Microsoft has for the first time made public the source code for two key software products from the company's distant past: the MS DOS operating system and Word for Windows.

The software giant announced that it was releasing the source code for the products via the Computer History Museum in Mountain View, California, saying that the important pieces of source code will thus be preserved and made available to the community for historical and technical scholarship.

The software comprises MS DOS versions 1.1 and 2.0, as well as Word for Windows 1.1a, one of the earliest word processors for the Windows platform.

MS DOS was Microsoft's version of the PC DOS platform it provided to IBM for the early PC systems, and was intended to boot from a floppy disk. MS-DOS version 1.1 dates from 1982, while version 2.0 is from 1983.

Word for Windows came several years later when Microsoft had introduced the Windows platform, initially running as a graphical user interface (GUI) that sat on top of DOS. Microsoft took full advantage of the Windows environment to deliver a product that was a step forward in user friendliness for its time, and also put it ahead of rivals that had dominated the DOS application market, such as Corel WordPerfect.

Roy Levin, distinguished engineer and managing director for Microsoft Research, said: "MS-DOS and Word for Windows built the foundation for Microsoft's success in the technology industry. By contributing these source codes to the Computer History Museum archives, Microsoft is making these historic systems from the early era of personal computing available to the community for historical and technical scholarship."