Use of Bool in C

use of bool in c

Bool in C

In this section we will discuss the use of bool in the C programming language.

The C programming language, as of C99, supports the use of boolean with the help of built-in -type _Bool. bool can be used in place of _Bool if stdbool.h header file is included.


Bool is data type which was introduced in C99. The variables of Bool only holds two value 0(false) and 1(true). When storing value in the Bool data type 0 is stored when the input is 0 and for every other input 1 is stored. For example say we have input 2019 then 1 will be stored.

Example :

int main()
    _Bool check =    2019;
    printf("the output is %d",check);
    return 0;

Output :

the output is 1

As we can see even when the input is 2019 the output is 1.

We have another way of using boolean arithmetic in C Programming language which by using bool which is a macros in the stdbool.h header.


There are 4 macros in the header stdbool.h in the C Standard Library for the C programming language for a Boolean data type. This header was introduced in C99.

The macros as defined in the ISO C standard are :

  • bool which expands to _Bool
  • true which expands to 1
  • false which expands to 0
  • __bool_true_false_are_defined which expands to 1


#include <stdio.h>
int main()
    bool x=true,y=false;
    printf("the value of x: %d",x );
    printf("\nthe value of y: %d",y );
    return 0;

Output :

the value of x: 1
the value of y: 0

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