transfer is complete. The AC is cleared by RRS.

4.6

HIGH-SPEED PAPER TAPE PUNCH
Skip On Punch Flag (PSF)

Octal Code: 6021

Event Ti me: 1
Operation: The punch flag is sensed, and if it contains a binary 1, the contents of the PC
is incremented by one so that the next sequential instruction is skipped. The punch flag is
bit 9 of status register 1, and has a value of 1 if the punch buffer is not full. If the punch
flag is 1 and the punch wait flag is 1, the program is dismissed until the punch flag is 1.
If the punch flag is 0 and the punch wait flag is 0, no operation is performed and control

returns to the user program immediately.

Clear Punch Flag (PCF)

Octal Code: 6022

Event Ti me: 2
Operation: If the punch buffer is not full, the punch flag is cleared in preparation for
punching the next character from the computer. If the punch buffer is full and the punch
wait flag is 1, the program is dismissed until the punch flag is 1. If the punch buffer is full
and the punch wait flag is 0, no operation is performed and control returns to the user program immediately.

Load Punch Buffer and Punch Character (PPe)

Octal Code: 6024

Event Ti me: 3
Operation: An a-bit character is transferred from bits 4 through 11 of the AC into the punch
buffer and then this character is punched. PPC does not clear the punch flag. If the punch
buffer is full and the punch wait flag is 1, the program is dismissed until the punch flag is
1. If the punch buffer is full and the punch wait flag is 0, no operation is performed and
control returns to the user program immediately.

4-19

Load Punch Buffer Sequence (PLS)

o cta I Code: 6026

Event Time: 2, 3
Operation: Identical to PCF followed by PPC.

o cta I Code: 6020

Punch String (PST)

Operation: PST allows a user program to punch a string of characters. Before executing PST,
load the AC with the beginning address of a 2-word block, where
Word 1:

contains the negative of the number of characters to be punched.

Word 2:

contains the beginning address -1 of the string to be punched;
the characters should be right justified one per word.

Upon execution of PST, the system takes only as many characters as will fit in the punch
buffer; it then makes the appropriate adjustment to word 2 to indicate a new starting address
and to word 1 to indicate the reduced character count. It returns to the instruction following the PST. If the character count is reduced to zero, the instruction following PST is
skipped. The AC is cleared by PST.

4.7

DECTAPE
Load Status Register A (DTXA)

Octal Code: 6764

Operation: DTXA allows a user program to read and write records (12B-word blocks) on
DECtape. Load the AC with the beginning address of a 4-word block, where
Word 1:

contains
Bit=l
0-2
6-B = 2
4
9 =0

10-11

contain the transport unit select number
for read data function
for write data function
to disable DECtape control flag (DTCF) and error
flag from causing a progralTl interrupt.
to enable DECtape control flag (DTCF) and error
flag to cause program interrupt
unused

Word 2:

contains the beginning DECtape block number

Word 3:

contains the negative of the number of records to transfer

Word 4:

contains the beginning core address -1 of record buffer

After DTXA is given, the DECtape request is placed in the DECtape request queue and the
DECtape and error flags are cleared in status register 2. Execution of the user program continues immediately without waiting for the DECtape request to be completed. If the wait

4-20

mask contains a 1 bit corresponding to the DECtape flag of the selected unit, the program
will be dismissed until the DECtape request has been completed. The DECtape queue is one
deep for each unit, therefore, four different DECtape requests may be overlapped if they
refer to different units. An attempt to overlap a DECtape request on the same unit will
result in the user program being dismissed until the first request has been completed. After
the completion of any DECtape request, the corresponding DECtape flag in status register 2
is turned on. The AC is cleared by DTXA.

Skip On Flags (DTSF)

Octal Code: 6771

Event Time: 1
Operation: The contents of both the error flag and the DECtape flag is sampled, and if
either flag contains a binary 1, the contents of the PC is incremented by one to skip the
next sequential instruction. If both flags are zero and if either of the corresponding wait
flags are 1, the user program is dismissed until the skip condition is satisfied.

