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The Annotated Turing: A Guided Tour Through Alan Turing's Historic Paper on Computability and the Turing Machine by Charles Petzold

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9  The Universal Machine

The machine that Turing describes in the next section of his paper is known today as the Universal Turing Machine, so called because it's the only machine we need. The individual computing machines presented earlier were not guaranteed to be implemented similarly or even to have interchangeable parts. This Universal Machine, however, can simulate other machines when supplied with their Standard Descriptions. The Universal Machine is, we would say today, programmable.

6. The universal computing machine.

It is possible to invent a single machine which can be used to compute any computable sequence. If this machine images is supplied with a tape on the beginning of which is written the S.D of some computing machine images, then images will compute the same sequence as images. In this section I explain in outline the behaviour of the machine. The next section is devoted to giving the complete table for images.

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There's that script font again. Turing uses for an arbitrary machine and for ...

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