科技文献翻译Section A Computer Program(计算机程序)Section B Software Life Cycle(软件生命周期)学生姓名：彭金辉学号：20032430217专业：计算机科学与技术信息工程学院完成时间：2007-5-202007年6月1日英文原文：Computer ProgramAmateur LeagueNewAdd/wareProind FCatalog出I.IntroductionA computer program is a set of instructions that directs a computer to perform someprocessing function or combination functions.For the instructions to be carried out,a computermust execute a program,that is,that is the computer reads the program,and then follows the stepsencoded in the program in a precise order until completion.A program can be executed manydifferent times,with each execution yielding a potentially different result depending upon theoptions and data that the user gives the computer.Program fall into two major classes:application program and operating systems.Anapplication program is one that carries out some function directly for a user,such as wordprocessing or game playing.An operating system is a program that manages the computer and thevarious resources and devices connected to it,such as RAM(random access memory),hard drives,monitors,keyboards,printers,and modems,so that they may be used by other program.Examplesof operating systems are DOS,Windows XP,OS/2,and UNIX.II.Program DevelopmentSoftware designers create new program by using special applications programs,often calledutility programs or development programs.A programmer uses another type of program called atext editor to write the new program in a special notation called programming language.With thetext editor,the programmer creates a text file,which is an ordered list of instructions,also calledprogram source file.The individual instructions that make up the source file are called source code.At this point,a special application program translates the source code into machine code language,or object code-a format that the operating systems will recognize as a proper program and beable to execute.Three types of application programs translate from source code to object code:compilers,interpreters,and assemblers.The three operate differently and on different types of programminglanguages,but they serve the same purpose of translating from a programming language intomachine language.A compiler translates text files written in a high-level programming language-such asFORTRAN,C,or Pascal-from the source code to the object code all at once,This differs fromthe approach taken by interpreted language such as BASIC,in which a program in translated intoobject code statement by statement as each instruction is executed.The advantage to interpretedlanguage is that they can begin executing the program immediately instead of having to waitingfor all the source code to be compiled.Changes can also be made to the program fairly quicklywithout having waiting for it to be compiled again.The disadvantage of interpreted language isthat they are slow to execute,since the entire program must translated one instruction at a time,each time program is run.On the other hand,compiled language are compiled only once and thuscan be executed by the computer much more quickly than interpreted languages,For this reason,compiled languages are more common and almost always used in professional and scientificAnother type of translator is the assembler,which is used for programs or parts of programswritten in assembly language.Assembly language is another programming language,but it ismuch more similar to machine language than other type of high-level language.In assemblylanguage,a single statement can usually be translated into a single instruction of machinelanguage.Today,assembly language is rarely used to written entire program,but is instead mostoften used when the programmer needs to directly control some aspect of the computer's function.Programs are often written as a set of smaller pieces,with each piece representing someaspect of the overall application program.After each piece has been compiled separately,aprogram called linker combines all the translated pieces into a single executable program.Program seldom work correctly the first time,so a program called a debugger is often usedto help problems called bugs.Debugger programs usually detect an event in the executingprogram and point the programmer back to the origin of the event in the program code.Recent programming systems,such as Java,use a combination of approaches to create andexecute programs.A compiler takes a Java source program and translates it into an intermediateform.Such intermediate programs are then transferred over the Internet into computers where aninterpreter program then executes the intermediate from as an application program.IⅢ.Program ElementsMost programs are built from just a few kings of steps that are repeated many times indifferent contexts and in different combinations throughout the program.The most common stepperforms some computation,and then proceeds to the next step in the program,in the order