On Tue, Oct 8, 2013 at 1:20 PM, Steven D'Aprano <st...@pearwood.info> wrote: > On Tue, 08 Oct 2013 10:46:50 +0530, Ravi Sahni wrote: > >> On Tue, Oct 8, 2013 at 8:47 AM, rusi <rustompm...@gmail.com> wrote: >>> I can only say how ironic it sounds to someone who is familiar with the >>> history of our field: Turing was not a computer scientist (the term did >>> not exist then) but a mathematician. And his major contribution was to >>> create a form of argument so much more rigorous than what erstwhile >>> mathematicians were used to that he was justified in calling that math >>> as a machine. >>> >>> The irony is that today's generation assumes that 'some-machine' >>> implies its something like 'Intel-machine'. To get out of this >>> confusion ask yourself: Is it finite or infinite? If the TM were finite >>> it would be a DFA If the Intel-machine (and like) were infinite they >>> would need to exist in a different universe. >> >> With due respect Sir, you saying that Turing machine not a machine? Very >> confusion Sir!!! > > The mathematical ideal Turing Machine has an infinitely long tape, > equivalent to infinite memory, and may take an unbounded amount of time > to complete the computation. Since no *actual* physical machine can be > infinitely big, and in practice there are strict limits on how long we > are willing to wait for a computation to complete, in the *literal* > sense, Turing Machines are not *actual* machines. They are a mathematical > abstraction. > > But in practice, we can wave our hands and ignore this fact, and consider > only not-quite-Turing Machines with finite amounts of tape, and note that > they are equivalent to physical machines with finite amounts of memory. > One could even build such a finite Turing Machine, although of course it > would be very slow. Or one can simulate it in software. > > So in that sense, computers are Turing Machines. Anything a physical > computing device can compute, a Turing Machine could too. The converse is > not true though: a Turing Machine with infinite tape can compute things > where a real physical device would run out of memory, although it might > take longer than anyone is willing to wait.
Thanks Sir the detailed explanation. You are offering me many thoughts inside few words so I will need some time to meditate upon the same. Presently Sir, I wish to ask single question: What you mean "wave our hands"?? Thanks -- Ravi -- https://mail.python.org/mailman/listinfo/python-list
