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|Paradigm||Object-based and Event-driven|
6.0 / 1998
|Typing discipline||Static, strong|
|OS||Microsoft Windows and MS-DOS|
|Microsoft Visual Studio|
|Visual Basic .NET, Gambas, Xojo, Basic4ppc and NS Basic|
Visual Basic is a third-generation event-driven programming language and integrated development environment (IDE) from Microsoft for its Component Object Model (COM) programming model first released in 1991 and declared legacy during 2008. Microsoft intended Visual Basic to be relatively easy to learn and use. Visual Basic was derived from BASIC and enables the rapid application development (RAD) of graphical user interface (GUI) applications, access to databases using Data Access Objects, Remote Data Objects, or ActiveX Data Objects, and creation of ActiveX controls and objects.
A programmer can create an application using the components provided by the Visual Basic program itself. Over time the community of programmers developed third-party components. Programs written in Visual Basic can also use the Windows API, which requires external function declarations.
The final release was version 6 in 1998 (now known simply as Visual Basic). On April 8, 2008, Microsoft stopped supporting Visual Basic 6.0 IDE. The Microsoft Visual Basic team still maintains compatibility for Visual Basic 6.0 applications on Windows Vista, Windows Server 2008 including R2, Windows 7, Windows 8, Windows 8.1, Windows Server 2012, Windows 10 and Windows Server 2016 through its "It Just Works" program. In 2014, some software developers still preferred Visual Basic 6.0 over its successor, Visual Basic .NET. In 2014 some developers lobbied for a new version of the VB6 programming environment. In 2016, Visual Basic 6.0 won the technical impact award at The 19th Annual D.I.C.E. Awards. A dialect of Visual Basic, Visual Basic for Applications (VBA), is used as a macro or scripting language within several Microsoft applications, including Microsoft Office.
Like the BASIC programming language, Visual Basic was designed for an easy learning curve. Programmers can create both simple and complex GUI applications. Programming in VB is a combination of visually arranging components or controls on a form, specifying attributes and actions for those components, and writing additional lines of code for more functionality. Since VB defines default attributes and actions for the components, a programmer can develop a simple program without writing much code. Programs built with earlier versions suffered performance problems, but faster computers and native code compilation has made this less of an issue. Though VB programs can be compiled into native code executables from version 5 on, they still require the presence of around 1 MB of runtime libraries. Core runtime libraries are included by default in Windows 2000 and later, but extended runtime components still have to be installed. Earlier versions of Windows (95/98/NT), require that the runtime libraries be distributed with the executable.
Forms are created using drag-and-drop techniques. A tool is used to place controls (e.g., text boxes, buttons, etc.) on the form (window). Controls have attributes and event handlers associated with them. Default values are provided when the control is created, but may be changed by the programmer. Many attribute values can be modified during run time based on user actions or changes in the environment, providing a dynamic application. For example, code can be inserted into the form resize event handler to reposition a control so that it remains centered on the form, expands to fill up the form, etc. By inserting code into the event handler for a keypress in a text box, the program can automatically translate the case of the text being entered, or even prevent certain characters from being inserted.
Visual Basic can create executables (EXE files), ActiveX controls, or DLL files, but is primarily used to develop Windows applications and to interface database systems. Dialog boxes with less functionality can be used to provide pop-up capabilities. Controls provide the basic functionality of the application, while programmers can insert additional logic within the appropriate event handlers. For example, a drop-down combination box automatically displays a list. When the user selects an element, an event handler is called that executes code that the programmer created to perform the action for that list item. Alternatively, a Visual Basic component can have no user interface, and instead provide ActiveX objects to other programs via Component Object Model (COM). This allows for server-side processing or an add-in module.
The runtime recovers unused memory using reference counting, which depends on variables passing out of scope or being set to Nothing, avoiding the problem of memory leaks that are possible in other languages. There is a large library of utility objects, and the language provides basic support for object-oriented programming. Unlike many other programming languages, Visual Basic is generally not case-sensitive--though it transforms keywords into a standard case configuration and forces the case of variable names to conform to the case of the entry in the symbol table. String comparisons are case sensitive by default. The Visual Basic compiler is shared with other Visual Studio languages (C, C++). Nevertheless, by default the restrictions in the IDE do not allow creation of some targets (Windows model DLLs) and threading models, but over the years, developers have bypassed these restrictions.
Visual Basic builds upon the characteristics of BASIC.
