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 would any other archive, 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.
Typical uses
Some of the common uses include:
- Distribution of software
- Mount "virtual drives" which emulate physical CDs or DVDs. Better performance is achieved by running an ISO image since hard drive I/O speed is many times faster than a CD/DVD drive.
- 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
Related file formats
References
^ Descriptor files are not image files, but they are commonly bundled with image files to describe the image's content and properties.
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