CHAPTER TWO ： Computer Hardware

1. CHAPTER TWO：Computer Hardware 第2章：计算机硬件

2. Table Of Contents Data Representation and Digital Electronics 2.1 Microprocessors and Memory 2.2 Storage Devices 2.3 Input and Output Devices 2.4

3. Data Representation and Digital Electronics • How is it that a computer can work with documents, photos, videos, and sound recordings? • The answer to that question is what data representation and digital electronics are all about. Data representation makes it possible to convert letters, sounds, and images into electrical signals. Digital electronics makes it possible for a computer to manipulate simple "on" and "off" signals to perform complex tasks.

4. Data Representation and Digital Electronics 2.1.1 Digital Data Representation 2.1.2 Quantifying Bits and Bytes 2.1.3 Digital Electronics

5. Data Representation and Digital Electronics 2.1.1 Digital Data Representation • Why are computers digital? • Most computers are digital, as opposed to analog, devices. A digital device works with discrete—distinct or separate—data or digits, such as 1 and 0. An analog device works with continuous data. - 大多数的计算机都是数字设备，这是相对于模拟设备来说的。数字设备使用的是离散的（个别的、分离的）数据或数字，如1和0。 模拟设备使用的是连续型数据。

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7. Data Representation and Digital Electronics • Most computers use the simplest type of digital technology—their circuits have only two possible states ("on" and "off").When discussing these states, we usually indicate the "on" state with 1 and the "off" state with 0. These 1s and 0s are referred to as binary digits. - 大多数的计算机都采用数字技术这种最简单的形式——它们的电路只有两种可能的状态(“开”和“关”)。在讨论这两种状态时，我们通常用1表示“开”状态，用0表示“关”状态。这些 1和0就是二进制数字。

8. Data Representation and Digital Electronics • How can a computer represent numbers using bits? • Computers represent numeric data using the binary number system, also called "base 2".The binary number system has only two digits: 0 and 1. - 计算机使用二进制数字系统（亦称“基2”）来表示数字型数据。二进制数字系统只有 两种数字：0和1。

9. Data Representation and Digital Electronics • The binary number system allows computers to represent virtually any number simply by using 0s and 1s, which conveniently translate into electrical "on" and "off" signals. - 二进制数字系统能够让计算机仅用若干的 0和1就能表示几乎任何的数字，而且它们 可以被很方便的转变成电信号的“开”和“关”状态。

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11. Data Representation and Digital Electronics 计算机技术领域中常用的几种进制 在计算机内部使用的是二进制，因为二进制：可靠性、可行性、简易性、逻辑性

12. Data Representation and Digital Electronics • How can you convert a number from base r (r=2,8,16) to base 10? - 方法：r进制数的数符乘以相对应的位权， 然后把各个乘积加（十进制加法）起来。 - 举例： 10101(B)=1*24+0*23+1*22+0*21+1*20=21 101.11(B)=1*22+0*21+1*20+1*2-1+1*2-2=5.75 101(O)=1*82+0*81+1*80=65 71.4(O)=7*81+1*80+4*8-1=57.5 1A2F(H)=1*163+10*162+2*161+15*160=6703

13. Data Representation and Digital Electronics • How can you convert a number from base 10 to base r (r=2,8,16)? - 方法：整数部分除以r取余数，直到商为0，余数从右到左排列；小数部分乘以r取整数，整数从左到右排列。 - 举例： 100.345(D)=1100100.01011(B) 100(D)=144(O)=64(H)

14. 0.345 ╳ 2 … 0 100 2 … 0 低位 2 50 高位 … 1 25 2 ╳ 2 1.380 … 0 12 2 … 0 6 0.760 ╳ 2 2 … 3 1 2 … 2 1 1 0 高位 1.04 低位 Data Representation and Digital Electronics 0.690 ╳ 2 1.520 ╳ 2 100.345(D) = 1100100.01011(B)

