[redhead]

one thing comes to mind

 //C++
#include <iostream>
#include <string>
void reverse(std::string &str)
{
    char tmp;
    for(int i=str.size()-1, j=0; i > j; i--, ++j)
    {
        tmp=str[i];
        str[i]=str[j];
        str[j]=tmp; 
    }
}

int main(){
  std::string foo("string");
  std::cout << foo << std::endl;
  reverse(foo);
  std::cout << foo << std::endl;
  return 0;
}

/* C */
#include <stdio.h>
#include <string.h>

void reverse(char str[])
{
    char tmp;
    int i = strlen(str)-1, j=0;
    for(; i > j; i--, ++j)
    {
        tmp=str[i];
        str[i]=str[j];
        str[j]=tmp; 
    }
}

int main(){
  char foo[] = "string";
  printf("%s\n", foo);
  reverse(foo);
  printf("%s\n", foo);
  return 0;
}