Z3 (computer)

The Z3 was a German electromechanical computer designed by Konrad Zuse. It was the world's first working programmable, fully automatic digital computer.[1] The Z3 was built with 2,600 relays, implementing a 22-bit word length that operated at a clock frequency of about 4–5 Hz. Program code was stored on punched film. Initial values were entered manually.[2][3][4]

The Z3 was completed in Berlin in 1941 but was not considered vital, so it was never put into everyday operation.[2][3][5][6][7][8] Based on the work of Hans Georg Küssner (cf. Küssner effect) e.g. a "Program to Compute a Complex Matrix" was written and used to solve wing flutter problems.[9] Zuse asked the German government for funding to replace the relays with fully electronic switches, but funding was denied during World War II since such development was deemed "not war-important".[10]:148 The original Z3 was destroyed on 21 December 1943 during an Allied bombardment of Berlin. The Z3 was originally called V3 (Versuchsmodell 3 or Experimental Model 3) but was renamed to not be confused with Germany's V-weapons.[11] A fully functioning replica was built in 1961 by Zuse's company, Zuse KG, and is on permanent display at Deutsches Museum in Munich.[12]

The Z3 was demonstrated in 1998 to be, in principle, Turing-complete.[13] However, because it lacked conditional branching, the Z3 only meets this definition by speculatively computing all possible outcomes of a calculation.

Thanks to this machine and its predecessors, Konrad Zuse is often regarded as the inventor of the computer.[14][15][16][17]

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. 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.[18] In that year when presenting the plan for a computer with 2,000 electron tubes, Zuse and Schreyer, who was an assistant at Prof. Wilhelm Stäblein's Telecommunication Institute at the Technical University of Berlin, were discouraged by members of the institute who knew about the problems with electron tube technology.[19] 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 components have to be developed."[20] 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.[21]

Zuse decided to implement the next design based on relays. The realization of the Z2 was helped financially by Dr. Kurt Pannke, who manufactured small calculating machines. The Z2 was completed 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.[18]

Improving on the basic Z2 machine, he built the Z3 in 1941, which was a highly secret project of the German government.[22] Dr. Joseph Jennissen (1905–1977),[23] member of the "Research-Leadership" (Forschungsführung) in the Reich Air Ministry[24] acted as a government supervisor for orders of the ministry to Zuse's company ZUSE Apparatebau.[25] A further intermediary between Zuse and the Reich Air Ministry was the aerodynamicist Herbert A. Wagner.[26]

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. The Z3 stored its program on an external tape, thus no rewiring was necessary to change programs.[27]

On 12 May 1941 the Z3 was presented to an audience of scientists including the professors Alfred Teichmann and Curt Schmieden[28] of the Deutsche Versuchsanstalt für Luftfahrt ("German Laboratory for Aviation") in Berlin,[29] today known as the German Aerospace Center in Cologne.

Zuse moved on to the Z4 design, which was built just days before World War II ended.

Z3 as a universal Turing machine

It was possible to construct loops on the Z3, but there was no conditional branch instruction. Nevertheless, the Z3 was Turing-complete – how to implement a universal Turing machine on the Z3 was shown in 1998 by Raúl Rojas.[13][30] He proposed that the tape program would have to be long enough to execute every possible path through both sides of every branch. It would compute all possible answers, but the unneeded results would be canceled out (a kind of speculative execution). Rojas concludes, "We can therefore say that, from an abstract theoretical perspective, the computing model of the Z3 is equivalent to the computing model of today's computers. From a practical perspective, and in the way the Z3 was really programmed, it was not equivalent to modern computers."

From a pragmatic point of view, however, the Z3 provided a quite practical instruction set for the typical engineering applications of the 1940s – Zuse was a civil engineer who only started to build his computers to facilitate his work in his main profession.

Relation to other work

The success of Zuse's Z3 is often attributed to its use of the simple binary system.[31] This was invented roughly three centuries earlier by Gottfried Leibniz; Boole later used it to develop his Boolean algebra. Zuse was inspired by Hilbert's and Ackermann's book on elementary mathematical logic (cf. Principles of Mathematical Logic).[19] In 1937, Claude Shannon introduced the idea of mapping Boolean algebra onto electronic relays in a seminal work on digital circuit design. Zuse, however, did not know Shannon's work and developed the groundwork independently[10]:149 for his first computer Z1, which he designed and built from 1935 to 1938.

