ctype(3)
NAME
isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct, isprint, isgraph, iscntrl, isascii, toascii − character classification macros
SYNTAX
#include <ctype.h>
isalpha(c)
. . .
DESCRIPTION
These macros classify ASCII-coded integer values by table lookup. Each is a predicate returning nonzero for true, zero for false. Isascii is defined on all integer values; the rest are defined only where isascii is true and on the single non-ASCII value EOF (see stdio(3S)).
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 hexadecimal digit [0-9], [A-F], or [a-f]
isalnum c is an alphanumeric character
isspace c is a space, tab, carriage return, newline, or formfeed
ispunct c is a punctuation character (neither control, alphanumeric, nor space).
isprint c is a printing character, code 040(8) (space) through 0176 (tilde)
isgraph c is a printing character, like isprint except false for space.
iscntrl c is a delete character (0177) or ordinary control character (less than 040) except for space characters. .
isascii c is an ASCII character, code less than 0200