Without a parameter, the template inserts a link to the Deutsch catalogue article (a.k.a. Schubert Thematic Catalogue by Otto Erich Deutsch) for compositions by Franz Schubert numbered according to that catalogue.
First parameter ("1") unnamed, omits the link whatever value is given to the parameter (only removes the period/full stop).
"number" parameter, when defined, makes the returned result of the template wikilink to the shortcut redirect to the article on the work (e.g. D. 157), while displaying the link without the period.
For the shortcuts: avoid creation of shortcuts without the period, because some of the numbers in that format are ambiguous, e.g. D 506 needs to disambiguate from Rule D 506.
Examples
edit Lorem {{D.}} 506 ipsum
- → Lorem D 506 ipsum
Lorem {{D.|u}} 506 ipsum
- → Lorem D 506 ipsum
Lorem {{D.|number=506}} ipsum
- → Lorem D 506 ipsum (nbsp between D and 506)
Lorem {{D.|u|number=506}} ipsum
- → Lorem D 506 ipsum (nbsp between D and 506)
Advantages of the unlinked template
editWhy would one use the unlinked template, when the same effect can be achieved with a single keystroke? The advantage is that the layout of all D numbers using the template can be updated simultaneously whatever the current preference on its display → Wikipedia-wide consistency.
Another advantage is that the template inserts a non-breaking space between the D and the number value, even in the unlinked version.