計算機專業(yè)vb外文翻譯---visual basic 語言與算法

1、<p>　　Visual Basic language and arithmetic</p><p>　　The United States launched the Microsoft Visual Basic (may be referred to VB), is the latest version of the current VB 2008 Beta2 (VB9) Chinese versio

2、n. </p><p>　　Visual meaning the visual, visible, referring to the development of operating systems like windows graphical user interface (Graphic User Interface, GUI) method, it does not need to prepare a la

3、rge number code to describe the appearance of the interface elements and location, as long as the pre - The establishment of good drag and drop objects on the screen corresponding to the location. </p><p>　　

4、Basic is actually an abbreviation of the phrase; this phrase is Beginners all-purpose symbolic instruction code, the Chinese meaning "to the initial directive GM symbol code language." </p><p>　　Vi

5、sual Basic learning, Professional Edition and Enterprise Edition versions to meet the different needs of the development. Study and apply to the ordinary version of the majority of learners and the use of Visual Basic de

6、velopment of the general staff of Windows applications, but; professional version for computer professional development of staff, including the study of functional version of the full content control and Internet develop

7、ment tools such as advanced features ,Enterprise contain n</p><p>　　Visual Basic </p><p>　　Section 1 the summary of Visual Basic </p><p>　　Microsoft Visual Basic,( abbreviate VB )as

8、 tool the most of application program one of under Windows operating platform. No matter beginner or professional developer, VB has all offered a whole set of tools to them, Development application program that it can be

9、 relaxed and convenient. So VB as most computer first-selected the ABC of programming language of beginner. </p><p>　　" Visual" mean method to adopt visual user of development figure interface (GUI

10、), need and write a large number of code go and describe interface appearance and position of element seldom, Tow and show controlling part that need corresponding position to get screen can help figure design interface,

11、 user of figure,; " Basic" means BASIC language, because VB is developed on the basis of already existing BAISC language. </p><p>　　VB is a kind of programming language in common use of Microsoft,

12、It, including VBA of the numerous Windows application software use VB language in Microsoft Excel, Microsoft Accessed., For users to carry on the secondary development; Make web page use more VBScript script language sub

13、 collection of VB too at present. </p><p>　　Utilize data of VB visit characteristic user can establish the data base to most data base forms including Microsoft SQL Server and other enterprises data base Wit

14、h the application program of front, and adjustable service end part. Utilize ActiveX(TM) technology, VB can use word processor, electronic data list he Windows function that application program offers extremely, Excel of

15、 Microsoft,, Word of Microsoft,, Even can use by VB specialty edition or enterprise application program and target th</p><p>　　The procedure that users established finally is a real .EXE file , can issue fre

16、ely . </p><p>　　VB offer study edition, the specialty edition and enterprise edition, use to satisfied with different development demands. Study edition make programming personnel develop Windows and Windows

17、 application program of NT very easily. The specialty edition has offered the developing instrument with complete function to programming personnel of the specialty, Include studying all functions of edition in the speci

18、alty edition. Enterprise edition allow the professional personnel to establish strong dis</p><p>　　Section 2 integrated development environments </p><p>　　Integrated environment of VB call IDE,

19、made up of a lot of parts , include title board, menu fence, tool fence, controlling part case, And window body window, engineering management device window, attribute window, code window and window body overall arrangem

20、ent window body overall arrangement, etc. of designing etc.. Have covered all functions, such as design which develops the application program, editting, compiling and debugging, etc.. </p><p>　　In VB, the a

21、pplication program calls the project too. When start VB and open a new project for the first time, can see and pursue integrated development environment interface that show. </p><p>　　Visual Basic Integrated

22、 development environment </p><p>　　VB come and organize development of application program through project, use project come and manage and form files of application program. One project uses the environment

23、 to make up by several window bodies, standard module generally. The system manages project through the project menu, for instance add the window body, quote . System allow turn on and manage a lot of projects besides. &

