BALL supports a number of different file formats and offers a set of classes do read and write those formats. Some of these classes provide interfaces for the format classes, e.g. GenericMolFile , which implements a generic interface for molecular file formats. Others implement specific formats. In addition, classes like LineBasedFile provide simple interface to allow the user the rapid implementation of user-defined file formats or for parsing specialized formats. All file format classes are derived from File and provide the features implemented there, e.g. on-the-fly transformation and URL retrieval.