Z1 (computer)

The Z1 was a mechanical computer designed by Konrad Zuse from 1936 to 1937 and built by him from 1936 to 1938.[1][2] It was a binary electrically driven mechanical calculator with limited programmability, reading instructions from punched celluloid film.

The Z1 was the first freely programmable computer in the world which used Boolean logic and binary floating-point numbers, however it was unreliable in operation.[3][4] It was completed in 1938 and financed completely from private funds. This computer was destroyed in the bombardment of Berlin in December 1943, during World War II, together with all construction plans.

The Z1 was the first in a series of computers that Zuse designed. Its original name was "V1" for VersuchsModell 1 (meaning Experimental Model 1). After WW2, it was renamed "Z1" to differentiate from the flying bombs designed by Robert Lusser.[5] The Z2 and Z3 were follow-ups based on many of the same ideas as the Z1.

Zuse Z1-2
Replica of the Z1 in the German Museum of Technology in Berlin


Zuse Patent 907948
Diagrams from Zuse's May 1936 patent for a binary switching element using a mechanism of flat sliding rods. The Z1 was based on such elements.

The Z1 contained almost all the parts of a modern computer, i.e. control unit, memory, micro sequences, floating-point logic and input–output devices. The Z1 was freely programmable via punched tape and a punched tape reader.[6] There was a clear separation between the punched tape reader, the control unit for supervising the whole machine and the execution of the instructions, the arithmetic unit, and the input and output devices. The input tape unit read perforations in 35-millimeter film.[7]

The Z1 was a 22-bit floating-point value adder and subtracter, with some control logic to make it capable of more complex operations such as multiplication (by repeated additions) and division (by repeated subtractions). The Z1's instruction set had nine instructions and it took between one and twenty cycles per instruction.

The Z1 had a 64-word floating-point memory, where each word of memory could be read from – and written to – the control unit. The mechanical memory units were unique in their design and were patented by Konrad Zuse in 1936. The machine was only capable of executing instructions while reading from the punched tape reader, so the program itself was not loaded in its entirety into internal memory in advance.

The input and output were in decimal numbers, with a decimal exponent and the units had special machinery for converting these to and from binary numbers. The input and output instructions would be read or written as floating-point numbers. The program tape was 35 mm film with the instructions encoded in punched holes.


"Z1 was a machine of about 1000 kg weight, which consisted from some 20000 parts. It was a programmable computer, based on binary floating-point numbers and a binary switching system. It consisted completely of thin metal sheets, which Zuse and his friends produced using a jigsaw."[8] "The [data] input device was a keyboard...The Z1’s programs (Zuse called them Rechenpläne) were stored on punch tapes by means of an 8-bit code"[8]

Construction of the Z1 was privately financed. Zuse got money from his parents, his sister Lieselotte, some students of the fraternity AV Motiv (cf. Helmut Schreyer) and Kurt Pannke (a calculating machines manufacturer in Berlin) to do so.

Zuse constructed the Z1 in his parents' apartment; in fact, he was allowed to use the living room for his construction. In 1936, Zuse quit his job in airplane construction in order to build the Z1.

Zuse is said to have used "thin metal strips" and perhaps "metal cylinders" or glass plates to construct Z1. There were probably no commercial relays in it (although the Z3 is said to have used a few telephone relays). The only electrical unit was an electric motor to give the clock frequency of 1 Hz (cycle per second) to the machine.

'The memory was constructed from thin strips of slotted metal and small pins, and proved faster, smaller, and more reliable, than relays. The Z2 used the mechanical memory of the Z1, but used relay-based arithmetic. The Z3 was experimentally built entirely of relays. The Z4 was the first attempt at a commercial computer, reverting to the faster and more economical mechanical slotted metal strip memory, with relay processing, of the Z2, but the war interrupted the Z4 development.'[9]

The Z1 was never very reliable in operation due to poor synchronization due to internal and external stresses on the mechanical parts.


