The Z3 was a German electromechanical computer designed by Konrad Zuse in 1935 and completed with the help of Helmut Schreyer in Berlin in 1941. It was the world's first working, programmable, fully automatic digital computer. The Z3 was built with 2,600 relays that implemented a 22-bit word length and operated at a clock frequency of about 5-10 Hz. The program code was stored on punched film and initial values were entered manually. The device was not considered to be mandatory and was therefore never put into everyday use. Based on the work of Hans Georg Küssner (cf. Küssner effect), for example, a "program for the calculation of a complex matrix" was written and used to solve wing flutter problems.
The Deutsche Versuchsanstalt für Luftfahrt had looked at the Z2 and given Zuse 25,000 Reichsmarks to build the Z3. Zuse asked the German government for funding to replace the relays with all-electronic switches, but funding was denied during World War II because such development was considered "not important to the war effort." On May 12, 1941 the Z3 was finally presented to a group of scientists (including Alfred Teichmann and Curt Schmieden). When Zuse was briefly drafted into the war in 1941 , he wrote to a friend: "Others leave the family behind, I leave the Z3". (Konrad Zuse: Famous Alumni of the Technical University of Berlin).
The original Z3 was destroyed in an Allied bombing raid on Berlin on December 21, 1943. This was a tragic moment for Zuse, as he no longer had proof that there really had been a working Z3. A working replica, made 1962 by Zuse-KG for exhibition purposes, is in the Deutsches Museum in Munich. At its former location, on the ruins of the house in Methfesselstraße in Berlin's Kreuzberg district, a plaque commemorates Zuse's Wirkungsstätte. Since the 100th birthday of Konrad Zuse on June 22, 2010, a replica of the Z3 can also be seen in the Konrad Zuse Museum in Hünfeld.
The Z3 was originally called the V3 (Versuchsmodell 3 or Experimentalmodell 3), but was renamed so as not to confuse it with the German V-Waffen. A fully functional replica was built in 1961 by Zuse's company, Zuse KG, and is now on permanent display at the Deutsches Museum in Munich . The Z3 was demonstrated in 1998 as a Turing-complete in principle. However, due to the lack of conditional branches, the Z3 satisfies this definition only by speculatively computing all possible results of a computation. Thanks to this machine and its predecessors, Konrad Zuse has often been called the inventor of the computer.