C++ Logical Operators

Logical operators are symbols that allow you to combine or modify conditions to make logical evaluations. They are used to perform logical operations on boolean values (true or false).

In C++, there are three logical operators:

1. Logical AND Operator ( && )

The C++ logical AND operator (&&) is a binary operator that returns true if both of its operands are true. Otherwise, it returns false. Here's the truth table for the AND operator:

Note: In C++, logical operators return a boolean value (true or false). Internally, true is typically represented as 1 and false as 0.

Syntax

expression1 && expression2

Example

#include <iostream>
using namespace std;

int main() {
    int age = 25;
    bool isStudent = true;

    // Using AND operator in if condition
    if (age > 18 && isStudent) {
        cout << "Student";
    }
    else {
        cout << "Not Student";
    }
	return 0;
}

Student

Explanation: In the above code, we have used AND operator in the if condition to check whether the age is greater than 18 and the person is a student. If both conditions are true, the message "Student" will be printed. Otherwise, the else statement is executed.

2. Logical OR Operator ( || )

The C++ logical OR operator ( || ) is a binary operator that returns true if at least one of its operands is true. It returns false only when both operands are false. Here's the truth table for the OR operator:

Syntax

expression1 || expression2

Example

#include <iostream>
using namespace std;

int main() {

    int n = 7;

    // using logical or for conditional statement
    if (n <= 0 || n >= 10) {
        cout << "n is not in range [0, 10]";
    }
    else {
        cout << "n is in range [0, 10]";
    }

    return 0;
}

n is in range [0, 10]

Explanation: In the above code, the condition n <= 0 || n >= 10 checks whether the number is either less than equal to 0 or greater than equal to 10. If either of these conditions is true, the message "The number is outside the range of 0 to 10." will be printed otherwise else statement is printed.

3. Logical NOT Operator ( ! )

The C++ logical NOT operator ( ! ) is a unary operator that is used to negate the value of a condition. It returns true if the condition is false, and false if the condition is true. Here's the truth table for the NOT operator:

Syntax

! expression

Example

#include <iostream>
using namespace std;

int main() {

    bool isLoggedIn = false;

    // using logical not operator
    if (!isLoggedIn) {
        cout << "Please log in.";
    }
    else {
        cout << "Welcome to GeeksforGeeks!";
    }

    return 0;
}

Please log in.

Explanation: In the above code, the condition '!isLoggedIn' checks whether the user is not logged in. If the condition is true (i.e., the user is not logged in), the message "Please log in." will be displayed otherwise else statement will be printed.