From age 13, he was given rare independence. He took off some nights to enjoy free use of the computers at the University of Washington. He spent chunks of time away from home -- much as his dad had done as a kid. He lived for a time in Olympia, where he was a page in the state legislature, and in Washington, D.C. as a Congressional page. During his senior year, he took a break from school to work as a programmer at a power plant in southern Washington. And in what would become his first major collaboration with Paul Allen, his future Microsoft cofounder, Mr. Gates designed the 'Traf-O-Data', a device for counting cars traveling over a section of road.

His parents played supporting roles. They acquiesced when Bill quit Harvard and then moved to Albuquerque, New Mexico, to start Microsoft. It was a tough decision to back.

'Mary and I were both concerned about it -- I think she a bit more than I,' Bill Sr. says. 'Her expectations and mine were very ordinary expectations of people who have kids in college -- that they get a degree.'

The family support was one reason Mr. Gates decided to move Microsoft to Seattle, where he settled into a house not far from his parents. Ms. Gates arranged to have a maid clean her son's house, and made sure he had clean shirts for his big meetings. She also insisted he kept observing the family traditions, including the weekly Sunday dinner at his parents' house.

Mr. Gates Sr., drawing from his own experience as a lawyer guiding small companies, helped find Seattle businesspeople to serve on the Microsoft board. In 1980, Bill Gates brought his father along to dinner to help persuade college friend Steve Ballmer -- now Microsoft's chief executive -- to quit graduate school and join Microsoft. The father's law firm would also end up representing Microsoft, which became the firm's biggest client.

Bill Sr. eased his son's worries about taking Microsoft public when Bill fretted that it would be a distraction for employees. The offering would turn Bill Gates into a billionaire. It also spawned the next challenge for the family.

After the windfall, Ms. Gates pressed her son to get into philanthropy. At his father's law office late one night, someone present recalls, Bill quarreled with his mother as she urged him to give money away.

'I'm just trying to run my company!' he snapped, says the person in the office at the time. Mr. Gates says that at the time he wasn't opposed to philanthropic work, he just didn't want to be distracted from his duties at Microsoft.

Eventually, she got her son to start a program at Microsoft to raise money for the United Way. He also followed his mother onto the national United Way board in the 1980s.

But as Bill Gates's wealth grew, letters from Seattle-area nonprofits asking for donations piled up. He says he planned to get serious about philanthropy after retiring from Microsoft, or at about 60 years old.

That plan would be fast-tracked after Ms. Gates was diagnosed with a rare form of breast cancer. As she battled the disease, she continued to urge her son to do more philanthropy. Ms. Gates passed away in June 1994.

The day of her funeral, the Gates family had dinner at home. Bill Sr. told his children not to worry about him, saying that he had about 10 good years left in him. He was 70 at the time. Still, after his wife died he was listless.

About six months later, standing in a line for a movie with his son and daughter-in-law, Melinda, the elder Mr. Gates again broached the idea of philanthropy. He suggested he could start sifting through the requests for money and give some out.

A week later, the software mogul set aside about $100 million to create a foundation that his father could run. Bill Gates Sr. later sat at his kitchen table and wrote the first check, $80,000 to a local cancer program.

In the early days, Mr. Gates Sr., who soon remarried, would scribble a few notes on the most-promising requests for donations. He would then put them in a cardboard wine box that he periodically sent to his son's house. The box would come back with Bill Jr.'s responses. Mr. Gates Sr. would then reply to all the grant seekers, sometimes including a $1 million check with little more than a single-page letter of congratulations.

Bill Sr. and a former Microsoft executive managed the foundation, doling out money, overseeing a staff of hundreds and expanding its purview to areas like education and vaccines.

Mr. Gates Sr. says he hasn't lost sight of the fact that he was playing the role of caretaker until his son and daughter-in-law took the helm. And after 53 years, he knows to give his son space.

'He has very fixed ideas of some things,' says Mr. Gates Sr. 'The dynamic of the family is that you don't cross him on those things, because it's a waste of time.'