In a surprise announcement Wednesday evening, Apple's Board of Directors announced that Steve Jobs is resigning as CEO of the company. Apple's Chief Operating Officer, Tim Cook, has been named Jobs' successor and plans to begin taking over as CEO effective immediately.

"Steve’s extraordinary vision and leadership saved Apple and guided it to its position as the world’s most innovative and valuable technology company," Apple Board member and Genetech chairman Art Levinson said in a statement. "Steve has made countless contributions to Apple’s success, and he has attracted and inspired Apple’s immensely creative employees and world class executive team. In his new role as Chairman of the Board, Steve will continue to serve Apple with his unique insights, creativity and inspiration."

In 2004, Jobs underwent a complicated but successful surgery to remove a tumor in his pancreas, and was back at work within a few months. While the procedure is highly successful for the form of pancreatic cancer that Jobs had, it also removes much of the pancreas and some of the digestive tract. This can lead to further complications, such as the dramatic and visible weight loss Jobs' suffered in 2008.

In 2009, Jobs went on a six-month medical leave again; it was later revealed that Jobs had received a liver transplant. All seemed well after his return until January of 2011 when Jobs announced once again that he was going on medical leave—this time, Apple fans had a feeling he might not be back.

Below is the text of Jobs' letter addressed to the Board and the Apple Community that was distributed on Wednesday evening: