Table Of Content“MACHINE
LANGUAGE
ROUTINES
=== FOR THE ———=
COMMODORE
64/128
{ A contin icon of oe han 2 0200
machine language rout A
inne tins to aces cer a
des and Kemal routines sting rts
much more. The ial reference
‘A COMPUTE! Books Pubication $18.95,
Machine
Language
Routines
or the
Commodore 64 and 128
Todd D. Heimarck and Patrick Parrish
COMPMTE Publications inc.
Greensbor » Carolina
‘Cops 1957, COMPUTE! Plains, A rights reve
Reyeoucton o trsaton oan prof tis work beyond th peri
Sica yt er URLS apy Aan pin of
2S copyright owner snl
ein the Und Sate of Areca
10987654321
Teeepurast pete Crean Secor ne tan od pees bes oe
‘respi pel tho ty tt hn nd ty en
[COMPUTE Pulao ne. Pot Oe Bon 3406, Greensboro, NC 27403 (19)
‘tle 6 nd tt asada of Comes Besant
Contents
Preface ..
Introduction
Opcodes
ROM Kernal Routines
The Routines
Index by Topic
Index by Label
Disk Coupon
Preface
“This book isa sich lisrary of more than 200 machine language
routines for programmer 9 learn from and sein ther Own
Programe. The progsame in ths book cover a wide range
+ Character input and output
+ Sprite definiton and movement
Highvresoltion graphics
Sorting and searching lists of information
"ending an wing disk files
+ Combining BASIC snd ML programs
‘Printer routines
{Addition subtraction, multiplication, and division
‘Conversions between characer and screen codes
‘Random suber generation
Shity clock and Ynte-of day clock routines
5 Using tnterrapes and vectors
5 Custom characters for 40-and 80-column displays)
*Sound eects and music
‘These ae jut few of the outines youl ind in this
books Neasly every subroutine is listed with a sample program
that astrates how it works. You eam study the subroutine by
self or sce how i's used inthe context of rel program
(One of the best ways to lean machine language et
study other people's programs. If you can ee Now someon
flee got the Eompater todo something ike moving spats,
Printing a score sorting Ist or whatever, you can face
Through the steps and gan a beter understanding of the
technique
Bul most magazines and books publish machine language
(ott) as 3 series of numbers in DATA statements. You dont
Team mach about machine language fom ping in clstes of
numbers. You could use an Mic monitor to daastemble the
program. but when you're faced with a sea of JSRe and BEQS
Asha aways obvious what's going on in a program
"The programs include a wealth of comments that take you
step hy step hough the various stages of each routine: sing
‘ap the variables, calling the routine: and handling the results
se on win by oh
om bebe DaSenete
paaeerepegece ey ae
iret tat rane
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Todd D. Heimarck
Patrick Paresh
‘Al the source code in this book is ready to type in and
‘assemble, There is also a disk available from COMPUTE!
Books which includes all the source code from the book
(no object code is included on the disk). An assembler is
required to use the disk, To purchase the disk, use the
‘coupon in the back of the book or call 1-800-346-6767 (in
New York 212-887-8525).
Introduction
‘The paradox of machine language is that i's both simpler
znd ove comp than High tevel language suchas BASIC
or Pascal
Nachine language (ML) i simpler because a program con-
sits of many very smal slope, LDA #10 pus the marber 10,
inthe accuntuletoe. STX SC1I5 takes the number inthe Xreg-
iter and sores it in memory locaion SC1IS: you sty
Sing line fom fot and powerfl machine language pro
fem, youll ously soe tat ol very emu happens Now
Soteidra BASIC command auch as SPRITE of tne Com
tmodore 12, With ove comand, you can fur a opie Ov et
{coir pron, and expansion, end pt in lbeeor
tmode. Compared to the Sparta ineacion st of Mi, BASIC
Ihe ciker ch ore combate language
But eventhough the insctons are small and simple,
puting together a working ML program is often more complex
ian wnting a BASIC program. fyeu make 2 mistake, chances
are good Dat the propa wil go into an endless lop (or
‘ose, the computer wl cash. Thre are po convene error
Sheseages to tel you what ou did wrong, Youre rexponaile
for betping track of your own varabien nd you've expected
to understand some ofthe archectire of the Computer—how
shearing hip and te gator wor
Some people find MIL quite easy Others srg to learn
ie Either woyrove Rope youl dcover wwe uae viet i
thee page.
What You'll Find Here
‘This book is divided into three major parts: the instruction set,
‘the Kernal routines, and the machine language routines.
