Commodore 64 User Manual

C=

commodore

COMPUTERS

USER

'S MANUAL STATEMENT

"THIS EQUIPMENT GENERATES AND USES RADIO FREQUENCY ENER­GY AND IF NOT INSTALLED PROPERLY, THAT IS, IN STRICT ACCORD­ANCE WITH THE MANUFACTURERS' INSTRUCTIONS, MAY CAUSE IN­TERFERENCE TO RADIO AND TELEVISION RECEPTION. IT HAS BEEN
TYPE TESTED AND FOUND TO COMPLY WITH THE LIMITS FOR A CLASS
B COMPUTING DEVICE IN ACCORDANCE WITH THE SPECIFICATIONS IN
SUBPART J OF PART 15 OF FCC RULES, WHICH ARE DESIGNED TO

PROVIDE REASONABLE PROTECTION AGAINST SUCH INTERFERENCE
IN A RESIDENTIAL INSTALLATION. HOWEVER, THERE IS NO GUARAN­TEE THAT INTERFERENCE WILL NOT OCCUR IN A PARTICULAR IN­STALLATION. IF THIS EQUIPMENT DOES CAUSE INTERFERENCE TO
RADIO OR TELEVISION RECEPTION, WHICH CAN BE DETERMINED BY
TURNING THE EQUIPMENT OFF AND ON, THE USER IS ENCOURAGED
TO TRY TO CORRECT THE INTERFERENCE BY ONE OR MORE OF THE

FOLLOWING MEASURES:

• REORIENT THE RECEIVING ANTENNA

• RELOCATE THE COMPUTER WITH RESPECT TO THE RECEIVER

• MOVE THE COMPUTER AWAY FROM THE RECEIVER

• PLUG THE COMPUTER INTO A DIFFERENT OUTLET SO THAT
COMPUTER AND RECEIVER ARE ON DIFFERENT BRANCH CIR­CUITS

"IF NECESSARY, THE USER SHOULD CONSULT THE DEALER OR AN

EXPERIENCED RADIO/TELEVISION TECHNICIAN FOR ADDITIONAL SUG-

GESTIONS. THE USER MAY FIND THE FOLLOWING BOOKLET PRE-

PARED BY THE FEDERAL COMMUNICATIONS COMMISSION HELPFUL:
'HOW TO IDENTIFY AND RESOLVE RADIO-TV INTERFERENCE PROB­LEMS.' THIS BOOKLET IS AVAILABLE FROM THE U.S. GOVERNMENT

PRINTING OFFICE, WASHINGTON, D.C. 20402, STOCK NO. 004-000­00345-4."

INFORMATION TO USER

"WARNING: THIS EQUIPMENT HAS BEEN CERTIFIED TO COMPLY WITH
THE LIMITS FOR A CLASS B COMPUTING DEVICE, PURSUANT TO SUB­PART J OF PART 15 OF FCC RULES. ONLY PERIPHERALS (COMPUTER
INPUT/OUTPUT DEVICES, TERMINALS, PRINTERS, ETC.) CERTIFIED TO
COMPLY WITH THE CLASS B LIMITS MAY BE ATTACHED TO THIS COM-

PUTER. OPERATION WITH NON-CERTIFIED PERIPHERALS IS LIKELY TO

RESULT IN INTERFERENCE TO RADIO AND TV RECEPTION.

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COMMO

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SE

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'S G

D

O

R

E 64

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Commodore Business Machines, Inc.

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Published

by.

First Edition

Ninth Printing - 1984

Copyright

All rights reserved.

This manual is copyrighted and contains proprietary information. No part of this publica-

tion may be reproduced

means,electronic, mechanical

written permission of COMMODORE BUSINESS MACHINES, Inc.

© 1982 by Commodore Business Machines, Inc.

,

stored in a retrieval system

,

photocopying

,

,

or transmitted in any form or by any

recording or otherwise, without the prior

TABLE OF CONTENTS

INTRODUCTION

1. SETUP

• Unpacking and Connecting the Commodore 64 .......... 2

• Installation ......................................... 3

• Optional Connections ................................ 6

• Operation .........................................

• Color Adjustment ................................... 11

2. GETTING STARTED

• Keyboard .......................................... 14

• Back to Normal .................................... 17

• Loading and Saving Programs ........................

• PRINT and Calculations .............................. 22

• Precedence 27

• Combining Things

3. BEGINNING BASIC PROGRAMMING

• The Next Ste

• Editing Tips 34

• Variables .......................

• IF ... THEN

• FOR . . . NEXT Loops ...............................

.............................................. 1

GOTO ........................................... 33

......................................... vii

.................................. 13

........................................

................................... 28

............... 31

p

........................................

................... 34

....................................... 37

8

18

32

39

4. ADVANCED BASIC

• Introduction ........................................ 42

• Simple Animation ................................... 43

Nested Loops .................................... 44

• INPUT ............................................. 45

• GET .............................................. 47

• Random Numbers and Other Functions ................. 48

• Guessing Game .................................... 50

• Your Roll .......................................... 52

.................................. 41

iii

• Random Graphics ................................... 53

CHR$ and ASC Functions .......................... 53

5. ADVANCED COLOR AND GRAPHIC COMMANDS .. 55

• Color and Graphics ................................. 56

• PRINTing Colors .................................... 56

• Color CHR$ Codes .................................. 58

• PEEKs and POKEs ................................... 60

• Screen Graphics .................................... 62

• Screen Memory Map ................................ 62

• Color Memory Map ................................. 64

• More Bouncing Balls ................................ 65

6

6. SPRITE GRAPHICS

• Introduction to Sprites ............................... 68

• Sprite Creation ..................................... 69

• Additional Notes on Sprites ........................... 75

• Binary Arithmetic ................................... 76

7. CREATING SOUND

• Using Sound if You're Not a

Computer Programmer ............................ 80

• Structure of a Sound Program ........................ 80

• Sample Sound Program .............................. 80

• Making Music on Your Commodore 64 ................. 81

• Important Sound Settings ............................ 83

• Playing a Song on the Commodore 64 ................. 88

• Creating Sound Effects .............................. 89

• Sample Sound Effects To Try ......................... 90

8. ADVANCED DATA HANDLING

• READ and DATA .................................... 92

• Averages .......................................... 94

• Subscripted Variables ............................... 95

One-Dimensional Arrays ........................... 96

Averages Revisited ................................ 97

• DIMENSION ........................................ 98

• Simulated Dice Roll With Arrays ....................... 99

• Two-Dimensional Arrays .............................. 100

.................................. 67

................................. 79

...................... 91

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APPENDICES

Introduction .......................................... 106

A: COMMODORE 64 ACCESSORIES AND SOFTWARE ....... 107

B: ADVANCED CASSETTE OPERATION .................... 110

C: COMMODORE 64 BASIC ............................ 112

D: ABBREVIATIONS FOR BASIC KEYWORDS ............... 130

E: SCREEN DISPLAY CODES ............................ 132

F: ASCII and CHR$ CODES ............................ 135

G: SCREEN AND COLOR MEMORY MAPS ................. 138

H: DERIVING MATHEMATICAL FUNCTIONS ................ 140

I: PINOUTS FOR INPUT/OUTPUT DEVICES ................ 141

J: PROGRAMS TO TRY ................................ 144

K: CONVERTING STANDARD BASIC PROGRAMS TO

COMMODORE 64 BASIC ............................ 148

L: ERROR MESSAGES ................................. 150

M: MUSIC NOTE VALUES ............................... 152

N: BIBLIOGRAPHY .................................... 156

0: SPRITE REGISTER MAP .............................. 159

P: COMMODORE 64 SOUND CONTROL SETTINGS ......... 162

........................................... 105

INDEX

................................................. 165

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INTRODUCTION

Congratulations, on your purchase of one of the best computers in the

world. You are now the proud owner of the

modore is known
being friendly is giving you easy to read, easy to use and easy to
understand instruction manuals.
designed to give you all the information you need to properly set up your

equipment, get acquainted with operating

give you a simple, fun start at learning to make

For those of you who don't want to bother learning how to program,
we've put all the information you need to use Commodore programs or
other prepackaged programs and/or game cartridges (third party

software) right up front. This means you don't have to hunt through the

entire book to get started.

Now let's look at some of the exciting features that are just waiting for
you inside your
you've got the most advanced picture maker in the microcomputer in­dustry. We call it
own pictures in 4 different colors, just like the ones you see on arcade
type video games. Not only that,

many as 8 different picture
soon be available as a software program that you can load directly into

COMMODORE

your

screen

MODORE 64

the computer to take the action you want when the sprites hit each
other.

rival many well known music synthesizers. This part of your computer
gives you 3 independent voices, each with a full 9 octave "piano-type"
range. In addition you get 4 different waveforms (sawtooth, triangle,
variable pulse, and noise), a programmable ADSR (attack, decay, sus-

tain, release

bandpass filter for the voices, and variable
trols. If you want

, even pass

even provides automatic collision detection which instructs

Next

, the COMMODORE

) envelope generator and a programmable high, low, and

as The Friendly Computer

The COMMODORE 64 USER'S GUIDE is

COMMODORE

SPRITE GRAPHICS

64. You can move

one image in

your

music to play back with professional sound re-

64. First, when it comes to graphics

, and it allows you to design your

the SPRITE EDITOR

levels at one

front of or behind another. Your COM-

64 has built-in music and sound effects that

your

COMMODORE

company, and part of

the COMMODORE 64, and

own programs.

your

let's you animate as

time. The

creations anywhere on the

resonance

SPRITE EDITOR will

and volume con-

64. Com-

vii

production,

the COMMODORE

64 allows you to connect your audio out-

put to almost any high-quality amplification system.

While we're on the subject of connecting

other pieces of equipment . . . your system can be expanded by adding
accessories, known as peripherals, as your computing needs grow.

Some of your options include items like a DATASSETTE* recorder or as
many as 5, VIC 1541 disk drive storage units for the programs you make
and/or play. If you already have a VIC 1540 disk drive your dealer can
update it for use with the
matrix printer to give you printed copies of your programs, letters, in­voices, etc. . . If you want to connect up with larger computers and their

massive data bases then just plug in a VICMODEM cartridge, and get
the services of hundreds of specialists and a variety of information net­works through your home or business telephone. Finally if you're one of
those people interested in the wide variety of applications software
available in CP/M**, the

Z-80 microprocessor.

Just as important as all the available hardware is the fact that this

'

USER

It won't tell you everything there is to know about computers, but it will
refer you to a wide variety of publications for more detailed information

about the topics presented. Commodore wants you to really enjoy your

new COMMODORE

not the kind of thing you can learn in a day. Be patient with yourself as

you go through

minutes to fill out and mail in the owner/registration card that came with

your computer. It will ensure that your

registered with Commodore Headquarters and that you receive the most
up-to-date information regarding future enhancements for your ma­chine. Welcome to a whole new world of fun!!

S GUIDE

will help you develop your understanding of computers.

64. And to have fun, remember: programming is

the USER

COMMODORE

COMMODORE

'

S GUIDE

. But before you start, take a few

the COMMODORE 64 to

64. You can add a VIC dot

64 can be fitted with a plug-in

COMMODORE

64 is properly

S

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NOTE:

Many programs are under development while this manual is being

produced. Please check with your local Commodore dealer and with
Commodore User's Magazines and Clubs, which will keep you up to
date on the wealth of applications programs being written for the
Commodore 64, worldwide.

*DATASSETTE is a registered trademark of Commodore Business Machines, Inc.

** CP/M is a registered trademark of Digital Research Inc. Specifications subject to
change.

C

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A

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R

• Unpacking' and

Commodore 64

• Installation

• Optional. Connections

• Operation

• Color

Adjustment

Connecting the

0

UNPACKING AND CONNECTING THE

COMMODORE 64

The following step-by-step instructions show you how to connect the
Commodore 64 to your television set, sound system, or monitor and
make sure everything is working properly.

Before attaching anything to the computer, check the contents of the

Commodore 64 container. Besides this manual, you should find the fol-

lowing items:

1. Commodore 64

2. Power supply (black box with

an AC

plug and supply cord)

3. Video cable

4. TV Switchbox (

If any items are missing check

a replacement.

,

First

let's take a look at the arrangement of the various connections

on the computer and how each functions.

SIDE PANEL

1. Power Socket

attached here to supply power to the Commodore 64.

2. Power Switch

3. Game Ports

controller paddle, while the lightpen can only be plugged into the
game port closest to the front of your computer.

CONNECTIONS

small silver box with short antenna leads).

back with your

. The free end of the cable from the power supply is

. Turns on power to the Commodore 64.

. Each game connector can accept a joystick or game

dealer immediately for

REAR CONNECTIONS

4. Cartridge

game cartridges.

5. Channel Selector

computer's picture will be displayed on.

6. TV Connector

your television set.

7. Audio & Video Output

can be connected to a high quality sound system, and a "compos­ite" video signal, which can be fed into a television "monitor."

8. Serial

the Commodore 64 through this connector.

Slot. The rectangular slot to the left accepts program or

. Use this switch to select which TV channel the

. This connector supplies both the picture and sound to

. This connector supplies direct audio, which

Port. You can attach a printer or single disk drive directly to

w

•

ah

•

2

GAME POWER POWER

PORTS SWITCH SOCKET

<-Ch. 3 Ch. 4->

CARTRIDGE CHANNEL TV AUDIONIDEO SERIAL CASSETTE USER

SLOT SELECTOR CONNECTOR CONNECTOR PORT INTERFACE PORT

9. Cassette Interface

. A DATASSETTE recorder can be attached to the
computer so you can save information entered for use at a later
time.

10. User

Port. Various interface cartridges can be attached to the user

port, such as the VICMODEM, or RS 232 communication cartridge.

INSTALLATION

CONNECTIONS

Connect the computer to your TV as shown on page 4.

1. Attach one end of the TV cable to the phono type TV signal jack at

the rear of the Commodore 64. Just push it in. Either end of the
cable can be used.

2. Connect the other end of the cable to the antenna switchbox. Just
push it in.

TO YOUR TV

3

Ft^a

TO

TV SIGNAL

JACK

TV

SWITCH BOX

TO 300 OHM

ANTENNA

INPUT

POWER

SUPPLY

3. If you have a VHF antenna, disconnect it from your TV set.

4. Connect your VHF antenna cable to the screw terminals labeled "an­tenna input" on the switchbox. If your antenna cable is the round

75-ohm coax type, use a 75-ohm to 300-ohm adapter (not supplied)

to attach your antenna cable to the switchbox.

5. Connect the twin lead output cable of the antenna switchbox to the
VHF antenna terminals of your TV set. If your set is one of the newer
types with a round 75-ohm VHF connector, you will need a 300-ohm
to 75-ohm converter (not supplied) to connect the switchbox to the

75-ohm VHF antenna input on the set.

6. Set the TV's VHF tuner to the channel number indicated on the com­puter's channel selector switch (channel 3 move the switch to the left,
channel 4 move the switch to the right). If a strong local TV signal is
present on one of these channels, select the other channel to avoid

possible interference.

8. Plug the power supply cable into the power socket on the side of the

Commodore 64. Just push it in. It is "keyed" to allow insertion in only
one direction, so you can't connect the power cord the wrong way.
The power supply converts household current into the form the com-

puter uses.

4

The Commodore

nections are required to use the computer
switchbox will connect the computer

the "computer

"

position.

will operate normally.

64 is now correctly connected. No additional con-

to the TV

When the switch

5

with your TV. The

when the slide switch is in

is in the

"TV" position

antenna

your set

OPTIONAL CONNECTIONS

Since the Commodore 64 furnishes a channel of high fidelity sound,

you may wish to play it through a quality amplifier to realize the best

sound possible. In addition, the Commodore 64 also provides a stan­dard "composite" video signal, which can be fed into a television

monitor.

