Radio Shack TRS-80 User manual

PRELIMINARY USER’S MANUAL
MICRO COMPUTER
Catalog Numbers:
2 -1001
2 -1201
14-841
©Copyright 1977, by Radio Shack, A Division of Tandy Corporation, ort Worth, Texas 76107, U. S. A. |

P. 2
TRS-80 PRELIMINARY MANUAL
This User's Manual is not intended to e the final, complete one.
Since we know you are eager to start using your Microcomputer
system, we decided not to delay your shipment any further ... and
to send you this Preliminary Manual (along with some game tapes
and other materials).
SETTING UP THE SYSTEM
*
Carefully unpack the system. Remove all packing material. 3e
sure you locate all ca les, papers, tapes, etc. Save the packing
material in case you need to transport the system.
Connecting the Video Monitor and Key oard:
1. Connect the power cord from the Video Monitor to a
source 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
e a le to plug the Monitor's power cord in.
Do not attempt to force this wide prong into the
extension cord; use a wall outlet if at all possi le.
2. Connect the power cord of the Power Supply to a source of
120 volts, 60 Hz AC power.

P. 3
3. Connect the gray ca le from the front of the Video Monitor
to the VIDEO jack on the ack of the Key oard Assem ly.
Take care to line up the pins correctly (the plug fits
only one way).
4. Connect the gray ca le from the Power Supply to the POWER
jack on the ack of the Key oard Assem ly. Again, take
care to mate the connection correctly.
Connecting the Cassette Recorder:
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. Load atteries into the CTR-41 as descri ed in the Manual.
Or make connections for 120 volt AC power.
2. Connect the short ca le (DIN plug on one end and 3 plugs
on the other) to the TAPE jack on the ack of the Key oard
Assem ly. Be sure you get the plug to mate correctly.
3. The 3 plugs on the other end of this ca le are for
connecting to the CTR-41.
A. Connect the lack 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).
3. Connect the larger gray plug into the AUX jack
on the CTR-41. This connection provides the
recording signal to record orograms 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 uilt-in Mic
so it won't pick-up sounds while you are recording tapes).

P. 4
C. Connect the smaller gray plug into the REM jack
on the CTR-41. This allows the TRS-80 to remotely
control the CTR-41's motor (turn tape motion on and
off for recording and playing tapes).
Notes On Using The Recorder
There are a num er of things you should e aware of as you use the
Cassette Tape System:
1. To Play a tape (load a taped program into the TRS-80), you
must have the CTR-41's Volume control set to 7 to 8 Then
press the CTR-41's PLAY key and then type CLOAD on the TRS-80
and ENTER this command. This will start the tape motion. An *
will appear on the top line of the Monitor; a second * will
link, indicating the program is loading. When loading is
done, the TRS-80 will automatically t u n the CTR-41 off and
flash READY on the screen. You are then ready to RUN the
program (type in RUN and hit ENTER) .
2. To Record a program from the TRS-80, press the CTR-41's
RECORD and PLAY keys simultaneously. Then type CSAVE on
the TRS-80 and ENTER this command. When the program has een
recorded, the TRS-80 will automatically turn 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 a third recording of the tape, just to
e sure they have a good recording.
NOTE: To load the full 4K of RAM in the TRS-80 takes less than
3 minutes of tape. Short programs will take only a few
seconds of tace.

P. 5
3. Use the CTR-41's Tape Counter to aid you in locating programs
on tapes.
4. For est results, use Radio Shack's special 10 minute Computer
Tape Cassettes (especially designed for recording computer
programs). If you use standard audio tape cassettes, e sure
to use top quality, such as Realistic SUPERTAPE or Cr02.
Keep in mind that audio cassettes have lead-ins on oth
ends ( lue non-magnetic mylar material) — you can not
record on the leader portion of the tape. Advance the tape
past the leader efore recording a program.
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 a cassette, 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 a taped program permanently, reak off the
erase protect ta 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 a tape has a program 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.

