What is an ISO file?

by burniso on July 13, 2007

An ISO image is an archive disk image file of an optical disk, most generally a CD or DVD. What this means is that an image of a CD is an exact replica of that CD compressed (note when I say compressed in this case it doesn’t mean that the size will be smaller) in one file. In fact ISO files contain raw data. When you extract the contents of that image file, you will have the exact files and folders which were on the CD, which was used to create an image from. In addition to data files it also contains all the metadata of the file-system used (like for example: NTFS or FAT 32), including boot code, structures, and attributes. All of this information is contained in a single file. It is not a multi-track image format and thus cannot be used for Audio CDs.

ISO files are typically useful for creating backups and or sharing bulky files with others. There are basically two ways to handle ISO files in order to be able to view or use their contents. The first is simply to burn the ISO image file onto disc (CD/DVD) and then use the CD normally. The other way is to use an application which “fools” the PC into believing that you are mounting the ISO file onto a virtual (non-existent) CD drive.

Some software titles are written in such a way that they require a physical disk to be present in order to run. This is mainly for security purposes, such that a user has to own the CD and this practice can also be used as a measure to not use a lot of hard disk space just for one application. Games are the most common example of software that fall in this category. When you install games, they partially install half the required files on your computer’s hard disk and the rest need the CD to load the audio tracks or some other data that the software needs to be able run. Otherwise the game would not work.

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