计算机专业英语课件3.

1、2021-7-13计算机专业英语1 2021-7-13计算机专业英语2 第第3章章 Software Knowledge 3.1 Data Structures 3.2 Operating System 3.3 Programming Languages 3.4 Software Engineering 3.5 Software Testing and Maintenance 2021-7-13计算机专业英语3 3.1 Data Structures General data structure types include the array, the file, the record, th

2、e table, the tree, and so on. In computer programming, a data structure may be selected or designed to store data for the purpose of working on it with various algorithms. If we provide a set of possible data values and a set of operations that act on the values, we can think of the combination as a

3、 data type. We will call any data type whose values are composed of component elements that are related by some structure a structured data type, or data structure. 2021-7-13计算机专业英语4 Integer Integer is amounts to a particular collection of axioms or rules that must be obeyed. The way in which intege

4、rs are represented is unimportant provided only that all readers understand the notationbinary, octal, decimal, hexadecimal, twos complement, ones complement or sign and magnitude, the choice does not matter. 2021-7-13计算机专业英语5 List The list is a flexible abstract data type. It is particularly useful

5、 when the number of elements to be stored is not known before running a program or can change during running. It is well suited to sequential processing of elements because the next element of a list is readily accessible from the current element. It is less suitable for random access to elements as

6、 this require a slow linear search. 2021-7-13计算机专业英语6 Array and Record The data types arrays and records are native to many programming languages. By using the pointer data type and dynamic memory allocation, many programming languages also provide the facilities for constructing linked structures.

7、Arrays, records, and linked structures provide the building blocks for implementing what we might call higher-level abstractions. 2021-7-13计算机专业英语7 Stack A stack is a data type whose major attributes are determined by the rules governing the insertion and deletion of its elements. The only element t

8、hat can be deleted or removed is the one that was inserted most recently. Such a structure is said to have a last-in/first-out (LIFO) behavior, or protocol. The sequencing of calls to and returns from subroutines follows a stack protocol. 2021-7-13计算机专业英语8 Queue The main feature of queues is that th

9、ey follow a first- come/first-served rule. In queues the earliest element inserted is the first served. In social settings, the rule appeals to our sense of equality and fairness. In computer systems, events that demand the attention of the computer are often handled according to a most- important-e

10、vent/first-served, or highest-priority in/first-out (HPIFO), rule. Such queues are called priority queue, in this type of queue service is not in order of time of arrival but rather in order of some measure of priority. 2021-7-13计算机专业英语9 The data structure of object-oriented software From the point

11、of view of deciding which data structure should represent that attributes of objects in a specific class, the emphasis that the object oriented approach places on abstraction is very important to the software development process. Abstraction means hiding unnecessary details. Once an appropriate abst

12、raction is selected, there may be several choices for representing the data structure. After an abstraction and representation are chosen, there are competing methods to encapsulate data structures. 2021-7-13计算机专业英语10 Key Words abstract 抽象，摘要抽象，摘要 accessible 易进入的，可使用的易进入的，可使用的 arithmetic 算术，算法算术，算法

13、axiom 公理，原理公理，原理 behavior 行为，举止行为，举止 contemporary 同时代的同时代的 devoid 全无的，缺乏的全无的，缺乏的 encapsulate 封装，压缩封装，压缩 identifiable 可以确认的可以确认的 instantiate 例示例示 2021-7-13计算机专业英语11 Key Words integrity 完整，正直完整，正直 irrelevant 无关系的，不相干的无关系的，不相干的 magnitude 重大，重要重大，重要 notation 记号，符号记号，符号 object-oriented 面向对象的面向对象的 sequent

14、ial 后继的后继的 stack 栈，堆栈栈，堆栈 tradeoff 交换，平衡，交易交换，平衡，交易 underlying 在下面的在下面的 versus 对对 2021-7-13计算机专业英语12 Notes 1The essence of a data type is that it attempts to identify qualities common to a group of individuals or objects that distinguish it as an identifiable class or kind. 本句由两个复合句构成，均由本句由两个复合句构成，均

15、由that引导。第一个引导。第一个that引导表语从句；引导表语从句； 第二个第二个that引导限定性定语从句，修饰引导限定性定语从句，修饰qualities，it代表代表a group of individuals or objects。 译文：数据类型的本质是标识一组个体或目标所共有的特性，这些译文：数据类型的本质是标识一组个体或目标所共有的特性，这些 特性把该组个体作为可识别的种类。特性把该组个体作为可识别的种类。 2021-7-13计算机专业英语13 Notes 2A data structure is a data type whose values are composed of

