Notes for Nand2Tetris: Virtual Machine I: Stack Arithmetic

This is a note for Nand2Tetris unit 7 (Part II, Unit 1).

Unit 7.0

Jack program:

class Main {
    function void main() {
        do Output.printString("Hello World!");
        do Output.println(); // New line.
        return;
    }
}

What makes the abstraction work?

• Assembler
• Virtual machine
• Compiler
• Operating system

Nand2Tetris Part II is more demanding than Nand2Tetris Part I.

Unit 7.1

Module 1: Virtual Machine

• Understanding the abstraction
• Building the implementation

Module 1: Take Home Lessons

• Compilation (big picture)
• Virtualization
• VM abstraction
• Stack processing
• VM implementation
• Pointers
• Programming

Unit 7.2

VM Abstraction: the Stack

Stack operations:

• push: add a plate to the stack's top
• pop: remove the top plate

Applying a function $f$ on the stack:

• pops the argument(s) from the stack
• computes $f$ on the arguments
• pushes the result onto the stack

Stack arithmetic:

high-level:

x = 17 + 19

After compilation:

low-level:

push 17
push 19
add
pop x

Stack machine, manipulated by:

• Arithmetic / logical commands
• Memory segment commands
• Branching commands
• Function commands

Unit 7.3

VM Abstraction: Memory Segments

Memory segments:

• local
• argument
• this
• that
• constant
• static
• pointer
• temp

Syntax:

• push $segment$ $i$:
  Where $segment$ is: argument, local, static, constant, this, that, pointer, or temp
  and $i$ is a non-negative integer
• pop $segment$ $i$:
  Where $segment$ is: argument, local, static, this, that, pointer, or temp
  and $i$ is a non-negative integer

Unit 7.4

Pointer manipulation

asterisk: *

Stack machine

...

VM translator perspective

VM Translator:

• A program that translates VM code into machine language
• Each VM command generates several assembly commands

Unit 7.5

Implementing local