Editing Z3 (computer) (section)

== Design and development ==
[[File:Elektromagnetischerspeicher zuse relais.jpg|thumb|Electromagnetic memory (relays) included in the Z3, [[Z5 (computer)|Z5]] and [[Z11 (computer)|Z11]]]]
Zuse designed the [[Z1 (computer)|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 [[Technische Hochschule]] in Charlottenburg (now [[Technische Universität Berlin]]) in 1937 he worked on the implementation of Boolean operations and (in today's terminology) [[flip-flop (electronics)|flip-flops]] on the basis of [[vacuum tube]]s. 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 far fewer tubes this was considered practically infeasible.<ref name="Lippe_2007"/> In that year when presenting the plan for a computer with 2,000 electron tubes, Zuse and Schreyer, who was an assistant at {{ill|Wilhelm Stäblein|lt=Wilhelm Stäblein's|de}} Telecommunication Institute at [[Technische Universität Berlin]], were discouraged by members of the institute who knew about the problems with electron tube technology.<ref name="Hellige_2004"/>{{rp|pages=113, 152}} Zuse later recalled: "They smiled at us in 1939, when we wanted to build electronic machines ... We said: The electronic machine is great, but first the [[Electronic component|components]] have to be developed."<ref name="Hellige_2004"/>{{rp|page=102}} In 1940, Zuse and Schreyer managed to arrange a meeting at the [[Oberkommando der Wehrmacht]] (OKW) to discuss a potential project for developing an electronic computer, but when they estimated a duration of two or three years, the proposal was rejected.<ref name="Hellige_2004"/>{{rp|page=115}}

Zuse decided to implement the next design based on relays. The realization of the [[Z2 (computer)|Z2]] was helped financially by [[Kurt Pannke]], who manufactured small calculating machines. The Z2 was completed and presented to an audience of the {{lang|de|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.<ref name="Lippe_2007"/>

In 1941, improving on the basic Z2 machine, he built the Z3 in a highly secret project of the German government.<ref name="Parsons-Oja_2007"/> [[Joseph Jennissen]] (1905–1977),<ref name="Kauther-Wirtz_2013"/> member of the "Research-Leadership" (''Forschungsführung'') in the [[Air Ministry (Germany)|Reich Air Ministry]]<ref name="Maier_2007"/> acted as a government supervisor for orders of the ministry to Zuse's company ''ZUSE Apparatebau''.<ref name="ZIB_Chrono"/> A further intermediary between Zuse and the Reich Air Ministry was the aerodynamicist [[Herbert A. Wagner]].<ref name="Bruderer"/>

[[File: Zuse archive Z3.jpg|thumb|Drawing of the Z3 computer from Zuse's 1941 patent.]]
The Z3 was completed in 1941 and was faster and far more reliable than the Z1 and Z2. The Z3 [[floating-point arithmetic]] was improved over that of the Z1 in that it implemented exception handling "using just a few relays", the exceptional values (plus infinity, minus infinity and undefined) could be generated and passed through operations. It further added a square root instruction. 

The Z3, like its predecessors, stored its program on an external punched tape, thus no rewiring was necessary to change programs. However, it did not have conditional branching found in later universal computers.<ref name="Rojas_1997_Legacy"/>{{rp|page=7}}

On 12 May 1941, the Z3 was presented to an audience of scientists including the professors Alfred Teichmann and Curt Schmieden<ref name="DHM_2013"/> of the {{lang|de|Deutsche Versuchsanstalt für Luftfahrt}} ("German Laboratory for Aviation") in [[Berlin]],<ref name="parTU_2009"/> today known as the [[German Aerospace Center]] in [[Cologne]].<ref name="DLR"/>

Zuse moved on to the [[Z4 (computer)|Z4]] design, which he completed in a bunker in the [[Harz]] mountains, alongside [[Wernher von Braun]]'s ballistic missile development. When World War II ended, Zuse retreated to [[Hinterstein]] in the Alps with the Z4, where he remained for several years.<ref name="Campbell-Kelly_1995"/>