OFS (Olsak's Font System) is a set of Plain TeX and LaTeX macros for managing large font collections; it has been used by Czech/Slovak users for many years. Main features include:

• Mapping from long names of fonts to the metric file name. The user can specify only exact long names in documents.
• Support for many font encodings.
• Printing of catalogues of fonts and test samples of font families; the interactive macro \showfonts shows all font families you have installed via OFS.
• The user interface is the same for Plain TeX and for LaTeX, but the implementation differs: the LaTeX variant of OFS uses NFSS, but the Plain variant implements its own font management (which may even be better than NFSS)
• Support for math fonts including TX fonts.

See also plnfss font-selection fontch.

The author is Petr Olšák.