Co-founder of Microsoft
Allen co-founded Microsoft (initially "Micro-Soft") with Bill Gates in Albuquerque, New Mexico, in 1975, and began marketing a BASIC programming language interpreter. In 1980, after promising to deliver IBM a Disk Operating System (DOS) they had not yet developed for the Intel 8088-based IBM PC, Allen spearheaded a deal for Microsoft to purchase a Quick and Dirty Operating System (QDOS) written by Tim Paterson who, at the time, was employed at Seattle Computer Products. As a result of this transaction, Microsoft was able to secure a contract to supply the DOS that would eventually run on IBM's PC line.
Courtesy of Wikipedia