..index:: stdbool.h

33. Boolean type and values <stdbool.h>

The header <stdbool.h> defines four macros. The macro

bool

expands to _Bool.

The remaining three macros are suitable for use in #if preprocessing directives. They are

true

which expands to the integer constant 1,

false

which expands to the integer constant 0, and

__bool_true_false_are_defined

which expands to the integer constant 1.

Notwithstanding the provisions of Macro Replacement, a program may undefine and perhaps then redefine the macros bool, true and false.