The user interface to the babel system is quite simple. He should specify the languages he wants to use in his document in the list of document-style options. For instance, for a document in which both the English and the Dutch language are used, the first line could read:
\documentstyle[a4,dutch,english]{artikel1}
Please note that in this case the Dutch-specific definitions are inactive when
LATEX has finished processing document-style option files.
If the user then wants to switch from English to Dutch he would include the command
\selectlanguage{dutch}
before starting to write Dutch.
If a user wants to write a document-style option of his own he might like to define a macro that checks which language is in use at the time the macro is executed. For this purpose the macro \iflanguage 〈:〉!:}language 〈:〉!:}then-clause 〈:〉!:}else-clause is available.