How Much of CP/M's Design Ended Up in MS‑DOS?
5 days ago
- #Operating Systems
- #MS-DOS
- #CP/M
- MS-DOS was designed to be API compatible with CP/M but did not copy its source code.
- Gary Kildall accused MS-DOS of borrowing CP/M's internal design, though specifics were vague.
- Tim Paterson defended MS-DOS, stating it implemented CP/M's API but had different internal workings, like the FAT file system.
- The controversy includes claims about MS-DOS adopting CP/M's BIOS-style component layout and system call mechanisms.
- Paterson acknowledged using CP/M's API but denied reverse-engineering CP/M's internals.
- MS-DOS used INT 21h for system calls, differing from CP/M's CALL 5 mechanism, due to 8086's built-in interrupt instruction.
- The component layout of MS-DOS, including the BIOS-like I/O system, was inspired by CP/M's design.
- The dispute highlights the reuse of software designs, with both CP/M and MS-DOS borrowing ideas from earlier systems.
- Both CP/M and MS-DOS are now part of computing history, with contributions from both Kildall and Paterson.