Though long-anticipated because of his bad health, the 154-word resignation letter from Jobs still took everyone by surprise, as his name has been attached with each and every move of Apple and its various products -- almost all of which went on to become fashion statements in the technology world.
Neither 56-year-old Jobs nor California-based Apple offered any reason for the resignation, but it has been speculated that it is on account of his continuing health problems.
Jobs was diagnosed with cancer in 2003 and also went for a liver transplant in 2009, when he had taken a break from the company. Such has been Jobs' association with Apple that his health has been as widely debated as the various highly successful products of his company.
He has passed on the baton to run Apple to 50-year-old Tim Cook, the man who has been running the day-to-day operations of the world's second-most valued company as its Chief Operating Officer and has also served as acting chief in times of Jobs' illness.
Cook headed the company when Jobs went on a two-month medical leave in 2004 for cancer treatment and again for over five months in 2009 for his liver transplant.
While Cook has now become the CEO, Jobs has assumed the role of Chairman with immediate effect, Apple said in a statement.
The leadership change followed a letter sent by Jobs yesterday to the 'Apple Board of Directors and the Apple Community', where he expressed his desire to quit as CEO and proposed Cook as his successor.
"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," Jobs wrote.
Expressing his desire to continue as an Apple employee, a director and Chairman, Jobs said: "I believe Apple's brightest and most innovative days are ahead of it. And I look forward to watching and contributing to its success in a new role."
Investors reacted negatively to Jobs' resignation as the company's share price fell by over 5 per cent in after-market trade in the US last night, while the stock was seen under pressure in Tokyo this morning too.
With a market valuation of about USD 350 billion, Apple is currently ranked as the second-most valuable company in the world. It had briefly replaced energy giant ExxonMobil as the top-valued firm earlier this month.
Trading was suspended in Nasdaq-listed Apple stock yesterday prior to the announcement of Jobs' resignation.
Born in San Francisco on February 24, 1955, Jobs co-founded Apple Computer at the age of 21 in the garage of his family home in 1976 along with Steve Wozniak.
In between, he had left Apple in 1985 after internal board room differences, but came back after nearly 12 years in 1997. In between, he started NeXT Computer, a maker of high-end business workstations, and Pixar, the maker of computer animation films that was later acquired by Walt Disney.
Apple began its journey as a high-end challenger to Microsoft with its sophisticated Mac computers, but it started losing ground during Jobs' 12-year absence.
His return, however, added an intensified vigour to the company, which went on to taste success-after-success with products ranging from its Mac computers to iPod digital music players to iPhone mobile phones and now iPad handheld computing devices.
Known as the 'heart and soul of Apple' and its public face also, Jobs' public appearances had become rare in the recent past due to his illness.
In March this year, he unveiled the second version of the revolutionary iPad and later attended a dinner hosted by President Barack Obama for technology tycoons in Silicon Valley.
In June, he was again on stage in San Francisco to talk about iCloud, Apple's latest foray into cloud-based computing.
Jobs' thin frame and gaunt appearance sparked questions about his health and for how long would he continue to be at the helm of Apple.
Concerns have been raised earlier about Apple' future due to Jobs' illness and his resignation has now further kindled these issues.
However, the company has expressed confidence in its new chief Tim Cook, who has been successfully handling the day-to-day operations in Jobs' absence despite not having been a public face of the company.
Apple Board said in a statement that it has "complete confidence that Tim is the right person to be our next CEO... Tim's 13 years of service to Apple have been marked by outstanding performance and he has demonstrated remarkable talent and sound judgement in everything he does."
As COO, Cook was previously responsible for Apple's worldwide sales and operations, including end-to-end management of Apple's supply chain, sales activities and service and support in all markets and countries.
He also headed Apple's Macintosh division and played a key role in the continued development of strategic reseller and supplier relationships, ensuring flexibility in response to an increasingly demanding marketplace, the company said.