By the late 1980's, the term "DOS" became synonymous with the disk operating system designed specifically for IBM compatible microcomputers. IBM PCs (including the XT, AT, PS family, and Value Point family) all use PC DOS. Microsoft also sells (or licenses) MS DOS for use by the many IBM clones and other DOS based machines.

Apple Computers, Inc. which had a good share of the personal computer market from 1977 to 1982, had its own operating system software.

IBM's PC DOS is nearly identical to Microsoft's MS DOS, but there are some differences.

By 1984, IBM's PC DOS, had grabbed 35 percent of the personal computer market. With the arrival of IBM compatible clones running MS DOS, the path was set for DOS to become the standard by sheer volume alone.

In 1995, Microsoft Corporation released Windows '95, which runs on IBM compatible personal computers and does not require either "MS DOS" or "PC DOS" as separate underlying programs in order to operate.

References:

There is considerable history and drama surrounding the development of DOS for the IBM Personal Computer. The following sources are recommended for more detailed coverage of this topic:

"Gates: How Microsoft's Mogul Reinvented an Industry and Made Himself the Richest Man in America," Stephen Manes and Paul Andrews, Doubleday, 1993, pages 149 to 181.

"The Making of Microsoft: How Bill Gates and His Team Created the World's Most Successful Software Company," Daniel Ichbiah with Susan L. Knepper, Prima Publishing 1993, pages 68 to 95.

"Fortune" Magazine, October 2, 1995. Bill Gates and Paul Allen interviewed. Cover photo and title: "How We Did It." Article by Brent Schlender.