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1、软件生命周期计算机程序科技文献翻译 Section A Computer Program (计算机程序)Section B Software Life Cycle (软件生命周期)英文原文：Computer Program. IntroductionA computer program is a set of instructions that directs a computer to perform some processing function or combination functions. For the instructions to be carried out, a com
2、puter must execute a program, that is, that is the computer reads the program, and then follows the steps encoded in the program in a precise order until completion. A program can be executed many different times, with each execution yielding a potentially different result depending upon the options
3、 and data that the user gives the computer.Program fall into two major classes: application program and operating systems. An application program is one that carries out some function directly for a user, such as word processing or game playing. An operating system is a program that manages the comp
4、uter and the various 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. Examples of operating systems are DOS, Windows XP, OS/2, and UNIX. .Program Development Software designers
5、create new program by using special applications programs, often called utility programs or development programs. A programmer uses another type of program called a text editor to write the new program in a special notation called programming language. With the text editor, the programmer creates a
6、text file, which is an ordered list of instructions, also called program 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
7、operating systems will recognize as a proper program and be able 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 programming languages, but they serve the same p
8、urpose of translating from a programming language into machine language.A compiler translates text files written in a high-level programming language- such as FORTRAN, C, or Pascal from the source code to the object code all at once, This differs from the approach taken by interpreted language such
9、as BASIC, in which a program in translated into object code statement by statement as each instruction is executed. The advantage to interpreted language is that they can begin executing the program immediately instead of having to waiting for all the source code to be compiled. Changes can also be
10、made to the program fairly quickly without having waiting for it to be compiled again. The disadvantage of interpreted language is that 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 com
11、piled only once and thus can 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 scientific applications.Another type of translator is the assembler, which is used for programs or par
12、ts of programs written in assembly language. Assembly language is another programming language, but it is much more similar to machine language than other type of high-level language. In assembly language, a single statement can usually be translated into a single instruction of machine language. To
13、day, assembly language is rarely used to written entire program, but is instead most often used when the programmer needs to directly control some aspect of the computers function.Programs are often written as a set of smaller pieces, with each piece representing some aspect of the overall applicati
14、on program. After each piece has been compiled separately, a program 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 used to help problems called bugs. Debugger programs usually de
15、tect an event in the executing program 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 and execute programs. A compiler takes a Java source program and translates it into an intermediate
16、form. Such intermediate programs are then transferred over the Internet into computers where an interpreter program then executes the intermediate from as an application program. Program ElementsMost programs are built from just a few kings of steps that are repeated many times in different contexts and in different combinations throughout the program. The most common step performs some computation, and then proceeds to the next step
