Computer in 1900

[Philip Belben]

This is an interesting topic.  Without quoting anyone else's messages, 
but acknowledging that I am drawing on other people's ideas, here are 
some suggestions.

Memory.  I'd go for mechanical.  Either decimal (there were mechanical 
calculators around at that date that had decimal and even duodecimal 
wheels for registers) or binary.  I think the first binary mechanical 
memory was built by Konrad Zuse in the 1930s.  They've reconstructed it, 
along with the rest of the Z1, at the Technical Museum in Berlin.  It 
could easily have been done using Victorian precision engineering

Logic.  I'd still go for relays.  I don't know whether there were relays 
as such in 1900 - my electrical engineering textbook of 1892 doesn't 
mention them - but the coils, cores, and components to make switches and 
actuators were all available.

On the other hand, there's a lovely _programmable_ mechanical 
calculator, from about 2 years before Zuse, preserved at the IBM museum 
in Sindelfingen.  This was just like any mechanical calculator of the 
day (decimal wheel registers), but with several accumulators.  You could 
program nine steps of something resembling horizontal microcode on a 
plugboard somewhere; it then sucked in hundreds of punched cards and 
processed each according to the nine steps.  There were conditionals in 
there - "if the card has a hole in position foo then add the total from 
accumulator 1 into accumulator 3" was I believe a possible instruction.

This machine was made by Dehomag - the German Hollerith Machine Company 
- who were later bought out by IBM.  Very fitting, since this machine 
was a typical IBM box - horrible processor but data throughput to die for...

And despite the 1934 date, I expect it could have been built in a 1900 
precision machine shop.

Philip.