Trademark (Microsoft disk operating system) An operating system written by Microsoft to be marketed with the early release of the IBM Personal Computer. The prefix MS is used to help distinguish the product from the large number of similarly titled DOS products. When IBM first announced the IBM PC, the company intended that it would run under CP/M, a popular proprietary operating system then available on other hardware platforms. In the event, Microsoft offered IBM their own product, which was to some extent a modified version of CP/M and was to be known as MS-DOS. The rest is history.

In common with other versions of DOS, MS-DOS has limited functionality, offering a command-line interface, management of peripheral devices, management of files, and no multitasking. The initial hardware restriction of the IBM PC to a total of 640 Kbytes of memory is embedded in MS-DOS. An MS-DOS emulator continues to be available in Windows.