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. The macro isascii 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(.).
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, new line, 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