Visualbasic language
Visual Basic(VB) is an event-driven programming language developed by Microsoft, which includes an auxiliary development environment. By any standard, VB is the most widely used language in the world-not only the developers who praise VB, but also the developers who complain about VB. It comes from the BASIC programming language. VB has a graphical user interface (GUI) and a rapid application development (RAD) system, so it can easily connect to a database or create ActiveX controls using DAO, RDO and ADO. Programmers can easily use the groups provided by VB to quickly build an application.
Development history
199 1 year, Microsoft released Visual Basic 1.0 version. This caused a great sensation at that time. Many experts believe that the emergence of VB is an epoch-making event in the history of software development. In fact, from our current point of view, the function of VB 1.0 is really too weak; (But recently VB 6.0, VB. NET function is still quite big! )。 But at that time, Yan was the first "visual" programming software. This makes programmers enjoy it and try to create software on the platform of VB. Microsoft also lost no time in launching three versions of VB2.0, VB3.0 and VB 4.0? Starting from VB3, Microsoft integrated the database driver of ACCESS into VB, which greatly improved the database programming ability of VB. Since VB4, VB has also introduced the idea of object-oriented programming. VB is powerful @ easy to learn. Moreover, VB also introduces the concept of "control", which makes a large number of compiled VB programs available. Directly used by us. In 2002. NET 2002 (v7.0) came out, in 2003, Visual Basic. NET 2003 (v7. 1), and in 2005, Visual Basic 2005 (v8.0) came out. At the same time, a free simplified version of Visual Basic 2005 and an accelerated version of Visual Basic 2005 are introduced for beginners and students of Visual Basic. Although Visual Basic 2005 Express Edition is a free version, Microsoft requires users of this version to register and obtain the product registration code on Microsoft's website before they can use it, otherwise Visual Basic 2005 Express Edition can only run for 30 days. The obvious advantage of VB2005 is that you can directly write XP-style buttons and other controls. But the short sequence it writes takes up nearly 10MB of memory. After several years of development, it has become a professional development language and environment. Users can quickly create Windows programs with Visual Basic, and now they can write enterprise-level client/server programs and powerful database applications.
A language derived from VB
Microsoft has developed a series of scripting languages about VB.
-VBA VBA, which is included in Microsoft applications (such as Microsoft Office) and third-party products (such as WordPerfect Office). VBA is embedded in various applications, which seems contradictory, but its function is as powerful as VB.
-VBscript is the default ASP language and can also be used for Windows scripts and web page coding. Although its grammar is similar to VB, it is a completely different language. VBS does not make VB runtime run, but is executed by Windows script host. The difference between these two languages reflects the performance of ASP website. When Microsoft is ready to develop a new programming tool, the first decision is whether to change the most sought-after old VB6 or re-establish a new tool for engineering development. Microsoft later developed Visual Basic. NET, which is the successor of VB, is also. NET platform. VB.net programming language is an object-oriented programming language, which is not completely compatible with VB.
language feature
The central idea of VB is to make programmers simple, whether novice or expert. Using VB, the GUI system of application program can be established simply, but it can also develop quite complicated programs. VB program is a combination of visual components based on forms, which adds? Code that specifies the generated properties and methods. Because the nature and methods of tacit understanding have been partially defined in the software, programmers can complete a simple program without writing too much code. In the past, the performance problems of VB programs were always put on the desktop, but with the rapid improvement of computer speed, the debate about performance has become less and less. The addition and change of form controls are realized by drag-and-drop technology. A toolbox full of controls to display available controls (such as text boxes or buttons). Each control has its own properties and events. The default property value will be provided when the control is created, but the programmer can also change it. The attribute value can be changed with the user's actions and modifications at runtime, thus forming a "one size fits all". Dynamic program. For example, code that can change the position of a control is added to a small change event of a form. Whenever the user changes the window size at run time, the control will also change its position. By adding the corresponding code in the text change event in the text box, the program can automatically interpret or block the input of certain characters when inputting text. A VB program can contain one or more forms, or a main form and multiple sub-forms, similar to the appearance of an operating system. Dialog windows with few functions (such as forms without maximize and minimize buttons) can be used to provide pop-up functions? Components of VB may or may not have a user interface. In this way, the server-side program can handle the added module. VB uses the method of parameter calculation to collect garbage, which contains a large number of objects and provides basic object-oriented support. Because more and more organizations appear, engineers can choose their own extension libraries. Really? Different languages, VB is case-insensitive, but mapping can automatically convert keywords into standard case, forcing the entities at the entrance of the symbol table to follow the writing rules. By default, string comparisons are case sensitive, but this feature can be turned off. VB has made many external controls? Have your own living space. Provides a large number of third-party components for VB. VB also provides a way to build, use and reuse these controls, but it is not easy to create another control from one application due to language problems.
school term
When discussing Visual Basic, you often hear the following terms @, so it is very helpful to have a basic understanding of these terms.