24、lt;/p><p>　　Section 3 Visual Basic language brief introductions </p><p>　　Basic use and do the elementary high-level language that used often most. Its full name is Beginner' s All-purpose Symb

25、olic Instruction Code, abbreviate as BASIC. As its name suggests, Basic one specially for language that beginner design, because it easy to learn easy to know, So the body is popular. Early Basic language to belong to an

26、d solve translating type, so can carry out line by line , So it can see the result carried out at once , this is a very convenient design for beginner. But it ha</p><p>　　The language is the basic compositio

27、n, which forms VB procedure. VB has stipulated the form of sentences and function. </p><p><b>　　Grammar: </b></p><p>　　The sentence defines incantations [Sentence body] </p>&

28、lt;p>　　Sentence define agree with and used in fixed function of sentence, sentence body appoint concrete content or want concrete operation that carry out of sentence. All set of sentence VB language, carry on with VB

29、 sentence organic association finish a certain specific function the procedure. Interface + procedure can solve a certain application problem. </p><p>　　VB application program code window write in" code

30、 editing machine" generally. " editing machine of code" is like the word processing software of a piece of height specialization, there are many easies function of writing VB code, Pursue to show [Example

31、Ex-Hello ]In" code editing machine" code that window written. </p><p>　　“Editing machine of code” window </p><p>　　Section 4 develop the application program with Visual Basic </p>

32、;<p>　　Use VB programming, design appearance of application program first generally, write every target procedure code or other treatment procedure of incident respectively, Work of programming should be light mor

33、e. </p><p>　　The procedure of establishing the application program is as follows: </p><p>　　Establish application program interface </p><p>　　The interface is the mutual bridge of u

34、ser and procedure, Generally formed of window body and vision frame of the button, menu, text frameset. with standard WINDOWS interface of application program that VB establish. Require according to function of procedure

35、 and user and need of information interchange of procedure, Come to confirm that need those targets , plan the overall arrangement of the interface. </p><p>　　2. Design by each attributes of target in interf

36、ace </p><p>　　Demand and set up each attribute of target such as appearance, name,, size of targeted. according to interface of planning. </p><p>　　Most attribute person who fetch can set up thr

37、ough the attribute window when design already, Too can set up revising when operating in procedure through programming in procedure code. Have the targets respond programming by procedure code </p><p>　　3. R

38、espond procedure code of programming target </p><p>　　Interface determine appearance of procedure only, design window add codes through" code editing machine" soon after the interface, Realize some

39、 make the tasks, such as responding, information processing,etc. after accepting external message, Add code , realize some response, information processing that make after accepting external information task, As editor&#

40、39;s window of code pursued shows add codes </p><p>　　“code editing machine” window </p><p>　　4. Keep project </p><p>　　One VB procedure one project, at the time of designing a appl

41、ication program, system will set up one be expanded and called. Project file of vbp, project file include all relevant information of file that project set up this, Keep project keep associated documents of project this

42、at the same time. For example the window body produced when design interfaces is kept and being expanded and being called. Frm sum. In the window body of foxfire. At the time of opening a project( file), this project re&

43、lt;/p><p>　　5. Operate and debugged by procedure </p><p>　　Operate the procedure thoroughpin operate" selecting in the menu, when the mistake appears, VB system can offer information prompt ca

44、n looked for and get rid of the mistake thoroughpin debug" within operate" menus too. </p><p>　　6. Can produce by executive program </p><p>　　For make procedure can break away from VB

45、environment, order to become next life through" file"" producing project 1.exe" of menu but executive program (eyeful), Can carry out this file directly after this. In produce, + executive program, an

46、d then through install guide bale all associated documents, Can run independently after installation under the environment of windows 9 x/2000 as a software product.</p><p>　　In computer system's any sof

47、tware, is by the every large or small each kind of software constituent constitution, defers to the specific algorithm to realize respectively, the algorithm quality direct decision realizes the software performance fit

