大学计算机基础复习资料-双语教学英文版.doc

计算机复习资料最终定稿版Ji suan ji fu xi zi liao zui zhong ding gao ban1.key words of Definition for computer: instructions,input,processes ,outputA computer is an electronic device which operates under the control of stored instructions accepts data input processes the data according to specified rules produces and stores output1、A computers power is derived from Speed Reliability Accuracy Storage Communications 2、Data: The symbols that represent people, events, things, and ideas. Consists of the raw, unprocessed facts, including text, numbers, images, and sounds.3、Information ：Data becomes information when it is presented in a format that people can understand and use .4information processing cycle：.input, process, output, and storage5Computing Technology (R)Evolution four generations Vacuum Tube （电子管）Age ，Transistor Age（晶体管） ，Integrated Circuit （集成电路）Age ，Large-scale Integration(大规模集成化) Age6.分类：Supercomputers (巨型计算机) fastest, most powerful, most expensiveMainframe computers（大型机）provide great processing speeds and data storage.Minicomputers （小型机）Microcomputers（微机）即 personal computer or PCleast powerful, but the most widely used.7. Information can be represented in one of two waysAnalog data（模拟） A continuous representation，analogous（相似） to the actual informationDigital data A discrete representation8. 1 Byte=8 bits，B, KB, MB, GB, TB):9. Binary（Base 2）Octal（8）Decimal（Base 10） Hexadecimal（16）0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F10.distinguish number system(1) Subscript(下标) (101)2 (101) 8（2）Postfix（后缀）101B 101O 101D 101H11. Converting numberNon-Decimal to DecimalDecimal to Non-Decimalv 102 integer整数（1）短除法（2）从高位到低位逆用210思想v Fraction小数Non-Decimal to Non-Decimal 28 (10 111 011.110 1)2 = (273.64)882 (6754.32)8 = (110 111 101 100. 011)2162 （A7B8.C9）16=(1010 0111 1011 1000 .1100 1001)？12. Binary Arithmetic 12original code (2n11) (2n11) Total number is2n1 n=8 -127 +127Pro：Simple & Direct Cons：Subtraction operation may fail （overflow）13Original code and Complement code, to do subtraction减法 in addition（补码的意义正在于把减法做成加法）§ For positive number：complement = original§ For negative number: Original: sign bit is 1, the rest is its absolute value Complement: reverse all digits except the sign, the plus 1§ Complement of complement = original14complement code 2n1 (2n11) Total number is 2n n=8, the range is: -128 +12715Floating point notation to represent very large real numbers and very small real numbers （1）-1.6875=(-1.1011)2=(-0.11011×21)2 （2）指数 尾数上数=0 0000001 1 11011000000000000000000 （用八位表示指数位，24位表示尾数位）？16In a 32 bits computer, if 8 bits for exponent part and 24 bits for mantissa part, the range of number is 1038 2-150 0 -1038 -2-15016Code of charactersASCII美国信息交换标准码 character setStandard 7-bits, with 128 charactersExtended 8-bits, with 256 charactersUnicode 16-bits, a superset超集 of ASCI17.von Neumannthree main ideas about computer *Five basic components *Use binary information *Stored program18The principle of stored program A couple of abilities: store program and then automatic execute program .（存储程序、自动执行程序）Computers use “memory” (primary memory主存) to store program which will be processedv 19Five basic components§ Control Unit§ Arithmetic/logic Unit (ALU) 运算器§ Input devices§ Output devices§ Storage primary and secondary storage19CPUcan fetch each instruction in that program from memory one by onedecode the informationGet data if neededand then execute the information until all instructions arefinished.巧记有一个全控制，有两个互相传数据和信息，有一个只入，有一个只出20 ALU（运算器）（arithmetic operation logical operations）-（register） CPU Control Unit（directs and coordinates使协调 operations in computer.）-register Random access memory (RAM) temporary or volatile storage Main memory Read-only memory (ROM) -BIOS Basic Input Output SystemMemory CMOS required every time the computer system is turned on Secondary Storage 外存 CPU不能直接访问注释1 CPU定义 Interprets（翻译） and carries out basic instructions that operate a computer 注释2 ROM cannot be changed 而CMOS can be changed to reflect changes in the computer system注释3 Memory used to store the most frequently accessed information stored in RAM cache, 21two registers in the control unit:The instruction register (IR) contains the instruction that is being executed.The program counter (PC) contains the address of the next instruction to be executed18#Two steps of a machine cycle: Instruction cycle and execution cycle22. CPU speed Clock rate Word size Cache Instruction set size（指令集大小） 23. Computers are electronic devices that accept instructions, process input, and produceinformation24.