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DEC-8E-OCASA-B-D

May 1974

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Document:	CAPS8 UG
Order Number:	DEC-8E-OCASA-B-D
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Pages:	223
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OCR Text

users manual

digital equipment corporation

DEC- 8E-OC1LSA-B-D

CASSETTE

PRO G RAM MIN G S Y S T E M
USE R 'S MAN UA L

For additional copies, order No. DEC-8E-OCASA-B-D
from Software
Distribution Center, Digital Equipment. Corporation, Maynard,
Massachusetts 01754

First Printing, March, 1973
Revised September, 1973
Printed July, 1974

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

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

The following a:re trademarks of Digital Equipment Corporation:
CDP
COMPUTER LAB
COMSYST
COMTEX
DDT
DEC
DECCOMM
DECTAPE
DIBOL

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

IND.~C

KAIO
LAB-8
LAB-8/e
LAB-K
OMNIBUS
05/8
PDP
PHA

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

CONTENTS
PAGE
CHAPTER 1 THE CASSETTE PROGRAMMING SYSTEM
1.1
1.1.1
1.1.2

INTRODUCTION TO A CASSETTE STORAGE SYSTEM
Hardware Components
Software Components

1-1
1-2
1-2

1.2
1.2.1
1.2.2

vvHAT IS A CAPS- S CASSET'I'E?
The Format of a Cassette
The sentinel File

1-2
1-4
1-4

1.3

THE SYSTEM CASSETTE

1-4

1.4

!JIOUNTING AND DISMOUNTING CASSETTES

1-5

1.5

CONCERNING EXAMPLES

1-6

CHAPTER 2 GETTING ON-LINE WITH THE CAPS_oS SYSTEM
2.1

SYSTEM PROGRAMS

2-1

2.2
2.2.1
2.2.2
2.2.3

SYSTEM CONVENTIONS
File Formats
Filenames and Extensions
Input/Output Devices

2-1
2-1
2-2
2-2

2.3

LOADING THE KEYBOARD MONITOR

2-3

2.4
2.4.1
2.4.2
2.4.3

USING THE KEYBOARD MONITOR
Making Corrections
Special Characters
I/O Designations and Specification Options

2-3
2-3
2-4
2-5

2.5
2.5.1
2.5.2
2.5.3
2.5.4
2.5.5
2.5.6
2.5.7
2.5.S

KEYBOARD MONITOR COMMANDS
Run Command
Load Conunand
DAte Conunand
DIrectory Command
DElete Conunand
Zero Conunand
REwind Command
Version Command

2-5
2-6
2-7
2-7
2-7
2-S
2-9
2-10
2-10

2.6

NOTES ON DEVICE HANDLERS

2-11

2.7

MONITOR ERROR MESSAGES

2-12

CHAPTER 3 SYMBOLIC EDITOR
3.1

INTRODUCTION

3-1

3.2
3.2.1
3.2.2
3.2.3

CALLING AND USING THE EDITOR
EDITOR Options
Input and Output Specifications
Version Numbers

3-1
3-1
3-2
3-3

iii

3.3
3.3.1

MODES OF OPERATION
Transition Between Modes

3- 4
3-4

3.4
3.4.1
3.4.2
3.4.3
3.4.4
3.4.5
3.4.6
3.4.7
3.4.8
3.4.9
3.4.11
3.4.12
3.4.13

SPECIAL CHARACTERS AND FUNCTIONS
RETURN Key
Erase (CTRL/U)
RUBOUT Key
Form Feed (CTRL/FORM)
The Current Line Counter (.)
Slash (/l
LINE FEED Key
ALT MODE Key
Right Angle Bracket (»
Left Angle Bracket «)
Equal Sign (=)
Colon (:)
Tabulation (CTRL/TAB)

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

3.5

COMMAND STRUCTURE

3-8

3.6
3.6.1
3.6.2
3.6.3

COMMAND REPERTOIRE
Input Conunands
Output Conunands
Editing Conunands

3-8
3-9
3-10
3-12

3.7

TEXT COLLECTION

3-15

3.8
3.8.1
3.8.2

CHARACTER SEARCHES
Single Character Search
Character String Search

3-16
3-16
3-17

3.9

EDITOR ERROR MESSAGES

3-21

3.10

EDITOR DEMONSTRATION RUN

3-23

3.4.1~

CHAPTER 4 SYSTEM COpy
4.1

INTRODUCTION

4-1

4.2
4.2.1
4.2.2
4.2.3

CALLING AND USING SYSTEM COpy
System Copy Options
Input and Output Specifications
System Copy Example

4-1
4-1
4-2
4-3

4.3

SYSTEM COpy ERROR MESS1~GES

4-4

CHAPTER 5 PALC ASSEMBLER
5.1

INTRODUCTION

5-1

5.2
5.2.1

CALLING AND USING PALC
PALC Options

5-1
5-5

5.3

CHARACTER SET

5-5

5.4
5.4.1
5.4.2
5.4.3
5.4.4

STATEMENTS
Labels
Instructions
Operands
Conunents

5-6
5-6
5-6
5-7
5-7

5.5
5.5.1
5.5.2
5.5.3

FORMAT EFFECTORS
Form Feed
Tabulations
Statement Terminators

5-7
5-7
5-7
5-8

5.6

NUMBERS

5-9

5.7
5.7.1
5.7.2
5.7.3
5.7.4
5.7.5
5.7.6
5.7.7
5.7.8

SYMBOLS
Permanent Symbols
User-Defined Symbols
Current Location Counter
Symbol Table
o'irect Assignment Stat~ements
Symbolic Instructions
Symbolic Operands
Internal Symbol Representation for PAGC

5-9
5-9
5-9
5-10
5-11
5-12
5-13
5-13
5-13

5.8
5.8.1
5.8.2

EXPRESSIONS
Operators
Special Characters

5-14
5-14
5-17

5.9
5.9.1
5.9.2
5.9.3
5.9.4

INSTRUCTIONS
Memory Reference Instructions
Indirect Addressing
Microinstructions
Autoindexing

5-20
5-20
5-20
5-21
5-23

PSEUDO-OPE RATORS
5.1.0
5.1.0.1
Indirect and Page Zero Addressing
Radix Control
5.1.0.2
Extended Memory
5.1.0.3
5.1.0.4
End-of-File
5.1.0.5
Resetting the Location Counter
5.1.0.6
Entering Text Strings
Suppressing the Listing
5.1.0.7
Reserving ~emory
5.1.0.8
Conditional Assembly Pseudo-Operators
5.1.0.9
Controlling Binary Output
5.1.0.1.0
Controlling Page Format
5.1.0.11
Altering the Permanent: Symbol Table
5.1.0.12

5-24
5-24
5-24
5-25
5-26
5-26
5-27
5-27
5-27
5-28
5-28
5-29
5-29

5.11

:GINK GENERATION AND STOHAGE

5-30

5.12

CODING PRACTICES

5-31

5.13
5.13.1

PROGRAM PREPARATION AND ASSEMBLER OUTPUT
Terminating Assembly

5-32
5-33

5.14

PALC ERROR CONDITIONS

5-33

CHAPTER 6 CASSETTE BASIC
6.1

INTRODUCTION

6-1

6.2

CALLING BASIC

6-1

6.3

NUMBERS

6-2

6.4

VARIABLES

6-3
v

6.5
6.5.1
6.5.2
6.5.3

ARITHMETIC OPERATIONS
Priority of Operations
Prentheses and Spaces
Relational Operators

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

6.6
6.6.1
6.6.2
6.6.3

IMMEDIATE MODE
PRINT Command
LET Command
Looping PRINT and LET Commands

6-6
6-6
6-7
6-7

6.7

EXAMPLE RUN

6-8

6.8
6.8.1
6.8.2
6.8.3
6.8.4
6.8.5
6.8.6
6.8.7
6.8.8
6.8.9
6.8.10
6.8.11
6.8.12

BASIC STATEMENTS
Statement Numbers
Commenting the Program
Terminating the Program
The Arithmetic Statement
Input/Output Statements
Creating Run-Time Input Files
Loops
Subscripted Variables
Transfer of Control Statements
Program Chaining
Subroutines
Functions

6-10
6-10
6-10
6-11
6-11
6-12
6-25
6-27
6-29
6-31
6-34
6-35
6-37

6.9
6.9.1
6.9.2
6.9.3
6.9.4
6.9.5

IMPLEMENTING A USER-CODED FUNCTION
Coding Formats
Floating-Point Format
Incorporating Subroutines with UUF
Writing the Program
Examples of User-Coded Functions

6-44
6-44
6-46
6-46
6-47
6-47

6.10
6.10.1
6.10.2

FLOATING-POINT PACKAGE
Instruction Set
Addressing

6-50
6-50
6-51

6.11
6.11.1
6.11.2
6.11.3
6.11.4
6.11.5
6.11.6
6.11.7
6.11.8

EDITING AND CONTROL COMMANDS
Erasing Characters and Lines
Listing a Program
Running a Program
Stopping a Run
Loading a User-Coded Function
Erasing a Prbgram In Memory
Renaming a Program
Saving a Program

6-52
6-52
6-53
6-54
6-54
6-55
6-55
6-55
6-56

6.12

CASSETTE BASIC ERROR MESSAGES

6-57

6.13

CASSETTE BASIC SYMBOL TABLE

6-59

CHAPTER 7

USING CAPS-8 CODT

7.1

FEATURES

7-1

7.2
7.2.1

USING CODT
Commands

7-2
7-2

7.3

ILLEGAL CHARACTERS

7.4
7.4.1
7.4.2

ADDITIONAL TECHNIQUES
TTY I/O-FLAG
Interrupt Program Debugging

7-8
7-9
7-9

7.4.3
7.4.4

Octal Dump
Indirect References

7-9
7-9

7.5

ERRORS

7-9

7.6
7.6.1
7.6.2

OPERATION AND STORAGE
Storage Requirements - CAPS-8 System
Programming Notes Summary

7-9
7-10
7-10

7.7

COMMAND SUMMARY

7-11

CHAPTER 8

CAPS-8 UTILITY PROGRAM

8.1

INTRODUCTION

8-1

8.2
8.2.1
8.2.2

CALLING AND USING THE UTILITY PROGRAM
Utility Program Options
Input and Output Specifications

8-1
8-1
8-2

8.3

UTILITY PROGRAM ERROR MESSAGES

8-2

CHAPTER 9
9.1

BOOT
OPERATING PROCEDURES

9-1

APPENDICES
A

ASCII Character Codes

A-I

Error Message and Command Summaries

B-1

PALC Permanent Symbol Table

C-l

CAPS-8 Demonstration. Run

D-l

Monitor Services

E-l

Assembly Instructions

F-l

TABLES
Table :2-1 CAPS-8 Extension Names
Table 2-2 Directory Options
Table 2-3 Keyboard Monitor Error Messages
Table 3-1 EDITOR Options
Table 3-2 Command Format
Table 3-3 Input Commands
Table 3-4 List Commands
Table 3-5 Text Transfer Commands
Table 3-6 Editing Commands
Table 3-7 Search Character Options
Table 3-8 Terminating a Strinq Search
Table 3-9 EDITOR Error Codes
Table 4-1 System Copy Options
Table 4-2 System Copy Error Messages
Table 5-1 PALC Options
Table 5-2 Use of Operators
Table 5-3 PALC Error Codes

vii

2-2
2-8
2-12
3-1
3-8
3-9
3-10
3-11
3-12
3-16
3-20
3-21
4-1
4-4
5-5
5-15
5-34

Table 6-1 Cassette BASIC Functions
Table 6-2 Function Addresses
Table 6-3 Floating-point Accumulator
Table 6-4 Floating-Point Instructions
Table 6-5 Relative Addresses
Table 6-6 Cassette BASIC Error Messages
Table 6-7 Cassette BASIC Symbol Table
Table E-l Monitor Memory Map
Table E-2 utility Subroutines and Locations
Table E-3 Header Record Structure

6-38
6-45
6-46
6-50
6-51
6-57
6-60
E-l
E-l
E-ll

ILLUSTRATIONS
Figure 1-1
Figure 1-2
Figure 1-3
Figure E-l
Figure E-2

Cassette Progranuning System
CAPS-8 Cassette
l-1ounting a Cassette
Switch Option Characters
Ring Buffers

viii

1-1

1-3
1-6

E-IO
E-IO

CHAPTER 1
THE CASSETTE PROGRAMMING SYSTEM

1.1 INTRODUCTION TO A CASSETTE STORAGE SYSTEM
The PDP-8 Cassette Programming System (CAPS-8) is a small programming
system for the PDP-8/E (8/M or 8/F) computer and is designed around
the use of cassettes for program storage, rather than DE~tape, paper
tape
or
disk storage.
CAPS-8 replaces paper tape procedures
completely. The MI8-E Hardware Bootstrap initially loads the Cassette
Keyboard Monitor into memory: with the use of the Monitor all file
transfers and program loading and storage is done via cassette.
Cassettes are more convenient and reliable and much easier to use than
paper tape, and in addition, cut the time involved in loading and
storing programs using paper tape by almost one half.
CAPS-8 provides the user with a Keyboard ~1oni tor, I/O facilities at
the Monitor level, and a library of System Programs, including a
machine language assembler, an editor, and a higher-level programming
language.

Figure 1-1 Cassette Programming System

1-1

1.1.1 Hardware Components
The Cassette Pro9ramming System is built~ around a PDP-8/E, 81M, or 8/F
computer with a minimum of one TU60 dual cassette unit, a console
terminal (LA30 DECWriter, LT33 or LT35 'I'eletype, or VT05 DECterminal),
and 8K of memory. A line printer is opt:ional.

1.1.2 Software Components
A brief description of the software
Cassette Programming System follows.
greater detail later i.n the manual.

package available with the
Each program is discussed in

1. MONITOR -- The Keyboard Monitor provides communication
between the user and the Cassette System Executive
Routines by accepting commands from the console terminal
keyboard.
The commands allow i:he user to run system and
user proograms, save programs on cassette, and obtain
directories of cassettes.
2. Symbolic EDITOR - The EDITOR allows the user to modify or
create
source files for use as input to language
processing programs such as BASIC and PALC.
The EDITOR
contains powerful text manipulation commands for quick
and easy editing.
3. PALC Ass-embler (Program Assembly Language--Cassette)
PALC accepts source files in the PAL machine language and
generates absolute binary files as output.
These files
can then be loaded and executed using Monitor commands.
4. BASIC
BASIC provides a
higher-level
programming
language which is easy to learn and use.
It includes
such language features as user-coded functions, data
files on cassette, and program chaining.
5. System Copy (SYSCOP) - SYSCOP allows the user to transfer
files from one cassette to another, giving him the
ability to make multiple copies of a cassette and "clean
up" full cassettes so that they may become available for
future use.

1.2 WHAT IS A CAPS-8 CASSETTE?
A CAPS-8 cassette is a magnetic tape device much like that used in a
cassette tape recorder. The tape itself and the reels it is wound on
are enclosed inside a rectangular plastic case
(see Figure 1-2),
making handling, storage, and care of the cassette convenient for the
user.

1-2

On either end of one side of the cassette are two flexible plastic
tabs called write protect tabs (see A in Figure 1-2). There is one
tab for each end of the tape; since data should only be ~Titten in one
direction on the t.ape, the user will need to be concerned with only
the tab which is specifically marked on the cassette label. Depending
upon the position of this tab, the user is able to protect his tape
against accidental wri ting and destruction of data.
wt.en the tab is
pulled in toward the middle of the cassette so that the hole is
uncovered,
the tape is write-locked; data cannot be writ.ten on it and
any attempt to do so will result in an error message. wt.en the tab is
pushed toward the outside of the cassette so that the hol.e is covered,
the tape is write-enabled and data can be written onto it.
Data can
be read from the cassette with the tab in either positior ..
The bottom of the cassette (B in Figure 1-2) provides an opening where
the magnetic tape is exposed.
The cassette is locked int.o position on
a TU60 cassette unit drive so that the tape comes in cont.act with the
read/write head through this opening.
Both ends of the magnetic tape in a cassette consist of clear plastic
leader/trailer tape;
this section of the tape is not used for
information storage purposes, but as a safeguard in handling and
storing the cassette itself.
Since cassette tape is ~:usceptible to
dust and fingerprints, the leader/trailer tape should be the only part
of the tape exposed whenever the cassette is not on a drive.

UNCOVER HOLE TO PRCTECT DATA

\'----A-~
Figure 1-2

CAPS-8 Cassette

1-3

1.2.1 The Format of a Cassette
A cassette is formatted so that it consists of a sequence of one or
more files. Each file is preceded and followed by a file gap.
(A gap
in this sense is a set length of specially coded tape.) All cassettes
must start with a file gap; any information preceding the initial file
gap is unreliable. A file consists of a sequence of one or more
records separated from each other by a record gap. The first record
of a file is call~:!d the file header record and contains information
concerning the name of the file, i t:s type, length, and so on.
(Chapter 2 provid~:!s more information concerning header records.) A
record generally contains
128 (decimal) characters of information;
there are approximately 600 records per cassette tape.
Records consist of a sequence of one or more cassette bytes; a byte in
turn consists of eight bits each representing a binary zero or one.
Characters and numbers are stored in bytE!s using the standard ASCII
character codes (see Appendix A) and binary notation.
The number of records of information on a .cassette tape may be
estimated by the user. On the outside of the cassette case is a clear
plastic window (C in Figure 1-2). Along the bottom of this window is
a series of marks; each mark represent:"s about 50 inches of magnetic
tape. Knowing that approximately 2 records fit on an inch of tape,
the user is able to make a reasonable 9uess as to the length of tape
and number of records available for use. By simply glancing at the
width of the tape reel showing in the window, the user can tell
quickly if he is very close to the end. Since he is given no advance
warning of a full tape condition, the USE!r must visually keep track of
the length of tap4~ he has available.
Should the tape become full
before his file transfer has complet:ed, another cassette must be
substituted, and the transfer or output operation must be restarted.

1.2.2 The Sentinel File
The last file on a cassette tape is called the sentinel file.
This
file consists of only a file header record and represents the logical
end-of-tape. A zeroed or blank cassette tape is one consisting of
only the sentinel file.

1.3 THE SYSTEM CASSETTE
The software discussed in Section 1.1 is provided to the user on a
single cassette called the System CassHtte. This is the cassette on
which the entire CAPS-8 System resides, cmd it is utilized for all
system functions. The System Cassette must always be mounted on drive
0; drive 0 serves as the default device \\Then the user fails to specify
another.

1-4

NOTE
Each TU60 dual cassette unit has two
drives. The drive on the left is always
odd-numbered and the drive on the right
even-numbered; thus, drive 0 will be the
le!ft drive.
If the user has more than
one TU60 dual cassette unit, he should
probably label the drives in consecutive
order so that there will be no confusion
when he is using the system.
The write protect tab on the System Cassette should usually be in the
write-locked position so that data will not accidently be written on
it; it is suggested that the user make a copy of this cassette as
protection against loss or accidental destruction.

1.4 MOUNTING AND DISMOUNTING A CASSETTE
To mount a tape on a drive, hold the tape so that the open part of the
cassette is to t:he left and the full reel is at the top. Set the top
write protect tab to the desired position depending upon whether data
is to be written on the tape.
Open the locking bar on the cassette drive by pushing it: to the right
away from the drive (see A in Figure 1-3). Next hold the tape up to
the cassette drive at approximately a 45-degree angle and insert the
tape
into
the!
drive
by applying a leftward pressure while
simultaneously rotating the cassette over the drive sprockets.
This
brings the tape! into position against the read/write head. Push the
tape into the uni.t so that when the cassette is properly mounted, the
locking bar automatically closes over the cassette back edge.
(Figure
1-3 illustrates this procedure.)
Press the rewind button on the cassette unit (see B in Figure 1-3;
there is a rewind button for each drive). This causes t:he cassette to
rewind to the beginning of its leader/trailer tape.
(Pressing the
rewind button a second time causes the cassette to re"rind to the end
of the leader/trailer tape and to the physical end·oof-tape.
The
cassette unit will click; this sound is almost inaudible and the user
may not hear it unless he is listening carefully.
Normal usage
requires that t:he user press the rewind button only once whenever he
wishes to manually re\"lind a cassette). Even though tapes which are
not actively being used on a drive should already be po!;;i tioned at the
beginning, the user should develop the habit of
automatically
rewinding a cassette.
When the tape has finished winding, the
cassette will stop moving. The cassette is now in plaCE! and ready for
transfer operations.

1-5

Figure 1-3 Mountin9 a Cassette
Before removing a cassette from a drive, the tape should always be
rewound to its beginning.
This can be done by pressing the rewind
button on the cassette unit or by issui.nq the REwind Monitor Command
as explained in Chapter 2. Rewinding a tape ensures that the clear
leader/trailer tape will be the only tape exposed at the open part of
the cassette. To remove a cassette from the cassette drive, open the
locking bar and the cassette will pop out.
When cassettes are not
being actively used on a cassette drive, they can be stored in the
small plastic boxes provided for this purpose by the manufacturer.
NOTE
Before using a new cassette, or prior to
using a cassette that has just been
shipped or accidently dropped, mount the
cassette on a drive so that the Digital
label faces the inside of the unit and
perform a rewind operation. Remove the
cassette, turn it over, and perform
another rewind operation.
This packs
,the tape neatly in the cassette and
places the full tape reel at the proper
tension.

1.5 CONCERNING EXAMPIJES
In the chapters that follow, care has been taken to include acutal
machine printout whenever possible. In cases in which there may be
some discrepancy as to whether a character was typed by the user or by
the system, that typed by the system will be underlined.

1-6

CHAPTER 2
GETTING ON-LINE WITH THE CAPS-a SYSTEM

2.1 SYSTEM PROGRAMS
The Cassette Programming System is distributed on a single cassette,
called the System Cassette, which contains all the proc;rrams necessary
for loading the Monitor into memory and creating and running system
and user programs.
The directory of the System Cassette is as
follows:

C2BOOT.BIN
MONfOrl.BIN
bt!:lCOP.BIN
.BIN
EDIT
~ALC
.B IN
BA!:)IC .BIN

01/22/73
01/22/73
01/25/73
01/02/73
01/02/73
01/02/73

V1
V1
V2
V1
V1
VI

System files are in binary format (see section 2.2.1). The first two
files on any System Cassette must be C2BOOT.BIN and MONTOR. BIN; these
two files comprise a bootstrap and the Keyboard Monitor.
C2BOOT.BIN
loads the Moni t:or into memory from the System CassettE~; the Keyboard
Monitor links the user and the CAPs-a System by providing a means of
communication bet:ween the two. By accepting commands from the console
terminal keyboard, the Cassette Keyboard Monitor allows the user to
run system and user programs, save and recall files utilizing cassette
storage, and create, assemble, and load programs.

2.2 SYSTEM CONVENTIONS
The following c:onventions concern file formats and file naming
procedures and are standard for the CAPS-a System, as WE!ll as for many
other systems.

2.2.1 File Format:s
The Cassette Programming System makes use of two types of file formats
-- ASCII and Binary.
Files in ASCII format conform to the Ame:rican National Standard Code
for Information Interchange in which alphanumeric characters are
represented by a 3-digit code. A table containing ASCII character
codes in 7- and B-bit octal is provided in Appendix A.
Binary format files consist of l2-bi t bi.nary words repr~~senting PDP-8
machine language code.
The standard DEC binary format is used with
the exception that no checksum is necessary.
Binary files contain
field addresses and memory instructions and are read directly into

2-1

memory for immediate execution. CAPS-8 System Programs are in binary
format, and pr09rams which the user assembles with PALC are translated
into files in binary format.

2.2.2 Filenames and Extensions
System and user files are referenced symbolically by a name of as many
as
six
alphabetic characters
(A-~:)
or digits
(0-9),
followed
optionally by an extension of from 1 to 3 alphabetic characters or
digits;
(the :Eirst character in a filename must be alphabetic). The
extension to a filename is generally used as an aid in remembering the
CAPS-8 format o:f a file.
Table 2-1 lists commonly accepted extensions
-- the user mayor may not conform to this list as he chooses; it is
included here only as a guide:
Table 2-1 CAPS-8 Ext:ension Names
Extension
PAL
BIN
BAS
TXT
DOC
DAT

Meaning
PALC source file (ASCII)
System or user binary format file
BASIC source file (ASCII)
Text file (ASCII)
Documentation file (ASCII)
Data file (ASCII or other)

Generally the user may call his files by any mnemonic filename and
extension he chooses.
In some cases, if he omits specifying an
extension, the System Program he is running may assume an extension.
For example, PALC assumes an extension of .PAL unless the user
.BIN unless another
indicates another, and the Run command assumes
extension is specified.

2.2.3 Input/Output Devices
There are three available categories of input/output devices in the
Cassette Programming System: consolE~ terminal keyboard (including
paper tape reader and punch if an LT33 Teletype containing these units
is used as the console terminal), cassette drives 0-7, and a line
printer. There are no permanent devicE~ names in the CAPS-8 System.
Command strings and I/O designations are entered in such a way that
the user specifies the device by a drive number and the file by a
filename;
option characters allow th.~ user to direct listings to the
line printer or to otherwise change th.~ normal operating procedure of
a program. The System Cassette -- drive 0 -- is the default device if
no drive number is specified. For example:
.DI/L

2-2

(DI is a Monitor command instructing thE~ computer to print a directory
listing of a cassette. Since no drive number is specified, drive 0 -the System Cassette -- is assumed.
The option character L sends
output to the line printer instead of the console terninal, which is
the normal output device.)

2.3 LOADING THE KEYBOARD MONITOR
The CAPS-8 hardware bootstrap and C2BOO~~ .BIN on the System Cassette
are used to load the Cassette Keyboard Monitor into memory.
(Both
bootstraps are described in Appendix E.) Loading the Monitor is
accomplished as follows:
1.

Ensure that the computer and tE~rminal are on-line.

Press and raise the HALT key. Make sure that the SINGLE
STEP key is in a raised position.

Place the System Cassette (wri1:e-locked to p.rotect data)
onto cassette unit drive 0;

Press and raise the SW key.

At this point the RUN lamp should be on and the System Cassette should
begin to move. The hardware bootstrap calls the first program on the
System Cassette (C2BOOT.BIN) which in turn loads the Keyboard Monitor
(MONTOR.BIN)
into memory.
If an error occurs during the loading
process (for example, an error may be caused by the cassette being
improperly mounted, by a missing file on the tape, or by the
occurrence of an I/O error) no error message will inform the user
since the Monitor is not completely in memory.
Instead, the System
Cassette may stop moving and the computer may loop or halt.
If this
is the case, steps 2-4 above should be repeated.
Once the Monitor has been loaded, the System Cassette stops moving and
a dot is typed at the left margin of the console terminal page. This
instructs the user that the Monitor is now in memory and ready to
accept input commands.

2.4 USING THE KEYBOARD MONITOR
Each command to the Keyboard Monitor is typed at the console terminal
keyboard in response to the dot at the left margin. A command is
entered by pressing the RETURN key.

2.4.1 Making Corrections
Corrections may be made to the command line providing they are made
before the line is entered (that is, before a carriage return has been
typed). The RUBOUT key is used to correct typing errors. Pressing the

2-3

RUB OUT key once causes an open bracket ([) to be typed followed by the
last character entered into memory. Aft~er this character is echoed on
the console terminal it is deleted from memory.
Successive RUBOUTs
each cause one more character to be printed and deleted. The first
non-RUBOUT character typed (after the last RUBOUT in a sequence)
causes a closing bracket (]) to be printed, thus enclosing only the
deleted portion of text within brackets. For example:
The user types: .. R BACIC (RUBOUT) (RUBOUT) (RUBOUT) SIC
The console terminal shows: .H 8AC I C (C I C] SIC
The string is entered to the-Keyboar~~itor as: .R BASIC

2.4.2 Special Characters (CTRL/C, CTRL/O, and CTRL/U)
Control can be rE~turned to the Keyboard Moni tor while under any of the
System Programs by typing a CTRL/C (produced by holding down the CTRL
key and simul tanE~ously pressing the C ke!y).
If the Monitor is not
still in memory, a CTRL/C causes a complete rebootstrap by reading the
appropriate files from the System Casset:te on drive O.
When it is
ready to accept input, the Keyboard Monitor types a dot at the left
margin of the teleprinter (i.e. console terminal) page.
Teleprinter output can be suppressed by typing a CTRL/O
(produced by
holding down the CTRL key and simultaneously pressing the 0 key) •
This allows execution of the program to continue, but stops all
console printout.
Typing a second C'l'RL/O will resume output again.
Unless output is extremely lengthy, or unless the program is waiting
for input from the user, processing of a program after an initial
CTRL/O will usually be completed before the user is able to type a
second CTRL/O.
Printout will automatically resume when control is
returned to the Keyboard Monitor (indicated by a dot at the left
margin) •
NOTE
crRL/o
does
not
prevent
certain
important error messagE!S from printing
on the console terminal.
A corranand line ma.y be deleted completely, before it is entered, by
typing a CTRL/U (produced by holding down the CTRL key and pressing
the U key). This causes the current command line to be ignored and
returns control to the Keyboard Monitor. The Monitor prints a dot at
the left margin to indicate that it is ready to accept another
command.

2-4

2.4.3 I/O Designations and Specification Options
Whenever the user runs a System Program or performs any I/O operation,
he must indicate1:he file(s) to be accessed, the cassetb! drive(s)
on
which they are located, and any desired options associa1:ed with the
operation. Procedures used in entering t~his information are explained
below.
Monitor commands q-enerally require only Gl single command line which
specifies the wlit drive number (in the range 0-7), filename (s), and
option(s) in the following format:
.COMMAND DRIVE #:FILENAME:.EXT/OPTION(S)
COMMAND represents one of the eight Monitor commands discussed in
Section 2.5.
The filename should be se~parated from thl~ drive number
by a colon. Options are alphabetic characters and are sl~parated from
the rest of the command line by the slash character (/1. Successive
options follow onl~ another without any separating ch,3.racter.
The
command line is executed by typing a carriage return.
I/O specifications to System Programs follow a diffl~rent format.
First the System Program is called from the System Cassette using the
Monitor Run command. The System Program then asks for the input
filename, drive number, and options, and then the out:;>ut filename,
drive number, and options. This informat:ion is usually reques ted in
two separate command lines, but the actual format "aries between
System Programs. Generally, the command strings appear as follows:
.R SYSTEM PROGRAM/OPTIONS
*INPUT-DRlVE # : FILENAME
*OUTPUT-DRIVE #: FILENAME
The appropriate chapter should be referenced for the accurate format.
Options are available in most System Programs and Monitor commands
allowing the user to change the order or format of input and output
operations from that which would normally be carried out by the
program.
Again, interpretation of options varies; the user should
refer to the appropriate section or chapter to learn which options are
available and what actions will result from their use.

2.5 KEYBOARD MONITOR COMMANDS
There are eight Keyboard Monitor commands available to the user.
Commands are typed in response to the dot printed by the Monitor and
are entered when the RETURN key is pressl~d. Each command consists of
one or more alphabetic characters, followed by a space (or any
non-alphabetic character).
Any error made while utilizing these
commands will result ~n a message informing the user (see Section
2.8). After occurrence of an error, control returns to the
Keyboard
Moni tor and the command must be re-typed.
(Since several of the
commands begin with the same letter, the user must be sure to note how
much of the command must be entered in order to distinguish it from
other commands. While it does not matter if too many characters are
entered, too few will cause errors.)

2-5

2.5.1 Run Command
The Run command is of the form:
• R Drive #:Filename/Option (s)
The Run command instructs the Monitor to load and execute the file
specified in t~e command line. The file should be in self-starting
binary format (t:hat is, the last location in the source file must be
an origin sett:ing which indicates the starting address of the file);
as the file is not in self-starting binary format, the program will be
loaded but execution will not begin; the user will have to proceed as
though he were using the Load command (see Section 2.5.2).
The user
may omit specifying an extension as the Monitor assumes .BIN. For
example:
:R CART.BIN

or
.ft CART

Regardless of which command string the user types, the Monitor assumes
.BIN, searches drive 0 for the file CART. BIN, and executes it.
Options allowed in the command line depend upon the program the user
is running.
Availability of options and results of their use are
discussed in Chapters 3, 4, 5 and 6. No error occurs if the user
specifies an option not allowed by a program; the option is simply
ignored.
Multiple files may be executed using the Run command.
Patches to
programs, BASIC user-coded functions, and programs the user may have
created using PALC can be executed as follows:
.R Drive #:PROGl,Drive #:PROG2, ••• PROGn/Option(s)
where n represents any number of programs as long as the total number
of characters on the input specification line does not exceed 64. The
user must enter programs in the command line in the order in which he
wants them executed and must be careful to include appropriate
starting, chaining, and return addresses (see Appendix E).
For example, assume the user has written a routine which will be used
for debugging purposes; each time a certain condition is met during
execution, this routine will be accessed, print a message and cause
execution to halt.
The routine ha.s been created using the CAPS-8
EDITOR, assembled with PALC, and is stored on cassette drive 1 as
DBG.BIN; it is loaded into memory with the user's program (TABLE.BIN
stored on casset:te drive 0). The programs are loaded as follows:

2-6

Chapter 6, BASIC, contains an example of running multiple
conjunction with the BASIC user-coded function feature.

files

2.5.2 Load Command
The Load command is used to load a binary file into memory
the form:

and

takes

.L Drive #:Filename.ext/Option(s)
This cormnand is similar to the Run cormnand except that the computer
halts after loading the file.
To start execution, the user sets the
correct starting .address in the Swi tch RE~gister, presse:3 ADDR LOAD,
CLEAR and CONT
(if the file is in self-starting binary format, the
user need only press CONT): appropriate addresses included in the
program (see Appendix E) will return control to the Keyboard Monitor
after execution.
Multiple files may be loaded in the same manner as in tha Run command
by simply specifying them in correct E~xecution order ':>n the command
line:
.L Drive #:PROGl,Drive #:PROG2 •••• PROGn/Option(s)
Again, n may represent any number of pr09rams as long as the
number of characbars on the command line does not exceed 64.

total

2.5.3 DAte Command
The DAte command is of the form:
.DA mm/dd/yy
where nun, dd, and yy repres~nt the current month, day and year as
entered by the user.
(One or two-digit numbers in the range 0-99 are
allowed in the DA'te command. The Keyboard Monitor does not check for
errors other than the entry of a number which is outsid,a this range.)
This date will then appear in directory listings (see Section 2.5.4),
and the date of creation of all new files will be included.
If the
DAte command is not used, directory listings will contain only
filenames, as illustrated in section 2.1.,

2.5.4 DIrectory Command
The DIrectory comnand is of the form:
.DI Drive #/Option(s)
and causes a directory listing of the cassette on the drive specified
to be output on the console terminal. N() colon is necessary after the

2-7

drive number. There are
DIrectory command:

two

options

available

for

use

with

the

Table 2-2 Directory Options
Option

Heaning

Causes the listing to be output
on the line print.er rather than
the console terminal.

Causes a "fast" listing to be
produced
(omi t·ting
creation
dates and version numbers).

In the following example a directory of cassette drive 2 is requested
and output
(the version number in the directory listing reflects the
number of times the file has been accessed and changed using the
CAPS-8 EDITOR; see Chapter 3, Section 3.:2.3):

lr/1/~9/7?

FILE
.RIN
ARCDEF.PAL
A
.ASC

~3/17/72

1)22

This same directory using the F option will be reduced to:

HlJ/29/7?

