C++ Boolean Expressions
Boolean Expression
A Boolean expression returns a boolean value that is either 1 (true) or 0
(false).
This is useful to build logic, and find answers.
You can use a comparison operator, such as the greater than (>) operator,
to find out if an expression (or variable) is true or false:
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:
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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Real Life Example
Let's think of a "real life example" where we need to find out if a person is old enough to vote.
In the example below, we use the >= comparison operator to find out if the age (25) is
greater than OR equal to the voting age limit, which is set to 18:
Example
int myAge = 25;
int votingAge = 18;
cout << (myAge >= votingAge);
// returns 1 (true), meaning 25 year olds are allowed to vote!
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Cool, right? An even better approach (since we are on a roll now), would be to wrap the code above in an
if...else statement, so we can perform
different actions depending on the result:
Example
Output "Old enough to vote!" if myAge is greater than or equal to 18. Otherwise output "Not old enough to vote.":
int myAge = 25;
int votingAge = 18;
if (myAge >= votingAge) {
cout << "Old enough to vote!";
} else {
cout << "Not old enough to vote.";
}
// Outputs: Old enough to vote!
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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.