These options are made possible by the audio/video output jack on
the rear panel of the Commodore 64. The easiest way to gain access to
these signals is by using a standard 5-Pin DIN audio cable (not

supplied). This cable connects directly to the audio/video connector on

the computer. Two of the four pins on the opposite end of the cable

contain the audio and video
own cable, using the pinouts shown in Appendix I as a guide.

signals

O

S

0

. Optionally, you can construct your

6

Normally, the BLACK connector of the DIN cable supplies the AUDIO
signal. This plug may be connected to the AUXILIARY input of an am­plifier, or the AUDIO IN connector of a monitor or other video system,
such as a video cassette recorder (VCR).

The WHITE or RED connector usually supplies the direct VIDEO signal.
This plug is connected to the VIDEO IN connector of the monitor or video
input section of some other video system, such as a VCR.

Depending on the manufacturer of your DIN cable, the color coding
of the plugs may be different. Use the pinouts shown in Appendix I to
match up the proper plugs if you don't get an audio or video signal
using the suggested connections.

AUDIOIVIEO

OUTPU

T

4

TO AUXILIARY

INPUT OR

TUNER INPUT TO VIDEO IN

I

TV MONITOR

AUDIO SYSTEM

If you purchased peripheral equipment, such as a VIC 1541 disk drive
or a VIC 1515 printer, you may wish to connect it at this time. Refer to
the user's manuals supplied with any additional equipment for the
proper procedure for connecting it to the computer.

6

a

J

7

A completed system might look like this.

Aft

•

OPERATION

USING THE COMMODORE 64

1. Turn on the computer using the rocker
when you

2. After a few moments the following will be displayed on the TV
screen:

E41 RAM 'SYSTEM 3

READY

■

--

'

re looking at the computer from

+*+ i_ C rir1C ODC'RE 64 E:A ; I C: 2 +*++

A .IC E

?-'911 E

,'

:

switch

on the right

the front.

•"iTE'=• FREE

CURSOR SIGNALS

COMMODORE 64 IS

WAITING FOR YOUR

INPUT.

-

side panel

•

8

9

3. If your TV has a manual fine tuning knob, adjust the TV until you get
a clear picture.

4. You may also want to adjust the color and tint controls on the TV for

the best display. You can use the color adjustment procedure de­scribed later to get everything setup properly. When you first get a

picture, the screen should appear mostly

dark blue, with a light

blue border and letters.

If you don't get the expected results, recheck the cables and connec-

tions. The accompanying chart will help you isolate any problem.

TROUBLESHOOTING CHART

Symptom Cause

Indicator Light
not "On"

Computer not

Power cable Check power socket

not plugged for loose or dis-

in connected power

Power supply Check connection
not plugged with wall outlet

in

Bad fuse in Take system to

computer authorized dealer

TV on wrong Check other

channel channel for

Incorrect

hookup VHF

Remedy

Make sure power
switch is in "On"
position

cable.

for replacement of
fuse

picture (3 or 4)

Computer hooks up to

antenna terminals

Video cable Check TV output
not plugged cable connection

in

Computer set Set computer for
for wrong some channel as TV
channel (3 or 4)

9

Symptom

Cause

Remedy

Random pattern
on TV with

cartridge in

place

Picture without

color

Picture with
poor color

Sound with

excess

background
noise

Picture OK,

but no sound

Cartridge not
properly

inserted

Poorly tuned

TV

Bad color
adjustment
on TV

TV volume up

high

TV volume too

low

Aux. output

not properly

connected

Reinsert
cartridge after

turning off power

Retune TV

Adjust color/
hue/brightness
controls on TV

Adjust volume of

TV

Adjust volume of

TV

Connect sound
jack to aux. input

on amplifier and
select aux. input

TIP: The

But we at Commodore recognize that computer users may, occasionally, run into

difficulties. To help answer your questions and give you some fun programming

ideas, Commodore has created several publications to help you. You might also find

that it's a good idea to join a Commodore Users Club to help you meet some other

COMMODORE

COMMODORE

64 owners who can help you gain knowledge and experience.

64 was designed to be used by everyone.

CURSOR

The flashing square under READY is called the cursor and indicates
where what you type on the keyboard will be displayed on the screen.
As you type, the cursor will move ahead one space, as the original

cursor position is replaced with the character you typed. Try typing on

the keyboard and watch as characters you type are displayed on the TV

screen.

10

COLOR ADJUSTMENT

There is a simple way to get a pattern of colors on the TV so you can

.

easily adjust the set
operation of the computer right now

how easy it is to use the Commodore 64.

First, look on the left side of the keyboard and locate the key marked

M. This stands for ConTRoL and is used, in conjunction with other

keys, to instruct the computer to do a specific task.

•LK tMIn s>NI CYM PUR No ILU

s .^... 8 • W E

Even though

you may not be familiar with the

just follow along, and you'll see

,

a 15

.

: R . 'r . Y- U I C3

YEt . o«

RUN

soP aeaR

OP

8T

Cc a1N

A 8 C3 F C3 H J K

T z

/P

Mai P_'3a Q

B

x

C

E4 P3

- V

8 sit 1

-

N M

1;- rTfi:

To use a control function, you hold down the= key while depress-

ing a second key.

Try this: hold the= key while also depressing

theakey

lease both keys. Nothing obvious should have happened, but if you
touch any key now, the screen will show the character displayed in re­verse type, rather than normal type-like the opening message or any­thing you typed

earlier.

Hold down the . What happens? If you did the above pro-

cedure correctly, you should see a light blue bar move across the screen

. Then re-

11

and then move down to the next line as long as the

SPACE BAR

pressed.

*++* COMMODORE 64 BASIC V2 *+**

64K RAM SYSTEM 3

E911 E:A

SIC BYTES

FREE

READY

Now, hold =while depressing any of the other number keys. Each

of them has a color marked on the front. Anything displayed from this
point will be in that color. For example, hold M and thefkey and

is de-

release

change the bar to any of the other colors indicated on the number keys
by holding • and the appropriate key.

color and tint controls on your TV so the display matches the colors you
selected.

both. Now hold the

Watch the display. The bar is now in yellow! In a like manner you can

Change the bar to a few more different colors and then adjust the

The display should appear something like this:

**** COFIMCODORE 64 BASIC Y2 *+**

64K RAM SYSTEM

READY

SPACE BAR

3

8911 BASIC BYTES FREE

WORED BAR

O GREEN BAR

O BLUE BAR

p YELLOW BAR

At this point everything is properly adjusted and working correctly.
The following chapters will introduce you to the BASIC language. How­ever, you can immediately start using some of the many prewritten ap-

plications and games available for the Commodore 64 without knowing

anything about computer programming.

Each of these packages contains detailed information about how to

use the program. It is suggested, though, that you read through the first
few chapters of this manual to become more familiar with the basic
operation of your new system.

12

CHAPTER

GETTING STARTED

• Keyboard

• Back to Normal

• Loading and Saving Programs

• PRINT and Calculations

• Precedence

• Combining Things

m

KEYBOARD

Now that you
few moments to familiarize yourself with the keyboard which is your
most important means of communication with the Commodore 64.

You will find the

found in most areas
control specialized functions
various keys and how they function.The detailed operation of each key
will be covered in later sections.

'

ve got everything set up and adjusted, please take a

keyboard similar to a standard typewriter

.

There are,however

. What

,

a number of new keys which

follows is a brief description of the

keyboard

RETURN

The key signals the computer to look at the information that

you typed and enters that information into memory.

SHIFT

The ® key works like that on a standard typewriter. Many keys
are capable of displaying two letters or symbols and two graphic char­acters. In the "upper/lower case" mode the ® key gives you stan­dard upper case characters. In the "upper case/graphic" mode the

® key will display the graphic character on the right hand side of

the front part of the key.

In the case of special YELLOW function keys, the ® key will give

you the function marked on the front of the key.

14

•

EDITING

No one is perfect, and the Commodore 64 takes that into account. A
number of editing keys let you correct typing mistakes and move infor­mation around on the screen.

CRSR

There are two keys marked IM (CuRSoR), one with up and down

arrows

ffl=

the other with left and right arrows ^ . You can
use these keys to move the cursor up and down or left and right. In the
unshifted mode, the keys will let you move the cursor down and to

the right. Using the key and keys allows the cursor to be

moved either up or to the left. The cursor keys have a special repeat

feature that keeps the cursor moving until you release the key.

INST/DEL

If you hit the key, the cursor will move back a space, eras­ing (DELeting) the previous character you typed. If you're in the middle
of a line, the character to the left is deleted and the characters to the
right automatically move together to close up the space.

A ®ed ®i allows you to INSerT information on a

example, if you noticed a typing mistake in the beginning of

perhaps you left out part of a name-you could use the

=CRSR

move back to the error and then hit ®i to insert a

just type in the missing letter.

CLR/HOME

CLR/HOME

positions the cursor at the "HOME" position of the screen,

which is the upper left-hand corner. A shifted will clear the

screen and place the cursor in the home position.

line. For

a line-

key to

space. Then

^^IIt

operates as the name implies. It restores the computer to the
normal state it was in before you changed things with a program or
some command. A lot more will be said on this in later chapters.

15

FUNCTION KEYS

The four function keys on the right side of the keyboard can be "pro-

grammed" to handle a variety of functions. They can be defined in

many ways to handle repetitive tasks.

CTRL

TheMkey, which stands for ConTRoL, allows you to set colors, and

perform other specialized functions. You hold the =key down while
depressing another designated key to get a control function. You had an
opportunity to try the= key when you changed text colors to create

different color bars during the setup procedure.

RUN/STOP

Normally, depressing the key will stop the execution of a

BASIC program. It signals the computer to STOP doing something. Using

16

l

the key in the shifted mode will allow you to automatically

load a program from tape.

® COMMODORE KEY

The Commodore key ® performs a number of functions. First, it

allows you to move between the text and graphic display modes.

When the computer is first turned on, it is in the Upper Case/Graphic

mode, that is, everything you type is in upper case letters. As was men-

tioned, using the ® key in this mode will display the graphic on the

right side of the keys.

If you hold down the ® key and ® key, the display will change

to upper and lower case. Now, if you hold down the ® key and any

other key with a graphic symbol, the graphic shown on the left side of

the key will be displayed.

To get bock into the upper case/graphic mode hold down the ® key

and ® key again.

The second function of the ® key is to allow you access to a second
set of eight text colors. By holding down the ® key and any of the
number keys, any text now typed will be in the alternate color available

from the key you depressed. Chapter 5 lists the text colors available
from each key.

BACK TO NORMAL

Now that you've had a chance to look over the keyboard, let's explore

some of the Commodore 64's many capabilities.

If you still have the color bars on the screen from adjusting your TV
set, hold ® and . The screen should clear and the cursor
will be positioned in the "home" spot (upper left-hand corner of the
screen).

Now, simultaneously hold ® and the o key. This sets the text color

back to light blue. There is one more step needed to get everything back
to normal. Hold M and
back to normal. If you remember, we turned REVERSE type on with the

MQ to create

spaces). If we were in the normal text mode during the color test, the
cursor would have moved, but just left blank spaces.

a (Zero not

the color bars (the color bars were actually reversed

Oh!). This sets the display mode

17

TIP:

Now that you've done things the hard way, there is a simple way to reset the
machine to the normal display. First press the key and then press
the

JIM

This will clear the screen and return everything to normal. If there is a program in

the computer, it will be left untouched. This is a good sequence to remember, espe­cially if you do a lot of programming.

If you wish to reset the machine as if it were turned off and then switched on
again, type, SYS64759 and press I=.. Be careful using this command! It will

wipe out any program or information that is currently in the computer.

key. must always be held down in order to use the

key function.

LOADING AND SAVING PROGRAMS

One of the most important features of the Commodore 64 is the ability

to save and load programs to and from cassette tape or disk.

This capability allows you to save the programs you write for use at a

later time, or purchase prewritten programs to use with the Commodore

64.
Make sure that either the disk drive or datasette unit is attached

properly.

LOADING PREPACKAGED PROGRAMS

For those of you interested in using only prepackaged programs

available on cartridges, cassette, or disk here's all you have to do:

1. CARTRIDGES

and games on cartridge. The programs offer a wide variety of business
and personal applications and the games are just like real arcade
games-not imitations. To load these games, first turn on your TV set.
Next turn OFF

MODORE 64 BEFORE INSERTING OR REMOVING CARTRIDGES OR YOU
MAY DAMAGE THE CARTRIDGE AND/OR YOUR COMMODORE 64!

Third insert the cartridge. Now turn your Commodore 64 on. Finally type
the appropriate START key as is listed on the instruction sheet that comes
with each game.

2. CASSETTES

: The Commodore 64 computer has a line of programs

your

Commodore 64. YOU

MUST TURN OFF YOUR COM-

: Use your DATASSETTE recorder and the ordinary audio cas-

18

0

settes that came as part of your prepackaged program. Make sure
the tape is completely rewound to the beginning of the first side.
Then, just type LOAD. The computer will answer with PRESS PLAY ON
TAPE, so you respond by pressing play on your datasette machine. At
this point the computer screen will go blank until the program is
found. The computer will say FOUND (PROGRAM NAME) on the
screen. Now you press down on the ® KEY. This will actually
load the program into the computer. If you want to stop the loading
simply press the key.

3. DISK

: Using your disk drive, carefully insert the preprogrammed disk
so that the label on the disk is facing up and is closest to you. Look
for a little notch on the disk (it might be covered with a little piece of
tape). If you're inserting the disk properly the notch will be on the left
side. Once the disk is inside close the protective gate by pushing down
on the lever. Now type LOAD "PROGRAM NAME", 8 and hit the

^^IIIID

key. The disk will make

noise

and your screen will say:

SEARCHING FOR PROGRAM NAME
LOADING

READY

I

When the READY comes on and the 0 is on, just type RUN, and

your prepackaged software is ready to use.

LOADING PROGRAMS FROM TAPE

Loading a program back from tape or disk is just as simple. For tape,

rewind the tape back to the beginning and type:

LOAD"PROGRAM NAME"

If you don't remember the program name, just type LOAD and the

first program on the tape will be loaded into memory.

After you press i the computer will respond with:

19

PRESS PLAY ON TAPE

After you depress the play key, the screen will blank, turning the

s

®

1^

11

border color of the

screen as

the computer

searches

for the program.

When the program is found, the screen will display:

FOUND

To actually LOAD the program, depress the
LOADing procedure, hit ^ . If you hit the Commodore key, the
screen will again turn the border color while the program is LOADed.

After the LOADing procedure is completed, the screen will return to the

normal state and the READY prompt will reappear.

LOADING PROGRAMS FROM DISK

Loading a program from disk follows the same format. Type:

PROGRAM NAME

®

key. To abandon the

I

I

I

II

4

LORD

The 8 is the code for the disk, so you're just letting the computer know

that you want the program loaded from the disk.

After you hit

shows:

SEARCHING FOR PROGRAM NAME

LOADING

READY

I

PROGRAM NAME",8

"

the disk will start whirring and the display

20

II h

NOTE:

When you load a new program into the computer's memory, any in-

structions that were in the computer previously will be erased. Make

sure you save a program you're working on before loading a new one.

Once a program has been loaded, you can RUN it, LIST it, or make
changes and re-save the new version.

SAVING PROGRAMS ON TAPE

After entering a program, if you wish to save it on tape, type:

SAVE "PROGRAM NAME"

"PROGRAM NAME" can be up to 16 characters long. After you hit

the computer will respond with:

PRESS PLAY AND RECORD ON TAPE

Press both the record and play keys on the datasette. The screen will

blank, turning the color of the border.

After the program is saved on tape, the READY prompt will reappear,

indicating that you can start working on another program, or just turn

off the computer for a while.

SAVING PROGRAMS ON DISK

Saving a program on disk is even simpler. Type:

SAVE "PROGRAM NAME"

,

21

The 8 is the code for the disk, so you're just letting the computer know

you want the program saved to disk.

