Tim Paterson

Who is Tim Paterson?

Tim Paterson is an American computer programmer, best known as the original author of MS-DOS, the most widely used personal computer operating system in the 1980s.

Paterson was educated in the Seattle Public Schools, graduating from Ingraham High School in 1974. He attended the University of Washington, working as a repair technician for The Retail Computer Store in the Green Lake area of Seattle, Washington, and graduated magna cum laude with a degree in Computer Science in June 1978. He went to work for Seattle Computer Products as a designer and engineer. He designed the hardware of Microsoft's Z-80 SoftCard which had a Z80 CPU and ran the CP/M operating system on an Apple II.

A month later, Intel released the 8086 CPU, and Paterson went to work designing an S-100 8086 board, which went to market in November 1979. The only commercial software that existed for the board was a standalone version of Microsoft BASIC. The standard CP/M operating system at the time was not available for this CPU and without a true operating system, sales were slow. Paterson began work on QDOS in April 1980 to fill that void, copying the APIs of CP/M from sources including the published CP/M manual so that it would be highly compatible. QDOS was soon renamed as 86-DOS. Version 0.10 was complete by July 1980. By version 1.14 86-DOS had grown to 4,000 lines of assembly code. In December 1980 Microsoft secured the rights to market 86-DOS to other hardware manufacturers.