Returns the difference between the top of the Lisp heap and a maximum memory limit in 32-bit LispWorks.
An integer address, or
If a limit on the maximum memory has been set by
returns the difference between the current top of the Lisp heap and that limit. That is, the amount by which the heap can grow.
. This is the default behavior.
is implemented only in 32-bit LispWorks. It is not relevant to the Memory Management API in 64-bit implementations.
LispWorks User Guide and Reference Manual - 21 Dec 2011