+The first 16 heap addresses (`0-15`) are reserved when using the stdlib.
+Within that reservation, heap[0] is used by `random` and heap[15] is used
+by `spewreg`. The remaining 14 locations, heap[1]-heap[14] are used as
+general-purpose registers.
+
+By convention, functions which return a pointer will use the address `0` to
+represent a `NULL` pointer.