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30 November 1936Reputable source · 2 sourcesWell documented

Turing describes the universal machine

A 24-year-old mathematician imagines a machine that could compute anything computable

On the timeline · around 30 November 1936 · Mechanical and Theoretical FoundationsMechanical and Theoretical FoundationsThe Electronic ComputerTuring describes the universal machine19001910192019301940

Quick facts

Author
Alan Turing
Published
30 November and 23 December 1936, Proceedings of the London Mathematical Society
Key idea
The universal machine: one machine that can imitate any other computing machine
Term coined by
Alonzo Church, in a 1937 review of the paper

What happened

Alan Turing published 'On Computable Numbers, with an Application to the Entscheidungsproblem' in the Proceedings of the London Mathematical Society, in installments dated 30 November and 23 December 1936. He was attacking a question posed by mathematician David Hilbert: whether a single mechanical procedure could decide, for any statement in formal logic, if it was provable. Turing answered by inventing an idealized device, an 'automatic machine' that reads and writes symbols on an infinite tape one cell at a time, following a fixed table of rules. He then described a 'universal machine' that could read a description of any other such machine off the tape and imitate it exactly, showing that one general-purpose device could in principle run any computation.

Why it matters

The paper proved that some mathematical problems have no mechanical solution at all, the halting problem, while simultaneously describing, in the universal machine, the theoretical blueprint for a stored-program computer that runs any program fed to it. Every general-purpose computer built since is, in the abstract sense Turing described, a physical approximation of that single idea.

How we know

The Stanford Encyclopedia of Philosophy's entry on Turing Machines and the IEEE's Engineering and Technology History Wiki both describe the paper's content and the 1936 date directly from the historical and scholarly record; the paper itself was named 'Turing machines' only afterward, by logician Alonzo Church's 1937 review.

Sources

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