VBScript (short for Visual Basic Scripting Edition) is an Active Scripting language developed by Microsoft. The language's syntax reflects its history as a limited variation of Microsoft's Visual Basic programming language. VBScript is installed by default in every desktop release of the Windows Operating System (OS) since Windows 98 and may or may not be included with Windows CE depending on the configuration and purpose of the device it is running on. It initially gained support from Windows administrators seeking an automation tool more powerful than the batch language first developed in the late 1970s. A VBScript script must be executed within a host environment, of which there are several provided on a standard install of Microsoft Windows (Windows Script Host, Windows Internet Explorer). Additionally, The VBScript hosting environment is embeddable in other programs, through technologies such as the Microsoft Script control (msscript.ocx).
When employed in Microsoft Internet Explorer, VBScript is similar in function to JavaScript, as a language to write functions that are embedded in or included from HTML pages and interact with the Document Object Model (DOM) of the page, to perform tasks not possible in HTML alone. Other web browsers such as Firefox, and Opera do not have built-in support for VBScript. This means that where client-side script is required on a web site, developers almost always use JavaScript for cross-browser compatibility.
Besides client-side web development, VBScript is used for server-side processing of web pages, most notably with Microsoft Active Server Pages (ASP). The ASP engine and type library, asp.dll, invokes vbscript.dll to run VBScript scripts. VBScript that is embedded in an ASP page is contained within <% and %> context switches.
VBScript can also be used to create applications that run directly on a person's computer running Microsoft Windows. The simplest example of this is a script that makes use of the Windows Script Host (WSH) environment. Such a script is usually in a stand-alone file with the file extension .vbs. The script can be invoked in two ways. Wscript.exe is used to display output and receive input in through a GUI, such as dialog and input boxes. Cscript.exe is used in a command line environment.
VBScript .vbs files can be included in two other types of scripting files: .wsf files, which are styled after XML; and .hta files, which are styled after HTML. .wsf files can be executed using wscript.exe or cscript.exe, just like .vbs files, and .wsf files can include multiple .vbs files. As a result .wsf files provide a means for code reuse: one can write a library of classes or functions in one or more .vbs files, and include those files in one or more .wsf files to use and reuse that functionality in a modular way.
Another employment of VBScript is the HTML Application, or HTA (file extension .hta). In an HTA, HTML is used for the user interface, and a scripting language such as VBScript is used for the program logic. HTAs run inside of mshta.exe, which is a 'Trusted Application Environment' provided by Internet Explorer. The 'Trusted Application Environment', implies that HTAs do not suffer the restrictions applied to applications running in the web or intranet zone, such as accessing local files or network paths. Although HTAs run in this 'trusted' environment, querying Active Directory can be subject to Internet Explorer Zone logic and associated error messages.
Lastly, VBScript (and JScript) can be used in a .wsc file to create a Windows Script Component - an ActiveX-enabled script class that can be invoked by other COM-enabled applications.
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