if Statement in C++

 

The if statement in C++ is used for decision-making. It allows the program to execute a block of code only if a specified condition is true.

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1️⃣ Basic if Statement

#include <iostream>
using namespace std;

int main() {
    int num;
    cout << "Enter a number: ";
    cin >> num;

    if (num > 0) {  // Condition
        cout << "The number is positive." << endl;
    }

    cout << "Program ended." << endl;
    return 0;
}

Output (if input is 5):

The number is positive.
Program ended.

📌 If the condition num > 0 is false, the cout statement inside if will be skipped.

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2️⃣ if-else Statement

The if-else statement provides two possible execution paths:

• if block executes when the condition is true.
• else block executes when the condition is false.

#include <iostream>
using namespace std;

int main() {
    int num;
    cout << "Enter a number: ";
    cin >> num;

    if (num % 2 == 0) {
        cout << "The number is even." << endl;
    } else {
        cout << "The number is odd." << endl;
    }

    return 0;
}

Output (if input is 7):

The number is odd.

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3️⃣ if-else if-else Ladder

When multiple conditions need to be checked, we use if-else if-else.

#include <iostream>
using namespace std;

int main() {
    int marks;
    cout << "Enter your marks: ";
    cin >> marks;

    if (marks >= 90) {
        cout << "Grade: A" << endl;
    } else if (marks >= 75) {
        cout << "Grade: B" << endl;
    } else if (marks >= 50) {
        cout << "Grade: C" << endl;
    } else {
        cout << "Grade: F (Fail)" << endl;
    }

    return 0;
}

Output (if input is 80):

Grade: B

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4️⃣ Nested if Statements

You can place an if statement inside another if statement, called nested if.

#include <iostream>
using namespace std;

int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;

    if (age >= 18) {
        if (age >= 60) {
            cout << "You are a senior citizen." << endl;
        } else {
            cout << "You are an adult." << endl;
        }
    } else {
        cout << "You are a minor." << endl;
    }

    return 0;
}

Output (if input is 65):

You are a senior citizen.

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5️⃣ Using if with Logical Operators

C++ supports logical operators to combine multiple conditions:

• && (AND) → Both conditions must be true.
• || (OR) → At least one condition must be true.
• ! (NOT) → Reverses the condition.

#include <iostream>
using namespace std;

int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;

    if (age >= 18 && age <= 60) {  // Both conditions must be true
        cout << "You are eligible to work." << endl;
    } else {
        cout << "You are either too young or retired." << endl;
    }

    return 0;
}

Output (if input is 25):

You are eligible to work.

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6️⃣ Using if with Ternary Operator (? :)

A compact alternative to if-else is the ternary operator (? :).

#include <iostream>
using namespace std;

int main() {
    int num;
    cout << "Enter a number: ";
    cin >> num;

    string result = (num % 2 == 0) ? "Even" : "Odd";  // Ternary operator
    cout << "The number is " << result << "." << endl;

    return 0;
}

Output (if input is 9):

The number is Odd.

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Conclusion

• Use if for single conditions.
• Use if-else for two-way decision making.
• Use if-else if-else for multiple conditions.
• Use nested if for more complex logic.
• Use logical operators (&&, ||, !) to combine conditions.
• Use ternary operator (? :) for short conditional expressions.

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