control
Simply put, controls are graphical tools used to form or build Visual Basic applications, including windows, buttons, check boxes, list boxes and data controls? Table controls, picture controls, etc.
event
Actions triggered by the user or the operating system. Examples of events are keystroke, mouse click, double mouse click, time limit or receiving data from a terminal.
way
The program code embedded in the object definition determines how the object processes information and responds to events. For example, a database object has the basic elements of a method program that opens a recordset and moves from one record to another. It contains attributes that define its characteristics, define its tasks, and identify the events it can respond to. Controls and forms are examples of all objects in Visual Basic.
target
Controls, tables, etc. Kind of a couple.
process
A code segment written to accomplish certain tasks, and procedures are usually used to respond to certain events. It can be used as a user-defined function of an application.
attribute
Attributes are concrete descriptions of the attributes of the objects that make up the user interface. Such as size, location, color, width, height, etc. The "objects" mentioned above are all called attributes of the control. Attributes determine the appearance and sometimes the behavior of an object. Most of the attributes of the object have been predefined in VB, but some attributes need to be defined in the application process. Property can provide data for the object @ and retrieve information from the object.
Controversy about VB
opposition
VB is a controversial language: many programmers have strong feelings about the quality of VB programs. Many people think that VB is not worth their use, and that it is a language used by children and programmers. It was a simple language from the beginning. Some features in C++ and Java do not appear in VB. While feeling the convenience and speed of post, some functions similar to compile-time type and declaration checking are turned off by default. While lamenting the usability of VB, some programmers generally look at an error similar to "undefined type" in dismay. Some critics think that the simple features of VB will make it harmful in the future. Many people have taught themselves VB, but they should not have learned good programming habits. When VB enters the classroom, students will not learn many basic sequential technologies and structures, because many technologies have been packaged in user-visible components. Don't learn standard programming habits, because VB has stinging characteristics, which leads to some inexplicable codes. Moreover, many errors and warnings are turned off by default, and programmers find hidden errors very quickly. Experienced programmers will turn on these options when programming in VB. Many critics criticized Microsoft for simply copying the idea of BASIC into VB. Edsger Dijkstra, a famous computer scientist, famously said, "If a student learns BASIC at the earliest, it is almost impossible for him to learn excellent programming, because these people have given up hope. 1"(Dijkstra has no mercy on Fortran, PL/ 1, COBOL and APL. What's another joke? "Real programmers don't need BASIC. Only/kloc-children under 0/2 years old can use it. "
-It's not that simple. The program it develops can only run in Microsoft Windows.
-It's too big. Visual Studio needs several disks to install. VB programs also need a runtime with the size of 1.4M when they leave the factory.
There is an error in the IDE.
-VB can't integrate the basic API of Windows well, so it is very difficult to program with low-level operation. The low-level memory operation of C language is much simpler than VB.
supporter
However, many supporters of VB explain that the ease of use of VB is its greatest advantage, which allows experienced VB programmers or people who only know the basic knowledge to develop programs quickly in their own way. In addition, VB programs can connect to the database very simply. For example, controls can be used to bind databases? In this way, the program written in VB can master all the information of the database without writing a line of code. Multilingual features such as GoSub, On Error and using the last character of variable names to determine the declaration type (such as string str$) all come from V. The syntax of VB is different from most languages, which may confuse new programmers. For example, the sound "Dim a, b, c As Integer" declares that C is an integer variable, but A and B are Variant types. There are also some features that are better than using the underscore character "_" in one line of code. Some programmers use it because it is not standardized and leads to errors.
abstract
VB will attract more praise and criticism, and will continue to be used by users and programmers. It is very suitable for developing user-friendly programs (compared with terminal data), but not suitable for developing other programs (such as joint computing programs).
Features that VB doesn't have
-Legacy. Both VB5 and VB6 are object-oriented programming languages. Yes, it does not contain inheritance features. VB provides special functions, but it still can't meet the needs of programmers. Visual Basic。 NET contains all the object-oriented features.
-Multi-threading support
-Exception handling. Try-Catch-Finally was used against Zhang Chang in VB.net. In VB, there is only the statement "Go to line when an error occurs".
-Support for pointers is very limited.
-VB can only support 8-32-bit plastic surgery, and many languages support it infinitely.
-VB does not allow constant changes in any array. VB does not support the above functions, and programmers need self-reported construction methods to realize similar functions.
VB revolution
VB 1.0 is published in 199 1. This progressive interface between the programming language and the user interface is called Tripod (sometimes called Ruby). The original design was completed by Alan Cooper.
time line
-1991April, released by Visual Basic1.0 for Windows.
-1992 September, Visual Basic 1.0 DOS version was released.
-19921/month, released by VB2.0. The reliability and speed of the previous version have been improved.
-/kloc-0 released VB3.0 in the summer of 993, which is divided into standard version and professional version. It contains a data engine, which can directly interpret the Access database.
