Considered the first electromechanical computers, they were created by Konrad Zuse in 1938. He began construction of the Z1 in 1936, setting out to make a computing machine with faster, more extensive calculating power than the existing desk calculators. Deciding on a binary system for greater calculating speed, he set the standard for it’s use in computing. The Z1 expressed the numbers using mechanical gates opened and closed by sliding plates. It was powered by electricity, and he intended to replace the gears and axles of desk calculators.
The Z1 read instructions from strips of film punched with binary, and functioned moderately but had trouble routing electrical signals from one location to another within itself. It’s significance was that it was the first freely programmable, binary based machine in the world. Zuse solved this problem in the Z2 by using an electromagnetic system that replaced the mechanical plates. He discovers this method is an excellent way to express binary numbers. Still not an impressive machine, it has potential and convinces the German Experimental Dynamics Institute to further fund Zuse’s projects. Later Zuse fled Germany with his machines, and the Z4 was born. It is the first working freely programmable, fully automatic machine. It was built with relays, and had a clock frequency of 5.33 Hz. The Harvard Mark I was considered the first until the discovery of the Z4 after the war.
In the last days of WWII the Z4 was transported under adventurous circumstances via truck and horse-drawn cart from Berlin to the Allgäu. Hidden in a stable, it remained undiscovered until 1949.