Chapter 1
generations of computer
- Vacuum Tubes
- Transistors
- SSI/MSI circuits
- LSI/VLSI circuit
Components of CPU
- Register
- Control Unit
- ALU (Arithmetic Logic Unit)
Components of hardware
- calculator
- memory
- controller
- I/O devices
BASIC FEATURE of Von Neumann : access memory by address and execute instruction in sequence
The operating system is appeared in the 3rd generation computers
Computer hardware consists of calculator, memory, controller and I/O devices.
System program: operating system, compiler, or utility program
machine language and assembly language can be implemented directly
The Art of Managing Complexity
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Abstraction
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Discipline
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The Three-Y’s
–Hierarchy
–Modularity
–Regularity
Abstraction
- Hiding unimportant details
- Professionals handle professional issues
Discipline
Intentionally restrict for design choices
The Three-Y’s
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Hierarchy(层次化)
A system divided into modules
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Modularity(模块化)
Having well-defined functions and interfaces
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Regularity(规整化)
Encouraging uniformity, so modules can be easily reused
The Digital Abstraction
Digital abstraction considers discrete subset of values.
- Focus on 0 and 1
- Ignore physical meanings
- make low level abstraction
The Analytical Engine
- Charles Babbage
- first digital computer
- Built from mechanical gears, where each gear represented a discrete value (0-9)
- Babbage died before it was finished
Number Systems
Decimal numbers
小数的表示
Binary numbers
Hexadecimal numbers
(0～15) ：0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
Conversion
Bits, Bytes, Nibbles
Overflow
Overflow judgement
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SA SB Sf
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Cf C
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double sign bit
Data types
Signed Binary Numbers
•‘0’ for positive number
•‘1’ for negative number
•A separate sign bit is placed at msb position
Sign-Magnitude Numbers（原码）
+6 =0110
-6 =1110
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Addition doesn’t work!!!
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Two representations of 0 (± 0)
Range : 
Two’s Complement Numbers（补码）
The most significant bit still indicates the sign (1 = negative, 0 = positive)
Range: 
How to flip the sign?
1.Invert the bits
2.Add 1
补码转换成原码：首位是1，符号位不变，后面的取反之后加一；首位是0，不变
One’s complement representation(反码）
正数的反码是它本身，负数的反码符号位不变，其余取反
Increasing Bit Width
Sign-Extension
•Sign bit copied to msb’s
•Number value is same
Example
Zero-Extension
•Zeros copied to msb’s
•Value changes for negative numbers
Logic Gates
Single-Input Logic Gates
Two-Input Logic Gates
