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Conditional Statements

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Conditional statements are fundamental in programming as they allow you to make decisions based on certain conditions. In C++, the primary conditional statements are if, else if, and else. These statements help control the flow of the program by executing different blocks of code based on specific conditions.

Key Concepts

  1. If Statement: Executes a block of code if a specified condition is true.
  2. Else Statement: Executes a block of code if the same condition is false.
  3. Else If Statement: Specifies a new condition to test if the first condition is false.
  4. Nested If Statements: An if or else if statement inside another if or else if statement.
  5. Logical Operators: Used to combine multiple conditions (&&, ||, !).

Syntax and Structure

If Statement

if (condition) {
    // code to be executed if condition is true
}

Else Statement

if (condition) {
    // code to be executed if condition is true
} else {
    // code to be executed if condition is false
}

Else If Statement

if (condition1) {
    // code to be executed if condition1 is true
} else if (condition2) {
    // code to be executed if condition2 is true
} else {
    // code to be executed if both conditions are false
}

Nested If Statements

if (condition1) {
    if (condition2) {
        // code to be executed if both condition1 and condition2 are true
    }
}

Practical Examples

Example 1: Basic If Statement

#include <iostream>
using namespace std;

int main() {
    int number = 10;

    if (number > 5) {
        cout << "The number is greater than 5." << endl;
    }

    return 0;
}

Explanation: This program checks if the variable number is greater than 5. Since number is 10, the condition is true, and the message "The number is greater than 5." is printed.

Example 2: If-Else Statement

#include <iostream>
using namespace std;

int main() {
    int number = 3;

    if (number > 5) {
        cout << "The number is greater than 5." << endl;
    } else {
        cout << "The number is not greater than 5." << endl;
    }

    return 0;
}

Explanation: This program checks if the variable number is greater than 5. Since number is 3, the condition is false, and the message "The number is not greater than 5." is printed.

Example 3: If-Else If-Else Statement

#include <iostream>
using namespace std;

int main() {
    int number = 7;

    if (number > 10) {
        cout << "The number is greater than 10." << endl;
    } else if (number > 5) {
        cout << "The number is greater than 5 but less than or equal to 10." << endl;
    } else {
        cout << "The number is 5 or less." << endl;
    }

    return 0;
}

Explanation: This program checks multiple conditions. Since number is 7, the first condition is false, but the second condition is true, so the message "The number is greater than 5 but less than or equal to 10." is printed.

Example 4: Nested If Statements

#include <iostream>
using namespace std;

int main() {
    int number = 15;

    if (number > 10) {
        if (number < 20) {
            cout << "The number is between 10 and 20." << endl;
        }
    }

    return 0;
}

Explanation: This program uses nested if statements to check if number is between 10 and 20. Since number is 15, both conditions are true, and the message "The number is between 10 and 20." is printed.

Exercises

Exercise 1: Simple If Statement

Task: Write a program that checks if a number is positive.

#include <iostream>
using namespace std;

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

    // Your code here

    return 0;
}

Solution:

#include <iostream>
using namespace std;

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

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

    return 0;
}

Exercise 2: If-Else Statement

Task: Write a program that checks if a number is even or odd.

#include <iostream>
using namespace std;

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

    // Your code here

    return 0;
}

Solution:

#include <iostream>
using namespace std;

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

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

    return 0;
}

Exercise 3: If-Else If-Else Statement

Task: Write a program that checks if a number is negative, zero, or positive.

#include <iostream>
using namespace std;

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

    // Your code here

    return 0;
}

Solution:

#include <iostream>
using namespace std;

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

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

    return 0;
}

Common Mistakes and Tips

  • Common Mistake: Forgetting to use curly braces {} for blocks of code.

    • Tip: Always use curly braces, even for single statements, to avoid errors and improve readability.

  • Common Mistake: Using = instead of == in conditions.

    • Tip: Remember that = is for assignment, while == is for comparison.

  • Common Mistake: Not considering all possible conditions.

    • Tip: Ensure that your conditions cover all possible scenarios to avoid unexpected behavior.

Conclusion

In this section, you learned about conditional statements in C++, including if, else if, and else. You also practiced writing programs that use these statements to make decisions based on conditions. Understanding and using conditional statements effectively is crucial for controlling the flow of your programs. In the next section, we will explore loops, which allow you to execute a block of code multiple times.

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