Microsoft Finally Open Sources MS-DOS After Over 3 Decades

Rafia Shaikh
ms-dos open source

Microsoft is making the source code of MS-DOS available to the public after over 30 years. If this sounds like deja vu, the Redmond software maker did offer the source code of MS-DOS as part of a collaboration with the Computer History Museum back in 2014. The 1983 operating system was added to the Computer History Museum in 2013. However, the latest move is part of a "re-release" without the restrictions of the previous effort.

The new repo that was made available on GitHub contains the original source code and compiled binaries for MS-DOS 1.25 and MS-DOS 2.0. All the source files are available for reference and internal experimentation as the company isn't allowing pull requests or modifications to the source.

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MS-DOS follows in the footsteps of Windows 3.0 File Manager

Earlier this year, just before the release of Windows 10 April 2018 Update, Microsoft had also released the source code for the original Windows File Manager that was introduced with Windows 3.0. Now awaiting the release of Windows 10 October 2018 Update, it appears the company is again taking us down the memory lane.

Microsoft said that it put MS-DOS on GitHub as it offers more convenience. Not to forget that Microsoft acquired GitHub in June for $7.5 billion. Senior Program Manager Rich Turner wrote in a post last week (via ZDNet).

Today, we're re-open-sourcing MS-DOS on GitHub. Why? Because it's much easier to find, read, and refer to MS-DOS source files if they're in a GitHub repo than in the original downloadable compressed archive file.

Turner added that the "source will be kept static" and requested everyone not to "send Pull Requests suggesting any modifications to the source files!"

Windows maker - currently in news for its upcoming line of Surface devices and a brand new version of Windows 10 - also added some interesting facts about the operating system:

  1. All the source for MS-DOS 1.25 and 2.0 was written in 8086 assembly code
  2. The source code for the initial release of 86-DOS dates from around December 29th 1980
  3. The MS-DOS 1.25 code dates from around May 9th 1983, and is comprised of just 7 source files, including the original MS-DOS Command-Line shell - COMMAND.ASM!
  4. MS-DOS 2.0 dates from around August 3rd 1983, and grew considerably in sophistication (and team size), and is comprised of 100 .ASM files
  5. There are some interesting documentation (.TXT, .DOC) files interspersed with the source and object files - many are well worth a read, as are many of the source code comments!

"Enjoy exploring the initial foundations of a family of operating systems that helped fuel the explosion of computer technology that we all rely upon for so much of our modern lives!" Turner wrote. MS-DOS is definitely considered among the most important software ever written and the company's latest effort will help many in their learning process. If you are interested in learning about the history of how MS-DOS came to be, you can have a look at an earlier piece published by Microsoft a few years back. GitHub repo is available here.

- Earlier: Microsoft Wants You to Relive the '90s with Its Windows 3.0 File Manager (Runs on Windows 10!)

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