C Tutorial/Statement/Switch statement

break statement stops evaluating any further case statements.

<source lang="cpp">#include <stdio.h> main(){

 int iResponse = 0;
 printf("\nPlease select a category (1-4): ");
 scanf("%d", &iResponse);
 switch (iResponse) {
   case 1:
     printf("\nYou selected 1\n");
     break;
   case 2:
     printf("You selected 2\n");
     break;
   case 3:
     printf("You selected 3\n");
     break;
   case 4:
     printf("You selected 4\n");
     break;
 }

}</source>

Please select a category (1-4): 2
      You selected 2

Confused if statement

<source lang="cpp">#include <stdio.h>

1. include <stdbool.h>

int main(void) {

 int age = 24;            
 int college = 1;        
 int subject = 2;        
 bool interview = false; 

 if((age>25 && subject==1) && (college==3 || college==1))
   interview = true;
 if(college==2 &&subject ==1)
   interview = true;
 if(college==1 && subject==2 && !(age>28))
   interview = true;
 if(college==2 && (subject==2 || subject==3) && age>25)
   interview = true;
 if(interview)
   printf("\n\nGive "em an interview");
 else
   printf("\n\nReject "em");
 return 0;

}</source>

Give "em an interview

In the absence of a break statement, all statements that are followed by matched cases are executed.

<source lang="cpp">#include <stdio.h> main(){

       int i= 6;
       
       switch(i%2)
       {
           case 0 : printf("the number %d is even \n",i);
          
           case 1 : printf("the number %d is odd \n",i);
                    break;
       }

}</source>

the number 1 is odd
     the number 2 is even
     the number 3 is odd
     the number 4 is even

Nest if statement in case statement

<source lang="cpp">#include <stdio.h>

1. include <ctype.h>

int main(void) {

 double number1 = 3.0;
 double number2 = 4.0;
 char operation = "+";
 char reply = 0;      

 switch(operation)
 {
   case "+":                    
     printf("= %lf\n", number1 + number2);
     break;
   case "-":                    
     printf("= %lf\n", number1 - number2);
     break;
   case "*":                    
     printf("= %lf\n", number1 * number2);
     break;
   case "/":
     if(number2 == 0)           
       printf("\n\n\aDivision by zero error!\n");
     else
       printf("= %lf\n", number1 / number2);
      break;
   case "%":                    
     if((long)number2 == 0)
       printf("\n\n\aDivision by zero error!\n");
     else
       printf("= %ld\n", (long)number1 % (long)number2);
     break;
   default:                     
     printf("\n\n\aIllegal operation!\n");
     break;
 }
 return 0;

}</source>

= 7.000000

The switch statement

To take one of a number of possible actions.

switch is preferred over multiple if...else statements.

The general form of a switch statement is

<source lang="cpp">switch(switch_expr)

    {
      case constant expr1 :  S1;
                             S2;
                             break;
      case constant expr1 :  S3;
                             S4;
                             break;
      .....
      default             :  S5;
                             S6;
                             break;
    }</source>

Two cases, one action

<source lang="cpp">#include <stdio.h> int main(void) {

 char answer = 0;
 printf("Enter Y or N: ");
 scanf(" %c", &answer);
 switch (answer)
 {
   case "y": case "Y":
     printf("\nYou responded in the affirmative.");
     break;
   case "n": case "N":
     printf("\nYou responded in the negative.");
     break;
   default:
     printf("\nYou did not respond correctly...");
     break;
 }
 return 0;

}</source>

Enter Y or N: N
     
     You responded in the negative.

Use switch structure to evaluate characters

<source lang="cpp">#include <stdio.h> main(){

   char iResponse = "A";
   printf("input(a or A or B or b or c or C):");
   scanf("%d", &iResponse);
   switch (iResponse) {
     case "a": case "A":
       printf ("\nYou selected the character a or A\n");
       break;
     case "b": case "B":
       printf("You selected the character b or B\n");
       break;
     case "c": case "C":
       printf("You selected the character c or C\n");
       break;
   }

}</source>

Use switch to simplify the logic

<source lang="cpp">#include <stdio.h> int main(void) {

 int choice = 2;                 

 if((choice>10) || (choice <1)){
   choice = 11;                 
 }   
 switch(choice)
 {
   case 7:
     printf("\nCongratulations!");
     break;                    
   case 2:
     printf("\nA");
     break;                      
   case 8:
     printf("\nB");
     break;     
   case 11:
     printf("\nC");
   default:
     printf("\nSorry, you lose.\n");
     break;             
 }
 return 0;

}</source>

A

Use the switch structure to evaluate a user"s response from a menu (without break).

<source lang="cpp">#include <stdio.h> main(){

 int iResponse = 0;
 printf("\nPlease select a category (1-4): ");
 scanf("%d", &iResponse);
 switch (iResponse) {
   case 1:
     printf("\nYou selected 1\n");
   case 2:
     printf("You selected 2\n");
   case 3:
     printf("You selected 3\n");
   case 4:
     printf("You selected 4\n");
 } //end switch

} //end main function</source>

Please select a category (1-4): 1
      
      You selected 1
      You selected 2
      You selected 3
      You selected 4