FILE
.AIN
ARCDEF.Pl\L
A
.ASC
R

2.5.5 DElete Command
The DElete command is of the form:
.DE Drive #:Filename.ext
and causes the fi.lename on the specified drive number to be deleted
from the direct;ory.
The fi lename is replaced by the name *EMPTY in
the directory listing and the file can no longer be referenced.
Only
one file may be specified in the DElete command string at a time.

2-8 .

For example, assume the user wishes to delete the
from the directory of cassette drive 3. He types:

filE:name

MATH.DAT

.DE 3:MATH.DAT

and then obtains a directory listing of drive 3.
appear as follows:
11 /17/72
TAPE
.BAS
*EMPTY.
TOR
.ASe

The

directory

will

11/02/72
11/07/72

where *EMPTY represents the deleted filename MATH. OAT.

2.5.6 Zero Command
The Zero command is of the form:
.Z Drive #:Filename
and specifies that the sentinel file of the indicated cassette is to
be moved so that it immediately follows the file indicated in the
cornmand line.
(See Chapter I for a description of the Bentinel file.)
All files following the sentinel file: are deleted from the cassette
and that portion of the tape is complete:ly reusable.
For example, assume cassette drive 3 contains the follm"ing directory:

LOO~

.Ase

BASE

• RAS

FOfJR

.RUJ

10/~3/72

11/17/72

*EMPTY.
RAC~

•E

and the user wishes to save only the first three files.
Zero command as :follows:

and the sentinel fi Ie is placed immediat:ely after the
The directory nrnN reads:

file

LOOK.ASC
BASE.gAS

1~/2~/72

2-9

uses

the

FOUR. BIN.

When no filename is specifed in the command line, for example:
.2

the cassette is said to be zeroed, or completely deleted of files; the
sentinel file i.s moved to the beginning of the cassette so that the
entire tape is available for use. This method is useful in "cleaning
up" cassettes which may contain several *EHPTY files in the directory
listing but have become full and therefore unavailable for further
use. First, any needed files are transfered to another cassette using
SYSCOP (see Chapter 4), then the directory of the old cassette is
zeroed.
The sentinel file is written at the beginning of the tape
making the casset.te completely reusable.
All new tapes must be zeroed before they are first used. This ensures
that a sentinel file is present on the tape and moved to the beginning
of the tape.

2.5.7 REwind Command
The REwind command is of the form:
.RE Drive #
and causes the cassette on the drive number specified to be rewound to
its beginning.
(The user can also cause the tape to rewind by
pressing the rewind button on the cassette unit.) System Programs and
Moni tor commands always re'''Iind a cassetbe before accessing a file, but
if the user delevopes the habit of rewind.ing the cassette himself he
performs a timesaving action.
A cassette should always be rewound
before it is removed from a drive.

2.5.8 Version Command
The Version command is used to find out
Monitor currently in use. Typing:

the

version

number

the

.V
instructs the Monitor to respond with
example:

the

appropriate

lLa
indicates that version 1.2 is currently in use.

2-10

number.

For

2.6 NOTES ON DEVICE HANDLERS
Device handlers for the CAPS-8 System are~ described in Appendix E.
few notes of interest concerning the1r use are included llere.

The line printer performs a form feed ope:ration before beginning an
output task.
Characters are unpacked from the output buffer and
printed. A form feed is also produced following the completion of an
output task. ThE~ line printer handler is capable of handling only an
80 column printer ..
If the console terminal is an LT33 Tele:type containinq reader and
punch units, these may be used as input/output devices :i.n conjunction
with the Teletype keyboard.
To punch a t,ape, simply place the punch
unit to ON; to read a tape,
place the reader unit to START.
Characters will be printed on the Teletype keyboard as tiley are read
or punched. Binary tapes may not be punched.
NOTE
The purpose of the Cassette Programming System is
the
elimination
of
paper
tape procedures.
CassettE~s provide a more convenient, reliable
and
faster means of program storage than paper tape.
Therefore, although paper tapes may be read and
punched using the LT33 paper tape units, therE~ is
no support for this type of I/O and its use is not
encoura g ed •
If the user's pro<Jram does not over-write certain areas of memory, the
parts of the Monitor which are in these locations are available for
use. This allows the user who takes advantage of wri 1:ing his own
programs in the PAL machine language to access system handlers and to
restart or rebootstrap the Cassette Keyboard Monitor after program
execution.
Information concerning Monitor Service Routines,
I/O
routines, device handlers, and internal descriptions of the Keyboard
Monitor are provided in Appendix E.

2-11

2.7 KEYBOARD MONITOR ERROR MESSAGES

The following error messages may occur when the
used incorrectly:
Table 2-3

Keyboard

Monitor

Keyboard Monitor Error Messages

Message

Meaning

BAD COMMAND

The user has failed to follow the
correct synt:ax for Moni tor commands.
This may be the result of mispelled
commands
or
too many or improper
arguments in a command string.

FILE NOT FOUND

The Monitor could not locate the file
(or files) specified. The user should
check to be sure that filenames are
spelled correctly and that the unit
drive number specified is correct.

INPUT ERROR ON UNIT n
OUTPUT ERROR ON UNIT n

An I/O

UNIT n NOT RE,ADY

There is no cassette on the drive
specified, or no such drive exists.

UNLOCK UNIT n

The user tried to write data when the
write protect tab of the cassette on
the drive specified was write-locked.
To
write
data
this tab must be
write-enabled.

error has occurred on the cassette drive specified.
This may be
caused
by an incorrectly formatted
cassette or may be due to a timing
error.
The user should try the I/O
transfer using another cassette.

2-12

CHAPTER 3
SYMBOLIC EDITOR

3.1

INTRODUCTION

The CAPS- 8 Symbolic EDITOR is used to cre!ate and modify ASCII source
files so that these files may be used as input to other System
Programs such as BASIC and PALC.
The EDITOR considers a file to be divided into logical units called
pages.
A page of text is generally 50-60 lines long, ruld corresponds
approximately to a physical page of a program listing.
(Note that
this is not the :3ame as a memory page). The EDITOR reads one page of
text at a time from the input file into its internal buffer where the
page becomes available for editing.
ThE~ Editor contain::; commands for
creating, modifying, or deleting characters, lines, or complete
logical pages of text. All commands consist of a single letter or a
letter wi th arguml~nts, and are executed by typing the RE~rURN key.

3.2

CALLING AND USING THE EDITOR

To call the EDITOR from the System Cassette, type:
• R EDIT/Options
in response to

3.2.1

th4~

dot (.) printed by the! Keyboard Monitor.

EDITOR Options

There are two options available for use with the EDITO:~; these are
described in Table 3-1.
(Option usage has been previo1lsly discussed
in Chapter 2, Section 2.4.3).

Table 3-1 EDITOR Options
Option

Meaning

Convert two or more spaces
reading from input device.

More than one file will be used fo.r input.
(When one of these commands--E, F, J, N, R,
or Y--is issued and an
end-of-file
is
encountered, the EDITOR pauses and requests
that the user specify another input file,
thus allowing continuation of the command.
If the /M option has not been previously
specified in the input line, the end-of-file
condition remains in effect.
See Se:tion 3.9
for an example.)

3-1

'rAB

when

3.2.2

Input and Output Specifications

After the EDITOR has been called from the System Cassette it asks
the input specification as follows:

for

*IN,)'JT FILE-

The user responds with the input cassette drive number and
filename and extension, if any. For example:

the

input

If only a filename (and no input cassette drive)
is specified, the
default device--drive O--is assumed; the EDITOR prints the user's
input specification line, only first it includes the assumed default
device before echoing the filename, as illustrated below:

The user has typed the filename AB, but bE~fore this is printed, the
EDITOR inserts 0: and then goes on to eeho AB. If the input file is
not found or if a syntax error occurs, the EDITOR prints a question
mark (1), types an asterisk
(*) at the left margin, and waits for
another input designation. Any number of input files is permitted.
If no input specification is made, (that is, a carriage return only
has been typed in response to the INPUT request), a new file will be
created using the console terminal keyboard as the input device.
The
EDITOR allows input from the keyboard via the Append command (see
Example Using the EDITOR for an illus1:ration of this method of
creating a program).
If more than one input file is to be entered, the 1M option must be
specified when the EDITOR is called flC'om the System Cassette. The
user responds to the INPUT FILE line ''lith the drive number and
filename of the first input file. He enters output information as
described next, and then edits his file.
When the end-of-file is
reached during the editing procedure, the EDITOR again prints the
INPUT FILE request and the user responds ,.,ith the drive number and
filename of the second file. When the us«:!r finishes editing his final
file and no more input files are available, he responds to the
EDITOR's INPUT request by typing a t:=arriage return; the EDITOR
continues and closes the output file. All input files are combined
under the one filename specified in the output line.
The EDITOR initially requests output information by printing:

3-2

The user responds with the output
example :

drive:

number

and

:Eilename.

For

Again, if no device is designated, drive 0 is assumed and echoed.
If the output file is to have the same name as the input file, the
user need only type the correct out.put drive number followed by a
carriage return; the EDITOR will echo the assumed name. For example:
*I\Jp'rr FILf~-l :FIL~.f~AS
*OJTPJT FILE:~:FILE.8AS

The EDITOR allows only one output file and creates the header for this
file on the specified cassette, deleting any file already on that
cassette under the same name (and replacing it with 'if EMPTY in the
directory listing) and leaving the cassette correctly postioned for
further output.
NOTE
If no output designation is specified
(that is, a carriage return only has
be~en typed in
response to the OUTPUT
FILE
request),
the
only
output
operations which may be performed are L
(list buffer on the console terminal) or
V (list buffer on the line printer).
Only cassette files in ASCII mode are acceptable for use by the
EDITOR.
No error message is given if non-ASCII files are input, but
the results of editing operations are garbled.
Once I/O file designations are entered, the Symbolic EDITOR is ready
to accept commands from the keyboard.
It signifies this by printing a
number sign (#) c:lt the left margin: this symbol occurs whenever the
EDITOR is waitin9 for a command.

3.2.3 Version Numbers
Each time a filename is indicated in response to thE~ output file
specification line, the number 0 is assigned to it:. This number
(called the version number) signifies that a new file has been created
and that it has not been previously edited or referenced under this
filename.
The user may call a file from a specified cassette, make corrections
to it and change it any number of times before he is finally satisfied
with it or ready to use it for some other operation. In this case, he
may reference the file in the output specification linH by specifying
only the output c:assette drive number followed by a carriage return,
since the filename itself will not be changed. Each time he does

3-3

this, the version number of the file i:3 increased by 1. When the
version number of a file has been incremented in this manner so that
it is greater than 0, it appears in dir.~ctory lis tings on the same
line as the filename (see Chapter 2).
NOTE
Version numbers associab~d with edited
files should not be confused with the V
Monitor command,
which
prints
the
version of the Monitor currently in use.

3.3

MODES OF OPERATION

The EDITOR operates in one of two diffe:rent modes: command mode or
text mode.
In command mode all i:nput typed on the keyboard is
interpreted as commands instructing the EDITOR to perform some
operation.
In text mode, all typed input is interpreted as text to
replace, be inserted into, or be appended to the contents of the text
buffer.

3.3.1

Transition Between Modes

Immediately afte:r being loaded into memory and started, the EDITOR is
in command mod.e.
The special character # is printed at the left
margin of the teleprinter page indicati:ng that the EDITOR is waiting
for a command..
All commands are terminated by pressing the RETURN
key.
In text mode, the EDITOR performs I/O operations on text stored within
the text buffer. Text is input to the EDITOR buffer until a form feed
is encountered. A line of text is terminated by a carriage return.
If no carriage return is present, the "text entered on the current line
is ignored. The buffer has room for approximately 5200
(decimal)
characters. Whem text has been input to the extent that there are
only 256 decimal locations available in the buffer, the console
terminal rings a warning bell.
From this point on, whenever a
carriage return is detected during text input, control returns to the
EDITOR command mode and the bell is rung. This line-at-a-time input
may continue until the absolute end-of-buffer is encountered. At this
point, no more text will be accomodated in the buffer: a "?" is
printed and cont:rol returns to command mode every time the
user
attempts to input more text.

3.4

SPECIAL CHARACTERS AND Fm~CTIONS

A number of the
functions.
These
below.

console terminal keys have special
operating
keys and their associated functions are described

3-4

3.4.1

RETURN Key

In both command Clnd text modes, typing the RETURN key causes a
carriage return and line feed operation and signal~1 the EDITOR to
process the information just typed.
In command mode,
:,-t allows the
EDITOR to execute the command just typed. A command will not be
executed until ii: is terminated by the F~TURN key (with the exception
of =, explained later).
In text mode, RETURN causes the line of text
which it follows to be entered in the te!xt buffer. A 1:yped line is
not actually pari: of the buffer until terminated by the RETURN key.

3.4.2

Erase (CTRL/U)

The erase charact:er (CTRL/U combination) is used for error recoveries
in both command and text modes.
It is generated by holding the CTRL
key while simultaneously typing the U ke:y. When used :Ln text mode,
CTRL/U cancels everything to its left back to the bHginning of the
line; the EDITOR echoes t u and performs a carriage ret. urn/line feed
(CR/LF); the user then continues typing on the next l:.ne. When used
in command mode I' CTRL/U cancels the entire command; the EDITOR
performs a CR/LF and prints a #. The: erase character cannot cancel
pas t a CR/LF in Ed ther command or text mode.

3.4.3

RUB OUT Key

Rubout is used in error recovery in both command and text modes.
In
text mode typing the RUBOUT key echoes a. backslash (\) and deletes the
last typed character. Repeated rubouts delete from right to left up
to, but not including, the CR/LF which separates the current line from
the previous one.. For example:
TI-fS

(:)iJ~JICI-{\\\\ICK

RROW'\J

FOX

will be entered in the buffer as:

When used in command mode, RUBOUT is equivalent to the CTRL/U feature
and cancels thH entire comma'nd; the EDITOR prints a. #, 'performs a
CR/LF, and waits for another command to be entered.

3.4.4

Form Feed (CTRL/FORM)

A form feed signals the EDITOR to return to command mod.~. A form feed
typingr
the
CTRL ,ind FORM keys
character
is
generated
by
simultaneously. This combination is typed while in text mode to
indicate that the desired text has be!en entered and t.hat the EDITOR
should now return to command mode. The EDITOR performs a CR/LF and

3-5

prints a # in response to a CTRL/FORM to indicate that it is back in
command mode. CTRL/G is usually equivalent to CTRL/FORM except in the
case of a SEARCH command, as explained in section 3.8.1.

3.4.5

The Current Line Counter (.)

The EDITOR keeps track of the implicit decimal number of the line on
which it is currently operating.
The dot (produced by typing the
period key) stands for this number and may be used as an argument to a
command.
For example, .L means list the current line; .-l,.+lL means
list the line preceding the current line, the current line, and the
line following- it, then update the dot (current line counter) to the
decimal number of the last line printed.
The following commands affect the curr,ent line counter as indicated:

3•4•6

1.-

After a Read or Append command, the current line counter
is equ.al to the number of the last line in the buffer.

After an Insert or Change command, the current line
counter is equal to the number of the last line entered.

After a List or Search command, the current line counter
is equ.al to the number of the last line listed.

After a Delete command, the current line counter is
equal to the number of the line immediately after the
deletion.

After a Kill command, the current line counter is
to O.

equal

After a Get command, the current line counter
to the number of the line printed by the GET.

equal

After a Move command, the current line counter is not
updated and remains whatever it was before the command
was issued.

Slash ( /)

The slash symbol (/) has a value equal to the decimal number of the
highest numbered line in the buffer.
It may also be used as an
argument to a c:ommand. For example: 10,/L means list from line 10 to
the end of the buffer.

3.4.7

LINE FEED Key

Typing the LINE: FEED while in command mode is equivalent to typing .+1
and will cause the EDITOR to print the line following the current one
and to increment the value of the current line counter by one.

3-6

3.4.8

ALT MODE Key

Typing the ALT MODE key while in command mode will cause the line
following the current line to be printed and the current line counter
to be incremented by one.
If the curren 1t line is also the last line
in the buffer, typing either ALT MODE or LINE FEED will gain a
response of ? from the EDITOR indicating that there is no next line.
Some console terminals provide an escape key (ESC) in place of the ALT
MODE. Their functions are identical.

3.4.9

Right Angle Bracket (»

Typing the right angle bracket (» while in command mode is equivalent
to typing .+lL and will cause the EDITOR to echo > and then print the
line following the current line.
The value of the current line
counter is increased by one so that it refers to the last line
printed.

3.4.10

Left Angle Bracket

«)

Typing the left angle bracket «) while in command mode is equivalent
to typing .-lL and will cause the EDITOR to echo < and then print the
line preceding the current line.
The value of the current line
counter is decreased by one so that it refers to the last line
printed.

3.4.11

Equal Sign (=)

The equal sign is used in conjunction wi·th the pointer's dot
(.)
or
slash (I).
~Vhen
typed in command mode the equal sign causes the
EDITOR to print the decimal value of the argument preceding it.
In
this way the user may determine the nurnb.~r of the current line (. = ),
or the total number of lines in the buff.~r (/= ), or the number of
some particular line (/-8= ) without counting lines from the beginning
of the buffer. No carriage return need be typed following the equal
sign.

3.4.12

Colon (:)

Typing a colon produces the same result .as the equal sign (=).

3.4.13

Tabulation (CTRL/TAB)

The EDITOR is written in such a way as to simulate tab stops at
8-space intervals across the teleprinber page. When t.he CTRL key is
held down and the: TAB key is typed, the EDITOR produces a tabulation.
A tabulation consists of from one to 'eight spaces, de'pending on the
number needed to bring the carriage to the next tab stop.
Thus, the

3-7

EDITOR may be used to produce neat columns on the teleprinter or line
printer page. The tab function is used in conjuction with the /B
option (for input. and output) to allow the user to produce and control
tabulations in the text buffer during input operations.
On
input
(under a Read command), the EDITOR will replace a group of two or more
spaces with a tabulation if the user has specified the /B option.

3.5

COMMAND STRUCTURE

A command directs the EDITOR to perform a desired operation.
Each
command consists of a single letter, preceded by zero, one, two or
three arguments. The command letter tells the EDITOR what operation
to perform; the a.rguments usually specify which numbered line or lines
of text are affec'ted. Command format is illustrated in Table 3-2,
where E represents any command letter.
Table 3-2 Command Format
Type of Command

Command
Format

No Argument:

Perform operation E

One argument:

Perform
operation
referenced line.

Two Arguments:

m,nE

Perform operation E
through n, inclusive.

lines

Three Arguments: m,n$jE

3.6

.Meaning

the
m

This combina.tion is used by the
MOVE command only and is explained
in Section 3.6.3.

COMMAND REPERTOIRE

Commands to the EDITOR are grouped under three general headings:
Input Commands
Output Commands
Editing Commands
Explanation of the three types of commands is detailed in the
following sections. Each command description will state if the EDITOR
returns to comman.d mode after completing the operation specified by
the command. All commands are entered when the RETURN key is typed.
The EDITOR prints an error message consisting of a question mark
whenever the user has requested nonlexistent information or used
inconsistent or incorrect format in typing a command. For example, if
a command requires two arguments, and only one (or none) is provided,
the EDITOR will print ?, perform a carriage return/line feed, and
ignore the command as typed.
Similarly, if a nonexistent command
character is typed, the error message ? 'N'ill be printed, follo\'led by a
carriage return/line feed; the command will be ignored. However, if

3-8

an argument is provided for a cormnmand that does not require one, the
argument will be ignored and the normal function of the conmunand
performed. For example:
Resul t:

User Types:

The buffer is empty. The user is aBking for
nonexistent information.

L
?

The arguments are in. the wrong order.
EDITOR cannot list backwards.

7,5L
?

The

This cormnand requires two arguments before
the $: only one was provided.

The user types a nonexistent command letter.

l7$lOM

3.6.1

Input Commands

Two commands are available for inputting text, and
Table 3-3.

are

described

Table 3-3 Input Commands
Command
A

Format

Action. and Explanation
Append the incoming text from 1:he console
terminal
keyboard
to the information
already in the buffer (if there is no
input
file t.he buffer will be empty
initially). The EDITOR will enter text
mode upon receiving this command and the
user may then t.ype in any number of lines
of text. The n.ew text will be appended to
the information. already in the buffer, if
any, until a form feed
(C~rRL/FORM key
combination)
is
typed:
control
then
returns to command mode.
By using the Append command wi ':h an empty
buffer, a symbolic program may effectively
be generated on-line by en':ering
the
program via thE! keyboard.
Any rubout encountered during 4~xecution of
an Append command will del4~te the last
typed character.
Repeated rllbouts will
delete from right to left up to but not
beyond the beginning of the current line.

Table 3-3 Input Commands (Cont'd)
Command

Format
#R

Action and Explanation
Read a page of text from the input file on
the specified unit drive. The EDITOR will
read information from the input file until
a
form feed character
(CTRL/FORM key
combination)
is detected or until the
EDITOR
senses
a
text
buffer
full
condition. All incoming text except the
form feed is appended to the contents of
the text buffer.
Information already in
the buffer remains there.
NOTE
In both these commands,
the
EDITOR ignores ASCII codes 340
through
376.
These
codes
include the codes for the lower
case alphabet
(ASCII 341-372).
The EDITOR returns to command
mode only after the detection of
a form feed or when a buffer
full condition is reached.

3.6.2

Output Commands

Output commands are subdivided into 1is·t and text transfer commands.
List commands will cause the printout of all or any part of the
contents of the text buffer to permit e:Kamination of the text.
Text
transfer commands provide for the output of form feeds, corrected
text, or for the duplication of pages of an input file.
List or text
transfer commands do not affect the con'tents of the buffer.

List Commands
The commands in Table 3-4 cause part or all of the contents of
text buffer to be listed on the console terminal or line printer.
Table 3-4 List Commands
Command

Format

Action and Explanation

LIST the entirl:! page.
This causes the
EDITOR to list the entire contents of the
text buffer on the console terminal.

#nL

LIST line n.
followed by
feed.

3-10

This line will be printed
a carriage return and a line

the

Table 3-4 List Commands (Cont I d)
Action and Explanation

Command

Format

im,nL

LIST lines m through n
console terminal.

inclusive

the

List the entire text buffer on
printer (if one is available) •

the

line

inV

List line n of
printer.

the

line

im,nV

List line m through
line printer.

the

buffer
n

inclusive

The EDITOR remains in command mode after a list command, and the value
of the current line counter is updated so as to equal the number of
the last line printed.

Text Transfer Commands
The
The following commands control the output: of text and form feeds.
EDITOR
is designed to m1n1m1ze the possibility of illegal or
meaningless characters being written into a source file: therefore the
codes 340-376 and 140-177, and most illegal
illegal
(nonexistent)
control characters will not be output.
Table 3-5
Command

Format

Text TransfE!r Commands
Action and Explanation

Output the current buffer to the output
file and transfer all input to the output
file: close the output file.

Transfer the entire contents of
buffer to the output buffer.

inP

Transfer line n only to the output buffer.

im,nP

Transfer lines m through n
inclusive
(where m must be less than n) to the
output buffer.
When the output buffer
becomes full, the text is output to the
indicated output file.
The P command
automatically outputs a FORM character
(214) after the last line of output.

Transfer the contents of the text buffer
to the output buffer, delete the text
buffer and read in the next logical page
of text from thE! input file.

3-11

the

text

Table 3-5
Command

Format

inN

Text Transfer Commands (Cont'd)
Action and Explanation
Execute the above sequence n times. If n
is greater than the number of pages of
input text, the command will proceed in
the specified sequence until it reads the
end of the input. file, then it will return
to command modle.
The N command <cannot be used with an empty
text buffer.
A? is printed if this is
attempted.

3.6.3

Immediate end·-of-file.
The Q
command
causes
the lentire text buffer to be
output. All text written into the output
buffer is then written into the output
file and the file closed, with control
returning
to
the
Cassette
Keyboard
Monitor.

Editing Commands

The following commands permit deletion, alteration,
text in the buffer.

expansion

Table 3-6 Editing Commands
Command

Format

Action and Explanation

List the n~ber of
available
memory
locations in the text buffer. The EDITOR
returns the number of locations on the
next line.
Iro es timate the number of
characters tha"t can be accomodated in this
area,
mUltiply
the
number
of free
locations by 1.7.

inC

Change line n. Line n is deleted, and the
EDITOR enters text mode to accept input.
The user may now type in as many lines of
text as he desires in place of the deleted
line. If more than one line is inserted,
all subsequent lines will be automatically
renumbered and the line count will be
updated
appropriately.
A
CTRL/FORM
terminates the command.

#m,nC

Change lines m through n inclusive (m must
be numbered lless the n). Lines m through
n are deleted and the EDITOR enters text
mode allowing the user to type in any
number of lines in their place.
All
subsequent lines will be automatically

3-12

Table 3-6 Editing Commands (Cont'd)
Command

Action and Explanation

Format

renumbered to account for the! change
the line count wi 11 be updatE!d.

and

After any Change operation, a return to
command mode is accomplishE!d by typing a
CTRL/FORM. After a Change, t:he value of
the current line counter (.) is equal to
the number of the last line input. The C
command utilizes the Text Collector in
altering text (see Section 3.7).

'nD

Delete line n. Line n is removed from the
text buffer. The current line counter and
the numbers of all succeeding lines are
reduced by one.

im,nD

Delete lines m through n inclusive.
The
space used by the line to be deleted is
reclaimed as part of the Delete function
(refer to Section 3.7, Text Collection).

Used during a string search.
Find the
next occurrence of the string currently
being searched for
(see SE!ction 3.8.2,
Inter-Buffer Character Strinq Search).

Get and list the next line which has a
label associated with it.
(A label in
this context is any line of text which
does not begin with a spacE~, slash, TAB,
or RETURN). The EDITOR begins with the
line following the current l:.ne (line .+1)
and tests for a line with a label.
This
will most often be a line beqinning with a
tag; it might also be a line containing an
origin. For example:
TAD
DCA
ITHIS IS A COMMENT

H~R~,

(This is
line)

the

current

(This line would be
printed by the command
G)

TAD
ISZ;

(This line would also
be prin1:ed if another
G were typed)
G

tnG

Get and list the next line which begins
with a label; the EDITOR beqins at line n
and tests it and each succeeding line as
described in the preceding e:{ample.

3-13

Table 3-6 Editing Commands (Cont'd)
Conunand

Format

Action and Explanation

Both G and nG update the current line
counter after finding the specified line.
However, if ei 1:her version of the GET
conunand reaches the end of the buffer
before finding il line beginning with an
ASCII character other than a tab, slash,
or space, the current line counter retains
the value it was assigned before the GET
was issued, and a ? is typed to indicate
that no tagged line was found. The EDITOR
remains in con~and mode after a
GET
command.
I

In!

Insert the typed text before line n until
a form feed
(CTRL/FORM) is encountered.
The EDITOR enters text mode to accept
input.
The first line typed becomes the
new line n. Rubouts are recognized. Both
the line count: and the numbers of all
lines
following
the
insertion
are
increased by the! number of lines inserted.
The value of the current line counter is
equal to the number of the last line
inserted. To re!enter conunand mode, the
CTRL/FORM key combination must be typed
(terminating te>:t mode). If this is not
done, all subsequent commands will be
interpreted erroneonusly as
text
and
entered in the! program inunediately after
the insertion.

Insert text before line
wi thout an argument).

Initiate an inter-buffer string search
(See Section 3.8.2, Inter-buffer Character
String Search).

Kill (delete)
the entire page in the
buffer.
The
values
of the special
characters (/) cLIld (.) are set to zero.
The EDITOR remai.ns in conunand mode.

(when

NOTE
The EDITOR ignores the commands
nK or m,nK. This prevents the
buffer from accidently
being
destroyed if the user intended
to type a I,ist command (m,nL).

3-14

used

'rable 3-6 Editing Commands (Cont' d)
Command

Format

im,n$jM

Action and Explanation
Hove lines m through n inclusi vc~ to before
line j (m must be numerically less than n
and j may not be in the range between m
and n).
Lines m through n a.re deleted
from their current position
and
are
inserted before line j.
The lines are
renumbered after the move is completed
although the value of the current line
counter (,) is unchanged, as mO'/ing lines
does not use any additional bu::fer space.
(The $ character is produced by typing a
SHIFT/4. )
A line or group of lines may be moved to
the end of the! buf fer by spec:L fying j as
/+1. For example, 1,lO$/+lM. Since the
MOVE command re!quires three arquments, it
must have three arguments in order to move
even one line. This is done by specifying
the same line number twice. Fo::::- example,
5,5$23M.
This will move line !) to before
line 23. The EDITOR remains :Ln command
mode after a Move command.

3.7

inS

Search line n for the character specified
after typing the S and a carriage return.
Allow modification of the line when the
character is found.
(See Section 3.8.1,
Single Character String Search~)

inY

Skip to a logica.l page in the input file,
without writing any output. For example,
#5Y..
This command reads through 4
logical pages of input, deleting them
without producing output. The ::ifth page
is read into the text buffer ~md control
automatically returns to command mode.
If
there are no more pages of input, the
EDITOR issues a ? and returns 1:'0 command
mode.

i$TEXT"
#$TEXT'
#"

Perform a chara.cter string search for the
string TEXT (see section 3.8 .. 2, IntraCharacter
String
Search).
Buffer
Following a string search, #" causes a
search for the next occurrenGe of the
string.

TEXT COLLECTION

The CAPS-8 EDITOR contains an automatic text collector which reclaims
buffer space following the use of a D, S, or C command.
If a full

3-15

buffer condition is reached, the user may output lines of text
(using
the P command,
for example), and the,n delete these lines from the
buffer--text collection is automatic and. always occurs on the three
commands mentionE~d above.
NOTE
If extremely large amounts of 1:ext are deleted,
the text collection process could take several
seconds.
For
small
amoun.ts
of
text,
no
appreciable time is lost.

3.8

CHARACTER SEARCHES

Two types of searches were mentioned in Table 3-6--the standard
character search and the character string search. Each is explained
in turn.

3.8.1

Single Character Search

The single character search may take one: of the following forms:
#S
or
inS
or
im,nS
where m and n represent line numbers (m<n), and S initiates the search
command. This command searches the enti.re text buffer (or the line(s)
indicated) for the search character. The search character is typed by
the user after he types the RETURN key which enters the command, and
does not echo on the teleprinter.
The EDITOR prints the contents of
the entire buffer or the indicated linE!(s) until the search character
is found. When the se:arch character is found, printing stops and the
user types a response chosen from the following table:
Table 3-7 Search Character Options
Option
text

CTRL/G

Result
Enter text: at that point at which
the search character was found and
printing stopped.

(bell rings)

Change the search character to the
next
character
typed:
search
continues.
If the character is not
contained
in
the
line,
the
remainder of the line will be typed
and control will be returned to
command mode.
(For example, CTRL/G
CTRL/G would cause the remainder of
the line to be lis ted. )

3-16

Table 3-7

Search Character Options (Cont'd)

option

3.8.2

Result

CTRL/FORM

Continue searching for the
occurrence of the charactHr.

RETURN key

End
line
here,
dele1:ing
subsequent text on that l:.ne.

all

LINE FEED kE!y

Make two lines out of thE! current
line.
Typing a line feed actually
inserts a carriage return without
returning control to command mode.

RUB OUT key

Delete cha.racters from the line. A
rubout echoes a backslaBh (\) for
each chara.cter deleted.
When all
characters
have
been
deleted,
echoing of "\" stops.

Character String Search

The character string search can identi~y a given line in the buffer by
the contents of that line or any un~que combination of characters.
This search returns the line number as a. parameter that can be used to
further edit the text.
There are two types of string search
available: intra--buffer search and inter-buffer search.

Intra-Buffer Character String Search
The intra-buffer search scans all text in the current buffer for a
specified character string.
If the string is n01: found, a ? is
printed and control returns to command mode.
If the string is found,
the number of the line which conta.ins the string :Ls put into the
current line counter and control waits for the user to issue a
command.
Thus, searching for a cha.racter string in this manner
furnishes a line number which can then be used in conjunction with
other EDITOR cormnands. This provides a. useful framework for editing,
as it eliminates the need to count lines or search for line numbers by
listing lines.

An intra-buffer search is signalled by typing the ALT MODE key (which
echoes as $)
in response to the i printed by the EDITOR. The user
then types the string to be found (as ma~ny as 20 characters may be
specified--any additional characters typed are echoed but not included
in the search). The search string calnnot be broken across line
boundaries.
Typing a single quote
(')
terminates the character
string; when the RETURN key is typed the! search is performed beginning
at line 1 of thE! text buffer. Use of t:he double quote (") causes the
search to begin at the current line +1.
(Use of 'and n as command
elements prohibits their use in the: search string,. An incorrect
response resets the current line counter to the be9inning of the
buffer. )

3-17

For example, assume the text buffer contctins the following text:
ABC DEF' GJO
lA283C4D5E6
.STRINGABCD

The user wants to list the line that cont:ains ABC; this could be
by typing:

done

~$ARC'L

The search begins with line 1 and continues until the string is found.
The current line counter is set equal to the line in which the string
ABC occurred, and the L command causes t:he line to be printed as
follows:
ARC DEF' llJO

Control returns to command mode, awaitinq further commands.
user wanted to find the next reference tel ABC, he could type:

the

In this case, " is a command which causes: the last string searched for
to be used again, with the search beginning at the current line +1.
It is not necessary to enter the search string again. The command may
be used several times in succession. For example, if the user wanted
to find the fourth occurrence of a string containing the characters
FEWMET he could type:
IS F'EINl-:ET' .. "' .. L

This command lists the line which contains the fourth occurrence of
that string. The L (List) command (or aLny other command code) can be
given following either • or"
The L command causes the line to be
listed when and if it is found.
In order to clear the text string buffer, the user can type:
#$'

The system responds with a question mark and the text string buffer is
cleared.
The properties of the commands I and " allow for easy and useful
editing, as the following example illustrates. In order to change CIF
20 to CIF 10, the user can issue the following commands:

3-18

#$ D'JM" , $C IF 20 ftC
elF 10
/I'vE W F I ~LD (CTRL/FORM)

The above set of instructions first causes the EDITOR to start at line
1 and search
for a line beginning with DUM,. A search is then made
for CIF 20, starting fror.1 the line af1:er the line containing the
string DUM,. When this string is found, the line number of the line
containing the string CIF 20 becomes thE~ current line number.
The C
command is gi ven, and the user then c::hanges the line to the correct
instruction, CIF 10 /NEW FIELD •
Since this search feature produces a line number as a result, any
operations which can be done by explicitly specifying a line number
can be done by specifying a string instE~ad. For example:
#$STQING'+4L

will list the fourth line after
STRING in the text buffer.

the

first

occurrence

the

text

1$ LABEL 1" • " LABEL?" "L

will list all lines between the two labeds, inclusive.
#$PFLfTG'S

will do a characit.er search on the line which contains PFLUG.
(The
user types the search character aft:er typing the :RETURN key that
enters the line.)
In cases where both strings and explicit: numbers are used,
'should be used first.
For example, the following commands:

strings

#l+$RAD! 'L

will not list th«~ next line after the st:ring BAD! occur::;.
syntax is:

The correct

#$BAD!'+lL

Inter-Buffer Character String Search
The inter-buffer search scans the current text buffer for a character
string.
If the string is not found, the current buffer is written to
the output file, the buffer is cleared, and the next buffer is read
from the input device. The search them resumes at line 1 of the new
buffer. This process continues until either the string is found or no
more input is le:Et.
If input is exhaust:ed, control returns to command
mode with all th«~ text having been writt:en to the outpU": file.
If the
string is found, control returns to command mode with the current line
equal to the number of the line containing the first oCI::urrence of the
string. For example, a command to find the character s'tring GONZO may

3-19

appear as follows:
IJ

$llONZO'

I. =vH~24
~

The J command initiates an inter-buffer search; the $ is printed
automatically by the EDITOR, and the user types in the character
string he wishes to search for. The search proceeds, and when the
string is found, control returns to command mode. The user types the
.= construction to discover the number of the line in the current
buffer on which the string is contained. To find further occurrences
of the string GONZO, the user can use the F conunand.
The F command
uses the last character string entered to search the buffer starting
from the current line count +1.
#F'

#.=0106
-

The above example causes a search for the string GONZO starting at the
current line +1.
If no output file is specified in the J or F
commarids, the EDITOR reads the next input buffer without attempting to
produce any output. This provides an E!asy way of paging through text
for a particular string.
After the J or F commands have processed the entire input file,
or Q command must be executed to close t:he output file.

