The IL and FL man pages contain documentation for each of the functions that can be called from a plug-in to manipulate IFF files. See the IFFmanPages for details.
The fcheck program provided with Maya allows you to view IFF files directly. See Overview of FCheck for details.
imgcvt man page (Linux and Windows only)
The imgcvt program provided with Maya allows you to convert IFF files to other formats. See imgcvt for details.
