The help system uses a fast hashed lookup table containing cached file offsets to the entry text. A modular database provides flexibility and portability. The files are located by default in the directories named ``help'' under the library tree, which is usually rooted at /usr/local/xictools. Xic and WRspice allow the user to specify the help search path through environment variables and/or startup files. All of the files with suffix ``.hlp'' in the directories along the help search path are parsed, and reference pointers added to the internal list, the first time the help command is issued in the application. In addition, other types of files, such as image files, which are referenced in the HTML help text may be present as well.
The ``.hlp'' files have a simple format allowing users to create and modify them. Each help item is indexed by a keyword which should be unique in the database. The help text may be in HTML or plain text format. The format is described in A.2.