(born 1955), U.S. entrepreneur, born in Seattle, Wash.; founder and chief executive officer of Microsoft Corporation, world's most prosperous computer software firm; started computer programming as a teenager; with friends, founded Traf-O-Data software company while in high school; briefly attended Harvard Univ.; with Paul Allen, founded Microsoft in 1975; hired by Tandy Corporation 1977 to design software; by 1980 Microsoft was leading software company; for IBM personal computers (PCs), produced MS-DOS (Microsoft Disk Operating System), which became worldwide standard for PCs; company moved into applications software and popular Windows graphical user interface; Gates was a billionaire by age 31, one of the world's wealthiest individuals.