Now, Mr. Nadella is known as a cerebral, collaborative leader with a low-key style that differs from Mr. Ballmer’s bombastic manner. While many executives within Microsoft tend to be polarizing figures, Mr. Nadella appears to be well liked in much of the company. Still, those who know Satya Nadella say that he is not a pushover as a boss.

“Managers have to keep proving themselves every day,” Mr. Artale said.

Mr. Nadella’s star at Microsoft rose considerably in the past several years as he took charge of the company’s cloud computing efforts, a business considered vital as more business customers choose to rent applications and other programs in far-off data centers rather than run software themselves.

For years, Microsoft did not pay enough attention to how the cloud — primarily through services offered by Amazon, its crosstown rival — was attracting the creativity of a new generation of developers. When he got control of the division that included Microsoft’s cloud initiatives, Mr. Nadella changed that. He began meeting with start-ups to hear more about what Microsoft needed to do to become more responsive to their needs.

“When you look at the most exciting things happening in tech, all the platform shifts happening and disruption — social, mobile, cloud — Microsoft has not even been part of the conversation until recently,” said Brad Silverberg, a Seattle-area investor and a former Microsoft executive. “With Satya’s leadership, Microsoft is doing interesting things in cloud.”

As chief executive of the entire 100,000-person company, Mr. Nadella has to grapple with a much broader set of challenges in markets in which he has little experience, like mobile devices. He inherits a deal to acquire Nokia’s mobile handset business, along with 33,000 employees, and a wide-ranging reorganization plan devised by Mr. Ballmer and still in progress.

In an interview in July, Mr. Nadella was supportive of the reorganization plan, which he predicted would allow Microsoft to adapt to changes in the market more quickly than in the past. “It’s not like our old structure didn’t allow us to do some of this,” he said. “The question is whether you can amplify.”

When Mr. Nadella joined Microsoft in 1992, it was still a scrappy, relatively small software company led by Mr. Gates that was just beginning its greatest years of growth. His familiarity with the company’s history and culture was said to have been an important factor in Mr. Gates’s comfort with Mr. Nadella as chief executive, according to someone briefed on the search for a new leader who asked for anonymity because the process was private.