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C++ Switch

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What Is a Switch Statement in C++?

In C++, the switch statement is used when you need to make a decision from multiple possible options based on the value of a single variable or expression.
It’s a cleaner and more efficient alternative to using many if...else if statements, especially when you’re comparing the same variable against different constant values.

The switch structure improves code readability and is commonly used in menu-driven programs, grade systems, and user input handling.

Syntax of the Switch Statement

The basic syntax of a switch statement looks like this:

switch (expression) {
    case constant1:
        // code block
        break;

    case constant2:
        // code block
        break;

    default:
        // code block
}

Explanation:

  • expression: The value or variable to be tested.

  • case: Each case represents one possible value of the expression.

  • break: Exits the switch block; without it, execution will “fall through” to the next case.

  • default: Optional, runs if none of the cases match.

Example: Basic Switch Statement

#include <iostream>
using namespace std;

int main() {
    int day = 3;

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

    return 0;
}

Output:

Wednesday

Here, the value of day is 3, so the statement under case 3 executes.

Why Use a Switch Instead of If...Else?

When you have several conditions checking the same variable, a switch statement is shorter and clearer than multiple if...else if statements.
Also, since switch statements use jump tables internally, they can be faster for large, fixed sets of comparisons.

Example Comparison

Using if...else:

if (choice == 1)
    cout << "Start Game";
else if (choice == 2)
    cout << "Load Game";
else if (choice == 3)
    cout << "Exit";
else
    cout << "Invalid Option";

Using switch:

switch (choice) {
    case 1: cout << "Start Game"; break;
    case 2: cout << "Load Game"; break;
    case 3: cout << "Exit"; break;
    default: cout << "Invalid Option";
}

The switch version is more compact and easier to read.

The Role of Break in a Switch

The break statement is crucial in a switch block.
It stops the program from executing the next case unintentionally.
Without break, all statements following a matched case will also execute — a behavior called fall-through.

Example Without Break:

int num = 2;

switch (num) {
    case 1:
        cout << "One";
    case 2:
        cout << "Two";
    case 3:
        cout << "Three";
    default:
        cout << "Default";
}

Output:

TwoThreeDefault

The program executes all cases after case 2 because there’s no break statement.
Always include break unless you intentionally want fall-through logic.

The Default Case in Switch

The default case is optional but recommended.
It executes when no case matches the expression’s value.

Example:

int number = 5;

switch (number) {
    case 1: cout << "One"; break;
    case 2: cout << "Two"; break;
    default: cout << "Not 1 or 2";
}

Output:

Not 1 or 2

You can also place the default case anywhere inside the switch, but it’s best to keep it last for clarity.

Switch with Char or String Values

C++ allows switch expressions to be of integral or enumeration types — this includes int, char, and enum, but not strings.

Example with Char:

#include <iostream>
using namespace std;

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

    switch (grade) {
        case 'A':
            cout << "Excellent!";
            break;
        case 'B':
            cout << "Good job!";
            break;
        case 'C':
            cout << "Needs improvement.";
            break;
        default:
            cout << "Invalid grade.";
    }

    return 0;
}

Output:

Good job!

If you try to use a string in a switch condition, it will cause a compile-time error because switch only supports constant integer or character expressions.

Nested Switch Statements

Just like if statements, switch statements can be nested — one inside another.
However, this should be used carefully to avoid confusion.

Example:

#include <iostream>
using namespace std;

int main() {
    int category = 1;
    int item = 2;

    switch (category) {
        case 1:
            switch (item) {
                case 1: cout << "Category 1 - Item 1"; break;
                case 2: cout << "Category 1 - Item 2"; break;
            }
            break;

        case 2:
            cout << "Category 2";
            break;

        default:
            cout << "Invalid Category";
    }

    return 0;
}

Output:

Category 1 - Item 2

Nested switches are useful when handling multiple levels of selection, such as menu-driven programs.

Common Mistakes with Switch Statements

  1. Forgetting break statements:
    Leads to unintentional fall-through behavior.

  2. Using non-integer types:
    Only integral or enum types are allowed in the switch expression.

  3. Missing default case:
    May cause the program to ignore unmatched values.

  4. Using variables in case labels:
    Case labels must be constant expressions, not variables.

Example: Menu-Driven Program Using Switch

#include <iostream>
using namespace std;

int main() {
    int choice;
    cout << "1. Addition\n2. Subtraction\n3. Multiplication\n4. Division\n";
    cout << "Enter your choice: ";
    cin >> choice;

    int a, b;
    cout << "Enter two numbers: ";
    cin >> a >> b;

    switch (choice) {
        case 1:
            cout << "Result: " << a + b;
            break;
        case 2:
            cout << "Result: " << a - b;
            break;
        case 3:
            cout << "Result: " << a * b;
            break;
        case 4:
            if (b != 0)
                cout << "Result: " << a / b;
            else
                cout << "Division by zero not allowed.";
            break;
        default:
            cout << "Invalid choice!";
    }

    return 0;
}

This example shows how the switch statement can make multi-option programs easy to manage.

Summary of C++ Switch

The switch statement in C++ is a control structure used to execute one code block from many options, depending on the value of an expression.
It’s more organized than a long list of if...else statements, and it improves readability and performance.

Remember:

  • Always use break to prevent fall-through.

  • Use default to handle unexpected input.

  • Only integral or enum types are supported.

Practice Questions

  1. What is the main difference between a switch statement and an if...else if ladder?

  2. Why is the break statement important in a switch block? What happens if you forget it?

  3. Can a switch statement work with floating-point or string values in C++? Why or why not?

  4. What is the role of the default case in a switch structure? Is it mandatory to include it?

  5. Write a C++ program using a switch statement to display the name of the month based on its number (1 for January, 2 for February, etc.).

  6. Create a C++ switch-based menu that performs addition, subtraction, multiplication, and division between two numbers entered by the user.

  7. What is meant by “fall-through” in the context of a switch statement? Provide an example.

  8. Write a program that takes a character input (‘A’, ‘B’, ‘C’, or others) and displays a corresponding message using a switch statement.

  9. Explain the difference between case labels and default in a switch block.

  10. Write a nested switch program to handle two levels of categories: one for “Fruit” and another for specific fruit names.

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