Microsoft was founded on April 4, 1975, by Bill Gates and Paul Allen.
The company began after Gates and Allen developed and marketed a version of the BASIC programming language for the Altair 8800, an early personal computer. They initially used the name “Micro-Soft,” combining “microcomputer” and “software.” The hyphen was later dropped.
Microsoft’s major growth came through operating-system software, especially MS-DOS and Windows. Its business expanded into productivity software, servers, cloud computing, gaming, and professional networking. Those businesses helped make Microsoft one of the world’s largest companies by market capitalization.
The founding date is often confused with later milestones, including Microsoft’s incorporation in 1981 and the release of Windows in 1985. The company’s origin, however, is dated to the 1975 partnership formed around Altair BASIC.