It would not be meaningful to test for inequality. Also, you can't perform arithmetic on pointers. NULL is a special pointer value. A pointer equal to NULL is guaranteed not to point to anything. If you try to dereference a null pointer your program will abend.
Pointers are mainly useful for stitching together various data objects to form a data structure .
Typically, data structures are built from dynamically allocated memory. Pointers can sometimes simplify the interface to a subprogram, especially in an IMS program. This approach avoids the need to pass PCBs all the way up and down the calling chain. Try to use a more conventional approach if it is not too cumbersome. So far as possible, isolate your pointer operations in a subprogram.