Steve Jobs resigned Wednesday as chief executive of Apple, marking an end to his 14-year reign at the consumer electronics giant he co-founded in a garage.

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.

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

The wording and timing of the announcement raised questions about Jobs' health, who was diagnosed with a rare form of pancreatic cancer in 2004 and underwent a liver transplant two years ago.

In 2008, Jobs lost a lot of weight, and Apple put out the following statement: doctors think they have found the cause - a hormone imbalance that has been 'robbing' me of the proteins my body needs to be healthy.... The remedy for this nutritional problem is relatively simple and straightforward, and I've already begun treatment.

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.

Most of the day-to-day duties were handed over to chief operating officer Tim Cook, who will become the new CEO effective immediately.

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.

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