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Visual FoxPro Run-Time Libraries

Visual FoxPro includes two run-time libraries for you to distribute with your applications:

  • VFPVersionNumberR.dll

  • VFPVersionNumberT.dll

VersionNumber indicates the version number of Visual FoxPro that you use to develop your applications. These run-time libraries are located in the ..\Program Files\Common Files\Microsoft Shared\VFP directory.

VFPVersionNumberR.dll is the typical run-time library for most application types. VFPVersionNumberT.dll is a special multithreaded run time for highly scalable in-process server applications such as those created for use with Microsoft Transaction Server. Both run-time libraries share the resource file, VFPVersionNumberRENU.dll. For more information, see VFP9R.DLL Run-Time Library and VFP9T.DLL Run-Time Library.

When you build your application from the Project Manager, the build action you choose determines which run-time library the generated application or server uses. Only Automation servers (.dll) can use the VFPVersionNumberT.dll run-time library. The Build method for Project objects also makes it possible for you to choose which run-time library to use. For more information, see How to: Build Automation Servers, How to: Build Applications, and Build Method.


The compiled source file, for example, an executable (.exe) or an Automation server is marked internally to identify which run-time library to use when called. The only way to change the run-time library an Automation server uses is by rebuilding it. Your server can determine at run time which run-time library it is using through the read-only Application StartMode property. You need to know which run-time library is associated with your Automation server so that you can choose the right run time to include in the setup. For more information, see Automation and COM Servers.