Read Status Register B (DTRB)

Octal Code: 6772

Event Time: 2
Operation: The contents of DECtape status register B is loaded into the AC by an OR transfer. The AC bit assignments are:
0
1
2

=
=
=

3
4

5
6

4.8

error flag
mark track error
end of tape
select error
parity error
timing error

through
10

unused

DECtape flag

AUTOMATIC LINE PRINTER
The Automatic line Printer and Control (Type 645) lOT instructions are simulated precisely as

they appear in the Small Computer Handbook. The line printer error flag is bit 10 of status register 2,
and the done flag is bit 11 of the same register. The wait mask and priority interrupt mask have the
same significance as with other devices.

4-21

Skip On Line Printer Error (LSE)

Octal Code: 6651

Event Time: 1
Operation: The contents of line printer error flag is sensed, and if it contains a binary 1,
indicating that an error has been detected, the contents of the PC is incremented by one so
that the next sequential instruction is skipped.
Symbol:

If Line Printer Error Flag = 1, then PC+1 .... PC

Clear Printer Buffer (LCB)

Octal Code: 6652

Event Ti me: 2
Operation: Both sections of the line printer buffer are cleared in preparation for receiving
new character information.
Symbol:

0"" LPB

Load Printer Buffer (LLB)

Octal Code: 6654

Event Ti me: 3
Operation: A section of the printer buffer is loaded from the contents of bits 6 through 11 of
the AC, then the AC is cleared.
Symbol:

AC 6 through 11 .... LPB, then 0 .... AC

Skip On Line Printer Done Flag (LSD)

Octal Code: 6661

Event Time: 1
Operation: The contents of the line printer done flag is sensed, and if it contains a binary
1, the contents of the PC is incremented by one so that the next sequential instruction is
skipped.
Symbol:

If Line Printer Done Flag = 1, then PC + 1 .... PC

Clear Line Printer Flags (LCF)

Octal Code: 6662

Event Time: 2
Operation: The line printer done and error flags are cleared.
Symbol:

0 .... Line Printer Done Flag

o .... Line Printer Error Flag

4-22

Clear Fonnat Register (LPR)

Octal Code: 6664

Event Time: 3
Operation: The line printer fonnat register (FR) is cleared and then loaded from the contents
of bits 9 through 11 of the AC, and the AC is cleared. The line contained in the section of
the printer buffer (LPB) loaded last is printed. Paper is advanced in accordance with the
selected channel of the format tape if the contents of AC8 is a 1. If AC8 is a 0, paper
advance is inhibited.

4.9

INCREMENTAL PLOTTER
The Incremental Plotter and Control (Type 350B) lOT instructions are simulated precisely as

they appear in the Small Computer Handbook. The plotter flag is bit 0 of status register 2. The wait
mask and priority interrupt mask have the same significance as with other devices.

Skip On Plotter Flag (PLSF)

Octal Code: 6501

Event Ti me: 1
Operation: The plotter flag is sensed, and if it contains a 1 the contents of the PC is
incremented by one so that the next sequential instruction is skipped.
Symbol:

If Plotter Flag = 1, then PC + 1 - PC

Clear Plotter Flag (PLCF)

o cta I Code: 6502

Event Time: 2
Operation: The plotter flag is cleared in preparation for issuing a plotter operation command.
Symbol:

Pen Up (PLPU)

0 - Plotter Flag

Octal Code: 6504

Event Ti me: 3
Operation: The plotter pen is raised from the surface of the paper.

Pen Right (PLPR)

Octal Code: 6511

Event Ti me: 1
Operation: The plotter pen is moved to the right in either the raised or lowered position.

4-23

Drum Up (PLDU)

Octal Code: 6512

Event Time: 2
Operation: The plotter paper drum is moved upward. This instruction can be combined with
the PLPR and PLDD instructions.

Drum Down (PLDD)

Octal Code: 6514

Event Time: 3
Operation: The plotter paper drum is moved downward.

Pen Left (PLPL)

Octal Code: 6521

Event Time: 1
Operation: The plotter pen is moved to the left in either the raised or lowered position.

Drum Up (PLUD)

Octal Code: 6522

Event Ti me: 2
Operation: The plotter paper drum is moved upward. This instruction is similar to PLDU
except that it can be combined with PLPL or PLPD instructions.

Pen Down (PLPD)

Octal Code: 6524

Event Time: 3
Operation: The plotter pen is lowered to the surface of the paper.

