Dual format is a technique used to allow software for two systems which would normally require different disk formats to be recorded on the same floppy disk. In the late 1980s, the term was used to refer to disks that could be used to boot either an Amiga or Atari ST computer. The layout of the first track of the disk was specially laid out to contain an Amiga and an Atari ST boot sector at the same time by fooling the operating system to think that the track resolved into the format it expected. The technique was used for some commercially available games, and also for the disks covermounted on ST/Amiga Format magazine. Other games came on Amiga and PC dual-format disks, or even "tri-format" disks, which contained the Amiga, Atari ST and PC versions of the game. Most dual and tri-format disks were implemented using technology developed by Rob Northen Computing. Later, the term was used for disks containing both Windows and Macintosh versions.

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