Paul Allen, who has died from complications of non-Hodgkin's lymphoma at the age of 65, was the co-founder with Bill Gates of Microsoft, on the strength of which he became one of the world's richest people.
His wealth, estimated at more than $20-billion (about R288-billion), allowed him to launch a private asset management firm, Vulcan Inc, which backed more than 50 businesses; to set up philanthropic ventures (his foundations gave away around $2-billion); to own several sports teams; and to collect gigantic yachts as well as science-fiction and rock 'n roll memorabilia.
He was born in Seattle on January 21 1953. Both his parents were university librarians and he grew up in a house stuffed with books.
He and Gates met in high school through a shared interest in early desktop technology, and set up a company, Traf-O-Data, that planned to build computers to analyse traffic volumes.
The two men, in succession, dropped out of college, meanwhile writing software for the affordable new Altair 8800 processor.
Micro-Soft (as it was originally called) was registered as a business in 1976. Gates handled contracts and business negotiations, and Allen concentrated on ideas for new technology and products.
In 1981 IBM asked if Allen and Gates would be interested in producing the operating system for its new "microcomputer". Allen acquired a CP/M (Control Program for Microcomputers) clone which ran on a "Quick and Dirty Operating System" (Q-DOS) called 86-DOS. He paid less than $50,000, in what has been called "the deal of the century". Allen and Gates's modification of 86-DOS became MS-DOS, the default operating system for the vast majority of PCs.
The company restructured, with Gates as president and chair of the board, and Allen as executive vice-president, of what was then Microsoft.
In 1983, with the release of Microsoft Mouse and Microsoft Word, which rapidly established itself as the most popular word-processing program, the company had already begun its spectacular rise.
That year, however, Allen was diagnosed with Hodgkin's disease, and underwent months of radiation therapy and a bone-marrow transplant. He decided to step away from Microsoft.
From 1990 he began to invest in a wide range of companies. By that point he was, thanks to his stock holding in Microsoft, the third richest American, with a fortune estimated at $30-billion. He poured it into developing Seattle and its sports teams, and charity.
By 2009 the cancer had returned.
Allen remained a private figure, though in 2011 he detailed the tensions in his creative partnership with Gates. When not travelling, often on one of his vast yachts, he lived in a compound near his mother, who died in 2012, and his sister.
He was linked at various times with glamorous actresses, and with the tennis player Monica Seles, but he never married.
1953-2018..