論文資料-----計算機軟件外文翻譯資料

1、論文資料-計算機軟件外文翻譯資料1984年2月23日，business week(商業(yè)周刊）頭版醒目地排印了通欄大標(biāo)題“軟件：新動力”。許多專家看到題目，禁不住笑了，評論說這話說得大約晚了10年。但是另外一些專家意識到這一標(biāo)題預(yù)示著對計算機軟件重要性的新的理解。今天，在計算機的歷史上，軟件首次超越了硬件，成為許多企業(yè)、產(chǎn)品以及系統(tǒng)成功的關(guān)鍵要素。其實，軟件常常是區(qū)別彼此的主要因素。軟件（以及相關(guān)數(shù)據(jù)庫）提供的信息，因其完整與適時，才使得公司與其競爭對手有所區(qū)別。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。正是軟件造成這種區(qū)別。在計算機時代的前30年內(nèi)，首要的挑戰(zhàn)是開發(fā)能降

2、低數(shù)據(jù)的處理和存儲費用的硬件。整個80年代，微電子技術(shù)的發(fā)展致使在不斷降低成本的情況下，得到更強的計算能力。今天，情況變化了。首要的挑戰(zhàn)是降低基于計算機的解決方案（用軟件實現(xiàn)的解決方案）的成本以及改進這種解決方案的質(zhì)量。昨天一臺大型計算機上的功能，今天可以在單片集成電路上獲得?，F(xiàn)代硬件令人敬畏的處理和存儲能力代表著計算機的潛能。軟件就是能夠使我們開發(fā)和利用這種潛能的工具。開發(fā)軟件的環(huán)境，一直與計算機系統(tǒng)發(fā)展的四個時代緊密耦合。較好的硬件性能、體積小以及低價位已經(jīng)促使許多復(fù)雜的基于計算機的系統(tǒng)趨于完善。真空管處理器已經(jīng)發(fā)展到了微電子設(shè)備。在關(guān)于“計算機革命”的暢銷書中，osborneosb79將

3、其稱為“新的工業(yè)革命，； toffler tof80 將微電子技術(shù)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(yù)示從工業(yè)社會到“信息社會”的轉(zhuǎn)變將對我們的生活產(chǎn)生深遠(yuǎn)的影響。圖1描述了軟件在基于計算機系統(tǒng)應(yīng)用領(lǐng)域內(nèi)的發(fā)展。在計算機系統(tǒng)發(fā)展初期，硬件經(jīng)歷著不斷地變化，而軟件則是許多人事后才思考的問題。計算機程序設(shè)計就像褲子臀部尺寸變化的藝術(shù)，沒有什么系統(tǒng)的方法。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。在這一過程中，大多數(shù)系統(tǒng)均使用面向批處理的方法。值得注意的例外是交互系統(tǒng)，如早期的美國航空公司的機票預(yù)定系統(tǒng)以及實時的面向防護的系統(tǒng)，

4、如sage（半自動地面環(huán)境）。然而，就絕大部分而言，硬件用于執(zhí)行單一程序，反過來，早期，通用的硬件很常見。而另一方面，軟件則是專為某項應(yīng)用設(shè)計的，因此其應(yīng)用面相對有限。 圖1產(chǎn)品軟件（為出售給一個或多個顧客而開發(fā)的程序）還在發(fā)展初期。大多數(shù)軟件都是由同一個人或組織開發(fā)并最后使用的。同一個人寫軟件，運行軟件，如果失敗，就對其進行調(diào)整。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。由于這種具有個人化特點的軟件環(huán)境，設(shè)計是在個人頭腦中進行的一個不可見過程，文檔常常是不存在的。早期，我們學(xué)會了很多關(guān)于實現(xiàn)計算機系統(tǒng)的知識，但相對對計算機系統(tǒng)工程知之甚少。然而，公正地說，

