Context-sensitive HTML Help function call

What code do the developers write so context-sensitive Help works with an application? They write what's known as a context-sensitive HTML Help function call.

The code looks something like this:

HtmlHelp(hWnd,       /*Window handle of program or dialog*/

    "CSHHelp.chm",   /*Name of the CHM file*/

    HH_HELP_CONTEXT,

    dwMapNumber);    /*Map number from map file*/

Note: Information enclosed in /* */ characters are developer's comments.