The following two comnlands may be used
command, once given:

abort

the

string

Table 3-8 Terminating a String Search
Command
CTRL!U

Explanation
A CTRL!U will return control to the
EDITOR conunand mode if executed while
entering text in
a
string
search
command; the string search conunand is
ignored, as in the following example:
#J
$WORD ffJ
II

The
inter-buffer
search
for
the
characters WO:RD was aborted by the user
typing tU before terminating the string
with ' or n
RUB OUT

Executing the RUBOUT key while entering
text for use in a string search causes
the text so far entered to be ignored
and allows a new string to be inserted.
The EDITOR anS'rlers the command by typing

3-20

Table 3-8

Terminating a String Search (Cont'd)

Command

Explanation

$, as seen in the following example:
(RUBOUT)
An example of the use of the character s'tring search is

contained
the EDITOR Demonstration Run found at thle end of this chapter.

3.9

EDITOR ERROR MESSAGES

Errors made by the user while running thie EDITOR may be of two types.
Minor errors (such as an EDITOR command string error, an attempt to
execute a read oz' write command without assigning a device, or
a
search for a nonexistent string) will cause a question mark to be
typed at the left margin of the teleprin'ter paper. The command may be
retyped.
Major errors force control to return to ·the Keyboard Monitor and may
be due to one of the causes listed in Table 3-9. These errors cause a
message to be typed in the form:
?ntC
where n is one of the error codes i.n Table 3-9 and tC indicates that
control will pass to the Keyboard Monitor when a character is typed.

Table 3-9 EDITOR Error Codes
Error Code

Meaning

The EDITOR failed in reading from a
device. An error occurred in the device
handler;
most
likely
a
hardware
malfunction.

The EDITOR failed in
device;
generally
malfunction.

A file close error occurred. The output
file could not be closed; either the
cassette
reached
an
end-of-tape
condition, or a sentinel file needs to
be written before any new output files
can be created on the cassette.

3-21

writing onto a
a
hardware

A ? occurs any time the EDITOR encounters a syntax error.
In
addi tion, the following error message m,ay be printed by the EDITOR:
Me,aning

Message
UNIT HAS OPENED FILE

Two files cannot be open on the same
device at the same time.

During the editing of a file, the outpu-t cassette specified in the
command string may become full before the editing process
is
completed. If this is the case and further writing is attempted on
that cassette, an error occurs. Thl3 output file is closed and the
message:

FULL.OUTPUT FILEis printed. The user must now indicate a new output cassette and file
which will contain the text that would not fit on the first cassette
and any further editing the user wishes to do. Since the contents of
the text buffer are retained through -this procedure, no text will be
lost if this error occurs.
NOTE
If no output file is spe,e:ified when this
condition
occurs,
th,e EDITOR again
requests an output file; this continues
until
the
output
designation
is
correctly specified.
Assuming the new output device is valid, the EDITOR will continue the
operation which filled the old file, putting all output into the new
output file. After editing is completed, the output files should be
combined using the EDITOR.
The entire process may then appear as
follows:

....R EDIT
*INPUT FILE-0:IN
*OUTPUT FILE-I: OUT
IY

$STRI NG'
FULL *OUTPUT FILE-2:0UTEMP
l·L
TAD STRING

Device 1: is full.
2: is specified as the
new output device
and editing continues.

3-22

At this point the output "file" is 2 files--l:OUT, 2:0UTEMP.
When
output is split like this, the split may have occurred in the middle
of a line.
Therefore, the output files should never be edited
separately as the split lines will then be lost. In a case such as
this, the files should be combined with the EDITOR as follows:

.R EDIT/M
*INPUT FILE-l:OUT
*OUTPUT FILE-3:0UT
IE
~INPUT FILE-2:0UTEMP
*1 NPUT FILEThe new file, OUT, may then be edited.

3-23

3.10

EDITOR DEMONSTRATION RUN

The following ,=xample illustrates both the use of the EDITOR to create
a new file and a few of the commands available for editing. Sections
of the printout are coded by letters which correspond
with the
explanations following the example.

{ .R EDIT

*1 NPUT FILE*OUTPU T FI LE-.0: P ROG. PA L

tA
{CHRPUT' SNA
0
B

(

{

{~.- 35
t·l

JMP I CHRPU T
CDF 0
DCA SHELF
TAD WI \HAT 1
SPC
JMP PUTII
SNA CLO
JMP PUTI2
CMA
DCA lNH AT 1

IACCEPTS CHAR IN AC AND
IPACKS IT INTO OUTPUT BUFFER
II GNORES NULL

SNA CLO\A
SNA ClA

C
P

.!K

!.A

TAD SHELF
AND (360
ClL RTL

{

.R EDIT
*INPUT FIlE-0:PROG.PAL
{ ~OUTPUT FILE-l:PROG.PAL

'R
{ .l$SPC'L

SPC
SPC\A

3-24

The user calls the EDITOlt; the output
file will be called PROG.PAL and will be
stored on the default dE!vice--cassette
drive O.
There is no input file since
one will be created from the console
terminal keyboard.
The Append command
is used to insert text into the empty
buffer.

Text is inserted.

The user makes a mistake
RUBOUT key to correct it

More text is added.

The user n.otices a typing mistake he has
made several lines back in the text. He
types a CT'RL/FORM to finish the Append
command,
searchs
for
the
illegal
character, corrects it, and then lists
the line.

The P command writes the c:::urrent buffer
into the cmtput file plac:Lng a form feed
after the last line.
~rhe
K command
deletes all text in the current buffer
in preparation for a new page of text.

The user inserts new t4~xt using the
Append command. When he is finished he
types a C'1 RL/FORM to end t.he command.

and

uses

the

file;
The user closes the
CaSS4:!tte
to
the
returns
Monitor.

In lookin9 over the listing, the user
notices another mistake~ he opens the
file, calling it by the same name in
both the input and output: specification
lines.

The Intra-Buffer Character String Search
is
used
to
locate
the
illegal
instruction and list it.

The Single Character Search is used to
find the letter to be corrected, and the
RUBOUT key deletes it.

The file is closed and control
returns to the Keyboard Monitor.

3-25

control
Keyboard

again

CHAPTER 4
SYSTEM COPY

4.1

INTRODUCTION

The CAPS-8 System Copy (SYSCOP) program allows the user to copy
individual files or all files from one cassette to another, giving him
the ability to make mUltiple copies of a cassette, add files to a
cassette, and "clean up" full cassettes so that they may become
available for future use. System Copy transfers all non-empty files
on the specified input cassette to the specified output cassette;
space taken up by previously deleted files (*EMPTY files) is regained.
(Single file transfers of ASCII files can be performed using the
CAPS-8 EDITOR; see Chapter 3.)

4.2

CALLING AND USING SYSTEM COpy

To call SYSCOP from the System CassettE!, the user types:
.R SYSCOP/Options
in response to -the dot (.) printed by t.he Keyboard Monitor.

4.2.1

System Copy Options

There are three options available for use with System Copy; these
options are discussed in Table 4-1..
(Option usage is explained in
Chapter 2, Section 2.4.3.)
Table 4-1 System Copy Options
Option

Meaning

This option allows the user to transfer
individual
cassette
files from one
cassette to anothE!r.
To use the /F
option, the user rE!sponds to the request
for
input
specification
with
the
cassette drive number and the name of
the file to be copied.
If the user
makes a typing error while entering the
input specification, he can type CTRL/U
to redo the entry.

If the /U option is specified, drive 1
is zeroed and then drive 0 is copied to
drive 1.
(The /U option is especially
useful for makin9 copies of the System
Cassette.) When thE! /U option is used,
no
further
I/O
specifications are
necessary.

This option caUSE~S the output drive
(indicated in thE~ output specifi,::ation
line) to be zeroed before any c()pying
begins.

4-1

4.2.2

Input and Output Specifications

Before indicating the input and output drives to be used for the copy
operation, the user must ensure that the proper cassettes are mounted.
The input cassette (the one to be copied) should be write-locked to
protect the data. The output cassette (the one that will be the new
copy) should be write-enabled to receive the data. When the input and
output cassettes are mounted on the correct drives, the user is ready
to begin the copy operation.
After SYSCOP has been called from the System Cassette, it asks for the
input specification as follows:
I N-

The user responds with a single digit (0 through 7) specifying the
input cassette drive number. A carriage return is not necessary.
If
the IF option was used, the user responds to the IN- query with the
drive number and the name of the file to be copied; in this case, the
user must also type a carriage return.
In the following example, a
file named ECHO is to be copied from drive 1.

IN-:ECHO
After the input specification has been entered, System
the output specification as follows:

Copy

requests

The user responds with a single digit (0 through 7)
specifying the
output drive number.
The output drive number cannot be the same as
the input drive number.
If the user wishes to change the input/output
specifications at this point, he may type a carriage return instead of
the drive number after OUT- to return to the IN- message.
After both input and output drives have been indicated, the copy
operation starts.
All non-empty files on the input cassette are
copied, in order, onto the output cassette.
(If a file is to be
copied onto a cassette under the same filename and extension as one
already present on the cassette, it will still be copied; however,
future reference to the file will cause the first file under that name
to be accessed. To circumvent this condition, the user should first
delete any old files or zero the output cassette.) t~en all files have
been copied, control returns to the Keyboard Monitor.

4-2

Only two responses other than the digits 0 through 7 are accepted in
reply to the input/output specification messages: carriage return and
CTRL/C. Carriage return returns the US4~r to the input specification
message; CTRL/C returns the user to the Keyboard Monitor. Any other
response is considered illegal.
Illegal responses are
neither
accepted nor echoed by System Copy; System Copy simply waits for the
user to type a legal response.

4.2.3

System Copy Example

In this example, the user wishes to mak4~ a copy of the Sys tern Cassette
which is mounted on drive O. One purpose of the copy operation is to
regain wasted space being taken up by previously deleted files.
A
directory listing shows that the System Cassette currently contains
the following files
C2BOOT.BIN 01/22/73
MONTOR.BIN 01/22/73
SYSCOP.BIN 01/25/73
*EMPTY.
EDIT
.BIN 01102/73
PALC
.BI N 01/02/73
BASIC .BI N 01/~2/73
*EMPTY.
*EMP TY •
*EMPTY.
*EMP TY.
ABC
01/22/73

The user mounts a write-enabled cassetb~ on drive 2
tape. He than calls System Copy as follows
~R

and

rewinds

the

SYSCOP IZ

The /Z opti?n will zero the cassette mounted on the cassette drive
specified 1n the OUT- message (drive 2), leaving only the sentinel
file on the cassette. System Copy then requests the input and output
drive numbers and the user responds as .follows:

The copy operation starts. If System Copy detects any problems during
the copy opera.tion, it prints one of the error messages explained in
Section 4.3. A successful copy operation returns control to the
Keyboard Monitor.
The user can then issue a DIrectory command to
ensure that all files were copied correctly.
In this example, a
successful copy operation should produce the follm.,ing directory
listing:
C2BOOT.BIN
MONTOR.BIN
SYSCOP.BIN
ED IT
.B IN
PALC
.BIN
BASIC .BIN
ABC

01/22/73
01/22/73
01/25/73
01/02/73
01/02/73
01/02/73
01/22/73

4-3

4.3

SYSTEM COPY ERROR MESSAGES

Errors which occur during a System Copy operation may be of two types:
user errors and cassette errors. Use:r errors may be corrected with
the appropriate action as detailed in Table 4-2.
Cassette errors
normally require the user to use another cassette (for either input or
output) to complete the copy operation. Control does not return to
the Keyboard Monitor when a System Copy error occurs. The user may
use CTRL/C to return to the Monitor if he cannot correct the indicated
error.
Table 4-2 System Copy Error Messages
Message

Meaning

INPUT ERROR ON UNIT n

An input error has occurred on

the
cassette drive specified. The user
should try the copy operation using
another cassette.

UNIT n NOT READY

There is either no cassette on the
cassette drive specified or no such
drive exists.

UNIT n WRITE LOCKED

The user tried to write data when
the
write
protect tab of the
cassette on the drive specified was
write-locked.

OUTPUT ERROR ON UNIT n

An output error has occurred on the
cassette drive specified. The user
should try the copy operation using
another cassette.

4-4

CHAPTER 5
PALC

5.1

INTRODUCTION

PALC (an acronym for Program Assembly Language for Casse:tte) is an 8K
2-pass assembler (with an optional third pass) designed for the CAPS-8
System. A program written in PALe sourcle language is translated by
the assembler into a binary file in two passes. Pa.ss I reads the
input file and sets up the symbol table; pass 2 reads the input file
and uses the symbol table created in pass 1 to gene~ate the binary
(object) file. The binary file may then be loaded into memory using
the Cassette Keyboard Monitor.
PALC allows I/O using any CAPS-8 device ~,.,hich handles ASCII text.
It
is called from the System Cassette using the Keyboard Monitor Run
command, accepts input generated by the CAPS-8 EDITOR, and will
generate output acceptable for use with both the Moni tc,r Load and Run
commands.

5.2

CALLING AND USING PALC

The user calls PALC from the System Cassette by typing:
.R PALC/Options
PALC responds by printing:
-INPUT FILES
..!...

The user enters his input cassette drive number and filename in answer
to the asterisk printed by PALC; a total of three input specifications
are allowed, so that the input interacti()n may appear as follows:
-INPUT. FILES
*l:TRA.PAL
i0 zTRB .PAL
,.!11 THe .PAL

Usually input files will contain the extension .PAL (see Chapter 2,
Section 2.2.2), and PALC will assume 1:his extension unless the user
explicitly designates another. Thus in 1:he above example the user may
have responded by typing only I:TRA, O:TRB, and I:TRC, in which case
PALC would automatically assume and echo the .PAL extension.
If the filename contains an extension other than .PAL, the user
specify this extension when entering the input. For example:

-INPUT FILES
..!.lIFAIL.l
i2ITABLE.ASC.
~zSHOR.

5-1

must

In the case of the third input file (SHOR.) an extension is not to be
indicated.
If the user wants to prevent PALe from assuming .PAL, he
must be sure to include a period in the input line; otherwise PALC
will append .PAL a.nd look for the filename with that extension.
If the user does not specify a drive number in his input line, the
default device--drive O--is assumed. PALC will automatically insert
0: in the input line before echoing the filename as the user has
entered it. For I~xample:
*0: FLOA .PAL

The user actually typed only the charactE!rs FLOA; PALC assumed both
the drive number 0 and the .PAL extension and correctly inserted these
in the I/O line before echoing the complE!te line.
A carriage return typed in response to any of the asterisks
that there are no more input files.
After the input specifi.cations have been entered,
binary output as follows:

PALC

indicates

requests

the

-BINAH.Y FILE

..!.

The user responds similarly here by indicating an output drive number
and filename. Only one binary file is allowed and it should have the
extension .BIN (since the Monitor Run and Load commands assume this
extension).
If the user wants his binary file to be called by the
same name as the first input file he need only type the drive number,
a colon, and a. carriage return.
Pl~C will echo this, adding the
filename with a .BIN extension. For example:
-INPuT F'ILES
~l :OPEN.PAL

-8 I NAR Y FILE_
..!0:0PEN.BIN

As in the input line, drive 0 and the extension (.BIN) are assumed if
the user fails to specify them, and a response of only a carriage
return indicates that no binary file is to be produced.
Once the binary output line has been ans\Olered, PALC prints:
-LIST TO

*
The user has a choice of sending his output listing to either the
console terminal or the line printer. To send output to the console
terminal the user types the characters TTY in response to the asterisk
as follows:
-LIST TO
..!.ITY

5-2

To send output to the line printer, the user responds by typing LPT:

-LIST TO
~LPT

A response of a carriage return indicates that no
produced.

listing

During a PALC assembly only one listing is produced and :it may be sent
to only one device, either the line printer or consoll~ terminal. A
second listing must be produced by anothe!r assembly.
If more cassettes are to be involved in t:he assembly than the user has
TU60 unit drives, a certain procedure must be follml7ed during the
assembly process. For example, assume the user has only one TU60 dual
cassette unit, and 3 input files are s t:ored on individual cassettes.
His I/O specification is as follows:

-INPUT FILES
*l:Fl.PAL .:!0:F2.PAL
*0:F3.PAL
-=BINARY FILE
*l:RESLT.BIN
-=-LIST TO
~LPT

PALC is a 3-pass assembler, therefore all three input files will be
referenced 3 times. Assume the user has. mounted 1:Fl.P1U, on drive 1,
and 0:F2.PAL on drive 0: assembly begin.s.
First the file Fl is
processed, then F2. After assembly of F2 PALC looks for F3, but since
the file is on a t:hird cassette which is not mounted, the assembly
pauses and PALC prints:

This pause in the assembly allows the user to dismount a cassette and
replace it with the cassette containing the file F3.PAL. The user
then responds to t:he above I/O line with the drive number on which he
has mounted the nE~W cassette (assume 0), as follows:

MOUNT F3.PAL'?0
If the response is valid, PALC responds by typing a CR/LF and
continues pass 1 of the assembly.
(An in.valid response Gauses PALC to
print a ?: the USE!r may then type the correct response.)
When pass 1 is completed PALC automatically begins the second pass,
which creates the binary file.
The binary output file specification
must now be made. Regardless of the output specification indicated in
the initial dialo9ue, PALC pauses and asks:

MOUNT rtESLT.BIN1

5-3

The user must mount the output cassette which is to contain the binary
file and respond with the drive number on which he has mounted it.
Assume he decides to mount the cassette on drive O. He replaces the
cassette currently on that drive
(c:ontaining F3.PAL) with the new
cassette and responds to the conunand line as follows:
MOUNT RESLT.BIN?0
PALC then opens the binary file on this cassette and prints:
BINAHY FILE OPENED ON 0
NOTE
The cassette used for binary output may
not contain any of the input files.
Under no
circumstances:
should
the
cassette containing thE! binary file be
removed from the drive until pass 2 is
completely finished.
PAI,C will indicate
completion of the pass by printing the
message, "BINARY FILE CLOSED".
After specification of the binary output~ file, PALC continues pass 2
of the assembly by processing the first: input file, Fl.PAL, currently
on drive 1. After this file is process€!d, PALC pauses and asks:
MOUNT F2.PAL?
Since the binary file being created on drive 0 is only partially
complete at this point, the user must not remove the cassette from
that drive.
He must instead remove the cassette from drive 1 and
replace it with the cassette containi.ng F2.PAL.
He then types 1 in
response to the I/O line and assembly continues until F3.PAL is
needed.
PALC again pa,uses and asks:
MOUNT F3.PAL?
Again the user replaces the cassette on drive 1 with the appropriate
one, correctly answers the I/O line, and assembly continues.
Once pass 2 is done, pass 3--the listi.ng pass--must be processed.
Drive 0 may again be used for input, and assembly of input files
continues in the same manner as during passes 1 and 2.
The procedure of mounting and dismounting cassettes may be repeated as
many times as necessary until all input files are processed and the
desired output produced.
If an I/O error occurs during any of the
three passes or if an output casset~te becomes full, the user must
restart the assembly beginning with pass: 1.

5-4

NOTE
When the assembly is complete, PALC
prints
tc (CTRL/C).
The user then
mounts the system cassette and types
CTRL/C to return to the Monitor.

5.2.1 PALC Options
Table 5-1 lists the options available in PALC which may
in the Monitor Run or Load specification line.
Option

5.3

Table 5-1 PALC Options
Meaning

Generate a DDT-compatible symbol t.able
(applicable only if a listing file is
specified).

Generate non-paginattad output.
Hea.der,
page
numbers
and
page format are
suppressed (applicable only if a listing
file is specified).

Used in assembling v 4ary large programs;
causes system containing 12K or more of
memory to use fields 2 and up as symbol
table storage.

Generate the symbol table, but not the
listing (applicable only if a listing
file is specified; the /H option is
assumed) •

Omi t the symbol tab14a normally generated
with the listing (,applicable only if a
listing file is specified).

Output a carriage return/line feed in
place of the form .feed character (s) in
the program (appli'cable only
if
a
listing file is specified).

CHARACTER SET

The following characters are acceptable .as input to PALe:
1.

The alphabetic characters: A through Z

The numeric characters: 0 throu9h 9

The characters described in following sections as
special characters and operators

5-5

indicated

Characters which are ignored during assembly such
as LINE: FEED, FORM FEED, and RUB OUT

All other characters are illegal (except when used in a
cause the error message:

comment)

and

IC AT nnnn
to be printed during pass 1; nnnn represents the location at which the
illegal character occurred.
(As assembly proceeds, each instruction
is assigned a location determined by the current location counter (see
section 5.7.3).
When an illegal character or any other error is
encountered during assembly, the value of the current location counter
is returned in the error message.) Illegal characters do not generally
cause assembly t:o halt.
If an illegal character occurs in the middle
of a symbol, the symbol is terminated at that point.

5.4 STATEMENTS
PALC source programs are usually prepared on the console terminal
(using the CAPS-8 EDITOR) as a sequence of statements. Each statement
is written on a single line and is terminated by typing the RETURN
key.
There are four types of elements in a PALC statement which are
identified by the order of their appearance in the statement and by
the separating (or delimiting) character which follows or precedes the
element. These are:
label,

instruction

operand

/comment

A statement must contain at least one of these elements and may
contain all four types. The assembler interprets and processes the
statements, generating one or more binary instructions or data words,
or performing an assembly prpcess.

5.4.1

Labels

A label is the symbolic name created by the programmer to identify the
location of a statement in the program.
If present, the label is
written first in a statement.
It must begin with an alphabetic
character, contain only alphanumeric characters, and be terminated by
a comma; there must be no intervening spaces between any of the
characters and t:he comma.

5.4.2

Instructions

An instruction may be one or more of the mnemonic machine instructions
or a pseudo-operation which directs assembly processing.
(Assembly
pseudo-ops are described later in this chapter; Appendix C summarizes
both the mnemonic machine instructions and pseudo-ops used by PALC.)
Ins tructions arE:! terminated with one or more spaces (or tabs if an

5-6

operand follows) or with a semicolon, slash, or
described in Sec1:ion 5.5.3.

5.4.3

carriaqe

return,

Operands

Operands are the octal or symbolic addresses of an assE~mbly language
instruction or the argument of a pseudo-operator, and can be any
expression.
In each case, interpretation of an operand depends upon
the instruction or the pseudo-op.
Operands are terminated by a
semicolon, slash, or carriage return.

5.4.4

comments

The programmer may add notes or comments to a statement by separating
these from the remainder of the line with a slash. Such comments do
not affect assembly processing or program execution but are useful in
the program listing for later analysis or debugging. The assembler
ignores everything from the slash to the next carriage return.
(For
an example see Section 5.5.3, Statement Terminators.)
It is possible to have only a carriage return on a line, resulting
a blank line in the final listing. No error message is given.

5.5

FORMAT EFFECTORS

The following characters are useful in controlling the format of an
assembly listingr •
They allow a neat r,eadable listing to be produced
by providing a me:ans of spacing through the program.

5.5.1

Form Feed

The form feed code causes the assembler to output blank lines in order
to skip to a new page in the output listing during pass 3; this is
useful in creating a page-by-page listin9. The form feed is generated
by typing a CTRL/L on the console terminal.

5.5.2

Tabulations

Tabulations are u.sed in the body of a source program to separate
fields into columns (for details refer ·to Chapter 3). For example, a
line written:

GO,TAD TOTAL/MAIN LOOP
is much easier to read if tabs are inserted to form:

5-7

5.5.3

IMAIN LOOP

TAD TOTAL

GO,

statement Terminators

The RETURN key is used to terminate a statement and causes a line
feed/carriage return combination to occur in the listing.
The
semicolon (;) may also be used as a statement terminator and is
considered identical to a carriage return except that it will not
terminate a comment. For example:

ITHIS IS A COMMENT; TAD R

TAD A

The entire expression between the slash (/) and the carriage return is
considered a comment. Thus in this caSE~ the assembler ignores the TAD
B.
If, for example, the user wishes to wri1:e a sequence of instructions
to rotate the contents of the accumulator and link six places to the
right, it might look like the following::

rlTH
RTrl
HTH
However, the programmer can alternatively place all three instructions
on a single line by separating thE~m with the special character
semicolon (;) and terminating the entirE~ line with a carriage return.
The above sequence of instructions can 1:hen be written:

These multi-statement lines are particularly useful when setting aside
a section of data storage for use during processing. For example, a
4-word cleared block could be reserved by specifying either of the
following:

LIST,

or
LIST~

o
o
o

Either format may be used to input data words (data words may be in
the form of numbers, symbols, or expres~;ions, explained next.) Each of
the following lines generates one storaqe word in the object program:

5-8

DATA.. 1111
A+C-B
5
123+82

5.6

NUMBERS

Any sequence of digits delimited by either a SPACE, TAB, semicolon, or
carriage return forms a number. PALC initally interprets numbers in
octal (base 8). This base can be changed to decimal using a special
pseudo-operator (discussed in Section 5.10.2). Numbers are used in
conjunction with symbols to form expressions.

5.7

SYMBOLS

A symbol is a string of alphanumeric characters beginning with a
letter and delimited by a non-alphanumeric character. Although a
symbol may be any length only the first six characters are recognized;
since additional characters are ignored, symbols which are identical
in their first six characters are considered identical.

5.7.1 Permanent Symbols
The assembler contains a table (called its permanent symbol table)
which lists the symbols for all PDP-8 pseudo-op codes, memory
reference instructions, operate and lOT (Input/Output
Transfer)
instructions.
These instructions are symbols which are permanently
defined by PALC and need no further definition by the user; they are
summarized in Appendix C. For example:
HLT

5.7.2

This
is
a
symbolic
instruction
assigned
the
value
7402 by the
assembler and stored in its permanent
symbol table.

User-Defined Symbols

All symbols not defined by the assembler (and represented in its
permanent symbol table) must be defined within the source program.
A symbol may be used as a statement label, in which case it is
assigned a value equal to the current location counter; it is called a
symbolic address and can be used as an operand or as a reference to an
instruction. Permanent symbols (instructions, special characters, and
pseudo-ops) may not be used as symbolic addresses.
The following are examples of legal symbolic addresses:
ADDR"
TOTAL"
.sUM"
AI ..

5-9

The following are illegal symbolic addresses:
AD>M ..
7ABC ..
LA BEL ..
D+TAG ..
LABEL ..

(contains an illegal character)
(first character must bE~ alphabetic)
(must not contain imbedded spaces)
(contains a legal but non-alphanumeric character)
(must be terminated by a comma with no
intervening spaces)

5.7.3 Current Location Counter
As source statements are processed, Pru~c assigns consecutive memory
addresses to the instructions and data words of the object program.
The current location counter contains the address in which the next
word of object code will be assembled cmd is automatically incremented
each time a memory location is assigned. A statement which generates
a single object program storage word increments the location counter
by one.
Another statement might generate six
storage
words,
incrementing the location counter by six.
The user sets or resets the location counter by typing an asterisk
followed by the octal absolute address value in which the next program
word is to be stored.
If the origin is not set by the user,
PALC
begins assigning addresses at location 200.

TAG,
B,
A,

*300
CLA
JMP A

/SET LOCATION COUNTER TO 300

DCA B

The symbol TAG (in the preceding example) is assigned a value of 0300,
the symbol B a value of 0302, and the symbol A a value of 0303.
If a
symbol is defined more than 40nce in this manner,
the assembler will
print the illegal definition diagnostic:
ID address
where address is the value of the location counter at the second
occurrence of the symbol definition.
The symbol is not redefined.
(For an explanation of diagnostic messages refer to Section 5.14 PALC
Error Conditions.) For example:

*3~~0

START,
CONTIN,
A,
COUNTER,
START,

TAD A
DCA COUNTER
JMS LEAVE
JMP START
-74

CLA CLL

5-10

The symbol START would have a value of 0300, the symbol CONTIN would
have a value of 0302, the symbol A would have a value of 0304, the
symbol COUNTER (considered COUNTE by the assembler) would have a value
of 0305.
When the assembler processed the next line it would print
(during pass 1):

IR CQUNTE+0001
Since the first pass of PALC is used to define all symbols, the
assembler will print a diagnostic during pass 2 if reference is made
to an undefined symbol. For example:
*7170

TAD C
CLA CMA

HLT
JMP A 1

The dollar sign must terminate
all PDP-8 assembly programs.

This would produce the undefined symbol diagnostic:

US A+0003

5.7.4

Symbol Table

Initially, the assembler's symbol table contains the mnemonic op-codes
of the machine instructions and the assembler pseudo-op codes as
listed in Appendix C; this is its permanent symbol table.
As the
source program is processed, user-defined symbols along with their
binary values are added to the symbol table.
The symbol table is
listed in alphabetical order at the end of pass 3.
During pass 1, if PALC detects that the symbol table is full (in other
words, there is no more memory space in which to store symbols and
their associated values), the symbol table exceeded diagnostic is
printed:
SE address
The assembler then prints t C and waits for a response from the user.
By typing t C the user can return control to the Monitor. If the
system contains more than 8K of memory, the user may choose the /K
option with the Run command (see section 5.2.1), or more address
arithmetic may be used to reduce the number of symbols.
It is also
possible to segment a program and assemble the segments separately,
taking care to generate proper links between the segments.
(See
Section 5.11.) PALC's symbol capacity is 768 symbols. The permanent
symbol table contains 69 symbols, leaving space for 699 possible
user-defined symbols. Each additional 4K allows 768 new symbols.
Section 5.10.12 provides instruction.s concerning altering PALC's
permanent symbol table should the USE!r wish to add instructions more
suited to his programming needs.

5-11

5.7.5

Direct Assignment statements

The programmer may insert new symbols with their assigned values
directly into the symbol table by USin9 a direct assignment statement
of the form:
SYMBOL=VALUE
VALUE may be a number or expression. No spaces or tabs may appear
between the symbol to the left of thE~ equal sign and the equal sign
itself. The following are examples of direct assignment statements:

A=6
EXIT=JMP I 0
C=A+B
All symbols to the right of the equal si.gn must be already defined.
The symbol to the left of the equal sign is subject to the same
restrictions as a symbolic address, and its associated value is stored
in the user's symbol table.
The use of the equal sign does not
increment the location counter: it is, rather, an instruction to the
assembler itself.
A direct assignment statement may also E!quate a new symbol to the
value assigned to a previously defined symbol.
In this case, the two
symbols share the same memory location.

8ETA=17
GAMMA=BETA
The new symbol, GAMMA, is entered into the user's
the value 17.

symbol

table

with

The value assigned to a symbol may be changed as follows:

ALPHA=5
ALPHA=7
The second line of code shown changes the value assigned to ALPHA from
5 to 7.
(This is legal but will generate an RD error message,
explained below.)
Symbols defined by use of the equal sign may
expression. For example:

A=100
B=400
A+B
TAD A

used

any

valid

IDOES NOT UPDATE CLC
IDOES NOT UPDATE CLC
ITHE VALUE 500 IS ASSEMBLED AT LOC. 200
ITHE VALUE 1200 IS ASSEMBLED AT LOC. 201

If the symbol to the left of the equal sign has already been
the redefinition diagnostic:

defined,

RD address
will be printed as a warning, where address is the value of the
location counter at the point of redefinition. The new value will be

5-12

stored in the symbol table; for example:
CLA=7600

will cause the diagnostic:
RD +0200

Whenever CLA is used after this point, it will have the value 7600.

5.7.6

Symbolic Instructions

Symbols used as instructions must be pr,edefined by the assembler or
the programmer.
If a statement has no label, the instructions may
appear first in the statement and must be terminated by a space, tab,
semicolon, slash, or carriage return. The following are examples of
legal instructions:
TAD

PAGE
ZIP

5.7.7

(a mnemonic machine instruction)
(an assembler pseudo-op)
(an instruction defined by the user)

Symbolic Operands

Symbols used as operands normally have a value defined by the user.
The assembler allows symbolic referlences to instructions or data
defined elsewhere in the program.
Operands may be numbers or
expressions. For example:

TOTAL, TAD ACI + TAG
The values of the two symbols ACI and 'TAG (already defined by the
user)
are combined by a
2' s compl,ament
add (see section 5.8.1,
Operators). This value is then used as the address of the operand.

5.7.8

Internal Symbol Representation For PALC

Each permanent and user-defined symbol occupies four words in the
symbol table storage area. A PDP-8 instruction has an operation code
of three bits as well as an indirect bit, a page bit, and seven
address bits.
The PALC assembler distinguishes between pseudo-ops,
memory reference
instructions,
other
permanent
symbols,
'and
user-defined symbols in the symbol table.

5-13

5.8 EXPRESSIONS
Expressions are formed by the combination of symbols, numbers, and
certain characters called operators, \~hich cause speci fic arithmetic
operations to be performed. An expression is terminated by either a
comma, carriage return, or semicolon.

5.8.1 Operators
There are seven characters in PALC which act as operators:
+
t
%

&
SPACE

Two's complement addition
TWo's complement subtraction
Hultiplication (unsigned, l2-bit)
Division (unsigned, l2-bit)
Boolean inclusive OR
Boolean AND
Treated as a Boolean inclusive OR
except in a memory refE~rence
instruction

Two's complement addition and subtraction are explained in detail in
Chapter 1 of INTRODUCTION TO PROGRA1~ING; the user should refer to
that handbook if he wi.shes more informat:ion. No checks for overflow
are made during assembly, and any overflow bits are lost from the high
order end. For 4~xample:
7755+24 will give a result of 1
The operators + and - may be used freely as prefix operators.
Mul tiplication is accomplished by repeat:ed addition.
No checks for
sign or overflow are made. All 12 bits of each factor are considered
as magnitude. For example:
3000t2 will give a result of 6000
Division is accomplished by repeated subtraction.
The number of
subtractions which are performed is t:he quotient. The remainder is
not saved and no checks are made for sign.
Division by 0 will
arbitrarily yield a result of O. For example:
7000%1000 will yield a result of 7
This could be written as:
-1000%1000
in this case the answer might be expecte!d to be -1 (7777), but all
bits are considered as magnitude and the result is still 7.

Use of the multiplication and division operators requires an attention
to sign on the part of the programmer beyond that which is required
for simple addition and subtraction. The following table of examples
is given for reference.

