Paul Allen, who co-founded Microsoft with his childhood friend Bill Gates before becoming a billionaire philanthropist, has died aged 65.
He died in Seattle from complications of non-Hodgkin’s lymphoma, his company Vulcan Inc announced.
Mr Gates said he was heartbroken about the loss of one of his “oldest and dearest friends”.
“Personal computing would not have existed without him,” Mr Gates said in a statement.
“But Paul wasn’t content with starting one company. He channelled his intellect and compassion into a second act focused on improving people’s lives and strengthening communities in Seattle and around the world. He was fond of saying, ‘If it has the potential to do good, then we should do it’,” Mr Gates wrote.
It is with deep sadness that we announce the death of @PaulGAllen, our founder and noted technologist, philanthropist, community builder, conservationist, musician and supporter of the arts. All of us who worked with Paul feel an inexpressible loss today. https://t.co/OMLZ7ivvSD pic.twitter.com/Bfa8kK6Q8e
— Vulcan Inc. (@VulcanInc) October 15, 2018
Microsoft chief executive Satya Nadella called Mr Allen’s contributions to the company, community and industry “indispensable”.
“As co-founder of Microsoft, in his own quiet and persistent way, he created magical products, experiences and institutions, and in doing so, he changed the world,” Mr Nadella wrote on Twitter.
Mr Allen, who was an avid sports fan, owned the Portland Trail Blazers and the Seattle Seahawks.
He and Mr Gates met while attending a private school in north Seattle.
The two friends would later drop out of university to pursue the future they envisioned: a world with a computer in every home.
Mr Gates so strongly believed it that he left Harvard University in his junior year to devote himself full-time to his and Mr Allen’s startup, originally called Micro-Soft.
Mr Allen spent two years at Washington State University before dropping out as well.
They founded the company in Albuquerque, New Mexico, and their first product was a computer language for the Altair hobby-kit personal computer, giving hobbyists a basic way to program and operate the machine.
After Mr Gates and Mr Allen found some success selling their programming language, MS-Basic, the Seattle natives moved their business in 1979 to Bellevue, Washington, not far from its eventual home in Redmond.
Microsoft’s big break came in 1980, when IBM decided to move into personal computers and asked Microsoft to provide the operating system.
Mr Gates and company did not invent the operating system.
Statement from Microsoft CEO Satya Nadella on the passing of Paul Allen: pic.twitter.com/1iLDLenLKz
— Microsoft (@Microsoft) October 15, 2018
To meet IBM’s needs, they spent 50,000 dollars to buy one known as QDOS from another programmer, Tim Paterson.
Eventually the product, refined by Microsoft – and renamed DOS, for Disk Operating System – became the core of IBM PCs and their clones, catapulting Microsoft into its dominant position in the PC industry.
The first versions of two classic Microsoft products, Microsoft Word and the Windows operating system, were released in 1983.
By 1991, Microsoft’s operating systems were used by 93% of the world’s personal computers.
The Windows operating system is now used on most of the world’s desktop computers, and Word is the cornerstone of the company’s prevalent Office products.
Microsoft was thrust on to the throne of technology and soon Mr Gates and Mr Allen became billionaires.
With his sister Jody Allen in 1986, he founded Vulcan, the investment firm that oversees his business and philanthropic efforts.
“My brother was a remarkable individual on every level,” his sister said in a statement. “Paul’s family and friends were blessed to experience his wit, warmth, his generosity and deep concern,” she added.
He founded the Allen Institute for Brain Science and aerospace firm Stratolaunch, which has built a colossal plane designed to launch satellites into orbit.
He has also backed research into nuclear-fusion power.
Mr Allen later joined the list of America’s wealthiest people who pledged to give away the bulk of their fortunes to charity.
In 2010, he publicly pledged to give away the majority of his fortune, saying he believed “those fortunate to achieve great wealth should put it to work for the good of humanity”.
When he released his 2011 memoir, Idea Man, he allowed 60 Minutes inside his home on Lake Washington, across the water from Seattle, revealing collections that ranged from the guitar Jimi Hendrix played at Woodstock to vintage war planes and a 300ft yacht with its own submarine.
Mr Allen served as Microsoft’s executive vice president of research and new product development until 1983, when he resigned after being diagnosed with Hodgkin’s lymphoma.
“To be 30 years old and have that kind of shock – to face your mortality – really makes you feel like you should do some of the things that you haven’t done yet,” Mr Allen said in a 2000 book, Inside Out: Microsoft In Our Own Words, published to celebrate 25 years of Microsoft.
His influence is firmly imprinted on the cultural landscape of Seattle and the Pacific Northwest, from the bright metallic Museum of Pop Culture designed by architect Frank Gehry to the computer science centre at the University of Washington that bears his name.
In 1988 at the age of 35, he bought the Portland Trail Blazers professional basketball team.
He told the Associated Press that “for a true fan of the game, this is a dream come true”.
Mr Allen was also a part owner of the Seattle Sounders FC, a Major League Soccer team, and bought the Seattle Seahawks.
He could sometimes be seen at games or chatting in the dressing room with players.