THE SWITCH STATEMENT

THE SWITCH STATEMENT

We can design a program using if statements to control the selection. However, the complexity of such a program increases dramatically when the   number of alternatives increases. The program becomes difficult to read and follow. C has a bult-in multiway decision statement known as a switch. The switch statement test the value of a given variable (or expression) against a list of case values and when a match is found, a block of statements associated with that case is executed. The general form of the switch statement is as  shown below:

The expression is an integer expression or characters. Value-1, value-2 ... are  constants are known as case lables. Each of these values should be unique within a swich statement. block-1, block-2 ..... are statement

 lists. There is no need to put braces around these blocks. Note that case labels end with a colon(:). When the switch is executed, the value of the expression is successively compared against the values value-1, value-2, ..... . If a case is found whose value matches with the value of the expression, then the block of statements that

follows the case are executed.:

The Switch Statement is shown below:

switch(expression)

{

case value-1:

block-1;

break;

case value-2:

block-2;

break;

.........

default:

default-blcok;

break;

} statement-x;

The traffic light program (switch)
A program that displays the recommended actions depending on the color of a traffic light. Unlike the previous program, this implementation uses the switch statement.

#include <stdio.h>

int main (void)

{

 char colour;

 /* ask user for colour */

   printf ("Enter the colour of the light (R,G,Y,A): ");

   scanf ("%c", &colour);

   /* test the alternatives */      

   switch (colour)

   {

       /* red light */

       case 'R':

       case 'r':

                 printf ("STOP! \n");

                 break;

  /* yellow or amber light */

       case 'Y':

       case 'y':

       case 'A':

       case 'a':

                 printf ("CAUTION! \n");

                 break;

          /* green light */

       case 'G':

       case 'g':

                 printf ("GO! \n");

                 break;

     /* other colour */

       default:

                 printf ("The colour is not valid.\n");

   }

 return (0);

}