Compressed container file created in the Compact File Set (CFS) format, an open format developed by Pismo Technic; stores data using a reduced implementation of the .ISO disc image standard; used for storing CD and DVD disc images, as well as for creating software distributions and large compressed file archives.

CFS files were designed to be easier to read than ISO files, which can be difficult to read due to the large range of supported storage options in the ISO specification. Since CFS files are compatible with the ISO file standard, they can be read by many existing ISO applications. NOTE: The CFS format is based on the following standards: ISO-9660, Joliet Extensions, ISO-9660:1999, Compact ISO.

File used by Lucene, a text search engine library written in Java; used for saving multiple index files into a single compound archive; enables easier management of the index but may perform slightly slower.

NOTE: Beginning with version 1.4, Lucene uses CFS files by default.