A friend sent me this riddle (which I imagine isn't his, but nevermind) via mail, and I thought it cute enough to share:

Find three ways to change/insert/delete a single character in the following code, so that the resulting code will print 20 star characters (*). Remember, for each solution you can only change one character, and there are at least three different solutions.

#include <stdio.h>

int main()
{
    int i, N = 20;
    for ( i = 0 ; i < N ; i-- )
        printf( "*" );
    return 0;
}

I'll post the solution in a few days, feel free to yell "eureka" in the comment section or whatever.