C++ pointers and member access: what exactly is printed, and why do (*p).x and p->x show the same value? #include class Tab { public: int x; }; int main() { Tab *p = new Tab(); (*p).x = 10; cout<< (*p).x << " " << p->x << " " ; p->x = 20; cout<< (*p).x << " " << p->x ; return 0; }

Introduction / Context: This program checks understanding of pointer member access in C++. The expression (*p).x and the shorthand p->x both access the same data member of the object that p points to. The code sets the member twice and prints after each assignment to verify aliasing behavior.

Given Data / Assumptions:

• p is obtained via new Tab(), so the pointer is valid.
• Tab has a public integer member x.
• Two prints occur: first after writing 10, then after writing 20.

Concept / Approach: The dereference operator * yields the object to which a pointer refers. Member access uses . on an object and -> on a pointer. Therefore, (*p).x and p->x are equivalent lvalues that refer to the same integer member.

Step-by-Step Solution: 1) (*p).x = 10; stores 10 in the member. 2) The first print outputs 10 twice because both forms read the same member. 3) p->x = 20; overwrites the same location with 20. 4) The second print outputs 20 twice for the same reason.

Verification / Alternative check: Replace (*p).x with p->x everywhere; observable behavior is unchanged since both are identical in meaning.

Why Other Options Are Wrong: “Garbage” outputs would require uninitialized reads, which do not occur here. There is no compile-time error since syntax and access specifiers are correct.

Common Pitfalls: Forgetting to allocate the object before dereferencing; confusing p.x (invalid for pointers) with p->x; assuming different storage for the two notations.

Final Answer: 10 10 20 20