Gates talks about the two tech leaders' divisions - and their bonds.
Bill Gates has frugal tastes. Asked to name his luxuries, he lists DVDs, books and takeaway burgers. It is hard, however, to think that any fast-food outlet would get rich on Gates's custom. During a long list of engagements beginning well before dawn, he consumes nothing but cans of diet cola.
For America's wealthiest citizen, austerity is relative. The retinue of staff and the private jet hint at a fortune said to be approaching £40 billion (A$59 billion). As he told pupils at a south London school he visited last week:
"If I hadn't given my money away, I'd have had more than anyone else on the planet. Ninety-nine per cent of it will go."
Bill Gates moves seamlessly between worlds. His day in London started in the VIP suite of a television studio and shifted to a school assembly hall before he left for Davos, where he announced a new US$750 million (A$706 million) package to fight Aids, malaria and TB. Accustomed to morphing from the subsistence farms of Africa – the focus of his latest effort – to the salons of prime ministers, he does not see himself as a global power broker.
"I hope they're having a good time up at the top table, but I doubt they're discussing diarrhoea and malaria."
Video: Why I'm a charity worker now
Though always courteous, he has the inscrutable quality of the outsider. As a teenage geek in Seattle, he was entrusted with compiling class timetables on the ponderous school computer. At Harvard, he was the drop-out who founded a multi-billion dollar corporation, and at Microsoft, he was the pioneer in an uncharted techno-world.
One of the few people to understand his compulsions was Steve Jobs, the founder of Apple, who died of cancer in October. The two men's long and stormy relationship has been chronicled in Jobs's latest biography, but, until now, Gates has said little about their divisions - and their bonds.
"Steve was an incredible genius who contributed immensely to the field I was in. We had periods, like the early Macintosh, when we had more people working on it than they did. And then we were competitors. The personal computers I worked on had a vastly higher [market] share than Apple until really the last five or six years, where Steve's very good work on the Mac and on iPhones and iPads did extremely well. It's quite an achievement, and we enjoyed each [other's work]."
This tribute, part praise, part reminder of Gates's dominance, is more tactful than the comments Jobs made in his lifetime. "He spent a lot of his time competing with me. There are lots of times when Steve said [critical] things about me. If you took the more harsh examples, you could get quite a litany." In Jobs's view, his rival was "unimaginative", "a bit narrow" and derivative. As he once told an interviewer, "He [Gates] would be a broader guy if he had dropped acid once or gone off to an ashram."
The atmosphere changed in 2007 when Gates left Microsoft to set up the Bill and Melinda Gates Foundation with his wife. "Steve and I did an event together, and he couldn't have been nicer...I got a fair bit of time with him in his last year. Some months before Jobs died, Gates paid him a long visit. "We spent literally hours reminiscing and talking about the future." Later, with his old adversary's death imminent, he wrote to him. "I told Steve about how he should feel great about what he had done and the company he had built. I wrote about his kids, whom I had got to know."
That last gesture was not, he says, conciliatory. "There was no peace to make. We were not at war. We made great products, and competition was always a positive thing. There was no [cause for] forgiveness." After Jobs's death, Gates received a phone call from his wife, Laurene. "She said; 'Look, this biography really doesn't paint a picture of the mutual respect you had.' And she said he'd appreciated my letter and kept it by his bed."
Bill Gates rarely talks in such human terms. As a mathematician, he prefers numbers to emotion, focusing on the billion people in desperate poverty and the money needed to help them survive and work towards prosperity. As someone on the front line of mortality, he has balanced his aims against his own lifespan and wealth. Asked about his goal by a pupil at the school he is visiting, he says: "I'm 56. Hopefully I'll live another 25 to 30 years to see [unnecessary] deaths drop to zero."
"It's not about legacy," he tells me. "I'd like to see it get done. That is my job." He has no expectation that his three children, who will inherit only a tiny fraction of his money, will follow him.
"Our foundation won't last long beyond Melinda's and my lifetime. The resources will last about 20 years after whichever is the last of us to go. There is no family business, and my kids will make their own careers."
While he speculates that they will be "great doctors or great lawyers", he admires not only entrepreneurs but the market system.
"Capitalism has worked phenomenally. Look at North Korea versus South Korea, or China before and after 1979. Capitalism has shortfalls. It doesn't necessarily take care of the poor, and it underfunds innovation, so we have to offset that. We don't have to [ask] whether capitalism is wrong."
Though not especially religious, and far from pious ("People on the front line are the saints"), Bill Gates is driven on by faith.
"I believed in the personal computer and I devoted my life to it," he says. "If you have a dream, and it comes true, it's a very cool thing."
Now he extends the passion he once expended on enterprise to ending disease and starvation. The man who changed the way the rich world lives is equally determined to change the way in which the poor world dies.
In an era when the wealthiest are society's pariahs, the Microsoft founder has become the people's plutocrat. Although some diseases, such as malaria, remain rife, his charitable foundation and his lobbying have borne results. In the past year, not a single citizen in India contracted polio.
"People think aid is abstract and thousands of miles away. I go there and see it. I'm intent on making sure that my money gets to people who need it, and I come back and say it's working."
"Philanthropy should be voluntary." No one, he says, is going to take up giving "because someone scolded them or they heard Bill Gates say something mean. But I do think people are missing an opportunity to make an impact, learn a lot and be fulfilled."
Having persuaded almost 70 like-minded Americans, Warren Buffett included, to give up a large slice of their wealth, Gates would be happy to advise any Britons thinking of following suit. "We're looking for philanthropists to co-invest, so any advice we can give them [is on offer]."
Whether Britain's bonus beneficiaries will avail themselves of this service is questionable. Still, as Gates points out, there is always tax.
"With deficits the way they are, the rich are going to have to pay more. Unfortunately, almost everyone's going to have to pay more, and it should fall more heavily on the rich... Just raising taxes on the rich won't solve the crisis, but it seems reasonable to people – and there's plenty of room to do that without creating disincentives or distortions."
The news that the mega-rich US Republican candidate, Mitt Romney, pays 15 per cent tax "wasn't shocking at all. That's the US system. If people want capital gains taxed more like the highest rate on income, that's a good discussion. Maybe that's the way to help close the deficit."
Read Bill Gates's annual letter at .
The Telegraph, London