The founder and head of Microsoft, the world's largest software company Bill Gates steps down on Friday. One of the richest men in the world, Gates will now work full time for his charitable organization The Bill & Melinda Gates Foundation. The 52-year-old will continue to be chairman though, but will only retain a nominal role in the software empire. He is still is the biggest shareholder of the company and his 8.7 per cent stake in Microsoft is worth about 23 billion dollars. Gates authored the personal computer revolution three decades ago when he founded Microsoft along with his friend Paul Allen. Microsoft released a commemorative video paying tribute to Bill's service to the company, titled "Bill Gates: Looking back, Moving Ahead". It can be watched on the company's website here.