In a collaborative effort that celebrates the history of personal computing, Microsoft, in partnership with IBM, has released the source code for MS-DOS 4.0 on GitHub. This marks a significant event in the tech world as it brings to light a pivotal chapter in software development over 35 years after the operating system's debut.

Historical Context of MS-DOS 4.0

MS-DOS 4.0, a product of the early collaboration between IBM and Microsoft, played a crucial role during the era of their joint OS/2 development. Known for its enhanced support of FAT16 hard disk partitions beyond 32 MB and the introduction of the MS-DOS Shell, MS-DOS 4.0 represents a key evolution in the DOS series, which was eventually overshadowed by the more user-friendly Windows 3.x.

The release became possible when Connor Hyde, a researcher documenting the intricacies of DOS and OS/2's development, contacted Microsoft's CTO, Ray Ozzie. Ozzie discovered the old source code on a collection of floppy disks dating back to 1984. With assistance from Scott Hanselman, Microsoft's VP for the Developer Community, and Jeff Sponaugle, an archivist, the code was digitized and made publicly available.

GitHub Release

The source code for MS-DOS 4.0 has been uploaded to GitHub under the MIT license, making it freely accessible for educational and historical exploration. This release includes not only the OS code but also related documentation and other materials from the era, providing a comprehensive view of its development and capabilities.

MS-DOS GIthub Page.

Technical Capabilities and Legacy

MS-DOS 4.0's release underlines its historical significance and technological innovations at the time. Users interested in the practical applications of this antique software can run the code on machines as old as the original IBM XT or as modern as a new Pentium. It is also compatible with PCem and 86box, two open-source emulators that facilitate the operation of older OS versions on contemporary hardware.

Microsoft has indicated that other versions of MS-DOS, specifically 3.3, 5, and 6, might soon follow in being open-sourced, although some adjustments will be necessary to remove proprietary utilities. This initiative is part of a broader movement to preserve and study the digital artifacts that have shaped today’s computing landscape.

The release of MS-DOS 4.0’s source code is not just a nod to nostalgia but a significant step in preserving the technological heritage that has paved the way for modern computing solutions. It offers both educational insights and a reminder of the rapid pace of technological advancement in the software industry.