P. 6
TURNING THE SYSTEM ON
Turn on the Video Monitor y pressing the POWER utton. Turn on
the TRS-80 Key oard y pressing the POWER utton on the ack
(next to the POWER Jack); the red LED just to the right of the
Key oard should light up and the screen should show READY.
Adjust C (contrast) and B ( rightness) controls on the front of
the Monitor for the sharpest display. Set Brightness so the
ackground is gray and the words are white. Do not set Brightness
too high.
If Monitor does not show READY, press the Key oard's POWER
switch off, wait 10 seconds, and then turn it on again.
(Pressing the power switch slowly can cause the machine to
"get confused". Turn it on with a quick push.)
Now type in P.m. and hit ENTER. This is a test to see that the
Computer powered-up properly. The display should read:
P.M.
3533
If the num er is not 3583, turn the Key oard's POWER switch off,
wait 10 seconds, and then turn it on again. Repeat the test and
verify that the num er is 3583.(It's good practice to perform this
simple test whenever you turn on the TRS-80. Always type new and
ENTER efore performing the test.)
NOTE: There is a Reset utton inside a door at the left
rear of the Key oard assem ly. This Reset utton can e
used to unlock a looping program or if the TRS-80 does
not turn off a cassette or in other such a normal program
situations.

P. 7
GETTING STARTED
This Preliminary User's Manual is not intended to e a detailed,
complete course in Radio Shack's Level I BASIC. For that you'll
have to wait for the complete Manual. However, we will try to give
you enough help here so you can exercise your Computer a little
efore getting into the meat.
IMPORTANT NOTE: Each line of a program must e entered into the
Computer. You do this y pressing ENTER key. To
correct a typing error, press the ackspace key
(-*-) ; repeat as necessary to erase the error. If
you have already ENTERed a line and notice an error,
'type the same line over again — the Computer
always takes the last line typed in.
Let's try the "calculator mode" first. It's the easiest. Type
the following:
PRINT 5-2 (hit ENTER) NOTE: With the TRS-80, there is no
The Display will show need to use SHIFT to type capital
3 letters (all letters are capital).
SHIFT is needed only for the keys
READY which have two sym ols.
> -
This means the Computer is ready for more. (From now on, we won't
repeat the READY and >_ .)
Now try
PRINT 2/3, 2*8 (Hit ENTER. Note you must use PRINT to receive a
display.)

P. 8
.666667 16 (the answer to the first — 2 divided y 3 —
is given first. The second answer — 2 multiplied
y 8 is given second, moved over 16 spaces
ecause of the comma.)
You can write a program for these same functions. A program must
have a num er for each line. Try this:
10 PRINT 14.5 + 3 (Remem er to hit ENTER at the end of each line.)
20 PRINT 6.1 - 4.2
30 PRINT 7/22
40 PRINT 8*2.1
This is a program. Each line egins with a num er. To execute (run)
the program, type RUN and hit ENTER. The screen will display —
17.5
1.9
.318182
16.8
Press CLEAR and the screen will e lank except for the little
cursor (_) at the upper left hand comer.
If you want to recall the program that is in the Computer, type
LIST and the program will e displayed on the screen.
Use LIST any time you want to check the program that is stored
in the Computer. You can use LIST to check a program that you
have loaded from a cassette tape.
If you want to delete a line, all you have to do is type that
line num er and ENTER it. That replaces the existing program line
num er with a lank line. Try it on the program you have in the
Computer. Then LIST the program and see what has happened.

P. 9
Notes on Line Num ers:
You don't have to type line num ers in sequence. The Computer
automatically puts lines in sequence.
You can add line num ers at any time (as long as you have a } _
on the screen).
Don't num er lines in direct sequence; leave lank num ers so
you can add more to your program later on. Example, use 10, 20,
30, etc.; then later on as you work with the program, you can
add 15, 25 ... (or any or all num ers etween the lines you have
used) .
More on PRINTinq:
Often you will want to put some wording in with your program, to
explain the meaning of calculations. Try this;
PRINT "THE APPROXIMATE VALUE OF PI IS", 22/7 (Hit ENTER)
The screen displays
THE APPROXIMATE VALUE OF PI IS 3.14286
The comma (,) moved the num er to the next 16 character frame
of the printing field. Try a semicolon instead and see what
happens.
Try the following;
PRINT 1,2,3,4 (Remem er to hit ENTER)
1 . 2 3 4
Now try:
PRINT 1;2;3;4 (Don’t forget to ENTER it)
1 2 3 4
The commas space out the printing into columns 16 characters wide.
The semicolons give just one extra space. Try some more till you get
the feel of hew and where the printing will e.