4.10

CARD READER
Skip on Card Reader Flag (CRSF)

Octal Code: 6632

Event Ti me: 2
Operation: The contents of the card reader flag is sensed, and if it contains a 1 (indicating
that the card column is present for reading), the contents of the PC is incremented by one so
that the next sequential instruction is skipped. The card reader flag is bit 6 of status register
2 and it has the value 1 if a card is in the card buffer. If the card reader flag is 0 and the
card reader wait flag is 1, the program is dismissed until the card reader flag is 1; otherwise,
control returns to the user program immediately.

4-24

Read Card Equipment Status (CERS)

Octal Code: 6634

Event Time: 3
Operation: The contents of the card reader flag and statlJS flags are transferred into the
contents of bits 7 through 9 of the AC. The AC bit assignments are:
7

card reader flag (1 if card in TS8 card reader buffer)

not ready (covers not in place, power is off, start pushbutton has not been
pressed, hopper is empty, stacker is full, a card is jammed, a validity check
error has been detected, or the read circuit is defective)

end of fj Ie (EOF) (hopper is empty and ope rator has pushed EOF button)

Read Card Reader Buffer (CRRB)

Octal Code: 6671

Event Time: 1
Operation: The contents of the card column buffer is transferred into the AC and the card
reader flag is cleared if the card reader buffer is empty. One CRRB reads either alphanumeric
or binary information. If the card reader buffer is empty and the card reader wait flag is
1, the program is dismissed until the card reader flag is 1. If the card reader buffer is empty
and the card reader wait flag is 0, no operation is performed and control returns to the user
program immediately.

Select Alphanumeri c (CRSA)

Octal Code: 6672

Event Time: 2
Operation: The card reader alphanumeric mode is selected and a card is read into the card
reader buffer. Information read into the card reader buffer is in 6-bit alphanumeric form
(the Hollerith code representing the decoded 12-row character in one column). If the card
reader wait flag is 1, the user program is dismissed until the card reader flag is 1; otherwise,
control returns to the user program immediately.

Select Binary (CRSB)

Octal Code: 6674

Event Time: 3
Operation: The card reader binary mode is selected and a card is read into the card reader
buffer in 12-bit binary form. If the card reader wait flag is 1, the user program is dismissed
until the card reader flag is 1; otherwise, control returns to the user program immediately.

4-25

Upon instruction to read the card reader buffer, the contents of the 12-bit column
is transferred into the AC. In the alphanumeric mode a 6-bit Hollerith code is transferred
into bits 6 through 11 of the AC, and bits 0 through 5 of the AC are cleared. In the binary
mode, the binary contents of the 12 bits (or rows) in a card column are transferred into the
AC so that row X is read into AC bit 0, row Y into AC bit 1, row 0 into AC bit 2, ••• , and
row 9 into AC bit 11. The mode is specified by either the CRSA or CRSB instruction.

Read Card String (RCS)

Octal Code: 6630

Operation: RCS allows the user program to read a string of characters from the card reader.
Before executing RCS, load the AC with the beginning address of a 2-word block, where
Word 1:

contains the negative of the number of columns to be read.

Word 2:

contains the address -1 of the first word of a buffer.

If the transfer is terminated before the column count has been reduced to zero, the card
reader flag is turned on the words 2 and 1 contain the address -1 of the next buffer location
and the negative of the number of columns remaining to be read, respectively. Columns are
packed right justified, one per word independent of mode.

4-26

CHAPTER 5
ERROR DIAGNOSTICS

5.1

USER PROGRAM
The following error messages are typed on the user's printer by the Error Phantom when error

conditions occur in a running user program. If the user program is not ercbled for system error interrupts,
the error messages are typed in the following format.
Sl FOR USER C1
AC=C2, l=C3, PC=C4
I NSTR=C5
Sl is a string, describing the nature of the illegal instruction C5 which user program C1 has executed at
location C4. At the time the illegal instruction was executed the value of the accumulator was C2 and
the value of the link was C3. For example,
ILLEGAL lOT

The user program has executed an lOT which the system regards
as illegal. The illegality may be for one of two reasons:

1. The lOT itself may be illegal.
2. The parameters to a legal lOT may invalidate it.

5.2

SYSTEM INTERPRETER
The following error messages result from illegal requests to the System Interpreter. They are

printed by the System Interpreter on the printer.
Sl

The System Interpreter does not understand the command.
Sl = command

I LLEGAL REQUEST

The user has requested an illegal service. This error usually
results when some parameter has been given an incorrect value
or the req uest refers to a faci Ii ty not owned by the user.

