Portable Self-Replicating C Contest

[Dan Christensen]

In article <12144 at haddock.ima.isc.com> karl at haddock.ima.isc.com (Karl Heuer) writes:
>*** Portable Self-Replicating C Contest ***
>
>Rules:
>4.  The source must use only the ISO 646 character set, using trigraphs as
>    needed.
>
>(You might not like trigraphs, but it makes the puzzle more challenging.)
>
>Karl W. Z. Heuer (ima!haddock!karl or karl at haddock.isc.com), The Walking Lint

Sorry if this is trivial, but what is the ISO 646 character set and what
are trigraphs?

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Dan Christensen, Computer Graphics Lab,	         jdchrist at watcgl.uwaterloo.ca
University of Waterloo, Waterloo, Ont.	         jdchrist at watcgl.waterloo.edu