A collection of assembly language include files for atasm for Atari DOS, OS, custom chips, etc.
(atasm -- all the joy of the Mac/65 assembler with none of the line numbers.)
I'm sure someone else has done a better version of includes. This is what I need for what I have coded. Primarily this is the standard custom chips, OS shadow values, CIO, and common interfaces/vectors in the OS. Not so much here for lower level Serial I/O and device-specific functionality.