What's the C99 boolean data type and how to use it?
The C99 standard for C language supports bool variables. Unlike C++, where no header file is needed to use bool, a header file “stdbool.
In computer science, the Boolean (sometimes shortened to Bool) is a data type that has one of two possible values (usually denoted true and false) which is intended to represent the two truth values of logic and Boolean algebra.
C does not have boolean data types, and normally uses integers for boolean testing. Zero is used to represent false, and One is used to represent true.
Boolean operator examples>= – True if a number is greater than or equal to another. <= – True if a number is less than or equal to another. == – True if two values are equivalent. !=
Include <stdbool.h>
header
#include <stdbool.h> int main(void){ bool b = false; }
Macros true
and false
expand to 1
and 0
respectively.
Section 7.16
Boolean type and values < stdbool.h >
- 1 The header
<stdbool.h>
defines four macros.- 2 The macro
- bool expands to _Bool.
- 3 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.
- 4 Notwithstanding the provisions of 7.1.3, a program may undefine and perhaps then redefine the macros bool, true, and false.
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