术语：Floppy disk 软盘 Optical disk/compact disk 光盘 Flash disk 闪存盘23System Unit (主机)v Motherboardv Processor CPU§ ALU§ Control Unitv Memory§ RAM, ROM, CMOS, Cache§ All data and instructions must be loaded into RAM before they can be executedv Bus data highway between devicesv Expansion slots/cards (扩展槽/卡) to add extra devices§ video card, sound card, network cardv Port (端口) a plug for a cable that leads to a device§ usb ports, RJ-45, VGA port for monitor OS24. 系统软件操作系统实用软件 外壳，命令解释程序 内核注释1Utility software fundamental to computer installations, but not part of the OS.注释2 shell provides an interface through which a human can interact with the computerkernel manages computer resources, such as memory and input/output device强调：System software定义 manage a computer system at a fundamental level25. Every operating system performs three basic functions：（different os also have other specific functions ）manages computer resources, such as 1. memory,2. CPU, and3. processesprovides an interface through which a human can interact with the computerallows an application program to interact with other system resources26. Managing Resources consists of:Memory managementProcess managementCPU scheduling26.1. Memory management optimizes（优化） the use of RAM26.2-1 A process can be defined as a program in execution.26.2-2 A single user operating system allows only one user to run one program at a time.A multiuser operating system enables two or more users to run a program simultaneously.A multitasking operating system allows a single user to work on two or more applications that reside in memory at the same time.A multiprocessing operating system can support two or more processors running programs at the same time.26.3 CPU SchedulingThe operating system determines which process in memory is executed by CPU Nonpreemptive scheduling 无优先调度Preemptive scheduling27.OTHER FUNCTIONS27.1 System Booting Cold boot&Warm bootThe process of starting or restarting a computer is called booting27.2 System Shutting DownSleep mode（睡眠）saves any open documents and programs to RAM, turns off all unneeded functions, and then places the computer in a low-power stateHibernate（休眠） saves any open documents and programs to a hard disk before removing power from the computerUser Interface Device Driver Network Support Performance Monitor System Update28. Types of Operating Systems28.1 A stand-alone operating system（独立操作系统） is a complete operating system that works on a desktop computer, notebook computer, or mobile computing device28.2 An embedded （嵌入式）operating system resides on a ROM chip on a mobile device or consumer electronic device29File A named collection of related dataFile is stored in secondary storage A file is a set of data that has been given a nameFile system The operating system's logical view of the files it manages Directory A named group of files. Also called a folder30File type Program files（程序文件） - contains instructions to tell the computer what to do.Microsoft Word, Photoshop, AutoCADData Files - not executable and only used with a program. Word document, text file, Excel file, PowerPoint fileText file A file in which the bytes of data are organized as characters from the ASCII or Unicode character setsBinary file A file that contains data in a specific format, requiring interpretation（翻译）31The root directory is typically identified by the device letter followed by a backslash(反斜线)32File managementWindows Explorer(资源管理器) Clipboard（剪贴板） Recycle Bin(回收站)33File Properties(属性)34Path Names Absolute path D:CoursesComputer2011OS.pptRelative path 2011OS.ppt Multimedia35Representing CharacterASCII （America Standard Code for Information Interchange）v Original ASCII uses 7 bits to code 128 charactersv Extended to 8 bits for 128 extra characters2. Unicodeuses 16 bits, can represent 216 = 6553436Representing Audiov Sound is generated by the vibration of airv Sound wave is analogv Computers convert sound to digits by samplingv A stereo sends an electrical signal to a speaker to reproduce soundA sampling rate of about 40,000 times per second is enough to create a reasonable sound reproductionAudio Formats§ WAV, AU, AIFF, VQF, and MP3 v MP3 is dominant§ MPEG-2, audio layer 3 file>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Graphics37Representing Images and Graphicsv Raster(光栅)-graphics§ The storage of image information is on a pixel-by-pixel（像素） basis§ Popular formats BMP (bitmap), GIF (Graphics Interchange Format), JPEG (Joint Photographic Experts Group)v Vector-graphics（矢量图）§ Describes an image in terms of lines and geometric shapes§ Include a series of commands that describe a lines direction, thickness, and colour.