Can we add pointers together in C language?

Question

Is it valid in C

P = P1 + P2 - P3 

Answer 1

U can add a integer to a pointer like P1+10 is valid but P1 + P2 is not valid. But the thing you are trying to achieve can be achieved by the following way...

P = P1 + (P2 - P3)

assuming all pointers are of same type.

Answer 2

It is not valid.

Since the pointer points address, if we add 2 address then resulting address may point to different segment or address. I guess this is the reason for this restriction.