Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!rutgers!sri-spam!sri-unix!hplabs!hp-pcd!orstcs!tgd
From: tgd@orstcs.UUCP (tgd)
Newsgroups: net.ai
Subject: Re: The Analog/Digital Distinction: Soli
Message-ID: <45900003@orstcs.UUCP>
Date: Thu, 23-Oct-86 13:20:00 EST
Article-I.D.: orstcs.45900003
Posted: Thu Oct 23 13:20:00 1986
Date-Received: Sun, 26-Oct-86 03:36:08 EST
References: <7@mind.UUCP>
Organization: Oregon State University - Corvallis, OR
Lines: 21
Nf-ID: #R:mind:-700:orstcs:45900003:000:1186
Nf-From: orstcs!tgd    Oct 23 09:20:00 1986

Here is a rough try at defining the analog vs. digital distinction.

In any representation, certain properties of the representational medium are
exploited to carry information.  Digital representations tend to exploit
fewer properties of the medium.  For example, in digital electronics, a 0
could be defined as anything below .2volts and a 1 as anything above 4volts.
This is a simple distinction.  An analog representation of a signal (e.g.,
in an audio amplifier) requires a much finer grain of distinctions--it
exploits the continuity of voltage to represent, for example, the loudness
of a sound.

A related notion of digital and analog can be obtained by considering what
kinds of transformations can be applied without losing information.  Digital
signals can generally be transformed in more ways--precisely because they do
not exploit as many properties of the representational medium.  Hence, if we
add .1volts to a digital 0 as defined above, the result will either still be
0 or else be undefined (and hence detectable).  A digital 1 remains
unchanged under addition of .1volts.  However, the analog signal would be
changed under ANY addition of voltage.

--Tom Dietterich