One of the founders of Microsoft, Paul Allen, died Monday of cancer at age 65.
Allen and childhood friend Bill Gates started the company in 1975 to sell software.
The company rose to dominate personal computer operating systems first with MS-DOS and then with Windows.
Allen had been fighting non-Hodgkin's lymphoma. He left Microsoft in 1982 due to illness.
In his life away from Microsoft, Allen became a philanthropist and sports owner, with the Portland Trail Blazers of the NBA and Seattle Seahawks of the NFL.
Allen and Gates founded "Micro-soft" 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.
Microsoft’s big break came in 1980, when IBM decided to move into personal computers and asked Microsoft to provide the operating system.
Microsoft didn't invent the system, but paid $50,000 for an existing one that was then tweaked to become MS-DOS.
It became the core of IBM PCs and their clones, skyrocketing Microsoft into the dominant position in computers.
In 1983, Microsoft Word and the Windows operating system were released. By 1991, Microsoft’s operating systems were used by 93 percent 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.
Allen was estimated to be worth $20.3 billion upon his death.