Character classification and conversion library functions

#include <cctype>
// isalpha(c) non-zero if c is alphabetic, 0 if not 
// isupper(c) non-zero if c is upper case, 0 if not 
// islower(c) non-zero if c is lower case, 0 if not 
// isdigit(c) non-zero if c is digit, 0 if not 
// isalnum(c) non-zero if isalpha(c) or isdigit(c), 0 if not 
// isspace(c) non-zero if c is blank, tab, newline, return, formfeed, vertical tab 
// toupper(c) return c converted to UPPER CASE 
// tolower(c) return c converted to lower case 
int main( )
{
    char ch = 'A';
    int result = isalpha( ch );
    return 0;
}