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DEC-D8-SDAA-D

April 1968

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Document:	PDP-8 I Disk Monitor System Programmers Reference Manual Jun1968
Order Number:	DEC-D8-SDAA-D
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Pages:	103
Original Filename:	http://bitsavers.org/pdf/dec/pdp8/diskMonitor/DEC-D8-SDAA-D_PDP-8_I_Disk_Monitor_System_Programmers_Reference_Manual_Jun1968.pdf

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STEM
Y
S
R
O
T
I
DISK MON

PDP-S/I
DISK MONITOR SYSTEM
Programmer's Reference Manual

For additional copies specify Order No. DEC-DS-SDAA-D to Program
Library, Digital Equipment Corporation, Maynard, Mass.

Price: $2.75

DIGITAL EQUIPMENT CORPORATION. MAYNARD, MASSACHUSETTS

1st Printing April 1968
2nd Printing June 1968

CONTENTS
Page
CHAPTER 1
INTRODUCTION
1.1

Equipment Requirements

1-1
CHAPTER 2
MONITOR OPERATION

2. 1

General Description

2-1

2.1.1

Monitor Residence

2-1

2.1.2

System Modes

2-1

2.2

Bootstrapping the Monitor

2-2

2.3

Starting the Monitor

2-3

2.4

Command Strings

2-3

2.4.1

Command String Format

2-4

2.4.2

Examples of Command Strings

2-6

2.5

Loading Programs - Binary Loader

2-7

2.5.1

Binary Loader Operating Procedures

2-7

2.5.2

Binary Loader Error Messages

2-9

2.6

Saving Programs (Save Command)

2-10

2.6.1

Save Command Format

2-10

2.6.2

Save Command Processing

2-12

2.7

Ca" i ng a Program (Ca" Command)

2-12

2.8

System Error Messages

2-13
CHAPTER 3
SYSTEM PROGRAM LIBRARY

3.1

PIP

3-1

3.1 .1

Loading and Saving

3-1

3.1.2

Operating Procedures

3-2

3.1.3

Examples

3-3

3.2

Editor

3-5

3.2.1

Loading and Saving

3-7.

3.2.2

Operating Procedures

3-8

3.2.3

Example

3-9

3.3

PAL-D Disk Assembler

3-10

iii

CONTENTS (Cont)
Page
3.3.1

Loading and Saving

3-10

3.3.2

Operating Procedures

3-11

3.3.3

Examples

3-13

3.4

FORTRAN-D

3-13

3.4.1

Compiler

3-16

3.4.2

Operating System

3-22

3.4.3

Examples

3-31

3.5

DDT-D

3-33

3.5.1

Loading and Saving

3-36

3.5.2

Operating Procedures

3-37

3.5.3

Examples

3-37
APPENDIX A
SYSTEM GENERATION

A-1

APPENDIX B
SYSTEM FORMATS

B-1

APPENDIX C
COMMAND DECODER

C-1

APPENDIX 0
BI NARY LOADER

0-1

APPENDIX E
SYSTEM PROGRAMS

E-1

TABLES
Page
2-1

System Error Messages

2-13

3-1

Special Key Functions

3-5

3-2

Summary of Editor Commands

3-6

3-3

PAL-D Pseudo-Operators

3-10

3-4

PAL-D Error Messages

3-12

3-5

Summary of FORTRAN Statements

3-14

3-6

Compiler Systems Diagnostics

3-19

3-7

Compiler Compilation Diagnostics

3-20

3-8

Operating System Diagnostics

3-25

3-9

DDT-D Commands

3-36

I LLU STRA TI ON S

B-1

Disk Storage Layout

B-2

DECtape Storage Layout

B-3

Directory Name (DN) Block Format

B-4

Storage Allocation Map (SAM) Block Format

B-6

B-5

Contiguous-Page Save File Format

B-8

B-6

Noncontiguous-Page Save File Format

B-9

B-7

Sample PIP Directory Listing

B-10

B-8

Monitor-Time vs User-Time Core Usage

B-11

B-9

Core Usage During SAVE Command Execution

B-12

B-10

Core Usage During CALL Command Execution

B-13

B-11

Monitor Flow Chart (Part 1)

B-14

B-11

Monitor Flow Chart (Part 2)

B-15

B-11

Monitor Flow Chart (Part 3)

B-16

C-1

Output List Produced by Command Decoder

C-3

C-2

Command Decoder Core Usage

C-4

C-3

Command Decoder Flow Chart (Part 1)

C-5

C-3

Command Decoder Flow Chart (Part 2)

C-6

C-3

Command Decoder Flow Chart (Part 3)

C-7

C-3

Command Decoder'Flow Chart (Part 4)

C-8

C-3

Command Decoder Flow Chart (Part 5)

C-9

C-3

Command Decoder Flow Chart (Part 6)

C-10

D-1

Binary Loader Flow Chart (Part 1)

D-3

D-1

Binary Loader Flow Chart (Part 2)

D-4

D-1

Binary Loader Flow Chart (Part 3)

D-5

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, 8/5, 8/1, LINC-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
rece ives a spec ifi c 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 ma iling list.

I
I

I.
I
I
I;
II

Ii
I,
I
I

To: Decus Office,
Digital Equipment Corporation,
Maynard, Mass. 01754
Please send DECUS installation membership information.
Please send DEC US individua I membersh ip information.
Please add my name to the DECUSCOPE non-member mailing list.
Name
Company

-----------------------

Address

(Zip Code)

CHAPTER 1
I NTRODUCTI ON

The PDP-8 Disk/DECtape Monitor System is designed for any PDP-8 computer having at
least one DECdisk or one DECtape.

This system consists of a keyboard-oriented Monitor, which en-

ables the user to efficiently control the flow of programs through his PDP-8, and a comprehensive software package, which includes a FORTRAN Compiler, Program Assembly Language (PAL-D), Edit program (Editor), Peripheral Interchange Program (PIP), and Dynamic Debugging Technique (DDT -D)
program. Also provided is a program (Builder) for generating a customized monitor according to the
user's particular machine configuration (amount of core, number of disks or DECtapes, etc.).
The system is modular and open ended, permitting the user to construct the software required
in his environment, and allows the user full access to his disk (or DECtape) - referred to as the system
device - for storage and retrieval of his programs. By typing appropriate commands to the Monitor,
the user can load a program (construct it from one or more units of binary coding previously punched o'ut
on paper tape or written on the disk by the Assembler, and assign it core), save it (write it out, with an
assigned starting address, on the system device), and later call it (read it back into core from the system device) for execution.
1.1

EQUIPMENT REQUIREMENTS
The minimum equipment requirements of the PDP-8 Disk/DECtape Monitor System are as

follows.
A basic PDP-8, PDP-8/S, or PDP-8/1
4K of core
Teletype
3-Cycle Data Break (Option required with PDP-8/S)
At least one DF32 Random Access DECdisk File or a TCOl Automatic Control
with a TU55 DECtape transport. The DECtape must have timing and mark
tracks wri tten on it prior to use.

NOTE
The system will recognize up to 32K of core, up to
four disks (l Type DF32 and 3 Type D$32 I s), up to
eight DECtapes (TC01's only) and a high-speed papertape reader.

1-1

CHAPTER 2
MONITOR OPERATION

This chapter contains a discussion of the operation of the Monitor.

Succeeding chapters

contain descriptions and operating procedures for the system programs.
2.1

GENERAL DESCRIPTION
The PDP-8 Disk/DECtape Monitor System permits the user to control the flow of programs

through his computer and takes full advantage of the extended memory capabilities of disk or DECtape.
In addition to the Monitor, the system also contains a library of system programs. Together, they provide the user with the capabilities of compiling, assembling, editing, loading, saving, calling, and
debugging his own programs.
2.1.1

Mon itor Residence
Monitor, as well as system and user programs, is stored on and retrieved from the user's

system device.

To obtain a working Monitor, the user must first build his own customized version, via

the easy-to-use dialogue technique of the System Builder program and store this version on his system
device. Following this, the user then creates his System Program library on the system device. Both
of these procedures are described in Appendix A.
In core, the resident part of Monitor (called head of monitor) resides in the top page (locations 7600 through 7777) of field O. The starting address of Monitor is 7600; 7642 is entry address to
the system I/O routine, which performs all reading and writing on the system device.' Nonresident
portions of Monitor, such as those routines which perform SAVEs and CAlls, are automatically called
in as needed, and in core, they share the area from location 7000 through 7577. (These portions
disappear after use, leaving this area for the user.)
Specific diagrams showing the allocation of the system, both on the system device and in
core, are given in Appendix B.

2.1.2

System Modes
At any point in time, the system is running in one of two modes:

Monitor mode or ~ mode.

Monitor mode is entered (1) whenever the Monitor is started (see Paragraph 2.2)-or E2) when
CTRljC (t C) is typed while running any system program. Monitor mode is signalled by the Monitor
typeout of a dot (.). At both Monitor and system program time, Monitor is able to sense a tC typein,
causing the system to enter Monitor mode, return to Monitor at location 7600, and respond with a dot
(.) typeout. At this point, the user can issue any Monitor command via the Teletype keyboard.
User mode is present whenever the system is executing a system or user program. System programs signal user mode by responding with an asterisk (*) typeout.

;

2-1

2.2

BOOTSTRAPPING THE MONITOR
The following discussion assumes that the user has built a customized Monitor and has stored

it on his system device, according to the procedure described in Appendix A.
The bootstrapping of Monitor into core is necessary only when the resident Monitor area
(locations 7600 through 7777) has been cleared or its contents otherwise destroyed. System Builder
leaves the resident portion of Monitor in core after building. Turning the computer off and subsequently
turning it on again does not normally destroy the contents of core.
The bootstrap procedure is as follows.
a.

Toggle in one of the following bootstrap routines, depending upon the type of system

device.
Disk
Location

Contents

0200
0201
0202
0203
0204
7750
7751
DECtape
Location

0200
0201
0202
0203
0204
0205
0206
0207
0210
0211
0212
0213
0214
0215
0216

51mbolic

6603

DMAR

6622
5201
5604
7600
7576
7576

DFSC
JMP .-1
JMP I .+1

7600

Contents

51mbolic

7600
1216
4210
1217
3620
1222
4210
5600
0000
6766
3621
6771
5213
5610
0600

BEG,

*200
7600
TAD MVB
JMS DO
TAD M201
DCA I CA
TAD RF
JMS DO
JMP I BEG

DO,

0000
DTXA DTCA
DCA I WC
DTSF
JMP .-1
JMP I DO

MVB,

2-2

0600

DECtape
Location

Contents

0217

7577

M201,

-201

0220

7755

CA,

7755

0221

7754

WC,

7754

0222

0220

RF,

0220

51mbolic

b. After toggling in one of the above bootstrap routines, set the switches to 200 and press
LOAD ADDress and START. Monitor should respond with a dot (.) after it has been brought into
core.
2.3

STARTING THE MONITOR
Monitor start is at location 7600. A jump to this location can be made by either (1) stop-

ping the machine, setting the switches to 7600, and pressing LOAD ADDress and START, or (2) typing
IC when in Monitor mode or when a system program (or any user program which includes coding to sense
.) •
•
1
a I Cty pem
IS runnmg.
Monitor start performs the following actions.
a. Saves the coding from location 7200 through 7577 in the first two scratch blocks on the
system device.
b.

Reads blocks 1 and 2 (containing the rest of Monitor) from the system device into these

Transfers control to Monitor, which responds with a carriage return, line feed, and a

locations.
dot.
A monitor restart can be performed by typing RUBOUT to Monitor. A Monitor restart performs
the same actions as described above except for Subparagraph a. A common use for RUBOUT is to terminate a command string when the operator has discovered that he has made a mistake. The command
string is ignored, and Monitor responds as described in Subparagraph c. The user core image on the
system device is not changed by RUBOUT (it is changed, however, by tC).
2.4

COMMAND STRINGS
The user types commands in the form of command strings to direct Monitor, or a system pro-

gram, to perform some action. Command strings are simple in format and afford the user an easy means
of communicating with the system.
Monitor indicates its readiness to accept a command string by typing a dot, and at this point,
the user can type some Monitor command, such as CALL or SAVE.

1 A start instruction (ST=7600) is issued when running Loader causes a jump to 7600 after loading has
been performed. Certain errors also cause a jump to this location.

2-3

System programs indicate their readiness to receive information by typing either an asterisk
or a query. The most common queries are as follows.
*OUT-

Requests that the user specify one output device name. In the case of
disk or DECtape thf filename to be assigned to the output data must
also be specified.

*IN-

Requests that the user specify one or more input device names. For
disk and DECtape, filenames of input files must also be specified. 1

*OPT-

Requests that the user specify one option or switch, entered as a single
alphanumeric character; see Chapter 3 for options available in each
system program.

. This communication between the system and the user is handled by a portion of Monitor
known as the Command Decoder. 2

Command Decoder is called into core by the system when needed

and occupies any four contiguous pages of core. A description of its core allocation and calling procedure, plus a flow chart, is given in Appendix C. Error messages produced by Command Decoder are
listed in Paragraph 2.8. Messages unique to individual system programs are given in Chapter 3.

2.4.1

Command String Format
Command strings are composed of a few basic elements and follow certain rules of punctua-

tion. Their basic elements are as follows.
a.

Device names

Filenames

Punctuation

Special characters

Each of these elements is described in the following paragraphs.

2.4.1.1

Device Names - Device names permitted in command strings are as follows.
Dn:

DECtape unit, if both disk and DECtape are present in the system
(n = unit number, 0 through 7)

S:
R:
T:

System device (disk or DECtape unit 0)
High-speed paper tape equipment (reader or punch)
Low-speed paper tape equipment on the Teletype (reader or punch)

1 Device nam:s and filenames are explained in Paragraph 2.4.1.
2 Command Decoder is a system program ( .CD.) which is saved on the system device at build time.

2-4

2.4.1.2

Filenames - Filenames are limited to four characters in length and can be composed of any

combination of alphanumeric characters or special characters 1 with the following exceptions.
a. Imbedded spaces cannot appear in a filename (they are ignored}.2
spaces are permitted.
b.

However, trailing

A filename cannot be one of the following words or symbols.
CALL

SAVE

Extensions to the filenames specified by the user are automatically appended by the system.
They are used internally by the system and cannot be referred to or modified by the user. 3
SYS (n)

Saved system program file in core bank n.

USER (n)

Saved user program file in core bank n.

ASCII
BINARY

Source language program file (input to PAL-D Assembler or FORTRAN
Compiler) •
Binary program file (output from PAL-D Assembler).

FTC BIN

Interpretive binary file (output from FORTRAN Compiler).

Filenames (and extensions) are meaningful only for file structured devices (disk and DECtape).
If they are specified for other devices, they are ignored. Both the fi lename and extension name appear
on directory listings produced by the list feature in PIP.4
Example:

NAME

TYPE

8D
PIP • SYS (0)
SRC1. ASCII
BIN • BINARY
SRC1 • USER(O)
2.4.1.3

BLK
0015
0007
0001
0001

Punctuation - Punctuation within command strings is as follows.

;

Used to separate device names, when more than one is given in a
command string. The ~e is also used to separate core references
in a SAVE command strin~, when more than one contiguous area of core
i s speci fi ed •
t 0 ."'~ tVl r:t
Precedes the entry point specification in a SAVE command.
Terminates each device name. The colon is also used following the
filename in a SAVE command to indicate that the file is to be saved as
a user program.

1 Although both printing and nonprinting keyboard characters are allowable, printing characters are
recommended.
2 Note that Monitor is given the filename EX C; one reason for this unconventional use of an imbedded
blank is to protect Monitor from accidental destruction by the user (e.g., deletion via PIP).
3 The data structure of these fi Ies is described in Appendix B under "Data Structure. II
4"8D" in example means VERSION 8, change D.

2-5

Separates the beginning and ending addresses of a contiguous core area
specification in a SAVE command.
Follows the filename in a SAVE command when a file is to be saved as
a system program.
2.4.1.4

Special Characters - Special characters are used as described below.
tC

If given while the system is in Monitor mode or a system program is running,
control is returned to Monitor start (location 7600). Monitor responds with a dot.
tC is typed by holding down the CTRL key and striking C.
not echo (does not print).

t C does

Typed in response to a t typeout. Instructs the system to proceed with
the next operation. 1 t Pis typed by holding down the CTRL key and
striking P. tp does not echo (does not print).
Carriage return terminates current command string input. When typed
alone, in response to a system query, it indicates that the user does
not desire to specify the item (e.g., device name) requested.

