Jobs kept a close cadre of friends, Bajarin said, including John Lasseter of Pixar and Larry Ellison of Oracle, but beyond that, shared very little of his personal life with anyone.
But that personal life -- he was given up at birth for adoption, had an illegitimate child, was romantically linked with movie stars -- was full of intrigue for his fan base and Apple consumers.
Jobs and his wife, Laurene Powell, were married in a small ceremony in Yosemite National Park in 1991, lived in Woodside, Calif., and had three children, Reed, Erin and Eve.
He admitted that when he was 23, he had a child out of wedlock with his high school girlfriend, Chris Ann Brennan. Their daughter, Lisa Brennan Jobs, was born in 1978.
He had a biological sister, Mona Simpson, the author of such well-known books as "Anywhere But Here." But he did not meet Simpson until they were adults and he was seeking out his birth parents. Simpson later wrote a book based on their relationship. Its title: "A Regular Guy."
Fortune magazine reported that Jobs denied for years that he was the father of Lisa Brennan Jobs, at one point swearing in a court document that he was infertile and could not have children. According to the report, Chris Ann Brennan collected welfare for a time to support the child until Jobs later acknowledged Lisa as his daughter.
There were other personal details that emerged over the years, as well.
At Reed, Jobs became romantically involved with the singer Joan Baez, according to Elizabeth Holmes, a friend and classmate. In "The Second Coming of Steve Jobs," Holmes tells biographer Alan Deutschman that Jobs broke up with his serious girlfriend to "begin an affair with the charismatic singer-activist." Holmes confirmed the details to ABC News.
Jobs' Health and Apple's Health
Enigmatic and charismatic, Jobs said little about himself. But then his body began to fail him.
In 2004, he was forced to say publicly he had a rare form of pancreatic cancer. In 2009, it was revealed that he had quietly gone to a Memphis hospital for a liver transplant.
In 2009, sources said, members of Apple's board of directors had to persuade him to disclose more about his health as "a fiduciary issue," interwoven with the health of the company.
He was listed in March as 109th on the Forbes list of the world's billionaires, with a net worth of about $8.3 billion. After selling Pixar animation studios to The Walt Disney Company in 2006, he became a Disney board member and the company's largest shareholder. Disney is the parent company of ABC News.
Analysts said Apple performed well during Jobs' absence, partly because he was available for big decisions and partly because his chief lieutenant, Tim Cook, was the hands-on manager even when Jobs was there.
The company has a history of bouncing back. In January 2009, after he announced his second medical leave, Apple stock dropped to $78.20 per share. But it quickly recovered and became one of the most successful stocks on Wall Street. On one day in the summer of 2011, with the stock hitting the $400 level, Apple briefly passed ExxonMobil as the world's most valuable company.
ABC News' Neal Karlinsky, Gregory J. Krieg, Alex Stone and Catherine McKenzie contributed to this report.