Posted By
gerliczer
on 2012-08-07
02:28:08
|  Re: Supposed YAPE bug of George
Hi George,
Although it is not a certainity, I have an idea about the nature of the messed up graphic screen. If you are doing what the Graphics Master instruction leaflet tells as it is written then it is maybe the charset data that interferes with your graphics. You see, the graphic screen of COMMODORE BASIC 3.5 resides at $2000-$3F3F in the memory. In the C=16 $3FFF is the end of the memory, therefore programs using character screen usually put the redefined character generator around there, although AFAIR one must be careful doing this because the reset and interrupt vectors may be overwritten. I checked only the BASIC lines 10 and 20, and those are setting the top of memory to $3800. I didn't read the following lines but I'm sure that they set the chargen to this location, after all Graphics Master is a program for the Commodore 16. Unfortunately for you these two things, the graphic screen and the character generator, overlap which is the cause of the messed up screen. At least, this is what I think.
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