RUBOUT

2.4.2

Causes the current command string to be ignored, and the system
returns to the beginning of the command string and is ready to receive
a new command. RUB OUT does not echo.

Examples of Command Strings
These examples illustrate the elements and rules explained above. Samples of both Monitor

commands and system program commands are given. 2
Monitor Commands:
• CALL PRGI J

Call the user program file, PRGl, from the system
device into core for execution.

..:. SAVE PALO 1 0-7577; 6200 J

Save a program, previously loaded by Loader into
locations 0 through 7577 of core, on the system
device as a system program (I). Assign a starting
address of 6200 and a filename, PALO.

System Program Commands:

*IN-S:PR02 J

Use the file PR02 on the system device as the
input file.

*IN-S:TSTl,R: J

Use the file TSTl on the system device and one fi Ie
from the high-speed paper tape reader as the input
fi les.

*OUT - 05: SPEC J

Write the output file on OECtape unit No.5 and
assign it the filename SPEC.

tP can also be used to prematurely terminate certain operations while in progress (e.g., the typing
out of a file directory by the list option in PIP).

21n all examples, system response (typeout) is underlined for clarity.

2-6

*OUT-T: J

Punch the output on the Teletype paper tape punch.

*OPT-M

Select option M. 1

Spaces in command strings are ignored. Thus, both examples below are equally correct and
perform the same function.
.SAVE PALO! 0-7577; 6200 J
• SAVE PALO !0-7577; 6200 J
2.5

LOADING PROGRAMS - BINARY LOADER 2
Binary Loader takes as input the binary coding produced by the PA L-D Assembler and loads

it into core in executable form. When loading is completed, Binary Loader "disappears" after first
entering the loaded program at the starting address typed by the user just prior to loading (see Paragraph 2.5.1).

Loader accepts input from the system device or paper tape.

Loader requires one pass for any program which does not load above location 6777 (field 0).
Loader uses core from location 167 through 177 and 6000 through 7577, and the resident portion of
Monitor occupies the remainder of field O. One -pass loading reads input files only once.
Two passes are required for all other programs (i .e., programs loading above 6777). In
two-pass loading, programs can be loaded in all of field 0, except locations 7600 through 7777. 3
Two-pass loading requires that input paper tapes be read through the reader twice.
2.5.1

Binary Loader Operating Procedures
• LOAD J

Direct Monitor to bring Binary Loader from the
system device into core for execution.

*IN-

Loader requests source of input(s}. Type one or
more device names, separated by commas. If an
input device is a file-structured device, include
filename(s}.
Up to five fi les can be specified. 4

Examples

*IN-R: J

Input one tape from the paper tape reader.

*IN-R:,R:,R: J

Input three tapes from the paper tape reader. 5

1 An automatic carriage return occurs after user response to an OPT -request.
2 Binary Loader is a system program saved on the disk at build time. It is called by the user in the same
manner as any system program. It occupies locations 7000-7577 and has a starting address of 7000.
3
In 8K and larger systems, Loader sets up locations 7574 through 7577 to perform a start in fields other
than O. It is the user1s responsibility to protect these locations if he wants to start in other than field O.
4An E or I error message (see Table 2-1) may appear following the entry of an IN command.
5Regardless of whether R: or T: is used to specify paper tape input, the high-speed equipment is used
if it was indicated as present in the system at System Builder time, otherwise the Teletype equipment
is used. This convention is unique to Binary Loader.

2-7

*IN-S:INPT J

Input the file INPT from the system device.

*IN-S:BIN2, R: J

Input the file BIN2 from the syster device and one
tape from the paper tape reader.

*IN-S:BIN1,S:BIN2 J

Input the files BIN1 and BIN2 from the system
device.

If device(s} are valid and filenames (if any) are
actually found on the system device, Loader responds with one asterisk for each correct input.

*OPT-

Loader requests mode desired (one-pass or two-pass).

Examples
*OPT -1

One pass loading desired; no programs are loaded
above location 6777.

*OPT-2
{or anything else}

Two-pass loading desired; programs can be loaded
above location 6777.

*ST=

Loader requests the starting address to which control
is to be transferred when loading is completed. The
address is typed in the form
fnnnn
where
f = field number 2 (omitted if field 0),
and
nnnn = location within field

Examples
*ST= J
}
*ST=7600 J
*ST=OJ

Load into field O.
Return to Monitor after loading.

*ST=30225,)

Load into field 3.
Jump to location 255, field 3, after loading.

*ST=10000,)

Load into field 1.
Return to Monitor after loading into field 1.
Loader now types a series of up-arrows, one at a
time, as explained below.
Following each up-arrow typeout, the user is required to perform one or more actions.

1 Regardless of whether R: or T: is used to specify paper tape input, the high -speed equipment is used
if it was indicated as present in the system at System Builder time, otherwise the Teletype equipment
is used. This convention is unique to Binary Loader.
2 The f-digit forces Loader to start loading into the speci.fied field until a "field bit" is found in the
input.

2-8

tttt

Fi rst up -arrow: Loader is ready to load. If paper
tape inputf put the tape in the reader.
Type tP.
Second up-arrow: End of pass 1. If operating in
one-pass mode, type tP to jump to previously
specified starting address.
If operating in two-pass mode, type tP.
The next two up-arrows appear only if operating
in two-pass mode.
Third up-arrow: Reload paper tape input for pass 2.
Type t P.
Fourth up -arrow: End of pass 2. Type t P to jump
to previously specified starting address.
Multiple Input Files
An up -arrow is typed out as the processing of each
input file is completed. If paper tape input,
insert the next fi Ie in the reader and type t P.
Repeat the above step until all files given in response to the *1 N - request have been processed.
If in two-pass mode, each tape must be entered
twice, in the order
Tl, 1'2, T3, •••• T1 , 1'2, T3, ••••
After all fi Ies have been entered the required number of times, type tP to jump to the previously
specified starting address.
NOTE
After each input paper tape is read, the high -speed paper
tape version of Loader loops unti I the user types tP to continue.
However, the low-speed paper tape version halts. Thus, when
using the Teletype paper tape equipment for input, the user
need not type t P but press CONT on the console and start
- -the paper tape reader.

At this point, Binary Loader disappears and control is transferred to the previously specified
starting address.
A flow chart of Binary Loader can be found in Appendix D.
2.5.2

Binary Loader Error Messages
An illegal checksum error condition causes Loader to type

?
and return to Monitor after the user types t P or t C. Error messages for illegal filenames or devices are
as specified in Paragraph 2.8.

11f Teletype paper tape equipment is used, type t P before turning on the reader.

2-9

2.6

SAVING PROGRAMS (SAVE COMMAND)
The SAVE command enables the user to write core images of system or user programs from

core onto his system device for subsequent call-in (CAll) and execution. For example, a program
which has been loaded by Binary loader can be stored on the system device by the SAVE command.
Or, a previously saved program which has been called in and modified by DDT can be stored in its updated version on the system device, overlaying the old version if desired.
Core images can be saved in units of one or more pages, each page occupying one block on
the system device. If a core specification (see below) addresses only a portion of a page, the entire
page is written out. For example, the core specification 45-150 is treated as though it were 0-177.
Core areas to be saved may be contiguous or noncontiguous as desired by the user. Up to 3210 core
specifications, in any combination of monotonically increasing single-page or multiple-page requests,
can be entered in a single SAVE command.
2.6.1

SAVE Command Format
• SAVE

flI ename

cOO"e -'ped fi co'; on" ••• , ent')' - point.

SAVE

Directs Monitor to call in the nonresident SAVE routine.

filename

The filename (program name) to be assigned to the file on the
systems device. This name will be used to call the file later
when the user wants to read in and execute the program.
Restrictions on the formation of filenames can be found in
Paragraph 2.4.1 .2. Any previously saved program wi th the
same "filename" and having the same extension will be automatically overwritten.

! is typed immediately after the filename of a file if the user
desires to save it as a systbm program (e.g., PIP). A program
saved in this manner can e called in by simply typing its
name to Monitor (the word CAll is not required) •
• filename J
An extension name of • SYS is automatically appended to the
filename.
: is typed immediately after the filename of a file if the user
desires to save it as a ~ program. A program saved in this
manner can be called in and executed later via the CAll
command.
.CAll filename ,J
An extension name of • USER is automatically appended to the
filename.

core -specifications

Up to 32 core specifications can be entered in a single SAVE
command. Each core specification is separated from the following one by a comma. The last core specification in the series
is followed by a semicolon. Addresses are expressed in octal.

2-10

Singl e -page core specification
fnnnn
where
f = field number (can be omitted if field 0).
nnnn = any location within the page which the user
desires to save.

Examples

Saves page 0 (locations 0 through 177)
offield O.

3570

Saves ,W ~1. "locations 3400
of field O.
through 35

30100

Saves page 0 (locations 0 through 177)
of field 3.

Multiple -page core specification
When a user wishes to save a core area of several contiguous
pages, he can type a multiple -page core specification in the
format
fnnnn 1-nnnn2
where
f = field number (can be omitted if field 0).
nnnn 1 = any location within the first page of the series
of contiguous pages to be saved.
nnnn 2 = any location within the last page of the series
of contiguous pages to be saved.
The following rules apply.
a. The beginn ing address of a mul ti pi e -page request must be
smaller than the ending address (nnnn 1 must be smaller than
nnnn 2 )·
b. Both addresses must be in the same field.
c. The field number (f) must be within the range of your
system; however, no check for the validity of this number is
performed at SAVE time.
Examples
0-7577
10000-7777

Saves all of field O.
Saves all of field 1. Note that this is
the same as typing
10000 -17777
See below for explanation of how the
field number (5th significant digit to
the left of the decimal point) is
"remembered. "

2-11

30425-745

Saves locations 400 through 777
(pages 3 and 4) of field 3.

NOTE
Only one field can be saved by each SAVE command.
If mul tiple fields are to be saved, a separate SAVE command must be given for each.
entry -point

The entry point of the saved program, in the format
Fnnnn (see explanation above)
An entry point of 0 causes a return to Monitor at CALL time,
regardless of the field into which the program was saved.
NOTE
The last nonzero field number encountered in a SAVE
command string is remembered and prefixed to a" other
addresses in the command string. (Remember: only
one field can be referred to in each command string.)
Example:

The following entries are identical in meaning.

SAVE PRGA: 10000-10m, 11400, l600-17m; 10200
SAVE PRGA: 30000-777, 51400, 26000-m7; 10200
SAVE PRGA: 10000-777, 1400, 6000-7777; 200
SAVE PRGA: 0-777, 1400, 60oo-7m; 10200
In each of these examples, all addresses are treated as
being in field 1, because the last five-digit entry seen
contained a most significant digit 1 •

2.6.2

SAVE Command Processing
A list of the required pages is constructed from the information typed by the user and a block

requirement count is kept. When the user types the terminating carriage return (J), allowing the
SAVE process to begin, a directory name search on the system device is initiated. If a file having the
same name as the filename in the SAVE command is found, it is replaced by the file now being saved.
If no such file is found, a new file is created. Next, a storage availability search finds a sufficient
number of available blocks on the system device to satisfy the block requirement count. (See above.)
These block numbers are stored in a corresponding block list; the blocks are then filled with the contents of the pages to be saved. When the SAVE process is completed, control returns to Monitor (7600).

2.7

CALLING A PROGRAM (CALL COMMAND)
Once a file has been loaded and saved, it can be called into core as desired. There are two

types of CALL command strings:

one for system programs and the other for user programs.

The CALL command string format for system programs (programs saved by a SAVE command
string in which the fi lename was followed by a !) is
• filename J
where filename is the same as the one used in the SAVE command string which saved it.

2-12

The CALL command string format for user programs (programs saved by a SAVE command
string in which the filename was followed by a :) is
.CALL filename J
When a program is called, a directory name search is performed on the system device.
Associated with the directory entry is the entry point of the program and information concerning file
protection and memory extension. If the appropriate directory name entry is found and the file has the
proper extension (. SY,S or .USER), calling proceeds. If not, the calling process is terminated, ? is
typed and control is returned to Iv\onitor.
2.~

SYSTEM ERROR MESSAGES
As an input command string is being typed, Monitor recognizes any incorrect syntax and

remembers it. When the user types a carriage return, Monitor responds with a ? to indicate invalid
input.
Error messages output by Command Decoder are given in Table 2-1.
Table 2-1
System Error Messages
Message

Meaning

?
D

Illegal syntax or miscellaneous error condition
Directory on the systems device is full

Too many inputs or outputs were entered

No such inputs

System I/O failure

Local errors in each system program are given in Chapter 3.
Monitor time read or write errors cause a halt to occur. Persistence of this condition indicates a hardware failure, as the system I/O routine attempts to read or write three times before halting.

