Comment by EvanAnderson

3 years ago

If the QDOS/86DOS angle interests you check out a talk that Tim Paterson, of Seattle Computer Products and later Microsoft, gave at VCF West 2019. He describes the history of 86-DOS (licensed to become PC-DOS and MS-DOS). API compatibility with CP/M, was the intention but no code was taken from CP/M.

CP/M was an Intel 8080-based OS. The 8086 was mostly source compatible (but not binary compatible) with the 8080 (i.e. 8080 assembler programs could be assembled targeting the 8086 with only minor changes) and QDOS/86DOS supporting CP/M APIs was to help it fit into this re-assembly workflow.