48、and unfit quality. Designs the algorithm with any method, what resources designs the algorithm to need, requires how many running time, how many storage space, how to determine an algorithm the quality, when realizes a s

49、oftware, is must give to solve. </p><p>　　The algorithm is the problem-solving step, we may define the algorithm Cheng Jie a determination class question the random one special method. In the computer scienc

50、e, the algorithm needs to use the computer algorithmic language to describe, the algorithm represents with the computer solves a kind of question precisely, the effective method. The algorithm construction of data = proc

51、edure, solves one to assign may calculate or the solvable question, the different person may compile the different </p><p>　　But the algorithm has certain characteristic, it includes:① Determinism. Algorithm

52、 each kind of operation must have the determination significance, this kind of operation should carry out what kind of movement should not to have the ambiguity, the goal is clear;② Effectiveness. Requests the operation

53、which in the algorithm waits for realizing is basic, each kind of operation can at least completes in the principle by the human with the paper and the pen in the limited time;③ Input. An algorithm </p><p>　

54、　Satisfies a first four characteristic group of rule not to be able to be called the algorithm, can only be called the computational process, the operating system is a computational process example, the operating system

55、uses for to manage the computer resources, controls the manufacture industry movement, when has not made industry the movement, the computational process does not stop, but is at the waiting status.</p><p>　

56、　The algorithm complexity is the algorithm efficiency measure, when appraises the algorithm performance, the complexity is an important basis. The algorithm complex degree with moves computer resources how many which thi

57、s algorithm needs related, needs the resources are more, indicated that this algorithm the complexity is higher; Needs the resources are less, indicated that this algorithm the complexity is lower.</p><p>　　

58、The spatial resources, which computer’s resources, operate most importantly, needs the time which and the stored routine and the data need, the algorithm complexity has division time complexity and the spatial complexity

59、.</p><p>　　The algorithm carries out the operation on the computer, needs the data which certain storage space depositing description algorithm the procedure and the algorithm need, the computer completes th

60、e operation task to require certain time. The procedure which writes according to the different algorithm places when on the computer operates, needs the time and the space are different, the algorithm complexity is need

61、s the time and the spatial one kind of measure to the algorithm operation. The diffe</p><p>　　Regarding question, which assigns willfully, a profitable target which designs, the complex low algorithm is as f

62、ar as possible when designs algorithm considered. Moreover, when the question, which assigns already when has many kinds of algorithms, an important criterion which choice complexity low, is when selects algorithm should

63、 follow. Therefore, the algorithm complex analysis or selects to the algorithm design has the important guiding sense and the use value.</p><p>　　When discussion algorithm complexity, two questions need to c

64、larify:</p><p>　　(1)An algorithm's complexity expresses with what kind of quantity;</p><p>　　(2)How to calculate one to assign the algorithm the complexity. After finding solves a question

65、 the algorithm, is this algorithm realization, as for whether could find the method which realized, was decided in the algorithm circularity and the computation complexity, whether this question did have the solution alg

66、orithm, whether to provide the time resources which and the spatial resources the algorithm needed.</p><p>　　Visual Basic 語言與算法</p><p>　　1991年，美國微軟公司推出了Visual Basic(可簡稱VB），目前的最新版本是VB 2008 Beta2(

67、VB9)中文版。</p><p>　　Visual 意即可視的、可見的，指的是開發(fā)像windows操作系統(tǒng)的圖形用戶界面（Graphic User Interface,GUI）的方法，它不需要編寫大量代碼去描述界面元素的外觀和位置，只要把預先建立好的對象拖放到屏幕上相應(yīng)的位置即可。</p><p>　　Basic 實際上是一個短語的縮寫，這個短語就是 Beginners all_purpo

