Re: Another file question (PET)

From: Nicolas Welte; address is valid for replies (Re:) only! (
Date: 2002-11-19 09:07:21

Marko Mäkelä wrote:

> the 264 series.  The PET and the CBM II require their own versions of the
> programs - the PET even for every ROM version.

 From what I could see in the cbmlink sources, the PET versions "only" differ 
in the OPEN and CLOSE entry point (IIRC), but the zero page locations for 
file handling are the same.

In some Commodore programs, mostly diagnostic programs and the 8250 alignment 
program, I saw a nice technique to make a program run on all PET ROM 
versions: They test for the hardware IRQ vektor high byte which indicates if 
a machine is BASIC 4.0 or not, and then patch the program itself to have the 
correct ROM entry points.

I'm just about writing a small program for the PETs, and it should run on 
*all* BASIC versions, including 1.0. I think the list of zero page locations 
from cbmlink and the little trick from the Commodore diagnostic software 
should enable me to do this with just one binary file.


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