Radio Shack TRS-80 User manual

TRSDOS &
DISK BASIC
Reference
Manual
Radio /hack
MICRO
COMPUTER
Contents
1. General Information
2. Mini Disk Operation
3. TRSDOS Overview
4. TRSDOS Commands
5. Extended Utilities
6. TRSDOS Technical Information
7. DISK BASIC
8. Appendices
Index
CUSTOM MANUFACTURED IN THE USA FOR RADIO SHACK MADIVISION OF TANDY CORPORATION

TRSDOS &
DISK BASIC
Reference
Manual
For the Radio Shack TRS-80
Disk Operating System
TRSDOS Version 2.1
DISK BASIC Version 1.1
Radio /haek
Ma DIVISION OF TANDY corporation
One Tandy Center
Fort Worth, Texas 76102

First Edition -1979 Software Copyright Notice
All rights reserved. Reproduction or use, without express
permission, of editorial or pictorial content, in any man-
ner, is prohibited. No patent liability is assumed with
respect to the use of the information contained herein.
While every precaution has been taken in the preparation
of this book, the publisher assumes no responsibility for
errors or omissions. Neither is any liability assumed for
damages resulting from the use of the information con-
tained herein.
©Copyright 1979, Radio Shack
ADivision of Tandy Corporation,
Fort Worth, Texas 76102, U.S.A.
All TRSDOS and DISK BASIC software is copyrighted by
Radio Shack. Radio Shack grants each TRSDOS user the
privilege of making BACKUP diskettes of TRSDOS and
DISK BASIC, provided such diskettes are solely for per-
sonal use.
Any other duplication of TRSDOS or DISK BASIC soft-
ware, in whole or in part, in print or in any other storage-
and-retrieval system, is forbidden.
Printed in the United States of America

To Our Customers
This is areference manual, and its organization reflects the relationship between
TRSDOS and DISK BASIC. TRSDOS is the fundamental software, so it's described
first. DISK BASIC is alanguage supported by TRSDOS, so it's described after
TRSDOS. (If other languages are supported later, they'll plug right in to this manual
along with DISK BASIC.)
But don't think you have to read the manual in strict sequence. If you're an old hand at
LEVEL II BASIC and you want to start out with DISK BASIC, go ahead and skip to
Section 7. You can refer back to the TRSDOS sections later on when you're ready or
when you need them.
We hope you enjoy exploring this powerful new computer system!
Htouj fo Use This Book
R«ad
Sections IiZ[make a TRSDOS Backup
YES
£>kim Read and use.
Sect/on 7
Read and use.
Sections 3-2
Yes

General
Information
Radio Jhaek
TRS-BO
MICRO
COMPUTER
SYSTEM
vJ
Contents of This Section
Introduction
Notation Conventions .
Versions and Releases
....2
....3
....6
Section 1-Page 1

General Information
Introduction
This book is acombined operation and reference manual for the
TRS-80 Disk Operating System. It will tell you how to operate the
hardware and how to use the software.
For many of you, there will be more than enough information. ("All
Iwant to do is use the Computer, not understand it!") Don't worry,
this book is designed so that you can start programming in DISK
BASIC (if that's what you want to do) right away. All you have to do
is read the chapter on Mini Disk Operation . . .skim through TRSDOS
Overview and TRSDOS Commands ... and on to DISK BASIC.
But DISK BASIC is just one aspect of TRSDOS. It's not a
part of TRSDOS, but aprogram that TRSDOS executes. Using
DISK BASIC without any awareness of the capabilities of TRSDOS
is rather like riding in aPullman car without any knowledge of the
engine, freight cars, diner and other parts of atrain. It's true that
TRSDOS will do all that's necessary to let you ride comfortably along
in BASIC; but eventually you're going to want to have asay in where
the train goes, what its schedule is, and what goes in all those freight
cars. That's when you need to understand TRSDOS.
The illustration below shows the relationship between the Computer,
Expansion Interface and Mini Disk Drives.
The first drive(Drive 0) always contains the TRSDOS
diskette, which is pre-recorded with the Operating System
software: an executive program, and several auxiliary
programs, including DISK BASIC. The executive program
is loaded into the first 4K bytes of RAM, and stays there
while TRSDOS is in control. The auxiliary programs
are loaded as needed.
Second, third and fourth drives can contain
diskettes, for storing your programs and data.
The Expansion Interface contains the real-
time clock, disk controller IC, and optional
extra RAM (addresses above 32767).
The Keyboard/Computer contains abuilt-in (ROM)
program which takes over at power-up, and loads
the TRSDOS executive program from the system
diskette (in Drive 0). If the Mini Disk equipment is
not connected, this ROM program can transfer control
to LEVEL II BASIC.
1-2

