The death was announced by Apple, the company Mr. Jobs and his high school friend Stephen Wozniak started in 1976 in a suburban California garage.

A friend of the family said that Mr. Jobs died of complications from pancreatic cancer, with which he waged a long and public struggle, remaining the face of the company even as he underwent treatment. He continued to introduce new products for a global market in his trademark blue jeans even as he grew gaunt and frail.

He underwent surgery in 2004, received a liver transplant in 2009 and took three medical leaves of absence as Apple’s chief executive before stepping down in August and turning over the helm to Timothy D. Cook, the chief operating officer. When he left, he was still engaged in the company’s affairs, negotiating with another Silicon Valley executive only weeks earlier.

“I have always said that if there ever came a day when I could no longer meet my duties and expectations as Apple’s C.E.O., I would be the first to let you know,” Mr. Jobs said in a letter released by the company. “Unfortunately, that day has come.”

By then, having mastered digital technology and capitalized on his intuitive marketing sense, Mr. Jobs had largely come to define the personal computer industry and an array of digital consumer and entertainment businesses centered on the Internet. He had also become a very rich man, worth an estimated $8.3 billion.

Tributes to Mr. Jobs flowed quickly on Wednesday evening, in formal statements and in the flow of social networks, with President Obama, technology industry leaders and legions of Apple fans weighing in.

A Twitter user named Matt Galligan wrote: “R.I.P. Steve Jobs. You touched an ugly world of technology and made it beautiful.”

Eight years after founding Apple, Mr. Jobs led the team that designed the Macintosh computer, a breakthrough in making personal computers easier to use. After a 12-year separation from the company, prompted by a bitter falling-out with his chief executive, John Sculley, he returned in 1997 to oversee the creation of one innovative digital device after another — the iPod, the iPhone and the iPad. These transformed not only product categories like music players and cellphones but also entire industries, like music and mobile communications.

During his years outside Apple, he bought a tiny computer graphics spinoff from the director George Lucas and built a team of computer scientists, artists and animators that became Pixar Animation Studios.

Starting with “Toy Story” in 1995, Pixar produced a string of hit movies, won several Academy Awards for artistic and technological excellence, and made the full-length computer-animated film a mainstream art form enjoyed by children and adults worldwide.

Mr. Jobs was neither a hardware engineer nor a software programmer, nor did he think of himself as a manager. He considered himself a technology leader, choosing the best people possible, encouraging and prodding them, and making the final call on product design.

It was an executive style that had evolved. In his early years at Apple, his meddling in tiny details maddened colleagues, and his criticism could be caustic and even humiliating. But he grew to elicit extraordinary loyalty.

“He was the most passionate leader one could hope for, a motivating force without parallel,” wrote Steven Levy, author of the 1994 book “Insanely Great,” which chronicles the creation of the Mac. “Tom Sawyer could have picked up tricks from Steve Jobs.”

“Toy Story,” for example, took four years to make while Pixar struggled, yet Mr. Jobs never let up on his colleagues. “‘You need a lot more than vision — you need a stubbornness, tenacity, belief and patience to stay the course,” said Edwin Catmull, a computer scientist and a co-founder of Pixar. “In Steve’s case, he pushes right to the edge, to try to make the next big step forward.”

Mr. Jobs was the ultimate arbiter of Apple products, and his standards were exacting. Over the course of a year he tossed out two iPhone prototypes, for example, before approving the third, and began shipping it in June 2007.

Steve Lohr contributed reporting.

This article has been revised to reflect the following correction:

Correction: October 5, 2011

An earlier version of this obituary incorrectly identified the city where Mr. Jobs graduated from high school. It was Cupertino, not Los Altos. It also misstated the year in which NeXT shifted its focus from the education to the business market as 1986. The change occurred in 1993.

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