When your source file was compiled no definition for these functions was found within the file so it was marked for external linking. During linking VC++ could not find another source or object file that contained the definition for these functions, that is where the "undefined external symbol" error comes from.
In order to resolve this external symbol you will have to provide the necessary files to the linker by either listing the files in your project file list (right-click on your project in the file view and select "add files to project...") or by going into your project's settings and entering the path to the files for which to link (go to Project >> Settings..., select the Link tab, select Input from the drop-down menu, and put the paths you want
to add in the Additional Library Path field).
The file that you need to link against in a program that uses the NI-488.2 API is gpib-32.obj, don't forget to also #include decl-32.h in your source files for function prototypes and constants used in the API as well.
Jason F.
Applications Engineer
National Instruments
www.ni.com/ask
