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Switch Case

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In this section, we will explore the switch statement in C++, which is a control structure used to handle multiple conditions more efficiently than a series of if-else statements. The switch statement is particularly useful when you have a variable that can take on a limited set of values and you want to execute different code based on the value of that variable.

Key Concepts

  1. Syntax of Switch Case
  2. How Switch Case Works
  3. Using Break and Default
  4. Practical Examples
  5. Common Mistakes
  6. Exercises

  1. Syntax of Switch Case

The basic syntax of a switch statement in C++ is as follows:

switch (expression) {
    case constant1:
        // code to be executed if expression equals constant1
        break;
    case constant2:
        // code to be executed if expression equals constant2
        break;
    // you can have any number of case statements
    default:
        // code to be executed if expression doesn't match any case
}

  1. How Switch Case Works

  • The expression inside the switch statement is evaluated once.
  • The value of the expression is compared with the values of each case.
  • If there is a match, the corresponding block of code is executed.
  • The break statement is used to terminate a case and exit the switch statement.
  • If no case matches, the default block is executed (if it is present).

  1. Using Break and Default

  • Break Statement: The break statement is crucial in a switch case to prevent "fall-through," where multiple cases are executed. Without break, the program continues to execute the subsequent cases until it encounters a break or the end of the switch statement.
  • Default Case: The default case is optional but recommended. It handles any values that do not match any of the specified cases.

  1. Practical Examples

Example 1: Basic Switch Case

#include <iostream>
using namespace std;

int main() {
    int day = 3;

    switch (day) {
        case 1:
            cout << "Monday" << endl;
            break;
        case 2:
            cout << "Tuesday" << endl;
            break;
        case 3:
            cout << "Wednesday" << endl;
            break;
        case 4:
            cout << "Thursday" << endl;
            break;
        case 5:
            cout << "Friday" << endl;
            break;
        case 6:
            cout << "Saturday" << endl;
            break;
        case 7:
            cout << "Sunday" << endl;
            break;
        default:
            cout << "Invalid day" << endl;
    }

    return 0;
}

Example 2: Switch Case Without Break

#include <iostream>
using namespace std;

int main() {
    int grade = 'B';

    switch (grade) {
        case 'A':
            cout << "Excellent!" << endl;
        case 'B':
            cout << "Well done" << endl;
        case 'C':
            cout << "Good" << endl;
        case 'D':
            cout << "You passed" << endl;
        case 'F':
            cout << "Better try again" << endl;
        default:
            cout << "Invalid grade" << endl;
    }

    return 0;
}

Explanation: In this example, since there are no break statements, all the cases after the matched case will be executed, leading to a fall-through.

  1. Common Mistakes

  • Forgetting the Break Statement: This can lead to unintended fall-through behavior.
  • Using Non-Constant Values in Case Labels: Case labels must be constant expressions.
  • Overlooking the Default Case: Always include a default case to handle unexpected values.

  1. Exercises

Exercise 1: Simple Calculator

Write a program that takes two integers and a character (+, -, *, /) as input and performs the corresponding arithmetic operation using a switch statement.

Solution:

#include <iostream>
using namespace std;

int main() {
    int num1, num2;
    char op;

    cout << "Enter two numbers: ";
    cin >> num1 >> num2;
    cout << "Enter an operator (+, -, *, /): ";
    cin >> op;

    switch (op) {
        case '+':
            cout << "Result: " << num1 + num2 << endl;
            break;
        case '-':
            cout << "Result: " << num1 - num2 << endl;
            break;
        case '*':
            cout << "Result: " << num1 * num2 << endl;
            break;
        case '/':
            if (num2 != 0)
                cout << "Result: " << num1 / num2 << endl;
            else
                cout << "Error: Division by zero" << endl;
            break;
        default:
            cout << "Invalid operator" << endl;
    }

    return 0;
}

Exercise 2: Grade Evaluation

Write a program that takes a character grade (A, B, C, D, F) as input and prints the corresponding message using a switch statement.

Solution:

#include <iostream>
using namespace std;

int main() {
    char grade;

    cout << "Enter your grade (A, B, C, D, F): ";
    cin >> grade;

    switch (grade) {
        case 'A':
            cout << "Excellent!" << endl;
            break;
        case 'B':
            cout << "Well done" << endl;
            break;
        case 'C':
            cout << "Good" << endl;
            break;
        case 'D':
            cout << "You passed" << endl;
            break;
        case 'F':
            cout << "Better try again" << endl;
            break;
        default:
            cout << "Invalid grade" << endl;
    }

    return 0;
}

Conclusion

In this section, we have learned about the switch statement in C++, its syntax, and how it works. We also covered the importance of the break and default statements and provided practical examples and exercises to reinforce the concepts. Understanding the switch statement will help you write more efficient and readable code when dealing with multiple conditions. In the next section, we will delve into the break and continue statements in more detail.

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