19 Nov
2003
19 Nov
'03
2:50 p.m.
On Wed, 19 Nov 2003, William R. Buckley wrote:
of a's
and
like a true
I did not contradict myself. I admit fully that the ideal TM has infinite
memory.
I also note that typical, contemporary computers are not exactly a TM. Yet,
they are computationally equivalent, and if you do not understand that
point,
then you do not understand the foundations of computer science.
Also, you must like the verbage, as you seem compelled to comment.
William R. Buckley
From
Daniel I. A. Cohen's book, Introduction To Compuer Theory,
pp 788
>Definition. If a Turning Machine (TM) has the
property that for every
word
>>it accepts, at the time it halts, it leaves one solid string b's on
>>its Tape starting in cell i, we call it a computer. The
input string we
call
>>the input (or, string of input numbers), and we identify it
as a sequence
>>of nonnegative integers. The string left
on the Tape we call
the output
>and
identify it also as a sequence of nonnegative integers.
The discussion continues,
"Now we finally know what a computer is. Those expensive boxes of
electronics sold as computers are only approximations to the real McCoy.
For one thing, they almost never come with an infinite memory TM."
William, you are completely contradicting yourself at this point. You
started out asserting that all computers are Turning machines, then you
quoted the source above which is saying that they really aren't, and
implying exactly what Tony Duell said a few messages ago, which is that
they aren't because they don't have infinite memory.