In his speech before the graduating students of Stanford University last year, Mr Jobs looked back fondly on his and Mr Wozniak's ascent at Apple.

'We worked hard, and in 10 years Apple had grown from just the two of us in a garage into a US$2 billion company with over 4,000 employees. We had just released our finest creation - the Macintosh - a year earlier, and I had just turned 30.'

It was also during that time that the expression 'reality distortion field' was coined by Macintosh developer Bud Tribble, now Apple's vice-president of software technology.

The term was used to describe Mr Jobs' ability to convince people to believe almost anything with a deft combination of charisma, exaggeration and shrewd marketing. Within that field, a person's sense of proportion is skewed. Small developments are seen as turning points and interesting advances are regarded as breakthroughs.

That worked especially well with Mr Jobs' relationship with Apple's hard-working engineers and the media, who largely helped prop up his credentials as a visionary.

Despite Mr Jobs' 'mojo', he experienced a painful April Fools' joke - only it was true. He was kicked out of the company in 1985 by his hand-picked successor, the former PepsiCo president John Sculley. 'How can you get fired from a company you started?' Mr Jobs said.

Mr Jobs founded a new company called NeXT. It offered powerful, expensive and beautiful workstations, but these did not sell well. So NeXT morphed into a software firm, nurturing its Unix-based operating system.

Apple, meanwhile, was growing and diversifying. In 1991, it introduced what would become the model for notebook PCs - the PowerBook 100. That same year, it unveiled the seventh and much lauded upgrade of its Macintosh operating system. Mr Jobs, apparently, was not missed.

But Apple steadily fell from grace, as Bill Gates and his software company Microsoft started its quick climb to the top of the PC market. Unlike Apple, Microsoft aggressively licensed its operating system to computer manufacturers until its Windows environment became the undisputed world market share leader.

Under Mr Sculley, Apple diversified into consumer electronics with the Newton personal digital assistant - a predecessor of the Palm Pilot - and the QuicTake digital camera. They both failed to live up to their hype and were discontinued.

Various new computer models were also developed and released at huge cost. But more businesses and consumers chose Windows-based PCs.

Those failures led to successive changes in leadership. By 1993, Mr Sculley was out. Former Apple Europe president Michael Spindler was chief executive until 1996, when turnaround specialist and former National Semiconductor chief executive Gil Amelio took over.

Under Mr Amelio, Apple decided to ensure its future by looking back to its founder. In February 1997, it purchased the NeXT operating system to pave the way for Mr Jobs' return.

After presiding over continued financial losses and a record low for company shares, Mr Amelio was ousted by the board and Mr Jobs took on the role of interim chief executive.

After successfully launching the all-in-one, multicoloured iMac computer and bringing Apple back in the black, Mr Jobs was well ensconced once again as the company's leader and visionary.

Although the iMac became a rallying cry for the Mac faithful worldwide, Apple continued to lose share in the desktop computer arena. Apple shipped 104,663 units of its flagship Power Macintosh desktop worldwide in 1998, but that number dwindled significantly over the years to hit a new low of 48,714 units last year.

Mr Jobs took what was arguably his biggest gamble when Apple entered the music and entertainment industry via its 5-gigabyte iPod media player in 2001, with the iTunes online music store following two years later.

'This will go down in history as a turning point for the music industry,' Mr Jobs told Fortune magazine ahead of the iTunes launch. 'This is landmark stuff. I can't overestimate it.'

In fact, few others predicted in either the iPod or iTunes the snowball effect that would see Apple dominate the internet music and device market to a similar degree that long-time rival Microsoft has enjoyed with computers.

Since their respective launches, more than 43 million iPods have been sold and a billion iTunes Music Store songs downloaded online. The two businesses accounted for about 39 per cent of Apple's total revenues last year.

But iTunes' success has had little impact on iPod owners in Asia. Not only has the company been slow to launch stores in the region - Japan and Australia remain the only two - it has limited the purchasing power of iPod users in Hong Kong, the mainland and elsewhere: they can only purchase songs in existing stores if they have credit cards from those countries.

And the oldest criticism of iTunes - its lack of subscription pricing - has not gone away.

Proposed legislation in France also threatens to undermine Apple's exclusive platform by forcing the company to share its digital rights management technology with other online distributors. Observers say Apple would rather retreat from the French market than abandon its present policy.

When Mr Jobs returned to Apple, he brought back the policy of secrecy he had cultivated at NeXT.

Although secrecy has helped in surprising the market with new products, it has hurt Apple's share price performance because investors and the media are uncertain about the company's next release, according to research from United States-based FTN Midwest Securities.

'We continue to believe if Apple told customers more about the iPod and the Macintosh product pipeline, investors would get more comfortable with the company and its stock,' FTN Midwest said.

When the South China Morning Post asked Apple Hong Kong last week about its plans for celebrating the company's 30th anniversary, the regional spokeswoman said: 'We don't know and we don't comment on any rumours.'

An earlier e-mail request sent by the Post to Apple's corporate communications offices in the US and Asia for archived product images was neither acknowledged nor answered.

The cult of secrecy surrounding Apple extends beyond its relationship with the mainstream media to the blogosphere and the new generation of user-generated content it helped to create.

Not only has Apple sued prominent fan blogs, such as AppleInsider and ThinkSecret, for releasing information about future products, it has also adopted a closed door policy regarding employee blogs, in stark contrast to Microsoft and Sun Microsystems, according to an Edelman and Intelliseek report last year.

Apple employees are forbidden to comment on anything relating to Apple on their blogs or post information in any capacity on Mac-related forums.

'The strictness of this policy stands in interesting juxtaposition to the fact that Apple is a leader in creating and promoting consumer-generated media tools like iMovie, Podcasts on iTunes, RSS and now blogs,' the report said.

Criticism aside, Mr Jobs appears to have plenty up his sleeve. Speculation is rife about Apple rolling out full-length feature films on its iTunes store to be played on a video iPod expected to be released on Saturday.

A recent Morgan Stanley report also predicted a so-called iPhone before the end of the year, further enhancing the appeal of both the Apple and the iPod brand.

Another much-speculated goodie for this Saturday is a new iBook line with Intel Core Duo processors.

But the biggest secret of all could be the identity of Mr Job's successor.

Mr Jobs was diagnosed with pancreatic cancer in 2004, had an operation and survived. But after being burned by handpicked successors at Apple and NeXT before, he could not be faulted for being more careful this time around.

Whatever the future holds for Apple and its Mac faithful, the company's place in history is assured - with or without Mr Jobs' reality distortion field.

A brief history of Apple