Thread: detecting characters

I am storing a string in an array of type of char and then break the string length into lowercase, uppercase, digits, other printable characters and whitespace.

For the "other printable characters" I am using

Code:

if (isgraph(str[i]) && (isalnum(str[i]) == false))

is there any library function which returns just that or shall i stick with the above line?

Thank You