Using functions isalpha : 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 isalpha:\n"
      << ( isalpha( 'A' ) ? "A is a" : "A is not a" ) << " letter\n"
      << ( isalpha( 'b' ) ? "b is a" : "b is not a" ) << " letter\n"
      << ( isalpha( '&' ) ? "& is a" : "& is not a" ) << " letter\n"
      << ( isalpha( '4' ) ? "4 is a" : "4 is not a" ) << " letter\n";


   return 0;
}

According to isalpha:
A is a letter
b is a letter
& is not a letter
4 is not a letter