General Information
One section of this book you should definitely become familiar with
is the Glossary. We've tried to give definitions for all the "computer
words" and everyday words with special meanings in this book. Even
if you've heard all the terms, you'll gain some useful information
from the Glossary, because it's customized for the TRS-80.
First you make aBACKUP ...
You received one TRSDOS diskette with your Mini Disk drive 26-1 160.
This diskette contains the operating system software. Without this
disk, you haven't got adisk operating system.
So, your first disk operation ...before you remove the write protect
tape from the TRSDOS diskette ...should be to duplicate TRSDOS
onto ablank diskette. You'll find abbreviated instructions for making
aduplicate (BACKUP) of your TRSDOS diskette at the end of the
Mini Disk Operation chapter.
Notation Conventions
In descriptions of syntax for commands, statements and dialog with
the Computer, we'll use the following conventions for clarity and
brevity.
p
1This special symbol represents amandatory
blank space. Unless it is specified, any
blanks that appear in the syntax are optional.
Example:
DIR#:1
The blank space is required after the R.
<space >
"Press the HJhH;l key."
"Press the space-bar."
CAPITALS and
punctuation
Indicate material which must be entered
exactly as it appears. The only punctuation
symbols not entered are the special cases
(brackets and triple-period ...) explained
below.
Example:
LOAD"filespec"
Only the command LOAD and the quote
marks are entered verbatim; you supply
the filespec.
1-3

General Information
Notation, continued
SCREENED CAPITALS Represent input you supply, upon prompt-
ing from the Computer. This convention
will only be used where necessary to
distinguish between Computer prompting
and user input.
Example:
HOW MflNV FILES? 5l=MHd;l
The Computer asks the question, and you
answer it.
lowercase italics Represent words, letters or values you
supply from aset of acceptable values for
that situation.
Example:
var =exp
Avariable name goes on the left, and an
expression goes on the right.
[ ] Brackets enclose optional material.
Example:
CLOSE[filenum ]
filenum (the file number) is optional after
CLOSE. The brackets are not actually
typed in.
The triple-period symbol inside brackets
indicates that preceding items in the
brackets may be repeated.
Example:
INPUT ["prompting message";] var[,var ...]
The INPUT variable-list may include
more than one variable. The periods are
not actually typed in.
var([, ....]) Signifies an array. If no commas are
placed inside the parentheses, a
one-dimensional array is intended;
1comma indicates atwo-dimensional
string array; etc.
Examples:
A$( ,)indicates atwo-dimensional
string array.
Bl( )indicates asingle-dimensioned
array.
1-4

General Information
Notation, continued
exp
var
nmexp
nmvar
exp$
var$
con
nmcon
con$
numerical
suffixes
String or numerical expression
String or numerical variable name
Numerical expression, including constants,
variables, functions
Numerical variable name
String expression, including constants in
quotes, variables, functions and operators
String variable name
Constant, either string or numerical
Numerical constant
String constant
Attached to distinguish between different
arguments and parameters of the same type.
Example:
COFYtyfilespecl fIO\j>filespec2
1-5

General Information
Versions and Releases
Some of you may be alittle confused about the terminology,
"Version X.Y". The "X" and "Y" will change as TRSDOS is
updated, so here's an explanation.
Anew version represents asubstantial expansion of the previous
version. For example, new utilities, high-level languages, etc., might
be included in anew version. Such versions are numbered by the
integers 1, 2, 3, —
Anew release, on the other hand, is simply an update of the previous
release of agiven version. This later release generally includes wider
implementations and enhancements of commands and fixes for any
problems in the earlier release. The releases are numbered by
decimal fractions, .1, .2, .3, ... .
Therefore, when we refer to Version 2.1, that's short for the first
Release of Version 2.
Note: In its original printing, this Manual describes TRSDOS
Version 2. 1,and DISK BASIC Version 1.1. The Manual will be
updated as required by later versions and releases.
1-6

Mini Disk
Operation
Radio Shack
TRS-SO
MICRO
COMPUTER
SYSTEM
H
A
R
D
W
A
R
E
Contents of This Section
Introduction 2
Connection 3
Operation 5
Care of Diskettes 8
Specifications 10
Schematics 11
Making aTRSDOS BACKUP 16
Note: Abbreviated instructions for making aBACKUP (duplicate) of your TRSDOS
software diskette are included at the end of this section. Your very first disk operation
should be to make such a"safe copy", following the abbreviated instructions.
Section 2-Page 1

