(AP) -- Bill Gates' successor as Microsoft's Chief Software Architect, Ray Ozzie, is leaving the company after five years.
In an e-mail sent to Microsoft Corp. employees Monday, CEO Steve Ballmer announced the change, saying Ozzie will stay with Microsoft for an undefined transition period.
Ballmer said the company is not looking for a replacement.
He said Ozzie - whose title translated into the company's top technical thinker - plans to concentrate on "the broader area of entertainment where Microsoft has many ongoing investments" before he leaves.
Ozzie came up with the idea for and helped build out Windows Azure, Microsoft's system for building and using software over the Internet.
He joined the company in 2005 as its chief technical officer when Microsoft bought his collaboration software company, Groove Networks. Already respected for his work with Web computing, Ozzie was asked to figure out how Microsoft could survive the sea change toward software being delivered online.
In the 1980s, Ozzie was at Lotus Development Corp., where he led work on Lotus Symphony, a precursor to Microsoft's Office package, and Lotus Notes, which let people form groups to share documents and e-mail. Notes' success prompted IBM to buy Lotus for $3.5 billion in 1995.
Ozzie then started Groove to refine his idea of "groupware" that lets multiple people collaborate. Groove made it possible for people to work together on the same virtual sketchpad, view the same video or edit documents simultaneously, all while chatting by text or voice.
This expertise made Ozzie a natural replacement for Gates as the mastermind of Microsoft's broad software strategy. Shortly after joining the company, Ozzie wrote an influential memo advocating a shift away from some of Microsoft's traditional reliance on selling desktop software and toward Web-based and sometimes ad-supported software. He urged Microsoft's product groups to make software that can run on a computer desktop, in a Web browser, on mobile devices and in game consoles, and to give users "seamless" access to their files no matter where they log on.
In Monday's e-mail, Ballmer referred back to that memo, reiterating a previous remark he had made that it "stimulated thinking across the company" and was a catalyst for getting Microsoft to concentrate on so-called "cloud" computing.
Explore further: Alibaba steals Yahoo's thunder ahead of IPO