In a PM application, symbolic names are typically used within an application to represent numeric values such as message classes or control window identifiers by a meaningful name rather than a less meaningful numeric representation. A list of suggested prefixes is given in Table "Type Prefixes for Symbolic Constants", to give an indication of type when using a symbolic name or constant.
These one-, two- or three-letter prefixes may be concatenated with the actual symbolic names of control windows, window classes etc., in order to provide a more meaningful representation of the symbolic name in the source code.