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

// convert "hello world" to "HELLO WORLD"
int main(int argc, char ** argv){
  char * s = "hello world";
  int i = 0;
  for ( ; i < strlen(s); ){
    s[i] = toupper(s[i]);
    i = i++;
  }
  printf("s: %s\n", s);
}