To view help information, you must specify a help file when calling the WinHelp function. The help file must have the Windows Help (.HLP) file format and have one or more topics. Each topic is a distinct unit of information, such as a conceptual description, a set of instructions, a picture, a glossary definition, and so on. Topics must be uniquely identified so that Windows Help can locate the topic whenever it is requested. Internally, Windows Help uses topic identifiers to locate topics, but applications most often use context identifiers (unique integer values) to specify topics to display. The help file author must explicitly map context identifiers to topic identifiers in the [MAP] section of the project file used to build the help file.
When you specify a help file but you do not specify a path, WinHelp looks for the help file in the Help directory or in a directory specified by the PATH environment variable. In addition, WinHelp can find a help file whose name is listed in the following registry location:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Help
To take advantage of the registry, you must create a value name that has the same name as your help file. The value assigned to that name must be the directory where the help file resides.
If WinHelp cannot find the given help file, it displays a dialog box that allows the user to specify the location of the help file. Because WinHelp saves the location information in the registry, WinHelp does not ask again for the location of the same help file.
For more information about how to author and build a help file, see the documentation provided with your development tools.