《计算机专业英语》.ppt

计算机专业英语,第1篇,计算机专业英语,本课程知识结构,第2篇,第3篇,第4篇,第1篇 基础篇,Chapter 1Architecture of Computer Systems,Text Any discussion of computer architectures，of how computers and computer systems are organized，designed，and implemented，will inevitably make reference to the“von Neumann architecture”as a basis for comparison，because virtually every electronic computer ever built has been rooted in this architecture.1,第1篇 基础篇,We have strong intuitive feelings about the“von Neumann architecture”，because this is what we have always used.This is“the way computers work”.To comprehend how computer designers conceive，or to appreciate what new choices must be found，it is necessary to have a definitive understanding of what the von Neumann architecture is and is not and what its implications are.The von Neumann architecture based on three ideas：four subsystems，stored program concept and sequential execution of instructions.2,第1篇 基础篇,Four Subsystems According to Von Neumanns preliminary discussion，the generalpurpose computing machine contains four main“organs”.These are identified as relating to arithmetic，memory，control，and connection with the human operator.In other words，they are the arithmetic logic unit，the control unit，the memory，and the inputoutput devices that we see in the classical model of what a computer“looks like”.The control unit（CU），arithmetic logic unit（ALU）and register constitute the central processing unit（CPU）,第1篇 基础篇,Four Subsystems According to Von Neumanns preliminary discussion，the generalpurpose computing machine contains four main“organs”.These are identified as relating to arithmetic，memory，control，and connection with the human operator.In other words，they are the arithmetic logic unit，the control unit，the memory，and the inputoutput devices that we see in the classical model of what a computer“looks like”.The control unit（CU），arithmetic logic unit（ALU）and register constitute the central processing unit（CPU）,第1篇 基础篇,Stored Program Concept To Von Neumann，the key to building a generalpurpose device lies in its ability to store not only its data and the intermediate results of computation，but also to store the instructions，or orders，which bring about the computation.3In a generalpurpose one,the instructions must be as changeable as the numbers they acted upon.Therefore，why not encode the instructions into numeric form and store instructions and data in the same memory?Von Neumann proposes that programs and data should be stored in the same binarynumber format in the memory device.4,第1篇 基础篇,Usually，this is viewed as the principal contribution provided by Von Neumanns insight into the nature of what a computer should be，which brings the significant breakthrough in the development of the generalpurpose electronic computer used today.That is what we all knowthe concept of a stored program.,第1篇 基础篇,Sequential Execution of Instructions Based on the stored program concept，computers store programs and data in a slowtoaccess storage medium（such as a hard disk）and work on them in a fastaccess，volatile storage medium（RAM）.5However，this concept has a perceived bottleneck：it is designed to process instructions one after another instead of using faster parallel processing.6When the program executes，the message seems to appear all at once，but the speed of the computer has deceived you.In fact，one instruction executes in sequence，that is at a time：fetching one instruction from memory，interpreting（decoding）it and executing it.The computer does not go on to the next instruction until the one it is working on is completed.,according to 依照architecture 体系结构breakthrough 突破constitute 组成decode 译码，解码encode 编码fetch 获取implication 含义instruction 指令intuitive 直觉in sequence 顺次，依次parallel processing 并行处理preliminary 初步的，最初的stored program concept 存储程序概念sequential 顺序的subsystem 子系统,第1篇 基础篇,Key Words&Terms,第1篇 基础篇,Text In computer science，the way information is organized in the memory of a computer is called a data structure.1 Its a data type whose values are composed of component elements that are related by some structure.Much of programming involves the storage and retrieval of data.Many of the most efficient algorithms for important problems are based on the use of specific data structures；the efficiency of the algorithm depends on the efficiency of the underlying data structure.2Software design often involves the choice of appropriate data structures.,Chapter 2Data Structure,第1篇 基础篇,For example，imagine that you are asked to create a database of names with ABC companys management and employees.To start your work，you make a list of everyone in the company along with their position,as shown in Table 2-1.,第1篇 基础篇,Although this list contains both name and position，it does not tell you which managers are responsible for which workers and so on.If you want your database to represent the relationships between management and employees at ABC，a tree diagram depicted Figure 2-1 is a much better structure for showing the work relationship at ABC.,第1篇 