68、se symbolic instruction code ，其中文意思為“初始者通用符號指令代碼語言”。Visual Basic有學習版、專業(yè)版和企業(yè)版三種版本，以滿足不同的開發(fā)需要。學習版適用于普通學習者及大多數(shù)使用Visual Basic開發(fā)一般Windows應(yīng)用程序的人員，但是；專業(yè)版適用于計算機專業(yè)開發(fā)人員，包括了學習版的全部內(nèi)容功能以及Internet控件開發(fā)工具之類的高級特性；企業(yè)版除包含專業(yè)版全部的內(nèi)容外，還有自動化構(gòu)件管

69、理器等工具，使得專業(yè)編程人員能夠開發(fā)功能強大的組骨子里分布式應(yīng)用程序。</p><p>　　Visual Basic </p><p>　　第1節(jié)Visual Basic的概述 </p><p>　　Microsoft Visual Basic(簡稱VB)是在Windows操作平臺下設(shè)計應(yīng)用程序的最速度、最簡捷的工具之一。不論是初學者還是專業(yè)開發(fā)人員，VB都為他們提

70、供了一整套的工具，可以輕松方便的開發(fā)應(yīng)用程序。因此，VB一直被作為大多數(shù)電腦初學者的首選入門編程語言。 </p><p>　　“Visual”指的是采用可視化的開發(fā)圖形用戶界面（GUI）的方法，一般不需要編寫大量代碼去描述界面元素的外觀和位置，而只要把需要的控件拖放到屏幕上的相應(yīng)位置即可方便圖形設(shè)計圖形用戶界面；“Basic”指的是 BASIC語言，因為VB是在原有的BAISC語言的基礎(chǔ)上發(fā)展起來的。 </

71、p><p>　　VB是 Microsoft的一種通用程序設(shè)計語言，它包括在 Microsoft Excel、Microsoft Access等眾多Windows應(yīng)用軟件中的VBA都使用VB語言，以供用戶進行二次開發(fā)；目前制作網(wǎng)頁使用較多的VBScript腳本語言也是VB的子集。 </p><p>　　利用VB的數(shù)據(jù)訪問特性用戶可以對包括 Microsoft SQL Server和其他企業(yè)數(shù)據(jù)庫

72、在內(nèi)的大部分數(shù)據(jù)庫格式創(chuàng)建數(shù)據(jù)庫和前端應(yīng)用程序，以及可調(diào)整的服務(wù)端部件。利用ActiveX(TM)技術(shù)，VB可使用 Microsoft Word字處理器、Microsoft Excel電子數(shù)據(jù)表極其他Windows應(yīng)用程序提供的功能，甚至可直接使用由VB專業(yè)版或企業(yè)版創(chuàng)建的應(yīng)用程序和對象。 </p><p>　　用戶最終創(chuàng)建的程序是一個真正的.EXE文件，可以自由發(fā)布。 </p><p>

73、　　VB提供了學習版，專業(yè)版和企業(yè)版，用以滿足不同的開發(fā)需求。學習版使編程人員很容易地開發(fā)Windows和Windows NT的應(yīng)用程序。專業(yè)版為專業(yè)編程人員提供了功能完備的開發(fā)工具，專業(yè)版中包含了學習版的所有功能。企業(yè)版允許專業(yè)人員以小組的形式來創(chuàng)建強大的分布式應(yīng)用程序。它包括專業(yè)版的所有的特性。所以可以根據(jù)不同的需要來選擇不同的版本。 </p><p>　　第2節(jié)集成開發(fā)環(huán)境 </p><

74、p>　　VB的集成環(huán)境或稱IDE，由多個部分組成，包含了標題欄、菜單欄、工具欄、控件箱，以及窗體設(shè)計器窗口、工程管理器窗口、屬性窗口、代碼窗口和窗體布局窗體布局等。覆蓋了開發(fā)應(yīng)用程序的設(shè)計、編輯、編譯和調(diào)試等所有功能。 </p><p>　　在VB中，應(yīng)用程序也稱工程。當?shù)谝淮螁覸B并打開一個新工程時，可以看到如圖所示的集成開發(fā)環(huán)境界面。 </p><p>　　Visual Bas

