Radio Shack TRS-80 User manual

CAT. NUMBER
26-2101
USER'S MANUAL
Rsdie/haek
CUSTOM MANUFACTURED IN U.S.A. BY RADIO SHACK MADIVISION OF TANDY CORPORATION

LIMITED WARRANTY
Radio Shack warrants for aperiod of 90 days from the date of delivery to customer that the computer hardware
described herein shall be free from defects in material and workmanship under normal use and service. This
warranty shall be void if the computer case or cabinet is opened or if the unit is altered or modified. During this
period, if adefect should occur, the product must be returned to aRadio Shack store or dealer for repair.
Customer's sole and exclusive remedy in the event of defect is expressly limited to the correction of the defect
by adjustment, repair or replacement at Radio Shack's election and sole expense, except there shall be no
obligation to replace or repair items which by their nature are expendable. No representation or other affirma-
tion of fact, including but not limited to statements regarding capacity, suitability for use, or performance of the
equipment, shall be or be deemed to be awarranty or representation by Radio Shack, for any purpose, nor give
rise to any liability or obligation of Radio Shack whatsoever.
EXCEPT AS SPECIFICALLY PROVIDED IN THIS AGREEMENT, THERE ARE NO OTHER WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTIES OF MER-
CHANTABILITY OR FITNESS FOR APARTICULAR PURPOSE AND IN NO EVENT SHALL RADIO
SHACK BE LIABLE FOR LOSS OF PROFITS OR BENEFITS, INDIRECT, SPECIAL, CONSEQUENTIAL OR
OTHER SIMILAR DAMAGES ARISING OUT OF ANY BREACH OF THIS WARRANTY OR OTHERWISE.
IMPORTANT NOTICE
ALL RADIO SHACK COMPUTER PROGRAMS ARE DISTRIBUTED ON AN "AS IS" BASIS WITHOUT
WARRANTY
Radio Shack shall have no liability or responsibility to customer or any other person or entity with respect to
any liability, loss or damage caused or alleged to be caused directly or indirectly by computer equipment or
programs sold by Radio Shack, including but not limited to any interruption of service, loss of business or
anticipatory profits or consequential damages resulting from the use or operation of such computer or computer
programs.
NOTE: Good data processing procedure dictates that the user test the program, run and test sample sets of
data, and run the system in parallel with the system previously in use for aperiod of time adequate to
insure that results of operation of the computer or program are satisfactory.

APersonal Note from the Author
1pntv of good conventional
,-u vThere are plenty or &u
books, and plenty that ^anything
T---^3 riSf^o^j- rrnSr;rk
^dio Shack TRS-80 counter an ^faun ^air ^.^
acompetent P^^^oyant and ridiculous technique ^
and unconventional, £la**°y*fun with your computer.
Swas used. 1want you to have ^^^.^ to £e«.
you to be afraid of it, &M
,« out on this book were good tas contains no
The only «Stra^"fyourintelligence. Beyond that ^attempt
attempt not to insult.your ^intimidate you >^&u
-. snow jobs", no effor P.dea that computers
to sell you anything excep
that bard to learn to use. ^above
,ii, as though savoring agoon rout ine
Sit back, relax, ^fj^JjV. I'll supply you £**!*
all, let your imaSxn3t*°n*d.The real enjoyment begin becomeB
facts and -^^s
eS
thrcr
n
eative juices ^f^Vot the other way
imagination starts the c^tM master »° into an
at0°
dVtStToi- Uevolves fro, just abo, P
S-siofofyour personality
Enjoy your new computer!
Dr. David A- Lien
San Diego -1977

FIRST EDITION
SECOND PRINTING —1978
All rights reserved. Reproduction or use, without
express permission, of editorial or pictorial con-
tent, in any manner, is prohibited. No patent
liability is assumed with respect to the use of the
information contained herein. While every pre-
caution 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 contained herein.
©Copyright 1977, Radio Shack,
ADivision of Tandy Corporation,
Fort Worth, Texas 76102, U.S.A.
Printed in the United States of America

