Mechanical computer

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Hamann Manus R

A mechanical computer is built from mechanical components such as levers and gears, rather than electronic components. The most common examples are adding machines and mechanical counters, which use the turning of gears to increment output displays. More complex examples could carry out multiplication and division—Friden used a moving head which paused at each column—and even differential analysis. One model[which?] sold in the 1960s calculated square roots.

Mechanical computers can be either analog, using smooth mechanisms such as curved plates or slide rules for computations; or digital, which use gears.

Mechanical computers reached their zenith during World War II, when they formed the basis of complex bombsights including the Norden, as well as the similar devices for ship computations such as the US Torpedo Data Computer or British Admiralty Fire Control Table. Noteworthy are mechanical flight instruments for early spacecraft, which provided their computed output not in the form of digits, but through the displacements of indicator surfaces. From Yuri Gagarin's first manned spaceflight until 2002, every manned Soviet and Russian spacecraft Vostok, Voskhod and Soyuz was equipped with a Globus instrument showing the apparent movement of the Earth under the spacecraft through the displacement of a miniature terrestrial globe, plus latitude and longitude indicators.

Mechanical computers continued to be used into the 1960s, but were quickly replaced by electronic calculators, which—with cathode-ray tube output—emerged in the mid-1960s. The evolution culminated in the 1970s with the introduction of inexpensive handheld electronic calculators. Mechanical computers were ailing in the 1970s and dead by the 1980s.

In 2016, NASA announced that its Automaton Rover for Extreme Environments program would use a mechanical computer to operate in the harsh environmental conditions found on Venus.[1]


Electro-mechanical computers[edit]

Early electrically powered computers constructed from switches and relay logic rather than vacuum tubes (thermionic valves) or transistors (from which later electronic computers were constructed) are classified as electro-mechanical computers. These varied greatly in design and capabilities, with some later units capable of floating point arithmetic. Some relay-based computers remained in service after the development of vacuum-tube computers, where their slower speed was compensated for by good reliability; some models were built as duplicate processors to detect errors, or could detect errors and retry the instruction. A few models were sold commercially with multiple units produced, but many designs were experimental one-off productions.

Name Country Year Remarks Reference
Automatic Relay Computer UK 1947 The Booths, experimental [2]
ARRA Holland 1952 experimental
BARK Sweden 1952 experimental
FACOM-100 Japan 1954 Fujitsu commercial [3]
FACOM-128 Japan 1956 commercial [4]
Harwell computer UK 1951 later known as WITCH
Harvard Mark I USA 1944 (IBM Automatic Sequence Controlled Calculator)
Harvard Mark II USA 1947
Imperial College Computing Engine (ICCE) UK 1947
Office of Naval Research ONR Relay Computer US 1951 Drum storage, but relay ALU, formerly Navy cryptology computer ABEL [5] [6]
OPREMA East Germany 1955 Commercial use at Zeiss Optical in Jena [7]
RVM-1 Soviet Union 1957 Alexander Kronrod [8]
SAPO Czechoslovakia 1957
Simon USA 1950 Hobbyist logic demonstrator magazine article
Z2 Germany 1939 Konrad Zuse
Z3 Germany 1941 Zuse
Z4 Germany 1945 Zuse
Z5 Germany 1953 Zuse
Z11 Germany 1955 Zuse, commercial
Bell Labs Model I USA 1939 George Stibitz, "Complex Number Calculator",450 relays and cross bar switches, demonstrated remote access 1940, used till 1948 [9]
Bell Labs Model II USA 1943 "Relay Interpolator", used for wartime work, shut down 1962 [9]
Bell Labs Model III USA 1944 "Ballistic Computer", used till 1949 [9]
Bell Labs Model IV USA 1944 Navy "Mark 22 Error Detector", used till 1961 [9]
Bell Labs Model V USA 1946, 1947 Two units delivered, general purpose, built in trig functions, floating point [9]
Bell Labs Model VI USA 1950 General purpose, [9]
Unnamed Cryptanalysis Multiplier UK 1937 Turing [10][11]
Relay Computer USA 2006 Harry Porter's Relay Computer, demonstrator/hobby, but integrated circuit memory. [12]


  1. ^ Hall, Loura (2016-04-01). "Automaton Rover for Extreme Environments (AREE)". NASA. Retrieved 2017-08-29. 
  2. ^ Herman H. Goldstine, The Computer from Pascal to von Neumann, Princeton University Press, 2008 ISBN 1400820138, page 349
  3. ^ Fujitsu Facom 100, retrieved 2017 Jul 26
  4. ^ FACOM 128A and 128B Relay Computers, retrieved 2017 July 26
  5. ^ David L. Boslaugh When Computers Went to Sea: The Digitization of the United States Navy page 95
  6. ^ The Office of Naval Research Relay Computer, abstract, retrieved 2017 July 25
  7. ^ Dolores L. Augustine, Red Prometheus: Engineering and Dictatorship in East Germany, 1945-1990MIT Press, 2007 ISBN 0262012367, page 134
  8. ^ Relay Computer RVM-1, retrieved 2017 July 25
  9. ^ a b c d e f Jack Belzer, Albert G. Holzman, Allen Kent (ed), Encyclopedia of Computer Science and Technology Volume 3, CRC Press, 1976 ISBN 0824722531 pages 197-200
  10. ^ Teuscher, Christof (2004). Alan Turing: Life and Legacy of a Great Thinker. Springer Science & Business Media. p. 46. ISBN 9783540200208. 
  11. ^ Hodges, Andrew (2014-11-10). Alan Turing: The Enigma: The Book That Inspired the Film "The Imitation Game". Princeton University Press. pp. 175–177. ISBN 9781400865123. 
  12. ^ Harry Porter's Relay Computer retrieved 2017 July 26

See also[edit]