A disk image is a single file or storage device containing the complete contents and structure representing a data storage medium or device, such as a hard drive, tape drives, floppy disk, CD/DVD/BD and key drive, although an image of an optical disc may be referred to as an optical disc image. A disk image is usually created by creating a complete sector-by-sector copy of the source medium and thereby perfectly replicating the structure and contents of a storage device.
Some disk imaging utilities omit unused file space from source media, or compress the disk they represent to reduce storage requirements, though these are typically referred to as archive files, as they are not literally disk images.
