C++ Logical Operators

Logical operators in C++ are used to perform logical operations on boolean expressions or values that can be evaluated as true or false. These operators are essential for creating complex conditional statements, controlling program flow, and implementing decision-making logic in applications. There are 3 logical operators in C++:

• Logical AND (&&)
• Logical OR (||)
• Logical NOT (!)

Logical AND (&&)

The logical AND operator && returns true only when both operands are true. It uses short-circuit evaluation, meaning if the first operand is false, the second operand is not evaluated.

Syntax of &&

expression1 && expression2

Here:

• expression1 and expression2 are boolean expressions or values that evaluate to true or false

Example of Logical AND (&&) Operator

#include <iostream>
using namespace std;

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

  // Check if person can drive
  if (age >= 18 && hasLicense) {
    cout << "Person can drive legally." << endl;
  } else {
    cout << "Person cannot drive legally." << endl;
  }

  return 0;
}

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The output of this code is:

Person can drive legally.

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Logical OR (||)

The logical OR operator || returns true if at least one of the operands is true. It also uses short-circuit evaluation, meaning if the first operand is true, the second operand is not evaluated.

Syntax of ||

expression1 || expression2

Example of Logical OR (||) Operator

#include <iostream>
using namespace std;

int main() {
  int day = 6; // Saturday
  bool isHoliday = false;

  // Check if it's a weekend or holiday
  if (day == 6 || day == 7 || isHoliday) {
    cout << "No work today!" << endl;
  } else {
    cout << "Work day." << endl;
  }

  return 0;
}

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The output of this code is:

No work today!

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Logical NOT (!)

The logical NOT operator ! reverses the boolean value of its operand. If the operand is true, it returns false, and vice versa.

Syntax of !

!expression1

Example of Logical NOT (!) Operator

#include <iostream>
using namespace std;

int main() {
  bool isRaining = false;

  if (!isRaining) {
    cout << "Perfect weather for a walk!" << endl;
  } else {
    cout << "Better stay inside." << endl;
  }

  return 0;
}

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The output of this code is:

Perfect weather for a walk!

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Codebyte Example

The following Codebyte demonstrates how logical operators are used in a real-world scenario such as verifying login credentials:

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The following table summarizes the three logical operators in C++: