0xxxxxxx xxxxxxxx - reserved for private use by stdlib
1xxxxxxx xxxxxxxx - available for use in user programs
-## Heap ##
+## Heap and Pointers ##
- The first 256 heap addresses are reserved when using the stdlib.
+The first 16 heap addresses (`0-15`) are reserved when using the stdlib.
+
+By convention, functions which return a pointer will use the address `0` to
+represent a `NULL` pointer.
# Entry Points #
011xxx - heap functions
11000 ----- memset (heap.pvvs)
11001 ----- memcpy (heap.pvvs)
- 100xxx - unassigned
+ 11010 ----- memrand (heap.pvvs)
+ 11011 ----- memcmp (heap.pvvs)
+ 11100 ----- memsrch (heap.pvvs)
+ 11101 ----- <empty>
+ 11110 ----- slurp (heap.pvvs)
+ 11111 ----- spew (heap.pvvs)
+ 100xxx - string functions
+ 100000 ----- strlen (string.pvvs)
101xxx - unassigned
110xxx - conversion functions
111xxx - debug functions
111000 ----- dump heap (debug.pvvs)
+ 111001 ----- dump stack (debug.pvvs)
1xxxxxx - reserved for less common entry points
- 1000000 ----- print sign of number (stdio.pvvs)
- 1000001 ----- print magnitude of number (stdio.pvvs)
+ 1000000 ----- slurp registers (heap.pvvs)
+ 1000001 ----- spew registers (heap.pvvs)
+ 1000010 ----- print sign of number (stdio.pvvs)
+ 1000011 ----- print magnitude of number (stdio.pvvs)
# Misc #
00001000 xxxxxxxx - for use by 1000
00001001 xxxxxxxx - for use by 1001
...etc
+
+# Slurp and Spew #
+
+The stdlib uses heap[1] to heap[15] as registers.
+
+The `slurpreg` and `spewreg` functions facilitate this by `spew`ing the stack
+onto the heap's pseudo-registers or `slurp`ing the pseudo-registers back to the
+stack. The functions preserve order in complementary fashion.
+
+The `spewreg` function uses `heap[0]` for storage.