Introduction:
From Nand to Tetris
Building a Modern Computer From First Principles
www.nand2tetris.org
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 1
The course at a glance
Objectives:
Understand how hardware and software systems are built,
and how they work together
Learn how to break complex problems into simpler ones
Learn how large scale development projects are planned and executed
Have fun
Methodology:
Build a complete, general-purpose, and working computer system
Play and experiment with this computer, at any level of interest.
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 2
Some course details
12 projects, can be done by pairs
Hardware projects are done and simulated in HDL
(Hardware Description Language)
Software projects can be done in any language of your choice
(we recommend Java)
Projects methodology:
o Design (API) + test materials are given
o Implementation done by students
Tools: simulators, tutorials, test scripts
Book
Q&A policy
Course grade.
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 3
Demo
Pong, 1985
Pong, 2011
Pong, on our
computer
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 4
Course theme and structure
Human
Thought
Abstract design
Software
hierarchy
abstract interface
Chapters 9, 12
H.L. Language
&
Operating Sys.
Compiler
abstract interface
Chapters 10 - 11
Virtual
Machine
VM Translator
abstract interface
Chapters 7 - 8
Assembly
Language
Assembler
Chapter 6
abstract interface
Machine
Language
Computer
Architecture
abstract interface
Chapters 4 - 5
Hardware
Platform
Hardware
hierarchy
Gate Logic
abstract interface
Chapters 1 - 3
Chips &
Logic Gates
Electrical
Engineering
Physics
(Abstraction–implementation paradigm)
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 5
Application level: Pong (example app)
Ball
abstraction
Bat
abstraction
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 6
The big picture
Human
Thought
Abstract design
Software
hierarchy
abstract interface
Chapters 9, 12
H.L. Language
&
Operating Sys.
Compiler
abstract interface
Chapters 10 - 11
Virtual
Machine
VM Translator
abstract interface
Chapters 7 - 8
Assembly
Language
Assembler
Chapter 6
abstract interface
Machine
Language
Computer
Architecture
abstract interface
Chapters 4 - 5
Hardware
Platform
Hardware
hierarchy
Gate Logic
abstract interface
Chapters 1 - 3
Chips &
Logic Gates
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
Electrical
Engineering
Physics
slide 7
High-level programming (our very own Jack language)
/**
/** AA Graphic
Graphic Bat
Bat for
for aa Pong
Pong Game
Game */
*/
class
Bat
{
class Bat {
field
//
field int
int x,
x, y;
y;
// screen
screen location
location of
of the
the bat's
bat's top-left
top-left corner
corner
field
int
width,
height;
//
bat's
width
&
height
field int width, height;
// bat's width & height
//
// The
The class
class constructor
constructor and
and most
most of
of the
the class
class methods
methods are
are omitted
omitted
/**
/** Draws
Draws (color=true)
(color=true) or
or erases
erases (color=false)
(color=false) the
the bat
bat */
*/
method
void
draw(boolean
color)
{
method void draw(boolean color) {
do
do Screen.setColor(color);
Screen.setColor(color);
do
Screen.drawRectangle(x,y,x+width,y+height);
do Screen.drawRectangle(x,y,x+width,y+height);
return;
return;
}}
Typical call to
an OS method
/**
/** Moves
Moves the
the bat
bat one
one step
step (4
(4 pixels)
pixels) to
to the
the right.
right. */
*/
method
void
moveR()
{
method void moveR() {
do
do draw(false);
draw(false); //
// erase
erase the
the bat
bat at
at the
the current
current location
location
let
x
=
x
+
4;
//
change
the
bat's
X-location
let x = x + 4;
// change the bat's X-location
//
but
don't
go
beyond
// but don't go beyond the
the screen's
screen's right
right border
border
if
((x
+
width)
>
511)
{
if ((x + width) > 511) {
let
let xx == 511
511 -- width;
width;
}}
do
do draw(true);
draw(true); //
// re-draw
re-draw the
the bat
bat in
in the
the new
new location
location
return;
return;
}}
Ball
abstraction
Bat
abstraction
}}
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 8
Operating system level (our very own Jack OS)
/**
/** An
An OS-level
OS-level screen
screen driver
driver that
that abstracts
abstracts the
the computer's
computer's physical
physical screen
screen */
*/
class
class Screen
Screen {{
static
static boolean
boolean currentColor;
currentColor; //
// the
the current
current color
color
//
// The
The Screen
Screen class
class is
is aa collection
collection of
of methods,
methods, each
each implementing
implementing one
one
//
abstract
screen-oriented
operation.
Most
of
this
code
is
omitted.
// abstract screen-oriented operation. Most of this code is omitted.
