【正文】 applications (Law). With the increase in plexity of the software, the full and plete separation would not exist. Below the software described the breadth of potential applications software. System software System software for other services the procedures set procedures. Some system software (for example, the piler, editor and file management utility) dealing with plex information structure but identified. Other applications (such as operating system ponents, drivers and remote munications processors) to deal with a large number of nondeterministic data. No matter under what circumstances, the system software is characterized by: frequent interaction with the puter hardware。 Transmission analysis of the information required。 Demand scheduling, resource sharing and management of the plex process of concurrent operation。 3. Difficult test。 Or adapted to cope with the purchase of new hardware. These are generally referred to as software maintenance. Software maintenance costs in the energy, its alarm rate to the frequency of troubleshooting source. But even worse is that many of the personal characteristics of procedures they have in fact made it is impossible to maintain. This appeared software crisis. The development of puter systems from the third era began in the mid1970s until now: Distribution System more puters, with various puter operation and mutual munication greatly increased the plexity of puter systems. Global works and local area works, broadband digital munications and the growing of the instant data access request, the software developers raised very high demands. Many personal puter software panies has been the driving force for development. Despite the second era of software panies sold only a few hundred, a few thousand sets, the third era of software panies have sold tens of thousands, even hundreds of thousands of sets. Personal puter hardware will soon bee a modity, and puter software will enable the characteristics are different. In fact, in the mid1980s, when the personal puter sales growth rate tends to slow, sales of software products still continue to grow. Many people spent on household and industrial use of the software purchase money than necessary puter software more money. The fourth puter software era has just begun. Feigenbaum and McCorduck [FEI83] These authors predicted: fifthgeneration puter and related software in the world will be on political power and the balance of industrial power have a farreaching impact. The fourth generation of software development technology (4 GT) is changing the software in the Community of certain sectors of the puter program design methods. Expert systems and artificial intelligence software has been the ultimate laboratory to the people from the reality of the problems in the practical application. With the era came to the fourth, the software crisis continues to deepen. Now we can describe software crisis following ways: 1. Hardware plex procedures have been beyond our hardware design to the development potential of software capabilities. 