Oldest operational computer was Re: cctalk Digest, Vol 54, Issue

Tony Duell ard at p850ug1.demon.co.uk
Thu Feb 14 12:47:16 CST 2008

> Hi,
> Not completely on topic, but my boss wishes to build a computer using
> modern knowledge, but only materials, IO etc that existed as at 1st Jan
> 1900.    The basic premise is that had a need existed, and they knew how
> to make one, could have it been done.

I think you need to be more specific. The laws of physics and chemistry 
have, AFAIK, not changed since 1900. The necessary raw materials to make 
transsitors and ICs were around then. So from what you said, you could 
just use a microprocessor.... So I think you have to consider just what 
you are, and are not, allowing with respect to making devices to make 
components, etc.

> That initially seemed hard, and certainly isn't easy, in that I'm the
> one doing the "building" :-)  however we have fairly quickly identified
> that magnetic logic is the only likely candidate.  Currently I'm playing

Relays were certainly well known and understood at that time. I would 
propose a relay logic machine, therefore.

Unfortunately my books on telegraphy are about 10-15 years too late. Some 
of the stuff in there could well be very applicable if it was known at 
the time you want. 

For example, and going a bit off the thread, one of my old books on 
electrical engineering describes a system used on the London Underground 
(underground railway, subway, call it what you will) to keep track of the 
trains. Each train had a 4 bit code, there was a drunm with 4 rows of 
pins whcih could be moved itn oone of 2 states to stoe the IDs of the 
trains. A set of solenoids moved the pins, the drum was then stepped to 
the next positon. A separate rotating set of contacts read out the states 
of a a row of pins and then moved on to the next one. It worked just like 
the classic circular queue with seaprate read and write pointers that 
we've all implemented in software at some point. The outputs of the 
contacts were decoded by a 'tree stucture' of relays to produce a 1-of-16 

Now, as I said, I don;t know if that was around in 1900, but it certainly 
_could_ have been,

The electric light bulb was known before 1900. The Edison Effect (diode 
valve) was, IIRC 1883. THe triode, was, alas, later (1907 I think), but 
maybe you'll stretch the point and allow it.


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