The name Bill Gates has long been synonymous with the technology industry. But, in about a month, he will step away from his day-to-day job at Microsoft, the company he founded. While remaining as Microsoft's chairman, Mr. Gates will devote much more of his time to the world- renowned charitable foundation he runs with his wife, Melinda French Gates. He leaves a company of enormous size and wealth, one that retains the near-monopoly he built in PC operating systems and Office suites, while struggling to compete with Google in search, advertising and Web applications; and with Apple in music and video devices and services. He also leaves a legacy as the person who, in the words of longtime rival Steve Jobs at D5 last year, was the first to recognize the potential of building a pure PC software company.