C Switch Statements

Switch-case statement comes under the Selection control statement; there are four types of Control statements

1. Decision-making statements (if, if-else)
2. Selection statements (Switch-case)
3. Iteration statements (for, while, do-while)
4. Jump statements (break, continue, goto)

If we want to write a program with one condition, then we use if-else statements. And if we want to write a program containing many conditions, then we will use an if-else ladder that supports many conditions simultaneously.

Instead of using the if-else ladder, we use the switch statement. In the switch statement, we build many blocks known as cases, and there must be a default case at the end of every switch statement.

• In the switch statement, we pass a value that will check all the case’s values. If that value matches the case value, then that case will be executed. Otherwise, the default case will be executed.
• In the if-else ladder, the conditions are evaluated continuously. But in the switch statement, the expression is evaluated only once.

When the expression value is matched with the case value, then that case statement will be executed until it reaches the break statement in the particular block.

• After every case, we use a break statement to come out of the switch block and stop the execution. The program will not stop execution if we forget to use a break statement in our program.
• If there is no case value matching the expression value, then the default statement will be executed. We will not give a break statement in the default case.
• In the switch statement, all the cases are numbered like case 1, case 2, case 3,………, and case n.

Syntax for switch statement:

Switch ( expression )
{
Case 1: {
		Statement (s);
		break;
	         }
Case 2: {
		Statement (s);
		break;
	        }


Case 3: {
		Statement (s);
		break;
	       }
//we can have any number of case statements in the program
Default: {
		Statement (s);
	         }
}

Example 1:

//simple program for switch-case statement
#include <stdio.h>            //pre-processor standard input and output
#include <conio.h>	//pre-processor clear screen before scanning the value
Int main ()
{
int num;	//declaring integer variable
clrscr();	//clear screen command
printf(“enter the value of num:”);
scanf(“%d”, &num);	//scanning the variable data


Switch(num)	//passing the scanned value in the switch statement
{
Case 1:	//declaring case 1 with executable statements
	printf(“Hi all this is case-1”);
	Break;
Case 2:	//declaring case 2 with executable statements
	printf(“Hello, this is case-2”);
	Break;
Case 3:	//declaring case 3 with executable statements
	printf(“Hello, this is case-3”);
	Break;
Case 4:	//declaring case 4 with executable statements
	printf(“Hello, this is case-4”);
	Break;
Default:	//declaring default case with print statements
	printf(“Invalid choice”);
}
return 0;
}

Output:

Test case 1:

Enter the value of num: 4
Hello, this is case 4.

Explanation:

In the above test case, we have given the number 4, and in the program, we have given case 4 both the numbers are matched. So, case 4 will be executed.

 Test case 2:

Enter the value of num: 8
Invalid choice

Explanation:

In the above test case, we have given the number 8, and in the program, we have not declared any case 8. Here expression value and case value are not matched. So, the default case will be executed.

Example 2:

//program for switch-case statements
#include <stdio.h>            //pre-processor standard input and output
#include <conio.h>	//pre-processor clear screen before scanning the value
Int main ()
{
int n;	//declaring integer variable
clrscr();	//clear screen command
printf(“enter the value of n:”);
scanf(“%d”, &n);	//scanning the variable data


Switch(n)	//passing the scanned value in the switch statement
{
Case 10:	//declaring case 1 with executable statements
{
      Int a;	//declaring integer variable a
      Printf(“enter the a value:”);
      Scanf(“%d”, &a);              //scanning the variable data(a)
      printf(“The division of two numbers is %d”,(n/a));           //printing the result
	Break;
}
Case 20:	//declaring case 2 with executable statements
{	
       Int b;                       //declaring integer variable b
	Printf(“enter the b value:”);
      Scanf(“%d”, &b);                 //scanning the variable data(b)
      printf(“The multiplication of two numbers is %d”,(n*b));    //printing the result
	Break;
}
Case 30:	//declaring case 3 with executable statements
{
	Int a;                    //declaring integer variable a
	Printf(“enter the a value:”);
      Scanf(“%d”, &a);      //scanning the variable data(a)
printf(“The addition of two numbers is %d”,(a+n));           //printing the result
	Break;
}
Case 40:	//declaring case 4 with executable statements
{
	Int b;                                //declaring integer variable b
	Printf(“enter the b value:”);
       Scanf(“%d”, &b);       //scanning the variable data(b)
printf(“The subtraction of two numbers is %d”, (n-b));        //printing the result
	Break;
Default:	//declaring default case with print statements
	printf(“Invalid choice”);
}
return 0;
}

Output:

Test case 1:

Enter the value of n: 40
Enter the b value: 25
The subtraction of two numbers is 15.

Explanation:

We have given the expression value 40, so in the program, there is a case value 40. Both are the same, so case 40 will be executed. And the output will be (40-25) = 15.

Test case 2:

Enter the value of n: 20
Enter the b value: 5
The multiplication of two numbers is 100.

Explanation:

We have given the expression value 20, so the program has a case value matching the expression value. Both are the same, so case 20 will be executed. And the output will be (20*5) = 100.

Test case 3:

Enter the value of n: 10
Enter the a value: 2
The division of the two numbers is 5.

Explanation:

We have given the expression value 10, so the program has a case value matching the expression value. Both are the same, so case 10 will be executed. And the output will be (10/2) = 5.

Test case 4:

Enter the value of n: 30
Enter the a value: 10
The addition of the two numbers is 40.

Explanation:

We have given the expression value 30, so the program has a case value matching the expression value. Both are the same, so case 30 will be executed. And the output will be (30+10) = 40.

Test case 5:

Enter the value of n: 70
Invalid choice.

Explanation:

We gave the expression value 70, so the program doesn’t have a case value matching the expression value. So the out will be “Invalid choice”.