Memory ◾ 111
that is no longer used will prevent that object from being reclaimed. Hence,
design guidelines recommend the nulling or zeroing out of pointers and
references once an object is considered inactive.
For one variable to hold the address of another, it must contain a refer-
ence or pointer as a eld. Whether or not a eld within an allocated memory
block represents a pointer requires knowledge of the type associated with
that eld. Some conservative garbage collection algorithms do not rely on
type information and treat every collection of bytes that could represent
a pointer as if it actually does. Why? To ensure that only those memory
blocks that are most denitively inaccessible are reclaimed. Consequently,
inactive block