SWITCHBOARD ERROR

The user has attempted to set a Permission Table bit not owned
by him; or the user has attempted to make a connection in the
Switchboard Table for which permission has not been granted.

SAVE LIMIT ERROR

The user has given invalid bounds in the command to save binary
core image. The first bound must be lower than the second.

CONSOLE IN USE
LOGOUT TO
RELEASE

The user has tried to log in on a console which is already ;n
use; or he has attempted to add a console to those he already
owns.

The user has attempted to use a console which is not logged in.

5-1

UNAUTHORIZED
ACCOUNT

The user has attempted to log into the system with an invalid
account number or name.

FULL

This message may appear on an attempt to log into TSS/8 from
a console. It means that all disk swapping tracks are in use.

C1 HAS Sl

Job C1 had device Sl; the request for its acquisition cannot be
granted.
C1 = job number
S 1 = devi ce name

5-2

APPENDIX A
TSS/8 CHARACTER SET

TSS/8 accepts 8-bit ASCII character only. ASCII is an abbreviation for USA Code for
I nformati on Interchange. The acceptable characters and their 6- and 8-bit octal equivalence are
listed below.
6-Bit*
Octal

8-Bit
Octal

Character

00
01
02
03
04
05
06
07

240
241
242
243
244
245
246
247

@
A
B
C
D
E
F
G

H
I

12
13
14
15
16
17

250
251
252
253
254
255
256
257

0
1
2
3
4
5
6
7

20
21
22
23
24
25
26
27

260
261
262
263
264
265
266
267

8
9

30
31
32
33
34
35
36
37

270
271
272
273
274
275
276
277

Character
Space

$
0/0
&

(
)
*
+

>
?

300
301
302
303
304
305
306
307

41
42
43
44
45
46
47

L
M
N

54
55
56
57

60
61
62
63
64
65
66
67

320
321
322
323
324
325
326
327

70
71
72
73
74
75
76
77

330
331
332
333
334
335
336
337

a
Q

R
S
T
U
V
W
X
Y
Z
[

]

A-1

8-Bit
Octal

310
311
312
313
314
315
316
317

J
K

* Used to store passwords and filenames only

6-Bit*
Octal

50
51
52
53

APPENDIX B
SUMMARY OF COMMANDS

A Monitor command is a string of characters terminated by a semicolon (;) or a carriage return (RETURN key). Parameters to commands may be octal numbers, decimal numbers, character strings,
or single letters. In the following summary, parameters are coded as follows:
Cl, C2,

represent octal numbers

Dl, D2,

represent decimal numbers

Sl, S2,

represent character stri ngs

Ll, L2,

represent single letters

Logging In and Out
LOGIN Cl Sl;

Request to login;
C 1 = user1s account number
S1 = user's password

LOGOUT;

Request to logout; processing and console time is typed out

TIME Cl;

Request typeout of processing time;
C 1 = job number
Without C 1, current job is assumed;
Before logging in and without Cl, time-of-day is typed out;
If Cl=job 0, time-of-day is typed out.

Console Manipulation
ASSIGN K Cl;

Request console;
K = console
C 1 = console number

SLAVEC1;

Slave an owner console;
C 1 = console number

UNSLAVE Cl;

Unslave an owned console;
Cl = console number

RELEASE K Cl;

Release console;
K = console
Cl = console number

Device Allocation
ASSIGN Ll;

Access device;
L1 = R for paper tape reader
P for paper tape punch
C for card reader
L for line printer
I for incremental plotter

B-1

Devi ce Allocation (Cont)
ASSIGN D Cli

Access DECtape unit;
D = DECtape
Cl = device number

RELEASE L1;
RELEASE K Cl;
RELEASE D Cl;

Release device;
L1 = R, P, C, L, or I, (see ASSIGN L1;)
K = console
D = DECtape unit
Cl = console or DECtape number

OPEN Cl Sl C2;

Establ ish association between internal fi Ie number and fi Ie;
C 1 = internal fi Ie number
Sl = file narne
C2 = account number