15. Data Representation and Digital Electronics • How can you convert a number from base 8 or base 16 to base 2? - 方法：八进制数的每一位对应二进制的三位，十六进制数的每一位对应二进制的四位。 - 举例： 7123(O) = 111001010011 (B) 7 1 2 3 144.65(O) = 001100100.110101 (B) 1 4 4 6 5 2C1D(H) = 0010110000011101 (B) 2 C 1 D

16. Data Representation and Digital Electronics • How can you convert a number from base 2 to base 8 or base 16? - 方法：二进制数的整数部分从右向左进行 分组，小数部分从左向右进行分组。转换成 八进制3位一组，转换成十六进制4位一组，不足补零。 - 举例： 1101101110.110101 (B) = 1556.65(O) 1 5 5 6 6 5 1101101110.110101 (B) = 36E.D4(H) 3 6 E D 4

17. Data Representation and Digital Electronics • How can a computer represent words and letters using bits? • Character data is composed of letters, symbols, and numerals. Computers employ several types of codes to represent character data, including ASCII, EBCDIC, and Unicode. - 字符型数据是由字母、符号和数字组成。计算机使用多种代码来表示字符型数据，包括ASCII码、EBCDIC码和Unicode码。

18. Data Representation and Digital Electronics • ASCII码 美国标准信息交换码 - 用7个二进制位表示一个字符，可以为128个 字符提供编码 • 扩展型ASCII码 - 用8个二进制位表示一个字符，可以为256个 字符提供编码 • EBCDIC码 扩展型二进制表示的十进制交换码 - 使用8个二进制位，为256个字符提供编码 • Unicode码 - 使用16个二进制位，为65000个字符提供编码

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20. Data Representation and Digital Electronics • Why does ASCII provide codes for 0,1,2,3,4,5,6,7,8,and 9? • Computers sometimes distinguish between numeric data and numerals. A computer uses the ASCII code numerals for numerical symbols, whereas it uses a binary number to code numeric data. - 有时计算机要把数字型数据和数码区分开来。计算机使用ASCII编码的数码来表示数字符号，使用二进制数字对数字型数据进行编码。

21. Data Representation and Digital Electronics • How does a computer convert sounds and pictures into codes? • To work with sounds and pictures, a computer must somehow digitize them into 1s and 0s. Computers convert colors and sounds into numbers, which can be represented by bits. - 计算机要使用声音和图片的话，就必须先把它们数字化为1和0的序列，即要把颜色和声音转变成能够用位序列表示的数字。

22. Data Representation and Digital Electronics • When a computer works with a series of 1s and 0s, how does it know which code to use? • To avoid confusion, most computer files contain a file header with information on the code that was used to represent the file data. - 为了防止混淆，大多数的计算机文件都带有一个文件头，其中包含着关于文件中数据所采用的编码的信息。

23. Data Representation and Digital Electronics 2.1.2 Quantifying Bits and Bytes • How can I tell the difference between bits and bytes? • The word "bit“ (abbreviation for "binary digit“) can be further abbreviatedas a lowercase "b".A byte, on the other hand, is composed of eight bits and is usually abbreviated as an uppercase "B". - “位”(“二进制数字”的缩写)可被进一步缩写为一个小写的“b”；另一方面，一个字节由8个 位构成，通常被缩写成一个大写的“B”。

24. Data Representation and Digital Electronics • Transmission speeds are usually expressed in bits, whereas storage space is usually expressed in bytes. - 传输速度通常用位来表示，而存储容量通常用字节表示。 - For Example • Modem’s speed: 56 Kbps —56 kilobits per second • The capacity of a hard disk drive: 8 GB —8 gigabytes

25. Data Representation and Digital Electronics • What do the prefixes kilo-, mega- and giga- mean? • In the context of bits and bytes, "Kilo" is a prefix that means 210 (1024). The prefix "mega" refers to 220 (1048576). The prefix “giga" refers to 230. - 对位和字节来说，“kilo”作为前缀代表210，前缀“mega”指的是220，前缀“giga”指的是230 。

