C Programming language

Decision using switch

The control statement that allows us to make a decision from the number of choices is called "switch". the switch is look as following:

switch ( integer expression )
{
case constant 1 :
do this ;
case constant 2 :
do this ;
case constant 3 :
do this ;
default :
do this ;
}

we can take an example of the switch case to understand easily it in deep.

main( )
{
int i = 2 ;
switch ( i )
{
case 1 :
printf ( "I am in case 1 \n" ) ;
case 2 :
printf ( "I am in case 2 \n" ) ;
case 3 :
printf ( "I am in case 3 \n" ) ;
default :
printf ( "I am in default \n" ) ;
}
}
The output of this program would be:
I am in case 2
I am in case 3
I am in default

Use of switch with decision control statement

1. Every statement in a switch must belong to some case or the other.
2. we can also use char values in case and switch.
3. If we have no default case, then the program simply falls through the entire switch and continues with the next instruction (if any,) that follows the closing brace of switch.
4. switch is a replacement for 'if' because it offers a better way of writing program as compared to if.
5. The advantage of switch over if is that it leads to a more structured program and the level of indentation is manageable, more so if there are multiple statements within each case of a switch.
6. The break statement when used in a switch takes the control outside the switch. However, use of continue will not take the control to the beginning of switch as one is likely to believe.

Switch versus if-else ladder

1. A float expression cannot be tested using a switch.
2. Cases can never have variable expressions (for example it is wrong to say case a +3 : ).
3. Multiple cases cannot use same expressions. Thus the following switch is illegal:

   switch ( a )
   {
   case 3 :
   ...
   case 1 + 2 :
   ...
   }