NAME

isalpha, isupper, islower, isdigit, isalnum, isspace, ispunct, isprint, iscntrl, isascii − character classification macros

USAGE

#include <ctype.h>

isalpha(c)

. . . 

DESCRIPTION

These macros classify ASCII-coded integer values by table lookup.  Each is a predicate that returns zero for false, and non-zero for true.  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 uppercase letter

islower c is a lowercase letter

isdigit c is a digit

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 nor alphanumeric)

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

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