Memory layout and register usage
================================

eax stores the top element of the stack. esi points to the second element of the stack.

The stack stores its elements little-endian and grows downwards. This is an elegant design which allows convenient manipulation of the top element, as many instructions modify eax. It was motivated by drop becoming simply a lodsd. It also allows words that operate below the top element, such as nip, to be implemented easily.

-----
|eax|
-----

-----
|   | <- esi
-----
|   |
-----
 ...

(but the stack is actually hanging from the ceiling, dangling down)

The return stack is pointed to by esp, grows downwards, and uses byte addressing.

Registers
---------
eax: 0 (000)  top stack element
ecx: 1 (001)
edx: 2 (010)  address register, also used to to extend precision to 64 bits with edx:eax
ebx: 3 (011)
esp: 4 (100)  pointer to the return stack
esi: 6 (110)  pointer to the second stack element
edi: 7 (111)  pointer to the next word to be interpreted when interpreting

~/cf/internals/mem.html