Include the SMSAPI.H file in source files that use the SMS API.
The SMSAPI.H file is the header file for the SMS API. It is located in the \MSSDK\INCLUDE directory of the Platform SDK CD-ROM.
Note that SMSAPI.H includes three other header files: QRYCODES.H, OBJECTTY.H, and SMSINFO.H. These files are also located in the \MSSDK\INCLUDE directory of the Platform SDK CD-ROM.
When building your application, you must also statically link SMSAPI.LIB and OBJECTTY.LIB. These static libraries are located in the \MSSDK\LIB\platform directory of the Platform SDK CD-ROM, where platform is the processor type of your build environment and target processor platform.