Using functions isxdigit : char functions « Data Types « C++ Tutorial

1. C++ Tutorial
2. Data Types
3. char functions

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

#include <cctype>
using std::isalnum;
using std::isalpha;
using std::isdigit;
using std::isxdigit;

int main()
{
   cout << "\nAccording to isxdigit:\n"
      << ( isxdigit( 'F' ) ? "F is a" : "F is not a" )
      << " hexadecimal digit\n"
      << ( isxdigit( 'J' ) ? "J is a" : "J is not a" )
      << " hexadecimal digit\n"
      << ( isxdigit( '7' ) ? "7 is a" : "7 is not a" )
      << " hexadecimal digit\n"
      << ( isxdigit( '$' ) ? "$ is a" : "$ is not a" )
      << " hexadecimal digit\n"
      << ( isxdigit( 'f' ) ? "f is a" : "f is not a" )
      << " hexadecimal digit" << endl;


   return 0;
}

According to isxdigit:
F is a hexadecimal digit
J is not a hexadecimal digit
7 is a hexadecimal digit
$ is not a hexadecimal digit
f is a hexadecimal digit