5-14

Table 5-2 Use of Operators
Expression

Also written as:

7777+2
7776-3
Ot2
2tO
1000t 7
0%12
12%0
7777%1
7000%1000
1%2

Result

-1+2
-2-3

+1
7773 or -5
0
0
7000 or -1000
0
0
7777 or -1
7
0

-1%1
-1000%1000

The ! operator causes a Boolean inclusive OR to be performed bit by
bit between the left-hand term and the right-hand term.
(The
inclusive OR is explained in Chapter
1
of
INTRODUCTION
TO
PROGRAMMING.) For example:
if A=l and B=2
then A!B=0003
The & operator causes a Boolean AND to be performed bit by bit between
the left and right values.
The operation is the same as that
indicated by the memory reference instruction AND.
SPACE has special significance depending on the context in which it is
used.
When it is used to separate two permanent symbols or two
user-defined symbols, as in the following example:
Sfv'JA CLA

it causes an inclusive OR to be performed between them.
In this case,
SMA=7500 and CLA=7600. The expression SMA CLA is assembled as 7700.
When SPACE is used following pseudo-operators and memory reference
instructions, it merely delimits the symbol.
User-defined
example:

symbols

are

treated

operate

instructions.

For

A=333

*222
8.1

ClA

possible expressions and their values using the symbols just defined
are shown below. Notice that the assembler reduces each expression to
one 4-digit (octal) word:
A
B

A+B
A-B
-A
I-B
B-1
AlB

-71

0333
0222
0555
0111
7445
7557
0221
0333
7707

(an

inclusivE~

5-15

OR is performed)

If the information generated is to be
counter is incremented. For example:

loaded,

the

current

location

B-1 ;A+4 ;A-B

produces three words of information; the current location
incremented after each expression. The! statement:

counter

HAL'f=HLT eLA

produces no information to be loaded (it produces an association in
the symbol table)
and hence does not increment the current location
counter.

*4721
TEMP,
TEM2,

The location counter is not incremented after the line TEMP,; the two
symbols TEMP and TEM2 are assigned the same value, in this case 4721.
Since a PDP-8 instruction has an operation code of three bits as well
as an indirect bit, a page bit, and seven address bits, the assembler
must combine memory reference instructions in a manner somewhat
differently from the way in which it combines operate or lOT
instructions. The assembler differentiates between the symbols in its
permanent symbol table and user-defined symbols.
The following
symbols are used as memory reference instructions:
AND
TAD
ISZ
DCA
JMS
JMP

0000
1000
2000
3000
4000
5000

Logical AND
Two's complement addition
Increment and skip if zero
Deposi t and cl,ear accumulator
Jump to subroutine
Jump

When the assembler has processed one of these
following it acts as an address field dlelimi ter.

symbols,

the

space

*4100

JMP A
CLA

A has the value 4101, JMP has the value 5000, and the space acts as
field delimiter. These symbols are represented as follows:
A
JMP

100 001 000 001
101 000 000 000

The seven address bits of A are taken, «:!. g. :
000 001 000 001
The rema1n1ng bits of the address are tested to see if they are zeros
(page zero reference); if they are not, the current page bit is set:

5-16

000 011 000 001
The operation code is then ORed into thE! JMP expression to form;
101 011 000 001
or, written more concisely in octal:
5301
In addition to the above tests, the pagE! bits of the address field are
compared with the page bits of the current location counter.
If the
page bits of the address field are nonze!ro and do not equal the page
bits of the current location counte!r, an out-of-page reference is
being attempted and the assembler will t;ake action as described in
Section 5.11, Link Generation and Storagre.

5.8.2 Special Characters
In addition to the operators described i.n the previous section, PALC
recognizes several special characters which serve specific functions
in the assembly process. These characters are:

equal sign
comma
'* asterisk
dot
" double quote
( ) parentheses
[] square brackets
/
slash
semicolon
<>
angle brackets
$ dollar sign
,

The equal sign, comma, asterisk, slash, and semicolon have
previously described. The remainder will be described next.

been

The special character dot (.) always has a value equal to the value of
the current location counter. It may be used as any integer or symbol
(except to the left of an equal sign), and must be preceded by a space
when used as an operand. For example:
*200
JMP
• +2

is equivalent to JMP 0202.

Also,

*300
• +2400

will produce in location 0300 the quantity 2700.
*2200
CALL=JMS 1 •

0027

5-17

Consider:

The second line (CALL=JMS I.) does not increment the current location
counter; therefore, 0027 is placed in location 2200 and CALL is placed
in the user's symbol table with an associated value of 4600 (the octal
equivalent of JMS I).
If a single character is preceded by a double quote
("), the 8-bit
value of ASCII code for the character is used rather than interpreting
the character as a symbol (ASCII codes are listed in Appendix A). For
example:

CLA
TAU

("t\

The constant 0301 is placed in the accumulator.
The code:

"
will be assembled as 0256. The characber must not be a carriage
return or one of the characters which is ignored on input (discussed
at the end of this section).
Left and right parentheses
member is optional).

() enclose a current page literal (closing

CLA
TAD INDEX
TAD (2)
DCA I ~DEX

The left parenthesis is a signal to the a.ssembler that the expression
following is to be evaluated and assigned a word in the constants
table of the current page. This is the same table in which the
indirect address linkages are stored.
In the above example, the
quanti ty 2 is stored in a word in th49 linkage and literals list
beginning at the top of the current memory page. The instruction in
which the literal appears is encoded with an address referring to the
address of the literal. A literal is assigned to storage the first
time it is encountered; subsequent reference to that literal from the
current page is made to the same register. The use of literals frees
symbol storage space for variables and makes programs much more
readable.
If the programmer wishes to assign literals to page zero rather than
to the current page, he may use square brackets,
[and] , in place of
parentheses. This enables the programmer to reference a single
literal from any page of memory. For example:
TAD (2]

TAD [2]

5-18

The closing member is optional.
forms:
constant term, variable
another literal.

Literals may take
term, instruction,

the following
expression, or

NOTE
Literals can be nested, for example:
TAD (TAD (30

This type of nesting may be continued in
some cases to as many as 6 levels,
depending on the
numbl3r
of
other
literals on the page and the complexity
of the expressions within the nest.
If
the limits of the assembll3r are reached,
the error messages BE (too many levels
of nesting)
or PE (too many literals)
will result.
Angle brackets are used as conditional dlelimi ters. The code enclosed
in the angle brackets is to be assembled or ignored contingent upon
the definition of the symbol or value of the expression within the
angle
brackets.
(The
IFDEF,
I~~DEF,
IFZERO,
and
IFNZRO
pseudo-operators are used with angle brackets and are described in
section 5.10.9.)
The dollar sign character ($) is mandatory at the end of a program and
is interpreted as an unconditional end-of-pass.
It may however occur
in a text string, comment or II term, in 1flhich case it is interpreted
in the same manner as any other character.
The following characters are handled by the assembler for the
listing, but are otherwise ignored:
FORM FEED
LINE FEED
RUB OUT

pass

Used to skip to a ne\,l page
Used to create a line spacing without causing a
carriage return
Used by the EDITOR to allow corrections in the
input file.

Nonprinting characters include:
SPACE
TAB

RETURN
These characters are used for format control and have been
explained in Section 5.5.

5-19

previously

5.9

INSTRUCTIONS

There are two basic groups of instructions: memory reference and
microinstructions.
Memory reference instructions require an operand,
microinstructions do not.

5.9.1

Memory Reference Instructions

In PDP-8 computers, some instructions require a reference to memory.
They are appropriately designated memory reference instructions, and
take the following format:

OPERATION
C~DE

ADDRESS

INDIRECT ADDRESSINGf
MEMORY PAGE ---~-

Memory Reference Bit Instructions
Bits 0 through 2 contain the operation code of the instruction to be
performed.
Bit 3 tells the computer if the instruction is indirect
(see Section 5.9.2). Bit 4 tells the computer if the instruction is
referencing the current page or page ZE~ro. This leaves bits 5 through
11 (7 bits) to specify an address.
In these 7 bits, 200 octal (128
decimal) locations can be specified; the page bit increases accessible
locations to 400 octal or 256 decimal.
For a list of the memory
reference instructions and their codes •. see Appendix C.
In PALe a memory reference instruction must be followed by a space(s)
or tab(s), an optional I or Z designation, and any valid expression.
It may be defined with the FIXMRI instruction as explained in Section
5.10.12, Altering the Permanent Symbol Table. Permanent symbols may
be defined using the FIXTAB instruction and may be used in address
fields as shown below:
A =123 4

FIXTAB
TAD A

5.9.2

Indirect Addressing

When the character I appears in a statE~ment between a memory reference
instruction and an operand, the operand is interpreted as the address
(or location) containing the address of the operand to be used in the
current statement. Consider:

5-20

TAD 40

which is a direct address statement, where 40 is interpreted as the
location on page zero containing the quantity to be added to the
accumulator. References to locations on the current page and page
zero may be done directly. An alternate way to note the page zero
reference is with the letter Z, as follows:
TAD Z 40

This is an optional notation, not differing in effect from the
previous example.
Thus, if location 40 contains 0432, then 0432 is
added to the accumulator. Now consider:
TAD I

which is an indirect address statement, 'where 40 is interpreted as the
address of the location containing the quantity to be added to the
accumulator. Thus, if location 40 contains 0432, and location 432
contains 0456, then 456 is added to the accumulator.
NOTE
Because the letter I is used to indicate
indirect addressing, it is never used as
a variable.
Likewise the letter Z,
which is sometimes used to indicate a
page zero reference, is never used as a
variable.

5.9.3

Microinstructions

Microinstructions are divided
into
two
groups:
operate
and
Input/Output
Transfer
(lOT)
:microinstructions.
Operate
microinstructions are further subdivided into Group 1, Group 2, and
Group 3 designations.
NOTE
If a programmer mistakenly specifies an
illegal
combination
of
microinstructions, the assembl'er will perform
an
inclusi ve
OR betw1een them; for
example:
eLL SKP is interpreted as SPA
(7100) (7410)
(7510)

Operate Microinstructions
within the operate group, there are thre·e groups of microinstructions
which cannot be mixed.
Group 1 microinstructions perform clear,
complement, rotate and increment operations, and are designated by the
presence of a 0 in bit 3 of the machine instruction word.

5-21

ISSW I lAC I

ICLA I CLL ICMAI CML I

ROTATE AC AND l RIGHT
ROTATE AC AND L LEFT
ROTATE 1 POSITION IF A 0,2 POSITIONS IF A 1
(BSW IF BITS 8,9 ARE 0)
LOGICAL SEQUENCE:

2 - CMA,CML

1 -ClA , Cll
3-IAC

4 - RAR, RAl, RTR ,RTl, BSW

Group 1 Operate Microinstruction Bit Assignments
Group 2 microinstructions check the contents of the accumulator and
link
and, based on the check, continue to or skip the next
instruction. Group 2 microinstructions are identified by the presence
of a 1 in bit 3 and a 0 in bit 11 of the machine instruction word.

234
I

I 1 ICLA ISMA I SZA ISNL I

REVERSE SKIP SENSING OF BITS 5,6,7 IF SET

IOSR IHLT

LOGICAL SEQUENCE: 1 (BIT 8 IS 0) - SMA OR SZA OR SNL
(BIT 8 IS I) - SPA AND SNA AND SZL
2 - ClA
3 - OSR, HlT

Group 2 Operate Microinstruction

Bit Assignments

Group 3 instructions reference
the
MQ
register.
They
are
differentiated from Group 2 instructions by the presence of a 1 in
bits 3 and 11. The other bits are part of a hardware arithmetic
option.
o

___

~O_t~6_~!_IO~i_N .~ ~IC_l_A~IM_QA~I ~I_MQ_-_L~I~~~~~~~~~~~~~~~~I
'----"
CONTAINS A 1 TO
SPECIFY GROUP 3

___ ___

"----'

\..

) '-..-J

'---~
CONTAINS A 1 TO
KEel-E EXTENDED
SPECIFY GROUP 3
ARITHMETIC
ELEMENT

Group 3 Operate Microinstruction Bit Assignments
Group 1 and Group 2 microinstructions cannot be combined since
determines either one or the other.

5-22

bit

Within Group 2, there are two groups ()f skip instructions.
be referred to as the OR group and thE! AND group.
OR Group

AND Group

SMA

SPA
SNA
SZL

SZA
SNL

They

can

The OR group is designated by a 0 in bit B, and the AND group by a 1
in bit B. OR and AND group instructions cannot be combined since bit
B determines either one or the other.
If the programmer does combine lE~gal skip instructions,
important to note the conditions under which a skip may occur.
1.

OR Group--If these skips are combined in a statement,
the inclusive OR of the conditions determines the skip.
For example:

SZA SNL
The next statement is skipped if the
contains 0000 or the link is a 1 or both.
2.

accumulator

AND Group--If the skips are c:ombined in a statement, the
logical AND of the conditions determines the skip. For
example:

SNA SZL
The next statement is skipped only if
differs from 0000 and the link is O.

the

accumulator

Input/Output Transfer Microinstructions
These microinstructions initiate operation of peripheral equipment and
effect an information transfer betwE~en the central processor and the
Input/Output device (s); i.e., cassettE~s, console terminal, and line
printer. The Permanent Symbol Table in Appendix C lists PALC's rOT's.

5.9.4 Autoindexing
Interpage references are often necessary for obtaining operands when
processing large amounts of data. ThH PDP-B computers have facilities
to ease the addressing of this data.
When one of the absolute
locations from 10 to 17 (octal) is indirectly addressed, the contents
of the location is incremented before it is used as an address and the
incremented
number is left in the location.
This allows the
programmer to address consecutive memory locations using a minimum of
statements.

5-23

It must be remembered that initially ~lese locations (10 to 17 on page
0) must be set to one less than the first desired address. Because of
their characteristics, these locations are called auto index registers.
No incrementation takes place when locations 10 to 17 are addressed
directly. For example, if the instruc1t::ion to be executed next is in
location 300 and the data to be refer4:!nced is on the page starting at
location 5000, autoindex register 10 can be used to address the data
as follows:

0276
0277
0300

1377
3010
1410

TAD C4777
DCA 10
TAD I 10

0377

4777

C4711,4111

1=5000-1

ISET UP AUTO INDEX
IINCREMENT TO 5000
IBEFORE USE AS AN ADDRESS

When the instruction in location 300 :Ls executed, the contents of
location 10 will be incremented to 5000 and the contents of location
5000 will be added to the contents OlE the accumulator.
When the
instruction TAD I 10 is executed again, the contents of location 5001
will be added to the accumulator, and so on.

5.10

PSEUDO-OPERATORS

The programmer uses pseudo-operators to direct the assembler to
perform certain tasks or to interpre1: subsequent coding in a certain
manner.
Some pseudo-ops generate storage words in the object program,
other pseudo-ops direct the assembler how to proceed with the
assembly. Pseudo-ops are maintained in the permanent symbol table.
The function of each PALC pseudo-op is described below.

5.10.1

Indirect and Page Zero Addressing

The pseudo-operators I and Z are used to specify the type of
addressing to be performed. These have been previously discussed in
Section 5.9.2.

5.10.2

Radix Control

Numbers used in a source program are initially considered to be octal
numbers.
However, the prograrraner may change or alternate the radix
interpretation by the use of the pseudo-operators DECIMAL and OCTAL.
The DECIMAL pseudo-op interprets all following
until the occurrence of the pseudo-op OCTAL.

numbers

decimal

The OCTAL pseudo-op resets the radix to its original octal base.

5-24

5.10.3

Extended Memory

The pseudo-op FIELD instructs the assembler to output a field setting
so that it may recognize more than one memory field. This field
setting is output during pass 2 and is recognized by the Run (or Load)
command, which in turn causes all subsequent information to be loaded
into the field specified by the expression. The form is:
FIELO n
n is an integer, a previously defined symbol, or an expression
the range 0<=n<=7.

within

This field setting is output on the binalry file during pass 2 followed
by an origin setting of 200. This word is read when the Run (or Load)
command is executed and begins loading i.nformation into the new field.
The field setting is never remembered by the assembler and no initial
field setting is output.
A binary file produced without field
settings will be loaded into field 0 when using the Run (or Load)
command.
NOTE
A symbol in one field may be used to
reference the same location in any other
field. The field to which it refers is
determined by the use of the COF and crF
instructions.
(The pr09rarnrner who is
unfamiliar with the rOT's but wishes to
use them should refer to the POP/BE
SMALL COMPUTER HANOBOO~: and experiment
with several short teBt programs to
satisfy himself as to their effect.)
COF and CIF instructions must be used
prior to any instruction referencing a
location outside the current field,
as
shown in the following example:

*200
TAD P301
CDF 00
CI F 10

Ji'1S PRINT
CI F 10

JMP NEXT
P3Q11 ,

NEXT,

301
FIELD 1
*200
TAD P302
CDF 10

JMS PRINT
HLT
P302,

PRINT,

302

TLS
TSF

5-25

JIVJP • - 1

CLA
RDF
TAD P6203
DCA .+1

00~1

P620~i ,

.1MP
6203

When FIELD is used, the assembler follolNs the new FIELD setting with
an origin at location 200.
For this reason, if the programmer wants
to assemble code at location 400 in field 1 he must write:

/CORRECT EXAMPLE

FIELD
*400

The following is incorrect and will not generate the desired code:

/ I NC"ORii EC T

* 4 eI ~~
FIELD

5.10.4

End-of-File

PAUSE signals the assembler to stop processing the file being read.
The current pass is not terminated, and processing continues with the
next file.
The PAUSE pseudo-op should be used only at the physical end of a file
and with two or more segments of one program. When a PAUSE statement
is reached the remainder of the fill~ is ignored and processing
continues with the next input file.
PAUSE must be present or a PH
error will occur.

5.10.5 Resetting the Location Counter
The PAGE n pseudo-op resets the location counter to the first address
of page n, where n is an integer, a previously defined symbol, or a
symbolic expression, all whose terms have been defined previously and
whose value is from 0 to 37 inclusive, If n is not specified, the
location counter is reset to the next logical page of memory.
For
example:
PAGE 2 sets the location coun1:er to 00400
PAGE 6 sets the location count.er to 01400
If the PAGE pseudo-op is used without an argument and the current
location counter 1S at the first location of a page, it will not be
moved.
In the following example, the code TAD B is assembled into
location 00400:

.JMP .-3
PAGE

TAD B

5-26

If several consecutive PAGE pseudo-ops are given, the first will cause
the current location counter to be reset as specified. The rest of
the PAGE pseudo-ops will be ignored.

5.10.6 Entering Text Strings
The TEXT pseudo-op allows a string of text characters to be entered as
data and stored in 6-bit ASCII by using the pseudo-op TEXT followed by
a space or spaces, a delimiting character (must be a printing
character), the string of text, and the same delimiting character.
Following the last character, a 6-bit zero is inserted as a stop code.
For example:

TAG,
The string would be stored as:
5162
5352
0000

5.10.7 Suppressing the Listing
Those portions of the source program enclosed by XLIST pseudo-ops will
not appear in the listing file; the code will be assembled, however.
Two XLIST pseudo-ops may be used to enclose the code to be suppressed
in which case the first XLIST with no argument will suppress the
listing, and the second will allow it again. XLIST may also be used
with an expression as an argument: a listing will be inhibited if the
expression is equal to zero, or allowed if the expression is not equal
to zero.

5.10.8

Reserving Memory

ZBLOCK instructs the assembler to reserVE~ n words of memory containing
zeros, starting at the word indicated by the current location counter.
It is of the form:
ZBLOCK n
For example:
ZBLOCK 40

causes the assembler to reserve 40 (octal) words.
expression.
If n=O, no locations are reserved.

5-27

The

may

The Il"DEF pseudo-op Jed.kes the form:
I lo"DE E' syrllbol

<SOU.(CE!

c:ode>

If the symbol indicab::d is previously d\~fLled, the codE:! contained in
the angle brackets is assembled; if the synibol is l.mdefined, this code
is ignored. Any number of statements or lines of code may be
contained in the angle brackets. This format of the IFDEF statement
requires a single space before and after the symbol.
The IFNDEF pseudo-op is similar in fonn to IFDEF and is expressed:
IE'NDEF symbol < source code>
If the symbol indicated has not be:en prt~vi()usly defined, the source
code in angle brackets is assembled.
If the symbol is defined, the
code in the angle brackets is ignored.
The IFZERO pseudo~op is of the form:
Il<'ZERO exp:.:esson <sourCE: cede>
If the evaluated (arithmetic or logical) expression is equal to zero,
the code within the angle brackets is assembled; if the expression is
non-zero, the code is ignored. Any nwru)er of statements or lines of
code may be contained in the angle brackets. The expression may not
contain any imbedded spaces and must have a single space preceding and
following it.
IFNZRO is similar in form to the IFZERO pseudo·'op and is expressed:
Il~"NZRO

expression < source code>

If the eValuated (arithmetic or logical) expression is not equal to
zero, the source code wi thin the angl(~ brackets is assembled; if the
expression is equal to zero, this code is ignored.
Pseudo~~ops

can be nested, for example:
IFDEF

S~'M

<IF'NZRO X2 <0 •• »

The evaluation and subsequent inclusion or deletion of
done by evaluating the outermost pseudo·~op first.

5.10.10

s~atements

Controlling Bi.nary Output~

NOPUNCH causes the assembler to cease bi.nary out:put
assembling code.
It is ignored except du.ri.ng pass 2.

but.

cont.inue

ENPUNCH causes the assembler to resume binary output after: NOPUNCH,
and is ignored except during pass 2.
For example, these two
pseudo-ops might be used ·INhere several programs share the same data on
page zero.
When these programs ar(~ to be loaded and executed
together, only one page zero need be output.

5-28

5.10.11

Controlling Page Format

The EJECT pseudo··op causes the listing t:o jump to the top of the next
page.
A page eject is done automatically every 55 lines: EJECT is
useful if the user requires more frequent paging.
If this pseudo-op
is followed by a string of r,haracters, t:he first 40 (octal) characters
of that string will be- used as a new header line.

5.10 .12

Altering the Permanent Symbol 'rable

PALC contains a table of symbol definitions for the PDP-8 and CAPS-8
peripheral devices.
These are symbols such as TAD, DCA, and CLA,
which are used in most. PDP-8 programs. This table is considered to be
the permanent symbol table for PAI.l~; all of the symbols it contains
are listed in Appendix C.
If the user purchases one or more optional devices whose instruction
set is not defined among the permanent symbols (for example EAE or an
AID converter), he would want to add thE~ necessary symbol
defini tions
to
the permanent symbol table in every p~ogram he assembles.
Conversely, the user who needs more space for user-defined symbols
would probably want t~o delete all def ini tions except the ones used in
his program.
For such purposes, PALC h,~s three pseudo-ops that can be
used to alter the permanent symboltahle.
These pseudo-ops are
recognized by the assembler only during pass 1. During either pass 2
or pass 3 they are ignored and have no effect ..
EXPUNGE deletes the entire permanent symbol table, except

pseudo~'ops.

FIXTAB appends all presently defined sY~IDols to the permanent symbol
table.
All symbols defined befo!'e the occnrrence of FIXTAB are mael.e
part. of the permanent symbol table nnt.LI. the assembler is ::t:'~loaded.
To append the following instructions to the symbol
generates an ASCII fiJ.f> called SYflITS. P)l.T, contain 5.ng ~
MUY=74~5

DVI=7407
CLSK::6131
FIXTAB

table,

t.he

user

IMULTIPLY
IDIVIDE
15KIP ON CLOCK INTERRUPT
ISO THAT THESE WON'T BE
IPRINTED IN THE SYMROL TARLE

The ASCII file is then entered in PAI,C I S input designation.
The user
may also place the definitions at the beginning of the source file.
This eliminates the need to load an extra file.
Each time the assembler :i.s loaded, PALe's permanent symbol table is
restored to contain only the penn<'1nent ::;ymbols shown in Appendix C~
The third pseudo-op used to alter the p'Jrrnanent symbol table in PALC
is FIXMRI.
FIXMRJ is used to def.ine a memory reference instructi.on
and is of the form:
FIXMRI

name:"v,~lue

5-29

The letters FIXHRI must be followed by one space, the symbol for the
ins truction to be de fined, an equal sign, and the val ue~ of the symbol.
The symbol will be defined and stored in the symbol table as a memory
reference instruction. The pseudo-op must be repeated for each memory
reference instruction to be defined. For example:
EXPUNGE
FIXMRI
TAD=100C
FIXMRI
DCt~=3eJ00
CLA=7200
FIXTAB

When the preceding program segment is r,ead into the assembler during
pass 1, all symbol definitions are deleted and the three symbols
listed are added to the permanent symbol table. Notice: that CLA ~s
not a memory reference instruction. This process can be performed to
alter the assembler's symbol table so that it contains only those
symbols used at. a given installation or by a given program. This may
increase the assembler's capacity for user-defined symbols in the
program.
A summary of the PALC pseudo-ops is provided in Appendix C.

5.11

LINK GENERATION AND STORAGE

In addition to handling symbolic addressing on the current page of
memory, PALC automatically generates links for off-page references.
If reference is made to an address not on the page where an
instruction is located, the assembler sets the indirect bit (bit 3)
and an indirect address linkage will be generated on the current
memory page.
If the off-page reference is already an indirect one,
the error diagnostic II (illegal indirect) will be generated.
For
example:
*2117

CLA

tJMP A

In the example above, the assembler will recognize that the register
labelled A is not on the current page (in this case 2600 to 2777) and
will generate a link to it as follows:
1. In location 2600 the assembler ,,,,ill place the
which is equivalent to JMP I 2777.

word

5777

2. In address 2777
(the last available location on the
current page) the assembler will place the word 2117 (the
actual address of A).
During pass 3, the octal code for the instruction will be followed
an apostrophe (') to indicate that a link was generated.

Although the assembler will recognize and generate an indirect address
linkage when necessary, the progra~ner may indicate an explicit

5-30

indirect address by the pseudo-op I. The assembler cannot generate a
link for an instruction that is already specified as being as indirect
reference.
In this case, the assembler will print the error message
II (illegal indirect). For example:
*2117

CLA

J:'1P I A
The above coding will not work because 1>:. is not defined on the
where JMP I A is attempted, and the indirect bit is already set.

page

Literals and links are stored on each pa.ge starting at page address
177
(relative)
and extending toward page address 0
(relative).
Whenever the origin is then set to another page, the literal buffer
for the current page is output. This does not affect later execution.
There is room for 160 (octal) literals alnd links on page zero ann 100
(octal) literals on each other page of memory.
Li terals and links are stored only alS far down as the highest
instruction on the page.
Further at.tempts to define literals will
result in a PE (page exceeded) or ZE (page zero exceeded) error
message.

5.12

CODING PRACTICES

A neat printout (or program listing, as it is usually called) makes
subsequent editing, debugging, and inte~rpretation much easier than if
the coding were laid out in a haphazard fashion. The coding practices
listed below are in general use, and will result in a readable,
orderly listing.
1.

A title comment begins with a slash at the left margin.

Pseudo-ops may begin at the left margin; often, however,
they are indented one tab stop to line up with the
executable instructions.

Address labels begin at the left margin.
They
separated from succeeding fields by a tabulation.

Instructions, whether or not they are
labe 1 fie ld, are indented one t:ab stop.

A conunent is separated from thE~ preceding field by one
or two tabs
(as required) and a slash; if the comment
occupies the whole line itusually begins with a slash at
the left margin.

5-31

preceded

are
by

5.13

PROGRAM PlillPARATION AND ASSEMBLER OUTPUT

The following program was generated using the
CAPS-8 EDITOR and was assembled with PALC.

TAB

function

the

*200
IEXAMPLE OF INPUT TO THE FORMAT
IGENERATOR PROGRAM
ISTART OF PROGRAM
BEGIN,
0
KeC
KSF
IWAIT FOR' FLAG
IFLAG NOT SET YET
Jr1P .-1
IREAD IN CHARACTER
KHB
DCA CHAR
Tt~D CHAR
Tt\D MSPACE
lIS I T A SPACE?
S NA CLA
HLT
IYES
INO:INPUT AGAIN
Jr1P BEGIN+2
CHAR,
0
ITEMPORARY STORAGE
MSPACE, -~!40
lEND OF EX~\MPLE
$

The program consists of statements and pseudo-ops and is terminated by
the dollar sign ($).
If the program is large, it can be segmented by
placing it into several files; this often facili tates t~he editing of
the source program since each section will be physically smaller.
The assembler initially sets the current location COt.nter to
This counter is reset whenever the asterisk (*) is processed.

0200.

The assembler reads the source file for pass 1 and defi.nes all symbols
used.
During pass 2, t~he assembler reads the source file and generates the
binary code using the symbol table equivalences defined during pass 1.
The binary file that is output may be loaded by the Load command.
This binary file consists of an origin setting and date: words.
During pass 3, t~he assembler reads the source file and generates the
code from the source statements. The assembly listi.ng is output in
ASCII code.
It consists of the current locatior.. counter, the
generated code in octal, and the sourc·e statement. Tr..e 5-digi t first
column is the field number and 4-digit octal address (current location
counter); the 4-·digi t second column is the assembled object code. The
symbol table is printed at the end of the pass. The pc:ss 3 output is:

PALe-V1

*200
021~0

12'12120121
012121211
0121202
1210203
1210204
00205
1210206
0021217

0000
6121:52
60:51

002H'I

76~)0

5202

60:36
3213
12 ~l3
12 ~l4

03/08'73

PAGE 1

*200

IE)(AMPLE OF I NPUT Tel THE FORMAT
IGEN~RATOR PROGRAM
BEGIN, 121
1ST ART OF

Kec

KSF
JMP
KRB
DCA
TAD
TAD
SNA

.-1

CHAR
CHAR
MSPACE
CLA

5-32

Pf~OGR

IWAIT FOR FI.AG
IFLAG NOT SET YET
IREAD INC H I~ RACT ER
lIS I T A SF j~CE?

021211
00212
2121213
2121214

14212
52212
21212121
15421

HLT

IVES
INOIINPUT AGAIN
ITEMPORARV STORAGE

JMP BEGIN+2

CHAR,
21
MSPACE, .2421
lEND Of EXAMPLE
$

PALC-V1

213/08/73

PAGE 1-1

BEGIN
CHAR

2122121
0213
MSPACE 21214

5.13.1 Terminating Assembly
PALC will a) terminate assembly, b) print. a tc, and c) wait for the
user to mount the System Cassette on dri'"e 0 and type tc, under any of
the following conditions:
1.

Normal exit--The $ at the end of the source program was
executed on pass 2 (or pass 3 if a listing is being
generated) •

Fatal error--One of the following error conditions
found and flagged (see the next: section) :
BE

5.14

was

tC--If typed by the user, control turns to the Monitor.

PALC ERROR CONDITIONS

PALC will detect and flag error conditions and generate error messages
on the console terminal. The format of t:he error message is:
CODE ADDRESS
where CODE is a 2-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. For example, the following code:

BEG,

TAD LBL
7.TAD LBL

5-33

would produce the error message:
Ie BEG+0001

since % is an illegal character.
If at any time PALC prints tc, the user should make cert,ain that the
System Cassette is mounted on drive 0 and then type tc to return to
the Monitor.
He should examine each error indication to determine
whether correction is required.
On the pass 3 listing, error messages are output as 2-character
messages on the line just prior to the line in which the error
occurred.
The following table lists thE~ PALC error codes.
Those
labeled Fatal Error are followed immedia1:ely by an effective tC.
Table 5-3 PALC Error Codes
Error Code

Explanation

Two PAL-C internal tables have overlapped.
error--assembly cannot continue.

Device error. An error was detected when trying
to read or write a devic(~.
Fatal error--assembly
cannot continue.

Device
full.
continue.

Illegal character. The character is
the assembly continued.

Illegal redefinition of a symbol.
An attempt was
made to give a previously defined symbol a new
value by means other than the equal sign.
The
symbol is not redefined.

Illegal equals--an equal sign was used in the
wrong context.
Considered a warning and may not
indicate an error but rather an undefined symbol
at that point.

Illegal indirect--an off-page reference \-J'as made.

Illegal pseudo-op--a pseudo-op was used
wrong context or with incorrect syntax.

Illegal page zero reference--the pseudo-op Z was
found in an instruction which did not. refer to
page zero.
The Z is ignored.

Current non-zero
made to:

Fatal

page

5-34

error--assembly

exceeded--an

Fatal

cannot

ignored

attempt

and

the

was

Table 5-3
Error Code

PALe Error Codes (Cont'd)
Explanation

Override a literal with an instruction

Override an instructi.on with a literal

Use more literals thaln the assembler allows on
that page.

This can be corrected by decreasing either the
number of literals on the page or the number of
instructions on the page.
PH

Phase error--either no $ appeared at the end of
the program, or < and > in conditional pseudo-ops
did not match.
Fatal error--assembly
cannot
continue.

Redefini tion--a permanent. symbol has been defined
with =. The new and old definitions do not match.
The redefinition is allow'ed.

Symbol table exceeded--too many symbols have been
defined for the amount of memory available. Fatal
error--assembly cannot continue.

Undefined origin--an undefined symbol has occurred
in an origin statement.

Undefined symbol--a syrrbol has been processed
during pass 2 that was not defined before the end
of pass 1.

Page 0 exceeded--same as PE except with
to page O.

5-35

reference

CHAPTER 15
CASSETTE BASIC

6.1

INTRODUCTION

Cassette BASIC is an interactive progJranuning language derived from
Dartmouth BASIC and designed to run under the Cassette Keyboard
Monitor. The BASIC language is aimed at facilitating communication
between the user and the computer. The user types his program as a
series of numbered statements, making llse of common English words and
familiar mathematical notations. Because the BASIC language involves
learning only a small number of commands, it is a very easy language
to use.
As the user gains familiarity with BASIC, he can add the
advanced techniques available to perform more intricate manipulations
or express a problem more efficiently and concisely.
Cassette BASIC provides approximately 1.7 to 2K of memory for program
storage.
Important
features
include
1and
2-dimensional
subscripting, user-coded functions, program chaining, use of cassettes
for program storage, and use of line printer, if available, for
output.
Beginning programmers may find a more fundamental approach to
language programming in Chapter 1 of THE EDUSYSTEM HANDBOOK.

6.2

BASIC

CALLING BASIC (.R BASIC)

Using the Cassette Keyboard Monitor, Bl\SIC is called from
Cassette by typing:

the

System

!...R BASIC
When it is first loaded into memory, Bl\SIC asks the user
use run~·time fi Ie input and output as follows:
USING RUN-TIME FILE

I/O?(Y

wi 11

OR N)

The user responds with Y or N followed by a carriage return. Choosing
the run-time I/O feature leaves the user approximately 1.7K of memory
for program storage, whereas a responsE~ of N frees the space used by
the run-time I/O routines and provides an additional. 3K of memory
(enough for approximately 20-25 statements
or
75
variables).
Statements associated with the run-timE! I/O feature are:
OPEN ••• FOR INPU'r
OPEN ••• FOR OUTPUT
CLOSE
IF END#
PRINT#
INPUT#
COMMAS
NO COMMAS

If any of these statements are used without the run-time I/O option
having been chos4:!n during BASIC' s initial dialogue, BASIC will print a
NO FILES ERROR message at run-time.
BASIC then asks:
NEW OR OLD-

The user responds NEW if he intends to create a program at the
keyboard, and must respond with the namE~ of the new prQo~ram when BASIC
requests:
NEw PROGRAM NAME-

The program name is typed as a standard system filename (6 characters
or less) and an optional extension (I to 3 characters); a program name
is entered even if the user does not in1:end to save the program for
future use.
(.A
response of only a carriage return causes BASIC to
repeat the NEW PROGRAM NAME request.
If the user types an ALT MODE in
response to this request, the name NONAME.BAS is assigned by BASIC.)
When the new program name has been entered, BASIC indicates that it is
ready
to accept input by issuing a carriage return/line feed
combination.
If the user responds OLD to BASIC' s ini 1:ial dialogue, BASIC assumes
that the program has been previously saved on a cassette and will ask:
OLD PROGRAM NAMEUNITI(0-7):

The user must respond with the correct program name and file extension
(if any), and then must specify which cassette unit drive the file is
stored on.
(An incorrect response will return an error message.) When
this interaction is complete, BASIC will type:
READY.

and the user may edit or run his progrrun.