基础篇,These two diagrams are examples of different data structures.If you want to locate the employees record very quickly，you can use the list that keeps the names of the employees in alphabetical order；If you want to see relationships between employees，the tree structure is much better.There are many different data structures that programmers use to organize data in computers.Each data structure has certain operations that naturally fit with data structure.Often these operations are bundled with the data structure and together they are called a data type.An example of several common data structures are array，linked list，stack，queue，binary tree，and hash table.,第1篇 基础篇,List A collection of items accessible one after another beginning at the head and ending at the tail.,Stack A collection of items in which only the most recently added item may be removed.The latest added item is at the top.Basic operations are push and pop.Also known as“last in，first out”or LIFO.,Queue A collection of items in which only the earliest added item may be accessed.Basic operations are add（to the tail）or enqueue and delete（from the head）or dequeue.Delete returns the item removed.Also known as“first in，first out”or FIFO.,第1篇 基础篇,List A collection of items accessible one after another beginning at the head and ending at the tail.,Stack A collection of items in which only the most recently added item may be removed.The latest added item is at the top.Basic operations are push and pop.Also known as“last in，first out”or LIFO.,Queue A collection of items in which only the earliest added item may be accessed.Basic operations are add（to the tail）or enqueue and delete（from the head）or dequeue.Delete returns the item removed.Also known as“first in，first out”or FIFO.,第1篇 基础篇,Tree A data structure accessed beginning at the root node.Each node is either a leaf or an internal node.An internal node has one or more child nodes and is called the parent of its child nodes.3All children of the same node are siblings.Contrary to a physical tree，the root is usually depicted at the top of the structure，and the leaves are depicted at the bottom.,algorithm 算法alphabetical 按字母顺序的appropriate 适当的array 数组depict 描述dequeue 出队diagram 图表enqueue 入队hash table 哈希表queue 队列retrieval 检索sibling 兄弟姐妹，同胞stack 堆栈,第1篇 基础篇,Key Words&Terms,FIFO（First In First Out）先进先出FIFO（Last In First Out）后进先出,第1篇 基础篇,Abbreviations,第1篇 基础篇,Chapter 3File Format,Text In general terms，a file format in the PC world signifies what type of information is contained in a particular file.These are usually designated by the one to four（usually three）characters（the extensions）after the period in a filename.1,TXT A file ending in“.TXT”usually designates that the file is a plaintext file.This can contain virtually any type of text a recipe，documentation for software，a book report draft，or whatever.When a file ending in“.TXT”is doubleclicked，a text editor，such as notepad，should appear，allowing you to view and/or edit the contents of the file.,第1篇 基础篇,PDF If a file has the extension.pdf，then it most likely is in the Portable Document Format（PDF），developed by Adobe Systems，Inc.PDF maintains the original document formatting for both printing and viewing on a multiple computing platforms，including Windows，UNIX and Mac.Although they contain the complete formatting of the original document，including fonts and images，PDF files are highly compressed，allowing complex information to be downloaded efficiently.2 To view PDF files，you must download the Adobe Acrobat Reader，which is free software for viewing and printing Adobe Portable Document Format（PDF）files on major hardware and operating system platforms.,第1篇 基础篇,For storing digital images，there is a large number of formats too.Most formats were developed for particular programs，some have become the standards，and a few formats were developed specifically for interchanging files between different programs and computers.3 Following are some of the formats most commonly used.,第1篇 基础篇,BMP BMP is the native bitmap file format of the Microsoft Windows environment.It efficiently stores mapped or unmapped RGB graphics data with pixels 1bits，4bits，8bits，or 24bits in size.BMP is an excellent choice for a simple bitmap format which supports a wide range of RGB image data.Bitmap images can be produced from existing drawings or photographs by“scanners”and edited with“image editing”programs such as Adobe Photoshop.4,GIF A mapped bitmap format developed for file interchange，commonly used for icons and other graphics on the Web.The GIF（Graphic Interchange Format）is limited to 256 colors.A single GIF file can combine several frames together for basic animated motion.A good compression method is built into the format.,第1篇 基础篇,JPEG Named after the Joint Photographic Experts Group，JPEG is a lossy codec for storing and transferring fullcolor digital images thats often used to post photography and artwork on the Web.5JPEG compression takes advantage of the human eyes inability to see minute