tgd@orstcs.UUCP (tgd) (10/23/86)
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