MS-DOS
Archived source code of early MS-DOS versions 1.25, 2.0 and 4.0, kept for historical reference.
- Stars
- 32.3k
- Forks
- 4.7k
- Licence
- MIT
- Language
- Assembly
- Last update
- 2.5 years ago
- Type
- Other
This repository is archived and no longer maintained.
What it is
This repository holds the original source code for MS-DOS v1.25 and v2.0, plus the source code for MS-DOS v4.00, which was developed jointly by IBM and Microsoft. The v1.25 and v2.0 files were first shared publicly at the Computer History Museum in 2014 and are republished here so they are easier to find and reference. The project is archived and its files are meant to stay static as a historical record.
- Read the original assembly source of MS-DOS v1.25, v2.0 and v4.00
- Cite specific source files in articles, papers or other writing
- Fork the repository and experiment with the code in your own copy
Great for
- Students of early PC operating system design
- Historians and writers who need to cite original MS-DOS source files
- Retro computing enthusiasts who want to read or experiment with old code
- Developers curious how a 1980s operating system was built
Not ideal for
- People who want to install or run MS-DOS as a working system today, since the README describes these as reference sources and does not offer a ready-to-use installer
- Anyone expecting active development, since the repository is archived and the README says pull requests suggesting changes will not be accepted
How to get it
- 1
Clone and build from source
Clone the repository
git clone https://github.com/microsoft/MS-DOS - 2
Run it
- Clone the repository to your computer
- Browse the directories to find the version you want (v1.25, v2.0 or v4.00)
- Open the source files in a text editor to read them
- Consult the README's links to the Computer History Museum page for background on the early releases
- 3
Get the most out of it
- Read the Computer History Museum article linked in the README for context on how the v1.25 and v2.0 files were released
- Fork the repository if you want to make changes, since the upstream project does not accept modification pull requests
- Compare the v1.25, v2.0 and v4.00 sources to see how the operating system changed across versions
Downloads
Strengths
- Original historical source code in one place, with the v1.25 and v2.0 files including compiled binaries
- Released under the MIT License, so forking and reuse are permitted
- Maintainers state the files will stay unchanged, giving a stable reference
Trade-offs
- Archived and static, so no updates or fixes are being accepted upstream
- The README gives no build or run instructions, so using the code requires figuring that out yourself
- Reading assembly from the 1980s generally requires specialized background knowledge
Stats synced from GitHub. The assessment above was drafted with AI from the project's README on 2026-10-29 and may miss recent changes — check the README before relying on a command. MIT licence: free to use, modify and distribute, including commercially, as long as you keep the copyright notice.