TWO months ago, Bill Gates met with members of the New York Times editorial board and a few editors and reporters. Public health was on his mind, and he spoke eloquently about the progress being made to combat diseases like tuberculosis and malaria, and the work of the Bill and Melinda Gates Foundation.

About an hour into the conversation, someone asked about Microsoft. The company seemed to be treading water, the mantle of high-tech leadership had passed to Apple and Google, and investors were impatient with Microsoft’s stagnant stock price. The question: Would Mr. Gates, the Microsoft chairman, consider going back to run the company?

That question comes to mind again, after Microsoft announced on Friday that Steven A. Ballmer, the chief executive, would step down within a year.