Microsoft has decided to make MS-DOS 4.0 open source, publishing the repo on GitHub as it did in 2018 for versions 1.25 and 2.0 of the operating system. These three versions can also be used to create forks.
When IBM presented its first IBM 5150 personal computer with an Intel 8088 processor on August 12, 1981, it combined it with three different operating systems: CP/M-86, UCSD p-System and PC DOS. PC DOS had been commissioned in 1980 from a Seattle company founded only five years earlier, Microsoft.
Version 1.0 of PC DOS was floppy disk only and accompanied the launch of the IBM 5150. Microsoft then rewrote the software to support subdirectories and hard drives. Version 2.0 was released with the IBM PC-XT in March 1983.
However, Microsoft retained the rights to its operating system and licensed it to other computer manufacturers under the name MS-DOS (Microsoft Disk Operating System). He evolved it up to version 8 on September 14, 2000 in Windows Me.
MS-DOS 4.0 was released in October 1988, but the version published by Microsoft on GitHub, in collaboration with IBM and under license from MIT, has “something more”.
In putting together the MS-DOS 4.0 source files for release, there also appeared some beta binaries collected by a former Microsoft CTO named Ray Ozzie, who had also a rare paper version release documentation.
Microsoft then posted MS-DOS 4.0 on GitHub along with the additional binaries and exported PDF documentation (located in the “v4.0-ozzie” folder).
MS-DOS 4.0 source files, and even earlier versions 1.25 and 2.0 released in 2018, cannot be modified with pull requests on GitHub, but they can be used for experiments and forks.