color changes，removing portions of data from the original picture file.When creating a JPEG file，varying amounts of compression can be selected，depending on the desired file size and image quality.,TIFF TIFF（Tag Image File Format）is a flexible container format for digital still images.It can incorporate various forms of compression（like JPEG），or can be uncompressed.Some digital cameras offer a special TIFF mode for capturing uncompressed photos；however，these files require many times more storage space than JPEGs，and can quickly fill up your cameras available memory.,bitmap 位图文件camera 照相机，摄像机codec 多媒体数字信号编解码器compress 压缩designate 指明，指定draft 草图，草稿extension 扩展名incorporate 合并interchange 交换lossy 有损耗的motion 运动，移动notepad 记事本pixel 像素platform 平台,第1篇 基础篇,Key Words&Terms,GIF（Graphic Interchange Format）可交换的图像文件，可交换的图像文件格式JPEG（Joint Photographic Experts Group）联合图像专家组，一种压缩标准PDF（Portable Document Format）便携式文件格式TIFF（Tag Image File Format）标签图像文件格式,第1篇 基础篇,Abbreviations,第1篇 基础篇,Text A database management system（DBMS），sometimes just called a database manager，is a program that lets one or more computer users create，access，update and manage the data.1 Technically speaking，it is a software system that uses a standard method of cataloging，retrieving，and running queries on data.,Chapter 4Database Management System,Databases are usually designed to manage large bodies of information.This involves definition of structures for information storage（data modeling），provision of mechanisms for the manipulation of information（file and systems structure，query processing），concurrency control if the system is shared by users，and providing for the safety of information in the database（crash recovery and security）.,第1篇 基础篇,The DBMS manages user requests（and requests from other programs）so that users and other programs are free from having to understand where the data is physically located on storage media and，in a multiuser system，who else may also be accessing the data.2In handling user requests，the DBMS ensures the integrity of the data（that is，making sure it continues to be accessible and is consistently organized as intended）and security（making sure only those with access privileges can access the data）.,第1篇 基础篇,The goal of a DBMS is to provide an environment that is both convenient and efficient to use in retrieving information from the database and storing information into the database.3The most typical DBMS is a Relational Database Management System（RDBMS）.The standard user and program interface for RDBMS is the Structured Query Language（SQL）.A newer kind of DBMS is the objectoriented database management system（ODBMS）.,A DBMS can be thought of as a file manager that manages data in databases rather than files in file systems.In IBMs mainframe operating systems，the nonrelational data managers were（and are，because these legacy application systems are still used）known as access methods.,第1篇 基础篇,A DBMS is usually an inherent part of a database product.On PCs，Microsoft Access is a popular example of a single or small group user DBMS.Microsofts SQL Server is an example of a DBMS that serves database requests from multiple（client）users.Other popular DBMSs are IBMs DB2，Oracles line of database management products，and Sybases products.,catalog 编目，分类consistently 始终如一地crash 冲突database 数据库definition 定义，解说inherent 与生俱来的，固有的integrity 完整性involving 包括，使陷于manipulation 处理操作persistent 持久稳固的privilege 特权Provision 供应，预备，防备retrieve 检索storage 存储technically 技术上,第1篇 基础篇,Key Words&Terms,DBMS（database management system）数据库管理系统RDBMS（Relational Data(base)Management System）关系数据（库）管理系统SQL（Structured Query Language）结构化查询语言,第1篇 基础篇,Abbreviations,第1篇 基础篇,Chapter 5IP Address,Text Every computer that communicates over the Internet is assigned an IP address that uniquely identifies the device and distinguishes it from other computers on the Internet.1To make it easier for us to remember，a typical IP address is normally expressed in decimal format as a“dotted decimal number”like 192.168.10.126.But computers communicate in binary form.Look at the same IP address in binary：11000000.10101000.00001010.01111110 The four numbers in an IP address are called octets，because they each have eight positions when viewed in binary form.,第1篇 基础篇,Every IP address consists of 32 bits，often shown as 4 octets of numbers from 0 to 255 represented in decimal form instead of binary form.2It consists of two parts，the first part of an Internet address identifies the network on which the host resides，while the second part identifies the particular host on the given network.This creates the twolevel addressing hierarchy that is illustrated in Figure 5-1.,第1篇 基础篇,In recent years，the network number field has been referred to as the network prefix because the leading portion of each IP address identifies the network number.All hosts on a given network share the same network prefix but must have a unique host number.3Similarly，any two hosts on different networks must have different network prefixes but may have t