Zuse's coworker Helmut Schreyer built an electronic digital experimental model of a computer using 100 vacuum tubes[32] in 1942, but it was lost at the end of the war.

An analog computer was built by the rocket scientist Helmut Hölzer in 1942 at the Peenemünde Army Research Center to simulate[33][34][35] V-2 rocket trajectories[36][37].

The Tommy Flowers-built Colossus (1943)[38] and the Atanasoff–Berry Computer (1942) used thermionic valves (vacuum tubes) and binary representation of numbers. Programming was by means of re-plugging patch panels and setting switches.

The ENIAC computer, completed after the war, used vacuum tubes to implement switches and used decimal representation for numbers. Until 1948 programming was, as with Colossus, by patch leads and switches.

The Manchester Baby of 1948 along with the Manchester Mark 1 and EDSAC both of 1949 were the world's earliest working computers that stored program instructions and data in the same space. In this they implemented the stored-program concept which is frequently (but erroneously) attributed to a 1945 paper by John von Neumann and colleagues.[39][40] Von Neumann is said to have given due credit to Alan Turing,[41] and the concept had actually been mentioned earlier by Konrad Zuse himself, in a 1936 patent application (that was rejected).[42][43] Konrad Zuse himself remembered in his memoirs: "During the war it would have barely been possible to build efficient stored program devices anyway."[44] and Friedrich L. Bauer wrote: "His visionary ideas (live programs) which were only to be published years afterwards aimed at the right practical direction but were never implemented by him."[45]


  • Average calculation speed: addition – 0.8 seconds, multiplication – 3 seconds[46]
  • Arithmetic unit: Binary floating-point, 22-bit, add, subtract, multiply, divide, square root[46]
  • Data memory: 64 words with a length of 22 bits[46]
  • Program memory: Punched celluloid tape[46]
  • Input: Decimal floating-point numbers[46]
  • Output: Decimal floating-point numbers[46]
  • Input and Output was facilitated by a terminal, with a special keyboard for input and a row of lamps to show results[18]
  • Elements: Around 2,000 relays (1,400 for the memory)[18]
  • Frequency: 5.3 hertz[46]
  • Power consumption: Around 4,000 watts[46]
  • Weight: Around 1 tonne (2,200 lb)[46]

Modern reconstructions

A modern reconstruction directed by Raúl Rojas and Horst Zuse started in 1997 and finished in 2003. It is now in the Konrad Zuse Museum in Hünfeld, Germany.[47][48] Memory was halved to 32 words. Power consumption is about 400 W, and weight is about 30 kilograms (66 lb).[49]

In 2008 Horst Zuse started reconstruction of Z3 by himself.[50] It was presented in 2010 in the Konrad Zuse Museum in Hünfeld.[51][52]

