Sometimes it is desirable to document aspects of a package outside 
the source-files. For this reason the system creates a link to files 
using the extension .txt. The referenced file is processed 
as Wiki source. The two fragments below illustrate the relation between 
an
.pl file and a .txt file.
%! read_setup(+File, -Setup) is det. % % Read application setup information from File. The details % on setup are described in setup.txt.
---+ Application setup data If a file =|.myapprc|= exists in the user's home directory the application will process this data using setup.pl. ...