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An ISO image is an archive file (a.k.a. disk image) of an optical disc using a conventional ISO (International Organization for Standardization) format that is supported by many software vendors. ISO image files typically have a file extension of .ISO but Mac OS X ISO images often have the extension .CDR. The name "ISO" is taken from the ISO 9660 file system used with CD-ROM media, but an ISO image can also contain UDF file system because UDF is backward-compatible to ISO 9660.

Format

As with any other archive, an ISO image includes all the data of files contained on the archived CD/DVD. They are stored in an uncompressed format. In addition to data of the files it also contains all the filesystem metadata, including boot code, structures, and attributes. ISO image does not support multi-track, thus cannot be used for audio CDs, VCD, and hybrid audio CDs.

These properties make it an attractive alternative to physical media for the distribution of software as it is simple to transfer over the Internet or via a LAN connection.

ISO image is an unattached file format (like RAR and ZIP): it merges a series of files into one single file according to a definite format. The most important feature of ISO is that it can be burned to DVD/VCD/CD with a special ISO tool, such as ISO burner, ISO Maker and so on.

Typical uses

Some of the common uses include:

• Distribution of software
• Mount "virtual drives" which emulate physical CDs or DVDs, such as Virtual Computers. Better performance is achieved by running an ISO image since hard drive I/O is many times faster than CD/DVD drive I/O.
• To use software titles that are written in such a way that they require a physical disk to be present in order to run. Games are commonly in this category.

See also

Related topics

• Most optical disc authoring software (CD/DVD burning software) can write ISO files to disc.
• See list of ISO image software for a list of software programs that can read and/or write ISO image files.

Related file formats

• BIN/CUE
• BWT, BWI, BWS, BWA
• CCD
• CIF from Adaptec Easy CD Creator
• CDI from DiscJuggler
• CSO (.cso)
• DAA (.daa)
• LCD from CDSpace
• MDF/MDS (.mdf)
• NRG (.nrg)
• DMG (Apple disk image) (.dmg)
• UIF (Universal Image Format) (.uif)
• IMA (.ima)
• IMG (.img)
• .dk (.dk)
• .isc (.ISC) MF Digital's Image Script virtual image file format
• WIM (.wim)

References

• http://www.ecma-international.org/publications/standards/Ecma-119.htm