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STDBOOL(3) Library Functions Manual STDBOOL(3)

stdboolstandard boolean types

#include <stdbool.h>

The <stdbool.h> header defines four macros:

  1. bool, which expands to _Bool;
  2. true, which expands to the integer constant 1;
  3. false, which expands to the integer constant 0; and
  4. __bool_true_false_are_defined, which expands to the constant 1.

The ability to undefine and redefine the macros bool, true, and false is an obsolescent feature that may be withdrawn in a future version of a standard.


The <stdbool.h> header conforms to ISO/IEC 9899:1999 (“ISO C99”) and IEEE Std 1003.1-2001 (“POSIX.1”).

The <stdbool.h> header was first introduced in NetBSD 1.6.

March 21, 2010 NetBSD-7.0.1