5、我們必須承認(rèn)在這一時期開發(fā)的許多優(yōu)秀的計算機系統(tǒng)。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。計算機系統(tǒng)發(fā)展的第二個時代是從60年代中期到70年代末這10年，見圖1。多道程序設(shè)計，多用戶系統(tǒng)引人了人機交互的新概念。交互技術(shù)開辟了應(yīng)用的新世界以及硬件和軟件技巧的新水平。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。聯(lián)機存儲設(shè)備的進步導(dǎo)致了第一代數(shù)據(jù)庫管理系統(tǒng)的出現(xiàn)。隨著計算機系統(tǒng)數(shù)目的增長，計算機軟件程序庫開始膨脹。公司內(nèi)部的開發(fā)項目設(shè)計了幾萬條源程序語句。從外部購買的軟件產(chǎn)品又增加了幾十，萬條新語句。麻煩出現(xiàn)了：所有這些程序

6、所有這些源語句若發(fā)現(xiàn)有錯誤，便不得不改正；若用戶要求有變化，就不得不修改；或改寫以適應(yīng)所購的新硬件。這些工作統(tǒng)稱為軟件維護。花費在軟件維護方面的精力，要以其報警率的頻度排除故障源。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。這就出現(xiàn)了軟件危機。計算機系統(tǒng)發(fā)展的第三個時代從70年代中期開始一直延續(xù)到現(xiàn)在：分布系統(tǒng)多計算機，各臺計算機并發(fā)運行并相互通信極大地增加了計算機系統(tǒng)的復(fù)雜程度。全球網(wǎng)和局域網(wǎng)、寬頻帶數(shù)字通信以及日益增長著的對“即時”數(shù)據(jù)訪問的要求，向軟件開發(fā)人員提出了很高的要求。個人計算機一直都是許多軟件公司的發(fā)展動力。盡管第二個時代的軟件公司只賣出了幾百、幾千套，第三個

7、時代的軟件公司卻賣出幾萬、甚至幾十萬套。個人計算機硬件很快成為一種日用品，而軟件則使計算機的特性有所區(qū)別。事實上，在80年代中期，當(dāng)個人計算機銷售增長速度趨于平緩時，軟件產(chǎn)品銷售仍繼續(xù)增長。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。計算機軟件的第四個時代剛剛開始。feigenbaum和mccorduck fei83這些作者預(yù)言：“第五代”計算機及其相關(guān)的軟件將在全世界對政治權(quán)力和工業(yè)權(quán)力的平衡產(chǎn)生深遠(yuǎn)的影響。軟件開發(fā)的第四代技術(shù)(4gt）正在改變著軟件共同體中的某些部門設(shè)計計算機程序的方法。專家系統(tǒng)和人工智能軟件已經(jīng)最終從實驗室轉(zhuǎn)人了現(xiàn)實中各種問題的實際應(yīng)用。隨著

8、第四個時代的來到，軟件危機繼續(xù)加深。現(xiàn)在我們可用下列方式描述軟件危機：1硬件復(fù)雜程序已經(jīng)超出了我們設(shè)計能開發(fā)硬件潛能的軟件的能力。2設(shè)計新程序的能力跟不上對新程序的要求。3維護已有程序的能力受到低劣的設(shè)計和匱乏的資源的威脅。作為對軟件危機的反應(yīng)，軟件工程實踐正應(yīng)用于整個工業(yè)領(lǐng)域。20年前，能夠明智地描繪出“計算機軟件”是什么的人不足1。今天，多數(shù)專業(yè)人員和公眾中不少人在很大程度上都感到他們懂軟件，是這樣嗎？一本講軟件的教科書可能會這樣描述軟件：(1)運行后提供指定功能和性能的指令（計算機程序）；(2)能夠使程序恰當(dāng)?shù)靥幚硇畔⒌臄?shù)據(jù)結(jié)構(gòu)；(3)描述程序操作和使用的文檔。勿容置疑，可以給出更完整的

