iscntrl : control character predicate

Synopsis

#include <ctype.h>
int iscntrl(int c);
```### Description

iscntrl is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for control characters, 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 iscntrl'.### Returns

iscntrl returns non-zero if c is a delete character or ordinary control character (0x7F or 0x00--0x1F).

---

**Authoritative source**: BUSMASTER DITA help source `iscntrl.dita`, compiled into `BUSMASTER.CHM` with the application.