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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)
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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
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Or even easier:

Example

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

cout << (10 == 15);  // returns 0 (false), because 10 is not equal to 15
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Booleans are the basis for all C++ comparisons and conditions.

You will learn more about conditions (if...else) in the next chapter.