My comments on “The Church-Turing Thesis Myth”

By Dennis J. Darland

December 4, 2007

As a model of algorithms that compute an answer to a problem, Turing machines seem perfectly adequate for what a computer can do. Any possible finite I/O can be represented on the tape.

However many General Purpose Computers are actually used for purposes other than computing “answers” to problems. There are constraints on the intermediate states as well as the final state possibly being the answer to the problem. For Operating systems for example, what is important is that the users are provided the services they need. There is no solution at the end. At least, it used to be, there was no stopping some operating systems except to turn the power off. Also for AI systems and Robots, there is not usually a final “answer.”  The Turing model just doesn’t apply. It’s the journey not the destination!  Many practical computer applications run “forever” [similar to OS’s in this way] providing some service.    

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