Mini Disk Operation
Introduction
The TRS-80 Mini Disk drive is amass storage device custom
manufactured for use with the TRS-80 Microcomputer. It combines
the compactness of acassette recorder with the high-speed, reliable
data access of the larger disk drive units. Information is magnetically
recorded on and read from flexible ("floppy") diskettes.
In simplified terms, the Mini Disk consists of amagnetic read/write
head, similar to that on atape recorder; astepper motor to move the
head across the diskette surface; adrive motor and hub assembly to
rotate the diskette; and the necessary logic circuitry to control
the read/write process and the motor speed. See Figures 1and 2.
There are two types of drives,
distinguished by their Radio
Shack Catalog Numbers,
26-1 160 and 26-1 161. Your
disk system must include one
(and only one) 26-1 160 and
may include up to three
26-1 161 drives.
Included with 26-1160
Drive unit: Incorporates
special terminating resistors
not present in the 26-1 161
units.
Interconnect cable: For con-
nection of 26-1 160 and up to
three optional 26-1 161 drives
to the Expansion Interface.
1TRSDOS diskette: Contains
the operating system software,
utilities, DISK BASIC, etc.
Included with each 26-1 161
Drive unit: Does not incorpo-
rate terminating resistors.
Blank diskette: Can be
formatted or backed up for
use with TRSDOS.
\i
Figure 1. Mini Disk Drive.
MAGNETIC READ/WRITE HEAD
DISKCONTROLLE
Figure 2. Functional components in aMini Disk drive.
2-2

Mini Disk Operation
Connections
The power to all components in the TRS-80 system should be "off
while you make connections.
Look at the ribbon-type connector cable included with your 26-1 160
Mini Disk drive. Notice that the cable has four edge card connectors
through its length, and asingle connector at the other end. Connect
the single plug to the edge-card jack on the left rear of the
Expansion Interface, as shown in Figure 3. Be sure the plug is
oriented so the cable exits from the bottom.
Before connecting the Drive(s) to the cable, note the following rules:
1) 26-1 160 must always be the "terminal" or final drive on the
cable; that is, of all your drives, it must always be the farthest
away from the Expansion Interface. This is because it includes
the terminating resistors mentioned above.
2) The connector closest to the Expansion Interface must always
be plugged in to adrive. The other connectors can be
"empty".
-LEFT REAR OF EXPANSION INTERFACE
(MINI-DISK CONNECTION)
CABLE MUST EXIT AT BOTTOM
FOR PROPER CONNECTION
RIBBON TYPE CONNECTOR CABLE
Figure 3. Connecting the ribbon cable to the Expansion Interface.
2-3

Mini Disk Operation
Connect each Mini Disk
unit to the cable, taking
care to orient the plug
properly as shown in
Figure 4. Inside each
plug is asmall plastic
connector. If the plug
doesn't mate properly,
check to see that the
plug is oriented so the
pin lines up with the
slot.
EDGE CARD PLUGS GUIDE SLOT"
Figure 4. Connecting the cable to the Mini Disk.
Examples:
If you have just one drive (must be 26-1 160), then connect it to the
first connector plug, so as not to leave any empty connectors between
the Drive and the Expansion Interface. Leave the last three connectors
empty.
If you have two drives, then connect 26-1 161 to the first connector
and 26-1 160 to the second connector. Leave the last two connectors
empty.
Figure 5shows aMini Disk system with four drives connected.
Connect each Mini Disk to asource of 120 VAC, using the power cord
provided.
IilflU
?i"'mm PiJB|lZJHI
26-1160 26-1161 26-1161 26-1161
Figure 5. Acomplete four-drive Mini Disk System.
-—
2-4

Mini Disk Operation
Drive Numbering
TRSDOS requires at least one Mini Disk drive, and can handle up to
four. Under TRSDOS, these drives are referred to as drives 0,1,2 and 3
(where drive is closest to the Expansion Interface, and drive 3is
farthest away). See Figure 5. These designations cannot be changed —
they are built into the ribbon cable connector.
When the Computer attempts abootstrap operation (power-on or
reset), it will automatically attempt to load TRSDOS from drive 0.
Therefore aTRSDOS diskette must be in drive when you power on
or reset the Computer. In fact, the TRSDOS diskette should always
remain in drive while TRSDOS is in use, except in special cases.
Operation
Before powering on the disk system, you need to understand afew
things about how the drives work.
The disk drive does not rotate continuously while it is "on". It only
rotates when aMotor-On signal is sent from the Computer. If more
than one Mini Disks are connected, the Motor-On signal will turn them
all on and off simultaneously, even if only one of them is to be
accessed by the Computer. This signal is sent about asecond before
the Computer accesses the disk, to allow the drives to reach operating
speed.
While the Computer is accessing one of the Mini Disks, the red light
(LED) on the front of that Mini Disk will remain lit.
Caution: Do not open adrive latch to insert or remove adiskette
while the drive motors are running (i.e., while one of the LEDS
is lit).
How aDiskette Works
Adiskette is simply acircular plastic sheet, one side of which is
coated with ahighly polished layer of ferromagnetic material. Similar
to a45 RPM record, the diskette has alarge spindle hole to
accommodate the drive hub, and asmall hole which indexes the
diskette as it rotates.
2-5