6.3

NUMBERS

Cassette BASIC t.reats all numbers (in both integer and real formats)
as real, or floating point, numbers. 'That is, BASIC a.ccepts as input
any number conta.ining a decimal point and assumes a decimal pQint
after any intege:r number entered.
In addition to i.nteger and real formats, a third format. is recognized
and accepted by BASIC in order to express numbers outside the range
.01<=x<1000000. This format is called exponential or E:-type notation.
In this format., a number is expressed as a decimal number times some
power of 10, as follows:

6-2

where E represents "times 10 to the power of" •
A number in
exponential notation is then read "xx times 10 to the power of n"; for
example:
23.4E2 = 23.4*(10 to the power of 2) = 2340
Data may be input in anyone or all three of these forms.
Internal
computations are carried out in floating point (real) format.
Results
of computations within the range .01<=x<1000000 are output as either
real or integer decimal numbers (whichever is the correct but more
concise format); results outside this range are output in exponential
format.
BASIC handles seven significant digits in normal operation
and input/output, as illustrated below:
Same Value
Output By BASIC

Value Typed In
.01
.0099
999999
1000000

.01
9.900000E-3
999999
1.000000E+6

BASIC automatically suppresses the pri:nting of leading and trailing
zeros in integer and decimal numbers and, as shown above, prints all
exponential numbers in the form:
(sign) x.xxxxxx E (+ or -) n
where x represents the number carried ·to six decimal places, E stands
for "times 10 to the power of", and n represents the exponent. For
example:
-3.4702lSE+S,is equal to -34702lS00
7.260000E-4 is equal to .000726

6. 4

VARIABLES

A variable in BASIC is a symbol which represents a number and is
formed by a single letter or a letter followed by a digit. For
example:
Acceptable Variables
I

Unal:ceptable Variables
2C - A digit cannot begin
a variable
AB .• Two or more letters
cannot form a variable

6-3

The user may as:sl.gn values to variables either by computing the values
in a LET statement or by inputting the values as data: these
operations are discussed later.

6.5

ARITHMETIC OPERATIONS

BASIC performs addition, subtraction, multiplication, division and
exponentiation, as well as more complicated operati.ons explained in
detail later in the chapter. The five operators used in writing most
formulas are:
Symbol

I
t

6.5.1

Meaning

Example

Addition
Subtraction
Multiplication
Division
Exponentiation
(Raise A to the
Bth power)

A + B
A - B
A * B
A I B
A t B

Priority of Operations

In any given mathematical formula,
BASIC
performs
operations in t:he following order of evaluation:

arithmetic

Parent:heses receive top priority. Any expression wi thin
parent:heses
is evaluated before an unparenthesized
expression.

In absence of parentheses, the order of priority is:

Exponentiation

Multiplication and Division (of equal pr:Lori ty)

Addition and Subtraction (of equal priority)

If ei t:her 1 or 2 above does not clearly deBignate the
order of priority, then the evaluation of expressions
proceeds from left to right.

The expression AtBtC is evaluated from left to right as follows:
1.

AtB

(result of step 1) tc

= step 1
= answer

The expression A/B*C is also evaluated from left
multiplication and division are of equal priority:
1.

AlB

= step 1

(result of step 1) *C

= answer

6-4

right

since

6.5.2

Parentheses and Spaces

Parentheses may be used by the programmer to change the order of
priority
(as listed in rule 2 of the previous section). Since
expressions within parentheses are always evaluated first,
the
programmer
can
control
the order of evaluation by enclosing
expressions appropriately. Parentheses may be nested, or enclosed by
a second set (or more) of parentheses.
In this case, the expression
within the innermost parentheses is evaluated first, and then the next
innermost, and so on, until all have been evaluated.
Consider the following example:
A=7*C CBf2+4)/X)

The order of priority is:
1.

Bt2

(result of step 1)+4

= step 2

(result of step 2)/X

step 3

(result of' step 3)*7

step 1

Parentheses also prevent any confusion
expression is evaluated. For example:

doubt

how

the

A*Bf2/7+B/C+Df2
«A*Br2)/7)+«B/C)+Df2)

Both of these formulas will be executed in the same way.
However,
most users will find that the second is easier to understand.
Spaces may be used in a similar manner~
ignores spaces, the two statements:
LET B

Since

the

BASIC

compiler

= Of 2 + 1

LETB=Df2+1

are identical, but spaces in
reading.

6.5.3

the

first

statement

provide

ease

Relational Operators

A program may require that two values be compared at some point to
discover their relation to one another. To accomplish this, BASIC

6-5

makes use of the following relational operators:
::

<
<=

equal to
less than
less than or
equal to

> greater than
>= greater than or
<equal to
<> not equal to

Depending upon the result of the comparison, flow of program execution
may be directed to another part of the program, or thE~ validity of the
relationship ma.y cause a value of 0 (indicating a FAL~E condition) or
1 (indicating a TRUE condition) to be assigned to a variable. For
example:
1S X=Y<7.

This statement assigns the value 1 to X if Y is greater than Z.
Relational operators are used primarily in conjunction with IF and LET
statements, bot.h of which are later discussed in detai 1.
The meaning of the equal sign (=) should be clarified.
In algebraic
notation, the formula X=X+ 1 is meaningless. HowevE~r, in BASIC (and
most computer languages), the equal sign designates replacement rather
than equality.
Thus, the formula X=X+l is actually translated: "add
one to the current value of X and storie the new resul t back in the
same variable X"; whatever value has previously bE!en assigned to X
will be combined with the value 1.
An expression such as A=B+C
instructs the computer to add the values of Bane: C and store the
result in a thi.rd variable A; the variable A is not be!ing evaluated in
terms of any previously assigned value, but only in t.erms of Band C.
Therefore, if A has been assigned any value prior to i.ts use in this
statement, the old value is lost; it is instead replc.ced by the value
of B+C. Finally, the equal sign may be used in relational testing as
illustrated in the previous example.

6.6

IMMEDIATE MODE

Commands are available which allow Cassette BASIC to act as a
calculator--that is, the user types an algebraic expression which is
to be calculated and BASIC types back the result.
This is called
Immediate Mode since the user is not required to write a detailed
program to calc:ulate expressions and equations, but can use BASIC to
produce resul t:s immediately. The commands used in Immediate Mode are
PRINT, LET and occasionally the FOR-NEXT combination.
These are
explained in the following paragraphs.

6.6.1

PRINT Command

The PRINT command is of the form:
PRINT expression
BASIC is instructed to compute the value of the expre!:;sion and print
the result on the console terminal.
The expre!:;sion is a normal

6-6

arithmetic expression \-lhich may includ43 numbers, variables, arithmetic
operators, and functions (discussed in Section 6.8.12). A string of
text may also be printed (see Section 6.8.5--PRINT). For example:

PRINT 1/Rf8
5.9604 6LJ E-08

6.6.2

LET Command

Values may be assigned to variables by
follows:

use

the

LET

command

LET variable=expression
The computer does not type anything in response to this command, but
computes the expression and assigns the value to the variable. The
variable may then be used in another ,computation or may be output
using the PRINT command. For example:

LET Pl=3.14159
PRINT Pl*4f2
50.26544

6.6.3 Looping PRINT and LET Commands
It is possible to include PRINT and LE'T commands in a loop so that
variables and results may be stored or printed in a series. Looping
is accomplished by means of FOR-NEXT statements in which the FOR
statement sets the limits of the loop and the NEXT statement
increments the count by 1. The only restriction in Immediate Mode
looping is that the command and the looping statements must appear on
one line. This is accomplished by using the backslash (\)
character
to separate multiple statements on a line.
(The backslash is produced
on an LT33 or 35 Teletype by pressing the SHIFT and L keys
simultaneously. Other types of terminals provide a separate key.) For
example:
Ll!.l P 1 =3.14159

FOR 1=1 TO 3\PR1NT Plf!\NEXT !

This combination will print the results of 3.14159 to
and 3rd powers respectively.

the

1st,

2nd,

More information on looping in general is provided in Section 6.8.7.

6-7

6. 7

EXAMPLE RUN

The following Example Run is included a·t this point as an illustration
of Cassette BASIC's initial dialogue, the format of a BASIC program,
the ease in editing and running it, and the type of output that may be
produced.
The user calls in the pr09ram AVER from cassette drive 1
and attempts to run it.
Execution is ha.lted by a SYNTAX ERROR at line
30.
The user lists the program, finds the mistake in line 30, and
also notices a mistake in line 85.
He corrects these errors by
retyping the lines, and then reruns the program.
After execution he
saves the corrected program on drive 1 under the original name.
Following sections cover the statements and
prosrramming •

commands

used

• R BASIC
USING RUN-TIME FILE I/O?(Y OR N)N
NE\-]

OR OLD-OLD

OLD PROGRAM NAME-AVER
UNITH(O-7):1
HEADY.
RUN
HOi·j MA0JY STUDENTS,

HOt!)

MANY GRADES PER STUDENT ?5,/.1

SYNTAX ERROR AT LINE 30
LIST
10 REM - PROGRAM TO TAKE AVERAGE OF
15 REM - STUDENT GRADES AND CLASS GHADES
20 PRINT "HOW MANY STlJDENTS, HO\·j MANY GHADES PER STUDENT ";
30 INPUT A,lB
40 LET 1=1
5v) FOR J=I T8 A
55 LET V=0
6(1} PHINT "STUDENT NUMnEH =";J
75 PBINT "ENTER GRADES"
76 LET D=J
80 FOR K=D TO D+(B-1)
81
02
(~5

INPUT G

LET V=V+G
NEXT L

90 LET V=V/B
95 PRINT "AVERAGE GRADE =";t.j

96 PRINT
99 LET

Q =Q+V

1(1}0 NEXT J
101
102
103
1 (14

PRI NT
PBINT "CLASS A.VER!'\GE =";Q/A

pnlNT

1 4(~

END

STOP

BASIC

READY.

INPUT A,B

85 NEXT K
RUN

HOW MANY STUDENTS, HOW MANY GRADES PER STUDENT ? 5, It
STUDENT NUMBER = 1
ENT ER GRADES

778
786
?88
774
A V ERA GE GRAD E = 8 1 • 5
STUDENT NUMBER
ENTER GRADES

759
?86
17'0

787
AVERAGE GRADE

= 75.5

STUDENT NUMBER = 3
ENT ER GRAD E5

758
764
?75
780
AVERAGE GRADE = 69.25
STUDENT NUMBER = 4
ENT ER GRADES

788
792
185
179

= 86
STUDENT NUMBER = 5

AVERAGE GRADE

ENT ER GRAD ES

?6'0

?78
?85
1[50
AVEHAGE GRl\DE

75.75

CLASS AVERAGE
READY.

SAVE
UNITH(O-7):1

READY.

6-9

6.8 BASIC STATEMENTS
The statements described in this section are used in creating BASIC
programs.
These statements make up the body of tt.e program; they
perform arithmetic calculations and input and output operations, and
control the orde:r of program execution.

6.8.1

Statement. Numbers

An integer number is placed at the beginning of each line in a BASIC
program.
BASIC executes the statements in a prograrr. in numerically
consecutive order regardless of the order in which they have been
typed. A recommended practice is to number lines by fives or tens, so
that additional lines may be inserted in a program without the
necessity of renumbering lines already present.
(BASIC programs may
be created using either the BASIC Editor as described here, or the
CAPS-8 EDITOR. If the CAPS-8 EDITOR is used, the programmer must make
certain to type his program in numerically consecutive order, as BASIC
will not sort it in this case.)
Multiple statements may be placed on a single line by separating each
statement from the preceding statement with a backs lash (SHIFT/L).
This feature is particularly useful since statement numbers require
space in the symbol table; if unnE~cessary statement numbers are
eliminated by use of the backslash, there will be more room for
program storage. For example:
10 A=5'B=.2'C=3'PHINT "ENTER DATA"

All of the statements in line 10 will be executed before BASIC
continues to the next line.
Only one statement number at the
beginning of the entire line is necessary.
However, it should be
noted that program control cannot be transferred to a statement within
a line, but only to the first statement of the line in which it is
contained (see Section 6.8.9, Transfer of Control Statements).

6.8.2

Commenting the Program (REM)

The REM or REMARK statement allows the programmer to insert comments
or remarks into a program without thesE~ comments affecting execution.
The BASIC compiler ignores everything on a line beginning with REM.
The form is:
(line number) REM (message)
In the Example Run program, lines 10 ruld 15 are REM~RK statements
describing what the program does. It is often useful to put the name
of the program and information relating to its use at the beginning
where it is available for future refE~rence. Remarks throughout the
body of a long program will help later debugging by explaining the
purpose of each :section of code wi thin t:he program.

6-10

6.8.3

Terminating the Program (END and STOP)

The END statement (line 140 in the Example Run program), if present,
must be the last statement of the entire program. The form is:
(line number) END
Use of the END statement is optional.
of the program and BASIC prints:

If executed, it signals the end

READY.
Variables and arrays are left in an unde:fined state,
any values they have been assigned durin.g execution.

thereby

losing

The STOP statement is used synonymously with the END statement to
terminate execution, but while END occurs only once at the end of a
program, STOP may occur any number of ti.mes. The format of the STOP
statement is:
(line number) STOP
This statement signals that execution is to be terminated at that
point in the program where it is encountered leaving variables in a
defined state.
(Variables will contain the values assigned when the
statement is encountered.)

6.8.4

The Arithmetic statement (LET)

The Arithmetic (LET) statement is probably the most commonly used
BASIC statement.
It causes a value to be assigned to a variable and
is of the form:
(line number)

(LET) x = expression

where x represents a variable, and the E~xpression is either a number,
another variable, or an arithmetic expression. The word 'LET' is
optional; thus the following statements are treated the same:

LET A=Af8+10
A=A f8+10

LET C =F'/G

C=F/G

As mentioned earlier, relational opera1:ors may be used in a LET
statement to assign a value to a variru)le depending upon the validity
of a relationship.
If the statement is FALSE, the value 0 is assigned
to the variable; if TRUE, the value 1 if> assigned. For example:
100 A=1
105 8=2
110 C=A=B
120 D=A>8
130 E=A<>B
140

PRINT C,D,E

150 E\JO

6-11

Translated, this actually means "let C=l if A=B (O otherwise): let 0=1
if A>B (0 otherwise)" and so on. Thus, the values of C, 0, and E are
printed as follows:
RUN
[21

READY.

There is no limit to the number of rela1:ionships that may be tested in
the statement.

6.8.5

Input/Output Statements

Input/Output sta'tements allow the user t:o bring data into a program
and output results or data at any time during execution. The console
terminal keyboard, (LT33 Teletype reader and punch uni t:s, if present) ,
cassettes, and line printer are all available as I/O devices in
Cassette BASIC. Statements which control their use are described
next.

READ and DATA
READ and DATA statements are used to input data into a program.
One
statement is n4~ver used without thE! other. The form of the READ
statement is:
(line number) READ xl,x2, ••• xn
where xl through xn represent variable names.

For example:

1 [21 REA D A, B , C

A,B, and C are variables to which values will be assignE~d.
Variables
in a READ statement must be separated by commas. READ statements are
generally placed at the beginning of a program, but must at least
logically occur before that point in the program wheJ::'e the value is
required for some computation.
Values which will be assigned to the variables in a READ statement are
supplied in a DA~~A statement of the form:
(line number) DATA xl,x2, ••• xn
where xl through xn represent values. The values must be separated by
commas and mus1: occur in the same order as the variables which are
listed in the corresponding READ statement.
A Dl~TA
statement
appropriate for t:he preceding READ statement is:
7 :) DA TAl , 2 , 3

Thus, after executing the READ statement, A=l, B=2, and C=3.

6-12

The DATA statement is usually placed at the end of a program (before
the END statement) where it is easily accessible to the programmer
should he wish to change the values.
A READ statement may have more or fewE!r variables than there are
values 1n anyone DATA statement. ThE! READ statment causes BASIC to
search all available DATA statements in consecutive line number order
until values are found for each variable in the READ. A second READ
statement will begin reading values where the first stopped.
If at
some point in the program an attempt is made to read data which is not
present or if the data is not separated by commas, BASIC will stop and
print the following message on the console terminal:
DATA ERROR AT LINE XXXX
where XXXX indicates the line
caused the error.

number

the

READ

statement

which

RESTORE
If it should become necessary to use the same data more than once in a
program, the RESTORE statement will make it possible to recycle
through the DATA statements beginning with the lowest numbered DATA
statement. The RESTORE statement is of the form:
(line number) RESTORE

An example of its use follows:
15 READ B .. C .. D

55 RESTORE
60 READ E,F,G

100 END

In this example, the READ statements in lines 15 and 60 will both read
the first three data values provided in line 80.
If the RESTORE
statement had not been inserted before line 60, then the second READ
would pick up data in line 80 starting with the fourth value.
In recycling through data with a RESTORE statement, the programmer may
use the same variable names the second time through the data, or not,
as he chooses, since the values are being read as though for the first
time.
In order to skip unwanted values, the programmer may insert
replacement (or dummy) variables. Consider:

6-13

1 REM - paOGRAM TO ILLUSTRATE USE OF RESTORE
20 READ N
25 PRINT "VJ\LTJES OF X ARE: ft

30 FOR 1=1 TO N
40 READ X
5'3 PRINT X,
60 NEXT 1
70 RESTORE
185 PRI NT

190 PRINT "SECOND LIST OF X VALUES'"
200 PRI NT "FOLLOW 1 NG RESTORE STAT Et'-lENT :"
210 FOR 1=1 TO N
220 READ X
230 PRI NT X.,
240 NEXT I
250 DATA 4,1,2
2 51 DA T A 3, ,4
3'~0 END
RU~

X ARE:
1 2 3

VALUES OF

SECOND LI ST OF X VALUES
FOLLOWING RESTORE STATEMENT:

4 1 2

READY.

The second time the data values are read, the variable X (line 220)
picks up the value originally assigned to N in line 20, and as a
result, BASIC prints:
4

To circumvent this, the programmer could insert a dummy variable
(for
example, 205 READ Z ), which would pick up and store the first value,
but would not be represented in the PRINT statement. In this case the
output would be t.he same each time through the list.

INPUT
The INPUT statement is used when data is to be supplied by the user
from the console terminal keyboard while a program is executing, and
is of the form:
(line number) INPUT xl,x2, ••• xn
where xl through xn represent variable names.

For example:

25 INPUT A,B,C

This statement will cause the program to pause during e:<ecution, print
a question mark on the console terminal, and wait for the user to type
three numerical values. The user must separate the values by commas;
they are entered into the computer by pressing the RE'rURN key at the
end of the list.

6-14

If the user does not insert enough values to satisfy the INPUT
statement, BASIC prints another question mark and waits for more
values to be input.
When the correct number has been entered,
execution continues.
If too many values are input, BASIC ignores
those in excess of the required number. 'rhe values are entered only
when the user types the RETURN key.

OPEN
Input and output files may be stored on cassette, and may be accessed
during run-time (providing the user has chosen the run-time I/O option
during BASIC's initial loading dialogue).
Before an I/O file is
accessed however, the user must first open it via one of the following
commands:
(line number) OPEN "n:xxxx" FOR INPUT
or
(line number) OPEN

"n:xxx:~"

FOR OUTPUT

where n represents the cassette drive numJer (O-7), and xxxx is any
legal filename
(6 characters or less, and optional extension of 3
characters or less). Input files are cre.ated either by using BASIC or
the CAPS-8 EDITOR (see Section 6.8.6), .and must have been previously
stored on cassette before being accessed. For example, the statement:
215 OPEN III :TEST.DAT" FOH I:\1PUT

opens an input file named TEST.DAT on cassette drive 1.
Only one input and one output file may be open at any time, and only
one file--either input or output--may be open on a given cassette
drive at one time.

CLOSE
The CLOSE statement is used to close a currently open output file, and
is of the form:
(line number) CLOSE
Suceeding OPEN FOR INPUT statements will perform an automatic close on
a previously open input file: however, the user should take note of
the following cases:
1.

If the user attempts to open an input file on a cassette
which is currently open for output, BASIC will return an
I 0 ERROR, as the same cassette drive cannot be open for
both input and output at the saml~ time.

If the user has an input file open on a cassette, and is
at
its
end-of-file
(that i:;, a CTRL/Z has been
detected), BASIC will allow him -to open an output file

6-15

on
t:he
same
cassette, since the input file is
theoretically "closed". However, if the u~:er has an
input file open on a cassette and is not at its
end-of-file, an I 0 ERROR will occur if he then tries to
open an output file on the same cassette.
(See Section
6.8.9, IF END#, for more information on BASIC's method
of det:ecting an end-of-file.)
3.

If the! user tries to open an output file and an output
file is already open on any cassette, BASIC will return
a "FIl,E OPEN ERROR": before opening a new output file,
the current output file must be closed.

A close is automatically performed on both open input and open output
files by STOP, END and CHAIN statements, as well as by all errors
detected at run-time.

INPUT#
Once an input file has been opened using the open statement, data can
be called into a program using the INPUT# statement. The form of this
statement is:
(line number) INPUT# xl,x2, ••• xn
where # signifies that the file is stored on cassette under the
filename and drive number specified in the last "OPEN ••• FOR INPUT"
statement: xl t,hrough xn represent variable names.
When the BASIC program reaches the INPUT# statement du.ring execution,
the data is automatically called into the program from cassette and
execution continues. INPUT# statements and INPUT statements may be
interspersed throughout a program. The input file need only be opened
once before it is referenced.

PRINT
The PRINT stat,ement is used to output results
comments, values of variables, or plot points
console terminal. The format is:

of computations,
of a graph on the

(line number) PRIN'r expression
When no expression is indicated in the statement line, a blank line is
output. For example:
?(15 DR I NT
?l(~

PRI:\IT

Two blank lines will be output on the console terminal.
By using
certain kinds of expressions and the control characters colon and
semicolon, the user can create fairly sophisticated formats.

6-16

In order to print out the results of a computation and the value of a
variable, the user types the line number, PRINT, and the variable
name{s) separated by a format control character (in this case, commas)
as follows:
5 A=16\B=5\C=4
10 PRINT A,C+B,SQR(A)

In BASIC, an output line is formatted into five columns (called print
zones)
of 14 spaces each. The control character comma causes a value
to be typed beginning at the next available print zone. In the above
example, the value of A, the sum of A+B, and the square root of A are
printed in the first three print zones as follows:
RUN
16

A statement such as in line number 10 in this next example:
5 A=2.3\B=21\C=156.75\D=1.134\E=23.4
10 PRINT A,B,C,D,E

causes the values of the variables to be printed in
using all five zones:
RUN
2.3

the

same

format

1 .134

23.4

When more than five variables are listed in the PRINT
sixth value begins a new line of output.

statement,

156.75

the

The PRINT statement may also be used to output a message or line of
text.
The desired message is simply placed in quotation marks in the
PRINT statement as follows:
10 PRINT "THIS IS A TEST II

when line
printed:

i.s

encountered

during

execution,

the

following

THIS IS A TEST

A message may be combined with
variable as follows:

the

result

calculation

80 PRINT IIAMOUNT PER PAYMENT =",R

Assuming R=344.96, when line 80 is encountered during
results are output as:
AMOUNT PER PAYMENT

execution,

the

344.96

If a number following a printed message is too long to be printed on a
single line, the number is automatically moved to the beginning of the
next line.
It is not necessary to use the standard 5-zone format for output. The
control character semicolon (;) causes the text or data to be output

6-17

immediately after the last character printed (separated from that
character by a space and followed by another space). If neither a
Thus both
comma nor a semicolon is used, BASIC ,~ssumes a semicolon.
of the following:
80 PRINT "AMOUNT PER PAYMENT ="R
80 PRINT "AMOUNT PER PAYMENT =";Ft

result in:
AMOUNT PER PAYMENT = 344.96

The PRINT statement can also cause a Gonstant to be printed on the
console terminal.
(This is similar to the PRINT command used in
Immediate Mode.) For example:
10 PRINT

1.234~SQR(10014)

causes the following to be output at 4;!xecution time:
1.234

100.07

Any algebraic expression in a PRINT s·tatement is evaluated using the
current value of the variables. Nmru)ers are printed according to the
format discussed in Section 6.3.
The following example program illustrates the use of the control
characters comma and semicolon in PRINT statements. The user may also
wish to refer to Section 6.8.12 for information pertaining to three
functions available for additional character control--TAB, PUT, and
GET:

10 READ A~B~C
20 PRINT A,B~C~At2,Bt2,Ct2
30 PRINT
40 PRINT A;B;C;At2;Bt2;Ct2
50 DATA 4~5,6
60 END
RUN
4

36
4

READY.

Another use of the PRINT statement is to combine it. with an
statement so as to identify the da·ta expected to be entered.
example, consider the following progr.am:

6-18

INPUT
As an

10 REM - PROGRAM TO COMPUTE INTEREST PAYMENTS
20 PRINT "INTEREST IN PERCENT";
25 INPUT J
26 LET J=J/100
30 PRINT "AMOUNT OF LOAN";
35 INPUT A
40 PRI NT "NUMBER OF YEARS";
45 INPUT N
50 PRINT "NUMBER OF PAYMENTS PER YEAR";
55 INPUT M
60 LET N=N*M
65 LET I=J/M
70 LET B=1 +1
75 LET R=A*I/(1-1/BtN)
78 PRINT
80 PRINT "AMOUNT PER PAYMENT =";R
85 PRINT "TOTAL INTEREST
=";R*N-A
88 PRINT
90 LET B=A
95 PRINT" INTEREST
APP TO PRIN
BALANCE"
100 LET L=B* I
110 LET P=R-L
120 LET B=B-P
130 PRINT L"P .. B
140 IF B>=RGO TO 100
150 PRINT B*I .. R-B*I
160 PRINT "LAST PAYMENT ="B*I+B
200 END
HUN
INTEREST IN PERCENT?9
AMOUNT OF LOAN?2500
NUMBER OF YEARS?2
NUMBER OF PAYMENTS PER YEAR?4
AMOUNT PER PAYMENT = 344.9617
TOTAL INTEREST
= 25~.6932
APP TO PRIN
INTEREST
288.7117
56.25
295.2077
49.75399
301.8498
43.11182
308.6415
36.32019
315.5859
29.37576
322.6866
22.27508
329.947
15.01463
337.3708
7.590824
LAST PAYMENT = 344.9608

BALtlNCE
2211 •. 288
1916 •. 081
1614 •. 231
1305 •. 589
990. fl03 5
667.~117

337 .~1699

READY.

As can be noticed in this example, the question mark is grammatically
useful when several values are to be i.nput by allowing the programmer
to formulate a verbal question which the input values will answer.

6-19

PRINT#
The PRINT# statement is similar to t:he PRINT stab:!ment with the
exception that data and messages are sent to the cur:rent output file
on cassette rather than to the console terminal.
Thl:! form of the
statement is:
(line number) PRINTf: xl, x2 , ••• xn
where # signifiE:!s that the output will be sent to the cassette drive
number and filename of the currently open output file, and xl through
xn represent data variables.
(The current open file iB determined by
the OPEN FOR OUTPUT statement, as detailed earlier in 1::his section.)
If the user attempts to save data on a full cassette, BASIC prints an
error message and returns control to its editing phase. The data
already output is lost, and the user will have to rerun his program
using a different output cassette.

COMMAS and NO COMMAS
Data stored in an output file on cassette is often called later as
input by another or the same program.
(This is in fact the only
method of passing data between segments of a chained program.)
In
order to be use~d as input, this data m.ust be in the sa.me format as it
would appear if written in a DATA statement. Cassette BASIC provides
two statements for formatting this output--COr.1MAS and NO COMMAS.
In order to be used as data, individual values must be separated by
commas; the COMMAS statement inserts a comma after eac:h item of data;
(unless the COMMAS statement is inserted in the program prior to
PRINT# statement, data will be output in the format illustrated
eariier under the PRINT statement.) The form is:
{line number> COMMAS
A NO COMMAS stat:ement will set the format back to its original state.
The COMMAS and NO COMMAS statements do not affect output on either the
console terminal or line printer.
The following example
"OUT. OAT" , reads the
console terminal.

writes out four values in a file called
values back into memory and prints them on the

10 OPEN "1:0iJT.DAT" FOn OUTPUT
15 COMMAS

20 PRINT' 1;2;3;4
30 CLOSE

40 OPF:N "1:0IJT.DAT I f FOR INPUT
50 INPUT# I~J~K~L
60 PR.INT I,J~K~L
73 END

Output appears as follows:
RUN
1

READY.

6-20

The COMMAS statement is not necessary if the user is only sending one
value per line.
The preceding example could have been coded as
follows, with the same results:
.
10 OPEN "1:0UT.DAT" FOR OUTPUT
20 FOR 1=1 TO 4
30 PRINT# I
40 NEXT I
50 CLOSE
60 OPEN "1:0UT.DAT" FOR INPUT
70 INPUTI I,J,K,L
80 PRINT I,J,K,L
90 END

In this case the file OUT. OAT would appe,ar:
1
2

3
4

whereas in the first case it would appear as follows:

The user must take care when inputting data from cassette files.
example, if the file OUT. OAT is in the form:

and the user attempts
statement:

input

these

values

using

the

For

following

the proper values for I, J, and K will he read, but the rest of the
line will be lost as far as satisfying any future variables--just as
it would be lost if these values were input from the console terminal.
(Refer to the information concerning the INPUT statement in this
section. )

LPT

The LPT statement is used to generate output on the line
one is available) and is of the form:

printer

(if

(line number) LPT
By inserting this statement anywhere in a program, all subsequent
output, with the exception of error messages, will be printed on the
line printer. The LPT statement is particularly advantageous for
outputting large amounts of calculated data, as can be seen from this

6-21

and following examples:
100
110
120
130
140

LPT
FOR F=30 TO 60 STEP 3
PRINT F"Ff2
NEXT F

END

huN

30
33

q00
1089

129&

t 5tH
17&4

42
45
48

2025
2304

2&01

291&

324q

3~00

When the END statement is encountered in
device is reset to the console terminal.

the

program,

the

output

TTY OUT
The console terminal may be placed under program control so that
during execution of a program output may be sent alte:rnately between
the console terminal and the line printe~r (if one is ava.ilable on the
system) •
Control is originally set with the console terminal.
B:{
issuing the
LPT statement discussed previously, all subsequent output can be sent
to the line printer.
To return control to the console terminal from
within the program, the statement:
(line number) T'I'Y OUT
is inserted.
(Cassette I/O always returns control to the last device
indicated, so that the TTY OUT statement need only bl~ used when the
line printer is involved.)
The following program makes use of almost all the available I/O
devices.
The console terminal and line printer output is included.
5 HEM PROGRAM TO DEMONSTHATE 4LL 110 DEVICgS
1~ REM AVAILABLE IN CASSETTE BASIC
15 REM
20 PR I NT "PHOGHAM TO CALCfJLATE SOIJA,RES AND SOfJARE HOOTS"
25 PRINT
27 REM GET LOOP LIMITS FROM USER
30 PRINT "INprTT LOWER LIMIT"
35 I NPT]T L
40 PRINT "INpT]T TJPPEH LIMIT"
45 INPUT U
50 PR I NT "I Npr]T STEP"
55 I NprJT S
57 HEM CREATE A CASSETTE FILE OF SQIJARES OF Nr)MBERS
60 OPEN "1: snfJARE. DAT"FOR Of]TPI]T

6-22

65 LPT
66 RSM PRINT A F'OHM F~F:D ON LINEPRl:'<J1EH
70 T =prJT ( 12 )
75 PH I NT "TABLE OF ;\JrJMBERS AND THE 1 R S()!JAHES"
80 PRINT
81 PHINT
II
X"," Xf2"
[12 PRINT
~3 PRINT
~5 FOR X=L TO /J STEP S
90 PHINT x,xn~
95 RF:M ALSO SF:ND S()fJARf.::S TO CASSF.TT~ FILE:
100 P~INT# Xn:~
H,5 NEXT X
1~6 CLOSE
110 T=prJT(l:l,)
111 TTY orJ1
112 PH I NT "TABLE OF SIJ'JAHES C OMDLETE"
113 LPT
115 PR I NT "TABLE OF ~\J;JM8ERS AND THE: I H 50! JARE ROOT S I I
12(71 OPE\} "I :SOi1AR~:.DAT"F'OR Il'JprJT
125 PRINT
126 P:'iINT
127 ~RINT " X"," SnR(X)"
128 PRINT
130 FOR X=L TO 'J STEP S
135 INP;JT# J
136 PRINT J,SOR(J)
140 i\lEXT X
150 T=P;JT( 1~)
155 TTY or)T
160 PRINT "PHOGHAM COMPLETED"
165 END

H,uN
PROGRAM TO CALCTJLATE SnrJARES AND S0rJARE ROOTS
I \JDIJT LOWER LIMIT

11
I:'lprJT fJPPEH LIMIT
1591

INprJT STEP
71

TABLE OF' S();JARES

COMPLETE

6-23

Ar~1,)

TA8LE Of' MJtviBE.RS

THE-If.( SQUARES

)(-2

)(

1
2

"
q

:~
i1

2':5
3h

(-.

1
8

1 V'

1?!0

2"0',

'i0

25~C1

,.."

)(

~QK(X)

1
?
3

9
1 f,

25
-~

':'
t-

,.,

1.19

'1 v

t 9l

;.>4 v' 1

2 ':'r,'~

') ~~

6-24

NOTE
If an LT33 Teletype i.s used as the
console
terminal and it includes a
reader and punch, these devices may be
used for I/O operations at any time; no
special statement is required. To read
in data from the reader, position the
tape over the sprocket \t;rheel; when input
is required, set the realder to START and
the tape will begin reading in.
To
punch a tape, set the! punch to ON and
all Teletype output will be punched on
the punch.
Using the! paper tape I/O
devices is, in effect, t~he same as using
the Teletype keyboard. Characters will
be typed on the Teletype keyboard as
tapes are being read or punched.

