In C pointer terminology, what does the expression (void*)0 represent?
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ARepresentation of NULL pointer
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BRepresentation of void pointer
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CError
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DNone of above
Answer
Correct Answer: Representation of NULL pointer
Explanation
Introduction / Context:Null pointers are used to indicate that a pointer intentionally does not point to any valid object or function. C defines specific ways to write a null pointer constant so that it can be converted to any pointer type safely.
Given Data / Assumptions:
- We are evaluating the literal (void*)0.
- Standard C semantics for pointer constants apply.
Concept / Approach:(void*)0 is a canonical spelling of a null pointer constant: the integer constant 0 explicitly cast to pointer-to-void. When assigned to or compared with any object pointer type, it becomes that type’s null pointer. It does not represent a generic “void pointer value” in use; it specifically denotes the absence of a valid address.
Step-by-Step Solution:Start with the integer constant 0, which is a null pointer constant in C.Cast to (void*) to make the null-ness explicit and type-safe for function overloading or diagnostics.Use in code: int p = (void)0; /* p becomes a null pointer /
Verification / Alternative check:Comparisons like if (p == NULL) or if (p == (void)0) are equivalent when p is a pointer to object.
Why Other Options Are Wrong:
- “Representation of void pointer” is vague; (void*)0 is not a generic pointer value, it is the null pointer value of type void*.
- “Error” and “None of above” are incorrect because the expression is well-defined and standard.
Common Pitfalls:Confusing (void*)0 with 0 or NULL in C++ where nullptr is preferred; assuming null pointers are all-bits-zero at the machine level (the standard does not require that).
Final Answer:Representation of NULL pointer.