'2.8

MONITOR START CONDITION

~~~n a CTRLjC or start at 76008 has just occurred, the Monitor saves three
pages 0

core on the disk scratch blocks. To recover this core perform the following:

a. Fo n~t type a second CTRLjC, as the user core memory from 7000-7577 (the
ocatlons removed from core) are still on the disk.
b. Type ~'SAVE SCRATC~: 7000-7577; nd" (n is the point in the System Pro ram
to which you would like to return, e.g., 200 for FOCAL).
9
c • Type "CALL SCRATCH J ". This restarts you with your core intact.

2-13

CHAPTER 3
SYSTEM PROGRAM LIBRARY

The Monitor System's library of programs presently consists of the Peripheral Interchange
Program (PIP), Disk System Editor (Editor), PAL-D Disk Assembler (PAL-D), 4K Disk FORTRAN
(FORTRAN-D), and Dynamic Debugging Technique for Disk (DDT-D) I and this Iist is destined to
lengthen with time. A section of this chapter is devoted to each program in the library.
To load a program using the Monitor System, the Loader makes certain queries to which the
user must type a reply. The queries are the same for all programs. The user's replies will vary, however,
depending on the particulars of the program being loaded.
When loading a program into core, the user should first check to see whether Monitor is in
core. This is done by typing tC (CTRL key and then the C key), The tC will not echo (not print on
the teleprinter), If Monitor is in core, it will respond by typing a period (. ) at the left margin of the
teleprinter paper. If a period is not typed in response to tC, Monitor is not in core. Therefore, the
user should refer to Chapter 2 of this manual for information on building Monitor and putting it into
core.
The Iibrary system incl udes the Binary Loader (LOAD) wh ich is automatically saved on the
disk at build time. (For Loader operating procedures see Paragraph 2.5.)
The user may save any program on the disk by responding to the last period typed by Monitor
with the word SAVE, a four character name of the program, the type of program (user or system),
whether it's a one or more page save, and the location of its starting address, as is thoroughly described in Paragraph 2.6.
After each program is saved on the system device, it may be called (i .e., transferred from
the disk into core) merely by responding to Monitor (to a period) with the four characters designated as
the name of that progr"am, as explained in Paragraph 2,7.
3.1

PI P
PIP (~eripheral .!..nterchange ~rogram) performs general utility operations, such as listing the

contents of specified directories, deleting unwanted files from the system device, and transferring files
between devices, and copying specified files.

PIP enables the user to do any of the above operations

merely by typing commands from the teleprinter keyboard.

3. 1 .1

Loading and Saving
PIP is loaded into core as indicated in Appendix E. Core requirements, starting address, and

number of passes through the Binary Loader (hereafter frequently referred to merely as Loader) are also
found in Appendix E.
To load PIP into core, the user calls LOAD, using Monitor, and replies to the system responses as explained in Chapter 2.

3-1

When in core, PIP may be saved on the system device as a system device by Monitor, as indicated in Appendix E. (See Paragraph 2.6.1 for a detailed description of the SAVE format.)
When loading and saving PI P, the printout wi II take the following format. (See Appendix E
for precise core limits.)
• LOAD J
*IN-R: J

*OPT-1 J
*ST- J

l.!

.:..SAVE PIP! 0-3177;1oo0,J

':",J

3.1.2

Operating Procedures
PI P has now been loaded into core and saved on the di sk. To use PI P, the user must call PI P

via Monitor which can be done only in response to a period. If a period is not present as the last system
response, the user must type tC, which should cause Monitor to type the needed period. The printout
should appear as follows:
• PI'P ,J
which transfers PIP from the disk into core. PIP now responds with
*OPTand waits for the user to select and specify one of the followi~9';~

B
D
F
M
P
R

S
U
,J or A

List entire system directory
Copy a binary file
Delete a file to be specified
Copy a FORTRAN binary fi Ie
Move directory to safe disk
Protect disk 1 (blocks 0-176)
Restore directory from safe disk
Copy a system fi Ie 1
Copy a user fi Ie 1
Copy a USA SCII file

If the user selects an option using any character other than one of those listed above, the option i,s
recognized as illegal; PIP ignores the request, types? (question mark), a,nd asks for another option
character. The output appears as follows:
*OPT-G ,J
-1*OPT-

1 User system files may not be copied onto paper tape.

7.,.O~i~ L4lf1d. D C4,.e tl" V"Y9Io"tPIh ~qf"- tl€3-2

,' ~

When the user specifies the D (delete a file) option, PIP responds with
*FI LE TYPE{A, B, F, U, S)where A,B,F ,U, S are the legal options from which the user may choose. If the user1s reply is S (system
file), PIP asks
REALLY?
PIP will not delete a system file unless the user answers by typing
Y J (meaning yes)
Any other answer causes PIP to repeat the fi Ie type request.
If the file requested for deletion is Monitor (EX C),PIPwill not delete it even if the user
answers to REALLY? with a Y. Instead, the request is ignored, and Monitor types a ?
When PIP is satisfied with the user1s reply to the file type request, it will type
*INWhen PIP recognizes a legal option character other than D, it will type *IN-, as shown in the example below.
The user should now specify the input device 1 as explained at the beginning of this chapter
and in Paragraph 2.4.

3.1.3

Examples
.!.PIP J
*OPT-L J

User calls PIP
and requests that it list option

*IN-S: J

of the system device directory

FB=2426

PIP types number of free {unused} blocks remaining
on specified device

NAME TYPE

8D
PALD • SYS 0
EDIT • SYS 0
LOAD. SYS 0
.CD •• SYS 0
PIP
• SYS 0
DDT • ASCII
FOO • USER CO)
BAR • SYS CO}
*OPT-D J

BLK

0037
0015
0003
0006
0015

followed by file name and description; e.g., PAL-D
is a system program in field 0 and occupies 378
.
blocks of storage

0062
0001
0037

*FILE TYPE {A,B,F,U,S)-U J

User requests delete option
and specifies type of file, U (user)

1 Options requiring input ask only for an input device; those requiring both input and output request a
devi ce for each.

3-3

*IN-S:FOO J

and device and file name

*OPT-D J

User requests delete option

*FILE TYPE(A,B,F,U,S)-S J
REALLY?Y J

and specifies type of file, S (system) (PIP double
checks); Y is the only meaningful answer

*IN-S:BAR J

User specifies file and filename

*OPT-L J

User requests list option

*IN-S: J

and system device directory

FB=2466

Note increase of 408 free blocks (see above)

NAME TYPE

BLK

80
PALO • SYS 0
EDIT .SYS 0
LOAD .SYS 0
.CD •• SYS 0
PIP
.SYS 0
DDT .ASCII

0037
0015
0003
0006
0015
0062

Note removal of two deleted files

*OPT-D J

User requests delete option

*FILE TYPE (A,B,F,U,S)-S J
REALLY?NJ
*FILE TYPE(A,B,F,U,S)-S J
REALLY?W J
*FI LE TYPE(A, B, F, U, S)-S J
REALLY?Y J

Y is only response for deletion of a system file;
other responses cause PI P to repeat the fi Ie type
request

*IN-S: EX C J

-r-

Even if user responds to REALLY? with Y, PI P wi"
not delete the Monitor file

*OPT-D J
*FILE TYPE(A,B,F,U,S)-S J
REALLY?Y J
*IN-S:EX C J

-r-

*OPT-D ,J
*FI LE TYPE(A, B, F, U, S)-U J
*IN-S:NONE J

-r-

PIP knows NONE is not an existing user file name on
the system device and indicates by typing ?

*FILE TYPE (A,B, F, U, S)-A J

User requests USA SCII file option

*IN-S:EDIT J

PIPalso knows when the file name and file type
don't match; EDIT is a system program

*OPT-D J

-r-

*OPT-D J
*FILE TYPE (A,B,F,U,S)-B J
*IN -S:EDIT J

TOPT-

3-4

3.2

EDITOR
Editor (Disk System Editor) enables the user to generate and edit symbolic programs on-line

from the teleprinter keyboard. The symbol ic program may be either printed on the teleprinter, punched
on paper tape using the high-or low-speed punch, or saved on the system device as a user program.
Editor operates ei ther in command or text mode. In command mode, all typed input is interpreted as a command instructing Editor to perform a certain operation or to allow the user to perform
an operation on the text stored in the buffer. In text mode, all typed input is interpreted as text to
replace, to be inserted into, or to be appended to the contents of the text buffer.
The command language of the Disk System Editor is identical to that of the PDP-8 Symbolic
Editor (DEC-08-ESAB-D) but with the following exceptions.
a.

Special characters:
tP

During output, progress stops and control is returned to command
mode.

Always returns control to Ivbnitor.

Commands:
P

Proceed, and output entire contents of the buffer followed by a form
feed and return to command mode.

Output line n, followed by a form feed, return to command mode.

m,nP

Output lines m through n, followed by a form feed, return to command mode.

Illegal command

Process entire file (perform enough NEXT commands to fill the file)
and create an end -of -fi Ie indicator (legal only for output to the
system device).

Certain keys have special operating functions. These keys and their associated functions are
listed in Table 3-1.
Table 3-1
Special Key Functions
Functions

Key

J (carriage return)
+-

(back arrow)

Text mode: Enter the I ine in the text buffer.
Command mode: Execute the command.
Text mode: Cancel the entire line of text and
continue typing on same line.
Command mode: cancel command.

'\ (rubout)

Text mode: Delete from right to left one character for each rubout typed (is not in effect during
a READ command).
Command mode: Delete entire command.

FORM FEED

Text mode:

3-5

End of input, return to command mode.

Table 3-1 (Cont)
Special· Key Functions
Key

Functions

• (period)

Command mode: Current line counter used as
argument alone or in combination with + or and a number.

/ (slash)

Command mode: Value equal to number of last
Iine in buffer and used as argument.

J (line feed)

Text mode: Used in SEARCH command to insert a
carriage return/line feed combination into the line
being searched.
Command mode: List the next line.

ALT MODE

Command mode:

List the next line.

ESCape

Command mode:

List the next line.

< (left angle bracket)

Command mode:

List the previous line.

= (equal sign)

Command mode: Used in conjunction with • and /
to obtain their value (. = 27).

: (colon)

COmmand mode:
tion as = •

-tI (tabulation)

Text mode: On output, is interpreted as :.,s
At a tab/rubout combination.

Lower case character, same func-

Table 3-2 is a summary of Editor commands.
Table 3-2
Summary of Editor Commands
Command

Fortnat{s)

Meaning

READ

Read incoming text and append to buffer until a
form feed is encountered.

APPEND

A,J

Append incoming text to any already in the buffer
until a form feed is encountered.

LIST

PROCEED

L ,J
nL·J
m,nL J
P,J
nP ,J
m,nP ,J

list the entire buffer.
List the line n.
List lines m through n.
Proceed and output the entire contents of the
buffer and return to command mode.
Output line n, followed by a form feed.
Output lines m through n, followed by a form feed.

TRAILER

Punch four inches of trailer.

N,J

Punch the entire buffer and a form feed; kill the
buffer and read next page.
Repeat the above sequence n times.

nN ,J
KILL
DELETE

KJ
hD J
m,nD J

Ki II the buffer.
Delete line .n.
Delete lines m through n.

3-6

Table 3-2 (Cont)
Summary of Editor Commands
Command

Format(s}

INSERT

CHANGE

Insert before line one all text until a form feed is
encountered.

nl J

Insert before line n until a form feed is encountered.

nC J

Delete line n and replace it with any number of
lines from the keyboard until a form feed is encountered.
Delete lines m through n, replace from keyboard
as above until form feed is encountered.

m,nC J
MOVE

m,n$kM J

GET

GJ
nG J

S J
nS J
m,nS J

END FILE

Meaning

Move and insert lines m through n before line k.
Get and list the next line beginningwith a tag.
Get and list the next line after line n which begins
with a tag.
Search the entire buffer for the character specified
(but not echoed) after the carriage return;
allow modification when found.
Search line n, as above, allow modification.
Search linesm through n, allow modification.
Process the entire file (perform enough NEXT
commands to pass over the entire file) and
create an end -of-file indication; legal only
for output to the system device. If the lowspeed paper tape reader is used for input while
performing an E command, the paper tape reader
will eventually run out ot tape, and at this point
typing a form feed wi II allow the command to be
completed.

Editor will print an error message consisting of a question mark whenever the user requests
nonexistent information or uses an inconsistent or incorrect format in typing a command. The question
mark will be followed by a carriage return/line feed and the command will be ignored.
3.2.1

Loading and Saving
Editor is loaded into core from punched paper tape in one pass using the loader. When in

core, it occupies locations shown in Appendix E.
To load Editor into core, the user calls LOAD, using Monitor, and replies to the system responses as explained at the beginning of this chapter and in Paragraph 2.5.
When in core, Editor may be s(lved on the system device as a system program by Monitor when
the user types the command indicated in Appendix E.
(See Paragraph 2.6.1 for detained description of the SAVE format.)

3-7

When loading and saving Editor, the printout should appear approximately as follows •
• LOAD';
*IN-R: ""

-*--

*OPT-l J
*51 -7600 J
n
.!.SAVE EDIT!0-3177; 2600 J

3.2.2

(See Appendix E.)

Operating Procedures
Editor is transferred from the system device into core by Monitor when the user types
EDIT J

Editor is now in core and responds by typing
*OUTThe user selects one of the following output devices: (T:) for low-speed reader/punch; (R:) for high-speed
reader/punch; (S:name) for output to the systems device on a file called ~ and types his choice
immediately after OUT-. If the specified device is not valid, that is, not declared when building
Monitor, Editor will respond with an error message (see Paragraph 2.8) and return control to Monitor.
Thus the user must call EDIT and respond to *OUT- with a valid device.
When Editor recognizes a valid device, .it responds with * J (asterisk, carriage return/line
feed) and *IN -, as shown below.

*INThe user now specifies the input device by typing T: J , R: J , or S:nameJ orJ in the same manner as
when replying to *OUT -, above. 1
The Editor responds with
*OPTasking the user to specify one of the following options.

Preserve blanks. Editor normally replaces
multiple blanks (spaces) with tabs, resulting
in considerable saving of space on the system
device.
Enter dynamic deletion mode if input is from the system
device. As the file is read, it is deleted from the system
device, thus allowing space for output if desired. (File
name remains on the directory but without any assigned blocks.)
Combine the functions of Band D options.
None of the above options; assume conversion of
two or more blanks to tabs, and not D.

1With a System Device output, the user must type E J to properly close the output file.

3-8

After the user has specified one of the options listed above, Editor responds with a carriage
return/line feed and asterisk. The entire printout might appear as follows •
• EDITJ
*OUT-R:,J

*IN-T:J

-*--

*OPT-BJ

*
*
The appearance of the last asterisk in the example above indicates that Editor is ready to
accept and operate on the user's symbolic program.
The user may now load the symbol ic program into core by using the procedures described in
Paragraph 2.5.

3.2.3

Example
.:..LOAD J

Call Loader using Monitor

*IN -R: ,J

Input to be from high -speed reader

