
1.3 Second-Generation Innovators
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machine that will carry out this task, and so on. Every effective procedure will have a cor-
responding Turing machine.
Such single-purpose machines were, however, only part of Turing’s analysis. He also
demonstrated that it was possible to build one machine that
could imitate any and every single-purpose machine. This new
machine, the so-called universal Turing machine, stood ready to
carry out (at least in theory) any conceivable effective procedure.
The universal Turing machine differs from a simple Turing
machine in that it is able to accept a description of another machine
and imitate ...