non-binary computers?

From: Mark Green <>
Date: Thu Sep 2 17:10:37 1999

> I recall reading an article a while back about the possibility of
> building computers based on a number system other than two (octal, IIRC).
> If memory serves me right, it was found possible to do, but not
> practical and less efficient than binary.
> I now have need for some basic information on the possibility of
> non-binary computers, but am unable to find anything. Can anybody point
> me in the direction of some info?

A number of early small computers were non-binary. One that comes
to mind is the IBM 1620 which was a decimal variable word lenght
machine. The 1620 was in production about 40 years ago and was
mainly marketed as a business machine. One of the interesting
features of this machine was that it did all its arthmetic by
table lookup. The tables were stored in memory, so you could change
how the operations worked! A number of 1620s were used by universities
into the late 1960s. Since they were variable word length, they
were very nice for doing precise computations.

Since early computers were based on analogue electronics it was
much easier to do non-binary than it is now. Many early memory
devices (except core) were really analogue devices with thresholds
used to distinguish 0 and 1. You just needed to add a few more
thresholds to get a larger range.

Dr. Mark Green                       
Professor                                      (780) 492-4584
Director, Research Institute for Multimedia Systems (RIMS)
Department of Computing Science                (780) 492-1071 (FAX)
University of Alberta, Edmonton, Alberta, T6G 2H1, Canada
Received on Thu Sep 02 1999 - 17:10:37 BST

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