外文翻译---软件和软件工程(编辑修改稿)

外文翻译---软件和软件工程(编辑修改稿)内容摘要：

e and earn a bundle of money. As the number of puterbased systems grew, libraries of puter software began to expand. Inhouse development projects produced tens of thousands of program source statements. Software products purchased from the outside added hundreds of thousands of new statements. A dark cloud appeared on the horizon. All of these programsall of these source statementshad to be corrected when faults were detected, modified as user requirements changed, or adapted to new hardware that was purchased. These activities were collectively called software maintenance. Effort spent on software maintenance began to absorb resources at an alarming rate. Worse yet, the personalized nature of many programs made them virtually unmentionable. A software crisis loomed on the horizon. The third era of puter system evolution began in the mid1970s and continues today. The distributed systemmultiple puters, each performing functions concurrently and municating with one another greatly increased the plexity of puterbased systems. Global and local area works, highbandwidth digital munications, and increasing demands for 39。 instantaneous39。 data access put heavy demands on software developers. The third era has also been characterized by the advent and widespread use of microprocessors, personal puters, and powerful desktop workstations. The microprocessor has spawned a wide array of intelligent productsfrom automobiles to microwave ovens, from industrial robots to blood serum diagnostic equipment. In many cases, software technology is being integrated into products by technical staff who understand hardware but are often novices in software development. The personal puter has been the catalyst for the growth of many software panies. While the software panies of the second era sold hundreds or thousands of copies of their programs, the software panies of the third era sell tens and even hundreds of thousands of copies. Personal puter hardware is rapidly being a modity, while software provides the differentiating characteristic. In fact, as the rate of personal puter sales growth flattened during the mid1980s, softwareproduct sales continued to grow. Many people in industry and at home spent more money on software than they did to purchase the puter on which the software would run. 5 The fourth era in puter software is just beginning. Objectoriented technologies (Chapters 8 and 12) are rapidly displacing more conventional software development approaches in many application areas. Authors such as Feigenbaum and McCorduck [FEI83] and Allman [ALL89] predict that fifthgeneration puters, radically different puting architectures, and their related software will have a profound impact on the balance of political and industrial power throughout the world. Already, fourthgeneration techniques for software development (discussed later in this chapter) are changing the manner in which some segments of the software munity build puter programs. Expert systems and artificial intelligence software has finally moved from the laboratory into practical application for wideranging problems in the real world. Artificial neural work software has opened exciting possibilities for pattern recognition and huma。