Ah, yes, I did write one of those once - a 1980s spelling dictionary for a word processor, where being able to encode an entire word in the smallest possible number of five-bit codes was *much* more important than being able to read the list backwards. (I think we ended up with less than 3 bytes per word for an English dictionary?)

I'm slightly surprised that it's thought to matter with this century's disk prices however.

-- 
Tim Ward

AFAIK it's not about disk price, but to make it more dense, so more index entries could fit in a single page, leading to fewer page reads and so improving speed.

see you !