Apple said Steve Jobs resigned as CEO, effective immediately.

The company said Wednesday that Jobs will be replaced by Tim Cook, who was the company's chief operating officer.

It said Jobs has been elected as Apple's chairman.

In Jobs' letter to the Board he wrote, "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."

The move appears to be the result of an unspecified medical condition for which Jobs took an indefinite leave from his post in January. That was Jobs' third medical leave over several years. He had previously survived pancreatic cancer and received a liver transplant.

At the Apple store in Soho Wednesday night, most people had not yet heard about Jobs' resignation. One customer, Hugh Fox, 38, was shocked to learn Jobs had stepped down. "I'm definitely worried in the short-term," said Fox, who also holds Apple stock and teaches business and management at the New School. "I don't expect the culture at Apple to change."

Allan Shuster, 28, who just purchased two laptops and an iPad as gifts, was not too surprised by the news. He also doesn't think Jobs' departure will affect the company. "They're on a pretty strong path," Shuster said. "Jobs is a strong figure head, but he's been sick for awhile. But hopefully, he's alright."

The board praised Jobs' vision and leadership. Art Levinson, Chairman of Genentech released a statement on behalf of the board. "Steve has made countless contributions to Apple's success, and he has attracted and inspired Apple's immensely creative employees and world class executive team. In his new role as Chairman of the board, Steve will continue to serve Apple with his unique insights, creativity and inspiration."

Jobs co-founded Apple and was the force behind many of the company's visionary products, such as the iPhone, iPod and the iPad.

Jeff Garmet, managing editor of "The Mac Observer" said Jobs had been telegraphing this coming change for several years. "All Apple really has done is made official what they've been doing administratively for a while now, which is Tim runs the show and Steve gets to do his part to make  sure the products come out to meed the Apple standard," he said. He described the significance of the resignation as more sentimental than practical.

Jobs recommended Tim Cook succeed him as CEO. Cook had previously be Apple's Chief Operating Officer.

But Trip Chowdhry, an analyst with Global Equities Research, took a different view of the announcement saying that Apple without Steve Jobs is nothing. "Apple is Steve Jobs, Steve Jobs is Apple, and Steve Jobs is innovation," Chowdhry said. "You can teach people how to be operationally efficient, you can hire consultants to tell you how to do that, but God creates innovation."

With the Associated Press