/**
/** Draws
Draws aa rectangle
rectangle in
in the
the current
current color.
color. */
*/
//
the
rectangle's
top
left
corner
is
anchored
// the rectangle's top left corner is anchored at
at screen
screen location
location (x0,y0)
(x0,y0)
//
// and
and its
its width
width and
and length
length are
are x1
x1 and
and y1,
y1, respectively.
respectively.
function
function void
void drawRectangle(int
drawRectangle(int x0,
x0, int
int y0,
y0, int
int x1,
x1, int
int y1)
y1) {{
var
var int
int x,
x, y;
y;
let
x
=
x0;
let x = x0;
while
while (x
(x << x1)
x1) {{
let
let yy == y0;
y0;
while(y
while(y << y1)
y1) {{
do
do Screen.drawPixel(x,y);
Screen.drawPixel(x,y);
let
let yy == y+1;
y+1;
}}
let
let xx == x+1;
x+1;
Ball
abstraction
Bat
abstraction
}}
}}
}}
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 9
The big picture
Human
Thought
Abstract design
Software
hierarchy
abstract interface
Chapters 9, 12
H.L. Language
&
Operating Sys.
Compiler
abstract interface
Chapters 10 - 11
Virtual
Machine
VM Translator
abstract interface
Chapters 7 - 8
Assembly
Language
Assembler
Chapter 6
abstract interface
Machine
Language
Computer
Architecture
abstract interface
Chapters 4 - 5
Hardware
Platform
Hardware
hierarchy
Gate Logic
abstract interface
Chapters 1 - 3
Chips &
Logic Gates
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
Electrical
Engineering
Physics
slide 10
A modern compilation model
Some
language
...
Some
compiler
...
Some Other
language
Jack
language
Proj. 9: building an app.
Proj. 12: building the OS
Jack
compiler
Some Other
compiler
Projects
10-11
VM language
VM
implementation
over CISC
platforms
CISC
machine
language
VM imp.
over RISC
platforms
RISC
machine
language
CISC
machine
RISC
machine
written in
a high-level
language
...
...
VM imp.
over the Hack
platform
VM
emulator
Projects
7-8
Hack
machine
language
Projects
...
other digital platforms, each equipped
with its VM implementation
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
1-6
Any
computer
Hack
computer
slide 11
Compilation 101
Intermediate code
>
Source code
(x
(x ++ width)
width) >> 511
511
parsing
+
511
Code
generation
push
push xx
push
push width
width
add
add
push
push 511
511
gt
gt
x
Abstraction
Syntax
Analysis
width
Parse
Tree
Semantic
Synthesis
Implementation
Observations:
Modularity
Abstraction / implementation interplay
The implementation uses abstract services from the level below.
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 12
The Virtual Machine (our very own VM, modeled after Java’s JVM)
if ((x+width)>511) {
let x=511-width;
}
...
width
75
450
...
// VM implementation
s2
memory (before)
x
450
sp
75
...
push x
// s1
push width
// s2
add
// s3
push 511
// s4
525
gt
// s5
511
if-goto L1
// s6
goto L2
// s7
s4
s5
s9
1
511
sp
450
sp
sp
L1:
push 511
// s8
push width
// s9
sub
// s10
pop x
// s11
s10
memory (after)
...
61
sp
width
...
L2:
...
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
450
x
61
...
slide 13
The big picture
Human
Thought
Abstract design
Software
hierarchy
abstract interface
Chapters 9, 12
H.L. Language
&
Operating Sys.
Compiler
abstract interface
Chapters 10 - 11
Virtual
Machine
VM Translator
abstract interface
Chapters 7 - 8
Assembly
Language
Assembler
Chapter 6
abstract interface
Machine
Language
Computer
Architecture
abstract interface
Chapters 4 - 5
Hardware
Platform
Hardware
hierarchy
Gate Logic
abstract interface
Chapters 1 - 3
Chips &
Logic Gates
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
Electrical
Engineering
Physics
slide 14
Low-level programming (on the Hack computer)
For now,
ignore all
details!
Virtual machine program
...
push x
push width
add
push 511
gt
if-goto L1
goto L2
L1:
push 511
push width
sub
pop x
L2:
...
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 15
Low-level programming (on the Hack computer)
For now,
ignore all
details!
Virtual machine program
...
push x
push width
add
push 511
VM translator
Assembly program
gt
if-goto L1
// push 511
goto L2
@511
L1:
D=A
push 511
@SP
push width
A=M
sub
M=D
pop x
@SP
L2:
// D=511
// *SP=D
M=M+1 // SP++
...
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 16
Low-level programming (on the Hack computer)
For now,
ignore all
details!
