Paul G. Allen, the co-founder of Microsoft who helped usher in the personal computing revolution and then channeled his enormous fortune into transforming Seattle into a cultural destination, died on Monday in Seattle. He was 65.
The cause was complications of non-Hodgkin’s lymphoma, his family said in a statement.
The disease recurred recently after having been in remission for years. He left Microsoft in the early 1980s, after the cancer first appeared, and, using his enormous wealth, went on to make a powerful impact on Seattle life through his philanthropy and his ownership of N.F.L. and N.B.A. teams there, ensuring that they would remain in the city.
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Mr. Allen was a force at Microsoft during its first seven years, along with his co-founder, Bill Gates, as the personal computer was moving from a hobbyist curiosity to a mainstream technology, used by both businesses and consumers.
When the company was founded, in 1975, the machines were known as microcomputers, to distinguish the desktop computers with the hulking machines of the day. Mr. Allen came up with the name Micro-Soft, an apt one for a company that made software for small computers. The term personal computer would become commonplace later.
The company’s first product was a much-compressed version of the Basic programming language, designed to suit those underpowered machines. Yet the company’s big move came when it promised the computer giant IBM that it would deliver the operating system software for IBM’s entry into the personal computer business. Mr. Gates and Mr. Allen committed to supplying that software in 1980.
At the time, it was a promise without a product. But Allen was instrumental in putting together a deal to buy an early operating system from a programmer in Seattle. He and Mr. Gates tweaked and massaged the code, and it became the operating system that guided the IBM personal computer, introduced in 1981.
Mr. Allen scored a perfect 1,600 on his SAT test, and went on to Washington State University. But after two years he dropped out to work as a programmer for Honeywell in Boston. Mr. Gates was nearby, attending Harvard University.
When an early microcomputer was introduced, appearing on the cover of Popular Electronics magazine, Mr. Allen persuaded Mr. Gates to drop out of Harvard and move to Albuquerque, where a start-up called MITS had built a machine that has been credited as the first personal computer. The machine lacked software, and Mr. Allen and Mr. Gates, showing up at the MITS offices, promised that they could supply it.
During his tenure the Seahawks made their only three Super Bowl appearances, winning the title once, in 2014.
“I personally valued Paul’s advice on subjects ranging from collective bargaining to bringing technology to our game,” Roger Goodell, the N.F.L. Commissioner, said in a statement.
One of Allen’s companies also owned a stake in the Seattle Sounders, one of the most successful franchises in Major League Soccer. The Sounders won the league title in 2016.
It is unclear what will happen to Mr. Allen’s teams; the details of his estate are not public. The Seahawks alone are worth an estimated $2.58 billion. Few N.F.L. and N.B.A. clubs change hands, so any sale is likely to attract substantial bids.
Paul Gardener Allen was born in Seattle on Jan. 21, 1953, to Kenneth and Edna (Faye) Allen. His father was a librarian; his mother a schoolteacher. He is survived by his sister, Jody Allen.
Three years ago, when commemorating Microsoft’s 40th anniversary, Mr. Allen posted on Twitter a bit of the code for the company’s first software product. At the top, it said, “Copyright 1975 by Bill Gates and Paul Allen.”
“It’s weird to look at bits of code you wrote 40 years ago and think, ‘That led to where Microsoft is today,’ ” Mr. Allen said at the time. He sounded genuinely amazed.