C Programming - Control Instructions - Discussion

@Mohit bansal.

I compiled it. Got the output as mentioned by you mohit.

Explanation:

y=x=10 means the values of x and y have been assigned as 10.

Now,
Z = x<10.

Means, value of z has been assigned as the same as x( here it is 10 from previous line).
But z is not <10. z is =10(since x is 10).

Thus the condition is false and so it returned a value 0. If the condition was true, then the compiler would return a value of 1 and the output would be x=10, y=10, z=1.

This is like a rule.

in C.

The cases cant be defined as the any operation methods!

Example: the following cases is not allowed.

case 3+2:
case 3/2:
case 3*2;
etc aren't allowed.

The definition after the case must a mere number or the character upon what data type you define.

example:

int a = 4;
switch (a)
case 1:
case 2:
case 3:
case 4:

or else it might be

char ch='A';
switch (ch)

case 'A':
case 'B':
etc..etc..etc.

It is needed because the absence of break statement will leads the execution to continue
the codes until it finds break.

For example:

#include<stdio.h>
int main()
{
switch(1)
{
case 1:
{ printf("1");
break;// if break statement is not included,then the output will 1 2. else the output will be 1.
}
case 2:
{ printf("2");
break;
}
}
}

Addition, multiplication, division are allowed in case statement but both the operand should be constant, operation is performed at compile time, for this case compiler get confused while choosing case 5 (ambiguity). So it will raise compile time error.

#include<stdio.h>
int main()
{
int x=3,y,z;
y=x=10;
z=x<10;
printf("x=%d y=%d z=%d\n",x,y,z);
return 0;
}

The output is x = 10, y = 10, z = 0.

Please explain?

@Deepu.

you are wrong about those operation.
You can perform arithmetic operation on case expressions.

case 2+3:
case 3-2:
case 2*3:
case 3/2:

is allowed.

I have a doubt for every case the break statement is needed or not. If it is not needed what will be the output? Can any one explain me?

I compiled it. And I got it error.

So the options are wrong. Also no duplicates should be present in switch.

If there's no break statement used, case 5 will not matter right? So it should keep printing till break?

Yes addition is allowed in case statements but case 3+2 is equal to case 5 so ambiguity is occurs.