This is like an O'Reilly Cookbook for C64/C128 assembly language programming. Lots of concrete CIA IRQ/NMI code snippets. For those who like to learn from many small, complete examples, track this one down. (Note: This book should not be confused with COMPUTE!'s Machine Language Routines for the Commodore 64 (isbn 0942386485), a book that contains many COMPUTE! magazine articles, in which the interesting ML details are usually hidden in pages of instruction-opaque BASIC data statements. It's way less awesome.)