Re: Commodore printer codes

From: Robin Harbron (
Date: 2001-08-06 23:36:01

John Phipps wrote:
> Just reading the discussion on control codes, reminded me of a strange bug
> that happened on the PET set up I used to use at school. It was 4032 machine
> linked to a 4040 disk drive and 4022 printer (I think), via an IEEE-488
> cable. I found out somehow, that if you included the graphic symbol '+' (not
> '+' as in plus or minus, but a larger character - chr$(217) or chr$(219), I
> forget which), in a REM statement, the PET would stop printing as soon as it
> reached this, and 'syntax error' would be displayed on the screen. To carry
> on printing, you had to list from the next line down. Never understood why
> this should be. Anyone else come across it?

The BASIC on the C-64 and probably most/all other C= BASICs do this
as well - many (all?) shifted characters cause strange effects during
listings.  You can even cause (on the 64 anyway) the text to change
colour during listings, etc.  I remember reading about this in Ahoy!
or RUN or one of those magazines way back when, and thinking how cool
it was - you could almost write a (simple) program that would be
"executed" when you LISTed it.

This bug has been exploited by more than one elite coder to prevent
people from discovering the secrets of their BASIC program :)
Robin Harbron

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