Iff

Interchange File Format

This article/section is a stub — probably a pile of half-sorted notes and is probably a first version, is not well-checked, so may have incorrect bits. (Feel free to ignore, or tell me)

Interchange File Format (IFF) is a file format that stores chunks, each tagged with what they are.

Originally introduced by Electronic Arts in 1985 (that specification can be referred to as EA IFF 85).

The file is big-endian (native to Macs and Amigas of the time), which is a little extra work on the little-endian x86.

There are various mild variations, a few derivative formats, and a few that formats that just happen to use a very similar chunking scheme just because it is a fairly obvious thing to do if you want to store more than one thing in one file.

Used in/for things like:

• Audio Interchange File Format (AIFF/AIFF-C)
• DjVu
• WebP
• 8SVX ('8-Bit Sampled Voice')
• Real Media File Format (RMFF)

Similar but not directly compatible:

• Microsoft's RIFF

seems to just be little-endian IFF?(verify)

the basis of WAV files (storing PCM sound), ANI (icons), AVI (video), and a bunch more

• MIDI uses a similar setup

Microsoft's .RMI is MIDI wrapped in RIFF - which adds an extra layer of tagging which... is usually more confusing than it is useful

• Nero's NRG images

Note: TIFF is not IFF-based, although it does have a similar approach(verify)

See also:

• http://en.wikipedia.org/wiki/Interchange_File_Format
• http://docs.python.org/lib/module-chunk.html

If and only if

Iff is a shorthand for if and only if, reglarly used in logic, theorems, and predicates elsewhere.

In a predicate-logic sense, 'if', 'only if', and 'if and only if' this is the distinction between

• a ⇒ b

• a ⇐ b

also written as b ⇒ a

• a ⇒ b and a ⇐ b

also written as a ⇔ b

The thing is that refers to strict logic, first-order predicate stuff.

Which means the use of everyday language makes it potentially confusing, because that suggests the more everyday, 'if this then probably that' reasoning.

And it gets even more confusing if we use everyday examples that in the real world would indeed only have that pragatic, probable sense.

(more typing up elsewhere)