I love when multiple hobbies come together. Microsoft has released the source code for their BASIC language for the MOS 6502 processor. I’ve been working on a small 6502 based computer (and old style 8-bit video game console, but that’s more complicated due to the graphics processing), and it’ll be fun to be able to utilize a good BASIC. There’s already some options out there, but it’ll be fun to try out and run the early Micro-Soft BASIC from 1978. Only utilizing 8K of space. I’m probably a bit rusty with my BASIC skills, but I can still get some good things done!

Cool stuff with it, with notes from Bill Gates included. Always neat to see how it was done and how simple and also complex things can be. The ASM is just fun to look through even if you don’t understand all or any of it, the comments are pretty interesting themselves.

This is BASIC M6502 8K VER 1.1, the 6502 BASIC lineage that powered an era of home computing and formed the foundation of Commodore BASIC in the PET, VIC-20, and the legendary Commodore 64. This very source tree also contains adaptations for the Apple II (“Applesoft BASIC”), built from the same core BASIC source. The original headers still read, “BASIC M6502 8K VER 1.1 BY MICRO-SOFT”—a time capsule from 1978.

The version we are releasing here—labeled “1.1”—contains fixes to the garbage collector identified by Commodore and jointly implemented in 1978 by Commodore engineer John Feagans and Bill Gates, when Feagans traveled to Microsoft’s Bellevue offices. This is the version that shipped as the PET’s “BASIC V2.” It even contains a playful Bill Gates Easter egg, hidden in the labels STORDO and STORD0, which Gates himself confirmed in 2010.