There are two main ways in which wxHelp may be used by other applications. The simplest is via the API (Application Programmer's Interface) included with the wxWindows system, as documented in the reference manual under wxHelpInstance. The other method is to use the DDE (Dynamic Data Exchange) commands on which the API is built. The only reason for doing this might be to access wxHelp from non-wxWindows applications running under Windows 3.1 (such as Visual Basic programs).
Under UNIX, the service name (the identifier for connecting to a DDE server) is generated at random by the API and passed to wxHelp when running it by specifying the -server switch. This is not fool-proof but usually doesn't result in a socket clash.
Under Windows, the service name is always assumed to be ``4000'', since there is only ever one instance of wxHelp running under Windows (a restriction of large model programming).
Listed below are the commands that wxHelp implements by means of a string sent to it using the Execute DDE command. Each string comprises an initial command letter followed by a space, followed by an argument, for example ``f help.xlp''.