#include <cctype>
#include <iostream>
 
using namespace std;
 
int main()
{
  for (int i=1;i<=10;i++){
 
  char ch;
 
  cout<<"Enter a character: ";
  cin>> ch;
 
  if ( isalpha ( ch ) ) {
    if ( isupper ( ch ) )
      cout<<"The lower case equivalent is "<< static_cast<char> ( tolower ( ch ) ) <<endl;
    else
      cout<<"The upper case equivalent is "<< static_cast<char> ( toupper ( ch ) )<<endl;
  }
  else
    cout<<"The character is not a letter"<<endl;
 
 
  while ( cin.get ( ch ) && ch != '\n' )
    ;
}
 system("pause");
 return 0;
}

#include <iostream>
#include <algorithm>
#include <string>
#include <cctype>
 
struct upper {
  int operator() ( int c )  
  {
      return toupper ( static_cast<unsigned char> ( c ) );
  }
};
 
struct lower{
  int operator() ( int c )  
  {
      return tolower( static_cast<unsigned char> ( c ) );
  }
};
 
int main(){
    std::string str = "Test StrinG";
    std::transform(str.begin(),str.end(),str.begin(),upper());
    std::cout << str;
    std::transform(str.begin(),str.end(),str.begin(),lower());
    std::cout << str;
    return 0;
}