It sounds like one of Steve Wozniak’s celebrated pranks. Woz, as he likes to be known, the other co-founder of Apple Computer, owner of the first dial-a-joke service in the San Francisco Bay area, took a phone call a few months ago from a friend who invited him to invest in a new company. Nothing odd about that, except there was a catch: it wasn’t allowed to know in advance what it was going to do. ‘It’s a Special Purpose Acquisition Corporation, or Spac,’ says Woz happily, ‘whose job is to acquire some company to do something – which we’re in the middle of doing right now, so I can’t tell you too much about it.’ He admits it’s hard to believe – ‘no one had ever heard of this weird kind of company that could go public and not be allowed to know what it’s doing’ – but he found the unexpectedness of the project instantly attractive. So he said yes.

In fact, the company being acquired, for $260m (£136m), is a California chip foundry called Jazz Semiconductor, which makes super-fast chips that the new owners hope will be at the heart of converging generations of mobile phones and other wireless consumer products. Woz will be chief technology officer, and thus finds himself back in the established corporate world that he hasn’t inhabited since he left Apple in 1985. Woz, a genial, bear-like 56-year-old, is in the UK to promote his as-told-to autobiography, iWoz , and as he emphasises in the book, pranks have done him well. The dial-a-joke line, run from a kitchen in Cupertino, netted him his first wife, one of its customers, before he had to give it up because (typically) it was costing too much. Among the projects on which he honed his nonpareil technical skills were early computer games and the famous ‘blue box’. This was a device for making free long-distance phone calls with which he once narrowly failed to wake up the Pope. On both occasions his partner in crime, as it were, was another prankster by the name of Steve Jobs.

Games are part of what it is to be human. Even in ultra-competitive Silicon Valley most people acknowledge that Woz’s genius as well as fundamental niceness was to import a human quality into the computer – then an array of flashing lights and dials whose only input was through punched cards and only output printouts of incomprehensi ble computerese. Until Woz constructed the Apple I, the computer did not engage with humans. ‘I didn’t realise it at the time, but that day, Sunday, 29 June, 1975, was pivotal,’ he recounts in his book. ‘It was the first time in history anyone had typed a character on a keyboard and seen it show up on the screen in front of them.’ Before the Apple I, no computer had come with a keyboard or screen after the Apple I, he says proudly, no computer would come without them.

Although an engineering prodigy – ‘engineering, teaching and humour are my things: maybe I should have taken a psychology degree?’ – Woz was an unlikely entrepreneur. Having taken time out of college to earn enough to pay for his final year, he had landed a job designing calculators at Hewlett-Packard, which he had decided was the best job in the world. ‘I just wanted to be an engineer.’ Building devices on the side was fun – over the next year Jobs and he sold 175 Apple Is (priced at the typical Woz figure of $666.66 until he realised the satanic connotations) – ‘but I never wanted to leave Hewlett-Packard,’ Wozniak says. It was only when Jobs, convinced of his partner’s ability to design a computer that would change the world, orchestrated a campaign to convince him, that he agreed to leave HP and join Apple full-time – and then only as long as he could remain an engineer rather than a manager.

Jobs was right, and Woz’s almost single-handedly designed Apple II did change history. ‘It had tons of firsts: it was constantly being optimised,’ Woz says – and it did it in the most elegant, simple and powerful way, which, he adds quickly, is his recipe for life as well as engineering excellence. Ironically, given his subsequent financial career, his creation also bailed out the infant Apple for the next few years through the disasters of the Apple III and the Lisa, which lost money, and kept it going till the Macintosh kicked in 1984.

Woz left full-time employment at Apple in 1985, although his mainstream influence had been on the wane since 1981, when he crashed his light aircraft and temporarily wiped out his memory before returning to college to finish his degree. Since then, his career has been so far removed from the hustling Silicon Valley stereotype that he would qualify as an anti-Mammon. At Apple’s flotation in 1980, Woz had already caused amazement, not least to Jobs, by selling tranches of his shares to 40 ordinary Apple employees (the ‘Woz Plan’) for $5, and giving more away to others left out of the allocation. He bought a cinema, set up philanthropic organisations and dropped $25m, although that was not part of the plan, on two rock festivals (he plans another next year). He taught full-time for eight years, and his latest venture, a GPS-system start-up called Wheels of Zeus (look at the initials) closed down this year. Once described as ‘uniquely undriven’, Wozniak himself admits that he doesn’t ‘feel attached to my money in normal ways’. Of the $200m or so that he made from the Apple IPO, one of the biggest ever at that time, he says on his website: ‘My ideals led me to give most of it away and not that much remains.’

All of which may explain his return to the corporate fray at the shell company Acquicor. Doing engineering at the old pitch of intensity to create a unique product such as the Apple II would in any case be impossible these days, he says, both because industry conditions have changed and ‘because it is hard on the head’. Intriguingly, the new venture brings him together with two old Apple colleagues – Gil Amelio, CEO until he was pushed out in a bitter row after Jobs returned to Apple in 1996, and Ellen Hancock, also a Jobs casualty. Doesn’t this pose problems, given that Woz remains good friends with Jobs, whose temper is legendary? ‘I don’t have anything against someone because someone else I know is in a feud with them,’ he says. ‘I’m one of the rare people who can be friends with lots of parties who are in feuds.’ Woz believes Amelio had overlooked strengths, including an ability to instil financial discipline. ‘He put Apple back on a sound financial footing.’

Woz remains an Apple shareholder (he still draws the minimum salary as employee No 1), and uses the word ‘we’ about the company. He still thinks it serves customers better than anyone else. But that doesn’t stop him criticising the OS X operating system and looking forward to the day when computer applications reside on the web and consumers are released from the regular upgrade tyranny. He is out of sympathy with an industry that has lost the human faith – and humour – it had 25 years ago.

‘I really just wanted recognition as the person who could connect chips better and more elegantly than anyone else in the world,’ he told an audience at Oxford’s Said Business School last week. They gave him a standing ovation.

THE CV

Name Stephen Gary Wozniak

Born 1950, San Jose, California

Education University of Colorado, University of California at Berkeley (electrical, engineering and computer sciences)

Career 1976 left Hewlett-Packard to co-found Apple Computer with Steve Jobs, helped shape computer industry with development of Apple I and II 1985, left Apple to take up teaching and philanthropy 2006, joined shell company Acquicor

Family Married three times, three grown-up children

The Observer, 29 October 2006