Null pointer in C++

Question

When in C++ I declare a null pointer to be int* p=0, does that mean the zero is some special constant of integer pointer type, or does it mean that p

Answer 1

It means that an integral constant expression with value zero has a special meaning in C++; it is called a null pointer constant. when you use such an expression to initialize a pointer with, or to assign to a pointer, the implementation ensures that the pointer contains the appropriately typed null pointer value. This is guaranteed to be a different value to any pointer pointing at a genuine object. It may or may not have a representation that is "zero".

ISO/IEC 14882:2011 4.10 [conv.ptr] / 1:

A null pointer constant is an integral constant expression (5.19) prvalue of integer type that evaluates to zero or a prvalue of type std::nullptr_t. A null pointer constant can be converted to a pointer type; the result is the null pointer value of that type and is distinguishable from every other value of object pointer or function pointer type.