My C64 Programmers Reference Guide taught BASIC, and had a memory map of the computer, documentation for all the custom chip registers, all the opcodes for the 6510 CPU, chip timing diagrams, I/O port pinouts, and a full schematic of the C64 in the back of the manual. I'm sure not all C64s came with that, this was the old-school 2-inch-thick C64 manual that came with early computers, at least mine had it. From this manual I learned assembly language in about a week in 1986 while I was still in junior high school. It was pretty amazing. It definitely ignited my passion for programming, and I still code assembly today on embedded MCUs.

https://archive.org/details/Commodore_64_Programmers_Referen...