Apple co-founder Steve Jobs has resigned as chief executive of the technology giant and will be replaced by chief operating officer Tim Cook. Mr Jobs, who underwent a liver transplant following pancreatic cancer, said he could no longer meet his chief executives duties and expectations. The Silicon Valley legend will become chairman of the firm. The 56-year-old has been on medical leave for an undisclosed condition since 17 January. In a short letter to the board of Apple, Mr Jobs wrote: I have always said if there ever came a day when I could no longer meet my duties and expectations as Apples 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 Apples brightest and most innovative days are ahead of it. And I look forward to watching and contributing to its success in a new role. BBC