|Routine to get next non space|
character.C flag set if valid
|Print HL in decimal||––||F9AD|
|Amount of memory||stored @||10DA|
|Ctrl ‘0’ flag||stored @||1045|
|End of program||stored @||10D6|
|Start of text||starts @||10F9|
|Line length||stored @||1042|
|Location of text||stored @||1049|
|Line buffer||stored @||1048|
While I was disassembling the BASIC I found a number of things that aren’t
mentioned in the manual such as ctrl ‘O’. “What is ctrl ‘O’?”, I hear you ask. It
suppresses output (long word ‘suppresses’). Can I hear shouts of, “Useless!”? Well its
not, because a flag is stored in the workspace. Poke the flag and you suppress output,
useful for passwords and the like. Mind you this only works while the BASIC has
control of the input buffer. This occurs when the input is in the NAS-SYS or NASBUG X0
mode, or during an INPUT statement.
Ever noticed how slow BASIC is on starting up? Take a look at locations FCCDH
through to FCD4H these locations form a routine which is simply a delay. At this point
I will grit my teeth and hope that I’m right and that it is all it does.
Ever wondered why you can’t single step BASIC? It’s because it changes the NMI
jump vector in the workspace. If you want to single step BASIC ignore any calls to
FEBBH because that’s where it changes. Ok so it changes the NMI jump so what does it
change it to? It changes it to the break function, so if you can generate an NMI you
can use it as a break key. How do I generate an NMI ? Simple connect a push to make
switch between pin 4 of the keyboard and ground. (Nascom 2 only. Ed.)
Hope that this helps you,
Nutty Nascom Owner.
(– are they legal !?)
Two little homilies (I’ve just looked that up in the dictionary, it said,
“Pedious moralizing discourse.”, I didn’t know how close my choice of words was). Both
of these concern the design and/or testing of new equipment, and both are printed here
for those just on the point of desparation.
The first came from my father, who spent a lot of my early childhood
constructing television sets out of war surplus radar sets. As I remember, they had
long persistence green screens. When I first cut my teeth on a soldering iron (and
that hurt), he told me, “It will always take so long to build a thing, and then at
least five times as long to make it work.”. That one has always stood me in good stead
when doubtful homebrew circuits didn’t do as expected. I must admit it’s preserved my
sanity, if only in a perverse desire to prove my old man wrong.
The origin of the second is more obsure, I may have even invented it myself. I
certainly use it in the shop when customers present themselves with a handful of dud
chips. It goes as follows. “One dud is too bad, change it, the second is coincdence,
three is ‘Hmmmm’, and four or more, is ‘you’ve done something wrong mate’.” This one
proved it’s worth only yesterday, when a customer came in with no less than eight
“dud” CD4028s. Now eight is stretching even my credulity a bit far, so after applying
the above rule, it turned out that he’d forgotten to connect the power rails to any of
the chips. QED.