I got a PET 4032 about a month ago (used these at school and have always wanted one), and I've noticed that a few programs make the screen larger vertically. I'd just re-sized the screen with the pot on the screen's board, then I saw this happen with some software (luckily, it's only the corners of the corner characters that are slightly off the screen when expanded like this), but I wondered what was going on.
I've just found a game that does this and found the command:
PRINT "NH"
The N and H are in reversed video. Usually these are created by opening quotes then doing a control character, but I wasn't sure what creates those, so just types a reversed NH, then put the print around it and the screen flickered and went bigger.
What exactly is this? Is it a documented feature, a hack, something related to the killer poke, an equivalent to a normal poke command?
Is it safe to use?
Is it something that was meant for a different model PET?
If there is a PET forum somewhere that anyone knows of, then please direct me to it.
Can anyone explain this PET command?
Moderator: Moderators
Re: Can anyone explain this PET command?
This is what I found in the PET-FAQ:
http://www.zimmers.net/anonftp/pub/cbm/ ... 20FAQ.html
"The 12" 4000/8000 series PETs allow you to change case by printing
a control character: CHR$(14) - Text Mode CHR$(142)-Graphics Mode
When you issue a CHR$(14) on a 4000/800 series PET the newer display
controller will be adjusted so there is a pixel or two gap between
screen lines. If you do not wish this gap in text mode just
POKE 59468,14 instead of printing CHR$(14)
(if you want the gap in character mode you can issue a ? CHR$(14)
and then POKE 59468,12 to produce the desired effect.)"
The gap ist intentional so text-mode is more readable. Effectively a reverse N is the same as CHR$(14). Not sure what the CHR$(8) (reverse H) does. On the VIC-20 and C64 it disables C=/Shift to switch between charsets, but the PETs do not have a C= key.
http://www.zimmers.net/anonftp/pub/cbm/ ... 20FAQ.html
"The 12" 4000/8000 series PETs allow you to change case by printing
a control character: CHR$(14) - Text Mode CHR$(142)-Graphics Mode
When you issue a CHR$(14) on a 4000/800 series PET the newer display
controller will be adjusted so there is a pixel or two gap between
screen lines. If you do not wish this gap in text mode just
POKE 59468,14 instead of printing CHR$(14)
(if you want the gap in character mode you can issue a ? CHR$(14)
and then POKE 59468,12 to produce the desired effect.)"
The gap ist intentional so text-mode is more readable. Effectively a reverse N is the same as CHR$(14). Not sure what the CHR$(8) (reverse H) does. On the VIC-20 and C64 it disables C=/Shift to switch between charsets, but the PETs do not have a C= key.
- necronom
- Vic 20 Dabbler
- Posts: 91
- Joined: Mon Jul 19, 2010 11:41 am
- Location: Middlesbrough, UK
- Occupation: IT Support
Re: Can anyone explain this PET command?
Thanks for the reply. I've been away, so I've just seen this now.
I've been using 59468,12 or 14, but didn't know about this special text mode. I'll have a look at the link and the other info in the FAQ.
I've been using 59468,12 or 14, but didn't know about this special text mode. I'll have a look at the link and the other info in the FAQ.