On 4/4/2025 2:00 PM, Alan Frisbie via cctalk wrote:
Bob Grabau <[email protected]> write: > As my memory serves, there was a class given by the Southern > California Computer Society (SCCS) in which the disassembled the > Altair Basic (not sure if it was the 4k or 8k version) and used the > output of that disassembly for the class. There was a guy who had the > complete annotated (by the class) of the source as printed out copies > in his trunk, which he just handed out to anyone that asked for it. > This was somewhere between 1975-1978 (76-77 most likely) when I was a > member of SCCS. I was part of that disassembly effort and remember it well! I'm pretty sure I still have my copy of it stashed away here. It was a lot of fun. I had been a very early (1974) user of the 8080 at NCR, and this gave me a chance to contribute to the knowledge base. One thing I intend to do with this listing is find a piece of code I worked to disassemble, and read the comments. As I recall, it was part of some error handling. It consisted of a string of three-byte instructions that did nothing important, but if you jumped into the second byte of one, it would (as I recall) act as a two-byte instruction and load a register with an error code. After executing that 2/3 instruction, it fell into the remaining string of three-byte instructions which did nothing of interest. At the end, it would take the value that had been loaded earlier and use it. I was simultaneously impressed and appalled by this space-saving coding technique.
It was quite common back in the day. :-)
I'm disappointed that two printer pages are combined into a single PDF page, as it makes it a bit difficult to read. Still, it is a great window into the minds of Bill, Paul, and Monte.
They sold a book containing a complete, commented dis-assembly of BASIC on the TRS-80 Model 3. I still have my copy of the original book and a Xerox of it my father did for some reason. bill
