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C - Switch



The Switch statement in C language is used to execute one of many code statements. It can be considered as group of If-else statements.

Syntax

switch (expression){
  case 1:
     statement 1;
     break;
  case 2:
     statement 2;
     break;
     ...
     ...
     ...
  case N:
     statement N;
     break;
  default:
     default statement;
} 

The Switch expression is evaluated and matched with the cases. When Case matches, the following block of code is executed.

Flow Diagram:

C Switch

Example:

In the example below, the switch expression is a variable called i with value 2 which is matched against case values. When the case value matches with expression value, the following block of code is executed.

#include <stdio.h>
 
int main (){
  int i = 2;
  switch(i){
    case 1: 
       printf("Red\n");
       break; 
    case 2:
       printf("Blue\n"); 
       break;
    case 3: 
       printf("Green\n");
  }
  return 0;
}

The output of the above code will be:

Blue

default and break statements

Default case and break statement are optional here.

  • Default Case: Default Statement is executed when there is no match between switch expression and test cases.
  • Break Statement: Break statement is used to get out of the Switch statement after a match is found.

Example:

In the example below, the switch expression is a variable called i with value 10 which is matched against case values. As there is no case that matches with value 10, hence default block of code gets executed.

#include <stdio.h>
 
int main (){
  int i = 10;
  switch(i){
    case 1: 
       printf("Red\n");
       break; 
    case 2: 
       printf("Blue\n");
       break;
    case 3: 
       printf("Green\n");
       break;
    default: 
       printf("No match found.\n");
  }
  return 0;
}

The output of the above code will be:

No match found.

Please note that, the default statement can be placed at any position in the switch statement. In such instances, add break statement with default statement.

Example:

Consider the example below, where default statement is placed on the top in a switch statement.

#include <stdio.h>
 
int main (){
  int i = 10;
  switch(i){
    default: 
       printf("No match found.\n");
       break;
    case 1: 
       printf("Red\n");
       break; 
    case 2: 
       printf("Blue\n");
       break;
    case 3: 
       printf("Green\n");
  }
  return 0;
}

The output of the above code will be:

No match found.

Common code blocks

There are instances where same code block is required in multiple cases.

Example:

In the example below, same code block is shared for different switch cases.

#include <stdio.h>
 
int main (){
  int i = 10;
  switch(i){
    case 1: 
       printf("Red\n");
       break; 
    case 2: 
    case 10:
       printf("Blue\n");
       break;
    case 3:
    case 4:
    case 5: 
       printf("Green\n");
  }
  return 0;
}

The output of the above code will be:

Blue

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