Using functions isalnum : 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 isalnum:\n"
      << ( isalnum( 'A' ) ? "A is a" : "A is not a" )
      << " digit or a letter\n"
      << ( isalnum( '8' ) ? "8 is a" : "8 is not a" )
      << " digit or a letter\n"
      << ( isalnum( '#' ) ? "# is a" : "# is not a" )
      << " digit or a letter\n";


   return 0;
}

According to isalnum:
A is a digit or a letter
8 is a digit or a letter
# is not a digit or a letter