Interchange File Format (IFF) is a generic digital container file format originally introduced by Electronic Arts (in cooperation with Commodore) in 1985 to facilitate transfer of data between software produced by different companies.
There are predefined group chunks, with type IDs FORM, LIST and CAT .
Group chunks, like their simpler counterparts, contain a length element.
It is also possible to include other IFF files as if they are chunks (note that they have the same structure: four letters followed with length), and some formats use this.
Some programs that create IFF files add chunks to them with their internal data; these same files can later be read by other programs without any disruption (because their parsers could skip uninteresting chunks), which is a great advantage of IFF and similar formats.