#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
        char *a, *b;

        char* str = strdup("foobar");
        for (a=str,b=str+strlen(str)-1; a<b; a++,b--)
        {
                *b ^= *a;
                *a ^= *b;
                *b ^= *a;
        }
        printf("%s",str);
}