How Many Games of Chess?

This is tangentially related to crypto.  I've been reading A.K. Dewdney's
_The New Turning Omnibus_ recently to refresh my memory of all that stuff
I learned in undergrad that I'm going to see again on the Comp Sci GRE
shortly. :-)  Anyway, I was glancing through the chapters on complexity,
computabilty, and minimax trees, and I got to wondering something:  how
many possible games of chess are there?  I know that it has to be a finite
number, but I'm not sure how to go about finding this number.  Any
pointers would be appreciated.

Ken

=============================================================================
Ken Kirksey            kkirksey@world.std.com            Mac Guru & Developer
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When the going gets tough, the tough hide under the table.
                                                           -Edmund Blackadder

Ken B Kirksey writes:
 > how many possible games of chess are there?  

A lot.  I recall a somewhat compulsive friend calculating how long it
would take to generate the complete game tree assuming the surface of
Jupiter were covered with Cyber 7600's (it was a while ago), and it
was a long time.

It's probably tricky to figure the count because you can't just use a
simple combinatorial system; you have to filter out illegal
configurations, and of course the paths down the game tree don't all
terminate in the same number of hops (and you have to find the ones
that don't terminate at all!).

Then again, I'm not a mathematician and I don't play chess, so the
word "tricky" above needs to be re-evaluated subjectively.

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