Hard to understand, difficult to work with and deemed irreplaceable by many Apple fans and investors, Steve Jobs has made a life defying conventions and expectations.

And despite years of signs of poor health, his resignation as chief executive of Apple Inc caused a global gasp as the world contemplated the future of an icon and the company he symbolizes.

“Steve Jobs is the most successful CEO in the U.S. of the last 25 years,” said Google Inc Chairman Eric Schmidt, who used to sit on Apple’s board but stepped down because of overlapping business interests.

“He uniquely combined an artist’s touch and an engineer’s vision to build an extraordinary company, one of the greatest American leaders in history,” Schmidt said in a statement.

A college dropout, Jobs floated through India in search of spiritual guidance prior to founding Apple — a name he suggested to his friend and co-founder Steve Wozniak after a visit to a commune in Oregon he referred to as an “apple orchard.”

With his passion for minimalist design and marketing genius, Jobs changed the course of personal computing during two stints at Apple and transformed the mobile market.

The iconic iPod, the iPhone — dubbed the “Jesus phone” for its quasi-religious following — and the iPad are the creation of a man known for his near-obsessive control of the product development process.

Greatest CEO in the history of man

“Most mere mortals cannot understand a person like Steve Jobs,” Guy Kawasaki, a former Apple employee who considers Jobs “the greatest CEO in the history of man”, said recently. “He’s just got a different operating system.”

Charismatic, visionary, ruthless, perfectionist, dictator – these are some of the words that people use to describe the larger-than-life figure of Jobs, who may be the biggest dreamer the technology world has ever known, but also a hard-edged businessman and negotiator through and through.

“Steve Jobs is the business genius of our generation,” former eBay Inc chief Meg Whitman said recently. “His contributions to Apple, his contributions to technology, frankly his contributions to America, are unparalleled in the business world. He is amazing.”

Former nemesis Bill Gates, the co-founder of Microsoft, has called Jobs the most inspiring person in the tech industry and President Barack Obama has held him up as the embodiment of the American Dream

Success story

It’s hard to imagine a bigger success story than Steve Jobs, but rejection, failure and bad fate have been part and parcel of who he is. Jobs was given away at birth, driven out of Apple in the mid-80s and struck with cancer when he finally had regained the top of the mountain. His resignation as CEO on Wednesday comes at the relatively young age of 55.

“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.

A source close to Jobs said he plans to be active in his new role as chairman of Apple’s board.

Jobs grew up with an adopted family in Silicon Valley, which was turning from orchards to homes for workers at Lockheed and other defense and technology companies.

Electronics friend Bill Fernandez introduced him to boy engineer Wozniak, and the two Steves began a friendship that eventually bred Apple Computer.

“Woz is a brilliant engineer, but he is not really an entrepreneur, and that’s where Jobs came in,” remembers Fernandez, who was the first employee at Apple.

Wozniak said that his goal was only to design hardware and he had no interest in running Apple.

“Steve Jobs’ role was defined — you’ve got to learn to be an executive in every division of the company so you can be the world’s most important person some day. That was his goal,” recently joked Woz, who is still listed as an employee reporting directly to Jobs, even though he has not worked at Apple for years.

Jobs created Apple twice — once when he founded it and the second time after a return credited with saving the company, which now vies with Exxon Mobil as the most valuable publicly traded corporation in the United States.

“Every day to him is a new adventure in the company,” said Jay Elliot, a former senior vice president at Apple who worked very closely with Jobs in the eighties. “He is almost like a child when it comes to his inquisitiveness. Steve has such a thirst of understanding for what’s going on in the company. What he is intolerant about it – politics, bureaucracy.”

But the inspiring Jobs came with a lot of hard edges, oftentimes alienating colleagues and early investors with his my-way-or-the-highway dictums and plans that were generally ahead of their time.

Elliot was a witness to the acrimony between Jobs and former Apple Chief Executive John Sculley who often clashed on ideas, products and the direction of the company.

The dispute came to a head at Apple’s first major sales meeting in Hawaii in 1985 where the two “just blew up against each other,” Elliot said.

Jobs left soon after, saying he was fired.

“It was awful-tasting medicine, but I guess the patient needed it. Sometimes life’s gonna hit you in the head with a brick. Don’t lose faith,” he told a Stanford graduating class in 2005. He returned to Apple about a decade after he left, working as a consultant. Soon he was running it, in what has been called Jobs’ second act.

To this point, he has reinvented the technology world four or five times, first with the Apple II, a beautiful personal computer in the 1970s; then in the 1980s with the Macintosh, driven by a mouse and presenting a clean screen that made computing inviting; the ubiquitous iPod debuted in 2001, the iPhone in 2007 and in 2010 the iPad, which a year after it was introduced outsold Macs.

[Via Reuters and Streamfile]