6.B.6 Creating Run-Time Input Files
Data files stored on cassette and used for input during execution can
be created either by use of BASIC itself or by use of the CAPS-B
EDITOR.
Using BASIC, the programmer creates a program which accepts values
from the console terminal keyboard and then writes these onto the
cassette as an output file. Data files consist of consecutive ASCII
characters.
If the useful data in a file is to end before the actual
end-of-file, the last useful character must be followed by a CTRL/Z.
(This character is inserted by BASIC when the user closes an output
file. When later detected during input:, BASIC sets an end-of-file
flag; the user can test an end-of-fiIE~ condition by using the IF-END#
statement.) The COMMAS statement is uSE~d to produce the correct format
for a data file when more than one value is on a single line.
The following program illustrates one method of doing this:

5 REM - PROGRAM TO ACCEPT DATA FROM THE CONSOLE
10 REM - TERMINAL AND CREATE A. RUNTIME INPUT FILE
20 OPEN "0:RTIN.DAT" FO!={ OUTPUT
25 PRINT "INPUT A"B"C"D";
30 INPUT A"B"C,D
35 COMMAS
40 PRINTH A"B"C"D
45 PRINT "INPUT FeI) FOR 1=1 TO 1~1"
50 DIM F( HD
52 REM - COMMAS NOT NEEDED SINCE t:~RRAY WILL
53 REM - BE OUTPUT ONE ELEMENT PER LINE
55 NO COMMAS
60 FOR 1=1 TO 10
70 PRINT "F("I")";
7 5 I NP UT F ( I )
80 PR I NT # F ( I )
85 NEXT I
90 PRINT I I INPUT Vl"V2"Z"
95 INPUT Vl "V2" Z
97 REM
CO~M.4S ARE NEEDED SINCE i} 1 " V2 AND Z
98 REM - \vILL BE OUTPUT ON THE SAt1E LI NE

6-25

1 tHtJ COMMAS

105 PRINT# Vl,V2,Z
110 CLOST<':
115 END
nUN
S.AVE

UNIT#(O··7) :0

READY.

The CAPS-8 EDITOR can also be used to create an input file.
The
EDITOR first asks for input and output devices and filenames; then the
user types the file using EDITOR commands and making sure the format
is correct for BASIC. The same data file in the above example can be
created using the EDITOR as follows:

!..R EDI T

*IN?UT FILE*Q0r~Jr FILE-0znfIN.DAT

JLA
1.37,2.346,-13.267,-1.056
23
3.56
1 .436
38
9.026
23.1967
89
5Ll

12.467
-1

123,34567,789

!L
1.37,2.346,-13.267,-1.056
23
3.56
1.436
38
9.026
23.067
f59

54
12.467
-1

123,34567,789

JtE

6-26

6.8.7 Loops (FOR, NEXT and STEP)
A loop is a set of instructions which are repeated over and over
again, each time being modified in some way until a terminal condition
is reached. FOR and NEXT statements define the beginning and end of a
loop; STEP specifies an incremental value. The FOR statement is of
the form:
(line number) FOR v=xl TO x2 STEP x3
where v represents a variable name, and xl, x2, and x3 all represent
formulas
(a formula in this case means a numerical value, variable
name, or mathematical expression). v is termed the index, xl the
initial value, x2 the terminal value, and x3 the incremental value.
For example:
15 FOR K=2 TO 20 STEP 2

This loop will be repeated as long as K is less than or equal to 20.
Each time through the loop, K is incremented by 2, so the loop will be
executed a total of 10 times.
A variable used as an index in a FOR statement must not be
subscripted,
although a common use of loops is to deal with
subscripted variables using the value of the index as the subscript of
a previously defined variable (this is illustrated in Section 6.8.8,
Subscripted Variables).
The NEXT statement is of the form:
(line number) NEXT v
where v is the index of the FOR loop and signals the end of the loop.
When execution of the loop reaches the NEXT statement, the computer
adds the STEP value to the index and checks to see if the index is
less than or equal to the .terminal value.
If so, the loop is executed
again. If the value of the index exceeds the terminal value, control
falls through the loop to the following statement, with the value of
the index equaling the value it was assigned the final time through
the loop.
(Note that this method of handling loops varies among other
versions of the BASIC language.)
If the STEP value is omitted, a value of +1 is assumed.
(Since +1 is
the usual STEP value, that portion of the statement is frequently
omitted.) The STEP value may also be a negative number.
The following example illustrates the use of loops.
This loop is
executed 10 times: the value of I is 10 when control leaves the loop.
+1 is the assumed STEP value.
10

FOR 1=1 TO 10

20 NEXT I
30 PRINT I
40 END

RUN
10

READY.

6-27

If line 10 had been:
10 FOR 1=10 TO 1 STEP -1

the value printed by the computer would be 1.
As indicated earlier, the numbers used in the FOR statement are
formulas; these formulas are evaluabed upon first encountering the
loop. While the index, initial, terminal and STEP values may be
changed within the loop, the value assigned to the initial formula
remains as originally defined until the terminal condition is reached.
To illustrate this point, consider the previous example. The value of
I (in line 10) ca.n be successfully chang1ed as follows:
10 FOR 1=1 TO 10
15 LET 1=10
20 NEXT I

The loop will only be executed once since the value 10 has been
reached by the variable I and the terminal condition is satisfied.
If the value of the counter variable is originally set equal to the
terminal value, the loop will executE:! once, regardless of the STEP
value. If the starting value is beyond 1:he terminal value, the loop
will also execute only once.
It is possible to exit from a FOR-NEXT loop without the index reaching
the terminal value.
This is known as a conditional transfer and is
explained in Section 6.8.9. Control may only transfer into a loop
which has been left earlier without beinq completed, ensuring that the
terminal and STEP values are assigned.

Nesting Loops
It is often useful to have one or more loops within a loop.
This
technique is called nesting, and is allowed as long as the field of
one loop (the numbered lines from the FOR statement
to
the
corresponding NEXT statement, inclusivE~) does not cros:; the field of
another loop. A diagram is the best way to illustrat.e acceptable
nesting procedures:
ACCEPTABLE NESTING
TECHNIQUES

UNACCEPTABIJE NESTING
TECHNIQUES

Two Level Nesting

' r~g~

~EXT

FOR

[NEXT
-NEXT

~'OR

E'OR

-NEXT
NEXT

6-28

Three Level Nesting
FOR
OR
r FOR
l-NEXT
FOR
r
[ l-NEXT
NEXT
NEXT

-FOR

-FOR
[ -NEXT
-FOR
'NEXT
-NEXT
-NEXT

A maximum of eight (8) levels of nesting' is permitted.
limit will result in the error message:

Exceeding that

FOR ERROR AT LINE XXXX
where XXXX is the number of the line in which the error occurred.

6.8.8

Subscripted variables

In addition to single variable names, BASIC accepts another class of
variables called subscripted variables. Subscripted variables provide
the programmer with additonal computing capabilities for handling
lists, tables, matrices, or any set of related variables. Variables
are allowed one or two subscripts. A single letter forms the name of
the variable, followed by one or two integers in parentheses,
separated by a comma, indicating the place of that variable in the
list.
Up to 26 arrays are possible in any program (corresponding to
the letters of the alphabet), subject only to the amount of memory
space available for data storage.
For example, a list might be
described as A(I) where I goes from 1 to 5, as follows:
A(l) ,A(2) ,A(3) ,A(4) ,A(5)
This allows the programmer to reference each of the five elements in
the list A.
A two dimensional matrix A{I,J) can be defined in a
similar manner, but the subscriped variable A can only be used once
(i.e., A{I)
and A{I,J)
cannot be used in the same program). It is
possible however, to use the same variable name as both a subscripted
and an unsubscripted variable.
That is, both A and A(I) are valid
variable names for use in the same program.
Subscripted variables allow data to be input quickly and easily, as
illustrated in the following program (the index of the FOR statement
in lines 20, 42 and 44 is used as the subscript):
10 REM - PROGRAM DEMONSTRATING READING
REM - OF S!J8SCH I PTED VAR I ABLES
15 DIM A(5)IR(213)
18 PRINT "A(I) WHl-:RE A=1 TO 5;"
20 FOR 1=1 TO 5
25 READ A( I)
30 PH I ~T A ( I ) ;
35 NEXT I
11

38 PRINT
39 PRINT
40 PRINT "BC IIJ)
41 PRINT"
42 F' on I 1 TO 2

WHl':HE 1=1
A'\lD
J=1

TO ? ...
TO 3:"

6-29

43 PRINT
44 FOR J=1 TO 3
48 HEAD B(IIJ)
50 PH 1 NT R ( 1 1 J) ;
55 NEXT J
56 '~EXT 1
60 DATA 112131415161718
61 DATA 811161514131211
65 END
WJN

A(I) WHERE A=1 TO 5;
1

8( I, J)

wHERE:

AND
6
R

7
7

1=1 TO 2 :
J=1 TO 3:

8
6

HP,ADY.

DIM
From the preceding example, it can be se,en that the use of subscripts
requires a dimension (DIM) statement to define the maJ<:imum number of
elements in the array. The DIM statement is of the form:
(line number) DIM vl(nl), v2(n2,m2)
where v indicates an array variable name and nand m are integer
nwnbers indicati.ng the largest subscript value requi.red during the
program. For example:
15 DIM A(6110)

The first element: of every array is automatically assumed to have a
subscript of zero.
Dimensioning A(6,lO) sets up room for an array
with 7 rows and 1.1 columns. This matrix can be thought of as existing
in the following form:
AO,O AO,l
Al,O Al,l
A2,O A2,1

AO,lO
AI,lO
A2,lO

A6,O A6,1 •••

A6,lO

and is illustrated in the following program:

6-30

10 REM - MATRIX CHECK PROGRAM
15 DIM A(6,10)
20 FOR 1=0 TO 6
22 LET A(I,0)=I
25 FOR J=0 TO 10
28 LET A(0,J)=J
30 P R I NT A ( I , J) ;
35 NEXT J
40 PRINT
45 NEXT I
50 END
RUN
0 1
1 0
2 0
3 0
4 0
5 0
6
0

0
0

0
0
(1

0
0
0

5
0
0
0

6
0
0

7
0

0
0

8
0
0
0
0
0
0

0
13
0

0
{~

0
0

READY.

Notice that a variable assumes a value of zero until another value has
been assigned.
If the user wishes to conserve memory space by not
making use of the extra variables set up within the array, he should
set his DIM statement to one less than necessary, i.e. DIM A{5,9).
This results in a 6 by 10 array which may then be referenced beginning
with the A (O,O) element.
More than one array can be defined in a single DIM statement:
10 DIM A(20), 8(4,7)

This dimensions both the list A and the matrix B.
A number must be used to define the maximum size of the array. A
variable inside the parentheses is not acceptable and will result in
an error message by BASIC at run-time.
The amount of memory not
filled by the program will determine the amount of data the computer
can accept as input to the program at anyone time.
In some programs
a TOO-BIG ERROR may occur, indicatinc;r that memory will not hold an
array of the size requested.
In that evemt, the user should change
his program to process part of the datcL in one run and then chain to
another section to process the rest (see Section 6.8.10).

6.8.9

Transfer of Control Statements

Certain control statements cause the execution of a program to jump to
a different line either unconditionally or as a result of some
condition within the program. Looping is one method of jumping to a
designated point until a condition is nlet. The following statements
give the progranuner added capabilities in this area.

6-31

Unconditional Transfer (GOTO)
The GOTO (or GO TO) statement is an unconditional statE!ment
direct program <::ontrol either forward or back in a pro9ram.
of the GOTO statement is:

used to
The form

(line number) GOTO n
where n represents a statement number. When the logic ()f the program
reaches the GOT 0 statement, the statement(s) immediately following
will not be executed: instead execution is transferred to the
statement beginning with the indicated line number.
The following program never ends: it does a READ, prints something,
and jumps back to the READ via a GOTO statement. Ii: atempts to do
this over and over until it runs out of data, which is an acceptable,
though not advisable, way to end a program.
10 HEM - PROGHAM ENDING WITH ERROR
11 .REM - MESSAGE Wy~~ O~T OF DATA
20 HEAD X
25 PRINT "X="XI"XT2="XT2
30 GO TO 20
35 DATA 115110115120125
40 END
HfJN
X=
X=
X=
X=
X=

1
5

10
15

X= 25

Xt2=
XT2=
Xt2=
Xt2=
Xf2=
Xf2=

10'1
225
400
f)~5

DATA ERROR AT LINE 20

Conditional Transfer (IF THEN and IF GOT 0)
A program sometimes requires that two values be compared at some
point; control of program execution may be directE!d to different
procedures depending upon the result of the comparison.
In computing,
values are logically tested to see whether they are equal, greater
than, less than another value, or possibly a combination of the three.
This is accomplished by use of the relational operators discussed in
section 6.5.3.
IF THEN and IF GOTO statements allow the programmer to test the
relationship
between
two
formulas
(variables,
numbers,
or
expressions).
Providing the relation.ship described in
the
IF
statement is true at the point it is tested, c()ntrol will be
transfered to the line number specified, or the indicated operation
will be performed. The statements are of the form:
(line number) IF vI <relation> v2 GOTO [or THEN]

6-32

where vl and v2 represent variable names or expressions, and x
represents a line number or an operation to be performed. The use of
either THEN or GOTO is acceptable.
The following two examples are equivalent (the value of the variable A
is changed or remains the same dependin9 upon A's relation to B) :

100 IF A>B THEN 120
110 A=A t8-1
120 C=A/D

100 IF A<=8 THEN A=AtB-l
110 C=A/D

IF ENOl
The IF ENOl statement is used to verify an end-of-file
during run-time input. The form of this statement is:

condition

(line number) IF ENOl THEN n
IF ENOl instructs BASIC to perform a ch.~ck on the validity of the last
INPUT I
statement referencing the currently open input file; n
represents a line number or operation to be performed.
If an
end-of-file (CTRL/Z) was detected during the last INPUTI statement,
BASIC transfers control to the specified line number or performs the
indicated operation.
If an end-of-file was not detected, then no
operation occurs. For example:

150 OPEN "1: VALUE" FOR INPUT
200 INPUT# A,B,C
210 IF END# THEN 530
215 LET X=SGNCA)
530 PRINT "INPUT FILE--NOT ENOUGH DATA"
535 STOP

6-33

In this example the programmer provides his own error message if there
is an insufficient number of values for his variables. If there are
two valid numbers remaining in the input file when stcLtement 200 is
reached, then the variables A and Bwill receive valid input. When
the program attempts to input a value for C, BASIC ~rill detect an
end-of-file and return a value of zero for C. As it executes the IF
END# statement, BASIC will note that it has ju~:t reached the
end-of-file, and will transfer control to statement nun~er 530, as the
user intended.
However, assume that as line 200 is executed there is only one valid
data value left in the input file.
An end-of-file is detected this
time when BASIC tries to read a value for B; B is set t~o zero.
When
BASIC attempts t:o continue reading a value for C, an EOF ERROR will be
returned (see Section 6.12) and program execution will terminate since
the user has tried to read past the end-of-file. A good way of
circumventing this condition is to include both the INPUT# and the IF
END# statements in a loop and input one value at a time. Using this
method allows the programmer's own error message to be printed before
BASIC is allowed to read past the end-of-file.

6.8.10 Program Chaining (CHAIN)
Since Cassette BASIC allows at most only 2K words of memory for
program storage, it is possible that a program may be t~oo large to fit
in memory at one time. However, Cassette BASIC compen~:ates for this
by allowing different segments of a program to be stored on cassette
and called as needed. Although each program segment is restricted to
2K of memory, total program length is effectively unlimited. The form
of the CHAIN statement is:
(line number) CHAIN "n:XXXX"
where n is the cassette drive number, and XXXX is the name of the file
to be chained to. The CHAIN statement should be the last statement in
the user's program. When BASIC transfers to the program specified in
the statement, it removes the old program from memory. Data is not
passed in memory during the chain, so the user should be careful to
save any data he will need in an output file.
(See Section
6.8.5--PRINT#.) The chain automatically closes any open output file,
transfers control to the lowest statement number in t:he new program,
and continues execution.
For example, the following section of a program stores some
values on an output cassette and chains to a file callE~d PART2:

450 OPEN "1.: DATA." FOR OUTPUT
4 55 COMMA.S
460 PRINT# B,C,D,G,H,Z
465 NO COMMAS
410 FOR 1=1 TO 10
415 PRINTH A( I)
480 NEXT I
485 CLOSE
490 CHAIN "1 :PART2"

6-34

data

The values stored by this section of the program in the cassette file
DATA can be read in by the second section of the program--PART2--and
can continue to be used. PART2 might appear as follows:
1 DIM A(10)
5 OPEN "1: DATA" FOR INPUT
10 INPUT# B,C,D,G,H,Z
15 FOR 1=1 TO 10
20 INPUT/! A.(I)
25 NEXT I

6.8.11 Subroutines (GOSUB and RETURN)
A subroutine is a section of code performing some
required at more than one point in the program.
I/O operation for a volume of data, a mathematical
too complex for a user-defined function, or
processes may best be performed in a subroutine.

operation that is
Often a complicated
evaluation which is
any number of other

Subroutines are generally placed physically at the end of a program,
usually before DATA statements, if any, and always before the END
statement. Two statements are used exclusively in BASIC to handle
subroutines; these are the GOSUB and RETURN statements.
A program begins execution and continues until it encounters
statement of the form:

GOSUB

(line number) GOSUB x
where x represents the first line number of the
then transfers to that line. For example:

subroutine.

Control

50 GOSUB 2'2)0

When program execution reaches line 50, control transfers to line 200,
and the subroutine is processed until execution encounters a RETURN
statement of the form:
(line number) RETURN
The RETURN statement causes control to return to the statement
following the GOSUB statement. Before transferring to the subroutine,
BASIC internally records the next statement to be processed after the
GOSUB statement; thus the RETURN statement is a signal to transfer
control to this statement.
In this way, no matter how many different
subroutines are called, or how many times they are used, BASIC always
knows where to go next.
The following program demonstrates a simple subroutine:

6-35

1 REM - THIS PROGRAM ILLUSTRATES GOSUB AND RETURN
10 DEF FNA(X)=ABSCINTCX»
20 INPUT A.. B .. C
30 GOSUB 1 '~0
40 LET A=FNACA)
50 LET S=FNACB)
60 LET C =FNACC)
70 PRINT
80 GOSUS 1"0
90 STOP
100 REM - THIS SUBROUTINE PRINTS OUT THE SOLUTIONS
110 REM - OF THE EQUATION: ACXt2) + SCX) + C = 0
120 PRINT "THE EQUATION IS
"A"*Xt2
+
"B"*X
+
130 LET D=B*B-4*A*C
140 IF D<>0 THEN 170
150 PRINT "ONLY ONE SOLUTION ••• X ="-B/C2*A)
160 RETURN
170 IF D<0 THEN 200
180 PRINT "TWO SOLUTIONS ••• X =";
185 PRINT (-B+SQR(D»/(2*A)"AND X ="C-B-SQRCD»/(H*A)
190 RETURN
200 PRINT "IMAGINARY SOLUTIONS ••• X = cn;
205 PRINT ··B/C2*A)" .. "SQRC -D)/C2*A)") AND C";
207 PRINT -B/C2*A) ...... -SQR( -D)/C2*A,)")"
210 RETURN
900 END

RUN
?1 ... 5 .. -.5

THE EQUATION IS
1 *Xt2
+
TWO SOLUTIONS ••• X = .5 AND X =-1

.5 *X

THE EQUATION IS
1 *Xt2
I MAG I NARY SOLUT IONS. •• X =

0 *X

o .. 1 ) AND

-.5

+
0

.. -1

RFADY.

Line 100 begins the subroutine. There are several places in which
control may return to the main prog'ram, depending upon the flow of
control through the various IF statements. The subrou1:ine is called
from line 30 and again from line 80. ~hen control returns to line 90,
the program encounters the STOP statement and execution is terminated.
It is importan1: to remember that subroutines should gE!nerally be kept
distinct from the main program.
The last statemen1: in the main
program should be a STOP or GOT 0 statement, and subroutines are
normally placed following this statement. A useful practice is to
assign dis tinc1:i ve line numbers to subroutines. For example, if the
main program is numbered with line numb,ers up to 199, 1:hen 200 and 300
could be used as the first numbers of t,wo subroutines.

Nesting Subroutines
Nesting of subroutines occurs when one subroutine calls another
subroutine.
If a RETURN statement is encountered during execution of
a subroutine, control returns to the statement follo\ling the GOSUB

6-36

which called it. From this point, it is possible to transfer to the
beginning or any part of a subroutine, even back to the calling
subroutine.
Multiple
entry points and RETURN statements make
subroutines more versatile.
The maximum level of GOSUB nesting is about ten (decimal)
levels,
which should prove more than adequate for all normal uses. Exceeding
this limit will result in the message:
GOSUB ERROR AT LINE XXXX
where XXXX represents the line number where the error occurred.
An
example of GOSUB nesting follows.
Execution has been stopped by
typing a CTRL/SHIFT/P combination (see section 6.11.4, Stopping a
Run), as the program would otherwise continue in an infinite loop.
10 REM - FACTORIAL PROGRAM USING GOSUB TO
15 REM - RECURSIVELY COMPUTE THE FACTORS
40 INPUT N
50 IF N>20 THEN 120
60 X=1
70 K=1
80 GOSUB 200
90 PRINT "FACTORIAL "N" ="X
110 GO TO 40
120 PRI NT "MUST BE 10 OR LESS"
130 GO TO 40
200 X=X*K
210 K=K+l
220 IF K<=N THEN GOSUB 200
230 RETURN
240 END
RUN
12
FACTORIAL
?4
FACTORIAL
75
FACTORIAL

= 24

= 120

STOP.
READY.

6.8.12 Functions
BASIC defines several mathematical calculations for the programmer,
eliminating the need for tables of trig' functions, square roots, and
logari thms. These functions have a 3-1et.ter call name, followed by an
argument, x, which can be a number, variable, expression, or another
function. Table 6-1 lists the functions available in Cassette BASIC.
Most are self-explanatory; those that; are not and are described in
greater detail are marked with an asterisk.

6-37

Table 6-1 Cassette BASIC Functions
Function

Meaning

SIN (x)

Sine of x (x is expressed i.n radians)
Cosine of x (x is expressed in radians)
Tangent of x (x is expressE!d in radians)
Arctangent of x (result is expressed
in radians)
e to the xth power (e=2.71E:282)
Natural log of x (logex)
Sign of x--assign a value Clf +1 if x is
positive, 0 if x is zero, or -1 if x
is negative
Integer value of x
Absolute value of x (I x I )
Square root of x (¥X)
Random numbter
Print next character at space x
Get a character from input device
Put a character on output device
User-defined function
User-coded function (machine language
code)

COS (x)
TAN (x)

ATN{x)
EXP (x)
LOG(x)
*SGN (x)
*INT (x)
ABS(x)
SQR(x)
*RND (x)
*TAB (x)
*GET (x)
*PUT (x)
*FNA(x)
*UUF (x)

Sign Function (SGN(x»
The sign function returns the value +1 if x is a positive value, 0 if
x is zero, and -1 if x is negative. For example, SGN(3.42)=1,
SGN(-42)=-1, and SGN(23-23)=O. The following example illustrates the
use of this function:

10 REM - SGN FUNCTIO:-J EXAMPLE:
20 READ A,B
25 Pn I NT "t\ =" A, "B ="B

30 PRINT "SGNCA)="SGNCA),"SGNCB)="SGNCB)
40 PRINT "SGNCINTCA»="SGNCINTCA»
50 DATA -7.32, .44
6(3 END

Integer Function (INT(x)}
The integer function returns the value of the nearest integer not
greater than x. For example, INT(34.67)=34. By specifying INT(x+.5)
the INT function can be used to round numbers to the nearest integer;
thus, INT(34.67+.5)=35. INT can also be used to round numbers to any
given decimal place by specifying:
INT(X*lOtD+.5)/lOtD
where D is the number of
program illustrates this
typing a CTRL/SHIFT/P:

decimal places desired.
function; ~:!xecution has

6-38

The following
been stopped by

10 REM - INT FUNCTION EXAMPLE
20 PRINT "NUMBER TO BE ROUNDED";
3(1 I NPUT A
40 PRINT "NO. OF DECIMAL PLACES";
50 INPUT D
60 LET B=INT(A*10fD+.5)/10fD
70 PRINT "A ROUNDED = "B
80 GO TO 20
90 END
RUN
NUMBER TO BE ROUNDED?55.65342
NO. OF DECIMAL PLACES?2
A ROUNDED = 55.65
NUMBER TO BE ROUNDED?78.375
NO. OF DEC I MAL PLAC ES?-2
A ROUNDED = 1(~0
NUMBER TO BE ROUNDED?67.89
NO. OF DECIMAL PLACES?-1
A ROUNDED = 70
NUMBER TO BE ROUNDED?
STOP.
READY.

If the argument is a negative number, the value returned is the
largest negative integer (rounded to the higher value) contained in
the number. For example, INT(-23)=-23 but INT(-14.39)=-IS.

Random Number Function (RND(x»
The random number function produces a random number n which is in the
range O<n<l. The numbers are not reproducible, a fact the programmer
should keep in mind when debugging or checking his program.
The
argument x in the RND(x)
function call can be any number, as that
value is ignored. The following program illustrates the use of this
function to generate a table of random numbers.
10 REM - RANDOM NUMBER EXA~PLE
25 PHI NT "RANDOM NUMBERS"
30 FOR 1=1 TO 30
40 PRINT RND(O),
50 NEXT I
60 END
RUN
RANDOM NUMBERS
.7759228
.4857633
.6156673
.3796163
.9547609
.05280478
READY.

.08069808
.4192038
.5921191
.2023254
.2890875
.3859534

.5008833
.1433537
.01170888
.7974058
.1416765
.8404774

6-39

.2790171
.08728769
.7411813
.9635064
.2482717
.5692836

.1661529
.2335427
.341708
.6043865
.2145417
.8514056

It is possible to generate random numbE:!rs over any range by using
following formula:

the

(B-A) *RND(O) +A
This produces a random number (n) in the range A<n<B. For example, in
order to obtain random digits in the range 0<n<9, line 40 in the
previous example is changed to read:
40 PRINT

9*RND(0)~

To obtain random integer digits, t:he INT functi·on is used in
conjunction with the RND function (using the same values for A and B
above) as follows:

When the program is run, the results will look as follows:
RUN
RANDOM NUMBERS
4

1
8
2
8
0
READY.

5
0
3
4
7
7

8
7
0
7
1

1
8
8
7
8
7

8
5
8
4

2
5

Notice that the range has changed to O<=n<:9. This is because the INT
function returns the value of the neare:st integer not qreater than n.

Tab Function (TAB(n»
The TAB function allows the user to position the printing of
characters anywhere on the teleprinter (or line printE!r) line. Print
positions can be thought of as being nu.mbered from 1 to 72 across the
console terminal line (1 to 80 across the line printer line) from left
to right. The form of this function is:
TAB(n)
where the argument n represents the position (from 1 to the total
number of spaces available) in which the next character will be typed.
For example, TAB(3) causes the character to be printed at position 3.
Each time the TAB function is used, positions are cOlmted from the
beginning of the line, not from the current position of the printing
head. For example, the following statement:
10 PRINT "X ='';TAB(3);,,/,t;3.14159

will print the slash on top of the equal sign, as shown below:
RUN
X

3.14159

6-40

The following is an example of the sort of graph
with BASIC using the TAB function:

that

can

drawn

30 FOR X=0 TO 15 STEP .5
40 PRINT TAB(30+15*SIN(X>*EXP(-.I*X»;,,*n
50 NEXT X
RUN
*

*
*
*

'"
* '"
*

*
*
*
*

*
*

**
**
*
*

PUT and GET Functions (PUT(x) , GET (x»
Cassette BASIC provides two additional functions, PUT and GET, to
increase input/output flexibility on the console terminal or line
printer. Using these statements, the programmer can "PUT" an ASCII
character on the current output device, or "GET" a character from the
current input device.
(ASCII character codes are listed in Appendix
A.) GET is of the form:
GET (x)
where the argument x is a dummy variable which may be any value.
GET (x) will be assigned the decimal value of the ASCII code of the
next character input on the current input device.
For example, if the following statement appears in a program:
10 LET L=GET(0)

6-41

and the next character input is an M, the variable L will be
the value 77(decimal).

assigned

PUT is of the form:
PUT (x)
where the argument x represents either the decimal valuE! of the ASCII
code of the character to be output, or the characte~r itself. For
example, the statement:
15 L=PUT(GET(V»

will wait for a character to be read from the current ir..put device and
then print it on the current output device. A statement. such as:
30 PRINT PUT(Q)

will print the character typed as well as the decimal value of the
ASCII code for that character.
(Since both the cha,racter and the
decimal value are typed, PUT and GET statements should not be used
with cassette files.)
NOTE
If the user is inputting characters from
paper tape via the paper tape reader on
an LT33 Teletype, he should be careful
to
position the tape on the first
character to be input. O,therwise blank
tape
may
be
entered,
which
is
interpreted as a "BREAK" and stops a
ru.nning program.
The PUT function can also be used to format output. For example, to
print a trig table on the line prin'ter with a heading and 50 data
lines per page, the form feed character (12 decimal) can be "PUT" to
the printer as follows:
100 LPT
110 GOSUB 1000
120 GOSUB 500
125 REM - SET UP TRIG TABLE
130 FOR J=0 TO 360 STEP .5
140 LET L=L+l
150 LET B=J/180*3.14
160 PRINT J,SINCB),COSCB),TANCB),ATNCB)
165 REM - PRINT 50 ENTRIES IN TABLE
170 IF L=50 THEN GOSUB 500
180 NEXT J
190 GOSUB 1000
200 GOSUB 1000
210 STOP
500 REM - PRINT HEADER
505 GOSUB 1000
510 PRINT
520 PRINT
530 PRI NT "ANGLE" I "s I NE" I"COSI NE" ,"TANGENT" I "ARCTANGENT"
540 PRINT
550 RETURN
1000 REM - PRINT FORM FEEDS TO ADVANCE PAPER
1005 X=PUT(12)
1010 L=0
1020 RETURN
1030 END

6-42

The beginning of the line printer output. from this program follows.
The first page of the table continues through an angle of 24.5
degrees: then the header and the next 50 entries are printed on the
next page,
and so on until the values have been output (in steps of
.5) for all angles through 360 degrees.

ANGLE

SINE

COSINE

TANGENT

ARCTANGENT

.. 5
1
1,5
2

8.722112E-01
.~H 14435&
,02616368
.03488181

.9998479

8,722444E-03
.01144621

2.5

.0435972Q
,052317..1945
,06101763

3
3.5
~

.0&CJ12117
.((11784194
.081111&7
,09579131
,\044757
,1131461
.1218019
,1304&04
.139103

8.5

.1~7735

4.5
5
5.5
&
6.§

7.5

.QQQqb2

.CJ9&92~5

,018bb164

.99&198b

,08144408

,995400CJ
.9945274
.9935184
.9925537
.9914535
,CJ902779
,989027

,1050506
,1138174
.1227211
.131585
,1404&81
.1493741

8.722001E .. 03
,017442&8
,02&1607
.03481474
.0435835
,052285&4
.0&097986
,0&966486
.07833935
.08700204
,095651&&
.10428619
,1129067
.lc15095
,1300944
.118&6
.147c052

.4554&45

,4038923

,QQQ6511

,02611261.&

,9993915
,CJ9904CJ2
,CJ98b30CJ

.0523811b

,99813b7

,0&1131S4

,CJ975&65

,0bCJ89125

l4.5

.03490305
,043&3878

,12I9&2]99J

FNA' Function (DEF FNA(x»
In some programs it may be necessary to execute the same mathematical
formula in several different p).aces..
Cassette BASIC allows the
programmer to define his own function in the BASIC language and then
call this function in the same manner as the square root or a trig
function is called.
Only one such user-defined function may be
included per program. The function is defined once at the beginning
of the program before its first use, and consists of a DEF statement
in combination with a 3-letter function name, the first two letters of
which must be FN. The format of the DE]~ FNA statement is as follows:
(line number) DEF FNA (:1{) =formula (x)
The A in the FNA portion of the statement may be any letter.
The
argument
(x) has no significance; it is strictly a dummy variable but
must be the same on each side of the equal sign. The function itself
can
be defined in terms of numbers, several variables, other
functions, or mathematical expressions.
For example:
10 DEF FNA(X)=Xt2+3*X+4
or

6-43

20 DEF FNC(X)=SQR(X+4)+1

The function:
10 DEF FNLCS)=St2

will cause the later statement:
20 LET R=FNA(4)+1

to be evaluated as R=17.
The user-defined function can be a function of only one variable.

User-Coded Function (UUF)
The user-coded function is explained in detail in the nE!xt section.

6.9 IMPLEMENTING A USER-CODED FUNCTION (UUF)
A special user-coded function is available in Cassette EASIC for the
programmer who is familiar with the PD]?-8 instruction set and 27-bit
mantissa floating-point format. BASIC's internal format is 27-bit,
sign-magni tude
mantissa floating-poin't; thus, all user-generated
values must be in that format and all coding must be compatible with
it.
The user codes the function in the PDP-8 series machine language
instructions, assembles it with the PALe Assembler, and loads the
resulting binary file as an overlay to one of the existing functions
(ATAN, LOG, etc.) Thus, while BASIC is running, this special function
can be requested and used in a fashion analogous to the built-in BASIC
functions.
The user-coded function, if present, is specified in the
BASIC program as:
UUF(n)
where n can be any BASIC expression.

6.9.1 Coding Formats
Due to memory restrictions, the user-codE!d function must replace one
or more of the existing Cassette BASIC functions. Table 6-2 lists the
functions which may be overlaid and the areas of memory they occupy.
Also listed is the transfer table address through whi.:h BASIC calls
the given extended function.

6-44

Table 6-2 Function 1\ddresses
Function

Locations Occupied

FNA
ATN

5453-5546
6200-6271
5412-5452
5350-5406
5547-5572

SQR

RND
TAB

~rransfer

Table Address
1131
1134
1137
1143
1147

The functions SIN, COS, and TAN are intE!rdependent, but all three may
be deleted as follows:
SIN
COS
TAN

5600-5674

1132
1133
1144

Almost a full page is freed by deleting
FNA

t~he

following:
1131
1137
1147

5412-5572

SQR
TAB

For each function replaced by the UUF, the user must set the
corresponding transfer table location to point to an erJ:-or routine so
that accidental
calls to that function will generate an error
condition rather than a spurious call to the UUF. The user does this
by inserting a statement such as the following in his UU1":
*1143
6441

IT t\BL~ ADDRSSS F'OH R\JI)
IPOI\JT€R TO SY\JfAX ERROH HO'JTINE

To include a user-coded function, all conventions required for the
PALC Assembler must be observed. The coding language is PDP-8 machine
language code, but can include instructions
in
1:he
modified
floating-point package, which is described later in this chapter in
section 6.10.
When floating-point statements are to be included in the program, it
is necessary only to indicate the start of floating-point notation by
including the following operator:
FENTER
immediately before the first floating-point statement:.
floating-point coding is terminated by the operator:

Similarly

FEXIT
immediately after the last floating-point statement. ThE!re can be as
many sections of floating-point code as necessary in thE! program, but
each must be delimited in this manner.

6-45

6.9.2 Floating-Point Format

The floating-point format used by Cassette BASIC allocates three
storage words i.n sign magnitude convention as follows
(in sign
magni tude convent.ion the sign bit rather than the mantissa, expresses
the sign of the entire number):

WORD 1

111111111

WORD 2

'---v---J~

WORD 3

ill] 1111111111111 [111111111111
--------~~~------------------~

EXPONENT

MANTISSA

SIGN BIT

Five memory locations are
accumulator, as follows:

used

represent

the

floating-point

Table 6-3 Floating-Point Accumulator
Location Name

Value

ACS

0024

Sign

ACE

0025

Exponent (200 octal biased:
i.e. the constant 200 is added
to the exponent to make the
range 0-377)

ACl

0020

High order word

AC2

0017

Mid order word

AC3

0016

Low order word

Contents

All of BASIC' s mathematical operations a.re in floating--point format:
therefore, if any temporary storage loc:ations are required by the UUF
subroutine, they must specify three words. For example:

6.9.3 Incorporating Subroutines with UUF'

When adding a user function, it becomes necessary to reference some of
Cassette BASIC's subroutines at specific: times in the coding. Most 6f
these calls are needed in order to preserve a compatible format
throughout the system. The BASIC subroutines which rna:, be referenced
are described below.
(The complete BASIC symbol table .is included as
Table 6-7 at the end of this chapter.)

