Steve Jobs started Apple with a high-school friend in a Silicon Valley garage in 1976.
He was forced out a decade later but returned in 1997 to rescue the company. During his second stint, it grew into the most valuable technology company in the world.
Cultivating Apple's counter-cultural sensibility and a minimalist design ethic, Mr Jobs rolled out one sensational product after another, even in the face of the late-2000s recession and his own failing health.
He helped change computers from a geeky hobbyist's obsession to a necessity of modern life at work and home, and in the process he upended not just personal technology but the mobile phone and music industries. For transformation of American industry, he has few rivals.
Perhaps most influentially, Mr Jobs in 2001 launched the iPod, which offered "1,000 songs in your pocket." Over the next 10 years, its white earphones and thumb-dial control seemed to become more ubiquitous than the wristwatch.
In 2007 came the touch-screen iPhone, joined a year later by Apple's App Store, where developers could sell iPhone "apps" which made the phone a device not just for making calls but also for managing money, editing photos, playing games and social networking.
And in 2010, Mr Jobs introduced the iPad, a tablet-sized, all-touch computer that took off even though market analysts said no-one really needed one.
By 2011, Apple had become the second largest company of any kind in the United States by market value. In August, it briefly surpassed Exxon Mobil as the most valuable company.
Under Steve Jobs, the company cloaked itself in secrecy to build frenzied anticipation for each of its new products. Mr Jobs himself had a wizardly sense of what his customers wanted, and where demand didn't exist, he leveraged a cult-like following to create it.
When he spoke at Apple presentations, almost always in faded blue jeans, trainers and a black mock turtleneck, legions of Apple acolytes listened to every word. He often boasted about Apple successes, then coyly added a coda - "One more thing" - before introducing its latest ambitious idea.
In later years, Apple investors also watched these appearances for clues about his health. Mr Jobs revealed in 2004 that he had been diagnosed with a very rare form of pancreatic cancer - an islet cell neuroendocrine tumour. He underwent surgery and said he had been cured. In 2009, following weight loss he initially attributed to a hormonal imbalance, he abruptly took a six-month leave. During that time, he received a liver transplant that became public two months after it was performed.
He went on another medical leave in January 2011, this time for an unspecified duration. He never went back and resigned as CEO in August, though he stayed on as chairman. Consistent with his penchant for secrecy, he didn't reference his illness in his resignation letter.
For technology lovers, buying Apple products has meant gaining entrance to an exclusive club. At the top was a complicated and contradictory figure who was endlessly fascinating - even to his detractors, of which Mr Jobs had many. Mr Jobs was a hero to techno-geeks and a villain to partners he bullied and to workers whose projects he unceremoniously killed or claimed as his own.
In the years after his cancer was revealed, rumours about Mr Jobs' health would spark runs on Apple stock as investors worried the company, with no clear succession plan, would fall apart without him. Apple did little to ease those concerns. It kept the state of Mr Jobs' health a secret for as long as it could, then disclosed vague details when, in early 2009, it became clear he was again ill.
Mr Jobs took a half-year medical leave of absence starting in January 2009, during which he had a liver transplant. Apple did not disclose the procedure at the time; two months later, The Wall Street Journal reported the fact and a doctor at the transplant hospital confirmed it.
In January 2011, Mr Jobs announced another medical leave, his third, with no set duration. He returned to the spotlight briefly in March to personally unveil a second-generation iPad and again in June, when he showed off Apple's iCloud music synching service. At both events, he looked frail in his signature jeans and mock turtleneck.
Less than three months later, Mr Jobs resigned as CEO. In a letter addressed to Apple's board and the "Apple community" Mr Jobs said he "always said if there ever came a day when I could no longer meet my duties and expectations as Apple's CEO, I would be the first to let you know. Unfortunately, that day has come".
In 2005, following the bout with cancer, Mr Jobs delivered Stanford University's commencement speech.
"Remembering that I'll be dead soon is the most important tool I've ever encountered to help me make the big choices in life," he said. "Because almost everything - all external expectations, all pride, all fear of embarrassment or failure - these things just fall away in the face of death, leaving only what is truly important."