~EDI"" J

Input device valid
One -pass load
Return to fvionitor after loading
Editor is loaded
and saved on the system device
Call Editor using Monitor

*OUT - S:SRC1 J

Output to be on system device, file named SRC1

*OPT -1 ,J
*ST- J
tt

~SAVE EDIT!0-3177i2600 ,J

*IN-R: J

Input to be from high -speed reader

"!..E ,;

Input device valid
No blanks, no dynamic deletion mode
Read incoming text
Process entire fi Ie

.:..EDIT J

Call Editor using Monitor

*OUT- J

No output desi red

*OPT - ,J
*R J

*IN-S:SRC1 J

Input from filename SRC1

-II:...

Filename valid
No option desired
Read incoming text
list the entire buffer

*OPT!:.R,J

"":'LJ

9400
ODUM,

/STARTING ADDRESS OF PROGRAM
CLA

'OSR'"
/GET LOWER LIMIT
iSCA"LOCK
HLT
OSR
/GET UPPER lIMI T
CMA

(t P was typed here, stopped listing of buffer)

*/L

$
('C was typed here)

3-9

3.3

PAl-D DISK ASSEMBLER
PAl-D, the acronym for ~rogram Assembly .!:anguage for the Qisk system, is the symbolic

assembly program designed primarily for the4K PDP-8 family of computers with disk or DECtape.
The PAl-D Assembler performs many useful functions, making machine language programming easier, faster, and more efficient. Basically, the Assembler processes the user's source program
statements by translating mnemonic operation codes into the binary codes needed in machine instructions, relating symbols to numeric values, assigning absolute core addresses for program instructions and
data, and preparing an output listing of the program which includes notification of any errors detected
during the assembly process.
The user may use pseudo-operators (pseudo-ops) to direct PAl-D to perform certain tasks or
to interpret subsequent coding in a certain manner. Instead of generating instructions or data, pseudoops direct the Assembler on how to proceed with the assembly. Pseudo-ops are maintained in the
Assembler's permanent symbol table.
The following is a summary of PAL-Dis pseudo-ops.
Table 3-3
PAl-D Pseudo-Operators
PseudoOperator

Explanation

PAGE

Set current location counter ~ first location on next page.

PAGE n

Set current location counter to .first location on page n.

FIELD n

load subsequent data in field n.

DECIMAL

Interpret subsequent integers as decimal.

OCTAL

Interpret subsequent integers as octal.

Xl/ST

Data enclosed is not to appear on third pass listing.

TEXT

Input text strings in USA SCII code trimmed to six bits.

End of program, terminate current pass.

PAUSE

End of file, terminate processing, proceed to next file.

EXPUNGE

Erase symbol table, except pseudo-ops.

FIXTAB

Append to symbol table.

The Assembler is thoroughly documented in PAl-D Disk Assembler Programming Nlanual
(Doc. No. DEC-D8-ASAA-D).
3.3.1

loading and Saving
PAl-D is loaded into core from punched paper tape in two passes using Loader. When in

core, it occupies locations, as shown in Appendix E.
To load PAl-D into core, the user calls lOAD using Monitor and replies to the system
responses as explained at the beginning of this chapter.

3-10

When in core, PAL-D may be saved on the system device as a system program by Monitor
as described in Appendix E. (See Paragraph 2.6.1 for a detailed description of the SAVE format.)
When loading and saving PAL-D, the printout should appear approximately as shown below.
(See Paragraph 2.5.)
.LOADJ
*IN-R:J

*OPT-2 J

~r-6POJ
.:...SAVE PALD 10-7577; 6200.1

3.3.2

Operating Procedures
PAL-D is transferred from the system device to core using Monitor. The user begins by

typing
• PALO J
PAL-D responds with a request for the output device by typing
*OUTThe user selects the output device by specifying one of the following.

T: J
R: J

for the high -speed punch

S:name J

for output to the system deviCe as a file called ~

for the low -speed punch

PAL-D then responds with
*INand waits for the user to select the input device{s). Up to five input devices may be specified (for
example, R:, T:, R:, R:, T: J), but in this example the user selected
R: J

input from the high -speed reader

If the user had specified the devices in the parenthetical example above, PAL-D would have
typed an asterisk for each input device that it found val id.
When PA L-D is satisfied that the input device is valid (i .e., the device does exist or the
file is present on the file-structured device), it will request the third-pass listing option by typing
*OPT-

3-11

The user types one of the following.

TJ
RJ

meaning listing and symbols are to be produced on the teleprinter
rrieanin~ listing and symbols are to be produced on the high -speed
reader/punch

meaning no third pass desired

(any other character means no third pass desired)
The entire printout might appear as follows •
• PALD,J
*OUT-T: ,J

*IN-R:J

-*--

*OPT-T J
PAL-D is now ready to proceed with the assembly, pausing only when user intervention is
required (i.e., placing a new paper tape in the reader, turning off the punch, etc.). On these occasions, PAL-D will type an up-arrow (t) on the teleprinter and wait for the user to type tP, indicating
that the user is ready to continue with the assembly.
Assembly may be terminated and control may be returned to Monitor at any time by typing
tC. When assembly is complete, control is automatically returned to Monitor.
PAL-D makes many error checks as it processes source language statements. When an error
is detected the Assembler prints an error message. The format of the error messages is
ERROR CODE

ADDRESS

where ERROR CODE is a two-letter code which specifies the type of error, and ADDRESS is either the
absolute octal address where the error occurred or the address of the error relative to the last symbolic
tag (if there was one) on the current page.
PAL-D's error messages are listed and explained below.
Table 3-4
PAL-D Error Messages
Error Code

Explanation

BE
DE
DF
IC
ID
IE
II
PE
PH
SE
US
ZE

Two PAL-D internal tables have overlapped.
System device error
System device full
Illegal character
Illegal redefinition of a symbol
Illegal equal sign
Illegal indirect address
Current nonzero page exceeded
Phase error
Symbol table exceeded
Undefined symbol.
Page zero exceeded

3-12

3.3.3

Examples
The following example shows the entire process covered in this section •
• LOAD J

Call loader

*IN-R: J

Input to be from high -speed reader

.:..SAVE PALO 10-7577; 6200 ,J

Loader found input device valid
Two-pass load
Return to Monitor after loading
PAL-O is loaded
PAL-O is saved on disk (see Appendix E)

• PALO J

Call PAL-O

*OUT-S:BIN J

Output to filename BIN on system device

filename and system device are valid
Input to filename SRC1 from system device

*OPT-R J
.:..LOAO J

Filename and system device are valid
Output listing and symbols on high-speed reader/punch
Call loader

*IN-S:BIN J

Innut to filename BIN from system device

Filename and system device are valid
PAL-O generates sl.
I. binary code from sources
program in two passes
Return to Monitor after assembly
Source program is translated into a II us_lale binary
code, followed by the output of the listing and symbols
on the high-speed punch

*OPT-2 J
*ST- J
tttt

*IN-S:SRC1 J

*OPT-2 J
*ST= ,J
tttt

3.4

FORTRAN -0

-----

FORTRAN-O (FORmula TRANslation for the Disk System), is an expanded version of standard

PDP-8 FORTRAN designed for PDP-8 computers with disk or OECtape units.
FORTRAN-O contains a compiler and an operating system. The FORTRAN compiler is used
to convert a source program into an object program. The FORTRAN operating system is used to execute
the object program.
This version of FORTRAN is designed to facilitate user/system communication by typing
appropriate commands from the teleprinter keyboard, eliminating the need to toggle input using the
switch registers.
FORTRAN statements specify the computations required to carry out the processes of the
FORTRAN program. There are four types of statements provided for by the FORTRAN language:
a.

Arithmetic statements define a numerical calculation.

Control statements determine the sequence of operation in the program.

Specification statements define the properties of variables, functions, and arrays ap-

pearing in the source program. They also enable the user to control storage allocation.
d.

Input-output statements are used to transmit information between the computer and re-

lated input-output devices.

3-13

A summary of the FORTRAN statements is given in Table 3-5.
Table 3-5
Summary of FORTRAN Statements
Statement and form

Explanation

1. Arithmetic Statements
v

v is a variable (possibly subscripted); e is
an expression.

2. Control Statements
GOTOn

n is a statement number.

GO TO (n1'n 2 , ••• nn),i

n l' ••• nn are statement numbers; i is a nonsubscripted integer variable.
e isan expression; n1,n 2 ,n 3 are statement
numbers.
n is a statement number of a CONTINUE;
i is an integer variable; k 1,k2 ,k 3 are
integers or nonsubscripted integer variables.

CONTINUE

Proc;:eed

PAUSE

Temporarily suspend execution.

PAUSE n

n is an address; subroutine execution wi II
commence at n.

STOP

Terminate execution.

END

Terminate compilation; last statement in
program.

3. Specification statements
DIMENSION v1 (n 1),v 2 (n 2 ,·· .vn (nn)

v1, •• ovn are variable names; n 1,. o.nn are
integers.

DEFINE device

Device is DISK or TAPE, system I/O device.

FORMAT (sl' s2'·· .sn)

s is a data field specification.

COMMENT

Designated by C as first character on line.

4. Input-Output Statements
ACCEPT f,list

f is a FORMAT statement number; list is a
list of variables.

TYPE f,list

f is a FORMAT statement number; list is a
list of variables.

READ u,f,list

u is an integer, representing device from
which data is to be read.
f is a FORMAT statement number; list is a
list of variables.
u is an integer, representing device onto
which data will be written.
f is a FORMAT statement number; list is a
list of variables.

WRITE u,f,list

3-14

The following functions are allowed:
SQTF(x)

square root of x

SINF(x)

sine of x

COSF(x)

cosine of x

ATNF(x)

arctangent of x (in radians)

EXPF(x)

exponential of x

LOGF(x)

logarithm of x

ABSF(x)

absolute value of x

Certain input-output statements have special characteristics when used with disk or DECtape
units.
a. The READ and WRITE statements disable the user from performing sequential input and
output either on paper tape or on the system device.
b. A DEFINE statement must precede the first executable statement in any program by using
the system device to input or output data.
c. When the operating system is called, the input or output filename must be specified by
using the S option if data is to be read from or written on the system device.
d. When a READ statement is used wi th the tel eprinter, the statement differs from the
ACCEPT statement in that the data be ing read is not echoed on the printer.
e. A WRITE statement used with the teleprinter differs from a TYPE statement in that it
always terminates by typing a carrige return-I ine feed.
f. The READ and WRITE statements allow the user to input and ou·tput data on either the
teleprinter, the high :-speed reader/punch, or the system device.
g. When the ACCEPT statement is used, the rubout character deletes the previous number as
shown in the following examples.
T~eed and Corrected

Read

Integer Numbers:
128 1028
128 -28
-128 128

+1028
-128
+128

Floating -point numbers:
+42.0
+42.0
+2.0
-42.2
+2.0 x 105
+2.0 x 105

2 42
+2. 42
-2.0 2.0
42 -42.2
20E6 5
2.0E-6 5
h.

When the READ statement is used, the rubout character is completely ignored.

The following examples show how the READ and WRITE statements might be used in a typical
FORTRAN program.

3-15

C
C
C

EXAMPLE PROGRAM TO READ COORDINATE PAIRS
FROM THE TELETYPE AND STORE THEM ON
THE SYSTEM DEVICE
DEFINE DISK
TYPE 100
100
FORMAT ("ENTER THE NUMBER OF COORDINATE PAIRS'!')
ACCEPT 10,N
10
FORMA T (I)
TYPE 102
102
FORMAT ("NOW ENTER THE COORDINATES'!')
DO 20 1= 1,N
ACCEPT 30,X, Y
WRITE 3,30,X, Y
20
CONTINUE
STOP
30
FORMA T (E, E)
END
Several READ and WRITE statements may occur within a single DO loop and may refer to different devices. The data is written in USA SCII format regardless of the device used. The following
program demonstrates how information previously stored on the disk might be read, processed, and
punched using the high-speed punch.
C
C
6

12
20
30
40

FORTRAN EXAMPLE PROGRAM
DEFINE DISK
DIMENSION X(100), Y(100)
READ DATA FROM THE DISK DEVICE NR3
IDEV=3
SUMX=O
SUMY=O
DO 10 1=1,100
READ IDEV,20,X(1), Y(1)
WRITE 2,20,X(1), Y(1)
SUMX= SUMX+X(1)
SUMY= SUMY+Y(1)
CONTINUE
TYPE 30,SUMX,SUMY
ACCEPT 40,J
IF (J) 12,12,6
STOP
FORMAT (E, E)
FORMAT ("SUM OF X VALUES = ",E, II SUM OF Y VALUES = 11 ,E, 11
//"TYPE 0 TO STOP, 1 TO CONTINUE")
.
FORMA T (1)
END

3.4.1

Compiler
The compiler consists of a loader (FORT) and the main portion of the compiler (.FT.). This
version of the compiler differs from the standard PDP-8 4K FORTRAN compiler in the following ways.
a. It uses the disk or DECtape unit during its operation.
b. It will compile programs which have been stored on the system devices or programs
which have been prepared on punched paper tape.
c. It will generate a FORTRAN binary output file either on the system devices or on
punched paper tape.
d. Significant improvements have been employed with the READ and WRITE statements.

3-16

e.
f.
to Monitor.

Input and output devices are determined using the Command Decoder
It is possible to terminate compilation at any time by typing tC, thus returning control

g. Within certain restrictions, a program compiled on a system device may be executed
immediately when the user types tP after compilation of the program.
h. Statement numbers need not be del imited by a semicolon, unless the user wishes them to
be employed for appearance.
i.
3.4.1.1

Statements without preceding numbers must be preceded by a space, a tab, or a semicolon.

Loading the FORTRAN Compiler -- To load the compiler, the following steps must be

performed.
a. Load the compiler loader (FORT) into core u~ing Loader in one pass and save it on
the system device as shown in Appendix E.
b. Load the compiler (.FT.) into core using Loader in two passes and save it on the sys
tem device as shown in Appendix E. The compiler is now loaded and saved on the system device and is
ready for use. The entire procedure will generate the following printout •
• LOAD ,J
*IN-R: J

*OPT-1 J
*$T=7600J

rr-

.LSAVE FORTlO-1m; 200J
.L lOAD ,J
*IN -R: J
-;---

(See Appendix E.)

*OPT-2 J
*ST=7600J
tttt
.:.SAVE • FT. !200-7377; J (See Appendix E.)
.::..

The loader occupies core locations 0-1777 with a starting address at 200. The compiler
occupies core locations 200-7377, its starting address is not specified since the loader (not the user)
calls.FT. when needed.
3.4.1.2

Operating Procedures -- The FORTRAN compiler is transferred from the system device into

core when the user responds to Monitor's period with FORT, as shown below •
• FORT J
Command Decoder then types
*OUTand waits for the user to specify one of the following:
T: J
R: J
S:name J

Output on low -speed punch/printer
Output on high -speed punch
Output on system device and assign name

No output desi red

3-17

Command Decoder wi II respond with an * when it recognizes a valid output device, and then types
*INand waits ~r the user to specify one of the following:

T:J

Input to be from low -speed reader

R: J

Input to be from high-speed reader

S:name J

Input to be from system device file named

Command Decoder will type an

* when it recognizes a valid input device.

The compiler now assumes control, and if the program to be compiled is on paper tape, the
compi ler types

t when it is ready to receive the tape for compilation.

When the user is ready to read in his program he should type

t P, which initiates compilation.

