Z3
These computers were the size of a large room and they used as much power as several hundred modern day computers. With this invention he got help from friends and some small support from the government he constructed the Z3 (1939-1941) in Berlin, Kreutzberg. He built the Z3 because he wanted to prove that it was possible to make a reliable, freely programmable computer based on a binary floating point number and switching system, which could be used to calculate very complicated arithmetic calculation. So the Computer was reliable he used relays throughout the whole computer.