9、定義，但我們需要的不僅只是一個正式的定義。軟件特點理解軟件（主要是軟件工程），首要的是檢查軟件區(qū)別于其他人工物質(zhì)的特點。造硬件時，人的創(chuàng)造過程（分析、設(shè)計、制造和檢驗）最終轉(zhuǎn)化成物質(zhì)形式。如果制造一臺新計算機，起初的草圖、正式設(shè)計圖和模擬板上的原型演化成為具有超大規(guī)模集成電路芯片、電路板和電源等物質(zhì)產(chǎn)品。軟件是邏輯的而不是物質(zhì)的系統(tǒng)部件。因此軟件具有和硬件完全不同的特點：在過去的五年里，“軟件工廠”的概念一直在文獻(xiàn)中得以討論（例如：man84 , taj84?！败浖S”這一術(shù)語并不意味硬件生產(chǎn)和軟件開發(fā)是等值的。注意到這一點是很重要的。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

10、。軟件不會磨損。“浴缸曲線”表明在硬件壽命的早期，它的故障率相對較高。這些故障往往是由設(shè)計或加工制造中的缺欠所致。缺欠排除后，在某一段時間內(nèi)，故障率降至一個較低的穩(wěn)定的水平?？墒?，隨著時間的推移，由于硬部件受到灰塵、振動、誤用、溫度極限的長期作用和許多其他惡劣環(huán)境的影響，其故障率再度上升。簡言之，硬件開始磨損。軟件不像硬件那樣容易受到惡劣環(huán)境的影響而損耗。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。然而，一旦得以更正，如果沒有其他錯誤，曲線就會變平。很明顯，軟件不會損耗，但確實會惡化。在使用期間，軟件會發(fā)生變化（維修）。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(fù)

11、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。漸漸地最低故障率開始上升，軟件由于多次修改而惡化。磨損的另一方面表明軟件與硬件的區(qū)別。當(dāng)硬部件磨損時，可用備件代替。軟件卻沒有備件。每個軟件故障都說明設(shè)計中有錯誤或在設(shè)計翻譯成機器可執(zhí)行碼的過程中有錯誤。因此軟件維護比硬件維護復(fù)雜得多。多數(shù)軟件是定制的，而不是用現(xiàn)存的組件組裝的。試設(shè)想一下微處理產(chǎn)品的控制硬件的設(shè)計和制造方法。設(shè)計工程師畫一張數(shù)字電路的簡單草圖，做一些基本分析以便確信其功能能夠?qū)崿F(xiàn)，然后查閱數(shù)字器件手冊。每一集成電路（ic或芯片）有一部件編號，一個確定而有效的功能，一個定義完善的接口，和一個標(biāo)準(zhǔn)的集成原則組。挑選好每一

12、組件后，就可取用。令人悲哀的是，軟件設(shè)計者承擔(dān)不起上述的豪華。幾乎無一例外，根本就沒有軟組件目錄。可以預(yù)定某一現(xiàn)成軟件，但只能是一個完整體，而不能是可組裝成新程序的部件。雖然有關(guān)“軟件可重用性”的論述不少（例如big84 )，但是到目前真正成功的卻不多。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。鑒于本單元討論的目的，這里只介紹能直接與機器可執(zhí)行指令相關(guān)的軟件成分。軟件設(shè)計翻譯成語言形式，該語言形式規(guī)定了軟件數(shù)據(jù)結(jié)構(gòu)、過程屬性和相關(guān)要求。語言形式由能把語言轉(zhuǎn)換成機器可執(zhí)行指令的翻譯程序來處理。人類若能通過自然語言（如英語、西班牙語或俄語）與計算

13、機交流是最理想不過了。遺憾的是，大量的詞匯、復(fù)雜的文法和在語境（上下文）基礎(chǔ)上進行的理解妨礙了人機用自然語言進行交流。語義信息處理和自然語言識別領(lǐng)域的研究（例如win83)為人機以自然語作為交流的媒介奠定了基礎(chǔ)。但是，至少在未來的幾年里，寫程序用的語言形式僅限于人工語言。所有的程序設(shè)計語言都是人工語言。每種人工語言都有有限的詞匯量、定義明確的語法和完善的句法和語義規(guī)則。這些屬性對機器翻譯來說是必要的。作為軟件成分之一的語言形式按特征分為機器級語言、高級語言和非過程語言。機器級語言是cpu指令集的符號表示。當(dāng)一個好的軟件開發(fā)者研制出可維護、有良好文檔的程序時，機器語言就能有效地利用存儲器并優(yōu)化程

