Image Exchange Format
Image Exchange Format is a subformat of TIFF, intended to be used for the transmission of bi-level images, especially fax images, over the (early) internet. Image Exchange Format is obsolete as a standard, though the format it defines is still a valid TIFF format.
It is defined in RFC 1314 as a subformat of TIFF Class B (which it calls TIFF-B). TIFF Class B is the bi-level TIFF subformat defined in the TIFF 5.0 specification.
It is not to be confused with Exchangeable image file format (Exif).