Ten years ago, a visit was made to the Laptop History Museum, and thereafter, the collection served as a valuable reference source. This ancient code holds a pivotal place in history and offers a fascinating study of an operational system written entirely in 8086 assembly language, nearly 45 years ago?
As part of our commitment to open innovation, we are proud to partner with IBM on a groundbreaking initiative: immediately releasing the source code for MS-DOS 4.00 under the permissive MIT License. The evolution of DOS’s 4.0 iterations is marked by a complex and intriguing historical narrative, wherein Microsoft collaborated with IBM on select code components, while concurrently developing a separate DOS variant, Multitasking DOS, which ultimately failed to gain significant traction.
Recently, a young English researcher engaged in a correspondence with Ray Ozzie, former Microsoft Chief Technical Officer, regarding several software programs within his repertoire. While working amidst old floppy disks, Ray stumbled upon long-lost beta versions of DOS 4.0, a discovery that seemed fittingly timed given his prior experience at Lotus. In an effort to gain insight into the release of DOS 4 source code, Starfrost contacted the Microsoft Open Supply Applications Office (OSPO) to explore the connections between DOS 4, MT-DOS, and the eventual development of OS/2, seeking to document this pivotal moment in computing history. While some later variants of these Multitasking DOS binaries may be found online, an intriguing discovery suggests that these Ozzie beta binaries are significantly earlier, unpublished, and incorporate the ibmbio.com library.
Scott Hanselman, with the expertise of web archivist and aficionado Jeff Sponaugle, has meticulously digitized these rare disks and carefully preserved the unique printed documentation from the “Ozzie Drop” archives. Microsoft, in collaboration with its partner IBM, recognizes the significance of preserving and celebrating the rich history of computing systems.
Jeff Wilcox and OSPO ventured to the Microsoft Archives, where they successfully located MS DOS 4.00, despite being unable to obtain the complete source code for MT-DOS. In a significant development, this historic software will be released immediately, accompanied by beta binaries, PDF documentation, and digitized disk images. We will proceed to explore the archives, replacing this launch if any additional information is uncovered.
We express our gratitude to Ray Ozzie, Starfrost, Jeff Sponaugle, Larry Osterman, as well as the IBM Open Systems and Platforms Organization associates, along with the developers of digital archaeology software tools, including but not limited to Greaseweazle, Fluxengine, Aaru Information Preservation Suite, and the HxC Floppy Emulator. Above all, we extend our gratitude to the innovative authors of this code, several of whom are remarkably talented professionals who currently work at esteemed organizations like Microsoft and IBM.
To test the software firsthand, we have successfully executed it on both an original IBM PC XT and a modern Pentium, as well as through the open-source PCem and 86box emulators.
About Scott
Scott Hanselman, a multifaceted individual, has transitioned from being a professor to serving as Chief Architect in the financial sector before embracing his current roles as a sought-after speaker, marketing consultant, devoted father, and person living with diabetes, all while working at Microsoft. He’s a struggling former stand-up comedian, part-time hairstylist specializing in cornrows, and an indie author of digital books.