After you press ^ the disk will start to turn and the computer

will respond with:

SAVIt-IG "PROGRA11 NAME"

READY

0

PRINT

Now that you've gotten through

tions you need in order to

some programs

Try typing the following exactly

AND CALCULATIONS

keep the programs

for you to save.

PR I tIT "C:OMMO ADORE. 64"

CCiPINFOO 'E h4

a couple

as shown:

of the

TYPE THIS

more

you like, lets start making

LINE AND

HIT

READY

■

If you make a typing mistake, use the ®i key to erase the char­acter immediately to the left of the cursor. You can delete as many
characters as necessary.

Let's see what went on in the example above. First, you instructed
(commanded) the computer to PRINT whatever was inside the quote

marks. By hitting ^ you told the computer to do what you in-

structed and COMMODORE 64 was printed on the screen.

When you use the PRINT statement in this form, whatever is enclosed

in quotes is

If the computer responded with:

printed exactly as you typed it.

COMPUTER TYPED

difficult opera-

?SYNTAX ERROR

ask yourself if you made a mistake in typing, or forgot the quote marks.

22

40

The computer is precise and expects instructions to be given in a specific
form.

But don't get worried; just remember to enter things as we present
them in the examples and you'll get along great with the Commo­dore 64.

Remember, you can't hurt the computer by typing on it, and the best
way to learn BASIC is to try different things and see what happens.

PRINT is one of the most useful and powerful commands in the BASIC

language. With it, you can display just about anything you wish, includ­ing graphics and results of computations.

For example, try the following. Clear the screen by holding down the

® key and key and type (be sure to use the '1' key for

one, not a letter 'I'):

PRINT 12 +

TYPE THIS LINE AND

HIT

Aphu

COMPUTER PRINTED

THE ANSWER ,

What you've discovered is that the Commodore 64 is a calculator in its
basic form. The result of "24" was calculated and printed automatically.
In fact, you can also perform subtraction, multiplication, division, ex­ponentiation, and advanced math functions such as calculating square
roots, etc. And you're not limited to a single calculation on a line, but

more on that later.

Note that in the above form, PRINT behaved differently from the first

example. In this case, a value or result of a calculation is printed, rather than
the exact message you entered because the quote marks were omitted.

ADDITION

The plus sign (+) signals addition: we instructed the computer to print
the result of 12 added to 12. Other arithmetic operations take a similar
form to addition. Remember to always hit after typing PRINT

and the calculation.

23

SUBTRACTION

To subtract, use the conventional minus (-) sign. Type:

MULTIPLICATION

ii

If you wanted to multiply 12 times 12, use the asterisk (*) to represent

multiplication. You would type:

DIVISION

Division uses

the familiar

"/". For example

, to divide 144 by 12, type:

•1

24

0

EXPONENTIATION

In a like fashion, you can easily raise a number to a power (this is the

same as multiplying a number by itself a specified number of times).

The 'T' (Up arrow) signifies exponentiation.

PRINT 12 ' 5
248832

This is the same as typing:

PRINT 12 * 12 * 12 * 12 * 12

248832

TIP:

BASIC has a number of shortcut ways of doing things. One such way is abbreviat­ing BASIC commands (or keywords). A ? can be used in place of PRINT, for exam­ple. As we go on you'll be presented with many commands; Appendix D shows the

abbreviations for each and what will be displayed on the screen when you type the
abbreviated form.

The last example brings up another important point: many calcula­tions may be performed on the same line, and they can be of mixed
types.

You could calculate this problem:

25

Up to this point we've just used small numbers and simple examples.

However, the Commodore 64 is capable of more complex calculations.

You could, for example, add a number of large figures together. Try

this, but don't use any commas, or you'll get an error:

: 123.45 + 345.

'1

78 + 7895.687

8364.917

That looks fine, but now try this:

12123123.45 + 345.78 + 7895.687

12131364.9

If you took the time to add this up by hand, you would get a different

result.

What's going on here? Even though the computer has a lot of power,
there's a limit to the numbers it can handle. The Commodore 64 can
work with numbers containing 10 digits. However when a number is

printed, only nine digits are displayed.

So in our example, the result was "rounded" to fit in the proper

range. The Commodore 64 rounds up when the next digit is five or more;
it rounds down when the next digit is four or less.

Numbers between 0.01 and 999,999,999 are printed using standard

notation. Numbers outside this range are printed using scientific nota-

tion.

Scientific notation is just a process of expressing a very large or small

number as a power of 10.

If you type:

12300

1.23E+17

0000

000000000

26

w

This is the same as 1.23 * 10T17 and is used just to keep things tidy.
There is a limit to the numbers the computer can handle, even in

scientific notation. These limits are:

Largest: ±- 1.70141183E+38

Smallest (different from zero): ± 2.93873588-39

PRECEDENCE

If you tried to perform some mixed calculations different from the
examples we showed earlier, you might not have gotten the results that
you expected. The reason is that the computer performs calculations in a
certain order.

In this calculation:

20 + 8/2

you can't tell whether the answer should be 24 or 14 until you know in
which order to perform the calculations. If you add 20 to 8 divided by 2

(or 4), then the result is 24. But, if you add 20 plus 8 and then divide by
2 the answer is 14. Try the example and see what result you get.

The reason you got 24 is because the Commodore 64 performs calcu-

lations left to right according to the following:
First: - minus sign indicating negative numbers

Second: T exponentiation, left to right
Third: multiplication and divisions, left to right

Fourth: +- addition and subtraction, left to right

Follow along according to the order of precedence, and you will see
that in the above example the division was performed first and then the
addition to get a result of 24.

Make up some problems of your own and see if you can follow along

and predict the results according to the rules set down above.

There's also an easy way to alter the precedence process by using

parentheses to set off which operations you want performed first.

For example, if you want to divide 35 by 5-plus-2 you type:

27

you will get 35 divided by 5 with 2 added to the answer, which is not
what you intended at all. To get what you really wanted, try this:

2 35 / (5 + 2)

5

What happens now is that the computer evaluates what is contained
in the parentheses first. If there are parentheses within parentheses, the
innermost parentheses are evaluated first.

Where there are a number of parentheses on a line, such as:

7 (1

+ 9) * (6 + 1)

21

147

the computer evaluates them left to right. Here 21 would be multiplied
by 7 for the result of 147.

COMBINING THINGS

Even though we've spent a lot of time in areas that might not seem
very important, the details presented here will make more sense once
you start to program, and will prove invaluable.

To give you an idea how things fit in place, consider the following:
how could you combine the two types of print statements we've exam­ined so far to print something more meaningful on the screen?

We know that by enclosing something within quote marks prints that
information on the screen exactly as it was entered, and by using moth
operators, calculations can be performed. So why not combine the two

types of PRINT statements like this:

Ah

"

5

*

9

5 * 9

= 4

= ' 5
5

SEMICOLON MEANS NO SPACE.

*

9

28

Even thcugh this might seem a bit redundant, what we've done is
simply use both types of print statements together. The first part prints
"5 * 9 =" exactly as it was typed. The second part does the actual work
and prints the result, with the semicolon separating the message part of
the statement from the actual calculation.

You can separate the parts of a mixed print statement with punctua-

tion for various formats. Try a comma in place of the semicolon and see
what happens.

For the curious, the semicolon causes the next part of the statement to

be printed immediately after the previous part, without any spaces. The
comma does something different. Even though it is an acceptable
separator, it spaces things out more. If you type:

the numbers will be printed across the screen and down on to the next

line.

The Commodore 64's display is organized into 4 areas of 10 columns

each. The comma tabs each result into the next available area. Since

we asked for more information to be printed than would fit on one line,

(we tried to fit five 10-column areas on one line) the last item was moved

down to the next line.

The basic difference between the comma and semicolon in formatting

PRINT statements can be used to our advantage when creating more

complex displays: it will allow us to create some sophisticated results
very easily.

29

CHAPTE

BEGINNING

PROGRAMMING

• The Next Step

-GOT4

• Editing Tips"

• Variables

• IF . . . THEN

• FOR . . . NEXT Loops

R

BASIC

m

THE NEXT STEP

Up to now we've performed some simple operations by entering a
single line of instructions into the computer. Once ^ was de­pressed, the operation that we specified was performed immediately.

This is called the IMMEDIATE or CALCULATOR mode.

But to accomplish anything significant, we must be able to have the
computer operate with more than a single line statement. A number of
statements combined together is called a PROGRAM and allows you to
use the full power of the Commodore 64.

To see how easy it is to write your first Commodcre 64 program, try

this:
Clear the screen by holding the ® key, and then depressing the

CLR'HOME

Type NEW and press . (This just clears out any numbers that
might have been left in the computer from your experimenting.)
Now type the following exactly as shown (Remember to hit '
after each line)

key.

0
40

•

10 ?"C0Mt`lCIDCIRE 64"

GUTU

20

Now, type RUN and hit -watch what happens. Your screen

will come alive

the display, hit

A number of important concepts were introduced in this short pro-

gram that are the basis for all programming.

Notice that here we preceded each statement with a number. This
LINE number tells the computer in what order to work with each state­ment. These numbers are also a reference point, in case the program
needs to get back to a particular line. Line numbers can be any whole
number (integer) value between 0-63,999.

10 PRINT "COMMODORE 64"

1

0

with COMMODORE 64. After you'

IJUM1 E

STATEMENT

LINE NUMBER

to stop the program.

ve finished

I

I

I

watching

32

COMMODORE 64
COMMODORE 64
COMMODORE 64
COMMODORE 64
COMMODORE 64
COMMODORE 64
COMMODORE 64
COMMODORE 14
COMMODORE 64
COMMODORE 64
COMMODORE 64

COMMODORE 64
BREAK IN 10
READY

■

It is good programming practice to number lines in increments of

10-in case you need to insert some statements later on.

Besides PRINT

GOTO.

This instructs the computer to go directly to a particular line and

,

our program also used another BASIC command,

perform it,then continue from that point.

-+ 10 PRINT "COMMODORE 64"

20 GOTO 10

In our example, the program prints the message in line 10, goes to

the next line (20), which instructs it to go back to line 10 and print the

message over again. Then the cycle repeats. Since we didn't give the
computer a way out of this loop, the program will cycle endlessly, until

we physically stop it with the key.

Once you've stopped the program, type: LIST. Your program will be

displayed, intact, because it's still in the computer's memory. Notice,

too, that the computer converted the ? into PRINT for you. The program

can now be changed, saved, or run again.

Another important difference between typing something in the im­mediate mode and writing a program is that once you execute and
clear the screen of an immediate statement, it's lost. However, you can
always get a program back by just typing LIST.

By the way, when it comes to abbreviations don't forget that the
computer may run out of space on a line if you use too many.

33

EDITING TIPS

If you make a mistake on a line, you have a number of editing

options.

1. You can retype a line anytime

and the computer will automatically

,

substitute the new line for the old one.

2. An unwanted line can be erased by simply typing the line number

and

3. You

can also easily edit an existing line, using the

cursor keys and

editing keys.

Suppose you made a typing mistake in a line of the example. To

correct it without retyping the entire line

Type LIST,

cursor up until it is positioned on the line that needs to be changed.

Now, use the cursor

want to change

t»M

If you need more space on the line, position the cursor where the
space is needed and hit ® and 1=111 at the same time and a
space will open up. Now just type in the additional information and hit

s

cursor to the right of the unwanted character and hitting the

key.

To verify that changes were entered
rected program will be displayed! And lines don
numerical order
proper sequence.

Try editing our sample program on page 33 by changing line 10 and
adding a comma to the end of the line. Then RUN the program again.

then using the ® and I keys together move the

-

right key to move the cursor to the character you

typing the change over the old character

,

and the corrected line will replace the old one.

. Likewise

,

you can delete unwanted characters by placing the

.

The computer will automatically place them in the

, try this:

.

Now hit

IN*

,

type LIST again,and the cor-

'

t have to be entered in

111

10 PRINT

"COMMODORE",

VARIABLES

Variables are some of the most used features of any programming
language, because variables can represent much more information in

the computer. Understanding how variables operate will make comput-

ing easier

otherwise.

and allow us to accomplish feats that would not be possible

34

DON'T FORGET TO MOVE THE
CURSOR PAST

YOU RUN THE PROGRAM.

LINE 20 BEFORE

S

e

C^ t1MC ADORE

G IMMClDORE
COMMODORE
COMMODORE

COMMODORE

COMMODORE

COMMODORE

COMMODORE

COMMODORE COMMODORE COMMODORE COMMODORE
COMMODORE

COMMODORE

COMMODORE

COMMODORE

BREAK: IN 10

READY

Imagine a number of boxes within the computer that can each hold a

number or a string of text characters. Each of these boxes is to be
labeled with a name that we choose. That name is called a variable
and represents the information in the respective box.

For example, if we say:

COMMODORE

COMMODORE

COMMODORE
COMMODORE
COMMODORE COMMODORE
COMMODORE COMMODORE
COMMODORE

COMMODORE

COMMODORE
COMMODORE

COMMODORE
COMMODORE

COMMODORE
COMMODORE
COMMODORE

COMMODORE

COMMODORE

COMMODORE

COMMODORE
COMMODORE COMMODORE
COMMODORE COMMODORE

COMMODORE

COMMODORE

COMMODORE

COMMODORE

COMMODORE

COMMODORE

COMMODORE
COMMODORE
COMMODORE

COMMODORE

COMMODORE

10 X% = 15

20 X = 23.5
30 X$ _ "THE SUM OF X%+X

The computer might represent the variables like this:

X% 15

X 23.5

X$ THE SUM OF X%+X =

A variable name represents the box, or memory location, where the
current value of the variable is stored. As you can see, we can assign
either an integer number, floating point number, or a text string to a
variable.

The % symbol following a variable name indicates the variable will

represent an integer number. The following are valid integer variable
names:

35

A%

X%

A1%

NM%

The '$' following the variable name indicates the variable will repre-

sent a text string

.

The following are examples of string variables:

A$
X$

Ml$

Floating point variables follow the some format

, with the type indi-

cator:

Al
X

Y

MI

In assigning a name to a variable there are a few things to keep in
mind. First, a variable name can have one or two characters. The first
character must be an alphabetic character from A to Z; the second

character can be either alphabetic or numeric (in the range 0 to 9). A
third character can be included to indicate the type of variable (integer
or text string), % or $.

You can use variable names having more than two alphabetic
characters,but only the first two are recognized by the computer. So

PA and PARTNO are the same and would refer to the some variable
box.

The last rule for variable names is simple: they can't contain any

BASIC keywords (reserved words) such as GOTO, RUN, etc. Refer back

to Appendix D for a complete list of BASIC reserved words.

To see how variables can be put to work, type in the complete pro­gram that we introduced earlier and RUN it. Remember to hit
after each line in the program.

^tID

NEW

= 23.

15

"

5

THE

"X!

X$;

10

:•: =

2

0

X

30X$ =

PRINT

40

50

PRINT

OF X% + X =

SUM

= " . Xi:, "X =

X% + X

. X

36

If you did everything as shown, you should get the following result

printed on the screen.

RUN

X% =

15

THE SUM OF

X

Xj

=

.5

23

+ X = 38.5

READY

We've put together all the tricks learned so far to format the display

as you see

it and print the sum of the two variables.

In lines 10 and 20 we assigned an integer value to X% and assigned a

floating point value to X. This puts the number associated with the vari­able in its box. In line 30, we assigned a text string to X$. Line 40
combines the two types of PRINT statements to print a message and the
actual value of X% and X. Line 50 prints the text string assigned to X$
and the sum of X% and X.

Note that even though X is used as part of each variable name, the
identifiers % and $ make X%, X, and X$ unique, thus representing
three distinct variables.

But variables are much more powerful. If you change their value, the

new value replaces the original

value

in the same box. This allows you

to write a statement like:

X = X + 1

This would never be accepted in normal algebra, but is one of the
most used concepts in programming. It means: take the current value of
X, add one to it and place the new sum into the box representing X.

