C++ Booleans

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Very often, in programming, you will need a data type that can only have one of two values, like:

For this, C++ has a bool data type, which can take the values true (1) or false (0).

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Boolean Values

A boolean variable is declared with the bool keyword and can only take the values true or false:

bool isCodingFun = true;
bool isFishTasty = false;
cout << isCodingFun; // Outputs 1 (true)
cout << isFishTasty; // Outputs 0 (false)

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 next page).

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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:

int x = 10;
int y = 9;
cout << (x > y); // returns 1 (true), because 10 is higher than 9

Or even easier:

cout << (10 > 9); // returns 1 (true), because 10 is higher than 9

In the examples below, we use the equal to (==) operator to evaluate an expression:

int x = 10;
cout << (x == 10); // returns 1 (true), because the value of x is equal to 10

cout << (10 == 15); // returns 0 (false), because 10 is not equal to 15

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