ctype(3)
NAME
isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct, isprint, isgraph, iscntrl, isascii − character classification
SYNTAX
#include <ctype.h>
int isalpha(c)
int c;
int isalnum(c)
int c;
int isascii(c)
int c;
int iscntrl(c)
int c;
int isdigit(c)
int c;
int isgraph(c)
int c;
int islower(c)
int c;
int isprint(c)
int c;
int ispunct(c)
int c;
int isspace(c)
int c;
int isupper(c)
int c;
int isxdigit(c)
int c;
DESCRIPTION
These macros classify ASCII-coded integer values by table lookup. Each return nonzero for true and zero for false. The isascii macro is defined on all integer values. The rest are defined only where isascii is true and on the single non-ASCII value EOF. For further information, 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, vertical tab, or formfeed
ispunct c is a punctuation character (neither control nor alphanumeric nor blank (040))
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).
isascii c is an ASCII character, code less than 0200