Steve Jobs has resigned as CEO of Apple, with CCO Tim Cook taking over the running of the company.It's a surprise, but at the same time, not really much of a surprise. Steve Jobs is 56-years-old and has undergone a liver transplant after suffering from pancreatic cancer. He's also been on medical leave since 17 January. With all that in mind, the day-to-day running of a corporate and technological giant perhaps isn't for him right now. He's not gone completely though, with Jobs taking on the less hands-on role of chairman.According to the BBC, Jobs has written a short letter to the board, which said: 'I have always said if there ever came a day when I could no longer meet my duties and expectations as Apple's chief executive, I would be the first to let you know. Unfortunately, that day has come. I hereby resign as chief executive of Apple.''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. I have made some of the best friends of my life at Apple, and I thank you all for the many years of being able to work alongside you.'The decision is unlikely to impact in the day-to-day running of Apple. Commenting on the news, Michael Gartenberg from Gartner told the BBC: 'At the end of the day, consumers don't buy products from Apple because they're from Steve Jobs, they buy them because they meet their needs and they're good products, and they'll continue to do that.'But the markets are a little more sensitive to the news, perhaps recognising the value of Jobs as a creative force. Apple shares slid more than 5% in after-hours trading, while rivals in the mobile market picked up considerably. HTC rose 4.1%, while Samsung gained 3.2% for example.All that could change in September though, when Apple is expected to launch the iPhone 5, as well as an iPhone 4s, the latter said to be an attempt by Apple to widen the market for its smartphones, particularly in emerging markets. A successful launch event and those shares will start to climb once more.