EDSAC Simulator

EDSAC was the first stored-memory computer (the more famous ENIAC had to be physically programmed by re-plugging wires). EDSAC, at Cambridge University, ran its first program on May 6, 1949. At this site, you can download a simulator of this ancestor of the computers we use today. Doubtless the simulator is at least several orders of magnitude faster than the original machine.

http://www.dcs.warwick.ac.uk/~edsac/