#include <string.h>
#include <stdio.h>

int main () {
        char string[]="dave rules";

        char *start = string;
        char *end = string + strlen(string) - 1;
        char *sentinel = end + 1;

        while (start < end) {
                *sentinel = *start;
                *start = *end;
                *end = *sentinel;
                start++;
                end--;
        }
        *sentinel = '\0';
        printf("string is now \'%s\'\n",string);
}