6-46

BEGFIX
If a value is to be returned to the acc'l:lIllulator as a :resul t
of the
user function, that value must be in normalized floatinq-point format.
If floating-point arithmetic is used throughout the user function,
then
the valuE~ in the FAC (floati.ng-point accumulator)
is in
normalized floating-point format and need not be c:onverted.
If
fixed-point arithmetic is used anywhere in the func::tion, then the
subroutine BEGFIX must be referenced before the value (::loating-point)
is saved in ordE~r that the storage loca.tions are propel::-ly initialized
to accept a floating-point value.
Usingr this procedure, the five FAC
locations are prepared accordingly. However, because 1:he value to be
stored only requires 12 bits, a subse:quent DCA AC3 statement is
sufficient.
BEGFIX is located at 3760 and is called via a JMS
instruction.

ANORM
If a fixed-point value is added to the F'AC, ANORM normalizes the FAC
in order that it be in a format suitable for Casse"tte BASIC. The
routine supplies the acceptable values for the location!; ACE, ACS, ACI
and AC2. ANORM is assigned the location 4600.

FIX
To convert a value in the FAC to an integer, as wh~~n printing
character, the subroutine FIX is called; it is located at 4744.

6.9.4 Writing the Program
A user-coded function must res~t one of Cassette BASIC's tables to
recognize the function,
otherwise, UUF is cons ide l::-ed to be an
undefined function. The pointer is at location 1150; a statement such
as the following is required:

* 1150

UUr

Procedures for loading a user-coded function are contained in
6.11.5. Examples of user-coded functions follow.

Section

6.9.5 Examples of User-Coded Functions
Example l--This program calculates squares and square
series of values.. The BASIC program is as follows:
100 FOR A=33.1 TO 33.9 STEP
110 PHI~T A,f]TJF{A),SQR{A)
120 NEXT A
130 END

6-47

roots

for

The user-coded function is:
PALC-Vl

12/27/72

PA~E

I
I~SER-CODED FUNCTION TO
ISQUARES OF NUMBERS

CALC~LATE

01134

4435
20100
0200
601001
000101
6441
1134
6441

011150

1 1 501
62010

916200
016201
016202
(162013
(~6204

(162015

0'62016
062017
016210

62001
01010101
4435
2204
6203
0101010
5600
000101
010100
0100101
010101
3010101

ITHE FUNCTION LOADS INTO FIELD 01
IINTO THE AREA OCC~PIED RY THE 'ATN'
IFTJNCT ION
FENTER=4435
FST=20010
FWD=200
FMP=6@001
FEXIT=0I00101
SXERR=6441
*1134
SXERR
ISO REFERENCES TO ATN WILL
IYIELD AN ERROR
*11501
lJfJF
IDEF I NE fJfJF IN F'JNCT I ON TABLE
*6200
iJfjF,

FENTER IINTO FLT.PT.PKG.-A IS IN FAC
FST+FWD+X-.
ISAVE A
FMP+FWD+X-.
FEXIT
JMP I
rJTJF
IALL DONE
X,

1};0;0

FIELD
*301001

ITO START BASIC WHEN LOADED

$
P~\LC-Vl

FENTER
FEXIT
FMP
FST
FWD
SXERR
:f]F

4435
0101001
600101

62(~6

200101

02001
6441
6~"J0I

The output after execution is:
H;I~

33.1
33.2
33.3
33. LI

33.5
33.6
33.7
33.R
33.9

10195.61
1102.24
1108.89
1115.56
1122.25
112R.96
1135.69
1 14~. 4L,
1149.21

5.75326
5.761944
5.770615
5.779273
5. '187 91 R
5.796551
5.R~517

S.R13777
5.R22371

READY.

6-48

12/27/72

PAGF. 1-1

Example 2--The following program tests a student's ability to convert
the octal value in the console switches to its decimal equivalent.
Line 120 will set P equal to the decimal value of the setting.
Line
130 determines if the correct answer wa,s typed:
100 PRINT '''WHAT DF.:CIMAL VAUJE DO

11 0

T~E

S'JJITCHI<:S E0 i UIL?"

I ~p rJT \J

120 LET P=fJiJF(0)
130 IF P=N THEN ?00

140 PRINT "TRY AGAIN"
150 GO TO 100
200 PHINT "'CORRECT"
300 END

The user-coded function is:
PALC-Vl

1~/2117~

PAllE I

IIJSER-CODED I'IJ'\ICT I ON TO READ THE CONSULE
IS~ITCHES AND CU~VERT TO FLOATING POINT
I

ITHF: I"J:'-JCT I ON LOADS I "JTO l'I ELD lEBO
11 NTO THE AREA PREV I OIISLY OCCIIP IE: 0 BY
ITHE • RND' I'IJNCT IO"'J-T'IE HANDOM ,\J:IMREH
IliENERATOR
I

0000
4435
0000
4000
2000
Pl200
3160
4600
0016
6441

1'1ELD 0
I'ENTER=4435
I'EXIT=~A~0

F'tID=400et
I'ST=2000
nm=?0et
REll1'1X=3160
ANOHM=4600
AC3=16
SXERR=644 ~

01143

1143
6441

* 1143
SXERR

01150

1150
5350

*1150
lJIII'
'JlJI' ,

0HHH~

05351

4156

JMS I

(?J5352

7604

LAS

05353

3016

DCA

05354
05355
05356
05351

4151
5150
3760
00~1

3000

IDEI'INE 'JIll' IN I'IINCTION TARLE

*5350

5350
0535~

46~0

ISO REFERENCES ro H.\lO
IWILL YIELD AN EHHOH

'JRElll'IX IPHEPARE FOR
II"-.JTEGER VALJE
IGET CONrE'\JTS
101' Sill • HEG.
ISAVE IN LUW
AC3
10RDER I'/\C
IJANOlm /NOHMAL I ;:E
IHET,JRN
:1'11'

JMS I
JMP I
'}BEGI' I X, BEllI' I X
'J/\NORM, ANOHM
FIELD 1
ITO STAHT 'JP RASIC wHEN LOADED
*3000
$

PALC-Vl
0016
AC3
ANORM 460~
BEGl'IX 37M
4000
FAD
I'ENTF;R 4435
FEXIT 0000
201'J0
FST
0?00
FWD
SXERR 6441
'JANOHM 5351
']REG I' I 5356
5350
'JIJr

6-49

1~/21172

PAll!-: 1-1

An example of a run
switches follows:

which

200 (oct.al)

was

set

the

console

RfJN
WHAT DECIMAL VALUE DO THE SWITCHES EQUAL?
1120
TRY AGAIN
WHAT DECIMAL VAL'JE DO THE SWITCHES EQrJAL?
1128
CORRECT
READY.

6.10 FLOATING-POINT PACKAGE
Information concerning the PDP-8 modifi.ed Floating-Point Package which
the programmer will find useful in codi.ng a function follows.

6.10.1 Instruction Set
The legal instructions in the modified Floating-Point Package used
Cassette BASIC are explained in Table 6-4:
Table 6-4 Floating-Point Instructions
Meaning

Instruction Value
FST

2000

FLD

:3000

FAD
FSB

4000
5000

FMP

6000

FDV
FJMP
FENTER
FEXIT

7000
1000
4435
10000

FWD

0200

BKWD

0600

FSNE
FSEQ
FSGE
FSLT
FSGT
FSLE

0040
0050
0100
0110
0140
0150

Store the contents of the floating accumulator
(Fl~C).
The conten·t:s of the
FAC are not: changed.
Load FAC
with contents of
relative
address.
Add contents of relative address to FAC.
Subtract contents of relative
address
from FAC.
Multiply the contents of the FAC by the
contents of the relative address.
Divide FAC by contents of relative address.
Floating-point ~,ump to relative address.
Start floating-point code.
Exit floating-point code.
Return to PDP-8
code.
Access a relative location in the forward
direction.
Access a relative location in the backward
direction.
Skip if FAC <> ()
Skip if FAC = 0
Skip if FAC => ()
Skip if FAC <0
Skip if FAC >0
Skip if FAC <= ()

6-50

The following instructions require indirect (and relative) addressing
and therefore only address field 1. Their operation is the same as
the corresponding direct instruction.
Table 6-5 Relative Addresses
Instruction

Value

Operation

FSTI
FLDI
FAD I
FSBI
FMPI
FDVI
FJMPI

2400
3400
4400
5400
6400
7400
1400

Store
Load
Add
Subtract
Multiply
Divide
Jump

6.10.2 Addressing
The Floating-Point Package uses relative addressin;J.
Thus, all
statements that address a location must include one of the operators
FWD or BKWD plus a reference to the current location.
Such a
reference is generally in the form:
op code instruction + FWD (BKWD) + LTEMP-.
The operator FtoJD is used when the address of the location to be
referenced is numerically greater than the current a:ldressj BKWD is
used when the address of the location to be referenced is numerically
less than the current address. LTEMP··. in conjunction with the FWD
or BKWD operator defines the relative address of the location to be
operated on (LTEMP) with respect to the current location. This
relative displacement is then used by the Floating-Point Interpreter
to access the contents of the three words at LTEMP. This can best be
seen in an example:
4010 FAD+FHD+LTEMP-.

The contents of that location which is (4063-4010)
locations forward
from the current address, (i.e. the contents of LTEMP) , are added to
the FAC. Similarly:

152 FMP+BKWD+. -ALOe

At line 152 the contents of FAC are mu11:iplied by the contents of the
location that is
(152-146)
locations backward from the current
address.

6-51

6.11 EDITING AND CONTROL COMMANDS
Errors made while typing at the console: keyboard are ea.sily corrected.
BASIC provides special commands to faci.litate the editing procedure.

6.11.1 Erasing Characters and Lines
(SHIFT/O" RUBOUTS, NO RUBOUTS,

J!~TMODE)

There are two methods available for eralsing a charactel:' or series of
characters one at a time. Typing a SHIFT/O causes the deletion of the
last character typed and echoes as a back arrow (+) on the LT33
(or
35) Teletype, or as an underscore
(-)
on most other console
terminals. One character is deleted ealch time the key is typed.
The RUBOUT key (or DELETE key on some t~erminals) may also be used
deletion of characters one at a time providing the command:

for

RUBOUTS
has been typed on the keyboard before the editing is done.
This
command enables the RUBOUT key to be used and must be typed each time
a new program is in memory.
If the use!r has neglected to type this
command, he may not use the RUBOUT key. A later command 'of:
NO RUl30UTS
disables the key for use.
For example:
10 LEE .. r A=10*B

The user types a B instead of T and immediately noticeEJ the mistake.
He may type SHIFT/O (or RUBOUT key, if enabled) once ·to delete the B,
(and as many times more as characters, including spacl~s ,
are to be
deleted).
After the correction is made, he may continue typing the
line. The typed line enters the comput~er only when thl~ RETURN key is
pressed.
Before that time. any number of correction:; can be made to
the line.

When the RETURN key is typed, the line is input as:

Notice that spaces, as well as printin9 characters, may be erased.
The user may era.se an entire line (provided the RETURN key has not
been typed) by typing the ALTMODE key (ESCAPE key on ,some keyboards).
BASIC echos back:

6-52

DELETED

at the end of the line to indicate that t:he line has been removed.
The user continues as though it were a new line. If ·the RETURN key
has already been typed, the user may still correct the line by simply
typing the line number and retyping the line correctly. He may delete
the line by typing the RETURN key immediately after the line number,
thus removing both the line number and line from his pro:Jram.
If the line number of a line not needing correction is accidentlally
typed, the SHIFT/O or RUBOUT key may be used to delete the number(s) ;
the user may than type in the correct numbers. Assume t:~e line:
10 IF A>5 GOTO 230

is correct.
types:

The programmer intends to insert a line 15,

but

instead

10 LET

He notices the mistake and makes the correction as follm.,s:
10

LET~~~~~5

LET X=Z-3

Line 10 ·remains unchanged, and line 15 is entered.
Following an attempt to run a program, error messages may be output on
the console terminal indicating illeqal characters or formats, or
other user errors in the program. Mos t ,arrors can be corrected by
typing the line number (s) and correc·tion (s) and then rerunning the
program. As many changes or corrections as desired may be made before
runs.

6.11.2 Listing a Program (LIST, LIST and LPT)
An indirect program or data can be listed on the active output
by typing the command:

device

LIST

followed by the RETURN key.
listed.

The entire

program

(or

data)

will

A part of a program may be listed by typing LIST followe~d by a line
number.
This causes that line and all following lines in the program
to be listed. For example:
LIST 100

will list line 100 and all remaining lines in the program.

6-53

The LIST command may be used in conjunction with the
follows:

1,PT

command

This will list the current program on the line printer.
Control
reset to the console terminal after the listing is completed.

LPT
LIST

6.11.3 Running a. Program (RUN, RUN and LPT)
After a BASIC program has been typed and. is in memory, i t is ready
be run.
This is accomplished by simply typing the command:

RUN
followed by the RETURN key.
The program will begin execution.
If
errors are encountered,
appropriate «~rror messages will be typed on
the keyboard; otherwise, the program will run to completion, printing
whatever output was requested.
When the END statement is reached,
BASIC stops execution and prints:
READY.

The line printer, if available, can be used in
RUN command, as follows:

conjunction

with

the

LPT
RUN
After this command is issued, all output: during program execution is
di verted from the console terminal to the line print'~r, eliminating
the need of inserting the LPT statement within the program.
The
output device is reset to the console tE~rminal after ex,~cution.

6.11.4 Stopping a Run (CTRL/C, CTRL/O, CTRL/SHIFT/P, BRE;AK)
To stop a program during execution or to return to the Keyboard
Moni tor at any time, type a CTRL/C (by pressing the CTRC, key and the C
key simultaneously). This causes the current operation to be aborted
immediately and the Cassette Keyboard Monitor to be :re-bootstrapped
from the System Cassette.
The cormnand CTRL/O (produced by typing the CTRL and
0
keys
simultaneously)
is used to stop teleprinter output temporarily.
The
program will con1:inue to execute but out.put will not be printed unless
an error occurs or unless BASIC is wai.ting for a comma.nd or for data
from an input sta.tement.
In the latter case, the console terminal is
the expected input device. This feat.ure is particularly useful for
programs that print lengthy introductions and then
request
a
user-specified parameter. Typing CTRL/O after the proqram is started
will cause BASIC to bypass printing the introduction and wait until

6-54

the parameter is specified, thereby savi.ng the time required to print
the message. A second CTRL/O will resume output.
NOTE
For most programs that do not wait for
input from the terminal, processing of
the program after an initi.al CTRL/O will
be completed before a second CTRL/O can
be typed. Thus, it is vel~ possible for
no output to be printed rather than the
anticipated partial output.
Certain terminals (such as Teletype models LT33 and 35)
are equipped
with a BREAK key which may be used in Cassette BASIC to interrupt
program execution. Pressing the BREAK kE!y causes a halt in execution
and a return to the BASIC Editor for mOrE! commands. For those systems
containing terminals not equipped with the BREAK feature, the same
result can be produced by pressing the CTRL, SHIrT, and P keys
simultaneously.

6.11.5 Loading a User-Coded Function
A user-coded function is created using the CAPS-8 EDITOR; it is
assembled using PALC. The resulting binary file is loaded with BASIC
using the Monitor Run or Load commands as follows:
.R BASIC, drive #::Eilename
or
.L BASIC, drive #::Eilename
Assume a user-coded function called UUF.BIN is stored on cassette
drive 3.
Assume also that the file UUF.BIN has been coded so as to
include the correct starting address for BASIC. The user runs BASIC
loading the function as follows:
.R. BASIC,UUF

The starting address for BASIC is included in the program and coded as
follows:
r~ I ELD

*31.100
$

The new function may now be used in any files the user \o.i'ishes to
and run.

6.11.6 Erasing a Program in Memory (SCRA'TCH)
The command:
SCRATCH

6-55

edit

or
SCR

is provided to allow the programmer to clear his storage area,
deleting any commands or a program which may have been previously
entered, and leaving a clean area in which to work.
If the storage
area is not cleared before entering a new program, lines from previous
programs may be executed along with tht:! new program, causing errors or
misinformation. The SCRATCH command eliminates all old statements and
numbers and should be used before any new programs are read into
memory or created at the keyboard.
Note that the SCR command does not clear the program name.
If the
user wishes to create a new program wi 1:h a new name, he should use the
NEW cormnand which also performs a SCRA~~CH.

6.11.7

Renaming a Program (NAME)

The user may change the name of the program in memory by
command:

issuing

the

NAME

BASIC responds by asking:
PROGHA~1

NEW

NAME-

The user specifies a new filename (and extension, if desired).
This
changes the name of the program without. affecting its image in memory.
All subsequent references to the progra.m must use this new name.

6.11.8

Saving

Program (SAVE)

Once the user has created or edited a program, he may ~lant to save the
new version on a cassette for later use. He does this by typing:
SAVE

BASIC asks:
U~IT

#(0-7):

to which the user responds with the number of the cassette drive on
which he wishes the program to be stored. The program is saved under
its current name--that is, the name used in BASIC's initial dialogue,
or its new name if the NAME command has been used to change it.
(If
the filename is the same as one already present on the cassette, the
old file is replaced by *EMPTY in the directory and the new file is

6-56

written onto the cassette.) After the program has been
still in memory and may be RUN or edited further.

saved,

Attempting to save a program on a full c::assette causes BASIC to return
to the editing phase; the user must save the program on another
cassette.
If the user does not specify a name for his program in the initial
dialogue (by responding with an AL~~ MODE to the NEW PROGRAM NAME
request), the program will be saved under the
assigned
name
NONAME.BAS.
If the user SCRATCHes a program, creates another program without
assigning a name to it by use of the NEW or NAME commands, and then
attempts to save it, it will be saved lmder the name of the last
program which was in memory, possibly deleting that program if saved
on the same drive.

6.12 CASSETTE BASIC ERROR MESSAGES
BASIC checks all commands before executing them.
If for some reason
it cannot execute a command, BASIC indicates this by typing one of the
following error messages and the number of the line in which the error
occured. The form is:
ERROR MESSAGE AT :LINE XXXX
Table 6-6 lists
execution.

the

errors

BASIC

chlecks

for

and

reports

before

Table 6-6 Cassette BASIC Error Messages
.Meaning

Message
ARGUMENT ERROR

A function has been
argument; for example:

CHAIN ERROR

A cassette error occurred while doing
program chaining; the user should not
attempt to run the program in memory
again.

DATA ERROR

There were no more items in the data list.

EOF ERROR

An attempt was made to read past the
end-of-file
during
run-t:ime
input.
Program execution terminates and control
returns to the Keyboard Monitor.

EXPRESSION ERROR

One of BASIC's internal lists overflowed
to
E~valuate
an
while
attempting
expression.

FILE NAME ERROR

A mistake or illegal character was found
in the user's specification of a cassette
drive # or file name in either a CHAIN or
an OPEN statement.

6-57

given an
SQR(-l)

illegal

Table 6-6

Cassette BASIC Error Messages (Cont'd)

Message

l-1eaning

FILE OPEN ERROR

The user attempted to open a run-time
output fi Ie when one was alre,:ldy open, or
a hardware error occurred.

FOR ERROR

FOR loops were nested too deeply.

FUNCTION ERROR

The user attempted to call
which had not been defined.

GOSUB ERROR

Subroutines were nested too

I 0 ERROR

The user attempted to do run··time input
and output to the same casBette at the
same time.

IN ERROR

A cassette error occurred whilE~ attempting

function

de~~ply.

to carry out an OLD command or while doing
run-time input.
LINE TOO LONG

A line of more than 80 characters was
entered; BASIC ignores the whole line and
waits for the user to enter a new line.

LINE # ERROR

A GOTO, GOSUB, or
nonexistent line.

LOOKUP ERROR

BA..SIC could not find a run-time input file
on the drive specified.

NEXT ERROR

FOR and NEXT statements were not
paired.

NO FILES ERROR

The user attempted to do run-time file I/O
wi thout first specifying so dUI'ing BASIC's
initial dialogue.

OUT ERROR

An error (probably end-of-tape) occurred
while doing cassette output either during
a SAVE or during run-time outpu.t.
If the
error occurred during a SAvE, the user
should retry the SAVE to a. different
cassette.
If the error occurred during
run-time output, he should re-run his
program using a different cassette for
output.

RETURN ERROR

A RETURN statem.~nt was issued
under control of a GOSUB.

SUBSCRIPT ERROR

A subscript has been used which is outside
the bounds defined in the DIM statement.

6-58

referenced

properly

when

not

Table 6-6

Cassette BASIC Error Messages (Cont'd)

Message

Heaning

SYNTAX ERROR

A command did not correspond to
the
language
syn1:ax.
Common examples of
syntax errors are misspelled commands,
unmatched
parentheses,
and
other
typographical errors.
Reference to an
undefined
UUF will also produce this
diagnostic.

TOO BIG, LINE IGNORED

The combination of program size and number
of variables exceeds the capacity of the
computer.
Reducing one or the other may
help.
Otherwise, the user must break his
program into
parts
and
chain
them
together.
A
large
number
of DATA
statements might be put into a run-time
input file.

The following programming errors are not reported by Cassette
BASIC, but instead are used in the computation as specified. They
are included here for the programmer's reference.
1.

Attempting to use a number in .::I. computation which is too
large for BASIC to handle will produce a result which is
meaningless.

Attempting to use a number in a computation which is too
small for BASIC to handle will result in the value zero
being used instead.

Attempt.ing to divide by zero will produce a result which
is mean.ingless.

6.13 CASSETTE BASIC SYMBOL TABLE
Table 6-7 lists the Cassette BASIC symbols and their values.
This information is useful when writing user-coded functions.

6-59

Table 6-7 Cassette BASIC Symbol Table

IPI)P-81f: CASSf:.TTE DASIC

PAI.8-V8

AHCLJEF

1763

CliJSF:

AHS
ACE.

b4d5

LLO:;EO 11 7 rt:

~~"25

l;MSwCH V'17b

AC~J

4417

C~t\MST

r~452

AC f,
ACl
AC?

~~24

CtJCLI'<

01.41

15 rA 2 ~71

CNt.R~

Vl5~1

V1 r~ 1 7
V"J01 b

CNTFNn 7 06~:'

(,. ~~ r L0

71.4rJi7

li~71

L~~ 1 LOZ

V1134

AC~
A[Hi h> ES

ALGr-LP tH.lhb
ALLOC
146~
314 ~,
ALL3
ALTMOO 2~ht
4~S4
ALl
AMATCH 6'50-'

12/27/72

DVI_OOP ';)245

h40~j

fALl

~61.4tl

CTklCK
CTt-:ZI1P
l..VILLlO

r;, t 1 ~

FA'rNAX

b2"' ~

\·'~"52
') VJ?' c'

fArNC

6.s:.s7

1 At K

th7~

f- A'r f\;CJ h34~
FATNCl 6304
FArNC2 b3~7
FATNC3 b31?

6731
E Cl"i ()
70C'3
EOIT
241(1
EI'.iIJ
2400
E~I)LIN 57102
E1\I)NM
733?
EH)NUM 3321
EI\I)POL S743
6404
F. f'.-r E R
EOFAO 4526
E(;F~TN 6650
E fJ'r R
0060
ERI~OR
4136
Ev ,~L
1000
E. \J '~L G0 10~14
EXI:'CUT 0213
EXIT
2'u~7

C/\(10

AhGERR

7;;~7

AR~L(1C

w~~: _~

LOI"iE u~

~~2~

AI-'l

44(7,2

LOS

"f:lh

L (l.~ T
'"' R 1 "J 1 )(

7143

Exp
bV'l0V'1
tXPGno ';)?42

4hkll?)

ASKAGI'I 11.5':1

~vH'~

E:.xPL("lN

5764

6 2v;~)
ATi"
ATf-.-,HIG 6265
AT~LOl·J 6220

L.~LF

h531

Ex flUK

~2b5

l..RLFU

13257

LF<'LF-I-I~

b? _",7

CTI-\LC

'1't

ATI\~,PT

P-A(JCHN

7 ~~ b 4

R~ f.\I-'Ol1.!

k:'!7..,1J

l..T!-iLCJ 7604
LT .... LZI f,6~t!

fx'rLOC 0?~4
FAI)
"vH:~ eI
FAOEXT 1314
FAD!
4 4 ~:H1

t~t" w0 S

l.4 '; ~~ 2

~TLINf:

Rf.l~~rX

b4':l1

.3 7 b r"

r'''l> LJ
hHful<

(;1 f:, r,1 ~,

~Sj(IP

27 y:,

6"2"

FEXPF

6067
6061
FEXPU
6064
FHER
511 7
FILALT 0367
FILNAM 0600
FILt\JR
1356
FILl
0606
FINDIT 0560
FINOLU 056b
fIOER
7135
fIx
4744
FIXEXI 4773
FIXITLJ 5200
f-IXLIN 2135
FIXLUP 4750
FIXUP 5143
FJMP
U1~0
14QlV1
FJMPI
F JUMP' 1130
FLU
3Vl~0
FLU!
3400
FLOGCl 6172
FLOGC2 6153
FLOGC3 615b
FLOGC4 6161
FMP
61tH~rll
fMPT
64V'1~
FMTENF 5121
I-MT1
'5123
FMT2
'le1S1
FMT3
5126
FN
'5453
FNE~R
5172

I)IA, I~

1301
CouELO V10V"4
CC'LUMN c;,13",
LOi'i CK ??77
l..()I"IMAS 617:;
LOI"1r-:UN 3377
(. (h"o/\(
1 123
COI\i!H
13b7

ANC1~M

PAGE 51

i} A

~'!vl~~

FATNCH 6342

UFlfxP (1043
u[CFRA ~:S43
ur:t~f:~ VJ 5 3~;

FEXPI

F's ...

7 \.3 \('?

KliFf;NO

h?0~

HlJF5T

b \~ V-' ~~

lin-

1~75

FATNC~

631'1

FNE)(IT

12~((1

rAi"I

1~~\

L·FLETE "'~~1
lJrVCOl"i 1354
~; I I.J I hi
3i!'21
Ult..dNl 't:?~
u.TLJIT
517b
L./ 1 bl. UP
~'~5 7

FATNCS

b~~(.1

F"ATNCb

63~3

FOR
FORCT
FOROON
FORERR
FORLIM
FORLIS
FORSTE
FORVAR
FOUNt)
FPAOO

0415
9J065
0663
0':)03
0721
5744
0'724

r: AP;';' E T 2~blJ
CASP\) hbl.:J
CAS [j U T 6 I;;';!'
CC/\;TR
~1~4 ~
CGtT
bb':ll

CHAlN

-f !,~.3 ,

CI1A"':Nt ,~1V' ~ 1
(I-" tol-.'r.',,- (()~4 ,
CrtCKIN 23'14

.J Tf'1

f..~7tJ.

L, I i'l F- L A

"Alii 34

LIVLP

4/05

01V~Tt

~3U1

h J ,/IV',

U 01 T ~4 U

t2a.,

3S~?

UrliJ[N

.3 ~'1 C .5
C ~-1 "JI·' S
.5 ~ 65
ChRr:ET o iJ 1 I
Cl'> hf< AI<. ,-<SIJ4
CKCTRL 4 1 Il~

UOI\( S \<J

PII.P.)
Vl b 5v:

r~" f- 11
C h~: hi f.i
C to r-: r;

U(l:'CRT

3Vl1.&2

UClfZER

t,57b

uPrL~(,

"~34?

U(.'i 1

'1~~2
r'- b? '.:l

r:LE:A~V

24b'-l

r! T x
'JOU nT r.

r:L~v

~1~l'~

li I-' I 1

1-,6"'7

CLOS

~l '(15f-·

-':'1.:'1 I C~

7 y~ I

FAlNC7 6326
FA"rNC~ 6331
FA'rNCg 6334
FATNS)( 62/2
FA'rNT
f-.21b
FA'r!'IlTT b301
FU:rGIT 3335
FDV
Fe) \11
Ft.~JTE:~

7 0~:H~

7400
4435
rt746

Ft ~n<
f- t:.)( I T
ei ~ 1I.1 ~)
F l:)( PC 1 6k172
Fl:.l(PC2 607')
rt )(f-lC3 b 1 ~j0

6-60

Fi:-. )(j-lC1.4

b 1 k.' 3

Ft \(PC~
Fr.l(I-'Cb

b 111

61~1,

F~Anl)R

FPOlv
fPOOIT
FPFLAG
FPGOTO
FPJMP
":-PJur1P
FPLAC
FPLOOP
fPMUL

~454
~57b

4456
'1"~ 014
4661

4237
?llS4
4273
4317
4214
4351
42(112
1.453V1

Table 6-7 Cassette BASIC Symbol Table (Cant 'd)

/POP-8/E CASSETTE BASIC

FPNOAD
FPOPEw
FPPGl
FPSKIP
FPSTO
FPSUB
FPT

PALB .. V8

427~

GETOPR

1~12

4305
4227
4314
4322

~fTuNI

~240

t.+4~3
42~v1

FPTE.MP

457~

FPT~

QJ0bl

FPZ01V ~n .$6
Ff.>INP 1243
FRINP1 12b1
FRr-.JDX
5tl04
FROUT 13(?\?

GETVAR el303
GE fl~ D ~177
bLum")
2711
GNt.XT V'lbel7
GObOTH 0534
('OLI5T 5764
t"n5UB

bOTSTE

~b34

'-'OUT

0(t1,;:)0

bfJff<

FSf.f:

v.J'0~

l1Rd

FSGT
F5INC1

1i'14~

(j~lJELA

7244
vH-j6d
7?23
7??1

';:) 7 1 ~~

GSdEND 'i777
LtSdPTi-i (il163
GSSl
1555
GSS2
lS~b
bToKlP 1722

rSINC~

,;:)124

F S PJC I

573?

~Tt:.MfJ

TJ ~1P 0442
GTJ",Pl 0~20
I.JTPTR
003b
rlAf
0~37
HALF
C1I451
HIGHwO 4333
HLOOP ?b77
2; 31
""LO~l
HLP
4163

FsTI

24ft1 0

""J...lr~

FTANT1
FTt-NT2
FU~,jT AB
FUPRCl
F v. f)

5677

F'Xxf>FX

GALT
r.UJMi?
fit T
GE:TAf)D

GtTbLK
r;r T CH

5" b?
v12C~
blll(l3

HNtJL~

JEt"<iol

2~V1?

GtTL.~t

?,t)jl

410~

I SIT 1 4422
I5L1T ~127
ISSDMl:. 1643
ISU,"1IN 1010
ITSDE~ 3513
ITS(')P
.$217
ITSl:.
32~3
ITSUP 1220
ITSP
3270
IUNIT 6660
JtlPtNT 37rt7
JISDIG 3344
JMATtH 277ft
JPUTCH Vl763
JUST0 3142
JuST0F 3152
Jl.JST0P 31:>')
3137
JUST1
JlJST2 3141
KbUIN 0421
KHI>INP 762b
t< ~ Uf E r~ b762
KbUt-ST b137

bbh3

1Ft
04~3
If;l\lOk'E ? 13 'f

Gf:.TLIN

ISITLI

h~00

v1 (-1 ~i 1

~573

ISI'TFU U es

"":163
lA~lLES 21?3
..L A1\lno
f.,76lJ
.l.AJ
1251
.I.C~5E:.P 5157
lrUUNl "'un2
11:.(TL.C 0235

Gr. T C!-ik iti" 12
Gt:.TCio(
0712
GtT1l 0f?7r:;
11~r:;
r,ETJ

ISlJIG

l.;I

7lJ4?
1557
1 4 ,>. ~I\
1 ., C:' l1
, ?(W

~551

10~aM

IOUN1T
IPNOPE
ISOI:'F2

727v)

F S It\JM4 5735
FSli\JOK 5h57
FSlf'-lZ ~ 7 Li)')
F S r r~ Z Z 5 "/1 ~
FSIN10 '=>b41
~, 1 5 V)
F5Lt:FSlf
01 1 V1
F S~jf..
f?\~) ~ 0
FSQ .... X 5407
2~0~
FST
':t" 02
11 j 1

ISITDF

ll\iSERT

l.?OTITl 7210
(1~? 1
G010
6010P~ 1202
l"OlSS
1~; 71

,;:)0~0.

FSINr.6 '::J"' (: 7

ISOIM
1 S I 'r

4007
7316
2027
2025
6434
4136
0227
1301
4024
3511
6532
1472
4564

IN~H(T5

5400

5716

~272

INPUT

It-..T
Ir-.wDTM

21tH

~7(il

INP'rN

72~7

'-'01 IT

FSB
FSHI
FSEO

FsI~C4

0434
4034
4076
0553

(;(llEt--1P C"V,55

f-!-<~TNE

FSI/l.IC3

II\;LOOP
INLLJPF
INPLUP
INPPTR
INPSET
I~PLJTN

~507

12/27/72

('1372

I(EPTR

(£;(1)77

Kf,Yv.U ~231
Klt;NOR 1b7b

lMMEL)

115~

1~1Mr:DA

KM2vl0

0(1)12

.P~

115S
343(11

KMLW04

l~JCHN

" 40.3

KI;HH1~

2170
2167

H~LJ

r. v

l"-liJF'tl
HiLH-:x2
J. [\ILClM

fJ,

131

(,)~,

117105
Kb201
LAStk'1-< 6612
LtH: t; I N 5622
LtRR
335~

~W15
4~17 7

6-61

PAGE 51-1
LET
0304
LETDO 0205
\..ETTER 3445
\..Fx\..UP 2331
\..HA\..f 30&7
LIMIT 1600
LINBUF 5551
\..INENO 0054
LINFIX 2326
3600
LIST
LISTAL 3610
LIST\..U 3612
L15T50 3611
L1ST2 3636
LIST3 3655
LIST4 3661
LISTS 3676
LITRAL 3123
LJMS
7255
LKER
1312
LKERR ~~30
LLSOUT 7400
LNOEND 3626
LC1ADtD 4123
LOCCTR 0045
LOCTEM 0671
LCCTMP 1671
LeG
6114
LCGACE 6165
LCGFwD 6164
LC'GOK W 6167
Ql3Ql6
LOOK
LOOKER 7310
LOOKUP 7002
L(iWLOC 2166
LFTOUT 7347
LLiKERR 0326
LLiNIT 0332
LLiP
34f.14
LUPF
'1430
L l~ LUP 3b64
M ~\ YZER 4612
MEIRE AK 7b05
M[NDLI 0e141
MENDPD 2361
M(iOL IS 0720
M(;SHEN 0527
M::NUS 1316
Ml.BEGI 0171
Ml.END vH 72
Ml.IN~U

0'140

Mr~ SON E 0736
MONITR 0100
MORElJI 647~
MOREIN 4[(1()j0

Table 6-7 Cassette BASIC Symbol Table

IPUP-81E:.

LA~;5I:TTE

f~ASIC

PAl.b-v8

12/27/72

MrJ ki fRO

1620

N(jTHE.R

0~13

I"1(lVt.

c!. (J ~-I 7

NOll(lfiU (}I3t'\5

01;1

NO T r"IOW

1776

010V,Vj

3271

01 1
01 :l0

21 7 1
3547
0506

,.,iClVLUP 212t:
MF~INT ~) v.l c::5
MPY

':i~?1

MpvLUP

Li')5?