‘The instruction setlists each 6502 machine language op-
eration, with an explanation of what it does and which fags
are affected. The 6802 family of chips includes the 6510 in the
64; the 8502 in the 128; and the 6802 in the VIC-20, Atari
400/800, and original Apple Il. The ML instructions listed are
common to all of these computers. (Incidentally, if you pro-
Introduction
gram on these othe 6502-based computers, you may be able
fo tranalate some ofthe rostines in this tock forthe Vics
Atari Appa) The inracton wt conn the bling
blocks of ME programming. H you're a beginner, jou may
want to Took dvough ths section fist Even if youre an cd
pro, you'll need Yo fefer to thi let ocasonall,
‘The next section of this book "ROM Kern Routines"—
lists the Kemal routines (which are common fo all eight bt
Commodore computers, including the VIC, Pls/4, 6 and
128). Note the duliberate misepelling of what othet computer
manufacturers call kerelrostines. Te Kernal is block of
Imemory that uses a standard jump tale to make it easier to
Program on diferent brands of Commodore computers. ror
Example, the rostine that pints character i found at dit
ferent locations onthe 64nd 126, but the standard entry
point for the Kemal CHROUT routine is the same (SFPD) on
oth computers This means the line LDA 65. JSR $FVD2 wil
‘work the same on both computersit print the letter A’on
the screen Indeed, i slao rks on the VIC-20, the Plas/l,
ana the 16. We've indsbaed to Otie Couper forgiving ts per
mission to reprints portion of his Mapping the Cmmtsore 128
(COMPUTE! Books, 1986) that explain Mow the Kernal
fovtines work
he inporane of he Kel routines connate over
emphasized To open a dak file, you cal the Kemal routines
SETLIS, SETNAML and OPEN, (Ste the enses under OPENFL
or READFL for examples) It these routines weren't avaliable,
1 would be quite difelt to red fom or write fo disk fle
nd have 1 write your own disk operating system, with
Toutines to apin the dick. ove the read/wate head ta given
tector, ead Bytes one at atime, and s0 on
The tied and largest part of the book is the cllaction of
ML routines. Each subroutine is listed aiphabeticaly by labo
In some cases, the entre program is the subroutine. However
the routine usually pt inthe conten of a framing program
wtkich lustates how fo setup and eal the given stteoutine
(marked by bold type). When a routine appear elsewhere
the Book, hs label appears in blatace type
What You Won't Find Here
‘The book is big, but we couldn't include everything. One
thing you won find is an explanation of how to begin
programming in ML. If you're a beginner, you'll find useful
2
Introduction
cxamples and programs here, but you may also want to lok
into tio books fr beginners: Machine Latguage for Beginners
by Richard Mansfeld (COMPUTE! Books) snd Machine Lan
sage by Jim Buttereld (Brady Books). Mansfeld’ book takes
& stare approach. relating machine language ietrctons fo
their BASIC counterparts. Ifyou know how 8 FOR NEXT foop
works in BASIC, ths book shows you how to do the same
thing in ML. Buterld' book approaches ML more from the
hardvare viewpoint espalning wht hppeing iad he
computer while an MI. progretn is running, We Nighly recom
mend both books. = oy
When you're writing programs forthe 64 and 128, i's
necessary 1@ understand something about how memory i oF
farised™which sero-page locations are avalasle: which ROM
FPutines are useful: how the registers ofthe support chips con-
tel video, input/outpt, and sound. For gencal intocuction
10 these tops, Commodore's two programmers slerence
ides are excellent. The 64 version is published by Howard
sm the 128 version comes from Bantam Books, For more
detail, Mapping the Commodore 64 by Sheldon Lacon and
Mapping the Commodore 128 by Orie Cowper ae esenil
(both published by COMPUTE! Books) infact i you buy
nly ane other machine language book, get the mapping took
for your computer. We ale recommend Anatomy of te Com
Inodore 64 and 128 BASIC 7.0 Internat (Abacus Books). Both
Tooke feature commented deasembler of the BASIC ROMs.
The Routines
ach machine language routine has label upto sx ltrs
Jong. Following the labels a more desciptive name tat tll
yolintat the tine do, fr sample, SQROOT Clcaat
ihe imeger square oot ofan Integer value
Below Ge label ard name, youl se one or two par
graphs that touch on te main points ofthe routine, with
fxamples of where you might see the routine or summary of
fowl works
Neat isthe prototype, whichis something like a flowchart,
converted to insracions writen in Engis, Ist the ndid=
‘al steps followed by the subroutine ad points out the var
‘bles and memory used within the routine. There are usually
three step covered in the prototype: hw to set up, how the
routine work, and how the esl are handed