Virtual machine program
...
push x
push width
add
push 511
VM
translator
Assembly program
gt
if-goto L1
// push 511
goto L2
@511
L1:
D=A
// D=511
push 511
@SP
push width
A=M
sub
M=D
pop x
@SP
@SP
M=M+1 // SP++
L2:
Assembler
// *SP=D
Executable
0000000000000000
1110110010001000
...
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 17
The big picture
Human
Thought
Abstract design
Software
hierarchy
abstract interface
Chapters 9, 12
H.L. Language
&
Operating Sys.
Compiler
abstract interface
Chapters 10 - 11
Virtual
Machine
VM Translator
abstract interface
Chapters 7 - 8
Assembly
Language
Assembler
Chapter 6
abstract interface
Machine
Language
Computer
Architecture
abstract interface
Chapters 4 - 5
Hardware
Platform
Hardware
hierarchy
Gate Logic
abstract interface
Chapters 1 - 3
Chips &
Logic Gates
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
Electrical
Engineering
Physics
slide 18
For now,
ignore all
details!
Machine language semantics (our very own Hack platform)
Code semantics, as interpreted by the Hack hardware platform
Instruction code
(0=“address” inst.)
Address
Code syntax
0
0000000000000000
@0
1111110111001000
M=M-1
1
0
1
0
0
1 1
Instruction code
(1=“compute” inst.)
0
1
0
1
0
0
0
1
0
1
0
1
0
0
0
0
0
1
0
0
0
0
0
0
ALU
operation code
Destination
Code
Jump
Code
(M-1)
(M)
(no jump)
We need a hardware architecture that realizes this semantics
The hardware platform should be designed to:
o Parse instructions, and
o Execute them.
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 19
For now,
ignore all
details!
Computer architecture (Hack platform, approx.)
instruction
Instruction
Memory
A
ALU
D
Data
Memory
data out
(M)
M
address of next
instruction
Program
Counter
data in
RAM(A)
A typical Von Neumann machine
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 20
The big picture
Human
Thought
Abstract design
Software
hierarchy
abstract interface
Chapters 9, 12
H.L. Language
&
Operating Sys.
Compiler
abstract interface
Chapters 10 - 11
Virtual
Machine
VM Translator
abstract interface
Chapters 7 - 8
Assembly
Language
Assembler
Chapter 6
abstract interface
Machine
Language
Computer
Architecture
abstract interface
Chapters 4 - 5
Hardware
Platform
Hardware
hierarchy
Gate Logic
abstract interface
Chapters 1 - 3
Chips &
Logic Gates
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
Electrical
Engineering
Physics
slide 21
Logic design
Combinational logic
Sequential logic
(leading to an ALU)
(leading to a RAM)
Putting the whole thing together (leading to a Computer)
Using … gate logic.
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 22
Gate logic
Hardware platform = inter-connected set of chips
Chips are made of simpler chips, all the way down to elemantary logic gates
Logic gate = hardware element that implements a certain Boolean function
Every chip and gate has an interface, specifying WHAT it is doing, and an
implementation, specifying HOW it is doing it.
Implementation
Interface
a
a
Xor
out
And
Not
b
Or
a
b
out
0
0
1
1
0
1
0
1
0
1
1
0
out
Not
b
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
And
slide 23
Hardware Description Language (HDL)
a
And
Not
Or
out
Not
b
And
CHIP Xor {
IN a,b;
OUT out;
PARTS:
Not(in=a,out=Nota);
Not(in=b,out=Notb);
And(a=a,b=Notb,out=w1);
And(a=Nota,b=b,out=w2);
Or(a=w1,b=w2,out=out);
}
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 24
The tour ends:
One implementation option (CMOS)
Interface
a
out
Nand
b
a
b
out
0
0
1
1
0
1
0
1
1
1
1
0
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
slide 25
The tour map, revisited
Human
Thought
Abstract design
Software
hierarchy
abstract interface
Chapters 9, 12
H.L. Language
&
Operating Sys.
Compiler
abstract interface
Chapters 10 - 11
Virtual
Machine
VM Translator
abstract interface
Chapters 7 - 8
Assembly
Language
Assembler
Chapter 6
Course overview:
Building this world,
from the ground up
abstract interface
Machine
Language
Computer
Architecture
abstract interface
Chapters 4 - 5
Hardware
Platform
Hardware
hierarchy
Gate Logic
abstract interface
Chapters 1 - 3
Chips &
Logic Gates
Elements of Computing Systems, Nisan & Schocken, MIT Press, www.nand2tetris.org , Introduction
Electrical
Engineering
Physics
slide 26