best friends are trees). This episode was prepared, edited, re-written and generally
messed around using Naspen. When I finish, I will send it in on tape, which (this is
where it may all go horribly wrong!) the editor will load, format, and print out with
the fabulous Qume Sprint. He can even use his computer to edit in some of those
REMarks of his! (e.g. What does this mean?-Ed)
OK, not the most detailed of reviews, I know. For better detail, see the
review in Practical Computing. Or get some-one to demonstrate it to you and see what
you think. “I’m convinced it’s a major contribution to .....”
SOUND BOARDS THE SNEAKY WAY.
Seen all those adverts for sound boards for Nascoms, but can’t afford them?
Winchester Technology, who make and sell one that uses the AY-3-8910 chip, will sell
you the documentation for a very reasonable amount. So what? says Disgusted of
Tunbridge Wells. The circuit diagram is included in the documentation, which is of a
very high standard in all ways. So you could buy a Winchester Technology prototyping
board to make you feel better about pinching their circuit, and make your own up.
This is more or less what I am up to, except that I have made several changes
to the circuit, to protect the guilty and make it even better, I hope. It will serve
me right if it doesn’t work: more news next episode.
OWNING UP TIME!
Some of the people who wrote to me about mystery opcodes will have had letters
from me in which I suggested that ED 00 does something amazing. In fact, Pierre
Molinaro has kindly written to explain how I made this error. When writing routines to
test such opcodes, it is of course vital to ensure that only the opcode itself caused
any changes you find after it has been executed. Since the monitor single steps the
first instruction when told to ‘Execute’ something, the task will be affected even if
the first instruction is a LD SP,nnnn intended to move the stack to a place where the
memory is known to be clear. I hope that is clear! So start with a NOP when writing
code to test things you think may affect the stack, and you won’t end up with a red
On the other hand, I must assure you that I really did know about ED 6B and ED
78. I was just seeing if you were all concentrating.....
How many of you noticed that Personal Computer world recently wrote “Dave
Barrow is intrigued by the missing instruction codes CB 30 to CB 37...” (February 81,
page 136). PCW wrote about those codes in their second issue, back in 1978 which is
where I found out about them. Can it be that they have memory plague?
PASCAL vs PILOT CONTROVERSY SHOCK PROBE
Actually, no contest, because the two languages are for different purposes. A
long time ago I wrote a sort of Pilot interpreter, but wasn’t very satisfied with it.
It has since been converted to run under Nas-Sys by one of the very few people who
expressed an interest in it. As soon as he is happy with his work, no doubt it will be
sent in for the library. Meanwhile, I have read P.J.Brown’s book, “Writing Interactive
Compilers and Interpreters”, and seen the error(s) of my ways. The whole thing will
have to be done all over again, starting from scratch, in my view. You shouldn’t hold
your breath.... If you can’t wait, there are various Pilot interpreters already
available from magazines, although these are mostly written in BASIC.
What this boils down to is that I have a fair idea how much work there is in
implementing something as complex as Pascal, and hope my “Is Pascal Necessary?”
heading last issue has not caused offence. The paragraph was actually an attack
against the authors of articles that have been padded out to earn more money, and was
written because I was jealous of the fact that they get paid for their articles. (You
want money for this ?! – Ed.)