Gaunt and Frail, Cancer Battle Takes Its Toll on Steve Jobs

Though his resignation letter was short and to the point, it was obviously full of emotion as he thanked 'the best friends he made for life' at the billion dollar company.

He is seen as the heart and soul of Apple, with analysts and investors repeatedly expressing concern over how the company, based in Cupertino, California, would handle his departure.

He has now been replaced by former Chief Operating Officer Tim Cook.

Cook ran Apple when Jobs went on medical leave and has taken over day-to-day operations since early this year, with the company racking up record revenue and profit.

He was previously responsible for Apple's worldwide sales and operations, including management of the supply chain, sales activities, and service and support in all markets and countries, according to ABC.

He has been at the company since 1998 and was recently given a $5million bonus as well as 75,000 restricted stock units as a thank you for his 'outstanding performance'.

Apple officially became the most valuable company in America this month and is now worth $338billion, $1billion more than Exxon Mobil. Pancreatic cancers are generally some of the most lethal of all tumours, and the most common type often kills within six months.

Jobs has battled a less common variety that grows far more slowly and develops in the hormone-secreting section of the pancreas, according to USA Today. Although diagnosed in 2003, his illness was not disclosed until the following year, after he'd had surgery.

The fiercely private CEO has said relatively little about his health problems, although he did acknowledge his bout with cancer during a commencement speech at Stanford University, saying: 'No one wants to die. And yet death is the destination we all share. No one has ever escaped it.'