See also


  1. "A Computer Pioneer Rediscovered, 50 Years On". The New York Times. April 20, 1994. Archived from the original on November 4, 2016.
  2. Weiss, E. (1996). Z1 and Z2. "Konrad Zuse Obituary". IEEE Annals of the History of Computing. 18 (2): 3–4. doi:10.1109/mahc.1996.489747. ISSN 1058-6180.
  3. Borchers, Detlef (2016-05-12). "Vor 75 Jahren: Computer Z3 wird vorgeführt" [75 years ago: Computer Z3 is demonstrated]. heise online (in German). Google translation. Retrieved 2018-05-13.
  4. Ceruzzi 1983, pp. 32–37.
  5. Zuse, Konrad (2013-03-09). The Computer – My Life. Springer Science & Business Media. p. 64. ISBN 9783662029312.
  6. Ceruzzi 1983, pp. 30, 38–39.
  7. It could solve problems like systems of linear equations and their determinants, quadratic equations and Eigenvalues (for wing flutter).
  8. Zuse, Konrad (1987-10-02). "My First Computer and First Thoughts About Data Processing". history.computer.org. Computer Pioneers – Konrad Zuse. Search for 1941; ["Computer Design-Past, Present, Future," talk in Lund/Sweden, Oct. 2, 1987, previously unpublished.] Retrieved 2018-05-14.
  9. Original name of the program in German: "Programm für die Berechnung einer komplexen Matrix". Hans Dieter Hellige (editor): Geschichten der Informatik. Visionen, Paradigmen, Leitmotive. Springer, Berlin 2004, ISBN 3-540-00217-0.
  10. Hans-Willy Hohn (1998). Kognitive Strukturen und Steuerungsprobleme der Forschung. Kernphysik und Informatik im Vergleich (in German). Schriften des Max-Planck-Instituts für Gesellschaftsforschung Köln. ISBN 978-3-593-36102-4.
  11. "Z3 Computer (1938–1941)". www.computermuseum.li. Archived from the original on 2008-06-17.
  12. Ceruzzi, Paul E. (1983). "2. Computers in Germany: Description of the Z3". Reckoners. ed-thelen.org. p. 30. Retrieved 2018-11-03.
  13. Rojas, R. (1998). "How to make Zuse's Z3 a universal computer". IEEE Annals of the History of Computing. 20 (3): 51–54. doi:10.1109/85.707574.
  14. "Konrad Zuse Biography". RTD Net. From various sides Konrad Zuse was awarded with the title "Inventor of the computer".
  15. "Konrad Zuse". The German Way. The Konrad-Zuse-Zentrum für Informationstechnik Berlin (ZIB), founded in 1986, is a working memorial to the German inventor of the computer.
  16. Ulrike von Leszczynski (2010-06-27). "Z like Zuse: German inventor of the computer". Monsters & Critics. Archived from the original on 2013-05-22. he(Zuse) built the world's first computer in Berlin
  17. Mary Bellis (2017-07-31). "Konrad Zuse and the Invention of the Modern Computer". Zuse earned the semi-official title of "inventor of the modern computer" for his series of automatic calculators, which he invented to help him with his lengthy engineering calculations.
  18. Lippe, Prof. Dr. Wolfram. "Kapitel 14 – Die ersten programmierbaren Rechner" [The first programmable computers] (PDF) (in German). Archived from the original (PDF) on 2011-07-19. Retrieved 2010-06-21.
  19. Hans Dieter Hellige, ed. (2004). Geschichten der Informatik. Visionen, Paradigmen, Leitmotive (in German). Berlin: Springer. pp. 113, 152. ISBN 978-3-540-00217-8.
  20. Hans Dieter Hellige, ed. (2004). Geschichten der Informatik. Visionen, Paradigmen, Leitmotive (in German). Berlin: Springer. p. 102. ISBN 3-540-00217-0. Original in German: "Man hat 1939 über uns gelächelt, als wir elektronische Geräte bauen wollten. ... Wir sagten uns damals: Die elektronische Maschine ist wunderbar, aber erst müssen ihre Bauelemente entwickelt werden."
  21. Hans Dieter Hellige, ed. (2004). Geschichten der Informatik. Visionen, Paradigmen, Leitmotive (in German). Berlin: Springer. p. 115. ISBN 3-540-00217-0.
  22. "New perspectives, computer concepts", June Jamrich Parsons, Dan Oja. Cengage Learning, 2007. ISBN 978-1-4239-0610-0, ISBN 978-1-4239-0610-0. Retrieved March 14, 2010.
  23. Alexander Kauther, Paul Wirtz: Der Einzelkämpfer Dorner. Grin Verlag Gmbh, 2013, ISBN 3-656-04860-6
  24. Helmut Maier: Forschung als Waffe, Wallstein Verlag, 2007, ISBN 3-8353-0109-8, p. 847
  25. "1977-compilation by Zuse of people in contact to his computers from 1935 to 1945" (in German). Archived from the original on 2011-09-28.
  26. Herbert Bruderer, ETH Zurich. "Konrad Zuse und die ETH Zürich" (PDF) (in German). Retrieved 2011-10-26.
