Modern Electronics (was Re: List charter mods & headcount... ;

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Tue Jun 22 17:44:36 2004

>
>
> On 22 Jun 2004, at 08:53, Tony Duell wrote:
> >
> > There have been discussions over here about teaching maths in schools,
> > in that with the common use of calculators it's not necessary for
> > students to understand things like long multiplications (the fact
> > that's
> > _exactly_ how every calculator I've ever examined does multiplication
> > is
> > another matter, but anyway). To some extent that's true, but then you
> > should teach the correct use of calculators. Why some statements that
> > are
> > mathemetically correct are not suitable for machine calculation. The
> > problem with itterations that converge far too slowly, or are unstable.
> > Things like that.
>
> Well I can think of one programmable calculator that I used in the
> early 1970s
> that did multiplication/division etc using logarithms. This had the neat

Interesting. The only machine I've ever come across that did something
like that weas the I2S (International Imaging Systems) Model 70 Image
processor/display. Those machines have several byteplanes, the outputs of
which feed lookup tables, the outputs of those are added (there's a large
board of full adders in the rack), then to more lookup tables. The manaul
suggests programming log and antilog tables if you want to multiply the
byteplanes.

Has anyone else ever come across these I2S machines?

Perhaps I should have said that all calculators _that I have worked on
and understood the internals of_ (which basically means quite a few HP
models) use a long multiplication algorithm.

-tony
Received on Tue Jun 22 2004 - 17:44:36 BST