If Else Statement In C++

Introduction

if-else statement in C++ are fundamental control structures used to make decisions and execute different blocks of code based on certain conditions. These statements allow the program to choose a path of execution depending on whether a condition evaluates to true or false.

Basic Structure of If Statement

The simplest form of an if statement checks a condition and executes a block of code if the condition is true:

if (condition) {
    // Code to execute if condition is true
}

Adding an Else Clause

An else clause can be added to execute a block of code when the if condition is false:

if(boolean_expression) {
   // statement(s) will execute if the boolean expression is true
} else {
  // statement(s) will execute if the boolean expression is false
}

Using Else If-else for Multiple Conditions

To handle multiple conditions, you can use the else if statement. This allows you to test additional conditions if the initial if condition is false:

if (condition1) {
    // Code to execute if condition1 is true
} else if (condition2) {
    // Code to execute if condition1 is false and condition2 is true
} else {
    // Code to execute if both condition1 and condition2 are false
}

How If-else Statements Work

• Evaluation of Conditions: The if statement evaluates the specified condition. If the condition is true, the code block within the if statement executes. If the condition is false, the program skips to the else if or else part, if available.
• Sequential Checks: In an if-else if-else chain, each condition is checked in sequence. The first condition that evaluates to true has its associated block executed, and the remaining conditions are skipped.
• Default Action: The else clause serves as a default action that executes when none of the preceding conditions are true.

Flow chart of If else Statement

Real World Example of If else statement

Scenario: Calculating Shipping Cost Based on Package Weight

In a shipping service, the cost might be determined as follows:

• Free shipping for packages weighing 5 kg or less.
• $10 shipping for packages weighing more than 5 kg but less than or equal to 20 kg.
• $25 shipping for packages weighing more than 20 kg.

C++ Code Example

#include <iostream>
using namespace std;
int main() {
    double weight;
    cout << "Enter the package weight in kg: ";
    cin >> weight;

    double shippingCost;

    if (weight <= 5) {
        shippingCost = 0.0;
    } else if (weight <= 20) {
        shippingCost = 10.0;
    } else {
        shippingCost = 25.0;
    }

    cout << "The shipping cost is: $" << shippingCost << endl;

    return 0;
}

Explanation

1. Input Package Weight: The program prompts the user to enter the weight of the package.
2. Determine Shipping Cost: Using if-else statements, the program determines the shipping cost based on the weight:
   • Free shipping if the weight is 5 kg or less.
   • $10 if the weight is more than 5 kg but less than or equal to 20 kg.
   • $25 if the weight is more than 20 kg.
3. Output the Shipping Cost: The program outputs the calculated shipping cost.

Example 1

Enter the package weight in kg: 3
The shipping cost is: $0

Example 2

Enter the package weight in kg: 15
The shipping cost is: $10

Example 3

Enter the package weight in kg: 25
The shipping cost is: $25

This example shows how if-else statements can be used to make decisions based on conditions and execute different actions accordingly.

Examples of If else statement

1. Checking if a number is positive, negative, or zero

#include <iostream>
using namespace std;

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

    if (num > 0) {
        cout << "The number is positive." << endl;
    } else if (num < 0) {
        cout << "The number is negative." << endl;
    } else {
        cout << "The number is zero." << endl;
    }

    return 0;
}

2.Determining if a number is even or odd

#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;
}

3.Checking eligibility for voting based on age

#include <iostream>
using namespace std;

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

    if (age >= 18) {
        cout << "You are eligible to vote." << endl;
    } else {
        cout << "You are not eligible to vote yet." << endl;
    }

    return 0;
}

4.Determining the largest of three numbers

#include <iostream>
using namespace std;

int main() {
    int num1, num2, num3;
    cout << "Enter three numbers: ";
    cin >> num1 >> num2 >> num3;

    if (num1 >= num2 && num1 >= num3) {
        cout << "The largest number is: " << num1 << endl;
    } else if (num2 >= num1 && num2 >= num3) {
        cout << "The largest number is: " << num2 << endl;
    } else {
        cout << "The largest number is: " << num3 << endl;
    }

    return 0;
}

Conclusion

In conclusion, the if-else statement in C++ is a fundamental control structure that allows for conditional execution of code based on certain conditions. It provides a way to make decisions within a program, allowing for branching behavior based on the evaluation of expressions.

Key points about if-else statements include:

1. Syntax: The syntax of the if-else statement consists of the if keyword followed by a condition in parentheses, followed by a block of code to be executed if the condition is true. Optionally, an else block can follow, containing code to be executed if the condition is false.
2. Condition Evaluation: The condition within the if statement is evaluated, and if it results in a true value, the code within the corresponding block is executed. If the condition is false, and there is an else block, the code within the else block is executed.
3. Nested if-else: if-else statements can be nested within each other to handle more complex decision-making scenarios.
4. Chaining if-else: Multiple if-else statements can be chained together using else if to handle multiple possible conditions.
5. Default Behavior: It’s important to consider providing default behavior or handling unexpected cases with else or else if clauses to ensure the program behaves as expected in all scenarios.
6. Code Readability: Proper indentation and formatting enhance the readability of if-else statements, making the code easier to understand and maintain.

Overall, if-else statements are essential for implementing conditional logic in C++ programs, enabling developers to create dynamic and responsive applications that can adapt their behavior based on different input conditions.

Frequently Asked Question