[WindowsCentral.com]

Exactly 36 years ago today, Microsoft Cofounder Bill Gates made one of the important purchases in the software giant's storied history.
On July 27, 1981, Gates fully licensed the "quick and dirty operating system" (QDOS) from a company called Seattle Computer Systems, according to The Register. That OS would later become known as MS-DOS.

Full story from the WindowsCentral blog...