IF ... THEN

Armed with the ability to easily update the value of variables, we can

now try a program such as:

37

NEW

1

^

0CT=0

20 ?"COMMODORE 64"

:30 CT = CT + 1

40 IF CT

50 END

RUN
COMMODORE 64
COMMODORE 64
COMMODORE 64
COMMODORE 64
COMMODORE 64

What we've done is introduce two new BASIC commands, and pro-

vided some control over our runaway little print program introduced at
the start of this chapter.

IF . . . THEN adds some logic to the program. It says IF a condition

holds true THEN do something. IF the condition no longer holds true,

THEN do the next line in the program.

A number of conditions can be set up in using an IF . . . THEN state-

ment:

c_ 5 THEN 20

SYMBOL MEANING

< Less Than
> Greater Than

<>

< = Less Than

The use of any one of these

powerful.

10 CT = 0
20 ?"COMMODORE 64"
30 CT = CT + 1
40 IF CT < 5 THEN 20

I

50 END

Equal To
Not Equal To

Greater Than or Equal

or Equal To

conditions

38

is simple

To

, yet surprisingly

In the sample program
straints placed on it by saying: IF a value is less than some number
THEN do something.

Line 10 sets CT
adds one to the variable CT. This line counts how many times we do the

loop. Each time the loop is executed

Line 40 is our control line. If CT is less than 5
cuted the loop less than 5 times, the program goes back to line 20 and

prints again

64's were printed
the program.

Try the program and see what we mean

line 40 you can have any number of lines printed.

IF . . . THEN has a multitude of other uses

examples.

(

CounT

.

When CT becomes equal to 5

-

,

we've set up a

)

equal to 0. Line 20 prints our message

,

the program goes to line 50

"

loop" that has some con-

CT goes up by one.

meaning we

,

indicating 5 COMMODORE

­,

which signals to END

By changing the CT limit in

.

,

which we'll see in future

.

'

ve exe-

FOR ... NEXT LOOPS

Line 30

There is a simpler

the previous example by using a FOR

, and preferred way to accomplish what we did in

. . . NEXT loop. Consider the

following:

am

113 FOR C. T = 1 TO 5

20 PRINT "COMMODORE 64"

:11

0 NEXJ CT

RIIN

COMMODORE 64
COMMODORE 64

CCIMI.ICICIC IRE 64
COMMODORE 64

I_ CIpIMC ID0F'E 64

As you can see, the program has become much smaller and more

direct.

,

CT starts at 1 in line 10. Then

line 20 does some printing

In Line 30

.

39

CT is incremented by 1. The NEXT statement in line 30 automatically
sends the program back to line 10 where the FOR part of the FOR .. .
NEXT statement is located. This process will continue until CT reaches the

limit you entered.

The variable used in a FOR . . . NEXT loop can be incremented by

smaller amounts than 1, if needed.

Try this:

NEW

10 FOR NB = 1 TO 10 STEP .5

20 PRINT NB,

30 NEXT NB

RUN

1

3
5
7

9

1.5

3.5

5.5

7.5

9.5

2

4
6

10

2.5

4.5

6.5

8.5

If you enter and run this program, you'll see the numbers from 1 to

10, by .5, printed across the display.

All we're doing here is printing the values that NB assumes as it goes

through the loop.

You can even specify whether the variable is increasing or decreas-

ing. Substitute the following for line 10:

10 FOR NB

and watch the opposite occur,
order.

= 10 to 1 STEP -.5

as NB goes

40

from 10 to 1 in descending

S

0

•

S

•

G

HAP

7E

l

t

ADVANCED BASIC

• Introduction

• Simple Animation

-Nested Loops

• INPUT

• GET

• Random Numbers and Other Functions

• Guessing Game

• Your Roll

• Random Graphics

-CHR$ and ASC Functions

m

INTRODUCTION

The next few chapters have been written for people who have be­come relatively familiar with
concepts

For those

may find
completely

SPRITE GRAPHICS and CREATING SOUND

examples that

a good
capabilities available

If you decide that you want

BASIC,

ual.

If you

will help you

es. More detailed information can befound

PROGRAMMER

Commodore

necessary to write

of you who

some

. But take heart. . . because

idea of how to

we've put a

are already

of the

are written for the new user. The examples will give you

on your COMMODORE 64.

bibliography (Appendix

familiar with BASIC

get started with advanced

'

S REFERENCE MANUAL, available through

dealer.

the BASIC

more

are just starting to learn how to program, you

information a bit too technical to understand

use the sophisticated sound and graphics

to learn more

programming language and the

advanced

programs.

for these two fun chapters,

,

we've set up some simple

about writing

N) in the back of this man-

programming,these chapters

BASIC

programming

in the COMMODORE 64

programs in

techniqu-

your local

4

2

SIMPLE

ANIMATION

Let's exercise some of the Commodore 64's graphic capabilities by

putting together what we've seen so far, together with a few new con-

cepts. If you're ambitious, type in the following program and see what

happens. You will notice that within the print statements we can also
include cursor controls and screen commands. When you see something

like {CRSR LEFT} in a program listing, hold the ® key and hit the
CRSR LEFT/ RIGHT key. The screen will show the graphic representation
of a cursor left (two vertical reversed bars). In the same way, pressing

® and shows as a reversed heart.

NEW

10 REM BOUNCING BALL

20 PRINT
25 FOR

30 FOR

40 PRINT"

50 FOR TM

"{CLR/HOME}
X = 1 TO
BL = 1 TO 40

•{CRSR LEFT)";:

&

TO 5

10 : PRINT "{CRSR/DOWN

REM (• is a SHIFT-Q)

}":

NEXT

60 NEXT TM
70 NEXT BL

75 REM MOVE
80 FOR BL

90 PRINT" {CRSR

B1' RIGHT TO LEFT

,;-,-

40 TO

1 STEP -1

LEFT}{

CRSR LEFT

}•{

CRSR

LEFT)";

100 FOR TM = 1 TO 5
110 NEXT TM
120 NEXT BL
130 GOTO 20

TIP:

All words in this text will be completed on one line. However, as long as you don't

hit

word.

your 64 will automatically move to the

The program will display a bouncing ball moving from left to right,

and back again, across the screen.

If we look at the program closely, (shown on page 44) you can see

how this feat was accomplished.

Line 10 is a REMark that just tells what the program does; it has no

43

next line even

in the middle of a

10 REM BOUNCING BALL

-20 PRINT "{CLR/HOME}"

25 FOR X = 1 TO 10 : PRINT "{CRSR/DUWN}": NEXT
30 FOR BL = i TO 40

40 PRINT" •{CRSR LEFT} ";:R.EM (• is a SHIFT-Q)
50 FOR TM = 1 TO 5

60

70

75

80

90

E100 1 TO5

XT TM

NE

NEXT

REM

FOR

PRINT

BL

MOVE BALL RIGHT TO LEFT

BL

=

40 TO 1 STEP -1

" {

CRSR LEFT}{CRSR LEFT

T M

}•{

CRSR LEFT)";

110 NEXT TM
120 NEXT BL

- 130 GGT0 20

effect on the program itself. Line 20 clears the screen of any informa­tion.

Line 25 PRINTs 10 cursor-down commands. This just positions the ball

in the middle of the screen. If line 25 was eliminated the ball would
move across the top line of the screen.

Line 30 sets up a loop for moving the ball the 40 columns from the left

to right.

Line 40 does a lot of work. It first prints a space to erase the previous

ball positions, then it prints the ball, and finally it performs a cursor-left

to get everything ready to erase the current ball position again.

The loop set up in lines 50 and 60 slows the ball down a bit by delay-

ing the program. Without it, the ball would move too fast to see.

Line 70 completes the loop that prints balls on the screen, set up in

line 30. Each time the loop is executed, the ball moves another space to
the right. As you notice from the illustration, we have set up a loop
within a loop.

This is perfectly acceptable. The only time you get in trouble is when
the loops cross over each other. It's helpful in writing programs to check
yourself as illustrated here to make sure the logic of a loop is correct.

To see what would happen if you cross a loop, reverse the statements

in lines 60 and 70. You will get an error because the computer gets
confused and cannot figure out what's going on.

Lines 80 through 120 just reverse the steps in the first part of the
program, and move the ball from right to left. Line 90 is slightly differ­ent from line 40 because the ball is moving in the opposite direction (we
have to erase the ball to the right and move to the left).

44

And when that's all done the program goes back to line 20 to start the
whole process over
down and hit

For a variation on the program, edit line 40 to read:

40 PRINT "•";

Run the program and see what happens now. Because we left out the
cursor control, each ball remains on the screen until erased by the ball
moving right to left in the second part of the program.

again

. Pretty neat! To stop the program hold

TO MAKE THE S. HOLD THE SHIFT

KEY DOWN AND HIT THE LETTER "Q."

INPUT

Up to now, everything within a program has been set before it is run.
Once the program was started, nothing could be changed. INPUT
allows us to pass new information to a program as it is running and
have that new information acted upon.

To get an idea of how INPUT works, type NEW

short program:

and enter this

10 INPUT A$

20 PRINT "YOU TYPED:

.30 PRINT

40 GOTO 10

RUN

2

COMMODORE 54

YOU TYPED: COMMODORE 64

What happens when you run this program is simple. A question mark
will appear, indicating that the computer is waiting for you to type
something. Enter any character, or group of characters, from the
keyboard and hit i. The computer will then respond with "YOU
TYPED :" followed by the information you entered.

This may seem very elementary, but imagine what you can have the
computer do with any information you enter.

You can INPUT either numeric or string variables, and even have the
INPUT statement prompt the user with a message. The format of INPUT is:

INPUT "PROMPT MESSAGE";VARIABLE

YOU TYPED

COMPUTER
RESPONDED

PROMPT MUST BE 38 CHARACTERS OR LESS.

45

Or, just:

INPUT VARIABLE

NOTE:

To get out of this program

um M

6

keys.

hold down the

MIsI

The following program is not only useful, but demonstrates a lot of

what has been presented so far, including the new input statement.

NEW

1 F:EM TEMF'ERATI_IF:E C:ONVERICON PRC'GF:A19

5 PR I NT " { i_ LF:;•'HCit'lE)

10

PRINT "CONVERT FF:COM FAHRENHEIT OR CELSIUS

F/C'" : INF'CIT A:

20

I F A$ = "y' THEN 20

341

IF AS _ "F" THEN 100

40

IF AF <? "C" THEN 10

50

INPUT "ENTER DEO±REES CEL=:I U'_ : ".:C

F = :C*9:

60

70

PRINT C;" DEC;. CELSIUS F;" DEG.
FAHRENHEIT"

PRINT

8

0

_:fO i 0Ti1 10

100 INPUT "ENTER
1 10 C. = (:: F- ? *5r'99
120 PRINT F:" DES=.

C:EL!-:; I US

1:300 PRINT
14e0 GCITO 10

'/5+ 2

DEGREE FAHRENHEIT: ";F

FAHRENHEIT = ";

C_.;" DEG.

and

If you enter and run this program, you'll see INPUT in action.

the input statement to not only gather information, but

Line 10
also print our prompt. Also notice that we can ask for either a number or
string (by using a numeric or string variable).

Lines 20, 30, and 40 do some checks on what is typed in. In line 20, if
nothing is entered (just ^ is hit), then the program goes back to
line 10 and requests the input again. In line 30, if F is typed, you know
the user wants to convert a temperature in degrees Fahrenheit to Cel-

sius, so

Line 40 does one more check. We know there are only two valid
choices the user can enter. To get to line 40, the user must have typed

some character other than
acter is a C; if not, the program requests input

This may seem like a lot of detail, but it is good programming prac-

uses

the program branches to the part that does that conversion.

F. Now, a

check is made to see if that char-

'again.

tice. A user not familiar with the program can become very frustrated if

it does something strange because a mistake was made entering infor­mation.

Once we determine what type of conversion to perform, the program
does the calculation and prints out the temperature entered and the
converted temperature.

The calculation is just straight math, using the established formula for
temperature conversion. After the calculation is finished and answer

printed, the program loops back and starts over.

After running, the screen might look like this:

CONVERT FROM FAHRENHEIT OR CELSIUS (F/C): ?F

ENTER

:32 DEG

DEGREESFAHRENHEIT: 32

. FAHRENHEIT

= 0 DEG. CELSIUS

CONVERT FROM FAHRENHEIT

After running the program

program, as well as others presented throughout the manual

the base of your program

,

library.

OR CELSIUS (F,C):

make sure to save it on disk or tape. This

,

can form

GET

GET allows you to input one character at a time from the keyboard

without hitting.

cations.Whatever key is hit is assigned to the variable you specify with
GET.

The following routine illustrates how GET works:

NEW

This really speeds entering data in many appli-

1 PRINT " {CLR/HOME} "

10 GET A$: IF AS = " THEN 10
20 PRINT AS;
30 GOTO 10

47

If you RUN the program, the screen will clear and each time you hit a
key, line 20 will print it on the display, and then GET another character.
It is important to note that the character entered will not be displayed
unless you specifically PRINT it to the screen, as we've done here.

The second statement on line 10 is also important. GET continually

works, even if no key is pressed (unlike INPUT that waits for a response),
so the second part of this line continually checks the keyboard until a key

is hit.

See what happens if the second part of line 10 is eliminated.

To stop this program you can hit the MM and J:M keys.
The first part of the temperature conversion program could easily be

rewritten to use GET. LOAD the temperature conversion program, and
modify lines 10, 20 and 40 as shown:

10 PRINT

(F/C7"

20 GET A$
40 IF

This modification will make the program operate smoother, as nothing
will happen unless the user types in one of the desired responses to
select the type of conversion.

Once this change is made, make sure you save the new version of the

program.

RANDOM

The Commodore 64 contains a number of functions that are used to
perform special operations. Functions could be thought of as built-in
programs included in BASIC.. But rather than typing in a number of
statements each time you need to perform u specialized calculation, you
just type the command for the desired function and the computer does
the rest.

Many times when designing a game or educational program, you
need to generate a random number, to simulate the throw of dice, for
example. You could certainly write a program that would generate these
numbers, but an easier way to call upon the RaNDom number function.

To see what RND actually does, try this short program:

"

CONVERT FROM FAHRENHEIT

IF AS = "''

:

AS C:> "

C" THEN 20

NUMBERS

OR CELSIUS

_

T

HEN

AND OTHER FUNCTIONS

48

NEW

o

10 FOR
20 PRINT RND
30 NEXT

X = 1 T

1e

(

1)

IF YOU LEAVE OUT THE COMMA YOUR LIST

, OF NUMBERS

AS

After running the program, you will see a display like this:

WILL APPEAR

1 COLUMN

.789280697

.256373663

.682952381

.402343724

.158209063

Your numbers don't match? Well, if they did we would all be in

trouble, as they should be completely random!

Try running the program a few more times to verify that the results are
always different. Even if the numbers don't follow any pattern, you
should start to notice that some things remain the same every time the
program is run.

First, the results are always between 0 and 1, but never equal to 0 or

1 . This will certainly never do if we want to simulate the random toss of

dice, since we're looking for numbers between 1 and 6.

The other important feature to look for is that we are dealing with real
numbers (with decimal places). This could also be a problem since
whole (integer) numbers are often needed.

There are a number of simple ways to produce numbers from the
RND function in the range desired.

Replace line 20 with the following and run the program again:

.664673

.

0123442287

3.90587275E-04

.

879300926

.245596701

958

20 PRINT 6*RND(1),

RUN

3

3.6056

5.47238963

3.19265054

3.16331095

664

9.32527884

4.53660853

40850227

8.

4.39547668

5.50620749

4.17090293

49

That cured the problem of not having results larger than 1, but we still

hove the decimal part of the result to deal with.Now, another function

can be called upon.

The INTeger function converts real numbers into integer values.

Once more

see the effect of the change:

,

replace line 20 with the following and run the program to

0

PRINT

M

A

That took

generating random numbers between 1 and 6. If you examine
what we generated this last time

0 to 5, only.

