ISO image
An ISO image (as prescribed by ISO standard ISO 9660) is a file that represents a one-to-one copy of a specific computer filesystem, most widely used for the compact disc medium (i.e an entire CD or DVD-ROM).
It is for this reason that many Linux, BSD, or other free operating systems are distributed for download using an ISO image—file permissions and other filesystem metadata is not lost in the transfer. Also, it is possible to loopback mount the image under many of these systems to access the individual files. The ISO 9660 is specified as read-only; currently you cannot modify the content when mounting an ISO file. The loopback mount gives you read access only. However, there are special tools that will allow you to modify an ISO file.
One can download an ISO image from the Internet. It is recommended because of a CD's large data capacity that a user wishing to download an ISO image of a CD to use a download manager, which prevents data loss if the download is interrupted due to a disconnection or a crash. Repeated abortive download attempts consume mirror bandwidth.
After downloading, one can burn this image to a CD. If the burned CD includes an operating system that doesn't need to be installed to the hard disk (this is, can be used from the CD), it is called a LiveCD. LiveCDs are bootable. Such an example of these are the Gnoppix, Knoppix and Morphix Linux distributions.
ISO Image Formats
There are many different ISO image formats to choose from. The most common include the .cue/.bin and .iso image formats.
.iso
The .iso format is a single data file containing all the data in the image. It is the most common format used, especially in the distribution of linux operating systems software.
.cue/.bin
The .cue / .bin format developed by Jeff Arnold for CDRWIN can encode CD Image formats in either 2048 or 2324 bytes per sector. The .bin file contains all the raw data of the CD while the .cue file is a datasheet that describes the data stored in the .bin file. The .cue file is in fact a plain text file. A typical .cue file is as follows:
FILE "IMAGE.BIN" BINARY
TRACK 01 MODE1/2352
INDEX 01 00:00:00
The file would be saved as IMAGE.CUE
See also: Disk image, Nero Burning ROM
