# ctype(3)

    NAME
         ctype, isalpha, isupper, islower, isdigit,  isxdigit,  isalnum,  isspace,
         ispunct,  isprint, isgraph, iscntrl, isascii, toupper, tolower, toascii -
         character classification macros

    SYNOPSIS
         #include <ctype.h>

         int isalpha(int c)
         ...

    DESCRIPTION
         These macros classify characters by table lookup.  Each  is  a  predicate
         returning  nonzero  for  true,  zero  for false.  Isascii and toascii are
         defined on all integer values; the rest are defined only on the range  of
         unsigned char and on the special value EOF (see stdio(3)).

         isalpha        c is a letter

         isupper        c is an upper case letter

         islower        c is a lower case letter

         isdigit        c is a digit

         isxdigit       c is a hex digit

         isalnum        c is an alphanumeric character

         isspace        c is a space, tab, carriage return, newline, vertical tab,
                        or formfeed

         ispunct        c  is  a  punctuation  character  (neither   control   nor
                        alphanumeric)

         isprint        c is a printing character,  code  040(8)  (space)  through
                        0176 (tilde)

         isgraph        c is a printing character, similar to isprint except false
                        for space.

         iscntrl        c  is  a  delete  character  (0177)  or  ordinary  control
                        character (less than 040).

         isascii        c is an ASCII character, code less than 0200

         tolower        c is converted to lower case.  Return value  is  undefined
                        if not isupper(c).

         toupper        c is converted to upper case.  Return value  is  undefined
                        if not islower(c).

         toascii        c is converted to be a valid ascii character.

    SEE ALSO
         ascii(7)