Profile: He runs on a program for whiz-kids: William Gates, wealthiest man in the US

According to the Forbes index published this week, the richest man in the United States is William H Gates III (net personal worth, dollars 6.4bn - or pounds 3.4bn). He is a man who is known, according to another prominent player in the Gates world - which is that of computer software - as 'not big on hygiene'. Pause. 'You know,' the man says, 'he doesn't bathe properly.'

But a bright man. 'Very bright, but big on the nerd tactic, if you know what I mean.' Uh-uh. 'Well, his unvarying strategy is the verbal bludgeon. He meets someone in the business, 'What are you up to?' he asks. 'What's new?' And then when that someone tells him, he says, 'You're full of shit.'

'Then he stocks it away and starts chewing at the other guy's idea on his own.'

'A bit like the Standard Oil group,' another says. 'Like he has plans to dominate the earth . . . and then colonise Mars. The guy has limitless ambition and, above all, energy.'

In fact Bill Gates is to computers what Bobby Fischer was to chess and Glenn Gould to music, a sort of moist, basement weirdo and loner, someone who thinks his own way, does his own thing and parleys his very isolation into the kind of posture towards the world that others fear. He is a Grade One Obsessive. Becoming personally worth dollars 6.4bn three years before you're 40 is hardly something you're going to do in normal ways.

Gates has done it by figuring out a way to tax, just as a state does, an industry that is in super-explosion, so that as it enlarges its galaxy he collects on every particle. Gates's Microsoft, his MS-DOS system, an adaptation of a system he bought for dollars 50,000 and managed to convince IBM to install on its computers and all its clones, enables the present generation of computers to work efficiently and be accessed industry-wide. On this access, Gates levies. Profitably.

Software is indeed the profitable end of the computer business. All a software designer needs is a certain kind of mind - the ability to think intuitively and logically, to like problem-solving and to have a taste for improvisation - and room for creativity. Ditch all the overheads that contribute to a cost factor for hardware of something like 85 per cent of the final value, and that factor goes down to about 15 per cent. The result is a fair number of nerd-geniuses earning vast sums. Gates and his former partner, Paul Allen, who left Microsoft in 1983 and formed his own company in 1985, may be the only billionaires in the club, but reliable estimates show that in Gates's company, Microsoft Corporation, about 2,200 employees are millionaires.

Bill Gates's world is one of unending potential, which may be why Holden Caulfield (the protagonist of Salinger's The Catcher in the Rye) is his hero. As he has said, Caulfield is 'sort of about being able to see things in a way people don't understand. You have this model in your head of what's going on out there, and adults are sort of thinking that this guy's just a kid.'

Kid or not, the image that Gates cultivates is that of the slouchy adolescent that he was when he first got hooked on computers.

Bill Gates (always called 'Trey' by his family because he is Bill the Third) was the second-born in a settled, moneyed and socially respectable family. Bill inherited a dollars 1m trust fund from his maternal grandfather; his father is one of Seattle's most prominent lawyers, while his mother excels in good works and is on the state governing board of the University of Washington (to which Gates has recently donated dollars 11m).

He attended Lakewood School - a force-feeding, private, 300-pupil institution for Seattle's elite - and when he arrived there, a gawky, thin, hugely competitive and very bright 11-year-old, the only memorable things about Bill Gates were his size 13 shoes.

The school's decision to get into computing was a watershed in Gates's life. He and his schoolmate Paul Allen, two years his senior, fell in love with that primitive machine (a PDP-10 from Digital) in the spring of 1968, when he was 12. It was seven years later - after Gates dropped out of Harvard, deciding to become an entrepreneur - that the pair of them founded Microsoft.

The mental development involved in the progression from playing with a primitive machine to creating the principal language by which it operates, says much about Gates's character and understanding of this relatively new field. The key is mathematics, for as Gates has said: 'In mathematics, you develop complete characterisations, and you have to combine theorems in very non-obvious ways.'

