Keyword indexes are similar to book indexes—the keywords are analogous to first-level entries, and the topics containing the keywords are analogous to second-level index entries. A keyword index consists of a list of index entries, or keywords. In a book index, each entry includes a page reference, which tells the reader where to find the indexed information. In a keyword index, each keyword includes a list of topics (the electronic equivalent of “page references”), which tells users where to find the information associated with that particular keyword. Just as you can have more than one reference following a single index entry in a book, you can assign the same keyword to more than one topic in the Help file.
When a user chooses the Search button, a dialog box appears that lists all the keywords associated with each topic in the upper half of the dialog box. The user types a word or selects one from the list and then chooses the Show Topics button. Help lists all the topics containing the selected keyword in the lower half of the dialog box. (Remember, topics are identified by the $ footnote.) Figure 6.7 shows how the sample application has the keyword “open” in two topics: “PLACEHOLDER” and “PLACEHOLDER.”
The user can double-click a topic in the list box to display that topic in the main Help window.