Dll is written in c language and function prototype is as follows:-

DLL_EXPORT int HistQueryFlat(
    char *Product, char *Version, char *SType)
{
    int Result;
    char *ItemVersion;
    HIST_ITEM *Item;
    HIST_TYPE Type;
    HIST_HANDLE HistFile;
    HIST_FILE File;
    HIST_STATUS Status;
    HIST_FILTER Filter;
    int SP, Num;
#ifdef LOGGING
    FILE *Log;

Installshield project code :-

**Header file code **
#define PDS_HISTORY_DLL             "pdshist.dll"
 prototype pdshist.HistQueryFlat(STRING, STRING, STRING);

**implementation **

nResult = pdshist.HistQueryFlat(@PRODUCT_NAME, svPdsProductVersionIdentifier, svPdsProdType);