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

#include <ctype.h>


. . .

These macros classify ASCII-coded integer values 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 where isascii is true and on the single non-ASCII
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

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.