As a last step,add a one to the statement

20 PRINT INT(6*RND

Now, we have achieved the desired results.

In general,you can place a number, variable
sion within the parentheses of the INT function. Depending on the range
desired
example

type:

you just multiply the upper limit by the RND function. For

,

to generate random numbers between 1 and 25

,

Ira? : 6* tl[I :: 1

El

care of a lot

,

(1))+1,

I

getting us closer to our original goal of

, you'll find that

the results range from

,

as follows:

or any BASIC expres-

,

you could

,

closely

(

20 PRINT INT

The general formula for generating a set of random numbers in a

certain range is:

25*RND(1))+1

NUMBER=INT(LOWER LIMIT+(UPPER

GUESSING GAME

Since we've gone to some lengths to understand random numbers,

why not put this information to use? The following game not only illus-

50

-

LOWER+1)*RND(1))

trates a good use of random numbers, but also introduces some addi­tional programming theory.

In running this program, a random number, NM, will be generated.

` INDICATES NO

NEW

1 REM NUMBER

2 PRINT "{CLR/HOME)"
5 INPUT "ENTER UPPER LIMIT FOR GUESS ".LI

10 NM

15 CN = 0

20 PRINT "I'VE GOT THE NUMBER.":PRINT

30 INPUT "WHAT'S YOUR GUESS".: GU

35 CN = CN + 1

40 IF GU > NM THEN PRINT "MY NUMBER IS

50 IF GU < NM THEN PRINT "MY NUMBER IS

60 PRINT "GREAT! YOU GOT MY NUMBER"

65 PRINT

70 PRINT "DO YOU WANT TO TRY ANOTHER (Y/N?":

80 GET AN$

90 IF

100 IF
110 END

= INT(LI*RND(1))+1

LOWER": PRINT : GOTO 30

HIGHER": PRINT : GOTO 30

RN$ = "Y" THEN 2

AN$ C? "N" THEN 70

GUESSING GAME

"IN ONLY ": CN :"GUESSES.":PRINT

:

IF AN$="" THEN 80

SPACE AFTER
QUOTATION MAR

You can specify how large the number will be at the start of the pro­gram. Then, it's up to you to guess what the number is.

A sample run follows along with an explanation.

ENTER UPPER LIMIT

I'VE GOT THE

WHAT'S YOUR GUESS 7 15
MY NUMBER IS HIGHER.

WHAT'S YOUR GUESS ? 20
MY NUMBER. IS LOWER.

WHAT

GREAT ! YOU GOT MY

IN ONLY 3 GUESSES.

DO YOU J WANT TO TRY ANOTHER. (Y/N`-

S YOUR GUE

'

NUMBER..

FOR GUESS?

SS ? 19

NUMBER

51

IF/THEN statements compare your guess to the number generated.

Depending on your guess

,

the program tells you whether

your

guess was

higher or lower than the random number generated.

From the formula given for determining random number range, see if
you can add a few lines to the program that allow the user to also
specify the lower range of numbers generated.

Each time you make a guess, CN is incremented by I to keep track of

the number of guesses.In using the program, see if you can use good

reasoning to guess a number in the least number of tries.

,

When you get the right answer

YOU GOT MY

NUMBER" message, along with the number of tries it took.

You can then start the process over again

the program prints out the

.

Remember

,

"GREAT!

the program

generates a new random number each time.

PROGRAMMING TIPS:

In lines 40 and 50, a colon is used to separate multiple statements on a single line.

This not only saves typing, but in long programs will conserve memory space.

Also notice in the IF/THEN statements on the same two lines, we instructed the
computer to PRINT something, rather than immediately branching to some other point
in the program.

The last point illustrates the reason behind using line numbers in increments of 10:

After the program was written, we decided to add the count part. By just adding
those new lines at the end of the program, numbered to fall between the proper
existing lines, the program was easily modified.

YOUR ROLL

The following program simulates the throw of two dice. You can enjoy

it as it stands, or use it as part of a larger game.

PRINT

5

PRINT

10

PRINT

20

PRINT

30

GET AS: IF AS = "" THEN 40

40

IF AS = CHRS(

50

Care to try your luck?

From what you've learned about random numbers and BASIC, see if

you can follow what is going on.

" Care

"RED DICE =
"WHITE DICE =
"HIT SPACE BAR FOR ANOTHER

to try ,Your luck? "

"

;INT(6•RND(1))+1

"

;INT(6*RND(1))+1

32) THEN 10

52

ROLL

":PRINT

RANDOM GRAPHICS

As a final note on random numbers, and as an introduction to design-

ing graphics, take a moment to enter and run this neat little program:

PRINT

10

PRINT

20

GOTrO

40

As you may have expected, line 20 is the key here. Another function,
CHR$ (Character String), gives you a character, based on a standard
code number from 0 to 255. Every character the Commodore 64 can

print is encoded this way (see Appendix F).

To quickly find out the code for any character, just type:

PRINT ASC("X")

where X is the character you're checking
character, including graphics). The response is the code for the char­acter you
which returns the standard

You can now print that character

PRINT CHR$(X)

If you try typing:

typed. As you

"{C:LR: HOME)

CHR$

(205.5 + RND':Ii) ;

20

probably figured

"ASCII" code for

by typing:

this can be any printable

(

out, "ASC"

the character

is another function,

you typed.

PRINT CHR$ (205

you will see the two right side graphic characters on the M and N keys.
These are the two characters that the program is using for the maze.

By using the formula 205
number between 205.5 and 206
number being above or below 206. CHR$ ignores any fractional values,
so half the time the character with code 205 is printed and the remain­ing time code 206 is displayed.

If you'

adding or subtracting a couple tenths from it
acter a greater chance of being selected.

d like to experiment with this program

CHR$(206)

);

5 + RND

.

1) the computer will pick a random

(

.

5. There is a

53

fifty-fifty

,

try changing

This will give either char-

.

chance of the

205.5 by

s

01

0
0

2

0

0

0

CHAPTER

5

ADVANCED COLOR

AND GRAPHIC

COMMANDS

• Color and Graphics

• PRINTing Colors

• Color CHR$ Codes

• PEEKS

• Screen Graphics

• More

and POKES'

Bouncing Balls

b11

COLOR AND GRAPHICS

Up to now we've explored some of the sophisticated computing
capabilities of the Commodore 64. But one of its most fascinating fea­tures is an outstanding ability to produce color and graphics.

You've seen a quick example of graphics in the "bouncing ball" and

"maze" programs. But these only touched on the power you command.

A number of new concepts will be introduced in this section to explain

graphic and color programming and show how you can create your own
games and advanced animation.

Because we've concentrated on the computing capabilities of the ma­chine, all the displays we've generated so far were a single color (light
blue text on a dark blue background, with a light blue border).

In this chapter we'll see how to add color to programs and control all

those strange graphic symbols on the keyboard.

PRINTING COLORS

As you discovered if you tried the color alignment test in Chapter 1,
you can change text colors by simply holding the= key and one of
the color keys. This works fine in the immediate mode, but what hap-

pens if you want to incorporate color changes in your programs?

When we showed the "bouncing ball" program, you saw how

keyboard commands, like cursor movement, could be incorporated
within PRINT statements. In a like way, you can also add text color
changes to your programs.

You have a full range of 16 text colors to work with. Using them

key and a number key, the following colors are available:

1 2 3 4 5 6 7 8

Black White Red Cyan Purple Green Blue Yellow

If you hold down the ® key along with the appropriate number

key, these additional eight colors can be used:

1 2 3 4 5 6 7 8

Orange Brown It

. Gray 1 Gray 2 Lt. It. Gray 3

Red Green Blue

TYPE NEW, and experiment with .he following. Hold down them

key and at the some time hit the 0 key. Next, hit the Q key without

56

•

holding down the =key. Now, while again depressing the Mkey
at the same time hit the key. Release theMkey and hit theOkey.
Move through the numbers, alternating with the letters, and type out the
word RAINBOW as follows:

10 PRINT

00

R1A1I1N1B

" 1

0

00000

1O1W"

RUN
RAINBOW

Just as cursor controls show as graphic characters within the quote

marks of print statements, color controls are also represented as graphic

characters.

In the previous example, when you held down 0 and typedua
'£" was displayed. M0 displayed a "-". Each color control will
display its unique graphic code when used in this way. The table shows
the graphic representations of each printable color control.

KEYBOARD COLOR DISPLAY KEYBOARD COLOR DISPLAY

00

m0

m©

M O CYAN

M0 PURPLE

=0 GREEN

m0

=0 YELLOW

BLACK

WHITE

RED

BLUE

L ®0 GRAY 1
0 ®

0

© ® 0 GRAY 3

0

[g

®0

®0

0

to 0 LT. GREEN

can

ORANGE

BROWN

LT. RED

GRAY 2

LT. BLUE

UI

Even though the PRINT statement may look a bit strange on the
screen, when you RUN the program, only the text will be displayed. And
it will automatically change colors according to the color controls you
placed in the print statement.

Try a few examples of your own, mixing any number of colors within a
single PRINT statement. Remember, too, you can use the second set of
text colors by using the Commodore key and the number keys.

TIP:

You will

"READY

mode change

7r::r6iPlli

notice

" prompt

and

after

. To get

running

and any

a program with color or mode (

additional text

back to the normal display,

you type is

57

reverse

the same as the lost

remember

to depress:

changes, that the

)

color or

COLOR

CHR$ CODES

Take a brief look at Appendix F, then turn back to this section.
You may have noticed in looking over the list of CHR$ codes in

Appendix F that each color (as well as most other keyboard controls,

such as cursor movement) has a unique code. These codes can be
printed directly to obtain the same results as typing • and the
appropriate key within the PRINT statement.

For example, try this:

NEW

10 FEINT CHR# 1::14 ' : PEN { C•LF'i`

L_t FE:I'ITi::HHHGE' ME Tii"i

RUN
CHR :: _ 0;' CHANGE'_; ME TO?

HCOME }

The text should now be green. In many cases, using the CHR$ func­tion will be much easier, especially if you want to experiment with
changing colors. The following program is a different way to get a rain-

bow of colors. Since there are a number of lines that are similar (40-

110) use the editing keys to save a lot of typing. See the notes after the

listing to refresh your memory on the editing procedures.

NEW

1 PEN AUTOMATIC CCILOF: E:HR'=.

5 PRINT C:HR.(147) : REM C:HR.(147:)= CLR/HOME

10 PRINT CHR$

20 CL = INT(8•RNG(

_:I_I ON CL GOTi 411 11 f.11, G,^:4+, !11 1311 1111
40 PRINT

50 PRINT GCOTCO 10
60 PRINT C:HF:f'30:? C:OTO 11

7 C+ PRINT CHR$ (:: =:1 :? GOTO 10

;_:0 FEI

90 PRINT CHR$(156:?;: GOTO 10

101 P

110 PRINT CHR$<:159:?;: GOTCI 10

CHF:3 (

NT CHR 144:? ; : OC'TO 10

RINT CHF3: 158); : GOTO 10

18) ., ' .-:F*EP1 R

1)>+1

5) GOT0 10 -

EVERS

E BAR

58

Type lines 5 through 40 normally. Your display should look like this:

1

REM AU

5

PRINT CHR$(147)

PRINT

113

20

CL = I NT *RND 1 +1

30

ON C:L GOTO 40,50,60,70, 80,90,100

40

PRINT CHR'$<5::' ; CiOTO 10

TOMATIC: COLOR BARE:

REM i_HR

CHR$(18 } : "

$(147;'= CLR,-'HOME

"; :REM REVERSE BARS

.,110

EDITING NOTES

Use the CRSR-UP key to position the cursor on line 40. Then type 5

over the 4 of 40. Next, use the CRSR-RIGHT key to move over to the 5 in

the CHR$ parentheses. Hit ®

rm-M

to open up a space and type

'28'. Now just hit i with the cursor anywhere on the line.

The display should now look like this:

REM

1

5

10

20 CL = I NT (=:*
:30 ON CL OOTO 40,`U,513

AUTOMATI

PRINT CHR$':: 14

C COLOR E:ARS

)

PRINT CHR$':: 18::' ; . : REM

RND':: 1

REM CHF

:' )+

1

$ f 14

„•0..80,90 101+.110

::' = CLR:-'

HCir1E

REVER'_.E BAR

50 PRINT CHR$ :'2 ::, :: GO TO 10

0

Don't worry. Line 40 is still there. LIST the program and see. Using the
same procedure, continue to modify the last line with a new line number
and CHR$ code until all the remaining lines have been entered. See, we

told you the editing keys would come in handy. As a final check, list the

entire program to make sure all the lines were entered properly before

you RUN it.

Here is a short explanation of what's going on.
You've probably figured out most of the color bar program by now

except for some strange new statement in line 30. But let's quickly see

59

what the whole program actually does. Line 5 prints the CHR$ code for
CLR/HOME.

Line 10 turns reverse type on and prints 5 spaces, which turn out to be

a bar, since they're reversed. The first time through the program the bar

will be light blue, the normal text color.

Line 20 uses our workhorse, the random function to select a random

color between 1 and 8.

Line 30 contains a variation of the IF . . . THEN statement which is

called ON . . . GOTO. ON . . . GOTO allows the program to choose
from a list of line numbers to go to. If the variable (in this case CL) has a
value of 1, the first line number is the one chosen (here 40). If the value

is 2, the second number in the list is used, etc.

Lines 40-110 just convert our random key colors to the appropriate

CHR$ code for that color and return the program to line 10 to PRINT a
section of the bar in that color. Then the whole process starts over

again.

See if you can figure out how to produce 16 random numbers, ex­pand ON . . . GOTO to handle them, and add the remaining CHR$
codes to display the remaining 8 colors.

O

1

■

PEEKS AND POKES

No, we're not talking about jabbing the computer, but we will be able

to "look around" inside the machine and "stick" things in there.

Just as variables could be thought of as a representation of "boxes"
within the machine where you placed your information, you can also
think of some specially defined "boxes" within the computer that repre­sent specific memory locations.

The Commodore 64 looks at these memory locations to see what the
screen's background and border color should be, what characters are to
be displayed on the screen-and where-and a host of other tasks.

By placing, "POKEing," a different value into the proper memory lo­cation, we can change colors, define and move objects, and even
create music.

These memory locations could be represented like this:

53280

X

BORDER

COLOR

53281

Y

BACKGROUND

COLOR

53282

53283

60

0

On page 60 we showed just four locations,

screen and background colors.

Try typing this:

two of which

POKE 53281,7

The background color of the screen will change to yellow because we
placed the value '7'-for yellow-in the location that controls the
background color of the screen.

Try POKEing different values into the background color location, and

see what results you get. You can POKE any value between 0 and 255,

but only 0 through 15 will work.

The actual values to POKE for each color are:

control the

0

1

2 RED

3

4
5 GREEN
6

7

BLACK

WHITE

CYAN

PURPLE

BLUE

YELLOW

8

9

10

11
12

13
14

15

ORANGE

BROWN
Light RED

GRAY 1
GRAY 2

Light GREEN
Light BLUE

GRAY 3

Can you think of a way to display the various background and border

combinations? The following may be of some help:

10 FOR 88 = 0 TO 15

20 FOR BO = 0 TO 15

30 POKE

53280, BR.

40 POKE 53281, BO

50 FOR
60 NEXT 8

X = 1 TO 2000 NE:<T X

0

: NEXT 88

RUN

Two simple loops were set up to POKE various values to change the

background and border colors. The DELAY loop in line 50 just slows
things down a bit.

61

For the curious, try:

? PEEK(53280) AND 15

You should

and makes sense because

GRAY (value 15) after the program is run.

By entering

cause

of the way color codes are stored in the computer. Normally you

get a value

of 15. This is the last value BORDER was given

both the background and border colors are

AND 15 you eliminate all other values except 1-15, be-

would expect to find the some value that was last POKEd in the location.

