First Microsoft OS

Posted Jul 18, 2013 13:33 UTC (Thu) by anselm (subscriber, #2796)
In reply to: First Microsoft OS by man_ls
Parent article: The 3.11 merge window closes

When Microsoft got started, the BASIC interpreter on many computers doubled up as the operating system since it was the (ROM-based) program that was booted when the computer was switched on and supported commands for operating-system-like tasks. Since Microsoft was behind most BASIC interpreters of late-70s/early-80s vintage computers, that would make those Microsoft's first »operating systems«.

{MS,PC}-DOS, when it was new, was basically a CP/M-80 knockoff for the 8088 CPU. It would probably have been reasonable at the time to do DOS development on CP/M, at least to the degree necessary to get a kernel running on the 8088 machine. It was possible to translate Z80 assembly language to 8088 assembly language automatically, so once you had a call-compatible CP/M-like kernel around you could probably get most of your other stuff across fairly quickly.