Bidirectional applications use bidirectional text. The bidirectional text is identified by the bidirectional attributes. Since applications use different sets of bidirectional attributes (and thus, different representations of bidirectional text), it is necessary to convert this text among representation forms. The most common case is when an application converts the text from the internal (storage) representation to the external (presentation) form.
OS/2 provides a set of Layout functions to manage the conversion of bidirectional text between different formats. The text is assumed to be in a form/representation that is described by a set of input values and is converted to another form described by a set of output values.