16、component elements that are related by some structure. 由由whose引导的限定性定语从句修饰引导的限定性定语从句修饰a data type，that引导的限定性引导的限定性 定语从句修饰定语从句修饰component elements。 译文：数据结构是一种数据类型，其值是由与某些结构有关的组成译文：数据结构是一种数据类型，其值是由与某些结构有关的组成 元素所构成的。元素所构成的。 3Many computer systems have stacks built into their circuitry and have machine-

17、level instructions to operate the hardware stack. 本句中，过去分词短语本句中，过去分词短语built into their circuitry作定语，修饰作定语，修饰stacks； 动词不定式短语动词不定式短语to operate the hardware stack也作定语，修饰也作定语，修饰 machine-level instructions。 译文：许多计算机系统的电路中都含有多个栈，并且含有操作硬件译文：许多计算机系统的电路中都含有多个栈，并且含有操作硬件 栈的机器指令。栈的机器指令。 2021-7-13计算机专业英语14 Notes

18、 4Procedural abstraction, or algorithmic abstraction, is hiding of algorithmic details, which allows the algorithm to be seen or described, at various levels of detail. 本句中的本句中的“or algorithmic abstraction”是同位语，是同位语，“which allows the algorithm to be seen or described”也是同位语。也是同位语。 译文：过程抽象或算法抽象是隐藏算法细节的

19、，允许算法在各个细译文：过程抽象或算法抽象是隐藏算法细节的，允许算法在各个细 节层次上可见或被描述。节层次上可见或被描述。 5 Once an appropriate abstraction is selected, there may be several choices for representing the data structure. 本句由本句由“Once”引导时间状语从句。引导时间状语从句。 译文：一旦选择了一个合适的抽象，就有一些选择来表示数据结构。译文：一旦选择了一个合适的抽象，就有一些选择来表示数据结构。 2021-7-13计算机专业英语15 词组翻译练习词组翻译练习 (

20、1) 自由访问自由访问 random access (2) 数据类型数据类型 data type (3) 数据结构数据结构 data structure (4) 数据值数据值 data value (5) 二进制和十六进制二进制和十六进制 binary and hexadecimal (6) 抽象数据类型抽象数据类型 abstract data type (7) 后进先出后进先出 last-in / first-out (8) 算术表达式算术表达式 arithmetic expression 2021-7-13计算机专业英语16 Reading Material： Applications o

21、f stack and queue When a call is made to a new function, all the variables local to the calling routine need to be saved by the system, since otherwise the new function will overwrite the calling routines variables. It is frequently the case that stacks do not share components and then it is usual t

22、o write pop and push procedures. There are many applications of the first-in/first-out (FIFO) protocol of queues in computing. There are several algorithms that use queues to give efficient running times. 2021-7-13计算机专业英语17 Database Technology A database-management system (DBMS) consists of a collec

23、tion of interrelated data and a set of programs to access those data. The collection of data, usually referred to as the data-base, contains information about one particular enterprise. The primary goal of a DBMS is to provide an environment that is both convenient and efficient to use in retrieving

24、 and storing database information. 2021-7-13计算机专业英语18 Database systems are designed to manage large bodies of information. The management of data involves both the definition of structures for the storage of information and the provision of mechanisms for the manipulation of information. 2021-7-13计算

25、机专业英语19 In addition, the database system must provide for the safety of the information stored, despite system crashes or attempts at unauthorized access. If data are to be shared among several users, the system must avoid possible anomalous results. 2021-7-13计算机专业英语20 The importance of information

26、in most organizations-which determines the value of the database-has led to the development of a large body of concepts and techniques for the efficient management of data. 2021-7-13计算机专业英语21 The storage structure and access methods used by the database system are specified by a set of definitions i

27、n a special of DDL called a data storage and definition language. The result of compilation of these definitions is a set of instructions to specify the implementation details of the database schemas-details are usually hidden from the users. A database schema is also specified by DDL. 2021-7-13计算机专

28、业英语22 The result of compilation of DDL statements is a set of tables that is stored in a special file called data dictionary, or data directory. A data dictionary is a file that contains metadata-that is, data about data. This file is consulted before actual data are read or modified in the database

29、 system. 2021-7-13计算机专业英语23 Transaction Management A transaction is a collection of operations that performs a single logical function in a database application. Each transaction is a unit of both atomicity and consistency. Thus, we require that transactions do not violate any database- consistency

30、constraints. 2021-7-13计算机专业英语24 That is, if the database was consistent when a transaction started, the database must be consistent when the transaction successfully terminates. However, during the execution of a transaction, it may be necessary temporarily to allow inconsistency. This temporary inc

