In Java/C#, it doesn't always:
int x = 1; int y = 2; x = y;
The variable `x` does not refer to the object that `y` is referring to(as there is no reference involved at all).
Assignment is a procedure that makes `x` equal to `y` without modifying `y`. However, if `x` refers to `y`, then we can modify `y` after assignment to `x`. This destroys the ability to reason locally about the code, because each object essentially becomes as good as a global variable.
Even though C++ has areas where things gets complicated, this is the one thing that C++ keeps very simple and consistent. There is only one definition of copy, assignment, and equality, whereas in java there is multiple definitions(deep copy vs shallow copy, `==` vs `.equals`).
> That’s called value semantics, although I would prefer the term state semantics: objects do not have a value, they have state, and that’s what’s being transferred here.
No. Its value semantics, as these objects represent some entity. The interpretation of the state(or datum to be more precise) is the known as the object's value. For example, when copying a `std::vector` the internal state of the vector will be different on copy, as it will point to new piece of memory, however, its value will still be the same.
> But experience shows that making a copy of an object is hard.
The compiler already generates a copy constructor and assignment for you. Its only necessary to write one, when one is dealing with low-level pointers. Using the standard built-in types and containers, writing a copy constructor is never needed.