In general

, PEEK

lets us examine

a specific location and see what value

is presently there. Can you think of a one line addition to the program

that will display the value of BACK and BORDER as the program runs?

How about this:

25 PRINT CHR$

GROUND

(

147); "BORDER = ";PEEK

= ";

PEEK (53281) AND 15

(

53280

) AND 15, "BACK-

SCREEN GRAPHICS

In all the printing of information that you've done so for, the computer
normally handled information in a sequential fashion: one character is
printed after the next, starting from the current cursor position (except

where you asked for a new line, or used the ',' in PRINT formatting).

To PRINT data in a particular spot you can start from a known place

on the screen and PRINT the proper number of cursor controls to format

the display. But this takes program steps and is time consuming.

But just as there are certain spots in the Commodore 64's memory to

control color, there are also locations that you can use to directly control
each location on the screen.

SCREEN MEMORY MAP

Since the computer'

columns by 25 lines) there are 1000 memory locations set aside to han­dle what is placed on the screen. The layout of the screen could be
thought of as a grid, with each square representing a memory location.

And since each location in memory can contain a number from 0 to

255, there are 256 possible values for each memory location. These

values represent the different characters the Commodore 64 can display

(see Appendix Q. By POKEing the value for a character in the appro-

s screen is

capable of holding 1000 characters (40

62

W

priate screen memory location, that character will be displayed in the

proper position.

1024 ­1064
1104
1144
1184
1224
1264
1304
1344
1384
1424
1464

1504

1544
1584
1624
1664
1704
1744
1784
1824
1864
1904
1944
1984

COLUMN

0

10

20

30

39

1063

f

2023

0

20

24

Screen memory in the Commodore 64 normally begins at memory
location 1024, and ends at location 2023. Location 1024 is the upper left
corner of the screen. Location 1025 is the position of the next character

to the right of that, and so on down the row. Location 1063 is the

right-most position of the first row. The next location following the last

character on a row is the first character on the next row down.

Now, let's say that you're controlling a ball bouncing on the screen.

The ball is in the middle of the screen, column 20, row 12. The formula
for calculation of the memory location on the screen is:

POINT = 1024 + X + 40*Y

COLUMN

ROW

where X is the column and Y is the row.

Therefore, the memory location of the ball is:

1024 + 20 + 480 or 1524

63

COLUMN

ROW (40' 12)

Clear the screen with ® and

CIR/HOME

and type:

POKE 1524,81
POKE 55796,1

COLOR

Li

LOCATION

COLOR MEMORY MAP

A ball appears in the middle of the screen! You have placed a char-

acter directly into screen memory without using the PRINT statement.
The ball that appeared was white. However there is a way to change
the color of an object on the screen by altering another range of mem­ory. Type:

POKE 55796,2. COLOR

LOCATION

The ball's color changes to red. For every spot on the Commodore 64's
screen there are two memory locations, one for the character code, and
the other for the color code. The color memory map begins at location
55296 (top left-hand corner), and continues on for 1000 locations. The

55296
55336
55376
55416
55456
55496
55536
55576

55616
55656
55696
55736
55776
55816
55856
55896
55936
55976
56016
56056

56096

56136

56176

56216

56256

0

L

10

COLUMN

20

30

39

55335

f

56295

20

24

64

same color codes, from 0-15, that we used to change border and
background colors can be used here to directly change character colors.

The formula we used for calculating screen memory locations can be

modified to give the locations to POKE color codes. The new formula is:

COLOR PRINT = 55296 + X + 40*Y

MORE BOUNCING BALLS

Here's a revised bouncing ball program that prints directly on the
screen with POKEs, rather than using cursor controls within PRINT state­ments. As you will see after running the program, it is much more flexi­ble than the earlier program, and will lead up to programming much

more sophisticated animation.

NEW

10

PRINT "{CLR/HUME)"

20

POKE 53280,7 : POKE 53281,13

30

40

50
60
70

80

90

100

110
120

X =

DX =

POKE
FOR
POKE

X = X + DX

1 : Y = 1

1 DY = 1

1024 + X + 40*Y.81

=

T

IF X < = 0 OR X i =

Y = Y + DY

IF Y = 0 OR Y

GOTO 50

1 TO 10 : NEXT

1024

+

X + 40*Y,32

39 THEN DX = -DX

? =

24 THEN DY = -DY

Line 10 clears the screen, and line 20 sets the background to light

green with a yellow border.

The X and Y variables in line 30 keep track of the current row and

column position of the ball. The DX and DY variables in line 40 are the

horizontal and vertical direction of the ball's movement. When a +1 is

added to the X value, the ball is moved to the right; when -1 is added,
the ball moves to the left. A + 1 added to Y moves the ball down a row;
a -1 added to Y moves the ball up a row.

Line 50 puts the ball on the screen at the current cursor position. Line
60 is the familiar delay loop, leaving the ball on the screen just long
enough to see it.

Line 70 erases the ball by putting a space (code 32) where the ball
was on the screen.

65

Line 80 adds the direction factor to X. Line 90 tests to see if the ball

has reached one of the side walls, reversing the direction if there's a
bounce. Lines 100 and 110 do the same thing for the top and bottom

walls.

Line 120 sends the program back to display and moves the ball

again.

By changing the code in line 50 from 81 to another character code,
you can change the ball to any other character. If you change DX or DY
to 0 the ball will bounce straight instead of diagonally.

We can also add a little more intelligence. So for the only thing you
checked for is the X and Y values getting out of bounds for the screen.

Add the following lines to the program.

21 FOR L = 1 TO 10

25 POKE 1024 + INT(RND(
27 NEXT L

55 IF PEEK(1024 + X + 40*Y) = 166 THEN DX _ -DX:

GOTO 80

105 IF PEEK<1024 + X + 40*Y) = 166 THEN DY = -DY:

GOTO 100

1)*1000), 166

Lines 21 to 27 put 10 blocks on the screen in random positions. Lines

85 and 105 check (PEEK) to see if the ball is about to bounce into a

block, and changes the ball's direction if so.

0

e

•

0

66

HAP

C

T

ER

SPRITE

• Introduction to Sprites

• Sprite Creation

• Additional

• Binary Arithmetic

GRAPHICS

Notes on Sprite

67

INTRODUCTION TO SPRITES

In previous chapters dealing with graphics

symbols could be used in PRINT statements to create animation and add

chartlike appearances to our displays.

we saw that graphic

,

A yygy was also shown to POKE character codes in specific screen

memory locations

This would then place the appropriate characters di-

.

rectly on the screen in the right spot.

Creating animation in both these cases requires a lot of work because
objects must be created from existing graphic symbols. Moving the ob­ject requires a number of program statements to keep track of the ob-

And, because of the limitation of using

ject and move it to a new spot

the shape and resolution of the object might not be as

graphic symbols

,

.

good as required.

Using sprites in animated sequences eliminates a lot of these prob­lems. A sprite is a high-resolution programmable object that can be
made into just about any shape
can be easily moved around the screen by simply telling the computer

the position the sprite should be moved to. The computer takes care of
the rest.

And sprites have much more power than just that. Their color can be

changed

made to go in front and behind another
panded in size, just for starters.

The penalty for all this is minimal. However
knowing some more details about how the Commodore 64 operates and
how numbers are handled within the computer
sounds
sprites do amazing things in no time.

;

you can tell if one object collides with another

.

though

,

Just follow the examples and you'll be making your own

through BASIC commands. The object

-

;

they can be

;

and they can be easily ex-

,

using sprites requires

.

It's not as difficult as it

AM

IML

r

SPRITE CREATION

Sprites are controlled by a separate picture-maker in the Commodore

64. This picture maker handles the video display. It does all the hard
work of creating and keeping track of characters and graphics, creating
colors, and moving around.

This display circuit has 46 different "ON/OFF" locations which act like

internal memory locations. Each of these locations breaks down into a
series of 8 blocks. And each block can either be "on" or "off". We'll get
into more detail about this later. By POKEing the appropriate decimal
value in the proper memory location you can control the formation and
movement of your sprite creations.

68

In addition to accessing many of the picture making locations we will

also be using some of the Commodore 64's main memory to store infor-

mation (data) that defines the sprites. Finally, eight memory locations
directly after the screen memory will be used to tell the computer exactly
which memory area each sprite will get its data from.

As we go through some examples, the process will be very

straightforward, and you'll get the hang of it.

So let's get on with creating some sprite graphics. A sprite object is 24

dots wide by 21 dots long. Up to eight sprites can be controlled at a

time. Sprites are displayed in a special independent 320 dot wide by
200 dot high area. However, you can use your sprite with any mode,
high-resolution, low-resolution, text etc.

Say you want to create a balloon and have it float around the sky.

The balloon could be designed as in the 24 by 21 grid on page 70.

The next step is to convert the graphic design into data the computer
can use. Get a piece of notebook or graph paper and set up a sample
grid that is 21 spaces down and 24 spaces across. Across the top write

128,64,32,16,8,4,2,1, three times (as shown) for each of the 24
squares. Number down the left side of the grid 1-21 for each row. Write
the word DATA at the end of each row. Now fill in the grid with any
design or use the balloon that we have. It's easiest to outline the shape

first and then go back and fill in the grid.

Now if you think of all the squares you filled in as "on" then substitute
a 1 for each filled square. For the one's that aren't filled in, they're "off"
so put a zero.

Starting on the first row, you need to convert the dots into three sepa-

rate pieces of data the computer can read. Each set of 8 squares is

equal to one piece of data called a byte in our balloon. Working from

the left, the first 8 squares are blank, or 0, so the value for that series of

numbers is 0.

The middle series looks like this (again a 1 indicates a dot, 0 is a

space):

128 64 32 16 8 4 2 1

The third series on the first row also contains blanks, so it, too, equals

zero. Thus, the data for the first line is:

0

1

1 1

T T T T T T T T

0 + 64 + 32

+

16 + 8 + 4 + 2 + 1 = 127

DATA 0, 127, 0

69

1

1 1

1

SERIES SERIES SERIES

1 2 3

128 32 8 2 128 32 8 2 128 32 8 2

64 16 4 11 64 16 4 11 64 16 4 1

1
2

3
4

5
6
7
8

9

10

11

12
13

14

15
16
17

18
19
20
21

1

5

10 15

COLUMN

20

a

0

24

The series that make up row two are calculated like this:

Series 1:

Series 2: 1 1

0 0

0 0 0 0

1 1 1 1 1

T T T T T T T T

+

4 + 2 + 1 = 255

0

0

0 0

Series 3:

128 + 64 + 32 + 16 + 8

1

1

0 0

I

T T

128 + 64

For row 2, the data would be:

DATA

In the same way, the three

would be converted into their decimal value. Take the time to do the

remainder of the conversion in this example.

Now that you have the data for your object, how can it be put to use?

Type in the following program and see what happens.

series

1,255,192

that make up each remaining row

1

1 = 1

1

= 192

•

•

70

1 REM

5 PRINT

UP, UP, AND RWRY!

"{CLRIHOME}"

10 V= 53248 : REM START OF DISPLAY CHIP
11 POKE V+21.

12 POKE 2042,13 : REM

4 : REM

ENABLE SPRITE 2

SPRITE 2 DATA FROM 13TH BLK

20 FOR N = 0 TO 62: READ Q : POKE 832+N,Q: NEXT

30 FOR

40 POKE

X = 0 TO

V+4,X: REM UPDATE X COORDINATES

200 GETS ITS INFO. FROM DATA'

50 POKE V+5,X: REM UPDATE Y COORDINATES
60 NEXT X

70 GOTO 30_ INFO.

200 DATA

0,127,0,1,255,192,3,255,224,3,231,224

READ IN FROM Q-

210 DATA 7,217,240,7,223,240,7,217,240,3,231,224

220 DATA
230 DATA
240 DATA 0,62,0,0

FOR MORE DETAIL ON READ & DATA SEE CHAPTER 8.

3,255,224,3,255,224,2,255,160,1,127,64

1,62,64,

0,156,128,0,156,128,0

,

62,0,0,62,0,0,28,0

,73,0,0,73,0

If you typed everything correctly, your balloon is smoothly flying

across the sky (page 72).

In order to understand what happened, first you need to know what
picture making locations control the functions you need. These locations,
called registers,could be illustrated in this manner:

Register(s) Description

0 X coordinate of sprite 0

1 Y coordinate of sprite 0

2 - 15 Paired like 0 and 1 for sprites 1-7

16 Most Significant Bit-X Coordinate

21 Sprite appear:
29 Expand sprite in "X" Direction

1 =appear 0=disappear

23 Expand sprite in "Y" Direction

39 - 46 Sprite 0 - 7 color

In addition to this information you need to know from which 64 byte

section sprites will get their data (1 byte is not used).

This data is handled by 8 locations directly after screen memory:

2040

SPRITE 0

Now let

41 42 43 44

T T T T

1 2 3 4

'

s outline the exact procedure to get things moving

45 46 2047

T T T

5 6 7

write a program.

and finally

71

r

ACTUAL SCREEN PHOTO

There are only a few things necessary to actually create and move an

object.

1. Make the proper sprite(s) appear on the screen by POKEing into lo­cation 21 a 1 for the bit which turns on the sprite.

2. Set sprite pointer (locations 2040-7) to where sprite data should be
read from.

3. POKE actual data into memory.

4. Through a loop, update X and Y coordinates to move sprite around.

5. You can, optionally, expand the object, change colors, or perform a

variety of special functions. Using location 29 to expand your sprite in

the "X" direction and location 23 in the "Y" direction.

There are only a few items in the program that might not be familiar

from the discussion so far.

In line 10;
V=53248

0

0

sets V to the starting memory location of the video chip. In this way we
just increase V by the memory number to get the actual memory loca­tion. The register numbers are the ones given on the sprite register map.

72

In line 11,

POKE V+21,4

makes sprite 2 appear by placing a 4 in what is called the sprite enable
register (21) to turn on sprite 2. Think of it like this:

SPRITES

Decimal

values of each

sprite number

Sprite Level Number

=4

21

128 64 32 16

7

6

0

0

2 1

5

0

4

3

0

0

2

1

1

0

0

0

Put a I For The SPRITE

Each sprite level is represented in section 21 of the sprite memory and

4 happens to be sprite level 2. If you were

using

level 3 you would put a

1 in sprite 3 which has a value of 8. In fact if you used both sprites 2
and 3 you would put a 1 in both 4 and 8. You would then add the
numbers together just like you did with the DATA on your graph paper.
So, turning on sprites 2 and 3 would be represented as V+21,12.

In line 12;

POKE 2042,13

instructs the computer to get the data for sprite 2 (location 2042) from
the 13th area of memory. You know from making your sprite that it
takes up 63 sections of memory. You may not have realized it, but those

numbers you put across the top of your grid equal what is known as 3
bytes of the computer. In other words each collection of the following
numbers, 128,64,32,16,8,4,2,1 equals 1 byte of computer memory.
Therefore with the 21 rows of your grid times the 3 bytes of each row,
each sprite takes up 63 bytes of memory

READ Q: POKE 832+N

20 FOR N

=

0 to 62

:

. I WHOLE SPRITE

,

Q: NEXT

You Want

This line handles the actual sprite creation. The 63 bytes of data that
represent the sprite you created are READ in through the loop and
POKEd into the 13th block of memory. This starts at location 832.

30 FOR X = 0 TO 200

40 POKE V+41
50 POKE V+S,X

If you

remember

horizontal movement across the screen and the Y coordinate represents

the sprite's vertical movement across the screen. Therefore as the values

from school the X coordinate represents an objects

73

of X change in line 30 from 0 to 200 (one number at a time) the sprite

moves across the screen DOWN and TO THE RIGHT one space for each

number. The numbers are READ by the computer fast enough to make
the movement appear to be continuous, instead of 1 step at a time. If
you need more details take a look at the register map in Appendix O.

When you get into moving multiple objects, it would be impossible for

one memory section to update the locations of all eight objects. There­fore each sprite has its own set of 2 memory sections to make it move on
the screen.