Table of Contents
This User's Manual and You 4
Part A: Chapter 1Computer Etiquette. PRINT, NEW, and RUN 7
Chapter 2Expanding aProgram. LIST, REM, END, LET, WHAT?, HOW? 11
Chapter 3Math Operators 17
Chapter 4Scientific Notation 23
Chapter 5Order of Operations. Use of Parentheses 25
Chapter 6Relational Operators. IF-THEN, GOTO '
[29
Chapter 7INPUTting Data 33
Chapter 8Calculator Mode. MEM, SORRY '..'.'.'. '.37
Chapter 9Using Cassette Tape for Mass Storage. CLOAD, CSAVE 41
Chapter 10 Loops. FOR-NEXT, STEP, CLS, Break Key 45
Chapter 11Timer Loops. LIST ###, RUN ###, STOP, CONT 53
Chapter 12Formatting Output with TAB 61
Chapter 1
3
Nested Loops 65
Chapter 14 INT Function 69
Chapter 15 More Branching Statements. Subroutines. ON-GOTO, GOSUB
ON-GOSUB, RETURN 77
Chapter 16 READ, DATA, RESTORE. String Variables A$ and B$ 85
Chapter 17ABS Function 93
Chapter 18 Level IShorthand Dialect. Multiple-Statement Lines 95
Chapter 19Generating Random Numbers with RND 99
Chapter 20 Video Display Graphics. SET, RESET 105
Chapter 21 Arrays Using A(X) 123
Chapter 22 Advanced Graphics. PRINT AT, POINT 133
Chapter 23 Flowcharting 141
Chapter 24 Logical Operators. *(AND), +(OR) !.T47
Chapter 25 Advanced Subroutines 155
Chapter 26 Debugging Programs 165
Part B: Sample Answers to Programming Exercises in Chapters 3through 25 177
Part C: Prepared User's Programs 201
Appendix:
Appendix A: Prepared User Subroutines 216
Appendix B: Cassette Data Files 221
Appendix C: Combined Function and ROM Test 225
SUMMARY OF LEVEL IBASIC 232

This User's Manual and You
This Manual has been written for the average person who has no
experience with aComputer. We've deliberately kept our style
light and humorous (some may even say it's corny!) ... we think
this will make your learning experience fun.
(And why shouldn't learning be fun ...?)
The Manual is organized in three basic sections:
A. 26 Chapters which introduce you to various capabilities of
the Computer; in small enough bites so you won't choke.
These Chapters include numerous little check points and
examples (as we get deeper into the book the examples get
deeper).
At the end of the Chapters we've given some Exercises -to
give you achance to try out your knowledge ON YOUR
OWN.
B. Asection with sample answers to the Exercises in each
Chapter. You can see how you make out with your attempts
at programming.
C. Asection with some User's Programs -some good
examples of interesting and practical programs (some for
fun, some for business, some for education, etc.).
We've also included some helpful information in an APPENDIX.
The Manual is written in astyle where the Computer assists you in
learning (educators might like to call it "Computer Assisted
Instruction" ...we'll try to avoid trying to impress you with that
type of fancy wording).
So, on you go -and we hope you have as much fun with this book
as we did preparing it (we had some headaches too . . . hope you
don't have any of those).
4

SETTING UP THE SYSTEM
Carefully unpack the system. Remove all packing material. Be sure you
locate all cables, papers, tapes, etc. Save the packing material in case
you need to transport the system.
Connecting the Video Display and Keyboard:
1. Connect the power cord from the Video Display to asource of 120
volts, 60 Hz AC power. Note that one prong of the AC plug is wider
than the other —the wide prong should go into the widest slot of
the AC socket.
NOTE: If you use an AC extension cord, you may not be able to
plug the Display's power cord in. Do not attempt to force
this wide prong into the extension cord; use awall outlet
if at all possible.
Connect the power cord of the Power Supply to asource of 120
volts, 60 Hz AC power.
Connect the gray cable from the front of the Video Monitor to the
VIDEO jack on the back of the Keyboard Assembly. Take care to
line up the pins correctly (the plug fits only one way).
NOTE: Before the next step, be sure the POWER switch on the
back of the Keyboard is off (button out).
Connect the gray cable from the Power Supply to the POWER
jack on the back of the Keyboard Assembly. Again, take care to
mate the connection correctly.
2.
3.
4.
POWER BUTTON
POWER POWER VIDEO TAPE
BUTTON
(ON REAR)
Connecting the Cassette Recorder:
NOTE: You do not need to connect the Cassette Recorder unless you
plan to record programs or to load taped programs into the TRS-80.
1.
2.
Load batteries into the CTR-41 as described in the Manual. Or
make connections for 120 volt AC power.
Connect the short cable (DIN plug on one end and 3plugs on the
other) to the TAPE jack on the back of the Keyboard Assembly.
Be sure you get the plug to mate correctly.
The 3plugs on the other end of this cable are for connecting to
the CTR-41.
A. Connect the black plug into the EAR jack on the side of the
CTR-41. This connection provides the output signal from the
CTR-41 to the TRS-80 (for loading Tape programs into the
TRS-80).
Connect the larger gray plug into the AUX jack on the CTR-41.
This connection provides the recording signal to record pro-
grams from the TRS-80 onto the CTR-41 's tape.
Also, plug the Dummy Plug (provided with the CTR-41) into
the MIC jack (this disconnects the built-in Mic so it won't pick-
up sounds while you are loading tapes).
NOTE: Be sure you always use the Dummy Plug when loading
programs onto tape (Recording).
B
Dummy Plug
C. Connect the smaller gray plug into the REM jack on the
CTR-41. This allows the TRS-80 to automatically control the
CTR-41 's motor (turn tape motion on and off for recording
and playing tapes).
Notes On Using The Recorder
There are anumber of things you should be aware of as you use the
Cassette Tape System: (Some of this will be covered in greater detail
in Chapter 9...but some of you can't wait till then ...can you!)
1. To Play atape (load ataped program into the TRS-80), you must
have the CTR-41 's Volume control set to 7to 8. Then press the
CTR-41
'
sPLAY key and then type CLOAD on the TRS-80 and
I3i?fcl3;l this command. This will start the tape motion. An *will
appear on the top line of the Monitor; asecond *will blink, indi-
cating the program is loading. When loading is done, the TRS-80
will automatically turn the CTR-41 off and flash READY on the
screen. You are then ready to RUN the program (type in
and hit 021133).