CLOSE Sl;

Close files;
S 1 = Iist of internal fi Ie numbers

CREATE Sl;

Create new fi Ie;
Sl = name of new file

RENAME Cl Sl;

Rename a fi Ie;
Cl = internal file number
S 1 = new name of file

REDUCE Cl Dl;

Reduce length of file;
Cl = internal file number
D 1 = number of segments to be removed from end of fi Ie

EXTEND Cl Dl;

Extend length of file;
Cl = internal file number
D 1 = number of segments to be added to end of fi Ie

PROTECT Cl C2;

Protect a file;
Cl = internal file number
C2 = new fi Ie protection mask
1 read protect against users with different project
number
2 write protect against users with different project
number
4 read protect against users with same project
number
10 write protect agai nst users wi th same proj ect
number
Or the sum of any combination

F Cl;

Print out association between internal file numbers and files
C 1 = internal fi Ie number

Control Of User Programs
START Cli

Execute user program;
Cl = starting location

B-2

Control of User Programs (Cont)
START;

Restart user program;

DEPOSIT Cl C2 ••• Cn; Store in core memory;
Cl = location
C2 = contents to be stored
Cn = location Cl+n-l
n ~ 10 decimal
EXAMINE Cl Dl;

List specified contents;
Cl = first location
Dl = number of location to be listed
Dl ~ 10 decimal

Saving and Restoring Binary User Programs
SAVE Sl;
SAVE Sl Cl;
SAVE Sl Cl C2;
SAVE Sl Cl C2 C3;

Save core image;
Sl = name of file
Cl = fi Ie address of first word to be
saved; if not specified, entire 4K is saved
C2 = core address of first word to be saved; if not specified,
entire core is saved
C3 = core address of last word to be saved; if not speci fied,
entire core is saved

LOAD Cl Sl;
Load core image;
LOAD Cl Sl C2;
Cl = owner's account number
LOAD Cl Sl C2 C3;
Sl = name of file
LOAD Cl Sl C2 C3 C4;
C2 = file address of first word to be loaded; if not specified,
entire 4K is loaded
C3 = core address of first word to be loaded, if not
specified, entire core is loaded
C4 = core address of last word to be loaded; if not
specified, entire core is loaded

R Sl;

Run System fi Ie;
S 1 = name of fi Ie

RUN Sl;

Run user fi Ie;
Sl = name of file

RUN Cl Sl;

Run user fi Ie;
C 1 = owner's account number
Sl = name of file

S·,

Stop execution

WHERE;

Type out contents of location counter, accumulator, link,
and switch register

USER;

Type out number of the job and devices owned

USER Cl;

Type out devi ce numbers;
C 1 = user's account number

B-3

Saving and Restoring Binary User Programs (Cont)
SWITCH Cl;

Set switch register;
Cl = word to be set

Switchboard
SET Ll L2 Cl L3 C2;

Set bit in Permission or Switchboard Table;
Ll = P for Permission Table
S for Switchboard Table
L2 = K for keyboard
P for user program
C 1 = keyboard or program number
L3 = I for input buffer
o for output buffer
C2 = receiving buffer number

RESET Ll L2 Cl L3 C2;

Clear bit in Permission or Switchboard Table;
parameters are as in SET, above

READ L1 L2 Cl L3 C2;

Read bit in Permission or Switchboard Table;
parameters are as in SET, above

DUPLEX;

Echo typed characters on printer;

ALLOW Cl;

Permit console Cl to output on this console;
Cl = console number

LINK Cl;

Output to console Cl;
Cl = console number

B-4

APPENDIX C
SUMMARY OF lOT INSTRUCTIONS
PROGRAM CONTROL

6000
6001
6002
6003
6005
6006
6007

SIM
ION
10F
RIM
SWM
CWM
RWM

Set Interrupt Mask
Interrupt Tum On
Interrupt Tum Off
Read Interrupt Mask
Set Wait Mask
Clear Wait Mask
Read Wait Mask

6200

CKS

Check Status

6402
6403
6410
6411
6412
6413
6414
6415
6416
6420
6421
6422
6430
6440
6442

SLY
UNS
SSP
WAIT
URT
TOO
RCR
DATE
SYN
STM
TSS
USE
CON
SSW
ASD
REL

Slave A Console
Unslave A Console
Set Switchboard and Permission Tables
Wait
User Run Ti me
Time Of Day
Return Clock Rate
Date
Quantum Synchronization
Set Timer
Skip On TS8
User
Console
Set Switch Register
Ass ign Devi ce
Release Device

