BILL GATES is famous for his inability to sit still. In meetings he rocks back and forth with pent-up energy, as if he were a small boy waiting to burst from his chair. When walking down halls he has been known to spontaneously leap upward. If he ever jumps as successfully as he runs a business he'll be the first human to reach orbit from a standing start. Critics may call him a monopolist, decry his business tactics, and complain Microsoft technology isn't that great. But it's hard to deny that William Henry Gates III is one of the most successful business leaders of this or any other age, for that matter. He's America's richest man, the king of computer techies, the patron saint of those who wear pocket protectors. To millions worldwide he is the most visible symbol of a technological revolution. To others, he symbolizes the danger that this revolution is concentrating power too narrowly. The CEO of Microsoft Corporation may be better groomed now than he was when the personal-computer software industry was a relative business backwater. He no longer walks around with his glasses as dirty as an old windshield. His hair is better cut, his clothes more expensive. Not that this means he wears Armani suits. At a recent presentation on interactive TV, the Internet, and ''wallet PCs'', Gates spoke wearing an argyle sweater. What hasn't changed is his passion for technology: seeing a computer in every home, on every desk, and ''information at your fingertips.'' Having carved out a virtual monopoly in the basic software that runs PCs, he is busy trying to expand into new fields of technology. Yet success doesn't seem to have gone to his head, analysts say. He is so competitive that he runs scared even in areas where Microsoft dominates. ''Gates is as tight with a buck as he ever was,'' says Mark Macgillivray, managing director of H&M Consulting in Sunnyvale, Calif. Gates watches that Microsoft's division's don't get flabby even as they add workers and rush to create new products. Others in the industry have as clear a sense of where technology is headed over the next 20 years. Gates is known more as a shrewd businessman than as a technical wizard or visionary futurist. He stands apart in his ability to map out orderly steps to make the vision reality, says Jesse Berst, editorial director of Windows Watcher, a newsletter about Microsoft. Gates is ''a chess player who can see several moves ahead of his opponents,'' Mr. Berst says. ''His timing is impeccable,'' agrees Mark Anderson, a consultant and founder of Technology Alliance Partners in Friday Harbor, Wash. But it is not clear whether Gates, who loves strategy games such as bridge and poker, will be able to keep his winning streak alive indefinitely. Observers say Microsoft's dominance of the software industry could be stopped by an unforeseen technology shift, or by the actions of rivals or government antitrust lawyers. The company could even be slowed by its sheer size and scope of its own activities. Gates can no longer take the hands-on approach, Berst says. Gates himself appears to understand the ephemeral nature of power in fast-paced technological markets, which is one reason why he shrugs off concerns about Microsoft's hegemony. ''This is a business where no one has a guaranteed future,'' he said at a recent appearance here while promoting Windows 95, the upgrade of Microsoft's core product that debuts this week. Branching out from software, Gates is personally investing in Hollywood's hot new studio team, known as DreamWorks SKG, which includes film director Steven Spielberg. And he is moving Microsoft into the burgeoning world of online services: The Microsoft Network debuts this month, offering people a dial-up world of information for a monthly fee. ''Bill sees the Internet as the greatest threat to Microsoft's domination for the second half of the decade,'' Berst says. The global computer network emphasizes connections between computers, and networking has long been Microsoft's weak link. But Gates is sure to make his company a strong player in this market, observers say. Microsoft's dominance has spawned mixed feelings of admiration and angst among industry rivals and computer users. Many people - including many software companies - are grateful there is a standard platform (Windows) on which to build ''applications,'' programs such as games or accounting software. Gates has become a powerful symbol to a generation that sends its children to computer camps, loves to try new electronic gadgets, and dreams of the freedom of entrepreneurship. But success has also made him a target of criticism. Such ''Bill-bashing,'' as it is known in the industry, is hard to overcome since the man's empire sparks envy. But some Gates supporters say he should shine up his image by showing a ''human'' side more. To some extent that appears to be happening. He married Melinda French on New Year's Day, 1994. The couple zealously guards their privacy. He will soon take a two-week vacation - an unusual respite - in China. He donates millions of dollars to favorite charities and has promised, ultimately to give the bulk of his fortune away. But some analysts say his business drive has been softened little. The competitive business spirit goes back to his youth, when the attorney's son negotiated a contract with his sister to use her baseball glove. He began programming computers while in eighth grade at the private Lakeside School near Seattle. Gates and Paul Allen, a friend two years his elder at Lakeside, founded Microsoft in 1975. Many analysts see Allen as more of a technological visionary than Gates. The bearded fan of Jimi Hendrix music has gone on to fund a flock of high-tech firms. Both men have benefitted by good fortune and competitors' mistakes. As Gates told Business Week in a 1992 interview, ''It's silly to think that anybody's innate skills qualify them to this level of success.''