P. 10
Now, type RUN. What happened? The screen came ack with
17.5
1.9
.318182
16.8
Why? The program that we typed in earlier is still in the
Computer? Not sure? Type LIST and see.
How to clear out previous programs? Of course we could erase
each line ( y typing in line num ers one at a time and ENTERing
them). But there is an easier way. Type NEW. This clears the
memory of all previous programs and you're ready to enter more.
Always type NEW efore loading new programs from cassettes or
typing in new programs.
Type
10 PRINT "HELLO THERE. I AM YOUR NEW TRS-80 MICROCOMPUTER:"
RUN this one-line program:
HELLO THERE. I AM YOUR NEW TRS-80 MICROCOMPUTER!
Add another line:
20 PRINT "YOU CALLED, MASTER. DO YOU HAVE A COMMAND?"
Now RUN the program. You get oth lines.
HELLO THERE. I AM YOUR NEW TRS-80 MICROCOMPUTER!
YOU CALLED, MASTER. DO YOU HAVE A COMMAND?
Now try it again. This time try talking to it; type in YES.
WHAT?
The Computer is telling you it does not know what you want.
You see, you must talk to it in its own language. The TRS-80
understands the BASIC language (a simple language for Computers).

p. 11
Add another line to your program:
15 PRINT
What is that going to add? Just an empty line. RUN it and you'll
see that the lines are separated; looks etter now.
Let's add a REMark statement at the eginning. A REMark statement
is not part of the program, it is just like a note or reminder
to you.
5 REM ** THIS IS MY FIRST COMPUTER PROGRAM **
RUN the program and you'll see that line 5 had no effect. Now
pull a list (type LIST) and sure enough, line 5 is there.
Big- & Little Num ers
The TRS-80 uses scientific notation to handle very large and
very small num ers. For example, the num er 5,000,000 ecomes
5E+06; this means the num er 5 followed y 6 zeros. The
num er .000,005 ecomes 5E-06; this means 6 decimal places
to the left of 5. Scientific notation is a very common method
for listing very large and very small num ers (they are much
easier to work with this way).
Sequence of Math Operators
Your TRS-80 uses the 4 fundamental math functions. You also can
use parentheses in your math formulas. The following rules apply
for ( ) and sequence of Math Operators:
1. All operations inside parentheses are performed first.
2. All operations uried deepest within ( ) are performed first.
IE. If you have operations nested inside ( ), which are nested

P.12
inside more ( ), the innermost ones are solved first.
3. Then, the Computer figures multiplication and division
operations ... in sequence from left to right. Then it
starts at the left again and performs addition and su traction.
IE. If you have a "chain" calculation which has multiplication,
division, addition and su traction, the Computer does
multiplication and division first, then addition and su traction.
4. A pro lem listed as (X)(Y) will not tell the Computer to
multiply. X * Y is for multiplication.
If you want to e sure your pro lems are calculated correctly,
use ( ) around operations which you want performed first.
NOTE: INT, RND and ABS functions are performed efore multiplication
and division.
Conditional Branching
Type in the following program.
10 A = 5
20 IF A = 5 THEN 50
30 PRINT "A DOES NOT EQUAL 5"
40 END
50 PRINT "A EQUALS 5"
RUN this program. The screen will show:
A EQUALS 5
In line 10 you assigned the value of 5 to A. Line 20 checked the
value of A, found it was 5 and ranched to 50 which resulted in
the printing. Now, change line 10 to give A some other value and
RUN it. T e display will s ow:
A DOES NOT EQUAL 5

