William Henry "Bill" Gates III (born October 28, 1955) is an American business magnate and philanthropist. Gates is the former chief executive and current chairman of Microsoft, the world’s largest personal-computer software company, which he co-founded with Paul Allen. He is consistently ranked among the world's wealthiest people and was the wealthiest overall from 1995 to 2009, excluding 2008, when he was ranked third; in 2011 he was the wealthiest American and the second wealthiest person. During his career at Microsoft, Gates held the positions of CEO and chief software architect, and remains the largest individual shareholder, with 6.4 percent of the common stock. He has also authored and co-authored several books.