C++Logical OperatorsLogical AND

Logical AND (&&) Operator in C++

In C++, the Logical AND operator (&&) is used to combine two or more conditions. It is commonly used in decision-making statements such as if, while, and for to determine whether multiple conditions are true.

How the Logical AND Works

The syntax is:

condition1 && condition2

This expression evaluates to:

  • true only if both condition1 and condition2 are true.
  • false if at least one of the conditions is false.

Truth Table

condition1condition2Result (condition1 && condition2)
truetruetrue
truefalsefalse
falsetruefalse
falsefalsefalse

Short-Circuit Behavior

C++ evaluates logical expressions from left to right.

In A && B:

  • If A is false, B is not evaluated. This is known as short-circuiting, and it’s an important performance feature and safety mechanism (e.g., preventing division by zero or null dereferencing).

Example 1: Basic Integer Conditions

and_basic_integers.cpp
int a = 10, b = 20;
std::cout << (a > 5 && b > 15);

Explanation

  • a > 5 → true (10 is greater than 5)
  • b > 15 → true (20 is greater than 15)
  • true && true → true

Output: 1 (since true is internally represented as 1)

Example 2: One Condition Fails

and_one_false.cpp
int x = 10, y = 5;
std::cout << (x > 15 && y < 10);

Explanation

  • x > 15 → false (10 is not greater than 15)
  • y < 10 → true
  • false && true → false

Output: 0

Example 3: Using in an if Statement

and_if_statement.cpp
int age = 22;
int marks = 80;
 
if (age >= 18 && marks >= 60) {
    std::cout << "Eligible for scholarship";
}

Explanation

  • age >= 18 → true
  • marks >= 60 → true
  • Since both conditions are true, the message is printed.

Example 4: Short-Circuit Prevention

and_short_circuit.cpp
int a = 0, b = 100;
 
if (a != 0 && (b / a) > 1) {
    std::cout << "Safe to divide";
}

Explanation

  • a != 0 → false
  • Because the first condition is false, the second (b / a) is not evaluated, preventing a division-by-zero error.

Example 5: With Booleans

and_booleans.cpp
bool a = true;
bool b = false;
 
std::cout << (a && b);  // Output: 0

Explanation

  • true && false → false
  • Output: 0

Example 6: With Characters

and_characters.cpp
char grade = 'A';
 
std::cout << (grade == 'A' && grade != 'F');  // Output: 1

Explanation

  • grade == 'A' → true
  • grade != 'F' → true
  • true && true → true → Output: 1

Example 7: With Strings

and_strings.cpp
std::string username = "admin";
std::string password = "1234";
 
if (username == "admin" && password == "1234") {
    std::cout << "Access Granted";
}

Explanation

  • Both string comparisons return true
  • Since both are true, the message is printed

Example 8: Practical Range Check

and_range_check.cpp
int marks = 75;
std::cout << (marks >= 0 && marks <= 100);

Explanation

  • marks >= 0 → true
  • marks <= 100 → true
  • Combined: true && true → 1

Example 9: Logical AND in Loops

and_loop_example.cpp
int i = 0;
while (i < 10 && i >= 0) {
    std::cout << i << " ";
    i++;
}

Explanation

  • The loop runs while i is less than 10 and greater than or equal to 0.
  • Both conditions must hold true for each iteration.

Output: 0 1 2 3 4 5 6 7 8 9

Key Takeaways

  • The && operator is used when all conditions must be true.
  • Evaluation stops early if the first condition is false (short-circuiting).
  • It helps write safe and readable conditional logic in if, while, and other control structures.
  • Works with all types that evaluate to Boolean values, including integers, characters, and strings.
Less than or EqualLogical OR