26. Data Representation and Digital Electronics • A kilobit (abbreviated Kb or Kbit) is 1024 bits and a kilobyte (abbreviated KB or Kbyte) is 1024 bytes. - 1Kb=1024b; 1KB=1024B • A megabit (abbreviated Mb or Mbit) is 1024 Kilobits (220 bits) and a megabyte (abbreviated MB or Mbyte) is 1024 kilobytes (220 bytes). - 1Mb=1024Kb=220b; 1MB=1024KB=220B

27. Data Representation and Digital Electronics 2.1.3 Digital Electronics • How does a computer store and transport all of those bits? • Because most computers are electronic devices, bits take the form of electrical pulses that can travel over circuits. - 由于大多数的计算机都是电子设备，所以 位序列都是以电子脉冲的形式在电路之中 传输的。

28. Data Representation and Digital Electronics • Does a typical computer owner need to mess around inside the system unit? - 由于采用了digital electronic technology使元件的小型化成为可能，现在的计算机才只包括很少的组成部分。 - 桌面计算机只需在系统单元内部添加或替换一些元件就能获得所需的功能。 - 笔记本电脑则在机箱外部提供了扩展和替换功能。

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30. Data Representation and Digital Electronics • What's a computer chip? • The terms "computer chip", "microchip", and "chip" originated as technical jargon for "integrated circuit." - “计算机芯片”、“微芯片”和“芯片”这些词原来是集成电路技术使用的专业术语。

31. Data Representation and Digital Electronics • An integrated circuit (IC) is a super thin slice of semiconducting material (or "semiconductors") packed with microscopic circuit elements such as wires, transistors, capacitors, logic gates, and resistors. - 集成电路是一种超薄的半导电性物质（或称“半导体”），它的表面上堆列着许多微小的电路元件，如电线、晶体管、电容、逻辑门和电阻。

32. Data Representation and Digital Electronics • The assortment of chips inside of a computer includes the microprocessor, memory modules, and support circuitry. - 计算机内部芯片的种类包括微处理器、内存 单元及支撑电路。 - 芯片封装的形状、大小各不相同，常见的有： • 双列直插式封装 DIP (Dual In-line Package) • 双列内置存储模型 DIMM (Dual In-line Memory Module) • 针网阵列 PGA (Pin-Grid Array) • 单列直插盒 SEC cartridge • (Single Edge Contact cartridge)

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34. Data Representation and Digital Electronics • How do chips fit together to make a computer? • The computer's main circuit board, called a motherboard or "main board", houses all essential chips and provides connecting circuitry between them. - 计算机的主要电路板称为母板或“主板”， 上面安放着所有的重要芯片并提供了芯片 之间的连接电路。

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36. Microprocessors and Memory 2.2.1 Microprocessor Basics 2.2.2 Microprocessor Performance Factors 2.2.3 Today’s Microprocessors 2.2.4 Random Access Memory 2.2.5 Read-only Memory 2.2.6 CMOS Memory

37. Microprocessors and Memory 2.2.1 Microprocessor Basics • Exactly what is a microprocessor? • A microprocessor (sometimes simply referred to as a “processor”, usually described as "a CPU on a chip") is an integrated circuit designed to process instructions. - 微处理器（有时简称“处理器”，通常被描述为“基于一块芯片上的CPU”）是一种用于执行指令的集成电路。

38. Microprocessors and Memory • What does a microprocessor look like? • Depending on the brand and model, a microprocessor might be housed in an SEC cartridge or in a square PGA. - 牌子和型号不同，微处理器的外观也不同，它可能被封装在单列直插盒(SEC)中，也可能被装在正方形的针网阵列(PGA)中。

39. Microprocessors and Memory • Inside the chip carrier, a microprocessor is a very complex integrated circuit, containing as many as 300 million miniaturized electronic components. Some of these components are only 30 nanometers thick. A nanometer is one billionth of a meter. - 封装内部的微处理器芯片是一种非常复杂 的集成电路，包括3亿个微小的电子元件。其中的一些元件只有30nm那么厚。1nm指 的是一米的十亿分之一。

