>    I did one using an integer based square root
 > function which
 >    only checks one less than or one greater than
 > multiples of
 >    six, which all primes seem to be for some reason.
 > :)

    I did one for the Z80 using bits. You just reset successively all bits
representing mutiples of all previous primes, and what remains a 1 must
represent a prime. 18 seconds to go through the entire 4 megabytes of bank
switched 64KB memory, IIRC.

    It should work well enough for 32bit or wider machines, too, but it's
at its best in assembler rather than C.

Best wishes,
Bill.

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