Logical Operators

You can use logical operators AND (&&), OR (||) and NOT (!) to evaluate multiple conditions simultaneously.

AND (&&) returns true only if both conditions are true. For example, checking if an account balance is sufficient and the withdrawal amount is positive;
OR (||) returns true if at least one condition is true. For example, checking if a balance is sufficient or the user has a credit card;
NOT (!) negates a condition, turning true into false and vice versa. For example, checking if an account is not locked.

Imagine you need to create conditions for user authentication. Let’s explore some scenarios.

Condition	Authorization Status	State of Password, Login, Phone Call, and Internet
Password AND login are correct	Authorized (`true`)	Password: `true` Login: `true` Phone Call: N/A Internet: N/A
Password AND login are correct, OR with a phone call identification	Authorized (`true`)	Password: `true` Login: `false` Phone Call: `true` Internet: N/A
There is NO internet	Not Authorized (`false`)	Password: N/A Login: N/A Phone Call: N/A Internet: `false`

logical_and

logical_or

logical_not


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#include <iostream>

int main()
{
    // Using AND (&&) operator for password and login
    //     Login is correct = `true`
    //     Password is correct = `true`
    std::cout << "User authorized (password AND login correct)" 
              << (true && true) << std::endl;
}

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 4