31、onsistency, although necessary, may lead to difficulty if a failure occurs. 2021-7-13计算机专业英语25 It is the responsibility of the programmer to define properly the various transactions, such that each preserves the consistency of the database. For example, the transactions to transfer funds from accoun

32、t A to account B could be defined to be composed of two separate programs: one that debits account A, and an another that credits account B. 2021-7-13计算机专业英语26 The execution of these two programs one after the other will indeed preserve consistency. However, each program by itself does not transform

33、 the database from a consistent state to a new consistent state. Thus, those programs are not transactions. 2021-7-13计算机专业英语27 Ensuring the atomicity and durability properties is the responsibility of the database system itself-specifically, of the transaction-management component. In the absence of

34、 failures, all transactions complete successfully, and atomicity is achieved easily. 2021-7-13计算机专业英语28 3.2 Operating System The purpose of an operating system is to provide an environment in which a user may execute programs. Operating systems exist because they are a reasonable way to solve the pr

35、oblem of creating a usable computing system. The primary goal of an operating system is convenience for the user. A secondary goal is efficient operation of the computer system. 2021-7-13计算机专业英语29 Resource Management The operating system provides the means for the proper use of these resources in th

36、e operation of the computer system. We can view an operating system as a resource allocates. The operating system sets up the order in which programs are processed, and defines the sequence in which particular jobs are executed. 2021-7-13计算机专业英语30 I/O Management To facilitate execution of I/O operat

37、ions, most operating systems have a standard set of control instructions to handle the processing of all input and output instructions. These standard instructions, referred to as the input/output control system (IOCS), are an integral part of most operating systems. The controlling software calls o

38、n the IOCS software to actually complete the I/O operation. 2021-7-13计算机专业英语31 Classification of Operating Systems A single-user operating system expects to deal with one set of input devicesthose that can be controlled by one user at a time. A multi-user operating system is designed to deal with in

39、put, output, and processing requests from many users-all at the same time. A network operating system provides communications and routing services that allow computers to share data, programs and peripheral devices. 2021-7-13计算机专业英语32 Classification of Operating Systems A multitasking operating syst

40、em provides process and memory management services that allow two or more programs to run simultaneously. All modern operating systems are multitasking and can run several processes simultaneously. A desktop operating system is one that is designed for a personal computereither a desktop or notebook

41、 computer. 2021-7-13计算机专业英语33 Key Words accommodate 使适应使适应 assess 评估评估 context switching 上下文转接，任务切换上下文转接，任务切换 convenience 方便，便利方便，便利 efficient 有效的有效的 environment 环境环境 fundamental 基本的，原则基本的，原则 government 政府政府 2021-7-13计算机专业英语34 Key Words handle 操作，处理操作，处理 interface 接口，界面接口，界面 primary 主要的，根本的主要的，根本的 p

42、rimitive 原始的，基本的原始的，基本的 scheduler 调度程序，调度表调度程序，调度表 statement 陈述，指令，语句陈述，指令，语句 suspend 暂停，挂起暂停，挂起 workstation 工作站工作站 2021-7-13计算机专业英语35 Notes 1An operating system is a program, which acts as an interface between a user of a computer and the computer hardware. 本句由本句由“which”引导非限定性定语从句，修饰引导非限定性定语从句，修饰“p

43、rogram”。 译文：操作系统是一种程序，它是用户与计算机硬件之间的接口。译文：操作系统是一种程序，它是用户与计算机硬件之间的接口。 2 The fundamental goal of computer systems is to execute user programs and solve user problems. 本句由不定式结构本句由不定式结构“to execute ”作表语。作表语。 译文：计算机系统的基本目标是执行用户程序和解决用户问题。译文：计算机系统的基本目标是执行用户程序和解决用户问题。 2021-7-13计算机专业英语36 Notes 3 Operating syst

44、em exists because they are supposed to make it easier to compute with an operating system than without an operating system. 本句由本句由“because”引导原因状语从句，用引导原因状语从句，用“than”实现比较。实现比较。 译文：操作系统的存在是因为有操作系统比没有操作系统计算更容译文：操作系统的存在是因为有操作系统比没有操作系统计算更容 易。易。 4 A single-user operating system expects to deal with one se

45、t of input devicesthose that can be controlled by one user at a time. 本句的本句的“those that can be controlled by one user at a time”是同位语。是同位语。 译文：单用户操作系统是用来处理一组输入设备，那些能被一个用译文：单用户操作系统是用来处理一组输入设备，那些能被一个用 户在同一时刻控制的设备。户在同一时刻控制的设备。 2021-7-13计算机专业英语37 Notes 5The most common mechanism used to create this illus

