The current generation of MS help systems is known as HTML Help, probably because it uses HTML as a content format and in some of its other files. This was first introduced in August, 1997 [http://www.helpware.net/htmlhelp/hh_info.htm] and was distributed with Win98 and Win2K. It uses the IE browser engine, with a special ActiveX control to provide extra capabilities to HTML pages.
The content resides in self-contained files called "Compiled HTML Help file[s]" (CHM). The HTML Help viewer (HH), compiler (HHC) and most decompilers (e.g. istorage) use an IStorage interface to access the virtual filesystem in the file. The virtual filesystem will be discussed in a later chapter and section. It is interesting to note that most of the file data in the filesystem is compressed in one big chunk with LZX (an LZ77 based compressor obtained from the Amiga community). The GUI authoring tools are known as HTML Help Workshop (HHW), which calls MS' compiler (HHC), which loads a dll (HHA) to do all the work.
HTML Help includes quite a few features that are useful to both the documentation author and user; table of contents, index, full-text search, bookmarks, context-sensitivity, custom navigation tabs, merged help and a simple UI.