toupper and tolower : char functions « Data Types « C++ Tutorial

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2. Data Types
3. char functions

#include <iostream>
using std::cout;
using std::endl;

#include <cctype>
using std::islower;
using std::isupper;
using std::tolower;
using std::toupper;

int main()
{
   cout << "\nu converted to uppercase is " 
      << static_cast< char >( toupper( 'u' ) )
      << "\n7 converted to uppercase is " 
      << static_cast< char >( toupper( '7' ) ) 
      << "\n$ converted to uppercase is " 
      << static_cast< char >( toupper( '$' ) ) 
      << "\nL converted to lowercase is " 
      << static_cast< char >( tolower( 'L' ) ) << endl;

   return 0;
}

u converted to uppercase is U
7 converted to uppercase is 7
$ converted to uppercase is $
L converted to lowercase is l