While a lot of you may not know who Bill Gates is, most of you have probably heard about Microsoft - the world's biggest software company he founded in 1975, at the tender age of twenty. Yesterday, this amazing man, who until last year, was also the world's richest, called it quits.

Gates and his friend Paul Allen (a co-founder of Microsoft) wrote their first computer program at the age of 13. Their fascination with computers continued when they went to Harvard University in 1973, and both of them dropped out in 1975 and founded Microsoft - the picture above shows the first eleven employees of the company (Bill is on the bottom far left, while Paul is on the bottom far right). Today, the company employs over half a million people worldwide.

Microsoft's first real opportunity came in 1980, when International Business Machines (IBM) chose it to create the operating system (the software that runs the computer) for its first personal computer. In fact, the system called MS-DOS, was not even developed at Microsoft, but bought by Bill and Paul for just $50,000 USD.

As personal computers became popular and as common in households as televisions were, Microsoft thrived. It continued to introduce new programs including "Word" and "Excel" and the Windows Operating System replaced MS-DOS on virtually every personal computer.

In 1983 Paul Allen, Bill's friend and partner was diagnosed with Hodgkin's Lymphoma, a kind of cancer that could be deadly. Paul decided to leave the company to get treated. While he never returned, thanks to his part ownership of Microsoft, he still ranks amongst the world's richest men.

Microsoft continued to thrive under the leadership of Bill Gates and in 1986, the company sold shares to the general public. The stock did really well making 31-year-old Bill, the youngest, self-made billionaire. In 1995 with $12.9 billion dollars to his name, Bill Gates became the richest man in the world - a title he retained until last year.

Gates, however is not just a brilliant businessman, he is also a big philanthropist. He has transferred a big chunk of his fortune to the Bill and Melinda Gates Foundation, which focuses on Global Health, Global Development and Education in the USA. Today, thanks to donations by other weathy individuals, this is the largest charitable foundation in the world, with assets exceeding $39.4 billion USD.

Though Bill remains the largest shareholder and chairman of Microsoft, he now plans to focus his daily energies on his foundation so that he continue making a difference in the world - only in a different way. However as you will see in the video below, while he may be one of the smartest and richest men on earth today, even Bill isn't good at everything he does!