Line 70 starts the cycle over again, after one pass on the screen. The
remainder of the program is the data for the balloon. Sure looks differ­ent on the screen, doesn't it?

Now, try adding the following line:

POKE V+29,4: REM EXPAND

25 POKE V+23,4

and RUN the program again. The balloon has expanded to twice the
original size

sprite 2
X and Y direction.

It's important to note that the sprite will start in the upper left-hand

corner of the object. When expanding an object in either direction, the

starting point remains the same.
For some added excitement

! What we did

)

into memory sections 23 and 29

:

was simple. By POKEing 4 (again to indicate

sprite 2 was expanded in the

,

make the following changes:

,

P

D

5

11 POKE V+21,12
12 POKE 2042

30 FOR X
45 POKE V+6,X
55 POKE V

A second sprite

memory location that makes the sprite appear
sprites 3 and 2 on (00001100 = 12).

The added lines 45 and 55 move sprite 3 around by POKEing values

into sprite 3's X and Y coordinate locations

Want to fill the sky with even more action

tions:

11 POKE V+21,28-

12

POKE 2042,13:POKE 2043,13:POKE 2044,13

25

POKE V+23,12 : POKE V+29,12

48

POKE V+8,X

58

POKE V+9,100

,

13 : POKE 2043,13

=

1 to 190

+

7,190-X

number 3)has been turned

(

on by

(V+21). The

(V+6 and V+7).

?

Try making these addi-

28 IS REALLY

(SPRITE 3) + 16 (SPRITE 4)

74

4 (SPRITE 2) + 8

POKEing 12 into the

12 turns

In line 11 this time, another sprite (4) was made to appear by POKE­ing 28 into the appropriate "on" location of the sprite memory section.
Now sprites 2-4 are on (00011100 = 28).

Line 12 indicates that sprite 4 will get its data from the same

memory area (13th 63 section area) as the other sprites by POKEing
2044,13.

In line 25, sprites 2 and 3 are expanded by POKEing 12 (Sprites 2
and 3 on) into the X and Y direction expanded memory locations (V+23
and V+29).

Line 48 moves sprite 3 along the X axis. Line 58 positions sprite 3
halfway down the screen, at location 100. Because this value does not
change, like it did before with X=0 to 200, sprite 3 just moves horizon-

tally.

ADDITIONAL NOTES ON SPRITES

Now that you've experimented with sprites, a few more words are in

order. First, you can change a sprite's color to any of the standard 16

color codes (0-15) that were used to change character color. These can
be found in Chapter 5 or in appendix G.

For example, to change sprite 1 to light green, type: POKE

V+40,13 (be sure to set V=53248).

You may have noticed in using the example sprite programs that

the object never moved to the right-hand edge of the screen. This was

because the screen is 320 dots wide and the X direction register can
only hold a value up to 255. How then can you get an object to move
across the entire screen?

There is a location on the memory map that has not been men-

tioned yet. Location 16 (of the map) controls something called the most

significant bit (MSB) of the sprite's X direction location. In effect, this

allows you to move the sprite to a horizontal spot between 256 and 320.

The MSB of X register works like this: after the sprite has been

moved to X location 255, place a value into memory location 16 repre-

senting the sprite you want to move. For example, to get 2 to move to

horizontal locations 256-320, POKE the value for sprite 2 which is (4) into
memory location 16:

POKE

Now start from 0 again in the usual X direction register for sprite 2
(which is in location 4 of the map). Since you are only moving another 64
spaces, X locations would only range between 0 and 63 this time.

V+ 16,4.

75

This whole concept

is best illustrated with a version of the original

sprite 1 program:

10

V= 532

20

FOR N = 0 Ti] 62 : READ Q : POKE 832+N,Q

25

POKE V+5, 100

30

FOR X=0TO255

40

POKE V+4,X

50

NEXT

60

POKE V+16,4

70

FORX=0TO63

-48 : POKE V+211,4 : POKE 2042,13

80 POKE 'd+4 , X
90 NEXT

100 POKE V+16,0

110 GOTO 30

Line 60 sets the most significant bit for sprite 2. Line 70 starts moving
the standard X direction location, moving sprite 2 the rest of the way
across the screen.

Line 100 is important because it "turns off" the MSB so that the

sprite can start moving from the left edge of the screen again.

To define multiple sprites, you may need additional blocks for the
sprite data. You can use some of BASIC's RAM by moving BASIC. Before
typing or loading your program type:

5

NEXT

5

10

I

1k

W

0

0

POKE44,16:POKE 16*256,0:NEW

Now, you can use blocks 32 through 41 (locations 2048 through 4095) to
store sprite data.

BINARY ARITHMETIC

It is beyond the scope of this introductory manual to go into details of
how the computer handles numbers. We will, however, provide you with
a good base for understanding the process and get you started on
sophisticated animation.

But, before you get too involved we have to define a few terms:

BIT-This is the smallest amount of information a computer can store.

O

76

Think of a BIT as a switch that is either "on" or "off". When a BIT is
"on" it has a value of 1; when a BIT is "off" it has a value of 0.

After BIT, the next level is BYTE.

-This is defined as a series of BITS. Since a BYTE is made up of

BYTE

8 BITS, you can actually have a total of 256 different combinations
of BITS. In other words, you can have all BITS "off" so your BYTE
will look like this:

128

0

64

32

0

0

16

0

8

0

4
0

2

0

and its value will be 0. All BITS "on" is:

128 64 32

1

which

1

1

is 128+64+32+16+8

16

1

+2+1=255.

8

1

4

1

2

1

The next step up is called a REGISTER.

REGISTER

-Defined as a block of BYTES strung together. But, in this

case each REGISTER is really only 1 BYTE long. A series of REGIS­TERS makes up a REGISTER MAP. REGISTER MAPS are charts like
the one you looked at to make your BALLOON SPRITE. Each REGIS­TER controls a different function, like turning on the SPRITE is really

called the ENABLE REGISTER. Making the SPRITE longer is the EX-

PAND X REGISTER, while making the SPRITE wider is the EXPAND Y

REGISTER. Keep in mind that a REGISTER is a BYTE that performs a

specific task.

0

s move on to the rest

Now let

'

BINARY TO DECIMAL CONVERSION

128 64 32 16 8 4 2 1

0 0
0
0 0
0
0
0
0

1

0

0
0
0

1

0

0
0
0 0
0
0

1
0
0

of BINARY ARITHMETIC.

Decimal Value

0

0 0

0

1

0
0 0
0

0 0 0

0

1
0 0
0

0

77

0

1

0 0

0
0 0
0

1

1

0

0
0

0

0
0
0
0
0
0
0

2T0

2 TI

2T2
2T3
2T4
2T5
2T6
217

Using combinations of all eight bits, you can obtain any decimal value

from 0 to 255. Do you start

to see

why when we POKEd character or

S

0

color values into memory locations the values had to be in the 0-255

range? Each memory location can hold a byte of information.

Any possible combination of eight 0's and l's will convert to a

unique decimal value between 0-255. If all places contain a 1 then the

value of the byte equals 255. All zeros equal a byte value of zero;

"00000011" equals 3, and so on. This will be the basis for creating data
that represents sprites and manipulating them. As just one example, if
this byte grouping represented part of a sprite (0 is a space, 1 is a

colored area):

2t 2s

128+ 64

Then we would POKE 255 into the appropriate memory location to

represent

T1PF

need to

idea to

that part of the object.

To save you the trouble of converting binary numbers into decimal

do that a lot-the following program will do the work for you.

enter

25

+

32+ 16+ 8

and save the program for future use.

24

23

+ 4+ 2+ 1 + = 255

22

21

20

values-we'll

It's a good

S

0

s
s

5 REM BINARY TO DECIMAL CONVERTER

10 INPUT "ENTER 8-BIT BINARY NUMBER :":A$
12 IF LEN (A$) :: 8 THEN PRINT "8 BITS PLEASE...":

GOTO 10

15 TL = 0 : C = 0

20 FOR X = 8 to 1 STEP -1 : C = C_. + 1

30 TL = TL + VAL(MID$(A$,C,1))*2f(X-1)

40 NEXT X

50 PRINT A$;" BINARY = ";TL;" DECIMAL"
60 GOTO 10

This program takes your binary number, which

at each character of the string, from left to right (the MID$ function). The variable C

indicates

are dealing
example

power of 2. Since the first value is in the 2T7 place, in the example, TL would first

equal

zero.

This process is repeated for all eight characters as TL keeps track of the running

total decimal value of the

what character to work on as the program

The SAL function, in line 30, returns the actual value of the character. Since we

with numeric characters,

, if the first character of AS is 1 then the value would also be 1.

The final part of line 30 multiplies the value of the current character by the proper

1 times 128 or 128. If the bit is 0 then the value for that place would also be

binary number.

the value

was entered as a string

through the loop.

goes

is the same as the character. For

, and looks

78

0

S

^,

CHAPTER

,.;

. 7

CREATING SOUND

• Using Sound
Programmer

• Structure of a Sound Program

• Sample Sound Program

• Making Music on Your Commodore 64

• Important Sound Settings

• Playing a Song on the Commodore 64

• Creating Sound Effects

• Sample Sound

if You'

Effects to Try

re Not a Computer-

79

USING

SOUND

IF YOU

'RE NOT

A COMPUTER

"PROGRAMMER"

Most programmers use computer sound for two purposes: making
music and generating sound effects. Before getting into the "intricacies"
of programming sound, let's take a quick look at how a typical sound

program is structured . . . and give you a short sound program you can
experiment with.

STRUCTURE OF A SOUND PROGRAM

To begin with, there are five settings which you should know in order
to generate sound on your

COMMODORE 64: VOLUME

,

ATTACK/ DE­CAY, SUSTAIN/RELEASE(ADSR ),
FREQUENCY/LOW FREQUENCY

ONCE at the beginning of your program. The high and low frequency
settings must be set for EACH NOTE you play. The waveform control
starts and stops each note.

WAVEFORM CONTROL and HIGH

. The first three settings are usually set

SAMPLE SOUND PROGRAM

Before you start you have to choose
Each voice requires different sound setting numbers for Waveform, etc.
You can play 1, 2 or 3 voices together but our sample

NUMBER

RETURN key after each line:
First clear sound chip. 5 FORL=54272TO54296:

1. Set VOLUME

2. Set ATTACK
define how fast a note rises to and
falls from its peak volume level (0
to 255).

3. Set
level to prolong note
release it.

4. Find
play in the

NOTES

the HIGH

FREQUENCY values for that note

each note requires 2 POKEs).

(

1. Type in this program line by line . . . be sure to hit the

at highest setting.

/DECAY

SUSTAIN/RELEASE

the note

in Appendix

-

FREQUENCY and LOW-

/tone you want to 40 POKE54273,17:POKE54272,37

TABLE OF MUSICAL

rates to 20 POKE54277,190

to define 30 POKE 54278,

and rate to ,b

M and enter

80

a VOICE

POKEL,O:NEXT

10 POKE54296,15

. There are 3 voices.

uses only VOICE

248 is

S
S
0

0

5. Start

WAVEFORM

with one of 50 POKE54276,17

4 standard settings (17, 33, 65

or 129);.

6. Enter a time loop to set the
DURATION

played (a quarter note is approx.

"250" but may vary since a longer

program can affect the timing).

7. Turn off note.

of the note to be

60 FORT=1TO250:NEXT

70 POKE54276,16

To hear the note you just created

key. To view the program type the word LIST and hit

, type the word

RUN and then hit the

To change it, retype the lines you want to alter.

MAKING MUSIC ON YOUR COMMODORE 64

You don't have to be a musician to make music on your COMMODORE
64! All you need to know are a few simple numbers which tell your
computer how loud to set the volume, which notes to play, how long to
play them, etc. But first . . . here's a program which gives you a quick

demonstration

using only ONE of your computer's 3 separate

Type the word NEW and hit to

gram

then enter

,

key.

of the COMMODORE 64's incredible music capabilities,

voices.

erase

your previous pro-

this program, type the word RUN and hit the

L

5 REM MUSICAL SCALE 4 .-Title

7 FORL=54272TO54296:POKEL,O:NEXT

10 POKE 54296,15-E

20 POKE 54277,9 t
30 POKE 54276,17'

40 FORT=1TO30O

50 READ A'

NEXI<

:

of program.

Sets volume at highest setting (15).

Sets Attack/Decay
Sustain

/Release

Determines waveform

Duration(how long)each note plays.

Reads first number

81

level (each note)

(type of sound).

in line 110 DATA.

60 READ B F
70 IFB=-1THENEND

80 POKE 54273,A: POKE54272,

B E--POKES the first number from DATA

85 POKE 54276,17 E -- Start note

90 FORT=1 TO250: NEXT: POKE54276, 16

FORT=1TO50:NEXT Time for release.

1

100 GOT020 E

0

0

110 DATA] 7,37,19,63,21,154,22,227
120 DATA 25,177,28,214,32,94,34,175

note

value

110 DATA.

in line 110 (A= 17)

HIGH and LOW

54273=HIGH

54272=

chart

in Appendix

"

C" of the 4th oc-

"

D" and so on.

,

and so on,

Reads second number in line

ENDS when it READS -1 in line 900.

as HIGH FREQUENCY and second number (B=37)

as LOW

FREQUENCY.Next time program loops

around it READS A as 19 and B as 63

and POKEs these numbers into the

FREQUENCY locations.The number

FREQUENCY for VOICEI and

QUENCY for VOICEI.

Let it ploy

Loops back to reset CONTROL and play new note.

Musical

note

Each pair of numbers represents one note. For

M.

example

tave, 19 and 63 represent

then stop note

values

from

17 and 37 represent

,

LOW FRE-

900 DATA-1,-1

When program

FREQUENCY
line 70.

-1 it turns off HIGH/LOW

reaches

settings and ENDS as instructed in

To change the sound to a "harpsichord," change Line 85 to read

POKE54276,33 and Line 90 to read FORT= 1T0250:NEXT: POKE54276,32
and RUN the program

again

. (To change the line, hit the

to stop the program, type the word LIST and hit

the program line you want to change

the new line will automatically

;

RUN/STOP

, then retype

replace the old one). What we did here is change the "waveform" from
a "triangular

WAVEFORM
MODORE 64 . . .

shaped sound wave to a "sawtooth" wave. Changing the

"

can drastically change the sound produced

by the COM-

but . . . waveform is only one of several settings you

can change to make different musical tones and sound effects! You can

also change

the ATTACK/DECAY

change from a "harpsichord

rate of each note . . . for example, to

sound to a more "banjo

"

"

sound try chang-

ing lines 20 and 30 to read:

O

key

e

S

20 POKE54277,3

30 POKE54278,0

82

Sets no

sustain

for banjo effect.

S

As you'

different

ve just seen

,

you can make

musical instruments

your COMMODORE

.

Let's take a closer look at how each sound

setting works

IMPORTANT SOUND SETTINGS

64 sound like

1 VOLUME

POKE 54296,15. The volume

-To turn on the volume and set it to the highest level, type:

setting ranges

from 0 to 15 but you

most of the time. To turn "off" the volume, type:

POKE 54296,0

You only have to set the volume ONCE at the beginning of your pro­gram, since the some setting activates all three of the Commodore 64's
VOICES. (Changing the volume during
can produce interesting results but is beyond the scope of this introduc­tion.)

2. ADSR and WAVEFORM CONTROL SETTING

how changing the waveform can change the sound effect from
"xylophone" to "harpsichord" Each VOICE has its own WAVEFORM

CONTROL SETTING which lets you define four different types of
waveforms: Triangle, Sawtooth, Pulse (Square
TROL also activates the COMMODORE 64's ADSR feature, but we'll

come back to this

in a moment.A sample

like this:

POKE 54276,17

a musical

) and Noise

waveform start

note or sound effect

-You've already seen

'll use 15

. The CON-

setting looks

where the first number (54276) represents the control setting for VOICE 1
and the second number (
waveform.

