he page is not part
of the garbage collected heap, a small integer <I>n</i>, indicating
that the page is part of large object, starting at least <I>n</i> pages
back, or a pointer to a descriptor for the page.  In the first case,
the candidate pointer i not a true pointer and can be safely ignored.
In the last two cases, we can obtain a descriptor for the page containing
the beginning of the object.
<LI>
The starting address of the referenced object is computed.
The page descriptor contains the size of the o