Case Control Structure(SWITCH)
In real life we are often faced with situations where we are required to make a choice between a number of alternatives rather than only one or two. Serious C programming is same, the choice we are asked to make is more complicated than merely selecting between two alter natives. C provides a special control statement that allows us to handle such cases effectively; rather than using a
series of IF statements.
Decisions Using Switch:
The control statement that allows us to make a decision from the numbers of choices is called a SWITCH,or more correctly a Switch-Case-Default, Since these 3 keywords go together to make up the control statement.They most often appear as Follows:
switch(inter expression)
{
case constant 1:
do this;
case constant 2:
do this;
case constant 3:
do this;
default:
do this;
}
The integer expression following the keyword SWITCH is any C expression that will yield an integer constant like 1,2 or 3, or an expression that evaluates to an integer.The keyword case is followed by an integer or a character constant.
Process of Execution:
When we run the program containing the switch,first the integer expression following the keyword switch is evaluated. The value it gives is then matched ,one by one, against the constant values that follow the case statements. When a match is found, the program executes the statements following that case, and all subsequent case and default statements. If no match is found with any of the case statements, default is executed.
Example:47
main()
{
int i=1;
switch(i)
{
case 1:
printf("I am in case1");
case 2:
printf("This is second one");
case 3:
printf("This is third case");
default :
printf("your are in default");
}
}
OUTPUT:
The output of this program would be:
I am in case1
This is second one
This is third case
your are in default
The output is definitely not what we expected. We didn't expect 2nd,3rd and default cases print output.If you want only case 2 should get executed,it is up to you to get out of the switch then and there by using a Break statement. Note that there is no need for a break statement after the
default,since the control comes out of the switch anyway.
Example:48
main()
{
int i=2;
switch(i)
{
case 1:
printf("I am in case1");
break;
case 2:
printf("This is second one");
break;
case 3:
printf("This is third case");
break;
default:
printf("your are in default");
}
}
OUTPUT: This is second one
Example:53
main()
{
char suite=3;
switch(suite)
{
case 1:
printf("\n Diamond");
case 2:
printf("\n Spade");
default:
printf("\n Heart");
}
printf("\n I thought one wears a suite");
}
OUTPUT:
Heart
I thought one wears a suite
Example:54
main()
{
int c=3;
switch(c)
{
case 'v' :
printf("This is v case");
break;
case 3:
printf(" Iam in a Third case");
break;
case 12:
printf("This is 12 th case");
break;
default:
printf("Default case?");
break;
}
}
OUTPUT:I am in a Third case.
Example:55
main()
{
int k,j=2;
switch(k=j+1)
{
case 0:
printf("\n Hai");
case 1:
printf("\n Hello");
case 2:
printf("\n Hai 1");
default:
printf("\n Bye");
}
}
OUTPUT:
Bye
Example:56
main()
{
int i=0;
switch(i)
{
case 0:printf("\n Customers are dicey");
case 1:printf("\n Markets are priery");
case 2:printf("\n Investors are moody");
case 3:printf("\n Employees are lazy");
}
}
OUTPUT: Customers are dicey
Markets are priery
Investors are moody
Employees are lazy
Explanation: Here case is not having break that's why all the statements preceded by required cases are also executed.
Example:57
main()
{
int k;
float j=2.0;
switch(k=j+1)
{
case 3:
printf("\n Trapped");
break;
default:
printf("\n Caught!");
}
}
OUTPUT:
Caught!
Example:58
main()
{
int i=4;
switch(i)
{
default:
printf("\n A mouse is an Alphabet
built by Japaneese");
case 1:
printf("\n Breeding rabbits is a
raising experience");
break;
case 2:
printf("Friction is a drag");
break;
case 3:
printf("\n If pratice makes perfect,
then noboby's perfect");
}
}
OUTPUT:
A mouse is an Alphabet built by Japanese
Breeding rabbits is a raising experience
Example:59
main()
{
int i=4,j=2;
switch(i)
{
case 1:
printf("\n To err is human,to
forgive is against company
policy");
break;
case j:
printf("\n If you have nothing to do,
don't do it here");
break;
}
}
OUTPUT: constant expression required in the second case,
we can not use j.
Example:60
main()
{
int i=1;
switch(i)
{
case 1:
printf("\n Radio Active cats have
18 half-lives");
break;
case 1*2+4:
printf("Bottle for rent-inquire
within");
break;
}
}
OUTPUT: Radio Active cats have 18 half-lives
Explanation: No error in this program. Constant expression
like
1*2+4 are acceptable in cases of a switch.
Example:61
main()
{
int a =10;
switch(a)
{
}
printf("\n Programmers never die, They just
get lost in the processing");
}
Explanation: Though never required, there can exist a switch
which has no cases.
OUTPUT: Programmers never die, They just get lost in the
processing
Example:62
main()
{
int i=1;
switch(i)
{
printf("hello");
case 1:
printf(" \n Individualists unite!");
break;
case 2:
printf("\n Money is the root of
all wealth");
break;
}
}
Explanation: Though there is no error, irrespective of the value of i the first printf() can never get executed . In other words, all statements in a switch have to belong to same case or the other
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