The settings

are shown in the table below.

ADSR AND WAVEFORM CONTROL SETTINGS

VOICE 1
VOICE 2
VOICE 3

Although the

waveform settings are the same for each type of waveform

17) represents

the start

for a triangular

for each VOICE and WAVEFORM combination

CONTROL

REGISTER

54276
54283

54290

TRIANGLE SAWTOOTH PULSE

17/16
17/16
17/16

Note Start

33/

32

33/

32

33/

32

/

Stop Numbers

65/64
65/64
65/64

control registers are different for each voice the

83

NOISE
129/128
129/128
129/128

.

To see how

this works, look at

Lines

85 and 90 in the

musical scale

program. In this

program, immediately

after setting

the frequency in Line 80, we set the
CONTROL SETTING for VOICE 1 in Line 85 by POKEing 54276,17. This
turned on the CONTROL for VOICE 1 and set it to a TRIANGLE

WAVEFORM (17). In Line 70 we POKE 54276,16, stopping the note. La­ter, we changed the waveform start setting from 17 to 33

SAWTOOTH WAVEFORM and this

gave the scale a

"harpsichord" effect.

to create a

See how the CONTROL SETTING and WAVEFORM interact? Setting the
waveform is similar to setting the volume, except each voice has its own
setting

and instead

of POKEing volume

levels

Next, we'll look at another aspect of sound . . . the ADSR

3. ATTACK/DECAY SETTING

CONTROL SETTING not only defines the waveform but it also activates

the ADSR

, or ATTACK/

DECAY/SUSTAIN

MODORE 64. We'll begin by looking at the ATTACK/DECAY setting. The
following chart shows the various ATTACK and DECAY levels for each

voice. If you're not familiar with the concepts of sound attack and de-

cay, you might think of "attack" as the rate at which a note/sound arises
to its MAXIMUM VOLUME. The DECAY is the rate at which the note/
sound falls from its highest volume level back to the SUSTAIN level. The
following chart shows the ATTACK/DECAY setting for each voice, and the
numbers for each attack and decay setting. Note that YOU MUST
COMBINE ATTACK AND DECAY SETTINGS BY ADDING THEM UP AND
ENTERING THE TOTAL. For example, you can set a HIGH ATTACK rate
and a LOW DECAY rate by adding the high attack number (64) to the
low decay number (1). The total (65) will tell the computer to set the high
attack rate and low decay

by adding them together (128 + 64 + 32 + 16 = MAX. ATTACK RATE
of 240).

-As we mentioned before, the ADSR

/

rate

. You can also increase the attack rates

we're defining waveforms.

RELEASE

feature of the COM-

feature.

ATTACK/DECAY RATE SETTINGS

.

4

4

4

LOW LOWEST

2

2

2

ATTACK/DECAY HIGH MEDIUM LOW LOWEST HIGH MED

SETTING ATTACK ATTACK ATTACK ATTACK DECAY DECAY DECAY DECAY

VOICE 1 54277
VOICE 2

VOICE 3

54284

54291

128

128
128

64
64

64

32

32

32

16
16

16

8

8

8

If you set an attack rate with no decay, the decay is automatically

zero, and vice-versa. For example, if you POKE 54277,64 you set a

medium attack rate with zero decay for VOICE 1. If you POKE 54277,66

you set a medium attack rate and a low decay rate (because 66=64+2

and sets BOTH settings). You can also add up several attack values, or
several decay values. For example, you can add a low attack (32) and a

84

•

medium attack (64) for a combined attack rate of 96, then add a
medium decay of 4 and . . . presto . . . POKE 54277,100.

At this point, a sample program will better illustrate the effect. Type

the word NEW, hit HIT M

-L and type in this program and RUN it:

,

5 FOR

10 PRINT

L=54272TO54296:

"HIT ANY KEY" --

POKE L

0:NEXT(

20 POKE54296,15 <

30 POKE54277,64 <

40 P0KE54273
60 GETK$

:

70 POKE54276,17:FORT

80 POKE54276,16:FORT

17:P0KE54272,37 E

,

IFK$=""THEN60 <-

=1 T0200:NEXT

=1T050:NEXT <

90 GOTO2O E

Here, we're using VOICE 1 to create one note at a time

MEDIUM ATTACK
ATTACK/

rate

DECAY setting with the number 64 activates a MEDIUM attack

.

The result sounds like someone bouncing a ball in an oil drum.

Now for the fun part. Hit the

type the word LIST and hit

RATE and

ZERO DECAY.

®r

^ID

. Now type this line and hit

The key is Line 40. POKEing the

key to stop the program, then

(the new line 40 automatically replaces the old line 40):

40 POKE 54277,190

Duration the note plays.

Screen message.

Set volume at highest level.

Set Attack/Decay.

Poke one note

Check the keyboard.

Set Vhvefonn control (
Turn off settings.
Loop back

into VOICE 1.

triangle).

and do it again.

. . .

with a

Type the word RUN and hit to see how it sounds. What we've

done here is combine several attack and decay settings. The settings

are: HIGH ATTACK

+

HIGH DECAY (8) + MEDIUM DECAY

128) + LOW ATTACK(32) + LOWEST ATTACK (16)

(

(

4) + LOW DECAY

(2) = 190.

This effect sounds like a sound an oboe or other "reedy" instrument

might make. If you'd like to experiment, try changing the waveform and
attack/decay numbers in the musical scale example to see how an

"oboe" sounds. Thus . . . you can see that changing the attack/decay

rates can be used to create different types of sound effects.

4. SUSTAIN/RELEASE SETTING

-Like Attack/Decay, the SUSTAIN/

RELEASE setting is activated by the ADSR/WAVEFORM Control. SUSTAIN/

RELEASE lets you "extend" (SUSTAIN) a portion of a particular sound, like
the "sustain pedal" on a piano or organ which lets you prolong a note.
Any note or sound can be sustained at any one of 16 levels. The

SUSTAIN/RELEASE Setting may be used with a FOR . . . NEXT loop to

85

determine how long the note will be held at SUSTAIN volume before

being released. The following chart shows the numbers you have to
POKE to reach different SUSTAIN/RELEASE,

SUSTAIN/

SUSTAIN

/

RELEASE HIGH MEDIUM LOW LOWEST HIGH MED

CONTROL SETTING SUSTAIN SUSTAIN SUSTAIN SUSTAIN RELEASE RELEASE RELEASE RELEASE

VOICE 1
VOICE 2
VOICE 3

54278
54285
54292

128
128
128

RELEASE

64
64 32
64 32

32

RATE SETTINGS

16
16
16

rates.

.

LOW LOWEST

8
8

8

4
4
4

2
2
2

As an example, if you're using VOICEI, you can set a HIGH SUSTAIN

LEVEL by typing: POKE 54278,128 or you could combine a HIGH SUSTAIN

LEVEL with a LOW RELEASE RATE by adding 128 + 2 and then POKE
54278,130. Here's the same sample program we used in the ATTACK/

DECAY section above . . . with a SUSTAIN/RELEASE feature added.
Notice the difference in sounds.

5 FORL=54272T 054296: POKE L,0: NEXT

10 POKE54296,15
20 POKE54277,64
30 POKE54278,128 'E­40 P0KE54273,17:P0KE54272,37 ^­50 PRINT"HIT ANY KEY" <
60 GETK$:IFK$=" "THEN60 E
70 POKE54276,17:FORT=1T0200:NEXT
80 POKE54276,16:FORT=1TO50:NEXTf
90 GOTO60

,Duration the note plays.

Set volume at highest level.

Set Attack/Decay.

Set Sustain/

POKE one note into VOICE I.

Screen message.

Check the keyboard.

Set VAoveform control (
Torn off settings.
Loop back and do it again.

Release

triangle).

In Line 30, we tell the computer to SUSTAIN the note at a HIGH SUS-

TAIN LEVEL (128 from chart above) . . . after which the tone is released

in Line 80. You can vary the duration of a note by changing the "count"
in Line 70. To see the effect of using the release function try changing

Line 30 to POKE54278,89 (SUSTAIN = 80, RELEASE = 9).

5. CHOOSING VOICES AND SETTING HIGH/LOW FREQUENCY

SOUND VALUES

-Each individual note on the Commodore 64 requires
TWO SEPARATE POKE COMMANDS . . . one for HIGH FREQUENCY and
one for LOW FREQUENCY. The MUSICAL NOTE VALUE table in Appendix
M shows you the corresponding POKES you need to play any note in the

86

Commodore 64's eight octave range. The HIGH and LOW FREQUENCY
POKE COMMANDS are different for each VOICE you use-this allows

you to program all 3 voices independently to create 3-voice music or

exotic sound effects.

The HIGH and LOW FREQUENCY POKE COMMANDS for each voice
are shown in the chart below, which also contains the NOTE VALUES for
the middle (fifth) octave.

VOICE NUMBER POKE

& FREQUENCY NUMBER

VOICEI/HIGH

VOICEI/LOW

VOICE2/HIGH

VOICE2/LOW

54273

54272

54280

54279

VOICE3/HIGH 54287

VOICE3/LOW 54286

C

C#

34

36 38 40 43

75 85

34

75

34

75

126

36

126

85

36 38

85 126

3

SAMPLE MUSICAL NOTES

D

D#

E

F

45

200

440

200

40

200

198 127

52

43

45

52

198

43 45

52 198

127

127

F#

48

48

48

51

97,

51

97

51

97

-FIFTH OCTAVE

G G#A

54 57

172 126

111

54 57

172

111

54

57

172

111

A#

61

64

188 149 169

61

64 68

126

188 149 169

61

64 68

126 188 149

As you can see, there are 2 settings for each voice, a HIGH FRE-

QUENCY setting and a LOW FREQUENCY setting. To play a musical note,

you must POKE a value into the HIGH FREQUENCY location and POKE

another value into the LOW FREQUENCY location. Using the settings in
our VOICE/FREQUENCY/NOTE VALUE table, here's the setting that plays
a C note from the 5th octave (VOICED:

POKE 54273,34:POKE 54272,75.

The same note on VOICE2 would be:

POKE 54280,34:POKE 54279,75.

B

C

C#

72

68

72

72

169

Used in a program, it looks like this:

5 FORL=54272TO54296:POKE L,O:NEXT

10 V=54296:W=54276:A=54277:

S=54278:H =54273:L=54272

20 POKEV,15:POKEA,190:POKES,

30 POKEH,34:POKEL,75
40 POKEW,33:FORT=1TO200:NEXTstart note, let it play
50 POKEW,32 ( stop note

87

89

^- POKE

Set numbers equal to letters.

,

.oIume

woveform

, ottac

k/de<ay.

POKE hi/lo freq. notes

PLAYING A

The following program can be used to compose or play a song (using

VOICEI). There are two important lessons in this program: First, note

how we abbreviate all the long control numbers in the first line of the
program ... after that, we can use the letter W for "Waveform" instead

of the number 54276.

SONG ON THE COMMODORE 64

The second

lesson

concerns the way we use the DATA. This program
is set up to let you enter 3 numbers for each note: the HIGH FREQUENCY
NOTE VALUE, the LOW FREQUENCY NOTE VALUE, and the DURATION

THE NOTE WILL BE PLAYED.

For this song, we used a duration "count" of 125 for an eighth note,
250 for a quarter note, 375 for a dotted quarter note, 500 for a half
note and 1000 for a whole note. These number values can be increased

or decreased to match a particular tempo, or your own musical taste.

To see how a song gets entered, look at Line 100. We entered 34
and 75 as our HIGH and LOW FREQUENCY settings to play a "C" note
(from the sample scale shown previously) and then the number 250 for a
quarter note. So the first note in our song is a quarter note C. The
second note is also a quarter note, this time the note is "E" ... and so
on to the end of our tune. You can enter almost any song this way,
adding as many DATA statement lines as you need. You can continue the
note and duration numbers from one line to the next but each
begin with the word DATA. DATA-1,-1,-1 should be the last line in your
program. This line "ends" the song.

Type the word NEW to erase your previous program and type in the

following program, then type

RUN to hear the song.

line must

MICHAEL ROW THE BOAT ASHORE-1 MEASURE

2 FORL=54272TO54296
5 V=54296:W=54276:A=54277

PH =54275:PL=54274

10 POKEY,15:POKEA,88:POKEPH,15:POKEPL,15:POKES,89

20 READH:IFH=-1THENEND
30 READL
40 READD
60 POKEHF,F:POKELF,L:POKEW,65
80 FORT=1 TOD:NEXT:POKEW,64
85 FORT=1TO50:NEXT

POKEL,O:NEXT

:

:

HF=54273:LF=54272:5=54278:

88

90 GOTO10

100 DATA34
105 DATA250
110 DATA51
115 DATA 1000

120 DATA-1,-1,-1

CREATING SOUN

Unlike music, sound effects are more often tied to a specific pro­gramming "action" such as the explosion made by an astro-fighter as it
crashes through a barrier in a space game . . . or the warning buzzer in
a business program that tells the user he's about to erase his disk by

mistake.

You have a wide range of options available if you want to create
different sound effects. Here are 10 programming ideas which might
help you get started experimenting with sound effects-

1. Change the volume while a note is playing, for example to create
an "echo" effect.

2. Vary between two notes rapidly to create a sound "tremor."

3. Waveform . . . try different settings for each voice.

4. Attack/Decay . . . to alter the rate a sound rises toward its "peak"
volume and rate it diminishes from that peak.

5. Sustain/

and rate it diminishes from that volume.

6. Multivoice effects . . . playing more than one voice at the same
time, each voice independently controlled, or one voice playing

longer or shorter than another, or serving as an "echo" or response

to a first note.

7. Changing notes on the scale, or changing octaves, using the values

in the MUSICAL NOTE VALUE table.

8. Use the Square Waveform and different Pulse Settings to create
different effects.

9. Use the Noise Waveform to generate "white noise" for accenting
tonal sound effects or creating explosions, gunshots or footsteps.
The same musical notes that create music can also be used with the

Noise Waveform to create different types of white noise.

10. Combine several HIGH/LOW frequencies in rapid succession across
different octaves.

11. Filter . . . try the extra POKE setting in Appendix M.

,

75,250

,

,

97,500

Release

,

57,172,250

,

0,0,125

51,97,500

,

,

43,52

. . . to change sustain to volume of a sound effect,

250,51,97,375

43,52

,

EFFECTS

D

,

250,51

43,52

,

,

97,250

,

125,51,97

,57,172

89

I

SAMPLE SOUND EFFECTS TO TRY

The following programs may be added to almost any BASIC program.
They are included to give you some programming ideas and demon­strate the Commodore 64's sound effect range.

Notice the programming shortcut we're using in Line 10. We can
abbreviate those long cumbersome sound setting numbers by
them as easy
that these easy to remember LETTERS can be used instead of those long

numbers

Frequency
letters instead of numbers in our program
shorter
spot.

,

-

to-use letters

.

typing faster

, V = Volume, W=Waveform, A=Attack/Decay,

Here

(VOICE]), and L=

,

and the sound settings easier to remember and

numeric variables). Line 10 simply means

(

Low Frequency

(VOICE]

. . .

). We then use these

making our program

DOLL CRYING

10 V=54296:W=54276:A=54277: H=54273:L=54272

20 POKEV,15:POKEW,65:POKEA,15

30 FORX=20OTO5STEP
40 FORX

50 POKEW,O

=

150TO5STEP-2:POKEH

-

2:POKE H

,

40:POKE L,X:NEXT

,

40:POKEL

,

X:NEXT

defining

H=High

S

•

SHOOTING SOUND

USING VOICE1

,

...

VOLUME

V=54296:W=54276:A=54277:H =54273:L=54272

10

FORX= I5TOOSTEP-1:POKEV,X:POKEW,129:POKEA,

20

15:POKEH,40:POKEL,200:NEXT

POKEW,O:POKEA,0

30

90

NOISE WAVEFORM,FADING

S

S

•

0

01