Can be mounted like an optical disc (such as a CD or DVD) or a disk drive (like an external hard drive); resides on the hard drive, but is recognized by the computer as a disc or hard disk when mounted.

IMG files, which were used by Mac OS 9 and earlier versions of the Mac OS, were replaced by the newer .DMG disk image format in Mac OS X.

Important: In some cases, renaming the file extension of an IMG file from ".img" to ".iso" will allow other programs to open the file.

Contains data copied from a CD by CloneCD; typically used for making backup copies of discs; should be saved in the same folder as the .CCD and .SUB files, which are referenced when burning a new CD.