C++ Pointers & Functions Question:

A NULL pointer has a fixed reserved value that is not zero or space, which indicates that no object is referred. NULL pointers are used in C and C++ as compile-time constant. NULL pointer represents certain conditions, like successor to the last element in linked list, while a consistent structure of the list of nodes are maintained.

A void pointer is a special pointer that points to an unspecified object. A null pointer can not be dereferenced. The address manipulation can directly be done by pointer casting to and from an integral type of sufficient size.