At the end of compilation the compil er will type any error diagnostics necessary, a carriage return/I ine
feed, and t.
The process described above would produce the following printout •
• FORT J
*OUT-R: J

*IN-R: J

T
t

3.4.1.3

(tC typed here; compilation finished)

Compiler Diagnostics -- Certain errors can make it impossible for the compiler to proceed in

the normal manner. These are referred to as system errors. They may be caused by improperly loading
the compiler, by not having an END statement on a source file, by a machine malfunction, or for
various other reasons.
There are two types of system errors:

those which occur before the compiler has been loaded

into core, and those which occur after the compiler has been loaded into core.

In the first case, the

compiler will type a four-digit error code and return control to the Monitor. In the second case, the
compiler will type SYS followed by a four-digit error code.
to return control to the Monitor.
Table 3-6 lists the system error messages.

3-18

At this point the operator must type tC

Table 3-6
Compiler Systems Diagnostics
Error
Code

0227
0231
0326
0330
1425
1521
1626
1726
3100
3417
4737
6141
6145
6207
6211
6223
6226
6257
6407
6416
6467
6724
6746
7114
7136
7150
7173

Explanation

Could not find Command Decoder on system device
Same as above

Could not find .FT. on system device
Same as above
READ error during directory or SAM block search
Same as above
Same as above
WRITE error during SAM block search

"legal operator on compiler stack 1
1
Pre -precedence error
No input device or invalid input device specified
Attempt to ~ecute a program not compiled onto the system device

Could not find FOSl on system device; if the error occurs, it may
be necessary to reload FORT and FOSt.
READ error white loading FOSL
Error while doing SAM block manipulation 1
Error while loading. FT.
Same as above
Same as above

"legal overlay request 1
Same as above
System device READ error
No END statement on source device
Same as above
Same as above
READ error on system device source file
System device full

WRITE error on system device output file

1 Error may be due to a compiler error or a machine malfunction.

3-19

The example below illustrates the appearance of the error codes •
• FORT J
0227
.FORT J
*OUT- J

Command Decoder not on system device

*IN-S:name J
SYS6141 <tC>

No output file specified

Error messages for errors which occur during compilation of a program are typed out upon
completion of the compilation. These errors are referred to as compilation errors and take the form:

XXXX

The error code
The number of statements since the appearance
of last numbered statement (octal)

The statement number of the last numbered statement
For example, during compilation of the statements

.
.

A= I (J+ 1)
B=;=A * (B+ SINF(THTA)

the error message

would be printed, indicating that an error exists in a statement which occurs 11 statements (octal) after
the appearance of statement 10. The message corresponding to error code 11 shows that th.e number of
left and right parentheses in the statement is not equal. The statement is examined and corrected, then
compi Iation is resumed.
Table 3-7 lists the compilation error
Table 3-7
Compiler Compilation Diagnostics
Error
Code

EXElanation

Mixed mode arithmetic exp~ession

Missing variable or constant in arithmetic expression

Comma was found in an arithmetic expression

Too many operators in this expression

Function argument is in fixed -point mode

Floating-point variable used as a subscript

Too many variable names in this program

Program too large, core storage exceeded

3-20

Table 3-7 (Cont)
Compil er Compi lation Diagnostics
Error
Code

3.4.1.4

Exelanation

Unbalanced right and left parentheses

Illegal character found in this statement

Compiler could not identify this statement

More than one statement with same statement number

Subscripted variable did not appear in a DIMENSION statement

Statement too long to process

Floating -point operand should have been fixed -point

Undefined statement number

Too many numbered statements in this program

Too many parentheses in this statement

Too many statements have been referenced before they appear in
the program

DEFINE statement was proceeded by some executable statement

Statement does not begin with a space, tab, C, or number

Debugging Aid (Symbolprint) -- Symbolprint is a program which may be used with the

FORTRAN compiler. Its purpose is to help the user create and debug his FORTRAN programs by providing certain information about the compiler-generated interpretive code. Symbolprint may be used
only immediately after a program has been compiled by using the Disk/DECtape FORTRAN compiler.
Symbolprint provides the following information:
a.

The limits of the interpretive code.

A list of variable names and their corresponding locations (the symbol table),

A list of statement numbers and their corresponding locations (the statement number table),

Symbolprint is loaded into core from punched paper tape and may be saved on the system device approximately as shown below (see Paragraph 2.5) •
• LOAD J
*IN-R: J

-*--

*OPT-l J
*ST- J
t-t-:SAVE STBL!600-777;600 J.

(See Appendix E.)

When in core, Symbolprint occupies locations 600-m with its starting address at location
600.

3-21

When symbolprint is called into core, it types the interpretive code limits, symbol table,
statement number table, carriage return/line feed, andt. At this point the user may execute his program by typing tP, or he may return to Monitor by typing tC.
In the following example, a program named SRC is compiled with no output specified. Symbolprint is then used as shown above •
• FORT J
*OUT- J

*
-*-

*IN-S:SRC J

~STBLJ
6154 7565
N 7576
I 7575
X 7571
Y 7566
0100 6033
0010 6060
0102 6066
0020 6145
0030 6147

(tc typed here)

(Symbol Table)

(Statement Number Table)

l<tc>
In the example above, location 6154 is the highest location used for interpretive code and location 7565
is the lowest location used for data, indicating that the part of core between 6145 and 7565 is unused.

Interpretive code starts at location 600 if a DEFINE statement appears in the program; otherwise, the
code starts at location 5200.
3.4.2

Operating System
The FORTRAN operating system consists of a loader (FOSL) and the interpreter and arithmetic

subroutine package (. OS.). This version of FOSL differs from the paper tape FORTRAN operating system in the following ways.
a. It will load and execute programs which have been compiled and saved on the system
device or programs which have been compiled on paper tape.
b. FOSL may be called directly by the compiler when a program has been compiled and
saved on the system device. This is referred to as compile -and -go mode.
c. FOSL is able to recognize READ and WRlrE statements which may read and write da,ta in
USA SCII format on either the low-speed paper tape reader/punch, the high-speed paper tape reader/
punch, or the system device.
d. The execution of a FORTRAN program may be interrupted by the user at any time by
typing tCi control will be retumed to Monitor.

3-22

3.4.2.1

Loading the FORTRAN Operating System -- To load the operating system, the following

steps are performed.
a. Load the operating system loader (FOSL) using Loader in one pass and save it on the system device as shown in Appendix E.
b. Load the operating system interpretive and arithmetic package (. OS.) by using Loader
in one pass and save it on the system device as shown in Appendix E. The FORTRAN operating system
is now loaded and ready for use. The loading process wi" generate the following printout •
• LOAD ,)
*IN-R: ,)

*OPT -1 ,J
*ST= ,)

U--

1'>77

.!..SAVE FOS L!O- ~i200 ,J
• LOAD')
*IN-R: ,J

(See Appendix E.)

-*--

*OPT -1 ,;
*ST - ,)
....."•.~
tttt
~"I j ,
..:.SAVE .OS. 10-";0 J

(See Appendix E.)

..:.

The loader occupies core locations 0-1577 with its starting address at 200. The arithmetic
and subroutine package occupies core locations 0-5177; its starting address is not specified since the
loader (not the user) calls .OS. when needed.
3.4.2.2

Operating Procedures -- The FORTRAN operating system may be transferred from the system

device into core in one of two ways:

by typing t P immediately after compiling a FORTRAN program

onto the system device, or by typing FOSl immediately after Monitor types a period.
If the operating system is called from Monitor, specify the desired input device by typing

T: J for low-speed reader, R:J for high-speed reader, or S:nameJ for system device input. FOSl wi"
type * when it recognizes a valid input device.
FOSl wi" type *OPT-. If input or output is to be to or from the system device, type S. Any
other character indicates that the system device is not to be used. However, if the S option is used,
FOSL wi" type *OUT-. The user should now specify the desired output filename (if any) by typing
S:name,; (name is the name of the file). FOSlwi" ask for the inputfilename by typing *IN-. The
user should respond with S: and the name of the file, followed by a carriage return.
If the FORTRAN program is on paper tape, Loader wi" type t when it is ready to begin
loading. When the user is ready to load his program, he types tP and the tape will begin loading.
When the FORTRAN program orfile is loaded, FOSl will type *READY, followed by a
carriage return/line feed and t. Place data tapes in the appropriate reader and type tP to begin executing the program. (If the low-speed reader is used, tum the reader ON after typing tP.)
When a STOP or END statement is executed, or when an end-of-file is read on the system
device, the operating system wi" type! and return control to-the Monitor.

3-23

The following examples show how the FORTRAN operating system may be used.
Example 1
.FOSL J
*IN-S:FBIN J

-*--

*OPT- ,)
*READY
t
(Program execution occurs here)
Example 2

1
~FOSL J
*IN-R:,R:J
*

"*tt
ERROR 01
'READY

(.tP typed here)

(Program execution begins here)
Example 3
• FORT J
*OUT-S:SMSQ,J

*IN-S:SMSQ J

T
*READY,J
1.

Compile
and

(Program execution begins here)

Example 4
.FOSL ,)
*IN-S:BIN ,)

-*--

*OPT .. S
lOOT -S:DA T2 ,J

*IN -S:DA T1 t/
~

*READY
1.
(Program execution begins here)
In example 2 a checksum error was detected on the second input tape. In this case the operator decided to attempt to execute the program in spite of the checksum error.

3-24

3.4.2.3

Operating System Diagnostics -- When an error occurs during program execution, the opera-

ting system will type ERROR followed by a two -digit error code number which will indicate the cause
of the error. Depending on the nature of the error, it may be possible to continue program execution
by typing tP or it may be necessary to return to the Monitor by typing tC.
The following is a list of the operating system error messages.
Table 3-8
Operating System Diagnostics
Error
Code

Explanation

Checksum error on FORTRAN binary input

Illegal origin or data address on FORTRAN binary input

System device input-output error 1

Hi gh - speed reader error

06
11

Illegal FORTRAN binary input device
Zero divide error

Floating-point input data conversion error

II Iega I op code

• ·Input-output error 1
System d eVlce

Non - FORMA T statement used as a FORMA T

Illegal FORMAT specification

Floating-point number larger than 2048

Square root of a negative number

Exponential negative number

Logarithm of a number less than or equal to zero

Illegal device code used in READ or WRITE statement

System device full, could not complete a WRITE statement

Stack underflow error 2
Stack overflow error 2

1 May be caused by machine malfunction or operating system error.
2 May be caused by source program or loading error; to correct, do the following
in descending order.
a.
b.
c.

Use Diagnose to determi ne where the error occurred.
Recompi Ie the source program.
Exam ine source program (in particular the ari thmeti c statements and subscripted variables).

When an error occurs, execution will stop and the operating system will wait for the user to
type t P or t C •

3-25

3.4.2.4

Debugging Aid (Diagnose) -- Diagnose is a basic system program whose purpose is to help

the user debug his FORTRAN program. It is intended to be used in conjunction with the PDP-8 4K
FORTRAN Operating System and revised FORTRAN Symbolprint. Diagnose provides the following
information.
a. If stack overflow or underflow has occurred, it will type a message indicating which of
the five run -time stacks caused the error.
b.

It will type a message indicating the contents of the current location counter (CLC).

If the counter stack is nonempty, it will type the contents of that stack.

d. If location zero is nonzero, it will type the contents of that location (minus one), indicating the point at which some FORTRAN systems error occurred.
Diagnose is loaded into core from punched paper tape and may be saved on the system device
as shown in Appendix E•
• LOAD')
*IN -R:.,I

;;tOPT -1,J

*ST- J
tt

..:..SAVE DIAGI200-1177i200,J

(See Appendix E.)

When in core, Diagnose occupies locations 200-1177 with its starting address at location 200.
Diagnose is called by typing the letters DIAG to the Monitor. It may be used any time the
FORTRAN 4K Operating system is in core. (If it is called any other time, the information typed will be
meaningless. )
The use of Diagnose is demonstrated by the example of the following test program which contains a large amount of arithmetic calculations.
Program 1:

*L
C
C
C

FORTST
PDP-8 ADVANCED SOFTWARE
FORTRAN TEST 1/2/68
DIMENSION ADIFE(6),AFAC(3),API PE(6), IMRCD(3), PP(27)
,ACPRI(3)
TYPE 1
FORMAT("PDP-8 4-K FORTRAN TEST'/,,)
ASPVA=.60
API PE(l) =12.09
APIPE(3)=6.66
API PE(4)=5.
APIPE(5)=5.0
IMRCD(l )=30
IMRCD(2) =30
ADIFE(l )=47.
ADIFE(2)=47.
ADIFE(4)=508.
AD IFE (5) =3857048.
AF=37.96

3-26

199
200
25

472
471

100
110

991
120
130
16

SC=3.1416
AMEAS=-9.02
FSUBB =:1 0.0
ASUVA=100.98
DO 200 1=1,27
READ 2,199, PP(J)
FORMAT(E)
CONTINUE
AGAST=38
INORU=2
BSPVA=(1./ASPVA)**.5
DO 550 JCB=l, INORU
AVEDE=IMRCD(JCB)
BE=API PE(JCB+3)/API PE(JCB)
IF(BE- .75)471 ,472,472
AK=.731
GO TO 16
AG=.075
DO 100 IE=l ,27
AG=AG+.025
IF(AG-BE) 100,100,110
CONTINUE
TOTA=PP(JE)
TOTB=PP(JE -1)
SC = .025 - (A G - BE)
WRITE 2,991, TOTA, TOTB, SC,AG, BE, IE
FORMAT(/" 1I ,E,E,E,E/" ",E,I)
IF(TOTA- TOTB)120, 120, 130
AK=TOTA
GO TO 16
AK=TOTB+(SC*(TOTA-TOTB»/.025
FRD=830.-5000. *BE+9000. *BE**2-4200. *BE**3+(530./APIPE(JCB)**.5)
BMEAS=AMEAS+14.4
FR=l. +«F RD/(12835. *AK»/«BMEAS*AVEDE)** .5»
XSUB2 =AVEDE/(27 .7*BMEAS)
YTTA=(XSUB2+1. )**.5
YTTB=.35*BE**4~+41.

110

991
120
130
16

YTTC=XSUB2/(1 ~3*YTTA)
YSUB2 =YTTA- YTTB*YTTC
ACPRI(JCB)=YSUB2*FR*1.0177*FSUBB
TOTA+PP(JE)
TOTB=PP(JE -1)
SC =.025 - (A G - BE}
WRITE 2,991, TOTA,TOTB, SC,AG,BE, IE
FORMAT(/ll",E,E,E,E/" ",E,I)
IF(TOTA=TOTB)120,120,130
AK=TOTA
GO TO 16
AK=TOTB+(SC*(TOTA-TOTB»/.025
FRD=830.-5000. *BE+9000. *BE**2 -4200. *BE**3+(530./APIPE(JCB)** .5)
BMEAS=AMEAS+14.4
FR=l. +«FRD/(l2835. *AK»/«BMEAS*AVEDE)**. 5»
XSUB2 =AVEDE/f27 .7*BMEAS)
YTTA=(t(SUB2+1 .}**.5
YTTB=.35*BE**4.+41.
YTTC=XSUB2/(1.3*YTTA)
YSUB2 =YTTA - YTTB *YTTC
ACPRI(JCB)=YSUB2*FR*1.0177*FSUBB
AFAC(JCB)=ADIFE(JCB)*BSPVA

3-27

992
550

38
14
993

WRITE 2,992,AK,FRD ,AMEAS,BMEAS,FR,XSUB2, YTTA, YTTB,'
YTTC, YSUB2,ACPRI(JCB),JCB
FORMAT(/" 2",E,E,E,E)
CONTINUE
AFTF=(520./(460.+AGAST»** .5
AFPV=(1. +(ASUVA *AMEAS)/((AGAST+460.)**3.825»**.5
FLOW =0
RATE=O
DO 38 l=l,INORU
AMWP=(ADIFE{1)*AMEAS)**.5/1000.
RA TE=RA TE+ACPRI(I)
FLOW =F LOW +AFTF*(AFAC(J)*AFPV*AMWP)
CONTINUE
WRITE 2, 993,AFTF ,AFPV,AMWP, FLOW,RA TE
TYPE 14, FLOW , RATE
FORMA T(E, Ej)
STOP
FORMA T(/E, E, E, E)
END

• STBL
6360
ADIF
AFAC
APIP
IMRC
PP
ACPR
ASPV
AF
SC
AMEA
FSUB
ASUV

I
AGAS
INOR
BSPV
JCB
AVED
BE
AK
AG
IE
TOTA
TOTB
FRD
BMEA
FR
XSUB
YTTA
