Both of you are wrong. You do not use any of the "is*" functions on integers. Yes, they take integers, but they expect the range to be a valid range for 'char'. They translate that decimal value into the ascii value of the corresponding character, and tell you if that is a character. They are meant to be used like so:
Code:
char c = '1';
if( isalpha( c ) )
printf("%c is an alpha-numeric character.\n", c );
You do not pass it a value like 200 and
expect it to say that 200 is a number.
Code:
if( scanf("%d", &n ) == 1 )
printf("%d is a number.\n", n );
else
printf("You entered an invalid value.\n");
Quzah.