§ The file sizes tend to be smaller because not every pixel is described§38 A graph is treated as a matrix of dots, which is called pixelsv The number of pixels is called resolution（分辨率）39Color is expressed as an RGB (Red,Green,Blue) value three primary colors40Color depth§ The amount of data that is used to represent a color41TrueColor§ A 24-bit color depth: eight bits used for each number in an (R,G,B) value42Each pixel is normally recorded by three bytes, for red-green-blue respectively. Therefore, a pixel is written as (r, g, b), where 0 <= r,g,b <= 25543Resolution§ The number of pixels used to represent a picture 44In the resolution 800×600, an RGB true-color image needsv 800×600×3×8 bits = 1440KB = 1.4MB。45Common Graph FormatsBitmap format§ Contains the pixel color values of the image from left to right and from top to bottomv GIF format§ Each image is made up of only 256 colorsv JPEG format§ Averages color hues over short distancesv PNG format§ Like GIF but achieves greater compression with wider range of color depths46.Vector Graphics(向量图)§ A vector graphic is a series of commands that describe a lines direction, thickness, and color line(x1,y1,x2,y2,color) circle(x,y,r,color)The good sideVector graphics can be resized mathematically and unrestrictedThe bad sideVector graphics are not good for representing real-world imagesNeed CPU calculations>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Video47. Features of video§ Video consists of a sequence of pictures/frames§ Fast and continuous move of frames creates video§ FPS (Frames Per Second): 16fps gives satisfiable feeling§ Huge storage required Frame size× FPS × Video length 600×400 resolution, 1 minute video needs: 600×400×3×60×16 Byte = 691 MBData Compression（压缩）48Data compression is a reduction in the amount of space needed to store a piece of data.49Compression ratio（压缩率）§ Size of the compressed data / Size of the original data.50A data compression technique can be lossless（无损） or lossy（有损）v Lossless compression（无损压缩）§ Compression based on statistics or specific data structure. Common in text and certain application domains, such as medical imagesv Lossy compression（有损压缩）§ Discard some irrelevant（不相干的） or insensitive（不被感知的） information to cheat eyes or ears. Common for audio, images, and videos51Keyword EncodingFrequently used words are replaced with a single character.Note, that the characters used to encode cannot be part of the original text.52Run-Length EncodingSome examples:AAAAAAAwould be encoded as*A7？Since we are using one character for the repetition count, it seems that we cant encode repetition lengths greater than nine. However, instead of interpreting the count character as an ASCII digit, we could interpret it as a binary number.53Audio Compressionv MP3 employs both lossy and lossless compression § First analyzes the frequency spread and discards information that cant be heard by humans § Then the bit stream is compressed using a form of Huffman encoding to achieve additional compressionv The compression ratio for MP3 is usually 1:10 to 1:1254Image Compressionv 在RGB模式下有28*28*28 = 224 = 16,777,216种颜色，discarding information not sensitive to our eyes就有了压缩55. Video CompressionAlmost all video codec use lossy compressions56. 视频压缩两种形式Temporal（时间） compression v A technique based on differences between consecutive framesIf most of an image in two frames hasnt changed, why should we waste space to duplicate all of the similar information?Spatial compression A technique based on removing redundant information（冗余信息） within a frame: This problem is essentially the same as that faced when compressing still imagesSoftware Design57 包含关系：Software Programs Languagesv Language§ Set of symbols and rules about programming v Program§ Sequence of instruction for solving a problemv Software§ Collection of programs, as well as documents and data两大问题 一。Problem Solving 二。Algorithm Design 一 Problem Solving 过程2The computer problem-solving processa. Analysis and Specification Phase Analyze Specificationb. Algorithm Development Phase(开发阶段) Develop algorithm Test algorithmdImplementation Phase（实施阶段） Code algorithm Test algorithmdMaintenance Phase Use Maintain过程详述：1. Analysis and Specification Phase 2. Algorithm Development Phase阶段1.program specification also called program definition or program analysis 包括五部分1。 The program's objectives2.The desired output3.The input required4.The processing requirements5.The documentation 2. program design A solution is created using design techniques.The most widely used are structured programming