P. 13
Of course, you may not want to change line 10 each time you
want to give the Computer a value of A. Let's introduce another
BASIC statement: INPUT. Add the following lines:
5 PRINT "THE VALUE I WISH TO GIVE A IS"
10 INPUT A
RUN the program. The screen will show:
THE VALUE I WISH TO GIVE A IS
?
The Computer is asking you to give it a value for A. Type a
num er and ENTER it. See what happens now. Try other num ers.
Now change line 5 as follows :
5 INPUT "THE VALUE I WISH TO GIVE A IS";A
Delete line 10 (type a line 10 and ENTER it with nothing else).
Run the program now and see what happens :
THE VALUE I WISH TO GIVE A IS?_
Type a num er; ENTER it and see if the program works the same.
You made a num er of changes with lines 5 and 10:
A. Changed PRINT to INPUT.
B. Changed A to e on the same line as the printing info.
C. Eliminated one line.
This illustrates one of the ways you can shorten a program.
(We'll have lots more on this in the final version of the
User's Manual.)

P. 14
The conditional ranching we tried a ove (IF .... THEN) can e
used for other purposes too. We can use a statement GOTO, telling
the Computer to go to a specific line num er and continue from
there. Or, we can tell the Computer to go to a su -routine
program (ON ... GOSUB 32000). Branching ecomes a very powerful
tool in the hands of an experienced programmer (hang in there,
you'll ecome one).
Counting and Looping
Try this.
10 A = 0
20 A = A + 1
30 PRINT A
40 GOTO 20
RUN it and see what happens.
To stop the Computer, hit BREAK. To restart it, type CONT (for
CONTinue) . Hit CLEAR and see vjhat happens.
Now change line 30 to end with a comma. RUN it. Then try a semi-colon.
RUN it.
Add a line for ranching.
35 IF A = 100 GOTO 100
100 END
RUN it. Or, you could com ine lines 35 and 100 as follows:
35 IF A = 100 END

P. 15
Try this:
10 FOR fJ = 1 TO 10
20 PRINT N*N
30 NEXT N
RUN this simple program. What happened? We set up a FOR-NEXT loop.
Line 10 set a series of values for N (from 1 to 10). Line 20
tells the Computer to multiply N times N (the square of N). Line
30 tells the Computer to take the next N. This program goes through
10 loops. Change line 10 for more loops. Change line 20 to end
with a comma or semi-colon.
NOTE: A FOR-NEXT loop automatically increases the num er y 1,
unless you tell it differently. Change 10 to 10 FOR N =
1 TO 10 STEP 2. RUN it.
Loops can e com ined — as long as the loops nest within each
other (ie. finish one loop efore going ack to the first). Example:
(type in NEW to clear out the memory):
Outer
Loop
("B" Loop is
nested inside
"A" Loop)
Note how we've indented info for the B Loop so you can see it
easier. This technique is a great aid to proper programming.
RUN the program.
The inner loop must e completed efore going ack to the outer loop.
Loops are extremely useful tools for computer programs. We'll cover
them in great detail in the final User's Manual.

P. 16
READ and DATA
Up to now we've looked at two ways to enter num ers into a
program. One is y assigning a value to a letter (A = 5).
Another is with the INPUT statement. Another method is with
DATA.
Try this :
10 DATA 1,2,3,4,5
20 READ A,B,C,D,E
30 PRINT A ;B ;C ; D;E
RUN this program.
NOTE: DATA statements can have values assigned with commas
separating them; same with READ statements.
DATA lines are always read from left to right y READ statements.
It does not matter where DATA statements come in the sequence of
a program. Move line 10 to line 25. Move it to line 10000. Works
the same in any case.
TAB Function
The TAB function is just like the Ta on a typewriter. It tells
the Computer to start printing at a specified num er of spaces
in from the left. Try this:
10 PRINT TAB(12),"@@@@"
20 PRINT TAB(32),"####”
RUN it.
@@@@

