It's all in the printf format string. The first parameter to printf is s, the string itself.
So this is equivalent to:
Code:
#include <stdio.h>
char*s="char*s=%c%s%c;main(){printf(s,34,s,34);}";
main()
{
printf("char*s=%c%s%c;main(){printf(s,34,s,34);}",34,s,34);
}
Now just match up the %-codes with the parameters:
%c=>34
%s=>s again
%c=>34.

34 is the ASCII code for ".