The bool data type in C++ stands for Boolean values, which are True and False. In C++, 1 stands for True whereas 0 stands for False. The keyword “bool” is used to declare a Boolean data type. The addition of bool data type is a one of the newer features of C++ language.

Use of Boolean Data Type

The Boolean (bool) data type is used in the following ways −

• In conditions where we need to have binary values, i.e., values which represent two states of a variable.
• When we need to run loops based on certain conditions, we use bool data types.
• In case of having null values, we generally relate them to bool data types.
• For comparing two values for equality or inequality, we generally use bool data types.

Values of Boolean (bool) Data Type

The bool data types in C++ can have one of two values, and these values are as follows −

• True or 1
• False or 0

As stated earlier, Boolean 1 means true whereas Boolean 0 means false in C++ compilation.

Creating a Boolean Variable

We can declare a Boolean variable using the “bool” keyword followed by the variable name.

Syntax

Use the following syntax to create a Boolean type variable −

bool variable_name = [value];

Here, [value] is an optional and can be used to assign value during the declaration.

Example

In the following examples, we are declaring a Boolean variable, assigning a value to it.

// C++ program to demonstrate 
// bool data type 
#include <iostream> 
using namespace std; 

// Driver code 
int main() { 
   bool flag;
   flag=1;//this is true    
   cout<<flag;    
   return 0; 
}

Example of bool Data Type

The following example demonstrate the use of Boolean (bool) data type −

// C++ program to demonstrate
// bool data type
#include <iostream>
using namespace std;

int main(){ 
   bool flag;
   flag=1;//this is true
   bool flag1=true;

   cout<<flag<<" "<<flag1<<endl;

   int count=0;
   while(flag){
      //condition where flag is true
      count++;
      if(count>=3) flag=false;
   }

   cout<<count<<" "<<flag<<endl;

   if(flag1) cout<<"True flag1"<<endl;
      else cout<<"False flag1"<<endl;

   return 0; 
}

Output

1 1
3 0
True flag1

Implicit Conversion of Bool Variables

Boolean data types can be implicitly converted to numeric data types, and vice-versa. This is possible as any value greater than 0 has a Boolean true value, whereas any value less than or equal to 0 has a Boolean false value.

Also, the Boolean values can be added in form of integers to integral variables, using implicit conversion techniques. Hence, when we add a Boolean value to an integer, it gets incremented by 1 if the value is true, otherwise it remains same as false value corresponds to 0.

Example

This is clearly explained in the examples given below −

// C++ program to demonstrate
// bool data type
#include <iostream> 
using namespace std;

int main() {
   bool flag;
   flag=1;//this is true
   bool flag1=true;

   cout<<flag<<" "<<flag1<<endl;

   int count=0;
   int x=12;
   float y=35.45;
   bool k=count, k1=x, k2=y;
   int sum=x+flag+flag1;

   cout<<k<<" "<<count<<" "<<k1<<" "<<x<<" "<<k2<<" "<<y<<" "<<endl;
   cout<<”After adding Boolean and integer values : ”<< sum<<endl;
   return 0; 
}