But you can't actually directly address I/O ports in C, and directly addressing memory (via pointer arithmetic which oversteps the bounds of an object, or which

But you can't actually directly address I/O ports in C, and directly addressing memory (via pointer arithmetic which oversteps the bounds of an object, or which puns the type of an object) invokes undefined behavior. Both those things depend on details of the underlying architecture, ABI, and operating system, and are abstracted away in C.