IFF, the "Interchange File Format" standard, encourages multimedia
interchange between different programs and different computers.  It
supports long-lived, extensible data.  It's great for composite files like
a page layout file that includes photos, an animation file that includes
music, and a library of sound effects.

IFF is a 2-level standard.  The first layer is the "wrapper" or "envelope"
structure for all IFF files.  Technically, it's the syntax.  The second
layer defines particular IFF file types such as ILBM (standard raster
pictures), ANIM (animation), SMUS (simple musical score), and 8SVX (8-bit
sampled audio voice).

IFF is also a design idea: programs should use interchange formats for
their everyday storage.

This way, users rarely need converters and import/export commands to
change software releases, application programs, or hardware.