Paul Allen death: Microsoft co-founder and billionaire philanthropist dies aged 65 after cancer battle

The billionaire co-founder of Microsoft Paul Allen has died aged 65.

Bill Gates, a childhood friend of Mr Allen, was among those to pay tribute to him after news of his death emerged on Monday night.

His death was announced by his family and company Vulcan.

Earlier this month, Mr Allen revealed that the non-Hodgkin's lymphoma, a group of blood cancers, he was treated for in 2009 had returned and he planned to fight it aggressively.

In statement on Monday, his sister Jody Allen said: “While most knew Paul Allen as a technologist and philanthropist, for us he was a much-loved brother and uncle, and an exceptional friend”.

Paying tribute to his friend, Mr Gates said: “I am heartbroken by the passing of one of my oldest and dearest friends, Paul Allen.”

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 start-up, 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.

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 per cent 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.

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".

Mr Allen, who was an avid sports fan, also owned the NBA’s Portland Trail Blazers and NFL’s Seattle Seahawks.

Agencies contributed to this report.