Mini Disk Operation
Ablank diskette (either brand-new or magnetically erased) contains
no information. TRSDOS has aspecial utility program (called
FORMAT) which takes ablank diskette and organizes it into
concentric "tracks" and subtracks called "sectors". See Figure 6.
These divisions are like the numbered pages in abook. (FORMAT
also places asmall amount of system and bookkeeping information
onto each diskette. For more information, see Extended Utilities,
FORMAT.)
TRACK 1, SECTOR 8
DATA 256 BYTES
TRACK/SECTOR ID FOR
TRACK 1, SECTOR 8
TRACKS 1,2 35
DIRECTION OF ROTATION
Figure 6. Track/sector organization on aformatted diskette.
Each diskette is permanently sealed inside its jacket to prevent
bending, creasing, scratching or contamination of the diskette
surface. When the diskette is loaded into the drive, ahub assembly
grips the diskette; when the drive motor is on, the diskette
rotates inside its jacket. The specially treated jacket lining cleans
the diskette as it rotates.
Notice that the TRSDOS diskette comes with apiece of tape across
the top (above the label). This tape covers the diskette's write
protect notch. With the notch covered, the diskette is physically
protected from being written to. (A "write operation" is any
alteration of the data stored on the diskette. In contrast, a"read"
does not alter the information —merely accesses it.)
2-6

Mini Disk Operation
Remove the tape from the diskette if you intend to write to it; and
place atape over the notch on any diskette you don't want to
accidentally write to.
See Figure 7.
WRITE PROTECT NOTCH
READ/WRITE NOTCH
WRITE PROTECT TAB
SECTOR HOLE
.s
Figure 7. Adiskette; awrite-protected diskette; adiskette in
protective storage envelope.
Inserting aDiskette
1
.
Be sure the Mini Disk drive is stopped when you insert or
remove adiskette.
2. Open the front of the Mini Disk drive. Gently insert the diskette
into the vertical slot, with the write protect notch up and the
diskette label to the right (Figure 8). Be sure not to close the
latch until the diskette is inserted all the way and seated
properly, or you may damage it.
3. Close the Mini Disk latch. This causes the spindle-hub assembly
to grip the diskette. If the door doesn't close easily, don't
force it. Re-insert the diskette and try again.
Figure 8. Inserting adiskette.
2-7

Mini Disk Operation
Power-Up Sequence
You should always power up the peripherals (disk drives, printer,
Expansion Interface, etc.) first, and the TRS-80 CPU/keyboard last.
Also note that turning the peripherals on and off while the Computer
is on may confuse the system and cause abnormal operation. Work
done on acurrently open file may be lost.
The power switch for each Mini Disk is on the rear of the unit. Power
is "on" when the toggle switch is in the up position, and "off when
the switch is down.
1
.
Turn on the Expansion Interface.
2. Turn on the Mini Disk drives: first the terminal drive, 26-1 160,
then the other drives, if any.
3. When you turn on the TRS-80 CPU/keyboard, the Computer
will instantly attempt to load TRSDOS from Drive 0. So before
turning on the CPU, carefully insert the TRSDOS diskette into
drive as explained above under "Inserting aDiskette". You
may also want to insert formatted diskettes into the other drives
now; however, these may be inserted any time the drives are
stopped.
Another approach would be to plug all devices into an adequate
power strip and turn them all on with asingle switch.
Care of Diskettes
Diskettes are precision recording media. Handle them very carefully
to get maximum life from each diskette. In general, follow the special
handling precautions used with both tape cassettes and high fidelity
records.
1. Keep the diskette in its storage envelope whenever it is not in
one of the drives. Don't leave the diskettes in the drives
needlessly, for example, when the system is turned off.
2. Keep diskettes away from magnetic fields (transformers, AC
motors, magnets, etc.). Strong magnetic fields will destroy
information on the diskettes.
3. Handle the diskette by the jacket only —don't touch any of the
exposed surfaces. Don't try to wipe or clean the diskette surface;
you might scratch it and destroy data.
4. Keep the diskette away from heat and direct sunlight. See the
"Specifications" section below for storage temperature range.
2-8