  27. Rojas, R (1997). "Konrad Zuse's Legacy: The Architecture of the Z1 and Z3" (PDF). IEEE Annals of the History of Computing. 19 (2): 5–15. doi:10.1109/85.586067.
  28. "An einem 12. Mai" (in German). Google translation. Deutsches Historisches Museum (German Historical Museum).CS1 maint: others (link)
  29. "Technische Universität Berlin – Rechenhilfe für Ingenieure" (in German). Google translation. Technical University of Berlin. Archived from the original on 2009-02-13.CS1 maint: others (link)
  30. Rojas, Raúl. "How to Make Zuse's Z3 a Universal Computer" (PDF).
  31. Ceruzzi, Paul (1983). "2. Computers in Germany". Reckoners: The Prehistory of The Digital Computer. Greenwood Press.
  32. "Helmut Schreyer" at the University of Berlin
  33. H. Otto Hirschler, 87, Aided Space Program
  34. Neufeld, Michael J. (2013-09-10). The Rocket and the Reich: Peenemunde and the Coming of the Ballistic Missile Era. Smithsonian Institution. p. 138. ISBN 9781588344663.
  35. Ulmann, Bernd (2013-07-22). Analog Computing. Walter de Gruyter. p. 38. ISBN 9783486755183.
  36. Neufeld, Michael J (1995). The Rocket and the Reich: Peenemünde and the Coming of the Ballistic Missile Era. New York: The Free Press. P. 106
  37. Tomayko, James E. (1985). "Helmut Hoelzer's Fully Electronic Analog Computer". IEEE Annals of the History of Computing. 7 (3): 227–240. doi:10.1109/MAHC.1985.10025.
  38. B. Jack Copeland, ed. (2006). Colossus: The Secrets of Bletchley Park's Codebreaking Computers. Oxford University Press. ISBN 978-0-19-284055-4.
  39. von Neumann, John (1945). "First Draft of a Report on the EDVAC" (PDF). Retrieved March 24, 2014.
  40. "Stored-program concept". Encyclopædia Britannica. Retrieved 24 March 2014.
  41. Copeland, Jack (2000). "A Brief History of Computing: ENIAC and EDVAC". Retrieved 27 January 2010. which cites Randell, Brian (1972). Meltzer, B.; Michie, D. (eds.). On Alan Turing and the Origins of Digital Computers. Machine Intelligence. 7. Edinburgh: Edinburgh University Press. p. 10. ISBN 978-0-902383-26-5.
  42. Williams, F. C.; Kilburn, T. (September 25, 1948). "Electronic Digital Computers". Nature. 162 (4117): 487. doi:10.1038/162487a0. Archived from the original on April 6, 2009. Retrieved 2009-04-10.
  43. Susanne Faber, "Konrad Zuses Bemuehungen um die Patentanmeldung der Z3", 2000
  44. Zuse, Konrad (20 April 2010). Der Computer – Mein Lebenswerk (in German) (5 ed.). Berlin: Springer. p. 78. ISBN 978-3642120954. Während des Krieges wäre es freilich ohnehin kaum möglich gewesen, leistungsfähige Geräte mit Speicherprogrammen zu bauen.
  45. Anmerkungen zum John von Neumann Rechner by Horst Zuse; F.L. Bauer (original): "Seine erst Jahre später publizierten visionären Ideen (Lebendige Rechenpläne) zielten in die richtige praktische Richtung, wurden von ihm aber nie verwirklicht.
  46. Morelli, Marcello (2001). Dalle calcolatrici ai computer degli anni Cinquanta. FrancoAngeli. p. 177. ISBN 9788846428790. Retrieved 5 August 2014.
  47. "Reconstruction of Konrad Zuse's Z3 Computer | Raúl Rojas". dcis.inf.fu-berlin.de.
  48. "Reconstructing the calculating machine Z3". zuse.zib.de.
  49. "Z3-Nachbau-2001" [Z3 replica 2001]. www.horst-zuse.homepage.t-online.de (in German). Google translation.CS1 maint: others (link)
  50. Zuse, Horst (2013), "Reconstruction of Konrad Zuse's Z3", Making the History of Computing Relevant, IFIP Advances in Information and Communication Technology, Springer Berlin Heidelberg, 416, pp. 287–296, doi:10.1007/978-3-642-41650-7_26, ISBN 9783642416491
  51. Zwernemann-Blech, Irene. "Events during Zuse Year 2010". www.horst-zuse.homepage.t-online.de. Retrieved 2018-11-03.
  52. "Z3-Präsentationen" [Z3 – Presentations]. www.horst-zuse.homepage.t-online.de (in German). Google translation. Retrieved 2018-11-03.CS1 maint: others (link)

Further reading

  • B. Jack Copeland, ed. (2006). Colossus: The Secrets of Bletchley Park's Codebreaking Computers. Oxford University Press. ISBN 978-0-19-284055-4.
  • R. Rojas; F. Darius; C. Göktekin & G. Heyne (2005). "The reconstruction of Konrad Zuse's Z3". IEEE Annals of the History of Computing. 27 (3): 23–32. doi:10.1109/mahc.2005.48.
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