7402
7404

HLT
OSR

Halt
OR With Switch Register

REN
OPEN
CLOS
RALE
PROT
WFILE
CRF
EXT
RED
FINF
SIZE
ACT
WHO

Rename File
Open File
Close File
Read File
Protect Fi Ie
Write File
Create File
Extend File
Reduce File
File Information
Segment Size
Account Number
Who

6404

FILE CONTROL

6600
6601
6602
6603
6604
6605
6610
6611
6612
6613
6614
6617
6616

C-1

INPUT BUFFER CONTROL
6030
6031
6032
6034
6036

KSR
KSF
KCC
KRS
KRB

Read Keyboard String
Skip On Keyboard Flag
Clear Keyboard Flag
Read Keyboard Buffer Stati c
Read Keyboard Buffer Dynamic

6400
6401

KSB

Set Keyboard Break
Set Buffer Control Flags

SBC

OUTPUT BUFFER CONTROL
6040
6041
6042

6044
6046

Send A Stri ng
Skip On Teleprinter Flag
Clear Teleprinter Flag
Load Teleprinter and Print
Load Teleprinter Sequence

SAS
TSF
TCF
TPC

TLS

HIGH-SPEED PAPER TAPE READER AND CONTROL (TYPE PC02)
6010
6011
6012
6014

Read Reader Stri ng
Skip On Reader Flag
Read Reader Buffer
Reader Fetch Character

RRS
RSF
RRB
RFC

HIGH-SPEED PAPER TAPE PUNCH AND CONTROL (TYPE PC03)
6020
6021
6022
6024
6026

Punch String
Skip On Punch Flag
Clear Punch Flag
Load Punch Buffer and Punch Character
Load Punch Buffer Sequence

PST
PSF
PCF
PPC
PLS

DECTAPE CONTROL (TYPE TC01)
6764
6771
6772

Load Status Register A
Skip On Flags
Read Status Register B

DTXA
DTSF
DTRB

AUTOMATIC LINE PRINTER AND CONTROL (TYPE 645)
6651
6652

LSE
LCB

6654

LLB

6661
6662
6664

LSD
LCF
LPR

Skip On Line Printer Error
Clear Printer Buffer
Load Pri nter Buffer
Skip On Line Printer Done Flag
Clear Line Printer Flags
Clear Format Register

INCREMENT AL PLOTTER AND CONTROL (TYPE 350B)
6501
6502
6504
6511
6512

Skip On Plotter Flag
Clear Plotter Flag
Pen Up
Pen Right
Drum Up

PLSF
PLCF
PLPU
PLPR
PLDU

C-2

INCREMENTAL PLOTTER AND CONTROL (TYPE 350B) (Cont)
6514
6521
6522
6524

PLDD
PLPL
PLUD
PLPD

Drum Down
Pen Left
Drum Up
Pen Down

CARD READER AND CONTROL (TYPE 451)
6630
6632

6634
6671
6672
6674

RCS
CRSF
CERS
CRRB
CRSA
CRSB

Read Card String
Skip On Card Reader Flag
Read Card Equipment Status
Read Card Reader Buffer
Select Alphanumeric
Select Binary

C-3

APPENDIX D
REQUIRED MODIACATIONS

The PDP-8/1 or PDP-8 computer must have the following KT08/1 time-sharing modifications
to be used in a TSS/8 system.
a. USER FLAG REGISTER (UF) - UF is a l-bit register that specified Monitor (UF=O) or
user (UF=l) mode. In Monitor mode all instructions are legal; in user mode HALT, OSR, and lOT
instructions are trapped via the program interrupt system. UF is cleared by the LOAD ADDress switch.
b. SAVE FIELD REGISTER EXTENSION (SF6) - When a program interrupt occurs, this bit
is cleared and then loaded from the UF.
c. USER BUFFER REGISTER (UB) - The UB serves as a l-bit input buffer for the UFo All
transfers into the UF are made through the UB, except transfers from the computer console switches.
The Change User Flag (CUF) instruction loads the UB with the value contained in the Memory Buffer
(MB). The Restore Memory Field (RMF) instruction transfers the contents of SF6 into the UB to restore
the UF to the condition that existed prior to a program interrupt. The UF is cleared by the LOAD
ADDress switch.
The following machine instructions have been changed to operate as indicated.
a.

