One of my heros is Alan Turing.
Turing played an important role in the deciphering of the German Enigma codes during WWII, and as a result saved the lives of many people directly involved in the prosecution of the war.
He was a mathemetician who played an important role in the development of computers.
One of his seminal ideas was of the Turing Machine, that demonstrated the theoretical possibility of stored program computing.
The video below shows a modern implementation of the Turing Machine.