Rich tributes are being paid to Apple Inc's co-founder and former CEO Steve Jobs, who has died at the age of 56.
Barack Obama, the US president, described the man who brought the world the Mac, iPod and iPhone as "among the greatest of American innovators".
Apple's board of directors announced the death in a brief statement on Wednesday, saying: "We are deeply saddened to announce that Steve Jobs passed away today.
"Steve's brilliance, passion and energy were the source of countless innovations that enrich and improve all of our lives. The world is immeasurably better because of Steve."
Tributes flowed in from around the world for Jobs, while Apple fans flooded social networking sites to voice their sorrow at the passing of the man who helped put mini computers in the shape of phones in millions of pockets.
Tim Cook, Apple's current CEO, said: "Apple has lost a visionary and creative genius, and the world has lost an amazing human being. Those of us who have been fortunate enough to know and work with Steve have lost a dear friend and an inspiring mentor."
Jobs leaves behind a company, Cook said, "that only he could have built, and his spirit will forever be the foundation of Apple".
Jobs, who took medical leave in January, stepped down as CEO of Apple last month, handing over his duties to Cook but staying on as the company's chairman.
In his resignation letter, Jobs said: "I believe Apple's brightest and most innovative days are ahead of it. And I look forward to watching and contributing to its success in a new role."
In his tribute, Obama said: "The world has lost a visionary. And there may be no greater tribute to Steve's success than the fact that much of the world learned of his passing on a device he invented."
He was joined by political, technological, entertainment and business leaders around the world in paying tribute to Jobs.
Bill Gates, Microsoft co-founder and chairman, paying tribute to his one-time rival, said: "Steve and I first met nearly 30 years ago, and have been colleagues, competitors and friends over the course of more than half our lives.
"The world rarely sees someone who has had the profound impact Steve has had, the effects of which will be felt for many generations to come. For those of us lucky enough to get to work with him, it's been an insanely great honour."
Jobs was just 21 when he founded Apple Computer in 1976 with a 26-year-old friend, Steve Wozniak, in his family garage.
From such humble beginnings the company, with its ubiquitous trademark of an apple with a bite taken out of it, grew to eventually become one of the world's most valuable firms.
In July, Apple's second quarter profit hit $7.31bn on revenue of $28.57bn.
In his homage to Rupert Murdoch, the CEO of News Corporation, said: "Today, we lost one of the most influential thinkers, creators and entrepreneurs of all time. Steve Jobs was simply the greatest CEO of his generation.
"While I am deeply saddened by his passing, I'm reminded of the stunning impact he had in revolutionising the way people consume media and entertainment. My heart goes out to his family and to everyone who had the opportunity to work beside him in bringing his many visions to life."
Mark Zuckerberg, the founder of the social networking site, Facebook, said Jobs for him was more than an innovator.
"Steve, thank you for being a mentor and a friend. Thanks for showing that what you build can change the world. I will miss you.
Apple was based in California and the state's former governor, Arnold Schwarzenegger, said: "Steve lived the California Dream every day of his life and he changed the world and inspired all of us."
Twitter users from around the world contributed eulogies of 140 characters or less, supplementing obituaries from nearly every major media outlet:
"3 Apples changed the World, 1st one seduced Eve, 2nd fell on Newton and the 3rd was offered to the World half bitten by Steve Jobs."
"Thank you, Steve Jobs, for making technology a delight to use, instead of a necessary evil."
Apple fans were invited to share their thoughts, memories and condolences by sending messages to email@example.com.
And social networking groups were calling for iPhone vigils in public parks across the US.