A CP/M like operating system with no proprietary code #VintageComputing #CPM @hjalfi

David Given posts on GitHub an open source sort-of CP/M 2.2 distribution. What is CP/M you ask?

CP/M (Wikipedia) is Digital Research’s seminal desktop operating system from 1977 that for a decade dominated the personal computer market. It’s of enormous historical value and there’s a vast wealth of programs written for it. It’s even useful today: both to study (as a superb example of sheer minimalism) but also to use; the Z80 is a common target for homebrew computers, and CP/M is the obvious operating system to run on one.

So what is CP/Mish?

CP/Mish is an open source sort-of-CP/M distribution for the 8080 and Z80 architectures (although for technical reasons currently it only works on the Z80).

It contains no actual Digital Research code. Instead, it’s a collection of third party modules which replicate it, all with proper open source licenses, integrated with a build system that should make it easy to work with.

What you get is a working CP/M 2.2 clone consisting of:

  • ZSDOS as the BDOS replacement
  • ZCPR1 as the CCP replacement
  • open source BIOSes for the supported platforms
  • various tools copying the functionality of the standard CP/M tools (some of them written by me)
  • R.T. Russell’s superb BBC Basic, Z80 edition (with integrated assembler)
  • a build system which provides a turnkey cross-compilation system for producing bootable disk images for any of the supported platforms
  • a classic CP/M syntax assembler and linker for cross-compiling ancient source
  • a simple but useful vi-adjacent editor called qe (written by myself)
  • an emulator for testing CP/M binaries
  • source for everything; no binaries are in this distribution
  • bugs

Currently it supports these platforms:

See GitHub for additional information.


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