Truehas numeric value -1. This is because the Boolean data type is stored as a two's complement signed integer. In this construct -1 evaluates to all-1s in binary (the Boolean value
True), and 0 as all-0s (the Boolean value
False). This is apparent when performing a (bitwise)
Notoperation on the two's complement value 0, which returns the two's complement value -1, in other words
True = Not False. This inherent functionality becomes especially useful when performing logical operations on the individual bits of an integer such as
Not. This definition of
Trueis also consistent with BASIC since the early 1970s Microsoft BASIC implementation and is also related to the characteristics of CPU instructions at the time.
OPTION BASEwas introduced by ANSI, with the standard for ANSI Minimal BASIC in the late 1970s.
? Round(2.5, 0)gives 2,
? Round(3.5, 0)gives 4.
/) so that division of one integer by another produces the intuitively correct result. VB provides a specific integer divide operator (
\) that does truncate.
Variant. However this can be changed with Deftype statements such as
DefStr. There are 12
Deftypestatements in total offered by Visual Basic 6.0. The default type may be overridden for a specific declaration by using a special suffix character on the variable name (
$for String, and
@for Currency) or using the key phrase
As (type). VB can also be set in a mode that only explicitly declared variables can be used with the command
Visual Basic 1.0 was introduced in 1991. The drag and drop design for creating the user interface is derived from a prototype form generator developed by Alan Cooper and his company called Tripod.[discuss] Microsoft contracted with Cooper and his associates to develop Tripod into a programmable form system for Windows 3.0, under the code name Ruby (no relation to the later Ruby programming language). Tripod did not include a programming language at all. Microsoft decided to combine Ruby with the Basic language to create Visual Basic. The Ruby interface generator provided the "visual" part of Visual Basic, and this was combined with the "EB" Embedded BASIC engine designed for Microsoft's abandoned "Omega" database system. Ruby also provided the ability to load dynamic link libraries containing additional controls (then called "gizmos"), which later became the VBX interface.
Some of the derived languages are:
Earlier versions of Visual Basic (prior to version 5) compiled the code to P-Code only. The P-Code is interpreted by the language runtime. The benefits of P-Code include portability and smaller binary file sizes, but it usually slows down the execution, since having a runtime adds an additional layer of interpretation. Visual Basic applications require Microsoft Visual Basic runtime MSVBVMxx.DLL, where xx is the relevant version number, either 50 or 60. MSVBVM60.dll comes as standard with Windows in all editions from Windows 98 to Windows 7 (some editions of Windows 7 do not include it). A Windows 95 machine would however require inclusion with the installer of whichever DLL was needed by the program. Visual Basic 5 and 6 can compile code to either native or P-Code but in either case the runtime is still required for built in functions and forms management.
Criticisms levelled at Visual Basic editions prior to VB.NET include:
All versions of the Visual Basic development environment from 1.0 to 6.0 were retired by Microsoft by 2008, and are therefore no longer supported. The associated runtime environments are also unsupported, except for the Visual Basic 6 core runtime environment, which Microsoft officially supports for the lifetime of Windows 8 and Windows 10. Third party components that shipped with Visual Studio 6.0 are not included in this support statement. Some legacy Visual Basic components may still work on newer platforms, despite being unsupported by Microsoft and other vendors. Documentation for Visual Basic 6.0, its application programming interface and tools is best covered in the last MSDN release before Visual Studio.NET 2002. Later releases of MSDN focused on .NET development and had significant parts of the Visual Basic 6.0 programming documentation removed as the language evolved, and support for older code ended. Although vendor support for Visual Basic 6 has ended, and the product has never been supported on the latest versions of Windows, key parts of the environment still work on newer platforms. It is possible to get a subset of the development environment working on 32-bit and 64-bit versions of Windows Vista, Windows 7, Windows 8, and Windows 10.
The following code snippet displays a message box saying "Hello, World!" as the window loads:
Private Sub Form_Load ' Execute a simple message box that says "Hello, World!" MsgBox "Hello, World!" End Sub
This snippet makes a counter that moves up 1 every second (a label and a timer control need to be added to the form for this to work) until the form is closed or an integer overflow occurs:
Option Explicit Dim Count As Integer Private Sub Form_Load Count = 0 Timer1.Interval = 1000 ' units of milliseconds End Sub Private Sub Timer1_Timer Count = Count + 1 Label1.Caption = Count End Sub
You can choose a language based on how easy it is to learn. For beginners, Visual Basic is a good choice. [~snip] A big advantage of Visual Basic is that it is a popular language since it is easy to learn.
Summary of positive issues: Visual Basic is easy to learn and widely available.
Trueis mapped to a non-zero numeric value, often 1 or -1.
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