Switch case statement

Switch case is useful where we have to select a choice between n numbers of alternatives. It is like if-else-if ladder statement.

switch (variable)
{
    case value1:
        statement 1;
        statement 2;
    break;
	
    case value2:
        statement 1;
        statement 2;
    break;
	
    default:
        statement 1;
        statement 2;
}

Rules for writting switch statement in C language:

The switch expression and case value must be of integer or character type.
The break statement in switch case is not must, it is optional. If there is no break statement found, all the cases will be executed after matching the case value. It is known as fall through state of C switch statement.
When user gives some choice the switch statement takes the control to the specified case. If no such case exists, then control goes to default.

Valid/In-Valid Switch syntax:

Some valid switch syntax:

int x=5, y=10;
switch(x)
switch(x>y)
switch(x+y-2)

Some invalid switch syntax:

float f=10.0f, g=20.2f ;
switch(f)
switch(f+g)
switch(f+2.5)

Some valid case syntax:

case 3:
case 1+2:
case 'a':
case 'a'>'b':

Some invalid case syntax:

case 2.5:
case x:
case x+2:
case 1,2,3:

Example: Switch

Example 1: WAP to explain the use of fall through statement in switch case. 206

void main()
{
   int n;
   clrscr();
   printf("Enter number: (1-5) ");
   scanf("%d",&n);
   switch(n)
   {
      case 1:
         printf("\nNumber is equal to 1.");
      case 2:
         printf("\nNumber is equal to 2.");
      case 3:
         printf("\nNumber is equal to 3.");
      case 4:
         printf("\nNumber is equal to 4.");
      case 5:
         printf("\nNumber is equal to 5.");
      default:
         printf("\nInvalid Input");
   }
   getch();
}

Output 1:
Enter number: 4
Number is equal to 4.
Number is equal to 5.

Output 2:
Enter number: 1
Number is equal to 1.
Number is equal to 2.
Number is equal to 3.
Number is equal to 4.
Number is equal to 5.

Above program is an example of fall through statement. Re-write the above program and apply break keyword at end of each case.

switch(n)
{
   case 1:
      printf("\nNumber is equal to 1.");
   break;
   case 2:
      printf("\nNumber is equal to 2.");
   break;
   case 3:
      printf("\nNumber is equal to 3.");
   break;
   case 4:
      printf("\nNumber is equal to 4.");
   break;
   case 5:
      printf("\nNumber is equal to 5.");
   break;
}

Output 1:
Enter number: 4
Number is equal to 4.

Output 2:
Enter number: 1
Number is equal to 1.

How to use switch statement