Definition of an Analog(ue) Computer

From: Allison J Parent <allisonp_at_world.std.com>
Date: Wed May 6 08:57:51 1998

<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

Yes, but they don't (generally) amplify.

<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).

I still hold that amplification is a factor in the equation that an analog
function may contain but it is not required.

    ----||----+---------+------>
              | |
              | |
              V ---
    input === diode ---
              | |
    --------------------+------>

This is an analogue function, take a shot at the equation it solves.

<For non-electronic digital computers, where do Facit mechanical
<calculators lie? I have one (which is driven by an electric motor but

Computers, mechanical, fixed program.

<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.

pipe organs were an example of repetitive but generally simple logic.
I might point ot that when they went electronic they used lots of
flipflops to generate octave and also diodes and tube to do keying
(gating). They were likely one of the earliest users of large numbers
of bistable and monostable elements in one system other than computers and
electronic measuring instruments.

You've not seen a modern production line that uses air logic. I've worked
on one that was used to produce pharaceuticals that were in flamable bases
(ethanol). There was some fairly complex logic in that system. Working
with it is like designing with relays.

Allison
Received on Wed May 06 1998 - 08:57:51 BST