Zuse Z1
Reconstruction of Z1

The original Z1 was destroyed by the Allied air raids in 1943, but in 1980s Zuse decided to rebuild the machine. First sketches of the Z1 reconstruction were drawn in 1984. He constructed (with the help of two engineering students) thousands of elements of the Z1 again, and finished rebuilding the device in 1989. The rebuilt Z1 (pictured) is displayed at the German Museum of Technology in Berlin.[10][11]


Konrad Zuse: "There is a replica of this Model in the Museum of Traffic and Technology in Berlin. Back then it didn't function well, and in that regard the replica is very reliable -- it also doesn't work well."[12]

See also


  1. ^ Bauer, Friedrich L. (2009-11-05). Origins and Foundations of Computing: In Cooperation with Heinz Nixdorf MuseumsForum. Springer Science & Business Media. p. 78. ISBN 9783642029929.
  2. ^ Zuse, Konrad (1976). The Plankalkül. GMD. p. 21.
  3. ^ Priestley, Mark (2011). A Science of Operations: Machines, Logic and the Invention of Programming. Springer. ISBN 978-1-84882-554-3.
  4. ^ Rojas, Raúl (Spring 2006). "The Zuse Computers". RESURRECTION the Bulletin of the Computer Conservation Society (37). ISSN 0958-7403.
  5. ^ OBITUARY : Konrad Zuse - People - News - The Independent
  6. ^ 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.
  7. ^ "History of the Computer", G. A. Erskine, CERN, Geneva, Switzerland
  8. ^ a b Konrad Zuse - the first relay computer, History of Computers article
  9. ^ Who Made the First Computer, Chris Malcolm, 2000
  10. ^ "Reconstruction of the Z1 Computer | Raúl Rojas". dcis.inf.fu-berlin.de.
  11. ^ Rojas, Raul (7 June 2014). "The Z1: Architecture and Algorithms of Konrad Zuse's First Computer". arXiv:1406.1886 [cs.AR].
  12. ^ Hans Dieter Hellige: Geschichten der Informatik - Visionen, Paradigmen, Leitmotive. Springer-Verlag Berlin Heidelberg 2004. ISBN 3-540-00217-0. P. 36.

Further reading

  • Zuse, Konrad (1993). The Computer - My Life. Springer-Verlag. ISBN 978-3-540-56453-9.
  • Rojas, Raul (2016-03-08). "The Design Principles of Konrad Zuse's Mechanical Computers". arXiv:1603.02396 [cs.OH]. Paper describes the design principles of Zuse Z1.

External links

1937 in science

The year 1937 in science and technology involved some significant events, listed below.

1938 in science

The year 1938 in science and technology involved some significant events, listed below.


The Arithmometer or Arithmomètre was the first digital mechanical calculator strong enough and reliable enough to be used daily in an office environment. This calculator could add and subtract two numbers directly and could perform long multiplications and divisions effectively by using a movable accumulator for the result. Patented in France by Thomas de Colmar in 1820 and manufactured from 1851 to 1915, it became the first commercially successful mechanical calculator. Its sturdy design gave it a strong reputation for reliability and accuracy and made it a key player in the move from human computers to calculating machines that took place during the second half of the 19th century.Its production debut of 1851 launched the mechanical calculator industry which ultimately built millions of machines well into the 1970s. For forty years, from 1851 to 1890, the arithmometer was the only type of mechanical calculator in commercial production, and it was sold all over the world. During the later part of that period two companies started manufacturing clones of the arithmometer: Burkhardt, from Germany, which started in 1878, and Layton of the UK, which started in 1883. Eventually about twenty European companies built clones of the arithmometer until the beginning of World War I.

Binary number

In mathematics and digital electronics, a binary number is a number expressed in the base-2 numeral system or binary numeral system, which uses only two symbols: typically "0" (zero) and "1" (one).

The base-2 numeral system is a positional notation with a radix of 2. Each digit is referred to as a bit. Because of its straightforward implementation in digital electronic circuitry using logic gates, the binary system is used by almost all modern computers and computer-based devices.


The comptometer was the first commercially successful key-driven mechanical calculator, patented in the United States by Dorr E. Felt in 1887.

A key-driven calculator is extremely fast because each key adds or subtracts its value to the accumulator as soon as it is pressed and a skilled operator can enter all of the digits of a number simultaneously, using as many fingers as required, making them sometimes faster to use than electronic calculators. Consequently, in specialized applications, comptometers remained in use in limited numbers into the early 1990s, but with the exception of museum pieces, they have all now been superseded by electronic calculators and computers.

Manufactured without interruption from 1887 to the mid-1970s, it was constantly improved. The mechanical versions were made faster and more reliable, then a line of electro-mechanical models was added in the 1930s. It was the first mechanical calculator to receive an all-electronic calculator engine in 1961, with the ANITA Mark VII model released by Sumlock Comptometer. This created the link between the mechanical calculator industries and the electronic.

Although the comptometer was primarily an adding machine, it could also do subtractions, multiplication and division. Its keyboard consisted of eight or more columns of nine keys each. Special comptometers with varying key arrays were produced for a variety of special purposes, including calculating currency exchanges, times and Imperial weights. The name comptometer was formerly in wide use as a generic name for this class of calculating machine.

History of programming languages

The first high-level programming language was Plankalkül, created by Konrad Zuse between 1942 and 1945. The first high-level language to have an associated compiler was created by Corrado Böhm in 1951, for his PhD thesis. The first commercially available language was FORTRAN (FORmula TRANslation); developed in 1956 (first manual appeared in 1956, but first developed in 1954) by a team led by John Backus at IBM.

When FORTRAN was first introduced it was treated with suspicion because of the belief that programs compiled from high-level language would be less efficient than those written directly in machine code. FORTRAN became popular because it provided a means of porting existing code to new computers, in a hardware market that was rapidly evolving; the language eventually became known for its efficiency.

Pascal's calculator

Pascal's calculator (also known as the arithmetic machine or Pascaline) is a mechanical calculator invented by Blaise Pascal in the early 17th century. Pascal was led to develop a calculator by the laborious arithmetical calculations required by his father's work as supervisor of taxes in Rouen. He designed the machine to add and subtract two numbers directly and to perform multiplication and division through repeated addition or subtraction.

Pascal's calculator was especially successful in the design of its carry mechanism, which adds 1 to 9 on one dial, and when it changes from 9 to 0, carries 1 to the next dial. His innovation made each digit independent of the state of the others, which enabled multiple carries to rapidly cascade from one digit to another regardless of the machine's capacity. Pascal was also the first to shrink and adapt for his purpose a lantern gear, used in turret clocks and water wheels, which could resist the strength of any operator input with very little added friction.

Pascal designed the machine in 1642, and after 50 prototypes, he presented it to the public in 1645, dedicating it to Pierre Séguier, then chancellor of France. Pascal built around twenty more machines during the next decade, many of which improved on his original design. In 1649, King Louis XIV of France gave Pascal a royal privilege (similar to a patent), which gave him the exclusive right to design and manufacture calculating machines in France. Nine Pascal calculators presently exist; most are on display in European museums.

Many later calculators either were directly inspired by, or shaped by the same historical influences which led to, Pascal's invention. Gottfried Leibniz invented his Leibniz wheels after 1671, after trying to add an automatic multiplication feature to the Pascaline. In 1820, Thomas de Colmar designed his arithmometer, the first mechanical calculator strong enough and reliable enough to be used daily in an office environment. It is not clear whether he ever saw Leibniz's device, but he either re-invented it or utilised Leibniz's invention of the step drum.


Z1, Z-1, or Z.1 may refer to:

Z.1 or the Flow of Funds, a U.S. government fiscal report

Z.1, an anti-tank barrier known as Admiralty scaffolding

Z-1 (band), a Japanese idol group

Z1 class Melbourne tram

Z-1 (comics), a DC comics character

Z1 (computer), a mechanical computer designed by Konrad Zuse from 1935 to 1936

Z1 TV, a Czech TV channel

Z1 Zagrebačka Televizija, a Croatian regional television network

Z-1 Suit, an experimental space suit

AEG Z.1, a German aircraft built before World War I from Zagreb

BMW Z1, a two-seat roadster

German destroyer Z1 Leberecht Maass

Great Northern Railway Z-1 class, a class of electric locomotives used by the Great Northern Railway (U.S.)

HZ-1 Aerocycle, an experimental U.S. Army flying platform of the 1960s

Kawasaki Z1, a motorcycle

Sony HVR-Z1, a HDV format camcorder manufactured by Sony

Sony Xperia Z1, a smartphone manufactured by Sony

Zork I, an interactive fiction computer game

the train code for high-speed train between Shanghai and Beijing

Computers designed by Konrad Zuse

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