William Henry "Bill" Gates III (born October 28, 1955) is an American business magnate, investor, author, philanthropist, and humanitarian. He is best known as the principal founder of Microsoft Corporation. During his career at Microsoft, Gates held the positions of chairman, CEO and chief software architect, while also being the largest individual shareholder until May 2014. In 1975, Gates and Paul Allen launched Microsoft, which became the world's largest PC software company. Gates led the company as chairman and CEO until stepping down as CEO in January 2000, but he remained chairman and became chief software architect.