At mathematics he was clearly very good. On his Scholarship Aptitude Test (SAT, the standard form of admission to US universities) he scored a perfect 800. His speciality was short cuts, and while he and Allen were still at school, they formed a company, the Lakeside Programmers Group. Their aim was to find money-making ways in which to use 'The Machine' in the real world: a foretaste of what was to come.

The obsession became so devouring (Gates would work all night) that though his school work was not suffering - for he was never just a mathematician, and read (and still reads) widely - his parents asked him to give up his computer for a year, which he did. 'I tried to be normal,' he said, 'the best I could.'

But by the time he was 15, Gates was back in business. Lakeside got its first contract; Gates got paid in computer time. That in itself says something about the man: he wasn't just good at computers, he knew how to cut a deal. Off to Harvard in 1973, he said matter-of-factly, 'I'm going to make my first million by the time I'm 25.'

Back in Washington, Allen kept their business going, but both already knew where they were really heading; the computer revolution (a computer in every home, accessible and easy to use) was on its way, and Allen kept insisting they ought to start a real business and get in on the ground floor.

This they did in a number of dazzling steps: first devising, and selling even before they started work on it, a computer language, Basic, which was easier to use than the then available Fortran and Cobol; then, in 1975, when Gates was still 19, setting up Microsoft. There is a splendid photograph of the fewer than a dozen staff of Microsoft - it now has more than 8,000 employees - taken in 1978. At the front is Gates, a 23-year-old looking barely 16, surrounded by the bearded, long-haired denizens of the Sixties, with Paul Allen as Tagore-like guru.

His understanding of both aspects of running a software company (unlike Allen, he was not interested in hardware) - the language needed to operate computers, and perceiving market needs - was evident from the start, and nowhere more clearly stated than in his credo: 'Does it work, is it fast, is it small, does it get it done?'

In 1980, from the tiny Satellite Computer Products, and for the bagatelle of dollars 50,000 (then worth pounds 21,500), he bought the 86-DOS operating system, rewrote it, renamed it MS-DOS and licensed it to IBM; by buying an existing programme he saved a year's development work. MS-DOS provided a way to enable the programs people do their everyday work with, such as word processors or spreadsheets, to be sold for use on IBMs or the many clone computers made by various manufacturers. You could buy the programs in a box and know they would work. And, because Bill Gates retained ownership of MS- DOS, for every machine they worked on, he sold another copy of his system.

It is the blend of entrepreneurship, vision and business acumen, along with his energy and ambition, that has put Gates in his present position. Something of a tyrant inside his own company, feared and respected by his competitors, he understood early the value of intellectual property - which may well turn out to be the basis of future capitalism.

Deeply reclusive, given to obsessive rocking (from a childhood encounter with a rocking horse), off-blond, wispy, thick-lipped, bespectacled, Gates remains subject to violent mood swings and the kind of straightforward cruelty towards his peers that characterises schoolboy confrontations. One writer has described him as an ageing Dennis the Menace; Gates describes himself as 'possessing the cleverness of youth'.

That cleverness is largely a matter of two things: a formidable memory (even for lowly detail) and a vision of the future. From MS-DOS, Gates moved on towards the phenomenally successful Windows program (though only after an initial failure and a deep crisis within the company); and latterly into Multimedia - computer-driven learning and entertainment devices through television and graphics.

The cost to him, one could say, is his life. The drive to the office, meetings, hours spent on his electronic mail and on the cellular phone in his Lexus, rare holidays (one was spent just reading on a chartered yacht off Australia), eating at his desk, constant fear (of becoming

outdated in the volatile world of computers) and aggressive marketing, have

in a way denied him a true progression to maturity.

He and his family both expect him to marry and settle down, but though there are girlfriends, Gates shows no signs of accepting that form of personal responsibility. 'Kids are a problem,' he once said in an unguarded moment to some industry acquaintances at a forum in Arizona. A few seconds later, he added, 'Babies are a subset.'

Or, as a friend of long standing said: 'Bill consciously tries to maintain this nine-year-old in him. That's why he doesn't want to get married, because you can't be nine years old and be married. When you are married, you become your parents.'

That's what Gates is: a nine-year-old entrepreneur, still a whiz-kid and a subset of one.