isxdigit---hexadecimal digit predicate#include <ctype.h> int isxdigit(int c);Description
isxdigit is a macro which classifies ASCII integer values by table
lookup. It is a predicate returning non-zero for hexadecimal digits,
and 0 for other characters. It is defined only when
isascii(c) is true or c is EOF.
You can use a compiled subroutine instead of the macro definition by
undefining the macro using `#undef isxdigit'.
Returns
isxdigit returns non-zero if c is a hexadecimal digit
(0--9, a--f, or A--F).
Portability
isxdigit is ANSI C.
No supporting OS subroutines are required.