Microsoft Corporation is an American multinational technology company headquartered in Redmond, Washington. The company became influential in the rise of personal computers through software like Windows and has since expanded into areas such as Internet services, cloud computing, artificial intelligence, video gaming, and more. A Big Tech company, Microsoft is the largest software company by revenue, one of the most valuable public companies, and one of the most valuable brands globally. Founded in 1975 by Bill Gates and Paul Allen to market BASIC interpreters for the Altair 8800, Microsoft rose to dominate the PC operating system market with MS-DOS in the mid-1980s, followed by Windows. The company's 1986 initial public offering and the subsequent rise in its share price created three billionaires and an estimated 12,000 millionaires among Microsoft employees. Since the 1990s, it has increasingly diversified its business. Steve Ballmer replaced Gates as CEO in 2000.