Paul Allen met Bill Gates at school in Seattle; he was 14, Gates was 12. Allen’s father was a librarian, his mother a teacher. Fast-forward a decade, and Allen persuaded his childhood friend to drop out of Harvard and co-found a company. Set up in 1975, it would become one of the most successful technology giants ever: Microsoft. First called Micro-Soft (a name suggested by Allen), the two friends believed that the combination of microprocessors and software would give the whole world personal computers. They got it. It’s Microsoft that most of the world will remember Allen for. He died on Monday from non-Hodgkin’s lymphoma at the age of 65. If you’re into gadgets, you may have heard of Altair, a hobby-kit personal computer from the 1970s. Allen’s and Gates’ first product was a computer language - BASIC - to power the Altair 8800, which made it easier for “computer hobbyists” to code. Many more products followed. In 1980, Microsoft bought a Quick and Dirty Operating System (QDOS), created by a programmer by Tim Paterson at Seattle Computer Products. The deal led to Allen and Gates’s big break, when IBM asked Microsoft to create an operating system for IBM’s personal computers. Thus MS-DOS was born, the Microsoft Disk Operating System – the name Allen and Gates gave to Paterson’s OS. Suddenly Microsoft found itself at the heart of the fledgling personal computer industry. Allen was Microsoft's executive vice president of research and new product development until 1983. He left when he was 30, after cancer diagnosis and following a disagreement with Gates over corporate strategy. In his memoir Inside Out: Microsoft in Our Own Words, published in 2011, he wrote that getting the cancer shock so young and having to face his own mortality “really makes you feel like you should do some of the things that you haven't done yet”. He remained on the board of Microsoft until 2000. But there’s much more to Allen’s legacy than Microsoft. Reacting to the death of his friend, Gates said Allen wasn’t happy with creating just one company. “He channeled his intellect and compassion into a second act focused on improving people’s lives and strengthening communities in Seattle and around the world,” Gates wrote. “He was fond of saying, ‘If it has the potential to do good, then we should do it’”. For nearly 40 years, Allen invested in a number of large technology companies, although many of his bets (for example on cable television) were less than successful. He certainly did well with his $243 million investment in Ticketmaster, which gave him 80 per cent of the company, and was the driving force to move the company online. In the early 1990s, Allen also teamed up with Stanford computer science professor David Liddle (who had gained fame as one of the key developers of the Xerox Star computer system). Together they co-founded the Interval Research Corporation, a Silicon Valley lab and incubator that went on to file hundreds of patents. The company closed down in 2000 – but had a controversial legacy when some of its patents were being used in patent infringement claims against tech firms like Apple, Facebook, Google, Yahoo!, YouTube, Netflix and eBay (but not Microsoft). More importantly, Allen pursued many philanthropic projects. First came the Paul G. Allen Family Foundation, which was his key vehicle to invest in health and science research. The foundation contributes $30m annually to many scientific and humanitarian projects. In 1986, with his sister Jody Allen, he also founded investment firm Vulcan, to manage his investments and philanthropic contributions. Fifteen years ago, Allen boosted his health and science investments, establishing the non-profit called Allen Institute for Brain Science with a donation of $100m. Five years later, he invested $41m in the Allen Spinal Cord Atlas online mouse gene map, which helps scientists access all existing spinal cord research data and research new diagnoses for various neurological disorders. By one estimate, Allen’s contributions to non-profit organisations in his native Pacific Northwest amounted to around $1 billion, although his total donations to advance scientific research, investigate the health of our oceans, fight homelessness, research nuclear-fusion power, among others, are said to exceed $2bn. Like many other Silicon Valley pioneers, Allen also caught the space bug and in 2011 founded Stratolaunch System – the first private space transport system to take a plane into orbit to launch satellites into space. In Oregon and Washington state, however, all these contributions may well be outshone by Allen’s love of sports and his (highly successful) investments in local sports teams. He bought NBA's Portland Trail Blazers, the NFL's Seattle Seahawks, and had a stake in the Seattle Sounders soccer team. Still, it’s his technology vision that really made a difference. In articles penned in the mid-1970s, Allen predicted not only the internet, but also the type of personal computing devices that today we would call smartphones. “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,” Microsoft CEO Satya Nadella wrote on Twitter. Little wonder that the computer science centre at the University of Washington in Seattle bears his name. Allen himself, however, may have been prouder of MoPOP, the Museum of Pop Culture, which he founded in 2000. Allen loved music, idolised Jimi Hendrix – and according to legendary music producer Quincy Jones – played the guitar nearly as good as his idol.