14、序執(zhí)行速度。而一個設(shè)計拙劣、連文檔都沒有的程序，機器語言有可能加重將要出現(xiàn)的問題。即使機器語言確實提供吸引人的運行速度和存儲特性，它還是有許多嚴(yán)重缺陷：1語言形式的復(fù)雜性和表達(dá)信息的低水平抽象能力延長了實現(xiàn)時間（指編程時間）；2最終的程序難以讀懂；3難以測試；4維護特別難；5不同處理器間無移植性。應(yīng)用機器語言時，軟件“生產(chǎn)效率”極其低下。由于其使用方面的缺點，在未來的10年里，這種語言形式的應(yīng)用范圍可能是有限的。高級語言使軟件開發(fā)人員和程序獨立于機器。當(dāng)使用較復(fù)雜的翻譯程序時，高級語言的詞匯、文法、句法和語義要比機器語言復(fù)雜得多。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。雖然目

15、前有數(shù)百種程序設(shè)計語言在應(yīng)用，但是工業(yè)中廣泛應(yīng)用的高級程序語言不足10個。cobol和fortran語言引人后，廣泛應(yīng)用了近30年。現(xiàn)代程序設(shè)計語言（為過程和數(shù)據(jù)設(shè)計而直接支持現(xiàn)代設(shè)計實踐的語言）如pascal,c和ada正得以廣泛應(yīng)用。專用語言（為特殊應(yīng)用領(lǐng)域設(shè)計的）如smalltalk,apl,lisp和prolog，作為新的應(yīng)用方法從實驗室轉(zhuǎn)向?qū)嶋H使用，正得到廣泛的認(rèn)可。我們已經(jīng)談到了程序語言翻譯程序的功能，即把語言形式轉(zhuǎn)換成機器可運行指令。匯編程序是機器級代碼的翻譯程序，它完成把符號性機器指令轉(zhuǎn)換成機器可執(zhí)行指令的相對簡單的任務(wù)。解釋程序是逐句變換高級語言的翻譯程序。每遇到一條語句，該

16、語句就被轉(zhuǎn)換成機器可執(zhí)行代碼并加以執(zhí)行。apl和basic就是通常用解釋程序加以運行的語言。最常見的高級語言翻譯程序便是編譯程序。通過全面評價一個程序，編譯程序能優(yōu)化存儲容量和或它所生成的機器可執(zhí)行指令的執(zhí)行速度。機器可執(zhí)行指令是軟件最底層的形式。十六進制或其他專用代碼可用來代表能引起特定的cpu處理步驟的二進制位模式。機器代碼、匯編語言（機器級語言）和高級編程語言常被稱作計算機語言的頭三代。用其中任一種語言，程序員都必須既考慮到信息結(jié)構(gòu)的規(guī)定還要考慮程序本身的控制。因此，頭三代語言稱作過程語言。在過去的10年里，出現(xiàn)了一組第四代語言或非過程語言。非過程語言不需要軟件開發(fā)人員規(guī)定過程細(xì)節(jié)，它所

