Switch statement in C++

Introduction

A switch statement helps you choose between many options easily. It makes your code cleaner when you have many choices based on one value.

When you want to run different code based on a number or character.

When you have many fixed options to check, like days of the week or menu choices.

When you want your code to be easier to read than many if-else statements.

Syntax

C++

switch (expression) {
    case constant1:
        // code to run if expression == constant1
        break;
    case constant2:
        // code to run if expression == constant2
        break;
    // more cases...
    default:
        // code to run if no case matches
        break;
}

The expression is checked once.

Each case compares the expression to a constant value.

Examples

Checks the value of day and runs code for Monday or Tuesday, or default if none match.

C++

switch (day) {
    case 1:
        // Monday
        break;
    case 2:
        // Tuesday
        break;
    default:
        // Other days
        break;
}

Uses a character to decide which message to show based on grade.

C++

char grade = 'B';
switch (grade) {
    case 'A':
        // Excellent
        break;
    case 'B':
        // Good
        break;
    default:
        // Other grades
        break;
}

Sample Program

This program checks the value of number. It prints a message for 1, 2, or 3. If the number is not 1, 2, or 3, it prints a default message.

C++

#include <iostream>

int main() {
    int number = 2;
    switch (number) {
        case 1:
            std::cout << "Number is one\n";
            break;
        case 2:
            std::cout << "Number is two\n";
            break;
        case 3:
            std::cout << "Number is three\n";
            break;
        default:
            std::cout << "Number is something else\n";
            break;
    }
    return 0;
}

Important Notes

Always use break; to stop the switch after a case runs, or all following cases will run too.

The default case is optional but useful for unexpected values.

Switch works best with simple values like integers or characters, not complex types.

Summary

Switch lets you pick code to run based on one value.

Use case for each choice and break; to stop.

Include default to handle unexpected values.

Practice

1. What is the main purpose of a switch statement in C++?

easy

A. To declare a variable

B. To repeat a block of code multiple times

C. To define a function

D. To choose which block of code to run based on a single value

Solution

1. Step 1: Understand the role of switch

   A switch statement checks one value and runs code matching that value.

2. Step 2: Compare with other options

   Repeating code is done by loops, functions define reusable code, and variables store data.

3. Final Answer:

   To choose which block of code to run based on a single value -> Option D

4. Quick Check:

   Switch selects code by value = A [OK]

Hint: Switch picks code based on one value quickly [OK]

Common Mistakes:

• Confusing switch with loops
• Thinking switch defines functions
• Mixing switch with variable declaration

2. Which of the following is the correct syntax to start a switch statement for variable choice?

easy

A. switch(choice) {

B. switch choice {

C. switch choice() {

D. switch(choice);

Solution

1. Step 1: Recall switch syntax

   The switch statement requires parentheses around the variable: switch(variable).

2. Step 2: Check each option

   switch(choice) { uses correct parentheses and opening brace. Others miss parentheses or use wrong punctuation.

3. Final Answer:

   switch(choice) { -> Option A

4. Quick Check:

   Correct switch syntax uses parentheses [OK]

Hint: Switch needs parentheses around variable [OK]

Common Mistakes:

• Omitting parentheses
• Using semicolon instead of brace
• Adding parentheses after variable name

3. What will be the output of this code?

int x = 2;
switch(x) {
  case 1:
    std::cout << "One";
    break;
  case 2:
    std::cout << "Two";
    break;
  default:
    std::cout << "Other";
}

medium

A. One

B. Two

C. Other

D. No output

Solution

1. Step 1: Check the value of x

   The variable x is 2.

2. Step 2: Match case in switch

   The switch matches case 2, so it prints "Two" and then breaks.

3. Final Answer:

   Two -> Option B

4. Quick Check:

   Value 2 matches case 2 = Two [OK]

Hint: Match variable value to case label [OK]

Common Mistakes:

• Forgetting break causes fall-through
• Choosing default when case matches
• Confusing output with case number

4. Identify the error in this switch statement:

int n = 3;
switch(n) {
  case 1:
    std::cout << "One";
  case 2:
    std::cout << "Two";
    break;
  default:
    std::cout << "Default";
}

medium

A. default case must be last

B. Variable n should be a string

C. Missing break after case 1 causes fall-through

D. case labels must be strings

Solution

1. Step 1: Check case 1 block

   There is no break; after case 1, so execution falls through to case 2.

2. Step 2: Understand consequences

   Without break, both "One" and "Two" print if n=1. This is usually unintended.

3. Final Answer:

   Missing break after case 1 causes fall-through -> Option C

4. Quick Check:

   Break prevents fall-through = A [OK]

Hint: Always add break after each case to stop fall-through [OK]

Common Mistakes:

• Forgetting break causes multiple outputs
• Thinking default must be last (it can be anywhere)
• Believing case labels must be strings

5. You want to write a switch statement that prints "Weekend" for cases 6 and 7, and "Weekday" for cases 1 to 5. Which code snippet correctly does this?

hard

A. switch(day) {
case 1: case 2: case 3: case 4: case 5:
std::cout << "Weekday";
break;
case 6: case 7:
std::cout << "Weekend";
break;
default:
std::cout << "Invalid";
}

B. switch(day) {
case 1:
case 2:
case 3:
case 4:
case 5:
std::cout << "Weekend";
break;
case 6:
case 7:
std::cout << "Weekday";
break;
default:
std::cout << "Invalid";
}

C. switch(day) {
case 1:
case 2:
case 3:
case 4:
case 5:
std::cout << "Weekday";
case 6:
case 7:
std::cout << "Weekend";
break;
default:
std::cout << "Invalid";
}

D. switch(day) {
case 1: case 2: case 3: case 4: case 5:
std::cout << "Weekend";
case 6: case 7:
std::cout << "Weekday";
break;
default:
std::cout << "Invalid";
}

Solution

1. Step 1: Group cases for weekdays and weekends

   Cases 1 to 5 print "Weekday"; cases 6 and 7 print "Weekend". Grouping cases with no code between them is correct.

2. Step 2: Check breaks and outputs

   switch(day) { case 1: case 2: case 3: case 4: case 5: std::cout << "Weekday"; break; case 6: case 7: std::cout << "Weekend"; break; default: std::cout << "Invalid"; } groups cases correctly and uses breaks to prevent fall-through. Others mix outputs or miss breaks.

3. Final Answer:

   Option A code correctly prints "Weekday" for 1-5 and "Weekend" for 6-7 -> Option A

4. Quick Check:

   Group cases + breaks = correct switch [OK]

Hint: Group cases without code, add break after each group [OK]

Common Mistakes:

• Missing breaks causing fall-through
• Swapping outputs for cases
• Not grouping cases properly