SAN FRANCISCO, June 27: Bill Gates spent his last day at Microsoft on Friday before turning his attention full time to philanthropy after decades spent building the software colossus.

The Microsoft co-founder, 52, known for his boyish face and nerdy manner, spent his final day at the software giant he helped found 33 years ago.

After decades devoted to Microsoft, Bill Gates plans to turn his attention full time to the philanthropic Bill and Melinda Gates Foundation he established with his wife.

Gates leaves Microsoft to wrestle with a fast-changing computer era and growing challenges from Internet juggernaut Google and long-time rival Apple, which makes Macintosh computers.

Three people will essentially fill the void Gates leaves behind at Microsoft. Gates’s job as chief software architect is being handled by Ray Ozzie.

Craig Mundie inherited Gates’s chief research and strategy officer duties, while former Harvard University classmate Steve Ballmer is chief executive officer of the Redmond, Washington-based software firm. Gates remains chairman of the Microsoft board of directors and its largest shareholder.

Microsoft is losing Gates at a time when “cloud computing” is shaking the packaged software foundation on which the company’s fortune is built.

Cloud computing refers to a trend in which firms such as Google and Salesforce.com let people use programs on the Internet instead of having to install and maintain software on their own computers.

Microsoft competes in the “software as a service” arena, but tends to combine offerings with packaged products in a “software-plus” marketing model, according to analysts.

Meanwhile, Microsoft’s Windows Vista operating system released in January of 2007 has flopped with customers, many of whom are clinging to its predecessor Windows XP. Vista loathing is heightening interest in free Linux open-source software and Macintosh computers, which use operating systems built by Apple.

Rivalry between Microsoft and Apple is legendary in Silicon Valley. Apple ads and press conferences take swipes at Microsoft, and devotees of competing systems routinely swap barbs in cafes and other social venues. The culture-shifting popularity of Apple’s iPods and iPhones is credited with increasing interest in Macintosh machines.

While Windows is still used on 90 percent of the world’s computers, Macintosh computers have grown to more than five percent of the market.—AFP