CTYPE(3C)
NAME
isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct, isprint, isgraph, iscntrl, isascii − character classification
SYNOPSIS
#include <ctype.h>
int isalpha (c)
int 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 [0-9]
isxdigit c is a hexidecimal digit [0-9], [A-F] or [a-f]
isalnum c is an alphanumeric
isspace c is a space, tab, carriage return, new-line, vertical tab, or form-feed
ispunct c is a punctuation character (neither control nor alphanumeric)
isprint c is a printing character, code 040 (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).
isascii c is an ASCII character, code less than 0200