TURNING THE SYSTEM ON
2. To Record aprogram from the TRS-80, press the CTR-41's
RECORD and PLAY keys simultaneously. Then type CSAVE on
the TRS-80 and Hflhfrfclthis command. When the program has
been recorded, the TRS-80 will automatically tum the CTR-41 off
and flash READY on the screen. Now you have your program on
tape (it still is in the TRS-80 also). Many computer users make a
second or even athird recording of the tape, just to be sure they
have agood recording.
NOTE: To load the full 4K of RAM in the TRS-80 takes less than
3minutes of tape. Short programs will take only afew
seconds of tape.
3. Use the CTR-41 's Tape Counter to aid you in locating programs on
tapes.
4. For best results, use Radio Shack's special 10 minute Computer
Tape Cassettes (especially designed for recording computer pro-
grams). If you use standard audio tape cassettes, be sure to use top
quality, such as Realistic SUPERTAPE. Keep in mind that audio
cassettes have lead-ins on both ends (blue non-magnetic mylar
material) —you can not record on the leader portion of the tape.
Advance the tape past the leader before recording aprogram.
5. When you are not going to use a CTR-41 for loading or recording
programs, do not leave RECORD or PLAY keys down (press
STOP).
6. To REWIND or FAST-Forward acassette, you must disconnect the
plug from the REM jack (with REM jack connected, the TRS-80
controls tape motion).
7. If you want to save ataped program permanently, break off the
erase protect tab on the cassette (see CTR-41 Manual).
8. Do not expose recorded tapes to magnetic fields. Avoid placing
your tapes near the Power Supply.
9. To check if atape has aprogram recorded on it, you can disconnect
the plug from the EAR jack (also disconnect the REM plug so
you can control the CTR-41 with the keys) and Play the tape;
you'll hear the program material from the speaker.
Turn on the Video Display by pressing the POWER button. Tum on
the TRS-80 Keyboard by pressing the POWER button on the back
(next to the POWER jack); the red LED just to the right of the Key-
board should light up and the screen should show READY .Adjust C
(contrast) and B(brightness) controls on the front of the Display for
the sharpest display. Set Brightness so the background is gray and the
words are white. Do not set Brightness too high.
If Display does not show READY ,press the Keyboard's POWER
switch off and on again,
NOTE: There is aReset button inside adoor at the left rear of the
Keyboard assembly. This Reset button can be used to unlock aloop-
ing program or if the TRS-80 does not turn off acassette or in other
such abnormal program situations.
One More Thought -', .-' ')".; :
You're all ready now, right? Well, maybe. But let's just prepare you
for the TRS-80 and Manual with one more thought ...
How do you "talk" to a Computer? In Binary Numbers? In Elec-
tronics (is there such alanguage ..,)? In English ...?
Well, we use asimplified form of English —it's called the BASIC
Language (Beginners All-purpose Symbolic Instruction Code). (There
are lots of other "computer languages", but this is the easiest.) This
Manual covers Radio Shack's LEVEL IBASIC.
As you go through this Manual you'll learn the different words of this
simple computer language —and how to punctuate (VERY IMPOR-
TANT) —and how to apply all of it for fun and practical benefit. It's
an easy language to learn —but remember, you've got to use the
language that the TRS-80 understands (well be giving you some
examples of wrong language use and you'll see what happens).
6

