a E i - Commodore Is Awesome

screen with a joystick is given and this
is used to illustrate some of the points.
Soft-scrolling of the screen
(moving it up one pixel at a time) is
dealt with briefl y, though again in
enough detail to give most programmers
the information that they require
and then it's on to the raster-interrupt.
For those of you not sure what this is
then I suggest that you go and buy the
hook, for those of you that do then you
will be interested to learn that scrolling
the screen is dealt with in detail
complete with a program that allows
you to scroll teat on the screen with a
joystick. All programs are given in
both hex-dump format and assembly
code when necessary, this means that
you can read the assembly code to find
out what the program is doing.
Music is the heading of the next
chapter. getting your C16 and Plus/4
to play both in Basic and Machine
code is covered. Firstly we have a Basic
program that shows you just what is
possible from Basic. Following this is a
program illustrating how to make your
computer play music on interrupts.
This is one instance in the book that I
felt that the author could have
produced a better explanation of the
program and how to use something
5.3 TUR80 MOCE FOR THE C 16
BOOR REVIEWS
similar in your own programs.
The Book then enters the world of
machine code programming. The first
section, entitled introduction to
Machine Code, tries to teach machine
code in only 13 pages.
realise that this isn't possible and
that whole books have been written on
the subject of machine code. However,
this section is excellent, it probably
won't make anyone a machine code
genius but it will stop people from
baulking at the sound of the term and
will show them, again through
examples, how to print something to
the screen, how loops work etc.
A full description of the 7501 processors
commands is given with the
commands in alphabetical order with a
description, their form of addressing,
the assembler format, the number of
bytes it occupies and how many
machine cycles it takes to function.
A description on how to use the
computers in-built kernal routines is
given, together with a list of them all.
Now you have no excuse for not
knowing how to LOAD and SAVE
programs in machine code, or how to
get a character from the keyboard in a
machine code program, all this and
much more is dealt with again in an
For all those, who think the C 16 is too slow., we can show you a
trick with which it will become about 30% faster. Since we live In a
Turbo age, we simply call It the Turbo Mode. The trick is to switch
the screen off. Of course this is impractical if you want to create
Graphics and see them at the same time, but not if you have
mathematical problems to solve, where you dbn't always have io look
at the screen. The speed advantage arises from the fact that the
Video-Chip TED doesn't slow down the Micro Processor anymore once the
screen is switched off. A small demo program, fi rst in Turbo MOde and
then in the normal mode, will Show you how it works and how much time
you can save.
100 POKE 65286,PEEX(65286) AND 239
110 GOSUB 150
120 POKE 65286,PEEK(65286) CC 16
130 GOSUB 150
140 END
150 1%.,.TI
160 FOR 1=1 TO 1000
170 : B=84.1
180 NEXT I
190 PRINT USING u
fi200 t RETURN . 0 4
0
;(TI-T)/60
YOUR COMMODORE january 1987
93
extremely clear way with the name of
the routine being given, its address in
the Kernal what registers are used etc.
all being given.
An excellent memory map of the
computers is given, extremely important
if you wish to use machine code.
The map could have done with some
examples of how to use the various
addresses to your own benefit as I am
afraid that beginners to machine code
will find the function of many of the
addresses totally baffling. The more
experienced programmer will no
doubt find all of the information that
he requires though and this section will
undoubtedly become one of the most
thumbed in the book. Maps of the
TED chip and KERNAL jump table
are also given which again will come in
extremely useful,
If you have ever used a C64 then
you will fi nd the comparison of the
memory maps of the CI6 and C64
extremely useful, I know I did when I
needed to fi nd out where the border
colour was stored on a C16. Its 53280
on the C64 but where on earth is it on a
CI6? This comparison will show you.
The fi nal section of the book
provides the reader with some machine
code utilities ranging from a joystick
scan routine to an OLD (restoring a
NEWed program) routine. Accompanying
this article is a sample section
from this chapter of the book, 1 hope
that this gives you a good idea of what
is possible with this book.
Verdict
must admit I have been waiting for a
book like this on the CI6 and Plus/4
ever since the machines were fi rst
launched. OK so the book isn't perfect
and there is room for a lot of improvement.
However, the book does provide
the advanced programmer with all of
the reference material that he should
ever require.
If you are into serious programming
than I would suggest this is one
book that you must go out and buy, it
will become an invaluable, if not the
most important book in your
collection.
Touchline
Name: (16/Phis 4 Reference Book
Price: 1
. Anco Software, 4 West Gate House,
7.95 Spital Street, Dartford, Kent, DA 1
P2E11. u bTeL
0322 92513/92518 ISBN: 2-
717-00101-5
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