YTTB
YTTC
YSUB
AFTF
AFPV
FLOW
RATE
AMWP

6756
7555
7544
7522
7517
7376
7365
7362
7310
7302
7274
7266
7260
7254
7246
7244
7240
7231
7225
7222
7213
7205
7201
7171
7166
7153
7124
7116
7102
7074
7063
7047
7041
7032
7016
6777
6773
6766
3-28

0001
0199
0200
0025
0472
0471
0100
0110
0991
0120
0130
0016
0992
0550
0038
0014
0993

5203

5411
5414
5426
5507
5515
5547
5550
5615
5650
5656
5676
6147
6162
6323
6342
6350

i
CI)

..Q

~
s-

CI)

..Q

cCI)

E
CI)

Example 1(a)
t

*READY
t

PDP-8 4-K FORTRAN TEST
0.255323E+l
-0. 825572E+1

!
.DIAG
CURRENT LOCATION COUNTER AT 6347
Example 1(b)

.FOSL
*IN-S:BIN

*READY
t

PDP-8 4-K FORTRAN TEST
ERROR 05
.DIAG

(tC typed here)

CURRENT LOCATION COUNTER AT 5407
Example 1(c)

.FOSL
*IN-S:BIN

*READY
t

PDP-8 4-K FORTRAN TEST

(tC typed here)

.DIAG
CURRENT LOCATION COUNTER AT 4404
COUNTER STACK •••
4733
4716
4673
6024

3-29

In example 1(a), the program was run to completion after which Diagnose was called.
Diagnose indicated that the current location counter contained 6347. By referring to the statement
number table (top of page 3-29, we can see that the CLC was pointing to an address just above statement 993 (address 6350), verifying that the program terminated normally at that point.
In example 1(b), program execution was attempted without paper tape in the high-speed
reader. After observing the error diagnostic 05, Diagnose was called, indicating that CLC=5407.
Again referring to the statement number table, we note that the address 5407 must refer to a statement
just before statement number 199 which is indeed the READ statement at which the error occurred.
In example l(c), program execution was arbitrarily stopped when the user typed tC. It
should be noted that in this case the CLC contained a 4404 which is outside the user's interpretive code
area. In such cases it is necessary to refer to the counter stack in order to determine where the program interruption occurred. The last address on the counter stack points to location 6024, and by
again referring to the statement number table we can determine that the program was interrupted at
some point between statements 16 and 992.
Program 2 is a FORTRAN program in which a missing operator appears on the 6th line. When
program execution is attempted a stack overflow (error n) occurs. Diagnose indicates that the operand
stack has overflowed, which suggests some noncompiler detected error in the source program. By referring to the statement number ta9le, which is typed aftelWards, we note that the CLC points just
before statement 10, which happens to be the source of the error. It should be pointed out, however,
that when stack overflow or underflow occurs t:'e CLC will not always point to the source of the error.
It may be necessary to examine the entire program for errors of this type.
Program 2:
.EDIT
*OUT-S:SRC
*
*IN*
*OPT-B
*1
C

10
20

FORTRAN TEST
B=l
C=2
0=3
DO 10 1=1,160
A=B(C+D)
CONTINUE
TYPE 20, A
FORMAT(E)
STOP
END

*E
• FORT
*OUT-S:BIN
*
*IN-S:SRC

3-30

*t
*READY
t

ERROR 77
(tC typed here)
.DIAG
OPERAND STACK OVERflOW
CURRENT LOCATION COUNTER AT 5231
• FORT
*OUT-

*IN-S:SRC

*t
(tC typed here)
.STBl
5251

7555

B
C
D
I
A

7574
7570
7564
7562
7555

0010
0020

5237
5244

When Diagnose finishes typing the appropriate information control returns to the Monitor
since it is impossible to resume FORTRAN program execution.
3.4.3

Examples
• lOADJ
*IN-R:J

-*-

*OPT-1J
*ST - ,J
tt

:sAVE FORTlO-lmi200,J
• lOAD,J
*IN-R: J

*OPT-2 J

*ST=J
t tt t

• SAVE .FT.1200-7377iO,J
• lOADJ
*IN-R:J

-*-

*OPT-1 J

*ST-,J

-t-t-

• ~l

\5}·

.!..SAVE FOSL!0-..-i200J

Call Loader
Input to be from high -speed reader
Input device is valid
One -pass load
Return to Monitor after loading
Loader-driver is loaded
and saved on the system device
Call Loader
Input to be from high -speed reader
Input device is valid
Two-pass load
Return to Monitor after loading
Compiler is loaded
and saved on the system device
Call Loader
Input to be from high -speed reader
Input device is valid
One-pass load
Return to Monitor after loading
Operating system loader is loaded
and saved on the system device

3-31

• LOAD,J
*IN-R:,J

-*-

*OPT -1,J
"'ST- J
tt

:-SAVE • OS. !0-4777;0,J
• LOAD l
*IN-R: ,J

*OPT-l,J
*.ST= ,J
tt

..!..SAVE STBL!600-m;600J
.EDIT J
*OUT - S:FORT J

*IN-R:'

-*-

*OPT-BJ

Call Loader
Input to be from high -speed reader
Input device is valid
One-pass load
Retum to Monitor after loading
Interpretive and arithmetic package is loaded
and saved on the system device
Ca" Loader
Input to be from high -speed reader
Input device is valid
One-pass load
Retum to Monitor after loading
Symbol print is loaded
and saved on the system device
Ca" Editor
Output to be on system device
Output device is valid
Input to be from high -speed reader
Input device is valid
Leave blanks (spaces) unchanged
Write the program on the system device
then write an end-of-file

I < tC>J

Call FORTRAN compiler
FORTRAN binary output to be on system device
Output device is valid
USA ASCII input to be from system device
Input device is valid
Compilation is finished, return to Monitor

..!..STBL ,J

Call FORTRAN Symbol print

• FORT J
*OUT - S:FORT J

*IN-S:FORT J

-*-

6177

7565

M
A
B
ANS

7576
7573
7570
7565

0001
0002
0003
0004
0005
0006
0009
0100
0200
0300
0400
0500
1000
2000
3000
4000
1500
0008
0007

5200
5257
5413
5570
5717
5754
5760
5763
5766
5771
5774
5777
6027
6040
6051
6062
6071
6077
6123

Core between 6200 and 7564 is unused

Symbol table (typed by Symbolprint)

Statement number table (typed by Symbolprint)

3-32

Symbolprint is finished, load operating system
and interpretive code
Operating system and interpretive code are loaded
Execute the program

*READY J
1.
THIS IS A DEMONSTRA TION OF PDP FORTRAN.
THIS PROGRAM WAS COMPILED IN ONE PASS
.FOSL J
*IN-S:FORT J

(tC typed here)

Call operating system and loader
FORTRAN binary input is on system device
Input device is valid
No input or output to be done on system device
during program execution
Operating system and interpretive code have been
loaded
Begin program execution

-*--

*OPT- J
*READY J
1.

THIS IS A DEMONSTRA TION OF PDP FORT
.FORTJ
*OUT - S:FORT J

(tC typed here)

Call FORTRAN compiler
Output to be on the system device
Output device is valid
Input to be from the system device
Input device is valid
Compilation is finished, loading operating system
and interpretive code
Operating system and interpretive code are loaded
Begin program execution

*IN-S:FORTJ

-*-t

*READY J

.!.
THIS IS A DEMONSTRATION OF

3.5

(tC typed here)

DDT-D
DDT-D (~namic Qebugging .!echnique for the Qisk/DECtape System) is used for on-line

checking, testing, and altering object programs by typing from the teleprinter keyboard. When debugging on-line, the user checks his program at the computer, controlling its execution, and making
corrections or changes to his program while it is running on the computer.
When using DDT-D, the user should have a listing of his program and its symbols so that he
can update the program listing as corrections and changes are made to his program. The user may refer
to variables and tags by their symbolic names or by their octal values.
DDT -D operates as described in DDT Programming Manual, DDT -8 (Doc. No. DEC-OSCDDA-D), except where that manual differs-from this one, in which case this manual has precedence.
DDT -D can be considered as being in three sections.
a.

SeU"'eHF'IOilutdl? ;o<5Cuj:mrr.'aQlg:h'l,cati.om499 .7::am:,t..

DDT Proper

tlu~,Jhr,e~J~r;~~s,

Driver

Resident in core with its origin set above DDT proper
(above 4577); itisa two-page program plusa one-page
once -only program, and it contains breakpoint insertion
and removal logic, overlay routines, continuation iteration
count a",d control, and breakpoint list.

f\ S>(1. Vi'" :u: -It
1..../

<-......I

C C)'{t::, :
3-33

User Core Image File

Occupies same storage area as DDT proper and is used for
swapping DDT proper and the user program to and from the
system device.

DDT -0 is an expanded version of DDT -8 with the following exceptions.
a.

Three breakpoints (as opposed to only one in DDT -8)

No punching (program may be output on the system device)

No switch options (user direction is via keyboard)

No hal ts (continues when user types t P)

Variations in commands 1 follows.

a•

[ 0, [S , [Y, [L, [M

Are temporary modifications to their respective constants;
are reset at every entrance to DDT -0 from a [G or [C

Continue (Monitor types t to indicate that it is waiting
for tP)

Restore user core image and return to Monitor

n[ Bk

Set breakpoint; where n is the address of the break, [B is
the breakpoint command, and k is 1, 2, or 3
NOTE
If user tries to set two breakpoints at the
same address, a ? is typed and no action
occurs.

n[B, [T, a;b[P, [E

Have been removed

Is switch independent

The following subroutines have been added.
a.

ADDCHK

Finds word to be examined and puts it in WORD 2; remembers if
last virtual word referenced was in same buffer as present virtual
word and reads only if required.

ADDMOD

Updates real or virtual core.

DDTB

Updates symbol table pointer, gets value of breakpoint and its
contents, types breakpoint number and a - (hyphen) if a breakpoint,
and goes to TRAP or types nothing and goes to START if breakpoint
number = O.

STOSYM

Updates DDT proper symbol area (DDT proper must be on unprotected
disk).

READS
and
SYMIO

Input-output routines for disk; a failure in either types Sand 90es
to start of DDT.

1 The ALT MODE key precedes each command character and is echoed as [.

3-34

The following subroutines have been modified as indicated.
a.

REDTAB

Assumes user wants to add to existing symbol table; user must type
[X to clear the symbol table.

FINIS

Does not halt, instead, it waits for the user to type tP.

CHANGE

Allows lookup of values to change limit of search and search mask.

TODDT

Handles breakpoint insertion; transferred to DDT driver.

TRAP

Breakpoint handler; transferred to DDT driver.

The following subroutines have been removed.
a.

PUNWOR

FSTPUN

FUN

PUNCHK

PUNLDR

WHICH

CHKSUM

From the teleprinter keyboard, the user can automatically stop his program at up to three
strategic points by setting breakpoints, which may be set before the debugging run is started or during
another breakpoint stop. To set a breakpoint, the user types the absolute address or symbolic tag of the
location where he wants his program to stop, the ALT MODE key, the 'B key, and then the breakpoint
number. For example,

3400[B1

(absolute address, ALT MODE, B, 1)

HERE[ B2

(symbolic tag, ALIMODE, B 2)

Locations 3, 4, and 5 on page zero are used as the breakpoint locations.

The user may,

however, reset the breakpoint locations to any three contiguous locations on page zero by setting
BRKCEL=n, where n is the lowest of the three locations desired. When the user sets his breakpoints,
DDT-D remembers the locations set with BRKCEL=n.
The following symbols are the address tags of certain regi sters in DDT -D whose contents are
avai lable to the user.
a.

b. Y

Accumulator storage (at breakpoints)
link storage (at breakpoints)

Mask used in search

Lower limit of se"arch

Upper limit of search

Table 3-9 lists the DDT-D commands available to the user.

3-35

Table 3-9
DDT -0 Commands
Action

Character
(space)

Separation character

Arithmetic plus
Arithmetic minus

3.5.1

Location examination character; when it follows the
address of a location, it causes the contents of that
location to be printed

,J (carriage return)

Make modifications, if any

t (line feed)

Make modifications, if any, and print the contents of
the next sequential location

Type last quantity as an octal integer

• (period)

Current location

.... (left arrow)

Delete the line currently being typed

[S
[0

Sets DDT -0 to type out in symbolic mode
Sets DDT -0 to type out in octal mode

n[W

Word search for all occurrences masked with C([M) of
the expression n

k[ Bn

Insert breakpoint n at location k (n = 1, 2, or 3)

[Bn

Remove breakpoint n (n =1, 2, or 3)

nrC

Continue n times automatically; if n is absent, it is
assumed to be 1

k[G

Go to location k

Append symbol table into external symbol table or define
symbols on line

Loading and Saving
DDT-D is loaded into core fram punched paper tape. The tape is in two sections. The first

section contains DDT proper which loads in one pass, occupies core locations 200-45n (Appendix E)
and uses'ocati

0) as the breakpoint 10cations1. After loading DDT proper, the

user should reserve on the system device a user core image file name. SYM, which should also be
assigned to core locations 200-4577. 1
The next section of DDT (the driver) loads in two passes and occupies two pages in core with
its origin anywhere above DDT proper, that is, anywhere above location 45n. The driver is resident
in core. For setup, it uses five more pages:

one for once -only code pi us four for Command Decoder.

Command Decoder expects two inputs to be assigned as files to be used by the driver. These files are
assigned only once unless the system is changed or destroyed, in which case the user must reassign these
two files.
1 • SYM is used also by PAL-D to store ,additional symbol table entries.

v4ed.
3-36

The sections of DDT are loaded and saved as described below.
• LOADJ
*IN-R:J

-*--

*OPT-1 J
*ST= ,J
tt
ll'5 Tl
:SAVE .DDT:200-~0,J
~SAVE • SYM:200-4577iO,J

• LOAD,J
*IN-R:,J

-*--

*OPT-2 J
*ST -7000J
t tt t

0 '5(~' I~':

*IN-S:< .DDT> ,S:< ......>,J
*IN-S:.DDT,S:.SYM ,J

*
~SAVE DDT!7200-7577i7200 ,J

Call loader using Monitor
Input to be from high -speed reader
Loader found input device valid
DDT proper loads in one pass
Return to Monitor after loading
DDT proper is loaded
(See Appendix E.)
Saved as a user program
(See Appendix E.)
User core image file also
saved as a user program
Call loader using Monitor
Input to be from high -speed reader
Loader found input device valid
Driver loads in two passes
Transfer to once-only code after loading
Driver is loaded
Assign 2 input files for use by
driver
(See Appendix E.)
Inputs to be from DDT proper and user
core image files
loader found input files valid (an
asterisk for each valid file (device)
Saved as a system program
(See Appendix E.)

-'-

The error message DDT? is typed whenever an error is encountered while loading DDT -D.
Errors may be caused by the following.

3.5.2

User file too large

System devi ce read error

c•

No Command Decoder

Operating Procedures
DDT -D is now saved on the system device. The user must now load into core the program to

be debugged. This is done as described in Paragraph 2.5.
When the program to be debugged is in core the user types DDT. in response to Monitor's
period as shown below.
.DDT
The user may now use DDT -D in debugging this program, directing execution and making
modifications to his program as described above and in the DDT -8 programming manual.
A brief example of using DDT -D is shown in Paragraph 3.5.3.
3.5.3

Example
• LOADJ
*IN-R: ,J

-*--

*OPT -1,J
ST- J

Ca II loader
Input to be from high -speed reader
Loader found input device valid
One -pass load
Return to Monitor after loading

3-37

7S'AVE • DDT:200-4577; 0 J
:SAVE • SYM:200 -4577; 0 J
:lOADJ
*IN-R:,}

*OPT-2,}
ST-7000J
..1..U.t

~S:< .DDT>,S:< .SYM>J

*IN-S:.DDT,S:.SYM J

:!!.
:!!.

.:.,SAVE DDT !72oo-7577;72oo J
.DDT.I
3400/AND 0007 lAC,}
340l/AND JMP 3400.1
34oo[ B1.J
3400 [ G.I
1 - 3400 )0000
[C.I
1 - 3400 )000 1
700[C'}
1 -3400)0701

DDT proper is loaded
DDT proper is saved on disk
(See Appendix E.)
User code image file also saved
Ca.II loader
Input to be from high -speed reader
loader found input device valid
Two-pass load
Transfer to once -only code after loading
Driver is loaded
logder expects 2 input files for use by driver
Inputs from DDT proper and user code image file
