with slides by Nisan & Schocken (www.nand2tetris.org)

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Course overview

Introduction to Computer Yung-Yu Chuang

with slides by Nisan & Schocken (www.nand2tetris.org)

Logistics

• Meeting time: 2:20pm-5:20pm, Tuesday

• Instructor: 莊永裕 Yung-Yu Chuang

• Webpage:

http://www.csie.ntu.edu.tw/~cyy/introcs

id / password

Textbook

The Elements of Computing Systems, Noam Nisan,

Shimon Schocken, MIT Press

Nand2Tetris on coursera Nand2Tetris2 on coursera

References (TOY)

Princeton’s Introduction to CS, http://www.cs.princeton.edu/intro cs/50machine/

http://www.cs.princeton.edu/intro

cs/60circuits/

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Grading (subject to change)

• Assignments (n projects, 50%) from the accompanying website

• Class participation (5%)

• Midterm quiz(20%)

• Final project (25%)

Early computers

Early programming tools First popular PCs

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Early PCs

• Intel 8086 processor

• 768KB memory

• 20MB disk

• Dot-Matrix printer (9-pin)

GUI/IDE

More advanced architectures

• Pipeline

• SIMD

• Multi-core

• Cache

More advanced software

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More “computers” around us My computers

iPhone 6+

(A8, ARMv8-A) Surface Pro 4

(Intel i5-6300 2.4GHz)

MacBook Air

(dual-core Intel Core i5, 1.3GHz) Desktop

(Intel Core i7-6700 3.4GHz, GTX960)

The downside

• “Once upon a time, every computer specialist had a gestalt understanding of how computers worked. … As modern computer technologies have become increasingly more complex, this clarity is all but lost.” Quoted from the textbook

How is it done?

// First Example in Programming 101 class Main {

function void main () {

do Output.printString("Hello World");

do Output.println(); // New line return;

}

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Main secret of computer science

Don’t worry about the “how”

Only about the “what”

• Extremely complicated system

• Information hiding

implementation

abstraction

what our programming language promises to do

Main secret of computer science

Don’t worry about the “how”

But, someone has to, for example, you.

Goal of the course

“The best way to understand how computers work is to build one from scratch.” Quoted from the textbook

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

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TOY machine TOY machine

• Starting from a simple construct

Logic gates

NOT _AND

OR

Components

PC

Registers

W W Data

A Data

B Data W Addr A Addr B Addr

+

1

Memory

W W Data Addr

R Data

IR

op d s t

A L U Cond

Eval

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25

Toy machine

PC

Registers

W W Data

A Data

B Data W Addr A Addr B Addr

+

1-bit counter 1

5 2

4

=0

>0

Opcode Execute Fetch Clock Memory

W W Data Addr

R Data

IR

op d s t

Cond Eval

A L U

Control

Clock

10

10 0

1 10

1001 00

TOY machine

• Almost as good as any computers

TOY machine

A DUP 32

lda R1, 1 lda RA, A lda RC, 0 read ld RD, 0xFF

bz RD, exit add R2, RA, RC sti RD, R2 add RC, RC, R1 bz R0, read exit jl RF, printr

hlt int A[32];

i=0;

Do { RD=stdin;

if (RD==0) break;

A[i]=RD;

i=i+1;

} while (1);

printr();

10: C020 20: 7101 21: 7A00 22: 7C00 23: 8DFF 24: CD29 25: 12AC 26: BD02 27: 1CC1 28: C023 29: FF2B 2A: 0000

TOY machine

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From NAND to Tetris

• The elements of computing systems

• Courses

• Software

• Cool stuffs

Pong on the Hack computer

Pong, 1985 Pong, 2011

Pong, on our computer

Theme and structure of the book

Assembler Chapter 6 H.L. Language

&

Operating Sys.

abstract interface

Compiler

Chapters 10 - 11

VM Translator Chapters 7 - 8

Computer Architecture Chapters 4 - 5

Gate Logic

Chapters 1 - 3 Electrical

Engineering

Physics Virtual

Machine abstract interface

Software hierarchy

Assembly Language abstract interface

Hardware hierarchy

Machine

Language abstract interface

Hardware Platform abstract interface

Chips &

Logic Gates abstract interface Human

Thought

Abstract design Chapters 9, 12

(Abstraction–implementation paradigm)

Application level: Pong (an example)

Ball abstraction

Bat

abstraction

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The big picture

&

Operating Sys.

abstract interface

Compiler

Chapters 10 - 11

Gate Logic

Engineering

Physics Virtual

Software hierarchy

Hardware hierarchy

Machine

Chips &

Thought

High-level programming (Jack language)

/** A Graphic Bat for a Pong Game */

class Bat {

field int x, y; // screen location of the bat's top-left corner field int width, height; // bat's width & height

// The class constructor and most of the class methods are omitted

/** Draws (color=true) or erases (color=false) the bat */

method void draw(boolean color) { do Screen.setColor(color);

do Screen.drawRectangle(x,y,x+width,y+height);

return;

}

/** Moves the bat one step (4 pixels) to the right. */

method void moveR() {

do draw(false); // erase the bat at the current location let x = x + 4; // change the bat's X-location

// but don't go beyond the screen's right border if ((x + width) > 511) {

let x = 511 - width;

}

do draw(true); // re-draw the bat in the new location return;

} }

Ball abstraction

Bat abstraction

Typical call to an OS method

Operating system level (Jack OS)

/** An OS-level screen driver that abstracts the computer's physical screen */

class Screen {

static boolean currentColor; // the current color

// The Screen class is a collection of methods, each implementing one // abstract screen-oriented operation. Most of this code is omitted.

