Z4 (computer)

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Z4 on display at the Deutsches Museum, Munich

The Z4 was the world's first commercial digital computer, designed by German engineer Konrad Zuse and built by his company Zuse Apparatebau in 1945.[1][2][3] The Z4 was Zuse's final target for the Z3 design,[4] but like Z2 it was partly mechanical (memory) and electromechanical machine.[5]


The Z4 was very similar to the Z3 in its design but was significantly enhanced in a number of respects. The memory consisted of 32-bit rather than 22-bit floating point words. A special unit called the Planfertigungsteil (program construction unit), which punched the program tapes, made programming and correcting programs for the machine much easier by the use of symbolic operations and memory cells. Numbers were entered and output as decimal floating point even though the internal working was in binary. The machine had a large repertoire of instructions including square root, MAX, MIN and sine. Conditional tests included tests for infinity. When delivered to ETH Zurich in 1950 the machine had a conditional branch facility added[6] and could print on a Mercedes typewriter. There were two program tapes where the second could be used to hold a subroutine. (Originally six were planned.)[7][8]

In 1944, Zuse was working on the Z4 with around two dozen people.[9] Some engineers who worked at the telecommunications facility of the OKW also worked for Zuse as a secondary occupation. Also in 1944 Zuse transformed his company to the Zuse KG, i.e. a limited partnership (in German KG resp. Kommanditgesellschaft) and planned to manufacture 300 computers.[10] This way he could also request additional staff and scientists as a contractor in the Emergency Fighter Program.[11]

To prevent it from falling into the hands of the Soviets, the Z4 was evacuated from Berlin in February 1945 and transported to Göttingen.[12][13] The Z4 was completed in Göttingen in a facility of the Aerodynamische Versuchsanstalt (AVA, Aerodynamic Research Institute), which was headed by Albert Betz. But when it was presented to scientists of the AVA the roar of the approaching front could already be heard,[14] so the computer was transported with a truck of the Wehrmacht to Hinterstein in Bad Hindelang in southern Bavaria, where Konrad Zuse met Wernher von Braun.[14][15]

By 1947 it was made possible for constants to be entered by the punched tape.[8]

Usage after World War II[edit]

In 1949, the Swiss mathematician Eduard Stiefel, after coming back from a stay in the US where he inspected American computers, visited Zuse and the Z4. When he formulated a differential equation for Zuse, who immediately programmed the Z4 to solve it, Stiefel decided to acquire the computer for his newly founded Institute for Applied Mathematics at the ETH Zurich.[16] It was delivered to ETH Zurich in 1950.[17][18]

At least Zürich has an interesting nightlife with the rattling of the Z4, even if it is only modest.

—Konrad Zuse

In 1954 Prof. Wolfgang Haack tried to obtain the Z4 for the Technical University of Berlin,[19] but it was instead transferred to the Institut Franco-Allemand des Recherches de St. Louis (ISL, Franco-German Institute of Research) in France, where it was in use until 1959, under its technical head Hubert Schardin. Today, the Z4 is on display in the Deutsches Museum in Munich. The Z4 inspired the ETH to build its own computer (mainly by Ambros Speiser and Eduard Stiefel), which was called ERMETH, an acronym for German: Elektronische Rechenmaschine ETH ("Electronic Computing Machine ETH").

In 1950/1951, the Z4 was the only working digital computer in continental Europe[clarification needed](cf. BARK) (the British had several, probably as many as eleven),[clarification needed] and the second digital computer in the world to be sold, beating the Ferranti Mark 1 by five months and the UNIVAC I by ten months, but in turn being beaten by the BINAC (although that never worked at the customer's site[20]). Other computers, all numbered with a leading Z, were built by Zuse and his company. Notable are the Z11, which was sold to the optics industry and to universities, and the Z22.

In 1955 the Z4 was sold to the French-German Research Institute of Saint-Louis (Institut franco-allemand de recherches de Saint-Louis) in Saint-Louis, close to Basel, and in 1960 transferred to the German Museum in Munich.[21]

The Z4 was used for calculations for work on the Grande Dixence Dam.


