ICS丨Chapter 1 Introduction to Computer System

Chapter 1 Introduction to Computer System

Courses About Systems:

1. DBMS
2. Distributed Systems
3. Compilers
4. Architecture
5. Operating Systems
6. e.t.c.

• 1. Brief Introduction
  • 1.1. What’s about CSAPP?
  • 1.2. Power of Abstraction
  • 1.3. Importance of understanding HOW things work
• 2. Class 1 Notes : Bits,Bytes and Integers
  • 2.1. Representing data as bits
  • 2.2. Bit-level manipulations
  • Integers
    • Representation : unsigned and signed

1. Brief Introduction

This part is about CSAPP Chapter 1

1.1. What’s about CSAPP?

1. System Knowledge
   • How hardware and software work together
2. Useful outcomes

1.2. Power of Abstraction

1. tiers of computer system
   • Software
     • Application
     • System Software
   • Hardware
2. Proper Abstraction
   • Hardware
     • Processor
     • Main memory
     • I/o devices
   • 1-3 Processes
     如何在进程之间切换？
     进程内容之间是如何组织的？——虚拟内存
   • 2-3 Virtual Memory
   • 3-3 Files

1.3. Importance of understanding HOW things work

1. Why?
   • Not only abstraction, but also reality
2. Most CS courses emphasize abstraction
   • Abstract data types
   • Asymptotic analysis(渐进分析)

2. Class 1 Notes : Bits,Bytes and Integers

CSAPP Chapter 2 信息的表示和处理
续Class 2 Notes

2.1. Representing data as bits

Bits:

• Each bit is 0 or 1
• Why bits? Electronic Implementation(电子实现)
  • Easy to store with bistable elements(双稳元件)
  • Reliably transmitted on noisy and inaccurate wires

What is Byte:

• 1 Byte = 8 bits
  • Binary $$00000000_{2}to11111111_2$$
  • Decimal $$0_{10}to255_{10}$$
  • Hexadecimal $$00_{16}toF{F}_{16}$$

Hexadecimal Reference Table

Decimal	Hexadecimal	Binary
0	0	0000
1	1	0001
2	2	0010
3	3	0011
4	4	0100
5	5	0101
6	6	0110
7	7	0111
8	8	1000
9	9	1001
10	A	1010
11	B	1011
12	C	1100
13	D	1101
14	E	1110
15	F	1111

2.2. Bit-level manipulations

boolean algebra(布尔代数)

General Operators:
& | ^ ~
Shift Operation(移位运算):
<< >>(移位运算符)

Contrast: Logic Operations in C

• Contrast to Bit-Level Operators
  • Logic Operations:
    && || !
    • View 0 as False
    • Anything nonzero is True
    • Always return 0 or 1
• Examples:
  • !0x41 = 0
  • !0x00 = 1
  • !!0x41 = 1
  • p && *p ( avoid null pointer dereference(避免空指针解引用) )

Problem : Symmetric Difference(对称差) ? P15

Integers

Representation : unsigned and signed

unsigned and signed

Important Concept : Two's Complement(补码)