Definition of an Analog(ue) Computer

From: Philip.Belben_at_powertech.co.uk <(Philip.Belben_at_powertech.co.uk)>
Date: Wed May 6 08:15:52 1998

> <Are you thinking of 'Digital circuits are built from analogue parts' ?
>
> Not a valid concept. both OR and AND gates can be done using totally
> non amplifying devices (diodes).

What's that got to do with it? Diodes are analogue parts - the output
(current) is a continuous function of the input (voltage), not a
discrete one (to me the difference between an analogue and a digital
component). In fact, Allison, you were saying only a few days ago that
you don't need any amplification to make an analogue _computer_ (with
which I agree - although some of your examples I wouldn't call
computers).

> It was Vonda that postulated that digital was analogue with a precision
> of two states, true and false. The realm of analogue is one of infinite
> precision but possibly of limited accuracy. The digital realm is one of
> limited precision and absolute accuracy.

That is an excellent concept. Thank you - I'll remember that.

For non-electronic digital computers, where do Facit mechanical
calculators lie? I have one (which is driven by an electric motor but
could conceivably use any motor) which has algorithms for optimised
decimal multiplication and non-restoring decimal division. It is not
programmable, but it is pretty complex - and all done mechanically.

For pneumatic computers, I think some pipe organs of the turn of the
century came close - you could program some buttons to set various
combinations of ranks for fast selection during performance. However,
the more complicated schemes of this nature (popular around 1920) used
electrical as well as pneumatic logic elements.

Philip.
Received on Wed May 06 1998 - 08:15:52 BST