17、指的程序是“規(guī)定指定的結(jié)果而不是規(guī)定達(dá)到其結(jié)果的行為”cob85。支持軟件把結(jié)果說明翻譯成機器可執(zhí)行程序。到目前為止，第四代語言(4gls )已用于數(shù)據(jù)庫應(yīng)用程序和其他商業(yè)數(shù)據(jù)處理領(lǐng)域。軟件應(yīng)用軟件可應(yīng)用在事先規(guī)定的過程步驟（即算法）已被定義的任何情況下（顯然不符合本規(guī)則的例子是專家系統(tǒng)軟件）。信息內(nèi)容和確定性是確定軟件應(yīng)用性質(zhì)的重要因素。內(nèi)容指的是輸人、輸出的信息的意義和形式。例如，許多商業(yè)應(yīng)用程序使用高度結(jié)構(gòu)化的輸人數(shù)據(jù)（數(shù)據(jù)庫）并生成格式化“報表”。控制自動化機器（例如數(shù)控）的軟件接受結(jié)構(gòu)形式有限的離散數(shù)據(jù)項并連續(xù)快速地生成出各條機器命令。信息確定性指輸人數(shù)據(jù)時間和順序的可預(yù)見性。工程分

18、析程序接受預(yù)先定義為順序的數(shù)據(jù)，連續(xù)執(zhí)行分析算法，并以報表或圖表形式給出結(jié)果數(shù)據(jù)。這種應(yīng)用程序就是確定性的。另一方面，多用戶操作系統(tǒng)接受具有變化的內(nèi)容和任意時序的輸人，執(zhí)行可能被外部情況中斷的算法并生成隨環(huán)境和時間作函數(shù)變化的輸出。具有這些特點的應(yīng)用程序是不確定的。很難找到一種有意義的軟件應(yīng)用的通用分類（法）。隨著軟件復(fù)雜性的增加，完全徹底的分類就不存在了。下面的軟件領(lǐng)域說明了軟件潛在應(yīng)用的廣度。系統(tǒng)軟件系統(tǒng)軟件是為其他程序服務(wù)的程序集。某些系統(tǒng)軟件（例如，編譯程序、編輯程序和文件管理實用程序）處理復(fù)雜的但確定的信息結(jié)構(gòu)。其他系統(tǒng)應(yīng)用（如操作系統(tǒng)部件、驅(qū)動程序和遠(yuǎn)程通訊處理器）大量地處理非確定

19、性數(shù)據(jù)。不論在哪種情況下，系統(tǒng)軟件的特點是：頻繁地與計算機硬件交互作用；多用戶頻繁使用；要求調(diào)度、資源共享和復(fù)雜過程的管理的并發(fā)操作；復(fù)雜的數(shù)據(jù)結(jié)構(gòu)和多外部接口。實時軟件當(dāng)實時事件出現(xiàn)時對其進行測量、分析和控制的軟件稱為實時軟件。實時軟件的組成包括：從外部環(huán)境收集信息并使之格式化的數(shù)據(jù)采集部分；傳送應(yīng)用所需信息的分析部分；對外部環(huán)境做出響應(yīng)的控制輸出部分和協(xié)調(diào)全部其余部件以確保實時響應(yīng)（通常由1毫秒到1分鐘）的監(jiān)督部件。應(yīng)該注意術(shù)語“實時”與“交互”或“分時”不同。實時系統(tǒng)必須在嚴(yán)格的時限內(nèi)做出反應(yīng)。通常，交互（或分時）系統(tǒng)可超出響應(yīng)時間而不致造成災(zāi)難性結(jié)局。商業(yè)軟件商業(yè)信息處理是最大的單一軟

20、件應(yīng)用領(lǐng)域。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(nèi)的大型數(shù)據(jù)庫。本領(lǐng)域的應(yīng)用軟件重新建立現(xiàn)有數(shù)據(jù)的結(jié)構(gòu)以便于商務(wù)操作或做出管理決策。除了傳統(tǒng)的數(shù)據(jù)處理任務(wù)以外，商務(wù)軟件還包括交互式計算（例如，銷售點交易處理）。 嵌入式軟件智能產(chǎn)品已經(jīng)成為幾乎每一個顧客和工業(yè)市場的老生常談。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)。嵌入式軟件能夠完成極其有限的秘密功能（例如，用作微波爐的小鍵盤控制）或提供重要功能和控制能力（例如，汽車上的數(shù)字功能，如燃料控制、儀表盤顯示和制動系統(tǒng)等

