Logical Operators and Short-Circuiting

Beginner11 min read•Updated: 2026-10-22

💡 Logical Operators and Short-Circuiting

Introduction

Logical operators evaluate one or more boolean expressions to make composite decisions. C++ guarantees short-circuit evaluation, a critical feature for writing safe, performant conditions.

🧩 The Three Core Logical Operators

Operator	Name	Logic
`&&`	Logical AND	Returns `true` if both operands evaluate to `true`
`		`	Logical OR	Returns `true` if at least one operand evaluates to `true`
`!`	Logical NOT	Inverts the truth value (`!true` is `false`)

1#include <iostream>
2 
3int main() {
4    bool hasIdProof = true;
5    int age = 19;
6    bool hasParentalConsent = false;
7 
8    // Compound logic:
9    bool isEligibleForAdmission = hasIdProof && (age >= 18 || hasParentalConsent);
10 
11    std::cout << std::boolalpha << "Eligible: " << isEligibleForAdmission << "\n";
12    return 0;
13}

⚡ Short-Circuit Evaluation: Safety & Performance

In C++, boolean expressions are evaluated strictly from left to right:

1
In A && B: If A is false, B is never evaluated, because the result must be false.
2
In A || B: If A is true, B is never evaluated, because the result must be true.

Preventing Division-by-Zero and Null Pointer Crashes:

1#include <iostream>
2 
3int main() {
4    int totalItems = 0;
5    int totalCost = 1000;
6 
7    // ✅ Safe thanks to short-circuiting:
8    // If totalItems == 0, the right-hand division is skipped entirely!
9    if (totalItems > 0 && (totalCost / totalItems) < 100) {
10        std::cout << "Discount applicable\n";
11    } else {
12        std::cout << "Cannot compute average or items are zero\n";
13    }
14 
15    return 0;
16}

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Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)	Math Functions with <cmath> (pow, sqrt, round, ceil, floor)

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Math Functions with <cmath> (pow, sqrt, round, ceil, floor)

Logical Operators and Short-Circuiting

Beginner11 min read•Updated: 2026-10-22

Study Materials

💡 Logical Operators and Short-Circuiting

Introduction

Logical operators evaluate one or more boolean expressions to make composite decisions. C++ guarantees short-circuit evaluation, a critical feature for writing safe, performant conditions.

🧩 The Three Core Logical Operators

Operator	Name	Logic
`&&`	Logical AND	Returns `true` if both operands evaluate to `true`
`		`	Logical OR	Returns `true` if at least one operand evaluates to `true`
`!`	Logical NOT	Inverts the truth value (`!true` is `false`)

1#include <iostream>
2 
3int main() {
4    bool hasIdProof = true;
5    int age = 19;
6    bool hasParentalConsent = false;
7 
8    // Compound logic:
9    bool isEligibleForAdmission = hasIdProof && (age >= 18 || hasParentalConsent);
10 
11    std::cout << std::boolalpha << "Eligible: " << isEligibleForAdmission << "\n";
12    return 0;
13}

⚡ Short-Circuit Evaluation: Safety & Performance

In C++, boolean expressions are evaluated strictly from left to right:

1
In A && B: If A is false, B is never evaluated, because the result must be false.
2
In A || B: If A is true, B is never evaluated, because the result must be true.

Preventing Division-by-Zero and Null Pointer Crashes:

1#include <iostream>
2 
3int main() {
4    int totalItems = 0;
5    int totalCost = 1000;
6 
7    // ✅ Safe thanks to short-circuiting:
8    // If totalItems == 0, the right-hand division is skipped entirely!
9    if (totalItems > 0 && (totalCost / totalItems) < 100) {
10        std::cout << "Discount applicable\n";
11    } else {
12        std::cout << "Cannot compute average or items are zero\n";
13    }
14 
15    return 0;
16}

Next Lesson

Math Functions with <cmath> (pow, sqrt, round, ceil, floor)

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Relational, Equality, and Three-Way Comparison (Spaceship Operator <=>)	Math Functions with <cmath> (pow, sqrt, round, ceil, floor)

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next