Z3 (computer)

Zuse Z3 replica on display at Deutsches Museum in Munich

Konrad Zuse's Z3 was the world's first working programmable, fully automatic computing machine; whose attributes, with the addition of conditional branching, have often been the ones used as criteria in defining a computer. The Z3 was built with 2,000 relays: a request for funding for an electronic successor was denied as "strategically unimportant" (German: nicht kriegswichtig). It had a clock frequency of about 5 to 10 Hz, and a word length of 22 bits. Calculations on the computer were performed in full binary floating point arithmetic. The Z3 read programs off a punched film.

The machine was completed in 1941. On 12 May 1941, it was successfully presented to an audience of scientists including the professors Alfred Teichmann and C. Schmieden of the [Deutsche Versuchsanstalt für Luftfahrt] Error: {{Lang}}: text has italic markup (help) ("German Laboratory for Aviation"), in Berlin. The original Z3 was destroyed in 1943 during an Allied bombardment of Berlin. A fully functioning replica was built in the 1960s by the originator's company Zuse KG and is on permanent display in the Deutsches Museum.

The Z3 was used by the German Aircraft Research Institute to perform statistical analyses of wing flutter in aircraft design. Dr. Joseph Jennissen, member of the Reich Air Ministry acted as the federal supervisor.

How the Z3 relates to other work

Unlike the first non-programmable mechanical computer, built by Wilhelm Schickard in 1623, the Z3 was program-controlled.

The first design of a program-controlled computer was Charles Babbage's Analytical Engine in the 1830s. However, Babbage failed to build it. (The Science Museum (London) built a replica of his Difference Engine No. 2.)

Zuse designed the Z1 upon which the Z3 was based 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. The Z3 used the same design but implemented using relays. The Z3 was completed in 1941 and was faster and far more reliable than the Z1. The Z3 floating point was improved over that of the Z1 in that it implemented exception handling. 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 for reprogramming no rewiring was necessary.

The success of Zuse's Z3 is often attributed to its use of the simple binary system. This was invented roughly three centuries earlier by Gottfried Leibniz; Boole later used it to develop his Boolean algebra. In 1937, Claude Shannon of MIT introduced the idea of mapping Boolean algebra onto electronic relays in a seminal work on digital circuit design.

The United Kingdom's 10 codebreaking Colossus computers (1943) were the first electronic digital computers, other than the one-off Atanasoff–Berry Computer (1942). They used thermionic valves (vacuum tubes) and binary representation of numbers. Programming was by means of re-plugging patch panels and setting switches. This development was kept secret for many decades which led to claims of "firsts" in computing that later turned out to be incorrect.

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

The Manchester Baby of 1948 and the EDSAC of 1949 were the world's first computers with internally stored programs. They implemented a concept frequently (but erroneously) attributed to a 1945 paper of John von Neumann and colleagues. Von Neumann's own papers give proper credit to Alan Turing, and the concept had actually been mentioned earlier by Konrad Zuse himself, in a 1936 patent application (which was rejected).

Relation to the concept of 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. He proposes 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.

Specifications

• Frequency: 5.3 Hertz
• Arithmetic Unit: Floating point, 22 bit, add, subtract, multiply, divide, square root
• Average calculation Speed: Addition 0.8 seconds Multiplication 3 seconds
• Power Consumption: Around 4000 watts
• Weight: Around 1,000 kilograms (2,200 lb)
• Elements: Around 2,600 relays
• Memory: 64 words with a length of 22 bits
• Input: Decimal floating point numbers
• Output: Decimal floating point numbers

See also

• IBM SSEC
• Manchester Mark 1
• Manchester Small-Scale Experimental Machine

References

• B. Jack Copeland, ed. (2006). Colossus: The Secrets of Bletchley Park's Codebreaking Computers. Oxford University Press. ISBN 0-19-284055-X.

External links

• Z3 page at the Technical University of Berlin
• The Life and Work of Konrad Zuse
• Konrad Zuse?s Legacy: The Architecture of the Z1 and Z3 (PDF)
• How to Make Zuse's Z3 a Universal Computer Raúl Rojas
• Raúl Rojas, The Zuse Computers In resurrection, the bulletin of the Computer Conservation Society ISSN 0958-7403 Number 37 Spring 2006