### 3.3 `isascii`—ASCII character predicate

Synopsis

         #include <ctype.h>
         int isascii(int c);

Description
`isascii` is a macro which returns non-zero when c is an ASCII character, and 0 otherwise. It is defined for all integer values.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ``#undef isascii`'.

Returns
`isascii` returns non-zero if the low order byte of c is in the range 0 to 127 (`0x00`–`0x7F`).

Portability
`isascii` is ANSI C.

No supporting OS subroutines are required.