File Extension ISO
File extension ISO is most commonly associated with a disc image stored in the ISO-9660 (International Organization for Standardization) file system, which is usually used to store data on CD-ROM. Disc images may also be stored using the UDF file system, which is backwards compatible with ISO-9660. ISO files contain exact disc images of optical media, and are often used for backup purposes or to create duplicates of original media.
ISO files may also be referred to as archives, as they store all the information present on the original CD or DVD. This includes the file and folder structure as well as the original file system and any boot data or attributes. ISO files are uncompressed which results in large file sizes. However, the benefit of this is that no additional processing power is required to extract data from an ISO image, and that the ISO file itself can be mounted using a virtual drive and used by an operating system as though it were a physical disc.
ISO files are commonly used to store backup copies of optical media and for the distribution of CD and DVD-based media over the Internet, as they allow an exact disc image to be made and transferred as a single file which also retains any additional disc attributes which would be lost be conventional zipping of a disc's contents. ISO files are also sometimes created and used with virtual drives to bypass the need for the physical disc to be in the drive to run a given application or game.
ISO files make use of the ISO-9660 and UDF standards and as such are cross-platform compatible. ISO files can be mounted and read using software such as DAEMON Tools or Alcohol 120% which create virtual drives, or opened using an application such as ISOBuster or PowerISO. Most burning software such as Nero or Roxio allows ISO files to be burnt directly to CD or DVD, or alternatively converted into another image format.