Former chief executive and co-founder of US technology giant Apple Steve Jobs has died, the company says. He was 56.
"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," Apple said.
Jobs announced he was suffering from pancreatic cancer in 2004.
Microsoft boss Bill Gates said Jobs' "profound impact" would " be felt for many generations to come".
Mr Gates added: "For those of us lucky enough to get to work with him, it's been an insanely great honour. I will miss Steve immensely."
US President Barack Obama also paid tribute: "Michelle and I are saddened to learn of the passing of Steve Jobs. Steve was among the greatest of American innovators - brave enough to think differently, bold enough to believe he could change the world, and talented enough to do it."
And New York Mayor Michael Bloomberg said that "America lost a genius who will be remembered with Edison and Einstein, and whose ideas will shape the world for generations to come".'The face of Apple'
In the statement Apple said: "Apple has lost a visionary and creative genius, and the world has lost an amazing human being".
"Steve leaves behind a company that only he could have built, and his spirit will forever be the foundation of Apple."
Jobs had built a reputation as a forthright and demanding leader who could take niche technologies - such as the mouse and the graphical window-based interface - and make them popular with the general public.
He introduced the colourful iMac computer, the iPod and the iPhone to the world. His death came just a day after Apple unveiled its latest iPhone 4S model.
In 2004, Jobs announced that he was suffering from pancreatic cancer and he had a liver transplant five years later.
In January, he took medical leave, before resigning as CEO in August and handing over his duties to Tim Cook.
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."
However, Jobs stayed on as Apple's chairman.
More than almost any other business leader, he was indistinguishable from his company, which he co-founded in the 1970s.
Apple - whose market value is estimated at $351bn (£227bn) - is now the world's most valuable technology company. Only oil giant Exxon Mobil is worth more.
As the face of Apple, Jobs represented its dedication to high-end technology and fashionable design.
And inside the company he exerted a level of influence unheard of in most businesses.
Despite a high profile, however, he remained fiercely protective of his private life.
He married his wife Laurene in 1991, and the couple had three children.
Jobs also leaves a daughter from a previous relationship, and as an adult discovered that he had a biological sister, US novelist Mona Simpson.