  • Frequency: (about) 40 hertz
  • Average calculation speed: 400 ms for an addition, 3 seconds for a multiplication. Approximately 1000 floating point arithmetic operations on average an hour.
  • Programming: holes in 35 mm film stock, punched on a programming machine
  • Input: Decimal floating point numbers, punch tape
  • Output: Decimal floating point numbers, punch tape or Mercedes typewriter
  • Word length: 32 bits floating point
  • Elements: (about) 2,500 relays, 21 step-wise relays
  • Memory: Mechanical memory from the Z1 and Z2[5] (64 words, 32 bit)[22]
  • Power consumption: (about) 4 kW

See also[edit]


  • Lyndon, Roger C. (1947). "The Zuse computer". Mathematics of Computation. 2 (20): 355–359. doi:10.1090/S0025-5718-1947-0022444-9. ISSN 0025-5718. Report on Z4.[23]
  1. ^ Zuse, Horst. "The Life and Work of Konrad Zuse". Part 6: part6a, part6b. Archived from the original on 16 June 2008. Retrieved 15 May 2010. Cite uses deprecated parameter |deadurl= (help)
  2. ^ Kaisler, Stephen H. (12 December 2016). Birthing the Computer: From Relays to Vacuum Tubes. Cambridge Scholars Publishing. p. 14. ISBN 9781443896313.
  3. ^ Sommaruga, Giovanni; Strahm, Thomas (21 January 2016). Turing's Revolution: The Impact of His Ideas about Computability. Birkhäuser. p. 54. ISBN 9783319221564.
  4. ^ Rojas, Raúl (Spring 2006). "The Zuse Computers". Resurrection: the Bulletin of the Computer Conservation Society. 37. ISSN 0958-7403. Retrieved 26 July 2008.
  5. ^ a b Zuse, Konrad (28 September 1993). The Computer - My Life. Springer Science & Business Media. p. 81. ISBN 9783540564539.
  6. ^ Rojas, Raúl (1 February 2014). Google translation, pdf is also translatable. "Konrad Zuse und der bedingte Sprung" [Konrad Zuse and the conditional jump]. Informatik-Spektrum (in German). 37 (1): 50–53. doi:10.1007/s00287-013-0717-9. ISSN 0170-6012.
  7. ^ Speiser, Ambros P (2002). "Konrad Zuse's Z4: Architecture, Programming and Modifications at ETH Zurich". In Rojas, Rául; Hashagen, Ulf (eds.). The first Computers: History and Architectures. MIT. pp. 263–276. ISBN 978-0-262-18197-6.
  8. ^ a b Lyndon 1947, p. 359.
  9. ^ Bauer, Friedrich L., Historische Notizen zur Informatik. Springer, Berlin 2009, ISBN 3-540-85789-3, Page 198
  10. ^ Hans Dieter Hellige (ed.): Geschichten der Informatik. Visionen, Paradigmen, Leitmotive. Berlin, Springer 2004, ISBN 3-540-00217-0. p. 93.
  11. ^ Hartmut Petzold in: Hans Dieter Hellige (ed.): Geschichten der Informatik. Visionen, Paradigmen, Leitmotive. Berlin, Springer 2004, ISBN 3-540-00217-0. p. 93.
  12. ^ Bauer, Friedrich L., Historische Notizen zur Informatik. Springer, Berlin 2009, ISBN 3-540-85789-3
  13. ^ Talk given by Horst Zuse to the Computer Conservation Society at the Science Museum (London) on 18 November 2010
  14. ^ a b Schillo, Dr. Michael. "Lecture on Zuse and his machines" (PDF) (in German). Retrieved 21 June 2010.
  15. ^ Campbell-Kelly, Martin (21 December 1995). "Obituary: Konrad Zuse". The Independent (newspaper). Retrieved 4 February 2011.
  16. ^ Lippe, Prof. Dr. Wolfram. "Kapitel 14 - Die ersten programmierbaren Rechner (i.e. The first programmable computers)" (PDF). Archived from the original (PDF) on 19 July 2011. Retrieved 21 June 2010. Cite uses deprecated parameter |deadurl= (help)
  17. ^ "Zuse Computer Model IV, at Zurich, Switzerland". Digital Computer Newsletter. 3 (1): 5. April 1951.
  18. ^ "Automatic Computing Machinery: News - Institute for Applied Mathematics of the Swiss Federal Institute of Technology". Mathematics of Computation. 5 (33): 45–46. 1951. doi:10.1090/S0025-5718-51-99443-4. ISSN 0025-5718.
  19. ^ Hans Dieter Hellige (ed.): Geschichten der Informatik. Visionen, Paradigmen, Leitmotive. Berlin, Springer 2004, ISBN 3-540-00217-0. p. 110.
  20. ^ "Description of the BINAC". citing Annals of the History of Computing, Vol. 10 #1 1988. Retrieved 26 July 2008.
  21. ^ Deutsches Museum, Die Z3 und Z4 von Konrad Zuse, Website of the Deutsches Museum
  22. ^ Research, United States Office of Naval (1953). A survey of automatic digital computers. Office of Naval Research, Dept. of the Navy. p. 97.
  23. ^ Randell, B. (6 December 2012). The Origins of Digital Computers: Selected Papers. Springer Science & Business Media. pp. 156–157. ISBN 9783642962424.

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