order. When each subtable is encountered, the layout engine compares flags in the subtable against control flags, generally derived from user settings. This determines whether or not the subtable is processed.

The set of available features in the font is made accessible to the user via the "feat" table. This table provides pointers to the localizable strings that can be used to describe a feature to the end user and the appropriate flags to send to the text engine if the feature is selected. Features can be made invisible to the user