IBM PC DOS, an acronym for IBM Personal Computer Disk Operating System, is a discontinued disk operating system for the IBM Personal Computer, its successors, and IBM PC compatibles. It was manufactured and sold by IBM from the early 1980s into the 2000s. Developed by Microsoft, it was also sold by that company as MS-DOS. Both operating systems were identical or almost identical until 1993, when IBM began selling PC DOS 6.1 with new features. The collective shorthand for PC DOS and MS-DOS was DOS, which is also the generic term for disk operating system, and is shared with dozens of disk operating systems called DOS.

Seattle Computer Products (SCP) was a Tukwila, Washington, microcomputer hardware company which was one of the first manufacturers of computer systems based on the 16-bit Intel 8086 processor. Founded in 1978, SCP began shipping its first S-100 bus 8086 CPU boards to customers in November 1979, about 21 months before IBM introduced its Personal Computer which was based on the slower 8088 and introduced the 8-bit ISA bus. SCP shipped an operating system for that hardware about a year before the release of the PC, which was modified by Microsoft for the PC and renamed IBM PC DOS. SCP was staffed partly by high-school students from nearby communities who soldered and assembled the computers. Some of them would later work for Microsoft.