The man who has stepped aside after 14 years as head of the world’s biggest software company has always exuded an overabundance of energy, running the gamut from ebullience (jumping sweatily around a stage to inspire an audience) to temper tantrum (throwing a chair across the room when a lieutenant quits).

The thoughtful, Indian-born engineer who has filled his shoes is from a different mould. “In personal style, he’s the opposite,” says Reed Hastings, the chief executive of Netflix and a former Microsoft director. “Steve is boisterous.

Satya is steady.” Steady hardly does it justice. Intellectually intense, he has a piercing gaze softened by a faint, slightly quizzical smile. If Mr Ballmer was the effervescent marketing dynamo, Mr Nadella is the quintessential engineer.

“He’s a cerebral guy, he’s not a pound-the-table kind of guy,” says John Connors, a former senior Microsoft executive. But along with the cool, he adds, Mr Nadella is “one of these rare guys” who is also business savvy with “a strong emotional IQ”.

Whether that will be enough to put Microsoft back on top in the technology world is another question. While milking its giant Windows and Office businesses for cash, Mr Ballmer has left it to his successor to drag the company out of its PC past.

Running Microsoft has also become “insanely complicated” because of its wide range of products, says Mr Connors. Top that off with a company-wide reorganisation that is halfway to completion, and the task looks daunting. Within weeks, Mr Nadella will also inherit one of the thorniest parts of the Ballmer legacy: the acquisition of the struggling Nokia handset business and its 35,000 nervous employees.

At 46, the new Microsoft chief is one of the first Indian-born executives to make it to the top of the US tech industry – though engineers from the subcontinent have long supplied much of the brain power, figuring prominently in recent years among the founders of West Coast start-ups.

Born in Hyderabad, a centre of the Indian IT industry, Mr Nadella took a degree in electrical engineering at Mangalore University before moving to the US, where he went on to complete a masters in computer science and an MBA.

In a carefully airbrushed official biography and an introductory email to staff[THIS WEEK?], he made much of his cricket obsession (he was once a right-handed off-spin bowler) and devotion to family. He wrote about his marriage to Anupama Priyadarshini – at 22 years, as long as his attachment to Microsoft – and three children, as well as what he called a “thirst for learning”.

When you have just got to the top, just about everyone has a good reason to talk well of you. But Mr Nadella, in particular, is “universally liked and respected” inside the company, says Matt McIlwain, a Seattle-based venture capitalist. Indeed, some are worried that he is too nice for the tough decisions ahead. Wall Street has pushed for cost-cutting and the spin-off of businesses such as the Xbox video games console. For much of the five months it took to find a new chief executive, many investors called for an outsider who would not be prevented by personal loyalties from making hard choices.

Popularity could be a sign that he ducked tough decisions on the way up, Mr McIlwain says – particularly at Microsoft, where clashing personalities have led to tensions at the top. Mr Nadella’s ability to rise without apparently making enemies along the way has left him in the right place at the right time.

People who have worked with him say this is not because he takes the soft option to avoid conflict. “He will demand a lot but do it in a very consensual way,” says Mr Connors. As Mr McIlwain concedes there is no way of telling whether this quality will survive the responsibilities and isolation that are about to hit him.

A deeply technical engineer with an eye for what is going on in corporate data centres, Mr Nadella is closely associated with the hottest trend reshaping the software world: the cloud. “If you love the cloud, you’ll love Satya Nadella,” says Mr Hastings, who points out that his first job was at Sun Microsystems, an early champion of the idea.

He is also credited with attacking technology orthodoxies at Microsoft. Those have included bringing Linux – the open-source software once seen as a mortal threat to the business – to Azure, its cloud platform. And, in a sign that the new boss wants to go further in ending insularity, people who have worked with him say he has an insatiable interest in the start-ups and new ideas bubbling up elsewhere in the tech industry.

He does not, however, have direct experience in the field most critical to Microsoft’s future: hitting back at Apple and Google in mobile computing.

One immediate test will be whether he can keep Bill Gates in his place. The Microsoft co-founder this week gave up his position as chairman but will take on a more active role as a technical adviser. People who have worked with both men say they have been able to work closely on big technical initiatives – for instance, when Mr Nadella ran the Bing search engine. “He’s perfectly able to stand up to Bill,” says Mr Hastings.

If Mr Nadella can hang on to the likeability, meanwhile, it could be one of his main assets in rebuilding Microsoft’s battered self-confidence. There was widespread relief at the company at the news of his appointment this week.