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Saturday, May 26, 2012

Switch case statement


 Switch case statement

The switch-case  statement is a multi way decision that tests whether an expression matches one of the number of constant expression and branches accordingly. switch case statements are a substitute for long if statements. The basic format for using switch case is outlined below.
Switch (expression or variable)               
{               
 case constant-expr1:          
   statement sequence;         
  break;       
 case constant-expr2:          
   statement sequence;
  break;               
 case : constant-expr3: 
  statement sequence;
  break;       
  ...          
 default:              
  statement sequence;  
}
The expression or variable has a value. The case says that if the expression or variable has value which  is after that cases then execute the statements that  follows the colon until the break is reached. Only one case is executed since only one value holds for expression or variable inside switch. The break is used to break out of the case statements. Break is a keyword that breaks out of the code block .The break prevents the
program from testing the next case statement also.

            Below is a sample program, in which not all of the proper functions are actually declared, but which shows how one would use switch case in a program.
#include <stdio.h>     
#include <conio.h>     
void main()
{        
  int input;     
  printf("1. Play game");      
  printf("2. Load game");      
  printf("3. Play multiplayer");      
  printf("4. Exit");   
  scanf(“%d”,&input);   
  switch (input)       
  {        /*switch block starts */
   case 1: printf(“Play game is choosen”);  /*note use of  : and ; */
           break;       
   case 2:
           printf(“Load game is choosen”);     
        break; 
   case 3:              
         printf(“Play multiplayer is choosen”);
          break;       
   case 4:
         exit(0);
  default:       
        printf(“Error, bad input “);  
  }         /* end of switch */
  }        /* end of main() */

Another example:
/* this program takes input a alphabetic character and determines that either the character is vowel or consonant  and if other character is found than letter it gives appropriate message */

#include<stdio.h>
void main()
{
 char ch;
 printf(“\nEnter  a character:”);
 scanf(“%c”,&ch);
 if((ch>=’A’&&ch<=’Z’)||(ch>=’a’&&ch<=’z’))
 {
  printf(“This is alphabetic character.”);
  switch(ch)
  {
   case ‘A’: case ‘a’:
   case ‘E’: case ‘e’:
   case ‘I’: case ‘i’:
   case ‘O’: case ‘o’:
   case ‘U’: case ‘u’:
    printf(“\nThe letter is vowel “);
   break;
   default: printf(“\nThe letter is consonant.”);
  }    /* end switch */
 } /*end if */
 else printf(“The character is not alphabetic.”);
}   /*end main() */

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