The main function of any file system is to keep track of where all the data files are located on the storage medium. Standard CD-ROM's are commonly formatted using a file system called ISO 9660. Other file formats in use are HFS (Hierarchical File System) and Joliet File System. The newest innovation in file systems is UDF (Universal Disk Format) which uses packet-writing technology. (None of the file systems mentioned earlier---ISO 9660, HFS, and Joliet---use packet-writing technology.) Although you may never have heard of packet writing or understand the technical details of it, you are seeing the impact of this technology in the recent availability of affordable CD-Writers to the general public. Packet-writing technology provides the ability to write small amounts of data incrementally to a CD without requiring large amounts of overhead space. Previously, the CD recording process always required huge amounts of overhead space, as well as time.
ISO 9660 File System
Standard CD-ROM's are commonly formatted using the ISO 9660 file system. ISO 9660 is an international standard that specifies how data is arranged in its logical format on a CD-ROM. This includes standards for the format of file names and directory names. Computers running under various operating systems such as DOS, Macintosh, OS/2, Windows, and UNIX can all read CD's written in the ISO 9660 format. The problem with the ISO 9660 is it doesn't support long file names.
ISO 9660 does not use packet-writing technology.
HFS (Hierarchical File System)
The Hierarchical File System refers to the MAC format.
The Joliet File System is very similar to ISO 9660 except it supports longer file names. Almost all CD readers can read the Joliet format now. This is the format that we most often recommend for your recovered files.
Newer technologies, such as CD-RW, DVD-ROM, and DVD-Video are formatted using a file system called UDF. UDF stands for Universal Disk Format. It a new standard that specifies how data is arranged on a CD or DVD, and specifies how the data can be accessed. UDF has been endorsed by the Optical Storage Technology Association (OSTA). The newer technologies (CD-RW, DVD-ROM, and DVD-Video) need a file system that can handle updates and changes to the disc. ISO 9660 has a number of limitations that make it unsuitable for this. UDF does not have these limitations. It uses a new technology called packet writing that allows the directory and file structure on disc to be updated when small increments of data, called packets, are added to the disc. What this means in a practical sense is that single files may be added to a CD-R or CD-RW. Files may also be modified one at time. UDF also allows for the erasure of individual files on a CD-R or CD-RW. This development has opened the way for CD-Writers to become a low-cost storage solution for desktop computers.
Video CD format discs are commonly played on DVD players. The format is also know as MPEG1.
CD+G stands for Compact Disc + Graphics.
This compact disc format is rarely used. It's generally used if both audio and low
resolution graphics are needed on the same CD.
CD TEXT Format is a format that allows text information to be displayed while music is being played, such as the artist's name, track number, messages, etc.