isdigit
---decimal digit predicate#include <ctype.h> int isdigit(int c);Description
isdigit
is a macro which classifies ASCII integer values by table
lookup. It is a predicate returning non-zero for decimal 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 isdigit
'.
Returns
isdigit
returns non-zero if c is a decimal digit (0
--9
).
Portability
isdigit
is ANSI C.
No supporting OS subroutines are required.