P. 17
PRINT AT Function
The screen can e divided up into 1024 individual squares. These
squares are used for the Graphics functions, ut you can also
use them with a PRINT function.
PRINT AT 650 , "TRS-80 MICROCOMPUTER"
ENTER this and see where the message is printed. There is a pad
of paper with markings showing the location of these squares on
the screen. Examine these pages and soon you'll e a le to set up
print statements for almost any part of the screen.
Graphics Functions
There are three Graphics statements. SET, RESET and POINT.
SET turns on a square on the screen. RESET turns a square off.
POINT checks for the presence of a signal at a square on the
screen. Locations on the screen are defined with coordinates
X and Y. X can e any value from 0 to 127. Y can e any value from
0 to 47.
Try this:
10 X = 27
20 Y = 27
30 SET (X, Y)
RUN it. Change the values of X and Y. (NOTE: Coordinates are not
limited to X and Y. Try any
letter com inations.)
Draw some lines with the SET function.
10 X = 32
20 FOR Y = 0 to 47
30 SET (X, Y)
40 NEXT Y
RUN it.

P. 18
Change the value of X. Also, try
10 TO 20; 0 TO 47 STEP 5).
changing the loop for Y (0 TO 10;
Try this program:
10 FOR Y = 0 TO 10 (Lines 10 and 50 set up a loop
20 FOR X = 0 TO 40 for Y. Lines 20 and 40 set up
30 SET (X, Y) a loop for X. Line 30 SETS the
40 NEXT X
50 NEXT Y
graphic display.)
60 FOR Y = 3 TO 7 (Lines 60 and 100 set up a loop
70 FOR X = 10 TO 30 for Y. Lines 70 and 90 set up
80 RESET (X,Y) a loop for X. Line 80 turns off
90 NEXT X
100 NEXT y
the graphic display.)
RUN the program. The READY goofs
of it?
up the display. How to get rid
How a out a timer loop? What's that? Just a loop with no printing;
no function ut to keep the Computer usy counting while we look
at our display. Try this:
110 FOR A = 1 to 5000 (This tells the Computer to count
120 NEXT A from 1 to 5000 for A. We did not
RUN this program now.
tell it to print A ... or to
do anything. It is just going to
e usy for a while.)

P. 19
Random Num er Generator
One of the most interesting functions of the TRS-80 is its
a ility to generate random num ers. Try this:
10 X = RND (10)
20 PRINT X
30 GOTO 10
RUN it. Too much? BREAK the program and add:
5 FOR N = 1 to 10
Change line 30:
30 NEXT N
RUN it. Then add a comma at the end of line 20 and change the
num er for N so you can fill up the screen. Then, use a semi-colon
and change N again to fill up the screen efore the program ends.
A reviations
Most of the statements and commands can e a reviated. This
simplifies programming. Look at the section LISTING OF RADIO
SHACK'S LEVEL I BASIC for all a reviations, along with a
complete listing of commands and statements and functions.

P. 20
Statement/
A reviation
INPUT/IN.
DATA/D.
READ (no a r.
RESTORE/RES.
PRINT/P.
PRINT AT/P.
LISTING OF RADIO SHACK'S LEVEL I BASIC
__________ Example______________________________
INPUT X, Y, Z (Computer will request data for
varia les X, Y and Z)
INPUT "ANY MESSAGE ON SCREEN"; X (Computer will
print info inside quotes and request data for
varia le X)
DATA X, Y, Z (holds data or values of varia les
for later READ statements)
) READ X, Y, Z (instructs Computer to READ
values assigned y DATA statements)
RESTORE (instructs Computer to start reading from
first DATA statement)
PRINT X (Computer will print value of X)
PRINT X, "ANY MESSAGE", Y, "ANY MESSAGE";
(, starts printing in next 16-character zone)
(; prints with no spacing)
(; at end of PRINT statement ties in the
next line ie. suppresses carriage return)
Print Modifiers
AT PRINT AT 123, X, Y, Z
PRINT AT X, "ANY MESSAGE"
PRINT AT X + Y
( egins printing at the location defined y
the integer, varia le or expression. It must
e in the range of 0 to 1023)