21、）。個人計算機軟件在過去的10年里，個人計算機（pc）軟件市場極其繁榮。字處理、電子表格、計算機作圖、娛樂、數(shù)據(jù)庫管理、個人和商業(yè)財經(jīng)應(yīng)用、外部網(wǎng)絡(luò)或數(shù)據(jù)庫存取等只是數(shù)百種應(yīng)用中的幾個例子。實際上，在軟件領(lǐng)域，pc軟件仍然代表某些最富創(chuàng)造力的軟件設(shè)計。人工智能軟件人工智能（ai)軟件使用非數(shù)值算法以解決計算或直接分析不能解決的復(fù)雜問題。目前最活躍的人工智能領(lǐng)域是專家系統(tǒng)，又叫做基于知識的系統(tǒng)wat85 o其他的人工智能軟件應(yīng)用領(lǐng)域是模式識別（圖像和聲音）、定理證明和游戲。1984 february 23, business week (business week) of the front p

22、age prominently typographical-column headline "software: new impetus." many experts see the title, could not help smiling, saying this is right about comments late 10. but some other experts aware of this title indicates the importance of computer software on the new understanding. today,

23、in the history of computer software goes beyond the hardware first, as many businesses, products and the system a key element of success. in fact, the distinction between software is often a major factor. software (and related databases) of the information provided, its integrity and the right time,

24、 it makes companies and their competitors are different. embedded software provided by the intelligent and often features two similar industrial products or consumer goods are different. this distinction is causing software. in the computer age of 30 years ago, the primary challenge is the developme

25、nt of data processing can reduce the cost of hardware and storage. throughout the 1980s, the development of microelectronics technology result in continuous cost reduction circumstances, be greater computing power. today, the situation changed. the primary challenge is to reduce computer-based solut

26、ions (using software solutions) and the cost of improving the quality of this solution. yesterday, a large computer functions, this can be obtained on the single-chip integrated circuits. modern hardware awesome handling and storage capacity represents the computer's potential. software that wil

27、l enable us to develop and utilize the potential of this tool. the software development environment, has been working with computer systems development four times tightly coupled. better hardware performance, small size and low-cost has prompted many complex computer-based systems tend to perfection

28、. vacuum tube processor has been developed to the microelectronics equipment. on the "computer revolution" best-selling book, osborne osb79 will be called the "new industrial revolution ' toffler tof80 will be known as the advent of microelectronics technology in human history &qu

29、ot;third wave of change" part; but naisbitt na182 indicates from the industry community to the "information society" will change our lives have a far-reaching impact. figure 1 describes the software in the application of computer-based systems in the field of development. early in the

30、 development of computer systems, hardware undergoing constant change, and personnel software is only after many thought. computer programming like hip pants size changes of art, no systematic approach. software development is in fact out of control, unless there are procedures for lost or prices be

31、gan to soar situation. in this process, the majority of systems in use batch-oriented approach. notable exceptions are interactive systems, such as the early american airlines ticket reservation systems, as well as real-time protection for the systems, such as sage (semi-automatic ground environment

32、). however, the vast majority, the hardware for the implementation of a single procedure, in turn, early, generic hardware are common. on the other hand, the software is designed for a particular application, the application of relatively limited.   figure 1 software products (for the sale to o

33、ne or more customers and the development of the program) is the initial stage of development. most software by the same person or organization to develop and final use. the same person write software, operating software, if it fails, their adjustment. since then changes in the work less, managers ca

34、n rest assured that even if the software has had some problems this person will be on the scene. as a result of this is personal characteristics software environment designed to be carried out in the minds of individuals in an invisible process, documentation often does not exist. early, we learn a

35、lot about the knowledge of the computer, but relatively little knowledge of computer systems engineering. however, fair to say that, we must admit that during this period many outstanding development of the computer system. some of these people today are still being used, but also provided some admi

36、ration for posterity by the astonishing achievements constantly. development of the computer system is the second from 60 times in the mid - to late 1970s, this 10, see figure 1. multi-channel programming, multi-user system for soliciting a new concept of human-computer interaction. interactive tech

