Taking a peek at machine code
HAVE you ever wondered what goes on inside your computer or
what this machine code stuff is all about? Well, if you are a
beginner or don't have some idea already then Peeko-Computer will
not help you very much.
It could, however, be a very useful visual aid in a class for
a teacher demonstrating the principles of machine code programming
to the uninitiated.
It is also handy for someone more experienced, enabling the
user to try out short routines without having to suffer endless
system crashes.
Basically, the program allows the user to write and run short
machine code routines — up to 80 bytes — of a simple numerical
nature and see their display on the screen.
The program is available on cassette or disc. I tried out the
cassette version, which was up to Acornsoft's usual high standard
of packaging and ease of use.
The pack consists of a short loader program, the main program
(about 5k), five short demonstration files and a 21 page instruction
manual.
All programs and files loaded perfectly every time and it was
very easy to create, save and load one's own pseudo machine code
routines.
I say pseudo machine code because some of the 20 assembler mnemonics
available in the program - 10 of which can be used at any one
time — were not identical to the 6502 instruction set as used
by the BBC and all were given an arbitary decimal code.
In fact this program avoids hexadecimal altogether, which may
not be a bad idea for the beginner but it does mean having to
learn machine code "properly" all over again.
The routines described in the booklet all worked very well indeed
and the display was perfectly intelligible on a black and white
TV as well as in colour.
The user can single step through a routine and watch the results
appear, as well as run it in fast mode.
A warning though: Scanning through the code with the cursor
can be confusing as individual instructions are often misinterpreted,
giving unexpected mnemonics at the top of the screen.
Overall, Peeko-Computer should be useful to instructors and
those already knowing what machine code is all about, though the
latter may well prefer one of the fully blown monitor programs
with more facilities that are available for the same price.
Mike Mahon
