Z4 (computer)

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Zuse-Z4-Totale deutsches-museum.jpg
Z4 on display at the Deutsches Museum, Munich
DeveloperKonrad Zuse
ManufacturerZuse Apparatebau
TypeProgrammable, fully automatic digital electromechanical computer
Release date1945; 78 years ago (1945)
Introductory priceSFr 30,000 for five years
Units sold1 (to ETH Zurich)
CPU@ (about) 40 Hz
MemoryMechanical, 32 bits word length
DisplayDecimal floating point numbers, punch tape or Mercedes typewriter
InputDecimal floating point numbers, punch tape
Power(about) 4 kW
MassCa. 1,000 kg (2,200 lb)

The Z4 was arguably the world's first commercial digital computer. It was designed, and manufactured by early computer scientist Konrad Zuse's company Zuse Apparatebau, for an order placed by Henschel & Son, in 1942; though only partially assembled in Berlin, then completed in Göttingen,[1] and not delivered by the defeat of Nazi Germany, in 1945.[2][3][4] The Z4 was Zuse's final target for the Z3 design.[5] Like the earlier Z2, it comprised a combination of mechanical memory and electromechanical logic, so was not a true electronic computer.[6]


Electromagnetic relay of the Z4

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. The Program Construction Unit (Planfertigungsteil) punched the program tapes, making 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[7] 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.)[8][9]

In 1944, Zuse was working on the Z4 with around two dozen people,[10] including Wilfried de Beauclair. 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 (Kommanditgesellschaft, i.e. a limited partnership) and planned to manufacture 300 computers.[11] This way he could also request additional staff and scientists as a contractor in the Emergency Fighter Program.[11] Zuse's company also cooperated with Alwin Walther's Institute for Applied Mathematics at the Technical University of Darmstadt.[12]

To prevent it from falling into the hands of the Soviets, the Z4 was evacuated from Berlin in February 1945 and transported to Göttingen.[10][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,[1] 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.[1][14]

By 1947 it was possible for constants to be entered by the punched tape.[9]

Use 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 as a test, Zuse 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.[15] It was delivered to ETH Zurich in 1950.[16][17]

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

—Konrad Zuse

In 1954, Wolfgang Haack tried to obtain the Z4 for the Technical University of Berlin,[11] 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 Germany, 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[18]). 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.[19]

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


  • Frequency: (about) 40 Hz
  • 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[6] (64 words, 32 bit)[20]
  • Power consumption: (about) 4 kW

See also[edit]


  1. ^ a b c Schillo, Michael [at Wikidata] (2001). "Zuse" (PDF) (Lecture) (in German). Archived (PDF) from the original on 2021-03-08. Retrieved 2010-06-21. (25 pages)
  2. ^ Zuse, Horst. "The Life and Work of Konrad Zuse". Part 6: part6a, part6b. Archived from the original on 2008-06-16. Retrieved 2010-05-15.
  3. ^ Kaisler, Stephen H. (2016-12-12). Birthing the Computer: From Relays to Vacuum Tubes. Cambridge Scholars Publishing. p. 14. ISBN 978-1-44389631-3.
  4. ^ Sommaruga, Giovanni; Strahm, Thomas (2016-01-21). Turing's Revolution: The Impact of His Ideas about Computability. Birkhäuser. p. 54. ISBN 978-3-31922156-4.
  5. ^ Rojas, Raúl (Spring 2006) [2005-05-12]. "The Zuse Computers". Resurrection: The Bulletin of the Computer Conservation Society (edited transscript of speech). Vol. 37. Computing Before Computers seminar, Science Museum. ISSN 0958-7403. Archived from the original on 2022-04-07. Retrieved 2008-07-26.
  6. ^ a b Zuse, Konrad (1993-09-28). The Computer - My Life. Springer Science & Business Media. p. 81. ISBN 978-3-54056453-9. (NB. This is a translation of the original title in German Der Computer - Mein Lebenswerk.)
  7. ^ Rojas, Raúl (2014-02-01). "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. S2CID 1086397.
  8. ^ Speiser, Ambros Paul (2002). "Konrad Zuse's Z4: Architecture, Programming and Modifications at ETH Zurich". In Rojas, Rául; Hashagen, Ulf [in German] (eds.). The first Computers: History and Architectures. MIT. pp. 263–276. ISBN 978-0-262-18197-6.
  9. ^ a b Lyndon, Roger Conant (1947). "The Zuse computer". Mathematics of Computation. 2 (20): 355–359 [359]. doi:10.1090/S0025-5718-1947-0022444-9. ISSN 0025-5718.
  10. ^ a b Bauer, Friedrich Ludwig (2009). Historische Notizen zur Informatik (in German). Berlin, Germany: Springer. p. 198. ISBN 978-3-540-85789-1.
  11. ^ a b c Petzold, Hartmut [in German] (2004). Hellige, Hans Dieter (ed.). Geschichten der Informatik. Visionen, Paradigmen, Leitmotive (in German). Berlin, Germany: Springer. pp. 93, 110. ISBN 3-540-00217-0.
  12. ^ de Beauclair, Wilfried (October 1986). "Alwin Walther, IPM, and the Development of Calculator/Computer Technology in Germany, 1930–1945". Annals of the History of Computing. Institute of Electrical and Electronics Engineers. 8 (4): 334–350. doi:10.1109/MAHC.1986.10061. ISSN 0164-1239. S2CID 15020276.
  13. ^ Zuse, Horst (2010-11-18), Speech, Computer Conservation Society, Science Museum (London), London, UK
  14. ^ Campbell-Kelly, Martin (1995-12-21). "Obituary: Konrad Zuse". The Independent. Retrieved 2011-02-04.
  15. ^ Lippe, Wolfram M. (2010-04-13) [2007]. "Kapitel 14 - Die ersten programmierbaren Rechner" (PDF) (in German). Archived from the original (PDF) on 2011-07-19. Retrieved 2010-06-21.
  16. ^ "Zuse Computer Model IV, at Zurich, Switzerland". Digital Computer Newsletter. 3 (1): 5. April 1951.[dead link]
  17. ^ "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.
  18. ^ "Description of the BINAC". Retrieved 2008-07-26. Citing Schmitt, William F. (1988). "The UNIVAC SHORT CODE". IEEE Annals of the History of Computing. 10 (1): 7–18 [9]. doi:10.1109/MAHC.1988.10004. S2CID 10189359. The BINAC
  19. ^ Deutsches Museum, Die Z3 und Z4 von Konrad Zuse, Website of the Deutsches Museum
  20. ^ A survey of automatic digital computers. Office of Naval Research, Dept. of the Navy. 1953. p. 97.

Further reading[edit]

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