C++ Booleans
C++ Booleans
Very often, in programming, you will need a data type that can only have one of two values, like:
- YES / NO
- ON / OFF
- TRUE / FALSE
For this, C++ has a bool data type, which can take the values true
(1) or false (0).
Boolean Values
A boolean variable is declared with the bool keyword and can only take the values true or false:
Example
bool isCodingFun = true;
bool isFishTasty = false;
cout << isCodingFun;
// Outputs 1 (true)
cout << isFishTasty; // Outputs 0 (false)
Run example »
From the example above, you can read that a true value returns 1, and false returns 0.
However, it is more common to return boolean values from boolean expressions (see below).
Boolean Expression
A Boolean expression is a C++ expression that returns a boolean value: 1 (true) or 0 (false).
You can use a comparison operator, such as the greater than (>) operator to find out if an expression (or a variable) is true:
Example
int x = 10;
int y = 9;
cout << (x > y); // returns 1 (true), because 10 is higher than 9
Run example »
Or even easier:
In the examples below, we use the equal to (==) operator to evaluate an expression:
Example
int x = 10;
cout << (x == 10); // returns 1 (true), because the value
of x is equal to 10
Run example »
Booleans are the basis for all C++ comparisons and conditions.
You will learn more about conditions (if...else) in the next chapter.
