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

int main(){
  char * w = "HELLO";
  char z[6];
  int len = strlen(w);
  printf("len: %d\n", len);
  for (int i=0; i < len; i++){
    printf("w[%d] = %c (%c)\n", i, w[i], tolower(w[i]));
    // w[i] = tolower(w[i]); caused a seg fault.  why?
    z[i] = tolower(w[i]);
  }

  printf("w: %s\n", z);
    
}