In this document you will find reference information on the differences between "traditional" HLLAPI and the extensions implemented in FlyHLLAPI along with a quick reference set, but without a full, comprehensive reference for the full HLLAPI call set.
With Flynet Viewer, FlyHLLAPI is not recommended for new applications: it is a migration tool for existing HLLAPI applications to the high performance Flynet Viewer environment.
As such, Flynet has decided not to invest in detailed documentation of the full HLLAPI API, since this information is broadly available on the Internet and is, in general, all copied material from the original specifications produced by first, IBM (HLLAPI, EHLLAPI), then a group of vendors that created the WinHLLAPI specification (DCA, Attachmate, Wall Data, Synapse Communications, NetSoft, Microsoft).
If you require additional overviews and details of the programming interfaces or additional API sets, please use your favorite search engine and do a search on "WINHLLAPI Documentation" or "HLLAPI Documentation" or "EHLLAPI Documentation". There is plenty out there and you may just find the documentation for the emulator you originally wrote your HLLAPI application for...