75、ic 集成開發(fā)環(huán)境 </p><p>　　VB通過工程來組織應(yīng)用程序的開發(fā)，使用工程來管理構(gòu)成應(yīng)用程序的所有文件。一個工程一般由若干個窗體、標準模塊以及應(yīng)用環(huán)境組成。系統(tǒng)通過工程菜單來對工程進行管理，如添加窗體、引用等。系統(tǒng)允許同時打開和管理多個工程。 </p><p>　　第3節(jié)Visual Basic語言簡介 </p><p>　　Basic是最常被用來做入門使

76、用的高級語言。它的全名是 Beginner’s All-purpose Sumbolic Instruction Code，簡稱為 BASIC。顧名思義，Basic就是一種專為初學者設(shè)計的語言，因其易學易懂，所以身受歡迎。早期的Basic語言都是屬于解譯式的，因此可以一行一行地執(zhí)行，所以它可以立刻看到執(zhí)行的結(jié)果，對初學者來說這是很方便的設(shè)計。不過它也因此沒有結(jié)構(gòu)化的概念，在程序的維護及管理上比起其他語言困難許多。不過在后期的Basic則

77、改正了以上的缺點（如Quick Basic），使得它也可以用來開發(fā)較大型的程序。 </p><p>　　語言是構(gòu)成VB程序的基本成分。VB規(guī)定了語句格式和功能。 </p><p><b>　　語法： </b></p><p>　　語句定義符[語句體] </p><p>　　語句定義符用于規(guī)定語句的功能，語句體指定語句的具

78、體內(nèi)容或要執(zhí)行的具體操作。所有語句的集合就是VB語言，用VB語句進行有機組合完成某個特定功能就是程序。界面+程序就能解決某個應(yīng)用問題。 </p><p>　　VB應(yīng)用程序代碼一般在“代碼編輯器”窗口編寫?！按a編輯器”像是一個高度專門化的字處理軟件，有很多便于編寫VB代碼的功能，圖所示為[例Ex-Hello]在“代碼編輯器”窗口編寫的代碼。 </p><p>　　“代碼編輯器”窗口 <

79、;/p><p>　　第4節(jié)用Visual Basic開發(fā)應(yīng)用程序 </p><p>　　使用VB編程，一般先設(shè)計應(yīng)用程序的外觀，然后再分別編寫各對象事件的程序代碼或其他處理程序，編程的工作要輕松多。 </p><p>　　創(chuàng)建應(yīng)用程序的步驟如下： </p><p>　　1． 創(chuàng)建應(yīng)用程序界面 </p><p>　　界面是用

80、戶和程序交互的橋梁，用VB創(chuàng)建的標準的WINDOWS應(yīng)用程序的界面一般由窗體和按鈕、菜單、文本框的圖象框等構(gòu)成。根據(jù)程序的功能要求和用戶與程序之間的信息交流的需要，來確定需要那些對象，規(guī)劃界面的布局。 </p><p>　　2． 設(shè)計界面上各個對象的屬性 </p><p>　　根據(jù)規(guī)劃的界面要求設(shè)置各個對象的屬性，比如對象的外貌、名稱、顏色、大小等。 </p><p&g

81、t;　　大多數(shù)屬性取值既可以在設(shè)計時通過屬性窗口來設(shè)置，也可以在程序代碼中通過編程在程序運行時設(shè)置修改。 </p><p>　　3． 編程對象響應(yīng)的程序代碼 </p><p>　　界面僅僅決定了程序的外觀，設(shè)計完界面后就要通過“代碼編輯器” </p><p>　　窗口來添加代碼，實現(xiàn)一些在接受外界信息后作出響應(yīng)、信息處理等任務(wù)，添加代碼，實現(xiàn)一些在接受外界信息后作出