40. Microprocessors and Memory 微处理器内部的微型化电路分别构成了 一些重要的功能区域，包括： • 算术逻辑单元 ALU (Arithmetic Logic Unit) - 也称“运算器”，主要完成算术和逻辑运算， 实现对数据的加工和处理。在运算过程中，ALU用寄存器(register)保存要处理的数据。 • 控制单元 Control Unit - 也称“控制器”，用于控制整个计算机的各个 部分自动协调地工作，它的基本功能就是从内存取指令并执行指令。

41. Microprocessors and Memory • Where does the microprocessor get its instructions? • A microprocessor executes instructions that are provided by a computer program. The list of instructions that a microprocessor can perform is called its instruction set. These instructions are hard-wired into the processor‘s circuitry. - 微处理器执行的指令是由计算机程序提供。微处理器能够执行的指令列表称为指令集合。这些指令被固化在处理器的电路中。

43. Microprocessors and Memory • What happens when a computer executes an instruction? • The term instruction cycle refers to the process in which a computer executes a single instruction. - 指令周期指的是计算机执行一条单指令的 过程。 - 一个指令周期包括四个活动：取指令、解释指令、执行指令和形成下一条指令地址。

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45. Microprocessors and Memory 2.2.2 Microprocessor Performance Factors • What makes one microprocessor perform better than another? • The performance of a microprocessor is affected by several factors, including clock speed, word size, cache size, instruction set, and processing techniques. - 微处理器的性能受到若干因素的影响，包括时钟频率、字长、高速缓冲容量、指令集合 和处理技术。

46. Microprocessors and Memory • What do MHz and GHz have to do with computer performance? • The speed specifications that you see in a computer ad indicate the speed of the microprocessor clock— a timing device that sets the pace for executing instructions. - 计算机广告中所说的速度指的是微处理器 时钟的速度。微处理器的时钟是一种计时 设备，用来设置指令执行的速度。

47. Microprocessors and Memory • Most computer ads specify the speed of a microprocessor in megahertz (MHz) or gigahertz (GHz). Megahertz means a million cycles per second. Gigahertz means a billion cycles per second. - 大多数的计算机广告中用兆赫兹和吉赫兹来具体说明微处理器的速度。兆赫兹意味着计算机每秒能够执行一百万(106)个时钟周期。吉赫兹意味着计算机每秒能够执行十亿(109)个时钟周期。

48. Microprocessors and Memory • 时钟周期(clock cycle)指的是微处理器执 行一条加法指令所需要的时间，由CPU的 时钟频率（主频）确定。它是微处理器领域内最小的时间单位。 - 假设某CPU的主频为1GHz (Hz:每秒次数，表示事件发生的频率)，它的意思是指微处理器的时钟每秒能运行10亿个周期，则它的时钟周期为：1s/109 = 10-9s = 1ns • 注意：时钟的速度和每秒微处理器能够执行的指令数并不相一致。

49. Microprocessors and Memory • Which is faster, an 8-bit processor or a 64-bit processor? • Word size refers to the number of bits that a microprocessor can manipulate at one time. Processors with a larger word size can process more data during each processor cycle, a factor that leads to increased computer performance. - 字长指的是微处理器能够同时处理的位的个数。有更大的字长的处理器能够在每个处理器周期内处理更多的数据，因此字长 越长计算机性能越好。

50. Microprocessors and Memory • How does the cache size affect performance? • Cache is sometimes called "RAM cache" or "cache memory“. It is special high-speed memory that allows a microprocessor to access data more rapidly than from memory located elsewhere on the motherboard. - 缓存有时也称为“RAM缓存”或“缓冲存储器”，它是一种特殊的高速内存，与安装在主板上其他位置的内存相比，它能够使微处理器更 快的获得数据。