Steve Jobs, the charismatic chairman and co-founder of Apple, has died. He was 56.

Jobs, who president Barack Obama described as "a visionary", had an extraordinary influence on the world of technology and entertainment: Apple ignited the personal computer revolution, popularised the graphical user interface, reinvented the PC, and invented the iPod, iPhone and iPad.

Jobs also co-founded and was CEO of Pixar Animation Studios and served on Disney's board of directors.

Sowing Apple's seeds

Jobs was born in San Francisco in 1955, the son of students Abdulfattah Jandali and Joanne Schieble. As his parents were unmarried, Jobs was put up for adoption. He was adopted by Paul and Clara Jobs, who named him Steven Paul, and when Jobs was very young the family moved to Santa Clara County in California.

While still in high school, Jobs attended lectures by the Hewlett-Packard Company. Jobs would spend a summer working for the firm, where he met his future colleague Stephen Wozniak.

After he graduated from Homestead High School, Jobs enrolled at Reed College in Portland, Oregon, but he dropped out after one semester. Jobs continued to attend classes at the school, however, and credits a calligraphy class as the root of his interest in typography - an interest that would inspire the Macintosh's fonts many years later.

Jobs returned to California in 1974, where he attended the Homebrew Computer Club with Steve Wozniak. Jobs took a job as a technician at Atari, using his wages to fund a trip to India from which he returned a Buddhist, and during this period Jobs also experimented with psychedelic drugs.

Jobs described his psychedelic experiences as "one of the two or three most important things I have done in my life". Jobs' countercultural background was a crucial part of his personality: he would later describe Apple as standing "at the intersection of technology and the liberal arts."

Jobs wasn't particularly technical, but he had a keen business sense - and that means he was quick to spot the potential of the personal computer, and of Steve Wozniak's engineering abilities. Apple was founded in Jobs' parents' garage, and 1977's Apple II was a runaway success. By 1980 Steve Jobs was worth $165 million.

Making the Mac

In the late 1970s personal computers, including Apple's, required users to type commands to make anything happen - but Xerox's Palo Alto Research Center, PARC, had a better idea.

Its graphical user interface used a mouse to control an on-screen pointer, which users could then use to click on little pictures, or icons. Many technology executives visited PARC and saw the technology, but only Jobs saw its potential.

Jobs masterminded the Apple Lisa, a powerful but expensive machine that Apple refined and called the Macintosh. The Macintosh, or Mac, was launched in 1984 and became the first successful personal computer with a graphical user interface.

Apple's success was bittersweet for Jobs: it was great for his ego but introduced big-company problems including bitter in-fighting and power struggles. By September 1985 Jobs had had enough, and resigned from Apple to create a new company. He ended up involved with two: a new computer company called NeXT, and Lucasfilm's ailing computer animation studio Pixar, which Jobs bought.

Both firms were hardware companies - Pixar made the Pixar Image Computer, a high-end graphics system - but Jobs refocused the firms to concentrate on software (NeXT) and animation (Pixar). The latter was so successful that Jobs sold Pixar to Disney in 2006 for $7.4 billion. NeXT's software, meanwhile, would play a crucial part in Apple's future - and it would bring Jobs back to the firm he founded.

Bringing it all back home

Apple foundered without Jobs, embarking on ill-fated ventures including licensing Apple's operating system to third-party manufacturers. The beleaguered firm acquired NeXT in 1996 and hired Jobs as an adviser. CEO Gil Amelio left Apple the following July, and Jobs became Interim CEO.

Jobs brought focus to the company, shuttering the licensing programme, closing multiple projects, migrating Macs from the classic Mac OS to a new, NeXT-based platform and promoting designer Jonathan Ive to Senior Vice President of Industrial Design.

In Ive, Jobs found the Paul McCartney to his John Lennon: a prodigiously talented designer who shared his vision and obsession with detail. Together they would create the candy-coloured iMac, the iPod, the iPhone and the iPad, not to mention some of the world's most impressive and beautiful desktop and portable computers.

Apple's products were runaway successes and often imitated, but they were rarely bettered - partly because Jobs also recognised the importance of the ecosystem surrounding a product.

iPods needed music and later, video, so Apple created the iTunes Store to sell music and video; it's currently the largest music retailer in the world. The iPhone enabled developers to create apps, small downloadable programs, so Apple created an App Store to deliver apps, provide quality control and pay developers. The App Store is currently the world's largest.

The combination of innovative hardware, exceptional design and supporting Stores and services has led to an extraordinary turnaround for Apple: under Jobs' watch, a firm that seemed doomed in the 1980s has become the most valuable technology company in the world.

One more thing

Jobs wasn't just a visionary: he was a showman too, famed for his superb presentation skills and the "reality distortion field" where his personal charisma made even the dullest product sound life-changing.

Jobs' keynote speeches were more like rock concerts than product announcements, generating headlines that other technology firms could only dream of.

The reality distortion field wasn't the only criticism of Jobs, however. Some saw him as arrogant, and in 2010 Forbes Magazine listed Jobs in both its "America's best bosses" list and its "bully boss hall of fame".

Jobs' temper was legendary, and as CNN reported in 2008, "he parks his Mercedes in handicapped spaces, periodically reduces subordinates to tears, and fires employees in angry tantrums. Yet many of top deputies at Apple have worked with him for years, and even some of those who have departed say that although it's often brutal and Jobs hogs the credit, they've never done better work."

Jobs' health

In 2003, Jobs was diagnosed with pancreatic cancer, a diagnosis he wouldn't announce publicly until he wrote to Apple staff in early 2004. Jobs initially resisted the idea of surgery, preferring instead to try a special diet, but in July 2004 he relented.

The surgery was successful, and in 2005 Jobs delivered a commencement speech at Stanford University where he explained how his cancer diagnosis had affected his worldview. "Have the courage to follow your heart and your intuition," he said. "They somehow already know what you truly want to become. Everything else is secondary."

Despite frequent denials from Apple, speculation over Jobs' health continued, peaking in 2008 with Jobs' gaunt appearance at the Worldwide Developers' Conference and Bloomberg's accidental publication of a pre-written obituary.

That September, Jobs took to the stage in front of Mark Twain's quote "rumours of my death are greatly exaggerated". However, in January 2009 Jobs wrote once again to Apple staff, explaining that he would be taking a six-month leave of absence as "my health-related issues are more complex than I originally thought."

Jobs had a liver transplant in April 2009, but in January 2011 Apple once again announced that Jobs would be taking a medical leave of absence. Jobs continued to work at Apple and appear at Apple events, but in August 2011 he formally resigned from the company.

"I have 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," he wrote. "Unfortunately, that day has come."

Steve Jobs died on 5 October 2011. He is survived by his wife, Laurene, and his four children.