Name and Mnemonic: CHANGE USER FLAG (CUF)
Octal Codes: 6264 and 6274
Execution Time: 1.5 ~s
Operation: 6264 sets the UF to 0; 6274 sets the UF to 1. The next JMP or JMS
instruction causes the appropriate mode to be entered.
Symbol:

MB8'" UB

Name and Mnemonic: SKIP ON USER lOT (SKIOT)
Octa I Code: 6245
Execution Time: 1.5 ~s
Operation: HALT, OSR, and lOTs when executed with UF=l, sets the user lOT
(UIOT) flag and, if the program interrupt is enabled, causes an interrupt.

Name and Mnemonic: CLEAR USER lOT (ClOT)
Octal Code: 6204
Execution Time: 1.5 ~s
Operation: Clears the user lOT (UIOT) flag.
Symbol:

0'" UIOT

Name and Mnemonic: READ INTERRUPT BUFFER (RIB)
Octal Code: 6234
Execution Time: 1.5 ~s

D-l

Operation: The contents of the Instruction Field, Data Field, and User Flag held in
the Save Field Register during a program interrupt are transferred into bits
6 through 8, 9 through 11, and 5, respectively.
Symbols:
e.

SFO-2 - AC6-8, SF3-5 - AC9-11, SF6 - AC5

Name and Mnemonic: RESTORE MEMORY FIELD (RMF)
Octal Code: 6244
Execution Time: 1.5 !-IS
Operation: This instruction is used upon exit from the program interrupt subroutine in
another field. The Instruction Field, Data Field, and User Flag that were
interrupted by the subroutine are restored by transferring the contents of
the Save Field Register into the Instruction Buffer and Data Field Registers
and the User Buffer.
Symbols:

SFO-2 - IB, SF3-5 - DF, SF6 - UB

D-2

APPENDIX E
STORAGE ALLOCATION

E.l

STORAGE MAP
A mental picture of the system's storage allocation is illustrated below.

pop-ell
CORE MEMORY

FIELD 0

FIELD 1

~--

.....

SYSTEM
INTERPRETER
AND
ERROR

.,./

,
SYSTEM
INITlALIZATION

FILE
PHANTOM

•

RESIDENT
MONITOR

USER
PROGRAMS

~
~

USER
PROGRAMS

FILE
STORAGE

•••

~ >
4K

f414-------- SYSTEM MONITOR ---------1~~
f4--------SWAPPING

Figure E-l

E.2

...

PHANTOM

""
""
""

•••

AREA ----------~~

TSS/8 Storage Map

FILE DIRECTORIES
There are two directories on the disk: the Master Fi Ie Directory, referenced mainly by the

system, and the User File Directory, referenced by the TSS/8 user. One of the functions of the MFD
is to serve as a directory for the UFO. A UFO is a particular user's own file directory and will contain
the names of programs he has created on the disk.
The UFO itself is a file like any other file except that its filename is a binary number in
combination with a four-letter password. The leftmost seven bits of the binary combination are used

E-l

for the project number, and the remai ning five bits are used for the programmer number. When a user
is logged in under a specific project-programmer number and references the disk, he is actually referencing his own area through the UFD having his project-programmer number as its name. He may of
course, specifically code his routine to reference UFD's of other users or the MFD; whether he is successful or not wi II depend upon the type of protection that has been specified for the area he is trying to
reference.
An illustration of tte file directories is shown below.

MASTER FILE DIRECTORY
WO RD 1

PROJECT NO.
( 1 CHAR)
( 1 CHAR.)

USER

PROG. NO.
(1 CHAR.)
(1 CHAR.)

PA SS
WO RD

FI LE

(1 CHAR.)

NA ME

(1CHAR.)

(1 CHAR.)

WO RD

(1 CHAR.)

LINK TO NEXT ENRTY

CONSOLE

lPROTECTED BITS

UNUSED
CPU

SEGMENT COUNT

TIME
WO RD 8