switch Statement

Learn about the switch statement in C++.

We'll cover the following

In this lesson, we’ll look at the switch statement which is another conditional statement.

The switch statement (syntax)

The switch statement is the extended form of if-else statement, but with a slight change: in if-else, we use a condition which, if false, executes the block of statements inside the else part. In the switch statement, however, we match an expression against several values for equality. These values are called cases. When the expression’s value matches with a case (integer or a character value), only then do the case’s statement(s) get executed.

The switch statment works with characters and integers only.

When no case is matched, the default statement (if there is one) is executed. It is not compulsory to have a default statement, but it is a good programming practice to have one.

The syntax for the switch statement is:

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switch(expression)
{
  case constant1:
         statement
         break;
  case constant2:
         statement
         break;
  case constant3:
         statement
         break;
  .
  .
  .
  default:
        statement
}

The default statement can be anywhere in the switch statement. If no case is matched, the default statement will still be executed.

How switch works?

Look at the animation below to understand how the switch statement works.

In the illustration above, suppose some expression evaluates to the constant case c3. The control then directly goes to the matched case c3. Then the statement of c3 executes until a break statement is found.

The break statement stops the processing of the particular case inside the switch statement and passes the control to the statement after the switch statement.

Note that the break statement can be used inside a loop as well.

  • Whenever the break statement is executed inside a loop, the loop is immediately terminated (no instruction after the break statement within that loop block will be executed), and the control jumps to the next instruction following the loop. Notice if there is a nested loop and the break is inside the second nested loop, then only the inner (second) loop will be terminated.

Let’s look at a code example now that uses the switch statement to calculate grades based on the marks entered by the user.

We want to determine what grade the candidate would get. A candidate is considered to have passed if they score more than 50% on the test. They get a “C” if they score 50%, and “D” or “F” if they score less than 50%.

//example of switch statement
#include<iostream>
using namespace std;

int main()
{
  int marks;
  cout << "The marks: ";
  cin >> marks;

  switch(marks / 10)
  {
    case 10:
    case 9:
    {
      cout << "A+" << endl;
      break;
    } 

    case 8:
    {
      cout << "A" << endl;
      break;
    } 
    
    case 7:
    {
      cout << "B+" << endl;
      break;
    }   

    case 6:
    {
      cout << "B" << endl;
      break;
    } 

    case 5:
    {
      cout << "C" << endl;
      break;
    }
    
    case 4:
    {
      cout << "D" << endl;
      break;
    } 

    case 3:
      cout << "The ";
    case 2:
      cout << "grade "; 
    case 1:
      cout << "is: ";
    case 0:
    {
      cout << "F" << endl;
      break;
    } 
  }

  return 0;
}
Example of a switch statement

Run the code above with different numbers including 95, 100, 109, and 7 as inputs.

We can execute multiple cases as well, as can be seen in lines 13–14 and lines 50–56.

When a case label matches with the evaluated expression and there are multiple case labels without a break statement in between, those case labels are also executed until a break statement is found. For example, if we enter 30 marks as input in the code editor above, we’ll get the output The grade is: F. This shows that once case 3 matches, the case labels 2, 1, and 0 are also executed until the break statement is found.

Solve the quiz below to identify the issues with our code above.

1

Enter 75 marks in the code above and see which grade gets printed.

A)

A

B)

B+

Question 1 of 40 attempted

If you’ve answered the quiz questions above, you know exactly what the issue is with our code. We need to modify our code so that the input entered is valid and within range (0 to 100).

So our if condition would be if(marks > 0 && marks <= 100) and our else condition would be cout << "Invalid input" << endl;.

Use the if-else statement to solve this issue in the code editor below. Then try running the code again with inputs 105 and -105 respectively.

//example of if else statement(variant 2)
#include<iostream>
using namespace std;

int main()
{
    int marks;
    cout << "The marks: ";
    cin >> marks;

  // Add "if" condition here
  {
    switch(marks / 10)
    {
      case 10:
      case 9:
      {
        cout << "A+" << endl;
        break;
      } 

      case 8:
      {
        cout << "A" << endl;
        break;
      } 
      
      case 7:
      {
        cout << "B+" << endl;
        break;
      }   

      case 6:
      {
        cout << "B" << endl;
        break;
      } 

      case 5:
      {
        cout << "C" << endl;
        break;
      }
      
      case 4:
      {
        cout << "D" << endl;
        break;
      } 

    case 3:
      cout << "The ";
    case 2:
      cout << "grade "; 
    case 1:
      cout << "is: ";
    case 0:
      {
        cout << "F" << endl;
        break;
      }
    }
  }  
  // Add "else" here
    
  return 0;
}
Example of switch statement (exercise)

Click the “Show Solution” button below to view the solution.