Interchange File Format

Type Bitmap Colors 1- to 24-bit Compression RLE, uncompressed Maximum Image Size 64Kx64K pixels Multiple Images Per File Yes Numerical Format Big-endian Originator Electronic Arts, Inc., Commodore-Amiga, Inc. Platform Amiga, MS-DOS, others Supporting Applications Too numerous to list See Also Microsoft RIFF , GIF , PNG Usage On platforms other than the Amiga, IFF is used mostly for storing image and sound data. On the Amiga almost any type of data may be found in an IFF file. The file extension usually indicates the type of data stored in an IFF file. Comment IFF is an older data file format found on most every system. Its versatility has not been greatly utilized outside of the Amiga platform. IFF (Interchange File Format) is a general purpose data storage format that can associate and store multiple types of data. IFF is portable and has many well-defined extensions that support still-picture, sound, music, video, and textual data. Because of this extensibility, IFF has fathered a family of special purpose file formats all based on IFF's simple data structure. IFF is most often associated with the Commodore-Amiga computer and originated on that system. IFF is fully supported by the Amiga operating system and is used for storing virtually every type of data found in the Amiga's filesystem. Initialization files, documents, temporary data, and data exported from the clipboard may all be stored using the IFF format. The most common IFF family member is ILBM, or InterLeaved BitMap. ILBM files are the standard image file format for the Commodore-Amiga computer and are the type of IFF files with which most graphics people are familiar. IFF files are common in the MS-DOS and UNIX environment as well and usually have the file extension .IFF or .LBM. Electronic Arts' DeluxePaint program is generally credited with making IFF known to the MS-DOS community. For a time IFF was a widely accepted 24-bit format under MS-DOS, but it was eventually replaced first by TIFF and TGA, and then by JFIF. IFF faces compatibility problems when the occasional program fails to write IFF file data using the big-endian byte order. This prevents most programs from reading these IFF files. Other problems created by bad IFF file writers include writing planar image data improperly and failing to use only linefeeds to terminate lines of text. Unfortuantely, some people (those who are all too willing to shoot the messenger), have blamed IFF, rather than bad software, for these problems. Today IFF is a widely used format that is supported by most graphics programs found on MS-DOS, MS Windows, Macintosh, UNIX, and Amiga systems. The format basically remained unchanged since its specification was released in 1985, but many extensions to the format have been created and documented by a great many software developers, making IFF one of the most utilized data file formats of today. IFF nesting is a powerful organizing principle. It offers the same sort of organizational advantages that nested directories and subdirectories do for filesystems. The down side of nesting is that it introduces a certain amount of complexity that can make IFF appear difficult to interpret. Most IFF files contain a single chunk called a FORM chunk. This chunk stores the formatting and identification information for all chunks and data in the IFF file. All other chunks in the file are stored within the FORM chunk. The basic structure of the FORM chunk is illustrated in Figure IFF-2. In this example, the FORM chunk is of type ILBM (InterLeaved BitMap) and contains three chunks, each of which contain data blocks that together define an image. The FORM ILBM is the most common file type for storing still-picture graphical data in an IFF file. "ILBM" is the type identifier for the FORM. It tells readers what kind of FORM chunk this is and what chunks might be expected within it. The three chunks in this example are the BMHD (BitMap HeaDer), CMAP (Color MAP), and BODY (the actual pixels