Introduction: From Nand to Tetris

Transcription

1 Introduction: From Nand to Tetris Building a Modern Computer From First Principles Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 1

2 Usage and Copyright Notice: Copyright Noam Nisan and Shimon Schocken This presentation accompanies the textbook The Elements of Computing Systems by Noam Nisan & Shimon Schocken, MIT Press, We provide 13 such presentations. Each presentation is designed to support about 3 hours of classroom or self-study instruction. You are welcome to use or edit this presentation as you see fit for instructional and noncommercial purposes. If you use our book and course materials, please include a reference to If you have any questions or comments, please write us at nand2tetris@gmail.com This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 2

3 Course theme and structure Human Thought Abstract design Chapters 9, 12 H.L. & Operating Sys. Compiler Chapters Virtual Software VM Translator Chapters 7-8 Assembly Assembler Chapter 6 Computer Architecture Chapters 4-5 Platform Gate Logic Chapters 1-3 Chips & Logic Gates Electrical Engineering Physics (Abstraction implementation paradigm) Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 3

4 Application level: Pong (example app) Ball abstraction Bat abstraction Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 4

5 The big picture Human Thought Abstract design Chapters 9, 12 H.L. & Operating Sys. Compiler Chapters Virtual Software VM Translator Chapters 7-8 Assembly Assembler Chapter 6 Computer Architecture Chapters 4-5 Platform Gate Logic Chapters 1-3 Chips & Logic Gates Electrical Engineering Physics Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 5

6 High-level programming (our very own 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; } Typical call to an OS method } /** 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 = width; } do draw(true); // re-draw the bat in the new location return; } Ball abstraction Bat abstraction Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 6

7 Operating system level (our very own 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 Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 7

8 The big picture Human Thought Abstract design Chapters 9, 12 H.L. & Operating Sys. Compiler Chapters Virtual Software VM Translator Chapters 7-8 Assembly Assembler Chapter 6 Computer Architecture Chapters 4-5 Platform Gate Logic Chapters 1-3 Chips & Logic Gates Electrical Engineering Physics Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 8

9 A modern compilation model Some... language Some Other language... Jack language Proj. 9: building an app. Proj. 12: building the OS Some compiler Some Other compiler Jack compiler Projects VM language VM implementation over CISC platforms VM imp. over RISC platforms VM emulator VM imp. over the Hack platform Projects 7-8 CISC machine language RISC machine language... written in a high-level language Hack machine language Projects 1-6 CISC machine RISC machine other digital platforms, each equipped with its VM implementation Any computer Hack computer Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 9

10 Compilation 101 > Intermediate code Source code push x (x + width) > 511 parsing Code generation push width add push 511 gt x width Abstraction Syntax Analysis 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, Introduction slide 10

11 The Virtual (our very own VM, modeled after Java s JVM) if ((x+width)>511) { let x=511-width; } // VM implementation push x // s1 width x memory (before) sp s push width // s2 add // s3 s4 s5 s9 push 511 // s4 gt // s5 if-goto L1 // s6 goto L2 // s7 sp sp 1 sp L1: L2: push 511 // s8 push width // s9 sub // s10 pop x // s11 sp s10 61 width x memory (after) Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 11

12 The big picture Human Thought Abstract design Chapters 9, 12 H.L. & Operating Sys. Compiler Chapters Virtual Software VM Translator Chapters 7-8 Assembly Assembler Chapter 6 Computer Architecture Chapters 4-5 Platform Gate Logic Chapters 1-3 Chips & Logic Gates Electrical Engineering Physics Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 12

13 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, Introduction slide 13

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: VM translator Assembly program // push D=A // A=M M=D // M=M+1 // SP++ Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 14

15 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: VM translator Assembly program // push D=A // A=M M=D M=M+1 // SP++ Assembler Executable Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 15

16 The big picture Human Thought Abstract design Chapters 9, 12 H.L. & Operating Sys. Compiler Chapters Virtual Software VM Translator Chapters 7-8 Assembly Assembler Chapter 6 Computer Architecture Chapters 4-5 Platform Gate Logic Chapters 1-3 Chips & Logic Gates Electrical Engineering Physics Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 16

17 language semantics (our very own Hack platform) For now, ignore all details! Code semantics, as interpreted by the Hack hardware platform Instruction code (0= address inst.) Address Code syntax M=M Instruction code (1= compute inst.) 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, Introduction slide 17

18 Computer architecture (Hack platform, approx.) For now, ignore all details! instruction Instruction Memory D A M ALU data out Data Memory (M) Program Counter address of next instruction data in RAM(A) A typical Von Neumann machine Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 18

19 The big picture Human Thought Abstract design Chapters 9, 12 H.L. & Operating Sys. Compiler Chapters Virtual Software VM Translator Chapters 7-8 Assembly Assembler Chapter 6 Computer Architecture Chapters 4-5 Platform Gate Logic Chapters 1-3 Chips & Logic Gates Electrical Engineering Physics Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 19

20 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. Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 20

21 Gate logic 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. Interface Implementation a b Xor out a Not And a b out Or out b Not And Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 21

22 Description (HDL) a Not And Or out b Not 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, Introduction slide 22

23 The tour ends: Interface One implementation option (CMOS) a b Nand out a b out Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 23

24 The tour map, revisited Human Thought Abstract design Chapters 9, 12 Computer Architecture Chapters 4-5 H.L. & Operating Sys. Platform Compiler Chapters Assembler Chapter 6 Gate Logic Chapters 1-3 Virtual Software VM Translator Chapters 7-8 Course overview: Building this world, from the ground up Chips & Logic Gates Electrical Engineering Assembly Physics Elements of Computing Systems, Nisan & Schocken, MIT Press, Introduction slide 24