27.3 User Programs & API

User Programs are custom programs written in Visual C++ or Visual Basic using Microsoft Development tools. These use the Applications Programming Interface (API) supplied with WebAccess. The API makes calls to the SCADA Node and these user programs must run on the SCADA node.

Note – there is a scripting language in WebAccess based on Tcl, which can accomplish most tasks. See Scripts for more information on Screen Scripts and Global Scripts.

User Programs using the API are recommended only for experienced Visual C++ or Visual Basic developers with Microsoft Certification.

Most users should use Scripts in WebAccess.

You must use a tag ID number to get information from WebAccess SCADA Node using the API calls. All calls use the Tag ID number only. You build a list of Tag ID numbers using the GetId() call and the tag name. Note that changes to the WebAccess Database will change the association of Tag ID and Tag name. Every time you start your User Program or WebAccess Restarts, you should rebuild you Tag ID list.

The APIs in this chapter should be used only in user program, or the behavior could not be guaranteed.