Microsoft and IBM make MS-DOS 4.00 Open-Source

Microsoft, in collaboration with IBM, has recently made MS-DOS 4.00 open-source. The Microsoft Disk Operating System (MS-DOS), launched in 1981, has been around for 43 years, with the 4.00 version released in 1986.

MS-DOS 4.00 was initially designed with preemptive multi-tasking capabilities, a sophisticated feature for its time, which enabled certain programs to run in the background. However, this version, dubbed "Multitasking DOS," was not widely used due to a lack of interest from Original Equipment Manufacturers (OEMs), including IBM, which restricted its availability. Because of this, the final MS-DOS 4.00 version, launched in 1988, did not fully incorporate its planned multi-tasking capabilities. Nevertheless, Microsoft has shown the operability of MS-DOS 4.00 on an IBM PC XT using emulation software like PCem and 86Box, demonstrating its compatibility with modern systems.

The source code for MS-DOS 4.00 is now accessible on GitHub, giving developers and enthusiasts the chance to explore and work with this significant piece of computing history.