C++ Boolean Type
A boolean is the simplest data type of all: it can hold only one of two values, true or false. Booleans power every decision your program makes, from if statements to loops, so they are worth understanding well.
The bool Type
You declare a boolean with the keyword bool and assign it either true or false. Internally C++ stores true as 1 and false as 0, which is why a bool prints as a number unless you tell it otherwise.
Declaring booleans
#include <iostream>
using namespace std;
int main() {
bool isRaining = false;
bool hasTicket = true;
cout << "Raining: " << isRaining << endl; // 0
cout << "Has ticket: " << hasTicket; // 1
return 0;
}Booleans from Comparisons
You rarely type true or false by hand. More often a boolean is the result of a comparison, such as checking whether one number is greater than another. Comparison operators like >, <, and == always produce a bool.
Comparisons return booleans
#include <iostream>
using namespace std;
int main() {
int age = 20;
bool isAdult = age >= 18;
cout << "Age: " << age << endl;
cout << "Is adult: " << isAdult << endl; // 1
cout << "Over 65? " << (age > 65); // 0
return 0;
}Note: To print the words "true" and "false" instead of 1 and 0, send std::boolalpha to cout: cout << boolalpha << isAdult;
- A bool holds only true or false.
- true is stored as 1 and false as 0.
- Comparison operators return a bool.
- Booleans control if statements and loops.
