Steve Jobs was 56. He was the Apple Inc. chairman and co-founder who pioneered the personal computer industry and changed the way people think about technology.
From http://www.apple.com/stevejobs/:
Apple has lost a visionary and creative genius, and the world has lost an amazing human being. Those of us who have been fortunate enough to know and work with Steve have lost a dear friend and an inspiring mentor. Steve leaves behind a company that only he could have built, and his spirit will forever be the foundation of Apple.