UDF

UDF means "Universal Disk Format".

The UDF format is used for so called "packet written" writable CD-ROMs that
are not simply copies of ISO 9660 CDROMs. Packet writing allows CDs to be
partially written using variable or fixed length records in multiple
sessions. Variable length packets written CD-Rs and CD-RWs can (usually) be
closed to ISO 9660 format just by writing a table of contents on the CD.
Fixed length packet formatting can not be closed to ISO 9660 format, but can
be randomly written and overwritten. Fixed length formatting cuts CD
capacity by about 20% relative to ISO 9660 or variable length formatting.

Conventional operating systems only provide support for ISO 9660 format
unless special drivers are loaded. Thus UDF formatted information can not be
used or listened to without closing the file to ISO 9660 format. Once
closed, the CDROM can not be reopened.

More generally, UDF is a format specification of a file system for storing
files on recordable media, mainly media with limited rewriting conditions,
such as:

   * MO (magneto optical)
   * DVD (including DVD-ROM, DVD-R and others)
   * CD-R, CD-RW

It is mainly used for DVD-Video discs, but also by software such as DirectCD
for Windows by Roxio, or Write UDF by Software Architects.

UDF is practically the successor of ISO 9660, supporting larger files,
larger disk and more information about individual files and folders (e.g.,
it includes support for special file properties, such as Apple's File Types,
Resource Forks, and other OS-specific data).