This article is from the Apple ][ Emulator Resources Guide, by Alex Maddison with numerous contributions by others.
The disk-image concept is used for a variety of tasks beyond emulation. Mainly, they are used for software distribution since, unlike compressed archives, disk- images can retain additional information such as file allocation (FAT files on PC disks) and icon placement (on Macintosh disks). Disks duplicated from an image are identical to the original, not mere copies. The following types of distribution images are not directly intended for emulation purposes.
 
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