ctype, isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace,
ispunct, isprint, isgraph, iscntrl, isascii, toupper, tolower, toascii -
character classification macros
int isalpha(int c)
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,
ispunct c is a punctuation character (neither control nor
isprint c is a printing character, code 040(8) (space) through
isgraph c is a printing character, similar to isprint except false
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.