Which company did Microsoft acquire the rights to for the operating system that became MS-DOS?

Microsoft acquired the rights to the operating system from Seattle Computer Products, whose system became the foundation of MS-DOS.

In 1980, IBM asked Microsoft to provide an operating system for its new personal computer. Microsoft did not initially own a suitable disk operating system, so it licensed 86-DOS from Seattle Computer Products. Microsoft later purchased the rights and adapted the software for IBM’s PC.

The system was first known as QDOS, short for “Quick and Dirty Operating System,” and was renamed 86-DOS before Microsoft’s involvement. IBM received a version called PC DOS, while Microsoft marketed its own version as MS-DOS.

A common mix-up is crediting Microsoft with writing the original system entirely from scratch. Microsoft developed and expanded the software, but its immediate starting point was Seattle Computer Products’ 86-DOS.