What company developed the MS-DOS operating system?

The ubiquitous Disk Operating System, or DOS, that powered early personal computers owes its widespread adoption to Microsoft. While the initial version wasn't entirely built from scratch by Microsoft, the company played a pivotal role in its development and commercial success, ultimately making it the standard operating system for IBM PC compatibles.

The story begins when IBM was developing its first Personal Computer (PC) in the early 1980s and needed an operating system. IBM initially approached Digital Research, the creators of the popular CP/M operating system, but negotiations stalled. Turning to Microsoft, a company known then for its programming languages like BASIC, IBM contracted them to provide an operating system. Microsoft, in turn, acquired an operating system called 86-DOS (also known as QDOS, for Quick and Dirty Operating System) from Seattle Computer Products (SCP) for a reported $50,000 to $75,000.

Microsoft then adapted and refined 86-DOS, rebranding it as MS-DOS. This modified version was licensed to IBM to be sold as PC DOS 1.0 with their new personal computer in August 1981. Crucially, Microsoft retained the right to license MS-DOS to other computer manufacturers. This strategic move allowed MS-DOS to become the dominant operating system for the rapidly expanding market of IBM PC compatible "clone" computers, solidifying Microsoft's position as a major force in the software industry. MS-DOS continued to evolve through various versions, introducing features like support for hard disks and hierarchical file systems, before eventually being superseded by graphical user interfaces like Microsoft Windows.