37、nology has opened up a new world of applications, as well as hardware and software skills new level. real-time systems from multiple sources of information collection, analysis and transmission of data, thereby using millisecond instead of minutes - control process and production output. the progres

38、s of on-line storage devices led to the first generation of a database management system. along with the increase in the number of computer systems, computer software program for beginning expansion. the company's development projects designed tens of thousands of source files statement. purchas

39、e from external software products added dozens, million of the new statement. trouble emerged: all of these procedures - all of these sources sentence - if mistakes are found, they have to make corrections. if there are changes in user requirements, we will have to revise; or adapted to cope with th

40、e 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

41、to maintain. this appeared software crisis. the development of computer systems from the third era began in the mid-1970s until now: distribution system - more computers, with various computer operation and mutual communication - greatly increased the complexity of computer systems. global networks

42、and local area networks, broadband digital communications and the growing of the "instant" data access request, the software developers raised very high demands. many personal computer software companies has been the driving force for development. despite the second era of software compani

43、es sold only a few hundred, a few thousand sets, the third era of software companies have sold tens of thousands, even hundreds of thousands of sets. personal computer hardware will soon become a commodity, and computer software will enable the characteristics are different. in fact, in the mid-1980

44、s, when the personal computer 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 computer software more money. the fourth computer software era has just begun. feigenbaum

45、and mccorduck fei83 these authors predicted: "fifth-generation" computer and related software in the world will be on political power and the balance of industrial power have a far-reaching impact. the fourth generation of software development technology (4 gt) is changing the software in

46、the community of certain sectors of the computer 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

47、 deepen. now we can describe software crisis following ways: 1. hardware complex 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. main

48、tenance 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 "computer software" is a person less than 1%. today, the majority of prof

49、essionals 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 (computer program); (2) enables the prope

50、r procedures for handling information data structure; (3) a description of procedures for handling and use of documents. not to say, can give a more complete definition, but what we need is not only a formal definition. software features understanding software (mainly software engineering), the firs

51、t inspection software is different from other artificial material characteristics. building hardware, the creation process (analysis, design, manufacture and testing) eventually transformed into material form. if manufacturers a new computer, the initial plan, a formal board layout design and simula

52、tion of the evolution of a prototype of vlsi chips, circuit boards and power supplies, and other material products. the software is a logical rather than physical system components. therefore software and hardware have completely different characteristics: in the past five years, the "software

53、factory" concept has been discussed in the literature (for example: man84, taj84. "software factory" of the term does not mean that the hardware production and software development is equivalent. note that this is a very important point. moreover, "software factory" concept

54、proposals for the development and use of automated software tools. software does not wear. "bathtub curve" that in the early life of the hardware, and its failure rate is relatively high. these failures are often processed and manufactured by design or due to the shortcomings. shortcomings

55、 ruled out after a certain period of time, the failure rate dropped to a lower stable level. however, with the passage of time, as hardware components by dust, vibration, misused, temperature limits and the long-term role of many other bad environmental impact, its failure rate went up again. in sho

56、rt, hardware begun wear. unlike hardware software as vulnerable to the adverse environmental impact of loss. however, in the initial operation of procedures and found no defects will trigger a higher failure rate. however, once can be corrected, if there is no other errors, will curve flattening. ob

57、viously, the software will not wear and tear, but it does deteriorate. in use, the software will be any change (maintenance). revised software, it may lead to some new defect, failure rate increased, in the failure rate curve back to the initial steady-state failure rate before and the need for anot

58、her revision, the result of the rise again. gradually the lowest failure rate began to increase, the software has been revised many times and because of the deterioration. wear on the other hand shows that the distinction between software and hardware. when the hardware components wear, available sp

59、are parts to replace. the software did not spare parts. each software fault in the design of all the mistakes in the design or translated into machine executable code in the course of the mistakes. therefore software maintenance much more complex than the hardware maintenance. most software is customized, rather than using the existing components of the assembly. try imagine th