isupper : char functions « Data Types « C++ Tutorial

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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 << "\nAccording to isupper:\n"
      << ( isupper( 'D' ) ? "D is an" : "D is not an" ) 
      << " uppercase letter\n"
      << ( isupper( 'd' ) ? "d is an" : "d is not an" ) 
      << " uppercase letter\n"
      << ( isupper( '8' ) ? "8 is an" : "8 is not an" ) 
      << " uppercase letter\n"
      << ( isupper('$') ? "$ is an" : "$ is not an" ) 
      << " uppercase letter\n";

   return 0;
}

According to isupper:
D is an uppercase letter
d is not an uppercase letter
8 is not an uppercase letter
$ is not an uppercase letter