Steve Jobs, the iconic founder and longtime CEO of Apple, resigned his CEO position Wednesday and has been elected Chairman of the Board.
Jobs will be replaced as CEO by Tim Cook, who had been serving as COO. In addition to his position as CEO, Cook will become a member of the Board of Directors, Apple said.
No reason was given for the resignation, and Apple did not respond to a request for more information. In his letter of resignation to the Board, Jobs said that the day has come, "when I could no longer meet my duties and expectations as Apple’s CEO."
Jobs has had a history of dealing with cancer. He was treated for pancreatic cancer in 2004 and had a liver transplant in 2009.
Jobs took an unexpected medical leave of absence starting January 17 of this year. In February, there were concerns that he might have as few as six weeks to live.
He eventually returned to work in March to oversee the launch of Apple's iPad 2.
Despite concerns that Apple's business might suffer without Jobs as CEO, the company has continued its stellar growth on the basis of its iPad, iPhone, and Macintosh PC lines.
Investors took a dim view of Jobs' resignation, causing the company's share prices to fall 5 percent in after-hours trading.
Under Jobs, Apple developed mobile devices and smart devices that drove the company to become the largest publically-listed company in the world in August when its market capitalization passed that of Exxon. That is a far cry from 1997 when Apple received a cash investment of $150 million from Microsoft that helped it shore up its shrinking computer business at a time when it had only a 3 percent market share.
Next: Cook's Apple History And Jobs' Resignation Letter