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Dark_Code_x

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Microsoft and IBM gave enthusiasts a trip to the past.

Ten years ago, Microsoft released the source code of the MS-DOS 1.25 and 2.0 operating systems for the Computer History Museum, and later "republished" them and posted them on GitHub for educational purposes. The system was written entirely in 8086 assembly code almost 45 years ago, and now occupies an important place in computer history.

Yesterday, April 25, Microsoft announced the publication of the source code of MS-DOS version 4.0. The code disclosure was made possible thanks to cooperation with IBM and is carried out under the MIT license. This step is part of an initiative to support open innovation.

Version 4.0 is of particular interest to enthusiasts, as this release was developed in collaboration with IBM.

Historical MS-DOS 4.0 materials, including source code, binaries, and documentation, are now also available on GitHub. This discovery was made possible by the efforts of researcher Connor Heide, who, in the course of correspondence with former Microsoft CTO Ray Ozzy, discovered unpublished beta versions of DOS 4.0.

Scott Hanselman and Internet archivist Geoff Sponaugle recovered data from the original floppy disks Ozzy had given them. These materials, known as "Ozzie Drops," include rare software versions and source code "ibmbio.com".

The OSPO team, led by Jeff Wilcox, actively searched the Microsoft archives for the full version of the MT-DOS code, but instead found the source code of MS-DOS 4.0.In addition to the code, beta versions, PDF documentation, and floppy disk images were published.

The software was successfully run on the original IBM PC XT, the newer Pentium, and the open-source PCem and 86box emulators, which confirms its functionality.
Microsoft and IBM will continue to research the archives for additional materials that can be added to the current release. Both companies express their gratitude to all participants of the project, including the creators of the software for digital archeology and the authors of the original code.
 
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