loader found both input files valid
Driver is saved on disk
(See Appendix E.)
Call DDT using Monitor
Examine contents of location
3400 and 3401
Set breakpoint No.1 at location 3400
Start execution at location 3400
location 3400 contains 0000
Continue
location 3400 now contains 0001
Pass through location 3400 700 times
location 3400 now contains 0701
t C was typed here

3-38

APPENDIX A
SYSTEM GENERATION

This appendix describes the creation of a Disk/DECtape System (Disk/DECtape Monitor and
system programs) on an empty disk or DECtape (if DECtape, it must have timing and mark tracks previously
written on it).
The steps involved in system generation are as follows.

A.1

Toggling in the Readin Mode (RIM) Loader.

Loading the Binary (BIN) Loader

Loading and executing Disk/DECtape System Builder to create Monitor.

Loading and saving any system programs.

TOGGLING IN THE READIN MODE (RIM) LOADER
The Readin Mode (RIM) Loader is a short program which loads any program in RIM format on

paper tape into core. Although the RIM Loader has various uses, its sole purpose in the System Building
process is to load the Binary Loader.
There are two versions of the RIM Loader, one for lociding programs from the high -speed paper
tape reader and the other for loading from the Teletype paper tape reader.
Hi gh - Speed Reader

Teletype Reader

Location

Instruction

Location

Instruction

7756

6014

7756

6032

7757

6011

7757

6031

7760

5357

7760

5357

7761

6016

7761

6036

7762

7106

7762

7106

7763

7006

7763

7006

7764

7510

7764

7510

7765

5374

7765

5357

7766

7006

7766

7006

7767

6011

7767

6031

7770

5367

7770

5367

7771

6016

7771

6034

7772

7420

7773

3776

7774

3376

m2
m3
m4

7775

5357

7775

5356

7776

0000

7776

0000

A-1

3776
3376

A detailed description of the toggling and checking procedures for the RIM Loader can be
found in the PDP-8 Console Manual (Doc. No. DEC-08-NGCA-D). Acomplete discussion of the
RIM Loader is contained in the PDP-8 Readin Mode Loader Program writeup (Doc. No. Digital-8-1-U).
A.2

LOADING THE BINARY (BIN) LOADER
The Binary (BIN) Loader loads any program in binary format on paper tape into core. Its pur-

pose in the System Building process is to load the Disk/DECtape System Builder. The procedure for
loading BIN is as follows.
a.

Check that the RIM Loader is in core.

b. Place the paper tape containing BIN in the paper tape reader (high-speed or Teletype,
according to version of RIM).
c.

If Teletype reader is to be used, turn it on.

Place the address 7756 into the SWITCH REGISTER and press LOAD ADD.

e. Press START. Tape should begin reading (if it does not, check that the SING INST and
SING STEP switches are down and that the reader is on line). (Note: The Teletype reader is always
on line.) If the Teletype begins to print, flip Teletype switch from LOCAL to LINE and back up the
tape to the leader/trailer.
f. After paper tape reads in, wait until only bit 0 of the accumulator is on. Press STOP
on console. If the high-speed reader is used, a 7402 (HLT) appears in the accumulator, and the tape
stops over the leader/trailer (200 code).
A detailed description of BIN and its use can be found in the PDP-8 Console Manual and PDP-8
Binary Loader Program writeup (Doc. No. Digital-8-2-U).
-A.3

LOADING AND EXECUTING DISK/DECTAPE SYSTEM BUILDER
Next, the Disk/DECtape System Builder program, in binary format on paper tape, is loaded

by the Binary Loader. Loading procedures' are as follows.
a. Place the address 7777 (starting address of BIN) into the SWITCH REGISTER. Press
LOAD ADD.
b. If the high-speed paper tape reader is to be used, put down (or set to 0) bit 0 of the
SWITCH REGISTER, place the System Builder tape in the reader, and turn the reader on.
If the Teletype reader is to be used, leave up bit 0 of the SWITCH REGISTER, place the
System Builder tape in the reader, put the reader on line, and pr~ss reader START.
c.

Press START on the console. Tape should read in.

d. When tape has been read, the accumulator should contain all zeroes (if not, the program has loaded incorrectly; begin the loading procedure from the beginning).
e. Turn off WRITE PROTECT on the disk (if present). Otherwise, mount a DECtape reel on
one of your DECtape units, set the unit selector to 8, and set the WRITE switch to WRITE.
f.
To begin System Builder execution, place the address 0200 into the SWITCH REGISTER,
press LOAD ADD, and then START.
g. As the following questions are typed out, answer them according to your machine
configuration.

A-2

*TYPE SIZE OF CORE (IN K).,
*8J
*HIGH SPEED PAPER TAPE?
*YES .,
*PDP-8/S?
*NOJ
*DISC?
*YES J
*TYPE NUMBER OF DISC UNITS
*1 .,
*TAPE?
*YES ,J

•

User enters core size of his machine (4,8, 12, 16,
20,24,28, or 32).
User answers YES or NO.
User answers YES or NO.
User answers YES or NO.
User types number of disk units on his machine.
User types YES if he has DECtape, NO if he does
not
,Q
lale,..:r
",illols
",,*._10
Monitor creation is~ completed, the resident
portion is moved to the appropriate core area
(7600 through 7777), and the nonresident portions
are written on the system device.

-..z

0:.

00.-.

NOTE

If specified as present, the disk is
automatically selected as the system
device; if not, DECtape unit 8 is
selected.
Monitor is loaded and ready.
If the response
WRITE ERROR
occurs:
".
,j .......
r .f;Ar({)If ~ .6."
a. If disk, start over at :itljlb{&j; there may be
a hardware problem.
b. If DECtape, try a new DECtape and start at
Step (e). Or, rewrite the timing and mark
tracks and start aot lilej 1 k. Otto ..

A.4

LOADING AND SAVING SYSTEM PROGRAMS
Binary Loader is one of the nonresident portions of Monitor and is used to load system and

user programs into core.

It is fully described in Chapter 2. An example follows.

• LOADJ
*IN-R:J

*OPT-l,
ST=7600 ~

• SAVE PIP! 0-3177; 1000J

Calls Bi nary Loader from the system device •
Input device is paper tape reader (high -speed reader
if specified as present at System Builder time;
otherwise Teletype reader).
Device is valid.
One-pass loading mode selected.
Return to Monitor after loading.
After each up -arrow typeout, user types t P to
continue (also must press CONTinue on console
if Teletype reader is being used).
Saves program (in this case, PIP) on system device •
Note that a ! must follow name of system program.
The SAVE command is explained in Chapter 2. The
SAVE command program is given in Appendix E.

Repeat the procedure above for each system program to be saved.
A-3

APPENDIX B
SYSTEM FORMA TS

This appendix contains the following information.
a•

System Devi ce Layouts
Di sk Storage Layout
DECtape Storage Layout
Directory Name (ON) Block Format
Storage Allocation Iv\ap (SAM) Block Format
Table of System Device and Core Capacities

Data Structure
Source File (ASCII)
Binary File (BINARY, FTC BIN)
Saved Files (SYS, USER)

B.l

PIP Listing of System Device Map (for Disk)

Monitor Core Usage Diagrams

SYSTEM DEVICE LAYOUTS
Figures B-1 and B-2 illustrate the layout of the system device for both disk and DECtape.

Note that, although the layouts differ in arrangement, they are logically equivalent.
A relatively sophisticated file structure is used for all automatic retrieval of storage by the
system. Two special types of blocks are required:

Directory Name (ON) Blocks, and Storage Alloca-

tion Map (SAM) Blocks.
B.1 .1

Directory Name (ON) Blocks
The format of a Directory Name Block is illustrated in Figure B-3. Each file has an entry

in one of the three DN blocks on the system device.
DN1 - Contains entries for internal file numbers 01 through 318 (25 10 ) and a link to DN 2 •
DN2 - Contains entries for internal file numbers 32 through 628 (50 10 ) and a link to DN 3 •
DN3 - Contains entries for internal file numbers 63 through 778 (63 10 ) and an end -of-chain
link of O.
Thus, the system device can contain up to 63 files. Each file entry contains the filename, start address,
entry point address, file type, and an internal file number (l through 77 8). When a file is to be added
on the system device, an entry fqr the file is created in the first open entry slot found in the ON blocks.
When a file is deleted, its ON entry is cleared and the slot is made available for some other file.

B-1

BLOCK
0

BLOCK
MONITOR (l ST PAGE OF SAVE)

MONITOR (START)

KUP - SEE PI

SAM

CKUP - SEE PI

MONITOR (2ND PAGE OF CALL)

MONITOR (3RD PAGE OF SAVE)

MONITOR (2ND PAGE OF SAVE)

MONITOR (1 ST PAGE OF CALL)

MONITOR (4TH PAGE OF .SAVE)

LOADER

COMMAND DECODER

401

SECOND DISK (OPTIONAL)

1001

THIRD DISK (OPTIONAL)

176
1401

177
200
201
202

373

SCRA TCH BLOCK

374

SCRATCH BLOCK

375

SCRATCH BLOCK

FOURTH DISK (OPTIONAL)

DN = Directory Name Block
SAM = Storage Allocation Map Block

376

377

AREA AVAILABLE FOR
SAVING CORE IMAGES

FIRST DISK

Figure B-1

Disk Storage layout
B-2

BLOCK
0

MONITOR HEAD
MONITOR (1 ST PAGE OF SAVE)

MONITOR (START)

SAM

SCRA TCH BLOCK

MONITOR (2ND PAGE OF CALL)

MONITOR (3RD PAGE OF SAVE)

MONITOR (2ND PAGE OF SAVE)

MONITOR 1ST PAGE OF CALL)

MONITOR (4TH PAGE OF SAVE)

LOADER

COMMAND DECODER

177

DNI (USER)

DN = Directory Name Block
SAM = Storage Allocation Map Block

AREA AVAI LAB lE
FOR SA VI N G CORE
IMAGES

200
201

DN2 (USER)

202

SAM2

203

SAM3 (USER)

204
205
206
207

2701 8

Figure B-2

DECtape Storage Layout

B-3

"""

BLOCK NUMBER OF FIRST SCRATCH BLOCK
(DISK = 0373; DECTAPE = 0005)

) 1ST ON BLOCK ONLY; OTHER
BLOCKS CONTA IN ZEROES IN
THESE WORDS

2-DIGIT VERSION NUMBER
BLOCK NUMBER OF FIRST SAM BLOCK (0200)
~~

25 10
ENTR IES
PER ON

ON ENTRY FOR FIRST FILE
(INTERNAL FILE NUMBER = 01)
ON ENTRY FOR SECOND FILE
(INTERNAL FILE NUMBER = 02)

ON ENTRY FOR THIRD FILE
(INTERNAL FILE NuMBER = 03)

i
I

ON ENTRY FOR TWENTY-FIFTH FILE
(INTERNAL FILE NUMBER = 31 8)
\~

LINK

t;nk ON
10

2 (files 32
through 62 8)

FIRST DIRECTORY NAME (ON) BLOCK

ON
ENTRY
FORMAT

}N= 4-CHARACTER
FILENAME

START

ADDRESS

ENTRY

POINT

INTERNAL FILE
NUMBER

"--y.

I
..l.

EXTENDED MEMORY BITS

1 -- SYSTEM PROGRAM

PROGRAM TYPE
00 = ASCII
01 = BINARY

10 = FTC BIN
11 = SYS OR USER SAVE FIL.E

Figure B-3

Directory Name (ON) Block Format

B-4

B.1.2

Storage Allocation Map (SAM) Blocks
SAM blocks contain a record of which files are occupying which blocks on the system device.

Each SAM block contains a record of a 3778-block area. (See Figure B-4.)
SAM 1 contains the map for blocks 0 through 3778 and a link to SAM2 •
SAM2 contains the map for blocks 400 through

m 8 and a link to SAM3 •

SAM3 contains the map for blocks 1000 through 13778 and a link to SAM 4 •
SAM4 contains the map for blocks 1400 through 1m8 and either an end-of-chain link of

o (if disk) or a link to SAM5 (if OECtape).

The next two SAM blocks are present only if a OECtape is the system device.
SAM5 contains the map for blocks 2000 th rough 23778 and a link to SAM 6 •
SAM6 contains the map for blocks 2400 through 2701 8 and an end-of-chain link of O.
On disk, one SAM block is present for each disk unit (up to four allowed) and each SAM
block resides on the disk which it maps (SAM 1 on the first disk, SAM2 on the second disk, etc.).
When a file is to be added, a search is made through the SAM blocks for an entry containing 0 (block
is unoccupied), the internal file number of the file is placed in that entry (and in as many other unoccupied entries as are needed for the file), and the storage block linking is adjusted. When a file is
deleted, all SAM block entries containing the file's internal file number are set to O. The block number of the beginning block of the SAM chain (200) is stored in the third word of the first ON block.

B-5

SPECIAL INTERNAL FILE NUMBERS:

01 = ALL MONITOR, DN., SAM,
AND SCRATCH BLOCKS
04 = LOADER BLOCKS
05 = COMMAND DECODER BLOCKS

WORD 0

f 200

fOOO

WORD 1

f 201

fOOl

WORD 2

f 202

f002

WORD 3

f 203

f003

WORD 4

f 204

fOO4

WORD 5

f 205

f005

WORD 6

f 206

f006

WORD 7

f 207

WORD 8

f 210

~
V

nnn

f007
f 010

-;::::::::-

f370

f167
f 170

WORD 122

f371

f 171

WORD 123

f372

fl72

WORD 124

f373

f173

WORD 125

f374

f174

WORD 126

f375

f175

WORD 127

f376

f176

WORD 128 10

f377

fl77
LINK

r--

[LINK TO SAM2
l(BLOCKS 400-777)

STORAGE ALLOCATION MAP (SAM)

EXAMPLE
FILE #1 - BLOCKS 0, 1, 2

FILE #3 - BLOCKS 5, 6, 11

FILE #4 - BLOCK 10

FILE #13 - BLOCKS 201,
202, 206, 207

FILE #15 - BLOCKS 200,
203, 205, 210
UNUSED - BLOCKS 3, 4, 7 ,
204, 211

Figure B-4

o
2

12
Storage Allocation Map (SAM) Block Format

B-6

internal file
number of fi Ie
occupying block
hnn (0 =
unoccupied)

Table B-1
System Device and Core Capacities

B.2

Highest Page (Block)
Number (1st Page == 0)

Unit

Words

1 DISK

32,768

255 10

(375 8 )

2 DISKS

65,536

51110

(773 8 )

3 DISKS

98,304

767 10

(1377 S)

4 DISKS

131,072

1023 10

(1mS)

1 DECTAPE

667,520

5215 10

(2701 S)

4K CORE

4,096

31 10

(37S)

8K CORE

8,192

63 10

(n8)

12K CORE

12,288

95 10

(1378 )

16K CORE

16,384

12710

(1778 )

20K CORE

20,480

15910

(237 8 )

24K CORE

24,576

191 10

(2778 )

28K CORE

2S,672

233 10

(3378 )

32K CORE

32,768

255 10

(377 8)

DATA STRUCTURE
The data structure of each type of program file is described in the following paragraphs.

B.2.1

Source File (ASCII) Data Structure
A" characters are stored in 6-bit ASCII code, two words per three paper tape frames as

described below. A" nonprinting characters (200 through 237 and 340 through 377) have their two
most significant bits dropped and a 77 prefixed to them. (The one exception to this rule is RUBOUT,
377, which is nonexistent.) A" printing characters are trimmed to six bits, except for? (277), which
is packed as 7777.
B.2.2

Binary File (BINARY, FTC BIN) Data Structure
A" binary (BINARY) and FORTRAN binary (FTC BIN) files are stored as two words per three

paper tape frames. Frame 1 contains the rightmost eight bits of word I, frame 2 contains the rightmost
eight bits of word 2, and frame 3 contains the leftmost four bits of words 1 and 2 (the most significant
bits of frame 3 are those of word 2).

Example:
Paper tape
200
102
033

Meaning

Disk(Octal)

Disk (Binary)

5600
0502

1011 10000000
0001 01000010

Leader
ORG
Second half
of ORG word

This procedure is repeated until a trailer code is found.
B.2.3

Saved File (SYS, USER) Data Structure
Saved files are stored on the system device as an integral number of pages and each page

occupies one disk or DECtape block. Storage conventions differ between saved files o~ contiguous pages
of core and those of noncontiguous pages.
Contiguous Pages
All system device blocks contain core images (Figure 8-5). The Start Address word in the
Directory Name (ON) entry for the file is set to the starting page address.
SAVE

Block 1

Block 2

Block 3

FILC:200-600;433

Contains core
image of locations
200 through 377

}

Start Address

Entry Point

File Type/File Number

DIRECTORY NAME ENTRY

Conta i ns core
image of locatio-l'Is
400 thrQ\Jgh 577

Contains care
image of locations
600 through 777
SYSTEM DEVICE BLOCKS
Figure B-5

Filename

Contiguous-Page. Save File Format

B-8

Noncontiguous Pages
The first system device block of a saved file composed of noncontiguous pages of core contains a list of core page assignments and the core images sotred in subsequent blocks. The last entry in
this list is set to 7777 (Figure B-6). The Start Address word in the Directory Name entry for the file is
set to 7777 to indicate that the first block does not contain a core image but a page assignment listing.

SAVE

Block 1

FILN: 0,400,1000;433

0000 List of
0400 page
1000 assign7777 ments

Filename

Start Address

Entry Point

File Type;File Number

DIRECTORY NAME ENTRY

Block 2

Conta ins core
image of locations
o through 177

Block 3

Contains core