82、的響應(yīng)、信息處理等任務(wù)，添加代碼如圖的代碼編輯窗口所示 </p><p>　　“代碼編輯器”窗口 </p><p><b>　　4． 保存工程 </b></p><p>　　一個VB程序就是一個工程，在設(shè)計一個應(yīng)用程序時，系統(tǒng)會建立一個擴展名為.vbp的工程文件，工程文件包含了該工程所建立的所有文件的相關(guān)信息，保存工程就同時保存了該工程的所有相

83、關(guān)文件。比如當設(shè)計界面時產(chǎn)生的窗體保存在擴展名為.frm和.frx的窗體文件中。在打開一個工程（文件）時，該工程有關(guān)的所有文件同時被裝載。 </p><p>　　5． 行和調(diào)試程序 </p><p>　　通過“運行”菜單中的選項來運行程序，當出現(xiàn)錯誤時， VB系統(tǒng)可以提供信息提示也可通過“調(diào)試”和“運行”菜單來查找和排除錯誤。 </p><p>　　6．生成可執(zhí)行程

84、序 </p><p>　　為了使程序可以脫離VB環(huán)境，通過“文件”菜單中的“生成工程1.exe”命令來生成可執(zhí)行程序（.exe文件），此后即可直接執(zhí)行該文件。在生成可+執(zhí)行程序后，再通過安裝向?qū)⑺邢嚓P(guān)文件打包，就可以作為一個軟件產(chǎn)品在windows 9x/2000 環(huán)境下安裝后獨立運行</p><p>　　VB的數(shù)據(jù)庫編程方面按其難易程度可分為三類(由易到難);</p>

85、<p>　　●使用數(shù)據(jù)庫控制項和綁定控制項</p><p>　　●使用數(shù)據(jù)庫對象變量進行編程</p><p>　　●直接調(diào)用ODBC2.0API</p><p>　　在使用VB進行數(shù)據(jù)庫編程時,通常,會首先選擇三種基本方法之一來進行數(shù)據(jù)庫應(yīng)用程序的方案設(shè)計, 現(xiàn)在就將以上三種設(shè)計方法的適應(yīng)范圍及其優(yōu)缺點進行一個比較。</p><p>

86、;　　1 使用數(shù)據(jù)庫控制項和綁定控制項</p><p><b>　　1.1優(yōu)點</b></p><p>　　它是三種方法中編碼量最小的</p><p>　　不必了解CDBC2.0API的細節(jié)</p><p>　　允許使用標準的和第三方廠商制訂的控制項</p><p><b>　　

87、簡化了錯誤處理</b></p><p>　　支持所有的動態(tài)集方法及屬性</p><p><b>　　1.2缺點</b></p><p>　　不能存取快照對象(snapshop)對象或表格對象(都屬于記錄集對象)</p><p>　　不能存取數(shù)據(jù)庫集合,比如表定義(TableDefs)字段(Fieds),

88、索引( Indexes)及查詢定義(QueryDefs)</p><p>　　只能存取部分ODBC2.0管理函數(shù)</p><p>　　不能進行真正的事務(wù)處理</p><p>　　有限的錯誤診斷功能</p><p><b>　　1.3應(yīng)用</b></p><p>　　對中小規(guī)模的數(shù)據(jù)庫表(通

89、常少于一千條記錄)只進行簡章的瀏覽操作</p><p>　　基本SQL查詢所對應(yīng)的結(jié)果集長度有限(通常結(jié)果集的記錄數(shù)小于一百, 這些記錄從一個或兩個長度有限的表中檢索出來)</p><p>　　應(yīng)用程序的數(shù)據(jù)輸入/輸出項較少(通常只涉及一個或兩個長度有限的表、并且表中的字段數(shù)在10個左右且不具有關(guān)系完整性限制</p><p>　　2 使用數(shù)據(jù)庫對象變量進行編程&

