Hi-Res Graphics Mind Meld
I read a description of how memory addressing for the hi-resolution screen works three times, each time from a different source. The first two times my brain simply melted before such a byzantine structure. The third time it finally clicked. Surely this had something to do with it being my third attempt to grasp the concept, but I believe even more of it had to do with the third source’s description being the most clear, well-written and well-illustrated.
That third source is “Applesoft BASIC Subroutines & Secrets” by Jeanette Sullivan and David Sullivan. It appears to be an excellent book all around. Below are scans of the two pages on hi-res memory addressing, to assist anyone else puzzling out the same issue:
(click on the images above to download full-size scans)
The book also includes a nifty little BASIC program that will compute the address of any particular block, and lays out the formula the program uses, further reinforcing how the addressing works. Scans of that are below.
(click on the images above to download full-size scans)
In assembly programming news, “Assembly Language for the Applesoft Programmer” continues its traditional of clear writing/explanations and annoying typos in listings. I’m also going through Don Lancaster’s “Assembly Cookbook for the Apple II/IIe” — Lancaster completely skips over the basics (he basically waves his finger at you and says ‘Don’t you dare think of using an assembler until you’ve learned to code 100s of lines of machine language on your own’), but has lots of opinionated advice on surrounding aspects of assembly. I’m learning, slow but steady.