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CTYPE(3) Library Functions Manual CTYPE(3) NAME isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, is- punct, isprint, isgraph, iscntrl, isascii - character classification SYNOPSIS #include <ctype.h> isalpha(c) isupper(c) islower(c) isdigit(c) isxdigit(c) isalnum(c) isspace(c) ispunct(c) isprint(c) isgraph(c) iscntrl(c) isascii(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; stdio(3). isalpha c is a letter, a-z or A-Z isupper c is an upper case letter, A-Z islower c is a lower case letter, a-z isdigit c is a digit, 0-9 isxdigit c is a hexadecimal digit, 0-9 or a-f or A-F isalnum c is an alphanumeric character, a-z or A-Z or 0-9 isspace c is a space, horizontal tab, vertical tab, carriage return, newline, or formfeed (040, 011, 012, 013, 014, 015) ispunct c is a punctuation character (one of !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~) isprint c is a printing character, 040 (space) through 0176 (tilde) isgraph c is a visible printing character, 041 (exclamation) through 0176 (tilde) iscntrl c is a delete character, 0177, or ordinary control character, 000 through 037 isascii c is an ASCII character, 000 through 0177 SEE ALSO tolower(3), ascii(6) CTYPE(3)