Paul Gardner Allen was an American business magnate, computer programmer, researcher, investor, and philanthropist. He co-founded Microsoft Corporation with childhood friend Bill Gates in 1975, which helped spark the microcomputer revolution of the 1970s and 1980s. Microsoft became the world's largest personal computer software company. Allen was ranked as the 44th-wealthiest person in the world by Forbes in 2018, with an estimated net worth of $20.3 billion at the time of his death.