KEY CONCEPTS ABOUT WINHELP FILES
================================

 1) A Windows help file consists of several seperate blocks or "files",
    organized via a simple file system *within* the help file.  Each of
    these "internal files" serves a different purpose within the larger
    help file.
    
    Overview of the WinHelp file system:	whifs.txt
    Overview of the internal files:		files.txt
    
 2) Many of these internal files are arranged as B-Trees, and act as lookup
    tables to help the WinHelp program find help text.  In particular,
    a special directory file lists the offsets of all the other internal
    files.
    
    Overview of the directory file:		whifs.txt
    Overview of WinHelp B-Trees:		b_tree.txt
    
 3) The actual help text is usually compressed two ways:  first with phrase
    replacement, and then with a simplified LZ77 compression algorithm.
    The compression algorithm may be proprietary to Microsoft; at this point,
    we don't know.
    
    The modified LZ77 algorithm:		compress.txt
    The phrase replacement system:		phrases.txt
    
 Finally, the file hypertxt.txt explains how some key hypertext concepts are
 represented in a WinHelp file.
 
 
 Written by:  Peter Milley
 Feb 22, 1993