2. The design of the new procedures failed to keep pace with the ability of the new procedural requirements. 3. Maintenance has been the ability of poor design and lack of resources threats. As a software crisis response, software engineering practice is applied to the entire industrial fields. 20 years ago, can be wise to draw up puter software is a person less than 1%. Today, the majority of professionals and the public to a large extent, many people feel they have to understand software, is it true? One stresses the software may be described textbooks Software: (1) after the operation to provide the specified functionality and performance Directive (puter program)。s potential. Software that will enable us to develop and utilize the potential of this tool. The software development environment, has been working with puter systems development four times tightly coupled. Better hardware performance, small size and lowcost has prompted many plex puterbased systems tend to perfection. Vacuum tube processor has been developed to the microelectronics equipment. On the puter revolution bestselling book, Osborne [OSB79] will be called the new industrial revolution 39。實際上，在軟件領域， PC 軟件仍然代表某些最富創(chuàng)造力的軟件設計。嵌入式軟件駐留在只讀存儲器之中，用來為顧客和工業(yè)市場控制產(chǎn)品和系統(tǒng)。離散的 “系統(tǒng) ”（如工資單軟件、收／付款軟件和存貨清單軟件等）已發(fā)展到管理信息系統(tǒng)（ MIS)軟件，這種軟件能訪問一個或多個包含商業(yè)信息在內的大型數(shù)據(jù)庫。應該注意術語 “實時 ”與 “交互 ”或 “分時 ”不同。其他系統(tǒng)應用（如操作系統(tǒng)部件、驅動程序和遠程通訊處理器）大量地處理非確定性數(shù)據(jù)。隨著軟件復雜性的增加，完全徹底的分類就不存在了。這種應用程序就是確定性的。例如，許多商業(yè)應用程序使用高度結構化的輸人數(shù)據(jù)（數(shù)據(jù)庫）并生成格式化 “報表 ”。到目前為止，第四代語言 (4GLs )已用于數(shù)據(jù)庫應用程序和其他商業(yè)數(shù)據(jù)處理領域。因此，頭三代語言稱作過程語言。 機器可執(zhí)行指令是軟件最底層的形式。每遇到一條語句，該語句就被轉換成機器可執(zhí)行代碼并加以執(zhí)行。專用語言（為特殊應用領域設計的）如 Smalltalk,APL,LISP和 Prolog，作為新的應用方法從實驗室轉向實際使用，正得到廣泛的認可。實際上，高級語言的編譯程序和解釋程序生成機器語言作為輸出。 應用機器語言時，軟件 “生產(chǎn)效率 ”極其低下。 機器級語言是 CPU 指令集的符號表示。 所有的程序設計語言都是人工語言。 人類若能通過自然語言（如英語、西班牙語或俄語）與計算機交流是最理想不過了。 軟件成分 計算機軟件是以兩種基本形式存在的信息：一個是非機器可執(zhí)行成分，另一個是機器可執(zhí)行成分。 令人悲哀的是，軟件設計者承擔不起上述的豪華。試設想一下微處理產(chǎn)品的控制硬件的設計和制造方法。軟件卻沒有備件。修改軟件時，有可能引發(fā)一些新的缺陷，使故障率增大，在故障率曲線恢復到起初的穩(wěn)態(tài)故障率以前，又需作另一 次修改，致使曲線再次上升。但是在程序運作初期，未發(fā)現(xiàn)的缺陷會引發(fā)較高的故障率。缺欠排除后， 在某一段時間內，故障率降至一個較低的穩(wěn)定的水平。而且， “軟件工廠 ”這一概念建議為開發(fā)軟件而使用自動化工具。 軟件是邏輯的而不是物質的系統(tǒng)部件。 勿容置疑，可以給出更完整的定義，但我們需要的不僅只是一個正式的定義。 3．維護已有程序的能力受到低劣的設計和匱乏的資源的威脅。專家系統(tǒng)和人工智能軟件已經(jīng)最終從實驗室轉人了現(xiàn)實中各種問題的實際應用。許多人花在工業(yè)用的和家用軟件上的錢要比購買軟件運行所需的計算機的錢要多。 個人計算機一直都是許多軟 件公司的發(fā)展動力。然而更糟的是，許多程序的個人化特點使得它們事實上是無法維護的。從外部購買的軟件產(chǎn)品又增加了幾十，萬條新語句。實時系統(tǒng)能夠從多信息源收集、分析并傳送數(shù)據(jù)，從而用毫秒級而不是用分鐘級控制過程和生產(chǎn)輸出。其中的一些今天仍被人們使用，而且提供了一些為后人所不斷欽佩的驚人成就。由于那時工作變動少，經(jīng)理可以放心，即使軟件出了問題，此人也會在現(xiàn)場。而另一方面，軟件則是專為某項應用設計的，因此其應用面相對有限。軟件開發(fā)事實上是不受控制的，除非出現(xiàn)程序丟失或價格開始猛漲的情況。在關于 “計算機革命 ”的暢銷書中， Osborne[OSB79]將其稱為 “新的工業(yè)革命， ’； Toffler [TOF80 ]將微電子技術的到來稱為人類歷史上 “第三次變革浪潮 ”的一部分；而 Naisbitt [NA182 ]則預示從工業(yè)社會到 “信息社會 ”的轉變將對我們的生活產(chǎn)生深遠的影響。軟件就是能夠使我們開發(fā)和利用這種潛能的工具。 今天，情況變化了。嵌入式軟件提供的智能和功能常常使兩 種相似的工業(yè)品或消費品有所區(qū)別。但是另外一些專家意識到這一標題預示著對