Gates began programming at school and in 1975, while an undergraduate at Harvard, wrote a BASIC interpreter with his friend Paul Allen for an early microcomputer, the MITS Altair. This Gates-Allen partnership was the genesis of Microsoft, and Gates left Harvard to develop the business. While he personally supervised Microsoft’s products in the early years, he became better known for the business acumen that has built Microsoft into the world’s largest software company, in the process making himself the world’s richest person. Notable successes include securing the contract (1980) to supply an operating system for the original IBM personal computer while retaining the right to market it separately (as MS-DOS); and the exploitation of the success of Windows 3.x after 1990 to achieve dominance of the PC marketplace. Gates was CEO of Microsoft until 2000, then chief software architect until 2006; he stepped down as chairman in 2014. He has used part of his personal fortune for philanthropic purposes, founding the Bill & Melinda Gates Foundation with his wife in 2000.