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)