Course overview
Introduction to Computer Yung-Yu Chuang
with slides by Nisan & Schocken (www.nand2tetris.org)
Logistics
• Meeting time: 2:20pm-5:20pm, Tuesday
• Classroom: CSIE Room 101
• Instructor: 莊永裕 Yung-Yu Chuang
• Teaching assistant: 沈林承 魏敏家
• Webpage:
http://www.csie.ntu.edu.tw/~cyy/introcs
id / password
• Mailing list: introcs@cmlab.csie.ntu.edu.tw Please subscribe via
https://cmlmail.csie.ntu.edu.tw/mailman/listinfo/introcs/
Textbook
The Elements of Computing Systems, Noam Nisan,
Shimon Schocken, MIT Press
Nand2Tetris on Coursea
References (TOY)
Princeton’s Introduction to CS,
http://www.cs.princeton.edu/intro cs/50machine/
http://www.cs.princeton.edu/intro
cs/60circuits/
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
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
More “computers” around us
My computers
iPhone 6+
(A8, ARMv8-A) iPad 2
(dual-core A5 1GHz)
MacBook Air
(dual-core Intel Core i5, 1.3GHz) Desktop
(Intel Pentium D
3GHz, Nvidia 7900)
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;
}
}
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
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
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
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
The big picture
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
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
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
A modern compilation model
. . .
RISC machine
VM language
other digital platforms, each equipped with its VM implementation RISC
machine language
Hack computer
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
Some
compiler Some Other compiler
Jack compiler
. . .
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
spmemory (before)
s2450
...
x width
75
...
...
525 511
sp1
sp511 450
sps4 s5 s9
61
sps10
450
...
x width
61
...
...
memory (after)
The big picture
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
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 x push width add
push 511 gt
if-goto L1 goto L2 L1:
push 511 push width sub
pop x L2:
...
// 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 x push width add
push 511 gt
if-goto L1 goto L2 L1:
push 511 push width sub
pop x L2:
...
// 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
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
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 platformInstruction 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
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
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
Gate logic
Xor a
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
out a
b Nand
Interface One implementation option (CMOS)
Electronics Digital System Design
Computer Architecture
Operating System
Compiler
The tour map, revisited
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
Course overview:
Building this world, from the ground up
