andersw+ at pitt.edu (Anders N Weinstein) writes:
>In article <6i7h70$gij at ux.cs.niu.edu>, Neil Rickert <rickert at cs.niu.edu> wrote:
>>andersw+ at pitt.edu (Anders N Weinstein) writes:
>>There are things that are being done by the computer on my desk that
>>I could not map into a Turing machine.
>>I'm not talking 'analog'. My concern is with interaction. A Turing
>>machine is not interactive. A person is, and the computer on my desk
>>is.
>Formal models of computation treat *interaction* in terms of
>symbols getting written onto the tape memory. This seems a
>pretty good model of how the operating system code views a device.
Right. But you generally have to model this as a Turing machine with
oracle. You can't model it as a plain Turing machine. The oracle
places the interactive symbols on the tape in a way that is not
predictable from within the Turing machine model.
But there is not much you can say about a Turing machine with
oracle. If you are fortunate enough to have an oracle capable of
solving a computationally unsolvable problem (such as the Halting
problem), then your TM with oracle is also able to solve that problem
by virtue of its ability to consult (interact with) the oracle.