Use of the DCE messaging API is very straightforward. In the application code itself, all that is usually required is simply to call one of the output routines, passing it the ID of the message to be output. The messages themselves must first be defined in a text file which must then be processed by the DCE sams (symbols and message strings) utility, which generates the message catalog file along with other C source files that contain code necessary to facilitate the additional layer of functionality that DCE has added to the XPG4 message catalog mechanism.
More:
A Simple DCE Messaging Example
The DCE Message Interface and sams Input and Output Files