Apple's stock was bruised in trading that followed the announcement Wednesday that second-in-command Tim Cook will take over as CEO for Jobs.
"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," Jobs said in his resignation letter. "Unfortunately, that day has come."
Jobs, 56, is seen as the heart and soul of Apple, with analysts and investors repeatedly expressing concern over how the Cupertino, Calif.-based company will fare without its driving force.
"Steve Jobs is the one who brought magic to Apple," said analyst Rob Enderle of Enderle Group in Silicon Valley.
"Like P.T. Barnum or Walt Disney, he has a skill like no other in the industry," he continued.
Apple's share price slid more than 5% to $357.10 in trading that followed news of his resignation.
Gartner analyst Van Baker saw no reason for investors to panic.
"Apple will do just fine," Baker told AFP. "There are so many talented people there, and Steve's attention to detail is baked into the culture."
'An Execution Monster'
Jobs will still be around as chairman of the Apple board and the company has product plans mapped, according to Baker. Apple is expected to launch a fifth-generation iPhone in September or October.
"Apple is an execution monster, and that includes products, supply chain and marketing," Baker said. "Their roadmap is in place; I'm sure they are already working on the next iPad."
Apple last week briefly held the title of the world's most valuable company based on stock price.
"Steve's extraordinary vision and leadership saved Apple and guided it to its position as the world's most innovative and valuable technology company," board member Art Levinson said in a statement.
Jobs's Health Declining?
The Apple statement made no direct mention of Jobs's health, but the announcement will raise fears that his situation is deteriorating.
His battle with pancreatic cancer earlier included a lengthy leave for a liver transplant in 2009.
Cook has been handling day-to-day operations since Jobs went on medical leave in January.
"The board has complete confidence that Tim is the right person to be our next CEO," Levinson said.
"Tim's 13 years of service to Apple have been marked by outstanding performance, and he has demonstrated remarkable talent and sound judgment in everything he does," he continued.
Cook was previously responsible for Apple's sales and operations, including management of the supply chain, sales activities, and service and support in all markets and countries.
A Living Legend in Silicon Valley
Jobs is a living legend in Silicon Valley. He is the beloved visionary behind the Macintosh computer, the iPod, the iPhone and the iPad as well as the iTunes online shop.
Born on Feb. 24, 1955, in San Francisco to a single mother and adopted by a couple in nearby Mountain View at barely a week old, he grew up among the orchards that one day would become the technology hub known as Silicon Valley.
Jobs was 21 and Steve Wozniak 26 when they founded Apple Computer in the garage of Jobs's family home in 1976.
Under Jobs, the company introduced its first Apple computers and then the Macintosh, which became wildly popular in the 1980s.
Jobs was elevated to idol status by ranks of Macintosh computer devotees, many of whom saw themselves as a sort of rebel alliance opposing the powerful empire Microsoft built with its ubiquitous Windows operating systems.
Jobs left Apple in 1985 after an internal power struggle and started NeXT Computer company, specializing in sophisticated workstations for businesses.
He co-founded Academy-Award-winning Pixar in 1986 from a former Lucasfilm computer-graphics unit that he bought from movie-industry titan George Lucas.
Apple's luster faded after Jobs left the company, but they reconciled in 1996 with Apple buying NeXT for $429 million and Jobs ascending once again to the Apple throne.
Since then, Apple has gone from strength to strength as Jobs revamped the Macintosh line, revolutionizing modern culture and launching a "post-PC era" in which personal computers give way to smart mobile gadgets.
Copyright Agence France-Presse, 2011