image of locations
400 through 577

Block 4

Contains cori!
image of locations
1000 through 1177

SYSTEM DEVICE BLOCKS

Figure B-6

Noncontiguous-Page Save File Format

B-9

B.3

PIP DIRECTORY LISTING

A directory listing of the system device con be obtained by running PIP (Figure B-7). A
sample output is given below .

• PIP
*OPT-L
*IN-S:
110 free blocks remain

FB=0110

80
PALO. SYS (0)
EDIT. SYS (0)
LOAD. SYS (0)
.CD •• SYS "(0)
PIP • SYS
(0)
FORT.SYS (0)
• FT •• SYS (0)
• OS •• SYS (0)
FOSL. SYS (0)
STBL. SYS (0)
• DDT. USER (0)
• USR. USER (0)

0030
0015
0003
0006
0020
0010
0035
0024
0006
0001
0022
0023

~~
I

L.
_______

Number of blocks used

'-.- - - - - - - - F i e l d number

'--------Extension name
'----Filename

Figure B-7

Sample PIP Directory Listing

B-10

B.4

MONITOR CORE USAGE DIAGRAMS
The following illustrations show Monitor usage of locations 7000 through 7777 at
a.

Monitor Time and User Time (Figure B-8)

SAVE Command Processing (Figure 8-9)

CALL Command Processing (Figure B-10)

7777

7777
SYSTEMS I/O ROUTINE
MONITOR H~AD

SYSTEMS I/O ROUTINE
MONITOR HEAD

7600

7600
MONITOR
TELETYPE SERVICE

USER AREA

7400

7400
SAVE COMMAND DECODER
AND
PAGE STACK BUILDER

USER AREA

7200

7200
7000

7000

(a) Monitor-Time Core Usage

Figure B-8

USER AREA

(b) User-Time Core Usage

Monitor-Time vs User-Time Core Usage

B-11

• SAVE filename:core-specifications, •.• ;entry-point

7777
SYSTEMS I/O

SYSTEMS I/O

MONITOR HEAD

PAGE STACK BUILT HERE

MONITOR AND TTY SERVICE ROUTINES
ARE NOW DESTROYED; VARIOUS STATUS
REGISTERS ARE HELD HERE.

7600

-----------------------------------TTY SERVICE ROUTINE
-----------------------------------7400

DIRECTORY NAME ENTRY BUILT HERE

PAGE STACK MOVED HERE

SAVE COMMAND DECODER
AND
PAGE STACK BUILDER

BUFFER FOR DN SEARCH

7200
CODE HERE IS SWAPPED OUT TO
SYSTEM. DEV ICE SCRATCH BLOC K;

DN BLOCK SEARCH AND UPDATE
ROUTINE LOADED HERE

7000
(a)

"SAVE filename:" Processing

(b) "Core-specifications, o;entry-point"
Processing

SYSTEMS I/O

MONITOR HEAD

BLOCK STACK

7777

7600
7500

------------------------------------. -------------------------------------------------------------------------- -------------------------------------PAGE STACK

PAGE STACK

7400
SAM BLOCK SEARCH AND UPDATE
ROUTINES LOADED HERE
(CREATE BLOCK STACK)

ACTUAL SAVE ROUTINE LOADED HERE
(RETURNS TO MONITOR START7600-WHEN FINISHED)

SAM BUFFER

SWAPPED-OUT CODE BROUGHT BACK

7200
7000
(c)

SAM Search

Figure B-9

(d)

Actual Save Time

Core Usage During SAVE Command Execution

B-12

. CALL filename J

. filename ,

7777
SYSTEMS I/O
MONITOR HEAD

7600
BUFFER FOR DN AND SAM BLOCKS

7400
CALL: DN AND SAM SEARCH
ROUTINES

7200

(LOCATE FILE AND DEFINE RANGE OF CALL)
X

7000
(a) "CALL filename" Processing

7777
SYSTEMS I/O
MONITOR HEAD

7600
READ ROUTINE
(PERFORMS ACTUAL CALLING IN OF FILE;
CAN DISAPPEAR AT USER TIME)

7400
CONTIGUOUS-PAGE PROGRAM:
THIS AREA IS NOT TOUCHED.

7200

NONCONTIGUOUS-PAGE PROGRAM:
SCATTER-GET READS CORE
ALLOCATION (BLK 1) INTO HERE
X

7000
(b) Actual CALL Time

Figure B-lO

Core Usage During CALL Command Execution

B-13

MaN ITOR START

CONSTRUCT
PAGE LIST

READ SAM
BLOCK

Figure B-11

Monitor FlowChart (Part 1)

B-14

SET ENTRY
POINT TO 200

AN OLD VERSION
OF THE FILE
E)(ISTS AND IS
BEING OVERWRITTEN BY
A NEW VERSION

TYPE "FUL'::

JUMP TO ENTRY
POINT ADDRESS

Figure B-11

Monitor Flow Chart (Part 2)

B-15

IF AN OLD FILE IS
BEING OVERWRITTEN
CONTINUE SEARCHING
SAMS FOR OLD FILE
NUMBER AND CHANGE
TO 0

Figure B-11

Monitor Flow Chart (Part 3)

B-16

APPENDIX C
COMMAN D DECODER

Command Decoder is a general-purpose program used by all system programs to read in and
interpret command strings entered by the user via his Teletype keyboard. Command Decoder is generated and stored on the system device by System Builder.
Command Decoder uses four pages of core (see Figure C-2) and is called in by a system program in the following way.
a. The internal file number of Command Decoder (filename = .CD.) is obtained.
b. The starting block of the Command Decoder file is obtained.
c. This block is then read into the second of the four pages to be used by Command
Decoder. Command Decoder is position-independent and can be read into any four contiguous pages
of core between locations 200 and 7577 inclusive.
d. Command Decoder is then entered by jumping to the second location of page 2 (the
first location is an error return).
C.1

LOCATIONS USED BY COMMAND DECODER
Locations 167 through 177, page 0, are used asToliows.
Table C-1
Page 0 Locations Used by Command Decoder
Location

Pur~se

167

Preloaded with 7777 if input and output filenames and extension names
are different.

170

Scratch location.

171

Scratch location.

172

Points to the first block of Command Decoder.

173

Scratch location.

174

Points to the output list. Information concerning each device request
is placed in this list by Command Decoder.

175

Contains the option bits. This location is not left in its original state
upon exit from Command Decoder

176

Scratch location.

177

Conta ins the address of the return from Command Decoder.

C.2

INPUT AND OUTPUT REQUIREMENTS FOR COMMAND DECODER
Location 174 (CDPTRP), the output list pointer, must point to a block of code, the length of

which must be 3*n+1, where n is the total number of device requests expected. For example, a program
with one output file plus three input files requires 13 locations. (See Figure C-1.)
The option bit location (175) is constructed as follows.
Bits 0 and 1

Contain output file extension code (or input, if no output is
requested) .1

Bits 2 and 3

Contain the input file extension code. 1

Bit 4

Bit 5

= Saved output file is a system program (bit 5 of word 4 in

Output file is expected {Command Decoder will type
*OUT - query (in addition to * IN-) ) .
ON entry is set to 1).

Bit 6

= Option is available (Command Decoder will type *OPT -).

Bit 7

= Saved input file is a system program (bit 5 of word 4 in
ON entry is checked for a 1).

Bits 8-11

(Total number of input files allowed) -1 .

1J0C04

'-.r---J
I
(Number of input files) -1
System/user input2

OPT - option
'----System/user output

I...---Output option

• 1
1...------ Input extension

11.-______

• 1
O utput extension

This option word must be set up by the system program before calling Command Decoder.

1Extension codes:

00 - ASCII
01 = BINARY
10 = FTC BIN
11 = Saved file (USER, SYS)

= System, 0 = User
C-2

PDP-S/I Disk Monitor System

DEC-DS-SDAA-D

July 1, 1965

The first block of the Command Decoder is read into the second of the four blocks into
wh ich it is to run. In the following examples, assume Command Decoder is to be run in locations
2000-2777; that you have already loaded FBLK with the first block number of the Command Decoder;
output list is in 3000; return is at 203 and you are looking for user file output, system file input, no
*OPT- is desired, and three input files are allowed.
Example 1:

FBLK,

TAD
DCA
TAD
DCA
TAD
DCA
TAD
DCA
CMA
DCA
JMS I
3
0
2200

*1700
(203
177
(7622
175
(3000
174
FBLK
172

/RETURN
/111 110 010 010 = BITS
/POINTER TO LIST
/BLOCK 1 OF .CD. (DISK)

167
(7642

HLT
JMP I .+1
2201

/READ
/BLOCK 1 OF COMMAND DECODER
/INTO LOCATION 2200
/LINK
/BAD READ
/ENTER .CD.

Example 2:

FBLK.

*2200
(203
TAD
177
DCA
TAD
(7622
175
DCA
(3000
TAD
174
DCA
FBLl<
TAD
172
DCA
CM
167
DCA
JMS I (7642
1003
0
2200
0
2200

/RETURN
/111 110 010 010

= BITS

/POINTER TO LIST
/BLOCK 1 OF • CD.

/READ AND RETURN THRU
/ADDRESS IN ERROR RETURN
/IF ERROR, OR ERROR RETURN
/+1 IF CORRECT RETURN
/NOTE THIS CODE IS OVER-WRITTEN

C-2a

FOR DISK OR DECTAPE:
OUTPUT
{
(OR INPUT 1
IF NO OUTPUn
INPUT 1
{
(OR INPUT 2
IF NO OUTPUT)

WORD A

UNIT
INTERNAL FILE
NUMBER
NUMBER
------0-7
6 = System Device
(
4 = Not System Dev i ce

DEVICE
CODE

WORD B

WORD A

Lo'

WORD B
FOR TELETYPE OR HIGH SPEED READER:

DEVICE
CODE

1 = Teletype
2 = Hig h Speed Reader
0= Null Device

7777
OPTION

END OF LIST
ASCII
CHARACTER

DISK OR DECTAPE (INPUT):
START BLOCK NUMBER
DISK OR DECTAPE (OUTPUT):

o
PAPER TAPE:

Figure C.,..1

Output list Produced by Command Decoder

C-3

PAGE

*IN-,*OUTTYPEOUTS

------

TYPE
__ .!!O.!!T.!.N=. _
TIME 1

CHARACTER
FETCH AND
DISPATCH

-------

PAGE

COMMAND
DECODER I NI T •

1------READ ROUTINE
FOR PAGES 1,
3, AND 4

1-------COMMA ,CARR IAGE
RETURN HANDLER

ROTATE

PAGE 3

PAGE 4

DEV I CE LOOKUP
AND VALIDITY CHK.

ERROR ROUTINE

1-------*
1--.-----1-------1-------1--------

------TYPE-OUT RTE

TYPE OUT
IF VALID

-----1/0 DEVICE

READ BLOCK 5
I NTO PAGE 2

CHECK ROUTINE
-----"--

ON CHECK

READ BLOCK 6

DECTAPE 110

ERROR DISPATCH

BLOCK 2

BLOCK

BLOCK 3

ON SEARCH
ROUTINE
f-...,.------

TIME 2

BUFFER

01 RECTORY
UPDATE

BLOCK 5

SAM BLOCK
SEARCH ROUTINE
(INPUT ONLY)

1-------TIME 3

BUFFER

READ IN BLOCK
1 I NTO PAGE 2
(OUTPUT ONL.Y)

f-------OPT-READ IN
OPTION CHAR.
f-------EXIT TO USER
BLOCK 6

Figure C-2

Command Decoder Core Usage

C-4

BLOCK 4

PAGE 2 (BLOCK 1)

PLACE "E" IN AC

PAGE 1 (BLOCK 2)

PAG E 1 (BLOCK 2)

TYPE II*OUT_II

Figure C-3

Command Decoder Flow Chart (Part 1)

C-5

(READ A CHARACTER FROM THE TELETYPE KEYBOARD)

PAGE 1
(BLOCK 2)

TYPE

PAGE 1
(BLOCK 2)

111"

Figure C-3

Command Decoder Flow Chart (Part 2)

C-6

PAGE 3
(BLOCK 3)

READ BLOCK 5
INTO PAGE

PLACE "?"
IN AC

ATTEMPT TO MAKE
NEW ON ENTRY
(PAGE 2, BLOCK 5)

Figure C-3

Command Decoder Flow Chart (Part 3)

C-7

SEARCH)

SET INTERN
FILE
NUMBER IN AC

NO (READ NEXT ON BLOCK)

Figure C-3 Command Decoder Flow Chart (Part 4)

C-8

CLEAR OUTPUT
BIT IN
LOCATION 175

PUT START
BLOCK NUMBER
IN AC

TYPE

"1'1

Figure C-3

Command Decoder Flow Chart (Part 5)

C-9

PAGE 4 (BLOCK 41

PAGE 2 (BLOCK 51

(DIRECTORY FULL)

PAGE 4 (BLOCK 41

SIMULATE JMS
DECTAPE 110

Figure C-3

Command Decoder Flow Chart (Part 6)

C-10

APPENDIX D
BINARY LOADER

Binary Loader loads binary output from Assembler into one or more fields in core in executable form.

It operates in either I-pass or 2-pass mode (all input files must be read in once for each pass).

A field bit indicator, which determines the field into which loading occurs, is initially set equal to the
field bit of the address typed in response to the ST= typeout. This indicator can be changed during
loading by the occurrence, in any input file, of a FiElD word (generated by the PAL-D pseudo-op
FIELD).
In I-pass mode, Binary loader can load core from locations 0 through 6777 in field 0 and
all of fields 1 thraugh 7. In 2-pass mode, it can load core from 0 through 7577 in field 0 and all of
fields 1 through 7. Two-pass loading, then, is required when any of the input files require that coding
be loaded into locations 7000 through 7577 in field 0; the reason for this is that Loader occupies these
positions and cannot load the information over itself. To handle this situation, 2-pass loading operates
as described in the following paragraphs.

PASS 1
All input files are read to find those partions of coding residing in the area from 7000 through
7577. Such coding is loaded into locations 6000 through 6577 instead. All other coding is bypassed.
At the end of Pass 1, the contents of locations 6000 through 6577 are written into three scratch blocks
on the system device.
PASS 2
Normal loading is performed, just as in the sing Ie pass of I-pass loading, except that coding
to be loaded in the 7000-7577 area is ignored. At the end of Pass 2, the contents of the three scratch
blocks writ,ten during Pass 1 are read into locations 7000 through 7577. A jUITlP is then made to the
ST= address.
The ST= address has a double significance.
a.

It initially sets the field bit indicator for loading 1

b. It specifies the address (either in the loaded program or Monitor) to which control is to
be transferred after loading.

iIn 8 through 32K systems it is the user1s responsibility t<;> specify existing bank settings. In 4K systems,
a 5-digit spec ification is illegal.

D-l

Examples
51=10000

Begin loading in field 1 and jump to Monitor start (7600) after
loading.

51=31015

Begin loading in field 3 and jump'to location 1015, field 3,
after loading.

51=27600

Begin loading in field 2 and jump to location 7600, field 2,
after loading.

0-2

SET UP TO INPUT
FROM SYSTEM
DEVICE

Figure D-1

Binary Loader Flow Chart (Part 1)

D-3

>----1--""" UPDATE
EXECUTE FIELD
INSTRUCTION

Figure 0-1

Binary Loader Flow Chart (Part 2)

0-4

CHECKSUM

PASS 2
(OR I-PASS)

WRITE OUT

6000-6577
ONTO SYS.
DEVICE

SET UP FIELD
INSTRUCTION

Figure 0-1

Binary Loader Flow Chart (Part 3)

0-5

APPENDIX E
SYSTEM PROGRAMS
E.1

E.2

lOADING STATISTICS
Name

Core Limits

Entry Point

Pass

PIP

0-177, 1000-3177

1000

EDIT

0-3177

2600

PALO

0-3377, 36.00-4377,
4600, 5200,
6200-6577, 7000-7577

6200

FORT

0-1777

200

.FT.

200-7377

STBl

600-777

600

FOSl

0-1577

200

.OS.

0-5177

DIAG

200-1177

200

. DDT

200-4577

.SYM

200-4577

DDT

7200-7577

7200

SAVE STATISTICS
PIP

SAVE PIPIO,l000-4777il000

EDIT

SAVE EDITlO-3177;2600

PALO

~.LO~~
... -:'~It,tl!OO.~~';'
... ··'SA)~.

i""

FORT

SAVE FORTIO-lm;200 ~...l

.FT.

SAVE . FT . 1200-7377;0

STBl

SAVE STBL!600;600

FOSl

SAVE FOSL!0-1577;200

.OS.

SAVE .OS. 10-5177;0

DIAG

SAVE DIAG 1200-1177;200

E-1

f~""~,. "', (I ,"" ~l ~ ~n j b 2, 06

.DDT

SAVE .DDTl200-4577jO

.SYM

SAVE .SYM!200-4577jO

DDT

SAVE DDT!7200-7577jO

(User may assemble anywhere above
location 4577)

E-2

July 1, 1968

PDP-8/1 Disk Monitor System
DEC-D8-SDAA-D
APPENDIX F
I/O PROGRAMMING

F.1

GENERAL

The modular concept of input-output {I/O} handling of the disk system provides for easy
maintenance and programming. The system device I/O is found in the following places (all I/O
routines must be in field 0).
a. Top page of field 0 (location 7642) which is the I/O routine used by all system programs for normal I/O. A copy of this page is on block 0 of the system device. Block 0 of each DECtape is the DECtape I/O routine.

F.2

Interrupt versions of disk and DECtape routines are found in PIP.

Paper tape I/O is handled by individual programs.

CALLING SEQUENCE FOR BASIC I/O ROUTINE

The basic I/O routine (see Para. F.1.a.) is called as shown in Figure F-1. It is called
in two ways, as determined by bit 2 of the function word.
a. Normal -- The I/O routine returns to JMS +6 (normal) or JMS +5 {error}. For
example, the following routine would read consecutive blocks from a file on the system device. The
routine is initialized by putting the first block number of the desired file into location LINK. If an
attempt is made to read past the last block of the file, an exit will be made to a routine called ENDFIL.

GETBLK,

a
TAD LINK

/GET LINK FROM LAST READ
/IS THIS END OF FILE?
/YES

SNA

JMP I (ENDFIL
DCA BLOK
Jr."S I
3

BLOK,

LINK,

(7642

/CALL DISK I/O ROUTINE
/FUNCTION - READ

BUFFAD

/BUFFER ADDRESS

JMPI (ERROR
JMP I GETBLK

/ERROR RETURN

b. Indirect -- The I/O routine returns to the 12-bit address in the error return word +1
(normal or the 12-bit address in the error (ERROR)). An example of the indirect routine is given on
page C-2a of this manual.

F-1

Call ing Sequence

Explanation

JMS I SYSIO

Location SYSIO points to I/O

FUNCT

Function word*

BLOCK

Block to he accessed

CORE

Low-order core address

LINK

Filled by WRITE, used by READ

ERROR

Error return here
Normal return here

* Function word:

Bits 0-1
Bit 2

= 0, normal return

Bits 3-5
Bits 6-8
Bits 9-11

= 1, indirect return at end of read/
write to address +1 in error
return
unit no. if DECtape
memory field
function: READ = 3; WRITE = 5

Figure F-1.

unused

Calling Sequence of System Routine

F-2

•

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PDP-8/1 DI SK MON ITOR SYSTEM

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DEC-D8-SDAA-D

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