<file format> (IFF, full name "EA IFF 1985") A generic file format published by Electronic Arts as an open standard. IFF is chunk-based and hierarchical so files can include other files. It is easily extensible and an all round Good Idea. An IFF file starts with one of the following "group IDs": 'FORM', 'LIST' or 'CAT '. This is followed by an unsigned 32-bit number of bytes in the remainder of the file. Then comes an ID that indicates which type of IFF file this is. The main image type is ILBM, audio is either AIFF or 8SVX, animations are ANIM etc. An IFF file will probably have a filename extension related to this file type stored in the file. The rest of the file is divided into chunks each of which also has a four-byte header and byte count. Microsoft WAV and AVI are all based around an almost identical scheme to IFF called RIFF. The main difference is that, in RIFF files, numbers are little-endian as on Intel processors, whereas in IFF files they are big-endian, as on the Motorola 68000 processors in the Amiga where IFF files were first used. (1997-07-23)

If and only if. Used in math and logic to state necessary and sufficient conditions for something to occur or exist.
Iff you ask me out, then I will go out with you.

1. <file format> Interchange File Format. 2. Identify friend or foe (radar).