VBScript Reference Manual for InduSoft Web Studio - ICP DAS

VBScript Reference ManualInduSoft Web StudioVBScript Hosting EnvironmentsWhile much of the material contained in the document covers the VBScript language and its use forIWS applications, it is important to understand conceptually how VBScript works in an IWS environment.If you browse the web for information on VBScript, you will likely find a plethora of information, butmany of the examples are for running VBScript with ASP using the Windows Scripting Host.VBScript was developed using a Microsoft technology called ActiveX scripting, which is a COM-basedspecification that allows the development of runtime engines for virtually any scripting language. Otherscripting languages include JScript. VBScript can create an instance, or instantiate, a COM object, andthus through VBScript, many system features can be controlled such as ActiveX Controls, theFIleSystemObject (providing access to the Windows file system), Microsoft Office Automation (COM),and ActiveX Database Objects (ADO).The VBScript Scripting Engine runs on a host, and there are several hosts that can run VBScript (orany ActiveX Scripting-compliant engines) including Windows Scripting Host and Microsoft InternetExplorer. VBScript can be used in conjunction with Windows Scripting Host (WSH) to automate systemadministration tasks. WSH is part of the Microsoft operating system and treats a VBScript applicationlike a powerful batch file. VBScript applications can also be found with Web-based shell views. Mostfrequently, VBScript is used with Active Server Pages (ASP) for Server-side web applications andMicrosoft Internet Explorer for Client-side web applications.Stating with Version 6.1, IWS is now a host for the VBScript Scripting Engine. When used inconjunction with IWS, IWS becomes the only host for the VBScript Scripting Engine that is used. WSHis not used by IWS, even though WSH may be resident on the PC running the IWS application.InduSoft has placed implemented VBScript host environment in a manner that is logically consistentwith the current IWS application development environment and licensing method. What this means isthat there are multiple locations in the development environment where VBScript code segments canbe located (so the code is located close to its use), and restrictions placed on the scope of proceduresand variables. In IWS, there is no such thing as a Global Variable that is accessible by any VBScriptcode segment. The IWS tags and built-in procedures can be accessed by any VBScript code segment.The restrictions and interaction with IWS tags and built-in functions implemented by the IWS VBScriptHost are covered in more detail in the VB Configuration and Operation in IWS section.The VBScript Scripting Engine performs a few key functions. It performs syntax checking in thedevelopment environment (e.g. right mouse click on a VBScript Interface, then select Check Script). Italso interacts with IntelliSense, an auto-completion tool that provides reference to available functions(VBScript and IWS), IWS tags and ActiveX Controls (name, Properties and Methods). And mostimportantly, it executes the VBScript code at runtime, providing error messages if an error occurs. Itshould be noted that unlike most programming languages, VBScript is not compiled; it runs in aninterpreted mode. The VBScript Scripting Engine (vbscript.dll) is responsible for interpreting (via theVBScript Parser, a part of the VBScript Scripting Engine) and executing the VBScript statements, and itdoes so quite efficiently. IWS uses Version 5.6 or later of the Microsoft VBScript Scripting Engine.There are no limitations on the number of VBScript variables supported in IWS, however the amount ofstorage for VBScript variables is determined by the amount of memory available in your system.VBScript variables do not count against IWS tag limits for licensing purposes.10 InduSoft, Ltd.