The original sources of MS-DOS 1.25, 2.0, and 4.0 for reference purposes

Microsoft BASIC for 6502 Microprocessor - Version 1.1

Incompatible Timesharing System

#FreeGEOS source codes. The offical home of the PC/GEOS operating system technology. For personal computing fans. For all developers and assembly lovers. For YOU!

The Touhou PC-98 Restoration Project

MS-DOS Text Editor

SPITBOL x64 provides raw power and speed for non-numeric computation on the x86_64 architecture

Paging operating system for a custom computer architecture

A 16-bit Lisp based operating system.

Code and software "archive" for the CP/M operating system created from 1979-1984

A double-joysticked, shooting, avoiding, crowded future game.

Le-Lisp by INRIA

fast-paced basketball game with new rules

VEDIT ⧸ VEDIT‑PLUS for CP/M V2.33b (04/27/87) source code

Some helpful modifications for Battle Garegga arcade roms

C source code for the Atari ST MIDI-Maze

Quality-of-Life patches for 'Armed Police Batrider' arcade program ROMs

QDOS Classic an experiment of a barebones system