On 31 Jul, wrote:
In article , Jim H
wrote:
Jim Lesurf in uk.rec.audio:

Did some looking through books, etc, today on this...

we now use 'bit' for quantity of info, but this was not always the
case in early work IIRC.

Interesting, what was considered the lowest possible unit of
information?

My memory is unreliable on this as I only came across references to it
many years ago. Note they weren't regarded as the 'lowest unit' any more
than a metre is the 'lowest unit' in the sense of being indivisible.
IIRC one unit was based upon 'e'. I think these units appear in, for
example, some of the books on the work at Bletchly Park during WW2.
Afraid I'd need to find the books and search through them to see what I
could find about this, although I suppose it may also be "out there" on
the web as most things are, these days!

I'm fairly sure this crops up in one of the more technical articles in "The
Inside Story of Bletchly Park" edited by Hinsley and Stripp. However a
look-through today didn't find a reference. It is, however, mentioned in
"Information Theory for Information Technologists" by M. J. Usher.

There it specifies 'nats' as the unit when using base 'e' and 'trits' when
using base 3 as examples. My recollection was that base 'e' was used a fair
bit for early work, but vanished once most processing, computing, etc
became binary digital. Looking through Shannon's early papers he refers to
other unit systems in his initial works on information theory, but refers
back to Hartley in the 1920's and to others for this and I didn't have the
papers to hand.

For work on 'natural' sic languages like English using 'nats' makes as
much sense in theoretical terms as using 'bits'. Similary for 'analog'
signalling and symbol systems. However base 2 makes good sense when most
processing, etc, tends to be done with binary digital methods. It is also
easier to explain in lectures. :-)

Slainte,

Jim

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