Mark                     Saves Current Start of Heap

 Mark(var P : <pointer>);

    Stores the current start-of-the-heap address in P. After heap space
    has been allocated with the procedure New, a call to Release(P) will
    deallocate all of the space above P, thus freeing this space for new
    heap allocation.

               P    A pointer to any data type.

          Notes:    Never use Mark and Dispose in the same program. Using
                    them together will cause unpredictable results.

                    All this procedure does is move the heap pointer to
                    the pointer variable P. To deallocate the space from P
                    to the top of the heap space, just call the procedure
                    Release(P). Release just sets the heap pointer to P
                    and updates the amount of heap memory available.

                    Note that the Mark/Release pair can not release space
                    used by variables in the middle of the heap. Use
                    Dispose if this operation is needed.

                    Use the function MemAvail to determine the amount of
                    space available on the heap at any given time.

  -------------------------------- Example ---------------------------------

           Mark(TempPtr);           { mark current top of heap }
           ...
           Release(TempPtr);        { restore heap to that mark }