90、lt;/p><p><b>　　2.1 優(yōu)點</b></p><p>　　可以在程序中存取ODBC2.0的管理函數(shù)</p><p>　　可以控制多種記錄集類型:Dynaset、Snapshop及Table記錄集合對象</p><p>　　可以存取存儲過程和查詢動作</p><p>　　可以存取數(shù)據(jù)庫集

91、合對象,例如TableDefs、Fields、Indexes及QueryDefs</p><p>　　具有真正的事務(wù)處理能力 , 包括啟動事務(wù) ( Begintrans) 、 提交事務(wù)(CommitTrans)及回滾事務(wù)(Rollback)</p><p><b>　　2.2 缺點</b></p><p>　　比使用數(shù)據(jù)控制項的方法編碼量較大&

92、lt;/p><p>　　只能進行間接的錯誤處理和錯誤恢復</p><p>　　對每個數(shù)據(jù)庫操作沒有細粒度的控制</p><p>　　對結(jié)果集和包含結(jié)果集的內(nèi)豐資源的操作受到限制</p><p>　　同直接使用ODBC2.0API函數(shù)的方法相比性能較低</p><p><b>　　2.3 應(yīng)用</b>&

93、lt;/p><p>　　應(yīng)用程序需要在執(zhí)行期間動態(tài)地建立表、字段及索引.</p><p>　　應(yīng)用程序涉及同步更新幾張表(但在邏輯上保持一致性)的復雜事務(wù)</p><p>　　應(yīng)用程序使用結(jié)果集而不是Dynaset的窗體(FORMS),例如Snapshots或Tables,這里是設(shè)計要考慮的關(guān)鍵</p><p>　　應(yīng)用程序的表非常大,多于100

94、0條記錄</p><p>　　應(yīng)用程序具有復雜的數(shù)據(jù)輸入/輸出項,它涉及許多內(nèi)部相關(guān)的字段并且包括數(shù)據(jù)庫參照完整性或一致性規(guī)則</p><p>　　應(yīng)用程序需要執(zhí)行一些額外的操作和對結(jié)果集的查詢后處理, 尤其是需要很高的數(shù)據(jù)格式化顯示</p><p>　　應(yīng)用程序需要利用復雜的ODBC管理功能以選擇、配置、校驗及建立各種數(shù)據(jù)源</p><p>

95、;　　應(yīng)用程序需要在執(zhí)行期間“顯示”數(shù)據(jù)庫的基本結(jié)構(gòu)</p><p>　　應(yīng)用程序需要使用復雜的多碼索引方式來檢索或更新記錄</p><p>　　3 直接調(diào)用ODBC2.0API</p><p><b>　　3.1 優(yōu)點</b></p><p>　　可以直接參與結(jié)果集的開發(fā)、管理及規(guī)范化</p><p

96、>　　對結(jié)果集游標提供了更多的控制,并且提供了更多的游標類型和執(zhí)行動作</p><p>　　能夠確定ODBC驅(qū)動程序及SQL的一致性級別</p><p>　　可以更好地控制Windows的執(zhí)行調(diào)度及資源利用</p><p>　　其他方面同其他方法差不多,因此這種方法很可能具有最好的性能</p><p><b>　　3.2 缺點

97、</b></p><p>　　較其他兩種方法需要大量的代碼</p><p>　　代碼復雜并且要求程序員具有編制API調(diào)用的經(jīng)驗</p><p>　　在網(wǎng)絡(luò)上Visual Basic運行期間庫的錯誤處理缺乏安全性,因此代碼運行期間出現(xiàn)的錯誤所造成的后果會非常嚴重</p><p><b>　　3.3 應(yīng)用</b>

