MS-DOS, the humble little operating system that was instrumental in establishing Microsoft’s dominance over the PC industry, turns 30 today. On July 27, 1981, Microsoft bought the rights for QDOS (Quick and Dirty Operating System). QDOS went on to be rebranded as MS-DOS (Microsoft Disk Operating System), which then went on to dominate the market for nearly fifteen years.

Colored Beginning

MS-DOS helped Microsoft blossom into a software giant that became both feared and hated for its often aggressive and sometimes illegal tactics. However, even before Microsoft was a household name, and even before Microsoft was a monopoly, Microsoft was no stranger to sneaky and clever business strategies. In those days, CP/M (Control Program for Microcomputers) by Gary Kildall of Digital Research, Inc. was the dominant OS, and IBM initially wanted to use it on their forthcoming PCs. However, talks broke down due to Kildall’s refusal to sign a non-disclosure agreement (although more colorful versions of the story are often told in tech folklore).

The next company that IBM approached was Microsoft, which had little experience in developing operating systems. Microsoft decided to license QDOS written by Tim Paterson, a Seattle Computer Products employee. Sneakily enough, Microsoft initially hid its IBM deal from Seattle Computer and managed to acquire the rights for less than $100,000. QDOS, which is often alleged to be virtually identical to CP/M, would soon succeed in obliterating the latter. However, the smartest decision that Microsoft took was to convince IBM to allow it to hold on to the rights for marketing DOS. As a result, Microsoft would go on to earn hundreds of millions in revenues over the next several years.