Table 4 <ctype.h> functions

         Character Testing Functions
-----------------------------------------------------
isalnum      alphanumeric ( isalpha || isdigit)

isalpha      alphabetic

iscntrl      control (beware!)

isdigit      '0' through '9'

isgraph      visible when printed

islower      lower case alphabetic

isprint      isgraph || ' '

ispunct      isgraph && !isalnum

isspace      whitespace

isupper      upper case alphabetic

isxdigit     isdigit || 'a' thru 'f' || 'A' thru 'F'

        Character Mapping Functions
-----------------------------------------------------
tolower      convert to lower case (if applicable)

toupper      convert to upper case (if applicable)