text: // C++ program to convert whole string to 
  // uppercase or lowercase using STL.
  
  #include <bits/stdc++.h> 
  #include <iostream>
  #include <string>
  
  using namespace std; 
    
  int main(void) 
  { 
      // str1 is the string which is converted to uppercase 
      string str1 = "Xuhua"; 
    
      // using transform() function and ::toupper in STL 
      transform(str1.begin(), str1.end(), str.begin(), ::toupper); 
      cout << str1 << endl; // XUHUA
    
      // str2 is the string which is converted to lowercase 
      string str2 = "Huang"; 
    
      // using transform() function and ::tolower in STL 
      transform(str2.begin(), str2.end(), str2.begin(), ::tolower); 
      cout << str2 << endl;  // "huang"
    
      return 0; 
  } 
  