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.
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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.