46、ion is time slice multitasking, whereby each process is run individually for a fixed period of time. 过去分词短语过去分词短语used to create this illusion作定语，修饰作定语，修饰mechanism； 由由whereby引导的是非限制性定语从句。引导的是非限制性定语从句。whereby：by means of which，以，以方式；凭借。方式；凭借。 译文：译文：产生这种错觉的最常用机制是时间分割多任务处理，以每个产生这种错觉的最常用机制是时间分割多任务处理，以每个

47、过程各自运行固定的一段时间的方式来实现的。过程各自运行固定的一段时间的方式来实现的。 2021-7-13计算机专业英语38 词组翻译练习词组翻译练习 (1) 资源资源 resource (2) 多用户系统多用户系统 multi-user system (3) 单任务单任务 single-task (4) 桌面操作系统桌面操作系统 desktop operating system (5) 个人计算机个人计算机 personal computer (6) 多任务操作系统多任务操作系统 multitasking operating system (7) 笔记本电脑笔记本电脑 notebook com

48、puter (8) 作业队列作业队列 job queue 2021-7-13计算机专业英语39 Reading Material： Windows XP Technical Overview The Windows operating system gets its name from the rectangular work areas that appear on the screen-based desktop. Each area can display a different document or program, providing a visual model of the o

49、perating systems multitasking capabilities. Windows XP is the next version of Microsoft Windows beyond Windows 2000 and Windows Millennium. Windows XP is built on an enhanced Windows 2000 code base, with different versions aimed at home users and business users: Windows XP Home Edition and Windows X

50、P Professional. 2021-7-13计算机专业英语40 The characteristics of Windows XP Fast User Switching for Multiple Users of a Computer New Visual Style User Interface Enhances Productivity Windows Media Player 8 64-Bit Support 2021-7-13计算机专业英语41 3.3 Programming Languages A programming language or computer langua

51、ge is a standardized communication technique for expressing instructions to a computer. A language enables a programmer to precisely specify what data a computer will act upon, how these data will be stored/transmitted, and what actions to take under various circumstances of cases. Programming langu

52、ages are important tools for helping software engineers write better programs faster. 2021-7-13计算机专业英语42 Procedural programming and Object-oriented programming Procedural programming involves using your knowledge of a programming language to create computer memory locations that can hold values and

53、writing a series of steps or operations that manipulate those values. A single procedural program often contains hundreds of variable and thousands of procedure calls. Object-oriented programming is an extension of procedural programming in which you take a slightly different approach to writing com

54、puter programs. Writing object-oriented programs involves both creating objects and creating applications that use those objects. 2021-7-13计算机专业英语43 Machine Language An executable program is a sequence of extremely simple instructions known as machine code. Machine code instructions are binarythat i

55、s, sequences of bits (0s and 1s). Because these numbers are not understood easily by humans, computer instructions usually are not written in machine code. 2021-7-13计算机专业英语44 Assembly Language Assembly language uses commands that are easier for programmers to understand than are machine-language com

56、mands. Each machine language instruction has an equivalent command in assembly language. Assembly language is sometimes inserted into a high-level language program to carry out specific hardware tasks or to speed up a high- level program. 2021-7-13计算机专业英语45 High-Level Languages If the computer could

57、 translate convenient symbols into basic operations, why couldnt it also perform other clerical coding functions? A high-level programming language is a means of writing down, in formal terms, the steps that must be performed to process a given set of data in a uniquely defined way. The high-level l

58、anguages are often oriented toward a particular class of processing problems. 2021-7-13计算机专业英语46 Compiler and Interpreter A complier is a program that translates source code into object code. Every high-level programming language comes with a compiler. Because compilers translate source code into ob

59、ject code, which is unique for each type of computer, many compilers are available for the same language. An interpreter translates high-level instructions into an intermediate form, which it then executes. The advantage of an interpreter, however, is that it does not need to go through the compilat

60、ion stage during which machine instructions are generated. 2021-7-13计算机专业英语47 Key Words assembler汇编程序，汇编器汇编程序，汇编器 circumstance 环境，状况环境，状况 clerical 文书上的文书上的 compilation 编辑编辑 correspondence相应相应 employee 职员，员工职员，员工 envision 想象想象 equivalent 相等的，相当的相等的，相当的 federal 联合的，同盟的联合的，同盟的 instruction指令指令 invoke 引起