-1995 In August, VB4.0 released a 32-bit version and a 16-bit version. It includes support for classes.
-1997 February, released by VB5.0. Programmers can use the 32-bit version to enter the 16-bit program created by version 4.0, and can easily compile it. It also includes self-control of users? Support.
-1998 summer, released by VB6.0.
-200 1, by visual Basic.net and. NET framework. Because it uses new cores and functions? So many VB programmers have to rewrite their programs.
-2003, Visual Basic.net 2003 and. NET framework 1. 1 release.
-In 2004, Microsoft opened the beta version of Visual Studio. NET 2005 (code name Whidbey). That contains the beta version. Network framework 2.0
-In 2005, Microsoft announced that it no longer supported Africa. VB online edition. The VB community immediately responded to Guan Zhong's news, and some old users also submitted petitions hoping to continue to provide technical support for VB. Wei is unwilling to change his decision at present.
-Visual Studio.net 2005 will be released on June 7th, 2005.
Overview: The next version of Microsoft Visual Basic mainly has the following three improvements: Web forms, Web services and object-oriented grammar. Web forms enable experienced Visual Basic users to develop network applications as simply as writing independent programs now. Through the SOAP interface, Web services allow you to configure your designed components anywhere you can connect to the Internet. In addition, several key improvements of object-oriented language make Visual Basic code as flexible as C++, including inheritance, polymorphism and overloading. In this regard, you can refer to Steve Ballmer's "VB its keynote on the next generation of visual basic".
Visual Basic has undergone many improvements. However, I have always liked it since its birth: at its core, you can still write your program as in 199 1 year. Of course, compared with that time, its software package has been greatly enhanced, but these improvements are generally complementary, and the purpose of being a programming tool itself is not vague. The purpose of this is to make Visual Basic design, write and debug excellent object-oriented applications more easily and quickly.
The currently used version of Visual Basic 6.0 introduces WebClasses as a simplified method to configure robust network-oriented applications. In fact, WebClasses provides a large number of methods to transplant programs to the network through common tools. (For a detailed discussion on the extensibility of Visual Basic 6.0 under the network, please refer to Ted Pattison's "Advanced Basic Knowledge Column" (Microsoft Internet Developer1published in October 1999).
Recently, I learned that the next version of Visual Basic plans to make some new improvements. The main improvement is that in terms of storage capacity, the storage capacity available to developers has tripled. The next version of Visual Basic plans to adopt a function called Web Forms in the Visual Studio environment. Web Forms represents a brand-new component-based network solution. Web service will become a new XML-based solution, which publishes the event handling function of the middle layer through standard network protocols. At the same time, Visual Basic language will contain some structures that developers have been demanding for a long time, which makes Visual Basic conform to the familiar object-oriented programming habits of C++ and Java users. These improvements will be announced in the next beta version of Visual Basic.
The changes in the next version of Visual Basic are amazing. If you want to get the benefits they bring, use them. If you don't want to, you can use what you are still using. However, it is beneficial to know that the functions realized by C++ and Java can also be realized by a language like Visual Basic, which is much easier to use than C++ and Java.
Future development trend
What impression did this preview give you? This question is good, but you can find the answer. In the past year, we can clearly see the changes in ASP development. These development programs are often composed of some easy-to-read ASP scripts, and the whole program runs on the basis of these scripts. Because ASP interprets and executes the whole script code, people gradually discover the inherent limitations of this technology when assembling various components. I hear more and more developers say that they want to completely separate the event handling function from the script code and put it into a faster compilation model. These models are all written in c++ or Visual Basic and assembled through COM interface.
Visual Basic can satisfy all the reasons you can think of. Designing components with Visual Basic is actually better than using VBScript or JScript? How hard it is. You can write code that is faster and can easily meet your needs. After the release of the next version of Visual Basic, you can use Visual Basic to generate network-oriented objects, which are compatible with ASP. In a word, taking the route of component combination will be considered as the best choice now and in the future.
As I mentioned earlier, Internet-oriented applications written in Visual Basic (and WebClasses) have a broad foundation. The problem is that most WebClasses-based applications are poorly designed. They don't distinguish the different levels of the application well, and confuse the process of the middle layer with the user interface based on DHTML.
The next version of Visual Basic will introduce WebClasses, a carefully selected network development tool. Because it is more extensible, more powerful and truly language-independent. It applies to all tools of Visual Studio. If you pay attention to some basic rules of multi-tier development, you can easily complete this transformation. Pay special attention to separating the middle layer process from the display layer process. It is strongly recommended to refer to Windows when performing these tasks. The architecture of DNA 2000. The core event handling functions must be completed in the middle layer, and you can use various components written in your favorite compilation language to realize these functions. Then, assemble these components into an ASP script file so that they can work together. It would be ideal if most logical operations were placed in event objects instead of scripts. This is not only a good idea to transition to Web services in the future, but also a practice worthy of emulation.