/** Draws a rectangle in the current color. */

// the rectangle's top left corner is anchored at screen location (x0,y0) // and its width and length are x1 and y1, respectively.

function void drawRectangle(int x0, int y0, int x1, int y1) { var int x, y;

let x = x0;

while (x < x1) { let y = y0;

while(y < y1) {

do Screen.drawPixel(x,y);

let y = y+1;

}

let x = x+1;

} } }

Ball abstraction

Bat abstraction

The big picture

&

Operating Sys.

abstract interface

Compiler

Chapters 10 - 11

Gate Logic

Engineering

Physics Virtual

Software hierarchy

Hardware hierarchy

Machine Language abstract interface

Chips &

Thought

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A modern compilation model

. . .

RISC machine

VM language

other digital platforms, each equipped with its VM implementation RISC

machine language

computerHack Hack machine language CISC

machine language

CISC machine

. . .

Projects 10-11

written in a high-level

language

Any computer

. . .

VM implementation

over CISC platforms

VM imp.

over RISC platforms

VM imp.

over the Hack platform VM

emulator Some Other

language

Jack language

compilerSome Some Other compiler

compilerJack

. . .

Projects 7-8 Some

language

. . .

Projects 1-6 Proj. 9: building an app.

Proj. 12: building the OS

Compilation 101

Observations:

 Modularity

 Abstraction / implementation interplay

 The implementation uses abstract services from the level below.

parsing Code

generation Source code

(x + width) > 511

Abstraction

push x push width add push 511 gt

Intermediate code

Implementation Syntax

Analysis Parse

Tree Semantic

Synthesis width

x

+ 511

>

The virtual machine (VM modeled after JVM)

// VM implementation push x // s1 push width // s2 add // s3 push 511 // s4 gt // s5 if-goto L1 // s6 goto L2 // s7 L1:

push 511 // s8 push width // s9 sub // s10 pop x // s11 L2:

...

if ((x+width)>511) { let x=511-width;

}

75 450

sp

memory (before)

s2

450 ...

x width

75 ...

...

525 511

sp

1

sp

511 450

sp

s4 s5 s9

61

sp

s10

450 ...

x width

61 ...

...

memory (after)

The big picture

&

Operating Sys.

abstract interface

Compiler

Chapters 10 - 11

Gate Logic

Engineering

Physics Virtual

Software hierarchy

Hardware hierarchy

Chips &

Thought

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Low-level programming (on Hack)

...

push x push width add push 511 gt if-goto L1 goto L2 L1:

push 511 push width sub pop x L2:

...

Virtual machine program

Low-level programming (on Hack)

...

// push 511

@511

D=A // D=511

@SP A=M

M=D // *SP=D

@SP

M=M+1 // SP++

Virtual machine program

Assembly program

VM translator

push 511

Low-level programming (on Hack)

...

// push 511

@511

D=A // D=511

@SP A=M

M=D // *SP=D

@SP

M=M+1 // SP++

Virtual machine program

Assembly program

0000000000000000 1110110010001000

Executable

VM

translator

Assembler push 511

@SP

M=M+1 // SP++

The big picture

&

Operating Sys.

abstract interface

Compiler

Chapters 10 - 11

Gate Logic

Engineering

Physics Virtual

Software hierarchy

Hardware hierarchy

Chips &

Thought

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Machine language semantics (Hack)

Code syntax

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1 1 1 1 1 1 0 1 1 1 0 0 1 0 0 0 Instruction code

(0=“address” inst.) Address

ALU operation code

(M-1)

Destination Code

(M)

Jump Code (no jump)

Code semantics

, as interpreted by the Hack hardware platform

Instruction code (1=“compute” inst.) 0000000000000000

1111110111001000

@0 M=M-1

• We need a hardware architecture that realizes this semantics

• The hardware platform should be designed to:

o Parse instructions, and o Execute them.

Computer architecture (Hack)

• A typical Von Neumann machine

Data Memory

(M)

ALU

Instruction Memory

instruction

A D

M

Program Counter

address of next instruction

data in

data out

RAM(A)

The big picture

&

Operating Sys.

abstract interface

Compiler

Chapters 10 - 11

Gate Logic

Engineering

Physics Virtual

Software hierarchy

Hardware hierarchy

Machine

Chips &

Thought

Logic design

• Combinational logic (leading to an ALU)

• Sequential logic (leading to a RAM)

• Putting the whole thing together (leading to a computer)

Using … gate logic

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Gate logic

a Xor

b out

0 0 0 0 1 1 1 0 1 1 1 0 a b out

Interface

And

And Not

Or out

a

b

Not

Implementation

 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.

Hardware description language (HDL)

And

And Not

Or out

a

b

Not

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);

}

The tour ends:

0 0 1 0 1 1 1 0 1 1 1 0 a b out a out

b Nand

Interface One implementation option (CMOS)

Electronics Digital System Design

Computer Architecture

Operating System

Compiler

The tour map, revisited

&

Operating Sys.

abstract interface

Compiler Chapters 10 - 11

Gate Logic

Engineering

Physics Virtual

Software hierarchy

Hardware hierarchy

Chips &

Thought

Course overview:

Building this world, from the ground up

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with slides by Nisan & Schocken (www.nand2tetris.org)

Course overview

Introduction to Computer Yung-Yu Chuang