[intv] convert string to upper or lower case

//Problem: convert string to upper case or lowercase.
//Save as: main.cpp and compile as: g++ -o main main.cpp

#include <iostream>
#include <string.h> //required for strlen

using namespace std;

char * toUpperOrLower(char *, int);


int main(){
  char *str1 = "A Toyota! Race fast, safe car. A Toyota.";

  cout << str1 << " **  " << toUpperOrLower(str1, 1) << endl;
  cout << str1 << " **  " << toUpperOrLower(str1, 0) << endl;

}


char * toUpperOrLower(char *a, int UpOrLow){
  char *c;
  c = (char *)malloc(sizeof(char)*strlen(a));
  if (NULL == c) {cout << "ERROR" << endl;}

  for (int i=0; i < strlen(a); i++){
    c[i] = a[i];
    if (UpOrLow == 0){
      //lower case
      if ((a[i] >= 0x41) && (a[i] <= 0x5a)){
	c[i] = (char)(a[i] | 0x20);
      }
    }else{
      //upper case
      if ((a[i] >= 0x61) && (a[i] <= 0x7a)){
	c[i] = (char)(a[i] & 0xdf);
      }
    }
  }
  return c;
}