There are no 17 bit, or even 24 bit, options.
externally.
internally, an application could take whatever advantage of compresion it
chooses to, most of the time a 16 bit character size would be ample, and will
probably map to existing conventions on some platforms (ie, 16-bit registers,
buses, support code expectations).
But since my complaints were framed with external, public formats in mind, I
guess I should have clarified that, so I must apoligize again for forgetting to
do so.
--
dana s emery <de19(_at_)umail(_dot_)umd(_dot_)edu>