98、</p><p>　　如果系統(tǒng)環(huán)境為客戶機/服務(wù)器模式下的大規(guī)模多用戶環(huán)境,那么應(yīng)用程序必須都能夠準確地解決可能出現(xiàn)的系統(tǒng)錯誤和失敗</p><p>　　應(yīng)用程序強調(diào)資源使用,這里如何對內(nèi)存、 網(wǎng)絡(luò)服務(wù)器資源進行直接控制是首要的考慮因素</p><p>　　應(yīng)用程序使用超大規(guī)模數(shù)據(jù)庫,例如數(shù)據(jù)庫表可能包含幾萬或幾十萬條記錄</p><p>　

99、　計算機系統(tǒng)中的任何軟件，都是由大大小小的各種軟件組成部分構(gòu)成，各自按照特定的算法來實現(xiàn)，算法的好壞直接決定所實現(xiàn)軟件性能的優(yōu)劣。用什么方法來設(shè)計算法，所設(shè)計算法需要什么樣的資源，需要多少運行時間、多少存儲空間，如何判定一個算法的好壞，在實現(xiàn)一個軟件時，都是必須予以解決的。計算機系統(tǒng)中的操作系統(tǒng)、語言編譯系統(tǒng)、數(shù)據(jù)庫管理系統(tǒng)以及各種各樣的計算機應(yīng)用系統(tǒng)中的軟件，都必須用一個個具體的算法來實現(xiàn)。因此，算法設(shè)計與分析是計算機科學與技術(shù)的一個

100、核心問題。</p><p>　　算法是解題的步驟，我們可以把算法定義成解一確定類問題的任意一種特殊的方法。在計算機科學中，算法要用計算機算法語言描述，算法代表用計算機解一類問題的精確、有效的方法。算法+數(shù)據(jù)結(jié)構(gòu)=程序，求解一個給定的可計算或可解的問題，不同的人可以編寫出不同的程序，來解決同一個問題，這里存在兩個問題：一是與計算方法密切相關(guān)的算法問題；二是程序設(shè)計的技術(shù)問題。算法和程序之間存在密切的關(guān)系。算法是一組

101、有窮的規(guī)則，它們規(guī)定了解決某一特定類型問題的一系列運算，是對解題方案的準確與完整的描述。制定一個算法，一般要經(jīng)過設(shè)計、確認、分析、編碼、測試、調(diào)試、計時等階段。對算法的學習包括五個方面的內(nèi)容：① 設(shè)計算法。算法設(shè)計工作是不可能完全自動化的，應(yīng)學習了解已經(jīng)被實踐證明是有用的一些基本的算法設(shè)計方法，這些基本的設(shè)計方法不僅適用于計算機科學，而且適用于電氣工程、運籌學等領(lǐng)域；② 表示算法。描述算法的方法有多種形式，例如自然語言和算法語言，各自有

102、適用的環(huán)境和特點；③確認算法。算法確認的目的是使人們確信這一算法能夠正確無誤地工作，即該算法具有可計算性。正確的算法用計算機算法語言描述，構(gòu)成計算機程序，計算機程序在計算機上運</p><p>　　而算法具有一定的特性，它包括：① 確定性。算法的每一種運算必須有確定的意義，該種運算應(yīng)執(zhí)行何種動作應(yīng)無二義性，目的明確；② 能行性。要求算法中有待實現(xiàn)的運算都是基本的，每種運算至少在原理上能由人用紙和筆在有限的時間內(nèi)完

103、成；③ 輸入。一個算法有0個或多個輸入，在算法運算開始之前給出算法所需數(shù)據(jù)的初值，這些輸入取自特定的對象集合；④ 輸出。作為算法運算的結(jié)果，一個算法產(chǎn)生一個或多個輸出，輸出是同輸入有某種特定關(guān)系的量；⑤ 有窮性。一個算法總是在執(zhí)行了有窮步的運算后終止，即該算法是可達的。滿足前四個特性的一組規(guī)則不能稱為算法，只能稱為計算過程，操作系統(tǒng)是計算過程的一個例子，操作系統(tǒng)用來管理計算機資源，控制作業(yè)的運行，沒有作業(yè)運行時，計算過程并不停止，而是處