MrJ A
r·1UL

1C,~1

hU r 5(;;('1

~437

NOlrxT ;>236
NOTVAk' 1 1 "'?
N(lTX1V1 ~23h
N(l r YI:: T h71J1
Nf-..,YMTA v1~53

o1 t~
o 1 t~2

It.J21
MSlbf-l 4~.s3
t"ll x'( 1 T 5173
MUlCLk' 4.,11
MUlfo:XfJ 3367

I\IIIL J M

1201/1

01 jr

ULx Tt. .33 .. 0

1\ U 1'1 f."\ l) F

5335

01llJ~

NlJl":Cr~K

C1172b

M lJ LX 1
33/1
MLiSTRE 4""'6

l'~lc.;HAN
r~

r t- ~!D

OL5

o 1 ,~

n 1 LH~ A

1 e2~'
1 , c; ~

~J A til

~n22

I\iAMCHK

0fo1~1

I\JIi,UlMS 3124
LHCO
4435
Vr,AS~Foi 257q

~aMf

1037

(.lee

o 1 t~0H

5205

23'::17

ft:i1261
2772
15b2
~35b

~-'62

2745
5144
3352

01 i' 7
[} 1 j' I ~

~027

02
02 ~,

~H1b4

oi' ~)[,,,

l{j153

02C'1J0A

3353
1151

"I A MI:: ~

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UCLJUNT

NA~1L OC

id216

uEt-.'P
UIP

"1 Ii 1
7~~ 1

021.~

335'?J
5344
0175

uJl.JMtJ

0215

~174

(J 2~)

Oc: "1 3

1366
3"17t1

I\iCTI-ILl b72S

~761

o c1~' 6 2

NF ~.!
10lJ7
I\;t it.JCHA 2h2?

ULv

127b
1057

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10~t?

lilliI'!: U;
ULtJMtS

;> (~~ 3

02£11{}

0~"1

11 11

02 i3

ULLH1P

[.Jl ~17

02~i5

OLIJ~

11171 VI
(.11147

02~)~B

5145
511J6
5153
b575

U"It:.lll M nH,l

O~6k1

0~12

u"'tSs

1~73

02 j'

UH.• v 1

3.312

3345
5147

LJ07b00

'i4~2

03v'"

1 01:'2

l\;E:.wLIN 2fo1(i'6

Nt: ~"r<1E. S 11 U"
~·~O';J
I\;I:XT
~H:. ~ T t R
N~~rG

~'b / 3
2757

1\;1:.)' T v A ~HI.3 7
N~Mt.S

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N~CiPEN

b3b5

Nt-i1

1~43

LJ "II:.

NQRLIMP 1J633

00/736 2324

~UCHNG

UPi.JONE

f'J(len!''''

OI-'l:.

3C)4V.l
6l -/6
t-.i(.IC'OMM v1 327
NOC~

4G'15h

Nn"II:;L~

3104

N[J~JZER

5~14

NnPARE 1032
NClPC~

2~20

1 31 4
f"OPE
N(1RLFT b423
NORMf-:lJ 522vl

I\IORMIT 52"-'7
NORUHO 5574
t-- ()SS1
1457
NO~S2
1452
NOT
3~26
NOTbAD 2153
Nort-'IG 4620
,..JUTCR 3~23
NOTEM 6~26
t-.iOTFUL 6712
1

02~i6A

o3l~

2771
1152
03i'37b 0776
0~i'55
1273
031' 7
~0/3
04
0156
2777
OiH'
a 4~!14
1153
04 ;:~
31Vj3
04f~0fc:l
3102
04c~13
1154
05tl(.10 5347
0046
06~~03
01
0074
o7 ~HlJ
1272
OHH1G1A 2565
07~H~0B 3473
07~n 7
1275
o 1 ~)20 5150
07~i45
4777

(JPtN
~575
(JPtN1
12C11~
UPt:.RAN 0075
OprljERk

~115

036
031'34

1203
0030

1354

uPUTAB 7016
UPS
IM'l26
uPuT(; 7147
UPl
Vl0?3
OPd
0022
(JP3
0021
(JTt.MP 1271
UTEMPI 7012
UTHER 3000
UUNIT 6760
OUPSET 1Vl26
OUll>EV (71133
OUrD2 ""132
UUTNUM 5f!.100
uUrOK
1332

6-62

(Cont I d)_

O/~i7eJ

b456

07~)77

4577

PAGE 51-2
07600
07603
07610
076i~0A

4.345
2774
5345
0754
2765
33Q!6
0140
2610
6544
3472
2775
3075
3346
3116
'1056
3743
4743
01f,0
3101
2325
0761
3 ~17 b
1274
3077
3351
5151
0057
5152
51'i4
5346
1561
3547
4742

U76408
07b73
077
07700
(J77'?J6A
U770bC
07715
07725A
077258
07737
07740
07741
07143
07745
07153
017b2
07763A
077b3H
07764A
07764A
07764C
07766
07770
07771
07772
07773
U7774
07"176
PACN
PAD
0~47
PADDON ~741
PAK8UF 0763
PAL1
0146
PANO~M 0144
PA~GER 0fc:l47
PARI
0145
PAsseR 0474
PBAR~O 2773
PBEGFI 1773
PCCUNT 0744
PCHKFI 0161
PCLOS 0143
PCOMMA 0273
PCQwT 0137
0036
PDL.
PDLIST 5703
PEDIT 0122
PENON 0271
PENDNM 0365
PERMS\' 5111
PERROR 0101

Table 6-7 Cassette BASIC Symbol Table (Cont'dl

IPPF-8/E: CAsSt:TTf

f~ A S

PALb-VA

PH~~w

~, I L.l1

PPl()(fO 1.162

PlhL.lc.1

"" .... VAL

vJ1 v., ~
(,11 ~i 5

PIo(c.~~T

l'JI:RROF< 1':) 7 1

?,315

Pt-).'p
F 1"1 f\d,) I
p ~ 1X

1£1612

PKt.St.:.T 1i113h
P!-! 1 t" i) L ~3ri12
t-IR i "ICn ?30b

v) 1 1 ~~

PI<'

P~NE[..lR

554b

pp 11\' H A 226~)

~F~.'L(JO

451~

P('E.TAf) ~H.,4
P (~E:. Tt3 L 011 7

PR 1 ~\jr)U
PR 1 ~J SE
PPJN'T

p l~ t, T C t..

t-iRINTC f?2C'J7

~r).I:CU

':,,776

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pr,ETLI ¥) 1 e 6
P (, tTL I"( 31'~ 2
Pl~t T n~
LOr.

I-' ~( 11\1 n~

~J L, f:' T V A l0 11 S
PC,iJL T S 81b2
p (, ell (' P ~, 1 11

F R 1 "11 2

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? 32v.l

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I-' ~~ LJ GN A

1114

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I-'P~,ut;f.(

37??

PLtTno

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Pr.( 'I EMP

VlV'(~2

PU: TTE. 310[,1
P L 1r·· 1 T c'~hb
P L I~, H U ~ 037
F L I ~,F I vl l I;) 7
~LlST
2') "111
PLrT~A
33':!u
') "I ·f ..,
P L lJ(.~

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r;W'i£?

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4L.1:5U
0121
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POLJ1NU
PF-ASSC
PPllLIS 0127
PPER~1S

21)72

PPFLOn 47,,1
P~FORl

17bl.;

Pf-'INT
PPop
PPRINl

b0b~

011b

PP~INU

vj! 25

01~)

PPUSH 0HJ6
PPUTCH ~~33

14~~

R1IOME 31VJ3
'::1573
RuN
2457
RUNC
i=456

RLJAO

~'S 1 Of.'

i-' 'r A t1 0 E

P(;P,3

~TBUF

~LJNIN

1171
p ~~ O~. BL 0124

POIP
41hh
POP
POPERA 3121

0433
6661
~MLE:FT 6413
f.(NI)
5353
Rf\OJMP 5350
f.(lBfN() 1~0~

PUNlUP 2472

P,....E~lI

(,:1 L1/J 4

RIGHT
RIP

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3770
, '~114

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131~

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P t-1tj I..: E A ;'J.3 o,(~
P ~,p Y
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0135

RfStT1 7072
RtSTOR .3771
RI:Tt\lE~ 0713
j.(tTU~N 0677

P ~ 1 f\1 T x 37~2
217L.1
Ph'l";LJM 374')

1.': 11 7 :~

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RtjS~'JCH

[..ltMPAC 3043

PR 1 r>1 T G 2 t~06
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t-iP If\IH'' 73?2

~'~LY

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~ELATt:.

?112

PI r. r,' (II-<

v-i722

RCtH~
6763
Io?E:AO
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Io<tAOIT 6664
Io(tADLO 12046
~t:ADV
6525

r r~r: X ??l.~

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i-'IJ~t:.RF

C;St.1'i

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PUTCOF

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PIJrCH

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PUfEk

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I-'l.' T J

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2550
2521
2544
1000
2401
SCtiMUR 1656
SCRATL 2445
SCR~T1

StARCH
SETINe
St:.TSGN
S('N
SIMPLV
SIN
SJUMP
S . . IPIT
SKPSVM
SLASH
SLOOP
SL.SHTM
SNUMFL
SPACER
SPLEFT
SGEXIT

P \·n·, F: RE 06L.17
P)(FORL CtJ55 .,
PXL.INb 3744
PXXCRL 3117
PXXFlJF ?571
P)(XExI 312v.'l
P)!XLIT 3122
j.I)(ATI1E 2567
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6-63

PAGE 51-3

1?/27/72

~332
lh~7

0200
4512
0726
3465
~624

0241
0471
2762

1332
2675
1337
el06b
1163
0142
5450

S(~LOOP
S(~R

S !;ERR
S :,F I X
S~) 0 Nt:.

s:n wo
s'r

5435
5412
11;)63
4/75

0336
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3~0~

S'r AR
1327
S'; AR 1 H 3vH?10
s'r I CKI 6L.130
S 'rOBUF 0747
S 'r (J P
2401
5" ORCH ~7ri1L.1
S "OVAR 0333
S\·JP
7~21
S)(E~

0~51

6441
TIUj
5547
TJ' BlH: S 6375
TI'd () 0 63'50
TJ'BFLG 2343
TI,BL
3652
Sl(ER~

Tn~rHP

2~h0

5000
TJ'N
TBE.GFI 5572
TEMP
0~e!3
TEMPS 31~2
TEN
0000
THESKI 1353
Tl.SOuT 7402
P1P
0V'J31
TOOlaN 5162
TPRINT 6$76
HIALUP 2131
TFIANSF 2126
HI VAG I 5131
H!VAL 0270
TFI VAL T 0271
THVOLO 3075
HIVSTE 0626
7024
T" V0
TrVOUT 1350
TUtHG 1173
T~I I DTH 2355
T~IOL F 3557
T~IO 5S 1074
0: TPAK 3~46
T"QUE5 1145
UDOPER 1363
UGH1
3561
0004
U..IMS
U~IOPER 1321
U~IOERF 4645
U~I I T
0012
UPARRO 6457

Table 6-7 Cassette BASIC Symbol Table (Cont'd)

/PDP"'8/t

RASIC

CA~S~TTE

P~~L8"'V8

12/27172

UPARRX

S140

xXGOSU 5321

)c)( TAN

UPAJ.<Rr?

~nbS

~)(L-iOTO

5300

X):TEXT ~540
)()( THEN 5305
)0: TO
51b5
X):TTVO 5437
)( ):ljNAR 5542

tlSERFN 1 to, 1 .,

XXGT

5147

liTEM

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6-64

PAGE 51-4

CHAPTER 7
USING CAPS-8 COOT

Using COOT, the programmer can run his binary program on the computer,
control its execution, and make alterations to his program by typing
at the Teletype keyboard.
COOT occupies any four pages of core, in the same field, that the user
desires. The user may change the location of these four pages of core
by reassembling the source.
If the user program resides in the first
few pages of memory, then COOT should be loaded in the upper pages of
memory, and vice versa. The user progrc~ cannot occupy (overlay)
any
location used by COOT, including the breakpoint locations (locations
4, 5, and 6 on page zero).

7.1

FEATURES

COOT features include location examina1:ion and modification: octal
core dumps to the Teletype using 1:he word search mechanism: and
instruction breakpoints to return control to COOT (breakpoints).
The
user's program can run with interrupts on. COOT may reside in any
field, not necessarily the same as the user's field.
The breakpoint is one of COOT's most uSE~ful features.
When debugging
a program, it is often desirable to allow the program to run normally
up to a predetermined point, at which the programmer may examine and
possibly modify the contents of the aecumulator (AC) , the link (L),
or various instruction or storage locations within his program,
depending on the results he finds.
To cicCOITlplish this, COOT acts as a
monitor to the user program.
The user decides how far he wishes the program to run and COOT inserts
an instruction in the user's program \~hich, when encountered, causes
control to transfer back to COOT.
COOT immediately preserves in
designated storage locations the con1:ents of the LINK and AC at the
break.
It then prints out the location at which the break occurred,
as well as the contents of the LINK and AC at that point. COOT will
then allow examination and modification of any location of the user's
program (or those locations containing the AC and L). The user may
also move the breakpoint and request that COOT continue running his
program.
This will cause COOT to reB tore the AC and L, execute the
trapped instruction and continue in the user's program until the
breakpoint is again encountered or the program is terminated normally.

7-1

7•2

USING COOT

When the programmer is ready to start de:bugging a new program
computer, he should have at the console:

the

A binary copy of the new program on a cassette.

A complete octal/symbolic program listing.

A binary copy of the COOT program (previously assembled so as
not to interfere with the user's program).

RUN P ROG, CODT
The binary of COOT must be the
automatically begins in CODT.

7.2.1

last

file

run.

Execution

Commands

SLASH(/)--OPEN PRECEDING LOCATION
The location examination character (/) causes the location addressed
by the octal number preceding the slash to be opened and its contents
printed in octal. The open location can then be modified by typing
the desired octal number and closing t:he location. Any octal number
from 1 to 4 digits in length is a legal input. Typing a fifth digit
is an error and will cause the entire m{~ification to be ignored and a
question mark to be printed by COOT.
Typing / with no preceding
argument causes the latest named location to be opened (again).
Typing 0/ is interpreted as / with no argument. For example:
400/6046
400/6046 2468?
400/6046 l2345?
/6046
The memory field referenced is that field specified by the location in
CODT symbolically referenced by F. For example, if the contents of F
were 20, then the command
423/
would examine location 423 in memory fiE!ld 2.

7-2

RETURN--CLOSE LOCATION
If the user has typed a valid octal nwru)er, after the content of a
location is printed by COOT, typing the RETURN key causes the binary
value of that number to replace the oriqinal contents of the opened
location and the location to be closed..
If nothing has been typed by
the user, the location is closed but the content of the location is
not changed. For example:
400/6046
400/6046 2345
/2345 6046
Typing another conunand
example:

location 400 is unchanged
location 400 is changed to contain 2345.
replace 6046 in location 400.
will

400/6046 401/6031 2346
400/6046 401/2346

also

opened

For

location ,100 is closed and unchanged and
401 is opened and changed to 2346.

LINE FEED--CLOSE LOCATION, OPEN NEXT LOCATION
The LINE FEED key has the same effect CiS the RETURN KEY, but, in
addition, the next sequential location is opened and its contents
printed. For example:
400/6046
0401/6031 1234
0402/5201

location 400 is closed unchanged and 401
is opened.. User types change, 401 is
closed containing 1234 and
402
is
opened.

SEMICOLON--CLOSE LOCATION, AND UNOBTRUSIVELY OPEN NEXT LOCATION
The SEMICOLON key has the same. effect as the LINEFEED key except that
the location and contents of the nf~xt sequential location are not
printed. Therefore,
400/6046 3211; 4162; 5000
has the same effect as
400/6046 3211
401/6031 4162
402/5201 5000
This makes it convenient for the user
locations.

ito

t (SHIFT/N) --CLOSE LOCATION, TAKE CONTENTS
OPEN SAME

change

several

MEMORY

sequential

REFERENCE

AND

The up arrow (circumflex) will close an open location just as will the
RETURN key.
Further, it will interprf~t the contents of the location
as a memory reference instruction, open the location referenced and
print its contents. For example:

7-3

404/3270t
0470/0212 0000

3270 symbolically is "DCA, this page,
relative location 70," so COOT opens
location .170.

(SHIFT/O) CLOSE LOCATION, OPEN INDIRECTLY

The Back arrow (or underscore) will close·the currently open location
and then interpret its contents as the address of the location whose
contents it is to print and open for modification.
For example:
365/5760t
0360/0426+
0426/5201

nnnnG--TRANSFER CONTROL TO USER AT LOCA~rION nnnn
Clear the AC then go to the location sp4~cified before the G (in the
field
specified by F).
All indicators and registers will be
initialized and the breakpoint, if any, will be insert~d.
Typing G
alone will cause a jump to location ~.

nnnnB--SET BREAKPOINT AT USER LOCATION nnnn
Instructs COOT to establish a breakpoin·t at the location specified
before the B (in the field specified by F).
If B is typed alone, COOT
removes any previously established breakpoint and restores
the
original contents of the break location. A breakpoint may be changed
to another location, whenever COOT is in control, by simply typing
nnnnB where nnnn is the new location. Only one breakpoint may be in
effect at one time; therefore, requesting a new breakpoint removes any
previously existing one.
A restriction in this regard is that a breakpoint may not be set on
any of the floating-point instructions which appear as arguments of a
JMS.
For example:
TAD
DCA
JMS
FAOO

Breakpoint legal here.
Breakpoint illegal here.

A breakpoint may not be set on a CIF instruction, nor on an
instruction which is meant to be ,executed between a CIF and its
corresponding JMP or JMS instruction.
A breakpoint may not be set on a memory
references an auto-index register.

reference

instruction

which

A breakpoint may not be set on a two-word EAE instruction, nor may
be set on any of the following instructions:

7-4

SKON
ION
IOF
The breakpoint (B) conunand does not make ,the actual excha.nge of COOT
instruction for user instruction, it only sets up the mechanism for
doing so. The act,ual exchange does not occur until a "g'o to" or a
"proceed from breakpoint" command is executed.
When, during execution, the user's program encounters the location
containing the breakpoint, control passes immediately to COOT (via
location 4, 5, and 6).
The C (AC)
and C (L) at t.he point of
interruption are saved in special locations accessible to COOT. The
user's data field is stored in location 0 and his instruction field is
stored in locati.on F as well as internally by COOT. The user
instruction that t:he breakpoint was replacing is restorec; before the
address of the trap and the content of the LINK and AC are printed.
The restored instruction has not been executed at this time. It will
not be executed until the "proceed from breakpoint" command is given.
Any user location, including those containing the stored AC and Link,
can now be modified in the usual manner. The breakpoint can also be
moved or removed at this time.
An example of breakpoint
ITERATE LOOP ••• ".

usage

follows

the

section

"CONTINUE

AND

A--OPEN C(AC)
When the breakpoint is encountered the C(AC) and C(L)
are saved for
later restoration.
Typing A after having encountered a breakpoint
opens for modification the location in which the AC was saved and
prints its contents. This location may now be modified in the normal
manner (see Slash) and the modification w'ill be restored to the AC
when the "proceed from breakpoint" conunand is given.
Similarly, other key locations in COOT ma.y be examined and modified as
follows:

L--OPEN CONTENTS OF LOCATION L (LINK)

F--OPEN CONTENTS OF LOCATION F

D--OPEN CONTENTS OF LOCATION 0 (USER' S Dl~TA FIELD)

7-5

NOTE
Whenever any of the locations A, L, F,
0, M are referenced, COlDT automatically
sets the value of F to be the field of
COOT.

C--PROCEED (CONTINUE) FROM A BREAKPOINT
Typing C, after having encountered a brc:!akpoint, causes COOT to insert
the latest specified breakpoint (if an~r>; restore the contents of the
AC and Link; execute the ins tructi()n trapped by the
previous
breakpoint;
and transfer control back to the user program at the
appropriate location. The user program then runs until the breakpoint
is again encountered.
Regardless of the value of P, the C co~nand resumes program execution
at the precise spot where it had been previously stopped. The user's
data field is first set to that specified by location o.
NOTE
If a trap set by COOT is not encountered
while
COOT
is
running the object
(user's) program, the instruction which
causes the break to occur will not be
removed from the user's program.

nnnnC--CONTINUE AND ITERATE LOOP nnnn TIMES BEFORE BREAK
The programmer may wish to establish thE! breakpoint at some location
within a loop of his program.
Since loops often run to many
iterations, some means must be available to prevent a break from
occurring each time the break locati()n is encountered. This is the
function of nnnnC (where nnnn is an ()ctal number).
After having
encountered the breakpoint for the first time, this command specifies
how many additional times the loop is t() be iterated before another
break
is to occur.
The break opE!rations have been described
previously in the section on the B command.
Gi ven the following program, which inCrE!aSeS the value of the AC by
increments of 1, the use of the breakpoint command may be illustrated.

7-6

*200
0200 7300
CLA CLL
0201 1206 A" TAD ONE
0202 2207 B,. ISZ CNT
0203 5202
JMP B
0204 5201
JMP A
0205 7402
HLT
0206 0001 ONE,l
0207 0000 CNT ,0
0201
A
B
0202
CNT
0207
ONE
0206
020lB
200G
0201 (0;0000
C
0201 (0;0001
C
0201 (0;0002
4C
0201 (0;0007
COOT has been loaded and started.
A breakpoint is inserted at
location 0201 and execution stops here showing the AC in:,-tially set to
0000 and the link O. The use of the Proceed command (C) executes the
program until the breakpoint is again en.countered (afte:::- one complete
loop) and shows the AC to contain a value of 0001.
Aga.in execution
continues, incrementing the AC to 0002. At this point, 1:he command 4C
is used, allowing execution of the loop to continue 4 more times
{following the initial encounter} before stopping at the breakpoint.
The contents of the AC have now been incremented to 0007,.

M--OPEN SEARCH MASK
Typing M causes COOT to open for modification the location containing
the current value of the search mask and print its contents.
Initially the mask is set to 7777.
It may be changed by opening the
mask location and typing the desired value after the value printed by
COOT then closing the location.

LINE FEED--OPEN LOWER SEARCH LIMIT
The word immediately following the mask :;torage location contains the
location at which the search is to begin. Typing the LINE FEED will
open for modification the first location after the mask, and its contents will be printed.
Initially, the lower search limit is set to
0001. It may be changed by typing the desired lower limit after that
printed by CODT, then closing the location.

7-7

LINE FEED--OPEN UPPER SEARCH LIMIT
The next sequential word contains the l()cation with which the search
is to terminate. Typing the LINE FEED key to close the lower search
limit causes the upper search limit to be opened for modification and
its contents printed.
Initially, the upper search limit is the
beginning of COOT itself, 7000 (1000 for low version). It may also be
changed by typing the desired upper search limit after the one printed
by CODT, then closing the location with the RETURN key.

nnnnW--WORD SEARCH
The command nnnnW (where nnnn is an octCll number) will cause COOT to
conduct a search of a defined section ()f core, using the mask and the
lower and upper limits which the user has specified, as indicated
above.
The searching operations arE! used to determine if a given
quantity is present in any of the locations of a particular section of
memory.
The search is conducted as follows: CODT masks the expression nnnn
which the user types preceding the Wand saves the·result as the
quantity for which it is searching. CODT then masks each location
within the user's specified limits with C(M) and compares the result
to the quantity for which it is searching. If the two quantities are
identical, the address and the actual unmasked contents of the
matching location are printed and the search continues until the upper
limit is reached. The search occurs in the memory field specified by
F.
A search never alters the contents of any location.
For example:
Search location 3000 to 4000 for all ISZ instructions regardless of
what location they refer to (i.e. search for all locations beginning
with an octal 2).
FOOlO
M7777

20
7000

7453/0001

3000

7454/7000

4000

2000W
0200/2467
3057/2501
3124/2032

7. 3

Set the field to 2
Change thE~ mask to 7000, open lower
search limit.
Change thE~ lower limit to 3000, open
upper limit.
Change thE! upper limit to 4000, close
location.
ISZ
the
search
for
Initiate
instructi()ns.
These are 4 ISZ instructions in
this section of core.

ILLEGAL CHARACTERS

Any character that is neither a valid c()ntrol character nor an octal
digit, or is the fifth octal digit in a sequence, causes the current
line to be ignored and a question mark printed. For example:

7-8

7.4

7.4.1

4:?
4U?

COOT opens no location.

0406/4671 67K
/4671

COOT ignores modification cmd closes
location 406.

ADDITIONAL TECHNIQUES

TTY I/O-FLAG

COOT automatically notes the status of the TTY flag after encountering
a breakpoint and restores it after performing a CONTINUE.o

7.4.2

Interrupt Program Debugging

COOT executes an IOF when a breakpoint is encountered.
(It does not
do this when more iterations remain in an nnnnC command.) This is done
so that an interrupt will not occur when COOT prints the breakpoint
information.
COOT thus protects itself against spurious interrupts
and may be used safely in debugging programs that turn on the
interrupt mode.
COOT restores the int:errupt facility to its former
state when it resumes execution.
'

7.4.3

Octal Dump

By setting the search mask to zero and typing W, all locations
(in
field F) between the search limits will be printed on thl~ Teletype.

7.4.4

Indirect References

When an indirect memory reference instruction is enc=>untered, the
actual address may be opened by typing t and + (SHIFT/N and SHIFT/O,
respectively).

7.5

ERRORS

The only legal inputs are control charac1:ers and octal digits.
Any
other character will cause the charactE~r or line to be ignored and a
question mark to be printed by COOT. Typing G alone is an error.
It
must be preceded by an address to which control will be transferred
This will elicit no question mark also if not preceded by an address,
but will cause control be transferred to location O.

7-9

7.6
7.6.1

OPERATION ANO STORAGE
Storage Requirements - CAPS-8 System

COOT can be run in a standard CAPS-8 system and requires 1000
(octal)
core locations and three locations (4,5,6) on page zero of every field
which uses a breakpoint. COOT is page-relocatable.
The source tape can be re-origined to the start of any memory page
except page zero and assembled to reside in the four pages following
that location, assuming they are all in the same memory bank.

7.6.2

Programming Notes Summary

COOT must begin at the start of a memory page (other than
and must be completely contained in one memory field.
The user's program must not use or reference
occupied or used by COOT and vice versa.

any

page

core

zero)

locations

Breakpoints are fully invisible to "open location" cOJ'TUllands; however,
breakpoints may not be placed in locations which the user program will
modify in the course of execution or th€~ breakpoint will be destroyed.
If a trap set by COOT is not encountered by the
breakpoint instruction will not be removed.

user's

The user may type CTRL/C at any time to return to the
(assuming his program did not destroy CAPS-8).

7-10

program,
CAPS-8

the

Monitor

7.7

COMMAND SUMMARY

nnnn/

Open location designated by the octal
nnnn.

Reopen latest opened location.

RETURN key

Close previously opened location.

LINE FEED key

Close location and open the
one for modification.

t(SHIFT/N)
+-

(SHIFT /0)

number

sequential

Close
location.
and
allO\~
modification of the next location.

immediate

Close location, take
contents
of
that
location as a mE!mory reference ilnd open it.
Close location, open indirectly.

Illegal character

Current line typed by user is
types: ? (CR/LF) •

nnnnG

Transfer program control to location nnnn.

nnnnB

Establish a breakpoint at location nnnn.

Remove the breakpoint.

Open for modifiGation the location in which
the contents of the AC were stored when the
breakpoint was encountered.

Open the location storing the link.

Proceed from a breakpoint.

nnnnC

Continue from a breakpoint and iterate past
the breakpoint llnnn times before interrupting
the user's
p:rogram
at
the
breakpoint
location.

Open the search mask.

ignored,

COOT

LINE FEED key

Open lower search limit.

LINE FEED key

Open upper search limit.

nnnnW

Search the portion of core as d.efined by the
upper and low-er limits for t.he octal value
nnnn.

Open location F.

Open location D.

7-11

CHAPTER 8
CAPS-8 UTILITY PROGRAM

8.1

INTRODUCTION

The CAPS-8 Utility Program (UTIL) allows: the user to take files stored
on paper tape and transfer them to cassette, using either the
high-speed or low-speed reader. The Ut:ility Program will transfer
both ASCII and BINARY files.

8.2

CALLING AND USING THE UTILITY PROGF~

To call the utility Program from the sys:tem cassette, the user types:
.R UTIL/OPTIONS
in response to the dot (.) printed by the Keyboard Moni 1:or.

8.2.1

Utility Program Options

There are two options available for use: with the Utility Program~
these options are discussed in Table 8-1.
(Options usaqe is explained
in Chapter 2, Sec::tion 2.4.3.)

Table 8-1
Utility Program Options
Meaning

Option

The /H option. is used to designate the
high-speed rea.der as the input: device. Note
that the high-speed reader in the default
input device.
That is, if no option is
specified the program aSSUmE!S
that
the
high-speed reader is the input device.

The /L option is used to designate
low-speed reader as the input device.

8-1

the

8.2.2

Input and Output Specifications

Before indicating the input and output devices to be used in the file
transfer, the user must ensure that the proper reader is ready and
that the cassette the file is to be copied onto is write-enabled.
When this has been done, the user is ready to begin the file transfer.
After UTIL has been called from
following:

the

system

cassette,

asks

the

MODEThe user responds with a single character (A or B) to indicate whether
the file being put on the cassette is ASCII or BINARY.
OUTThe user responds by typing the drive number the output cassette is
mounted on and the name of the output file to be put onto it, i.e.,
3 :FOO. In B mode, • BIN is the default e~:tension.
After these two queries have been answere!d UTIL prints the following:
t

The user responds by typing any character; this response starts the
file transfer.
(If /L had been typed, the user merely turns on the
low-speed reader.)

8.3

UTILITY PROGRAM ERROR MESSAGES

Errors which occur during the utility Program operation may be of two
types: User errors and cassette errors. User errors may be corrected
with the appropriate action as detailed in Table 8-2. Cassette errors
normally require the user to use another cassette to complete the copy
operation. Control does not return to the Keyboard Monitor when a
Utility Program error occurs. The USE!r may use CTRL/C to return to
the Monitor if he cannot correct the indicated error.

Table 8-2
Utility Program Error Messages
Jl.!eaning

Message
UNIT n NOT READY

There is either no cassette on the cassette
drive specified or no such drive exists.

OUTPUT ERROR ON UNIT n

An output error has occurred on the

cassette
drive specified.
The user should try the
transfer operation using another cassette.
Or perhaps, the user tried to write data when
the write prote1ct tab of the cassette on the
drive specified was write-locked.

8-2

ENTER ERROR ON UNIT n

An error occurrl:!d whi Ie trying to open a

new

cassette file.
UNIT n FULL

There was not enough room on the cassette.

CLOSE ERROR ON UNIT n

An error occurred during a close operation.

INPUT ERROR

In binary mode, the paper tape reader stopped
or ran out o:E tape before a checksum was
encountered.

CHECKSUM ERROR

In binary mode, the checksum did not agree;
probably a hard~"are read error. Try again.

Whenever an error occurs, the program writes a
open cassette if possible.

8-3

new

sentinel

the

CHAPTER 9
BOOT

BOOT is used to make it convenient to bootstrap from one system to
another, or from. one device to another by typing commands on the
keyboard.
BOOT can run conveniently from CAPS-8 and other monitor systems,
i.e., OS/8 and COS-300.
9.1

OPERATING PROCEDURES

To run BOOT from CAPS-8 the user types:
.R BOOT
the system will respond by typing a slash, at which time the user
responds with the device mnemonic.
If an illegal mnemonic is typed, the system types "NO" and prints a
slash to allow the user to try again.

In this case, the user can

type RUBOUT to erase a line and try again.
If a legal mnemonic was given, but the system configuration does not
include the corresponding device (or

thE~

device is not ready), the

bootstrap may hang.
The following is a list of legal mnemonics:
Mnemonic

Device

!3~stem

or Comments

TA8E cassette

CAPS-8

Any disk (RF08,
DF32, RK8E, RK8)

OS/8, COS-300

LINCtape

DIAL-V2, DIAL-MS

RF08 or DF32

Disk Monitor

Any tape (TC08,
T08E, LINCtape)

OS/8, COS-300

LINCtape

OS/8, COS-300

PT8E Papertape

Loads BINLDR into field 0

9-1

Mnemonic

Device

§:ystem or Comments

RK8E disk

OS/8, COS-300

RF08, DF32 disks

OS/8, COS-300

RK8 disk

OS/8, COS-300

TD8E DECtape

OS/8, COS-300

TC08 DECtape unit 4

Typeset Bootstrap
types BOOT's version number

TC08 DECtape

OS/8, COS-300, Disk monitor,
DEC library system, and others
Zeroes core (field 0)

If the device mnemonic is followed by a period, the program will load
the correct bootstrap into core and then halt.

Hitting continue

branches to the bootstrap.
Example:
.R BOOT

LDT
The preceding bootstraps onto a DECtape system (on DECtape unit ~).
The underlined characters were typed by the computer.

9-2

APPENDIX A.
ASCII CHARACTER SET

Character
A
B
C
D
E
F
G
H
I
J

K
L
M

N
0

P
Q

R
S
T
U
V
W

Z
0
1
2
3
4
5
6
7
B
9

B-Bit
Octal

7-Bit
Octal

301
302
303
304
305
306
307
310
311
312
313
314
315
316
317
320
321
322
323
324
325
326
327
330
331
332
260
261
262
263
264
265
266
267
270
271

101
102
103
104
105
106
107
110
III
112
113
114
115
116
117
120
121
122
123
124
125
126
127
130
131
132
260
261
262
263
264
265
266
267
270
271

Character
!

$
%
&

(

)

<
=
>
?
@

[

\
]
t
+

Le alde r /Tr ai Ie r
BELL
TAB
LINE FEED
FORM
CARRIAGE RETURN
CTRL/Z
SPACE
RUB OUT
BLANK

A-I

B··Bit
Octal

7-Bit
Octal

241
242
243
244
245
246
247
250
251
252
253
254
255
256
257
272
273
274
275
276
277
300
333
334
335
336
337
200
207
211
212
214
215
232
240
377
000

241
242
243
244
245
246
247
250
251
252
253
254
255
256
257
272
273
274
275
276
277
133
134
135
136
137

240

APPENDIX B
ERROR MESSAGE N~D COMMAND SUMMARIES

The following summaries are provided for the user's convenience: they
are grouped in alphabetical order according to the Sys;tem Program to
which they pertain. As these are only summaries the USE!r is referred
to the appropriate chapters for details.

KEYBOARD MONITOR (Chapter 2)
Error Messages
Meaning

Message
BAD COMMAND

The user has failed to follow the
correct syntax for Monitor commands.

FILE NOT FOUND

The Monitor could not locate the file
(or files) specified.

IO ERROR ON UNIT n

An I/O error has occurred on the
cassette unit drive spec!ified. The
user should try the I/O transfer
specifying another cassett:e.

UN IT n NOT READY

There is no cassette on the unit
drive specified, or no such drive
exists.

UNIT n WRITE I..oCKED

The user t,ried to write data when the
wri te prc1tect tab of the cassette on
the drive specified was wJ:ite-Iocked.

Conunands
Explanation

Conunand
DATE

Allows thE~ user to enter the month,
day, and year.
This date is then
represented in directory listings.

DELETE

Causes thE! file named in t.he command
line to be deleted from the cassette
drive specified.