During the transition, Mr. Gates has also stayed closely involved in shaping Microsoft’s strategy in the search market where it has been assiduously attempting to catch Google and Yahoo.

“We made all the structural changes we were going to make, and we rode in tandem last year,” said Mr. Mundie. “In the last few months Bill has transitioned to what I start to think of as special project mode.”

If he is stepping away from Microsoft, Mr. Gates has shed none of his trademark combativeness. He rejected the Silicon Valley view that Microsoft has begun to exhibit the same sclerotic signs of middle age that I.B.M. did when it dominated the computer industry, but failed to respond effectively to the challenge of the personal computer.

I.B.M. is no longer at the center of the computer industry, he asserted, for two reasons. First, the industry is now centered on personal computing. “As much as I.B.M. created the I.B.M. PC, it was never their culture, their excellence,” he said. “Their skill sets were never about personal computing.”

Second, the center of gravity in the computer industry has dramatically shifted toward software, he said. “Why do you like your iPod, your iPhone, your Xbox 360, your Google Search?” he said. “The real magic sauce is not the parts that we buy for the Xbox, or the parts that Apple buys for iPhones, it’s the software that goes into it.”

During the interview Mr. Gates rejected the notion that Google could become a successful competitor in the smartphone software market, where Microsoft has about 10 percent market share. The Silicon valley search engine provider has been widely reported to be preparing to enter the cellphone market with its own software and a host of services springing from that software.

Microsoft’s chairman said it was unlikely that Google would be able to make inroads into the Microsoft’s share of market for mobile phone software.