DMG - Computer Definition
(Disk iMaGe) The file format used in the Mac for distributing software. Mac install packages appear as a virtual disk drive on the Mac. When the DMG file icon is double clicked, the virtual drive is "mounted" on the desktop. The DMG format harks back to the days when the Mac was a floppy-only machine. DMGs were used to make multiple floppy disks without having to insert the original floppy again for each subsequent copy. See disk image.