Steve Jobs, co-founder of Apple Inc., resigned as chief executive officer, but will continue at the company that revolutionized consumer electronics as chairman of the board, according to reports.

Jobs tendered his resignation on Wednesday, ending a 14-year reign at Apple, a tech-giant company that he co-founded in a garage.

Apple shares slid to $357.40 in extended trading after a brief halt. They had gained 0.7 percent to close at $376.18 on the Nasdaq.

Much of the day-to-day work were handed over to COO Tim Cook, who will become the new CEO effective immediately.

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. Unfortunately, that day has come, he said in a brief letter announcing his resignation.

That he has relinquished daily control isn't all too surprising because it was widely anticipated after Jobs took an extended medical leave earlier this year. The 55-year-old briefly emerged from his medical leave in March to unveil the iPad 2 tablet computer, and later to attend a dinner hosted by President Barack Obama for technology leaders in Silicon Valley.

He also showed up this summer at Apple's Worldwide Developer Conference in San Francisco to introduce iOS 5, and the forthcoming iCloud service.

Jobs had a liver transplant two years ago and also underwent surgery for pancreatic cancer seven years ago.

Neither the company nor Jobs has mentioned his health since he took a leave in January, telling employees in an internal memo he had learned that my health-related issues are more complex than I originally thought.