The Z3 was an electromechanical computer designed by Konrad Zuse. It was the world's first working programmable, fully automatic computing machine. It was Turing-complete, and by modern standards the Z3 was one of the first machines that could be considered a complete computing machine, although it lacked the conditional branch operation. The Z3 was built with 2,000 relays, implementing a 22 bit word length that operated at a clock frequency of about 5–10 Hz. Program code and data were stored on punched film.
The Z3 was completed in Berlin in 1941. The German Aircraft Research Institute used it to perform statistical analyses of wing flutter.
The original Z3 was destroyed in 1943 during an Allied bombardment of Berlin. A fully functioning replica was built in the 1960s by Zuse's company, Zuse KG, and is on permanent display in the Deutsches Museum.
Zuse asked the German government for funding to replace the relays with fully electronic switches, but funding was denied during World War II as "not war-important". 
Design and development
Zuse designed the Z1 in 1935 to 1936 and built it from 1936 to 1938. The Z1 was wholly mechanical and only worked for a few minutes at a time at most. Helmut Schreyer advised Zuse to use a different technology. As a doctoral student at the Berlin Institute of Technology in 1937 he worked on the implementation of Boolean operations and (in today's terminology) flip-flops on the basis of vacuum tubes (valves). In 1938 Schreyer demonstrated a circuit on this basis to a small audience and explained his vision of an electronic computing machine – but since the largest operational electronic devices contained many fewer tubes this was considered practically unfeasible.
So Zuse decided to implement the next design based on relays. The realization of the Z2 was helped financially by Dr. Kurt Pennke, who manufactured small calculating machines. The Z2 was completed in 1939 and presented to an audience of the Deutsche Versuchsanstalt für Luftfahrt ("German Laboratory for Aviation") in 1940 in Berlin-Adlershof. Zuse was lucky – this presentation was one of the few instances where the Z2 actually worked and could convince the DVL to partly finance the next design.
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