ftp://ftp.microsoft.com/developr/drg/WinHelp/ftsrch.zip

WinHelp Full-Text Search Interface for Windows 95 and Windows NT 3.51

The WinHelp system of Window 95 and Windows NT 3.51 provides full-text 
indexing and searching. Whenever you go to the "Find" tab, you invoke 
that engine. If the HLP file(s) which you're using haven't been indexed, 
a "Find Wizard" will create indexes for you. If you'd like to index other 
text files, you can call the full-text APIs directly. You"ll find an 
overview description of how to use the full-text engine (FTSrch.dll) in 
the file FTSAPI.rtf. Then you can use the header file FTSIFace.h to write 
code to drive FTSrch. You can use LoadLibrary and GetProcAddress to connect 
to the FTSrch APIs, or you can use the FTSRCH.def file to construct a LIB 
file and staticly bind to the FTSRCH APIs.

FTSRCH.ZIP contains three files. FTSAPI.RTF is an overview of the FTSrch
interfaces and documentation for each API. FTSIFace.h is a C language
header file for FTSrch, which ships as part of the Windows NT 3.51 SDK.
FTSrch.def is a list of exported functions, which is useful for building a
LIB file which matches the FTSrch.dll.