Chapter 1
Computer Etiquette
From the moment you turn it on, the TRS-80 follows awell-defined set of rules for coping
with you, the "master," This makes it an especially easy computer to use. To alarge extent,
all you have to do is say the right thing (via the keyboard) at the right time. Of course, there
are lots of "right things" to say; putting them together for apurpose is called programming.
In this chapter we're going to start aconversation with the TRS-80 by teaching it afew
simple social graces. At the same time, you'll be learning the fundamentals of computer
etiquette. You'll even write, wonder of wonders, your first TRS-80 computer program!
Getting READY
1. Connect the keyboard-computer, Video Display and Power Supply as explained in the
previous section. Plug Video Display and Power Supply into 120-volt AC outlets.
2. Press POWER button on Video Display and the back of the Keyboard. Give the video
tube afew seconds to warm up.
3. READY ____
>— should appear in the upper left corner of the screen. Press the QQQ|Q key
several times to produce acolumn of READY messages. The Computer is trying to tell
you something: "I'm ready —it's your turn to do something!
"
To make sure you start off withaclean slate —erasing all traces of prior programs or tests —
type NEW and press |3fllia;| ,The Computer will respond by erasing the screen and print-
ing
READY
>—
at the top of the screen.
Now type in p.M.and I3i?na;l .This is atest to see that the Computer powered up proper-
ly. The display should read:
P.M.
3583
This set of rules is permanently stored in the
Computer in two programs, called the monitor
and the interpreter.
is amonitor command. It tells the Com-
puter to take alook at whatever you've typed on
the screen. In step 3, you didn't type anything,
so the Computer just comes back with another
READY .
Hit Ekey, (Tj key, [M] key and Qkey.
Don't use shift key —letters are always capital for
TRS-80.
If you have 8K of memory, the number should
be 7679. With 16K of memory, it should be
15871.

If the number is not 3583, turn the Computer off, using the pushbutton on the right rear
corner of the keyboard. Wait about 10 seconds and turn it on again. Repeat the test and
verify that the number is 3583.
Just What Is aComputer Program?
Aprogram is asequence of instructions that the Computer stores until we command it to
follow (or "execute") those instructions. Programs for the TRS-80. are written in alanguage
called BASIC —and that should give you an idea of how easy it is to learn!
Let's write asimple one-line program to let the TRS-80 introduce itself. First be sure the
last line on the screen shows a>, which we call the "prompt". This is the Computer's way of
saying, "Go ahead —do something! "Now type the following line, exactly as shown
:
10 PRINT "HELLO THERE. IAM YOUR NEW TRS-80 MICROCGMPUTER !"
Do not hit QZQ1D key yet!
If you made amistake, don't worry —it's much easier to correct typing errors on the
TRS-80 than it is on aregular typewriter. No rubber erasers or white paint to fuss with! Just
use the backspace key *. Each time you press this key, the rightmost character will be
erased. If your error was at the beginning of the line, you'll have to erase your way back to
that point and then retype the rest of the line.
Now go back and examine VERY CAREFULLY what you have typed:
1. Did you enclose everything after the word PRINT in quotation marks?
2. Are there any extra quotation marks?
If everything's okay, you can press l^ll^jp .The >prompt will reappear. The Computer is
telling you, "Fine —what's next?"
If It's Too Late
If you find an error after you've typed aline and pressed la^il^jj ,you cannot use the*
backspace key to correct it. Instead, retype the entire line correctly. As soon as you
1^113.11 the line, it will replace the incorrect one. This is because both of them share the
same starting number (in this case, 1(8).
It's good practice fa* perform this simple test
whenever you turn on the TRS-80. Always type
N£W and r^h^il befor* performing the test.
.As for what the test tests —we'll wait a'few
chapters for that!
"EXTRA CAREFUL'
You don't have to use the ishift jkey to get a
capital letter —that's the only kind of letter'theV; :
:
TRS-80 uses. However, some of the keys do
have two characters printed on them. Use the ,.,';'/. >}
.iSHift\key to get the upper cha?facters-—,\
\
j£e ,'the
"marks and the exclamation pomt(!>.
See- the little "dash" (—)that moves across th*--
screen as you type in aletter? This is the "cursor".
It lets you know exactly where the next character
you type will be printed oh the screen. Pushing the
space bar moves the cursor along one space, with-
i>ttt printing anything. :
If you; press ^i?»3:l asecond time,the screen
''Wffl"'»e&i.;.l.-'-r; felifO .[''-L-':
.~:,"yz:$:?,
READY
This is reassuring/hut riotheeessaty —as long as
the bottom item on the screen is the>pfompt,
you know it's "yoor turn."