[GreenKeys] First Electronic Computer

[Craig Sawyers]

>  My old boss asked me recently what was the generally accepted
> "first electronic computer" and who is credited with building or
> designing
> it.  Anyone know?

Well, until the mid 70's it was generally accepted to be ENIAC (Electronic
Numerical Integrator and Computer)  - a beast which contained 19,000 tubes
and consumed 200kW.  It has a storage capacity of 20 ten-digit decimal
numbers.  It could discriminate the sign of a number, compare quantities for
equality, add, subtract, multiply, divide, and extract square roots. It was
finally commissioned in early 1946.

Lots of history out there about ENIAC - have a look at
http://ftp.arl.mil/~mike/comphist/eniac-story.html and
http://ei.cs.vt.edu/~history/ENIAC.Richey.HTML

However it turned out that a British machine called Colossus predated it by
two years.  Collossus was not a general purpose machine, it was specifically
designed to break the Lorenz cipher.  The Lorenz machine had 10^19 initial
settings, so breaking it by hand was nearly impossible.  However a
statistical weakness was found in the cipher that could be exploited it you
could do enough calculations.  Colossus was designed at the Dollis Hill Post
Office reseach lab in the UK, and incorporated 2000 tubes.  Extemely
innovative, it parallel processed all 5 teleprinted Baudot bits, and until
the 1998 Pentiums it beat modern computers.  In modern jargon Colossus was
really a parallel processing coprocessor.

Anyway, ten Colossi were built, and all of them including the plans were
destroyed after the war on Chruchill's specific orders (so they wouldn't
fall into the hands of the Soviets).  In fact two existed for a while at
GCHQ, until they too were destroyed in the early 60's.  It was only when the
files became public domain after 30 years that it's existence was even known
about.

Astonishingly it has been rebuilt.  The 90-odd year old desiger was found
(Tommy Flowers), and remembered enough to sketch out schematics.  Old tubes
were found, and engineers who had illegally kept drawings in the attick
provided them to the project.

Here's a picture of it originally being used
http://www.pro.gov.uk/virtualmuseum/maingalleries/invent/computer/computer.h
tm.  And this is the website of the guy who rebuilt the machine
http://www.codesandciphers.org.uk/lorenz/colossus.htm.

The mechanical Bombes were even more specialised.  They broke the Enigma
cipher, and really were nothing more than 50-odd Enigma machines in a line,
driven by a motor.  They needed great skill to use, however - a cryptanalyst
would "guess" parts of the message (time and date, for example or a
salutation at the start of a message) and this "crib" was used as a test
phrase.  When the rotors of the Bombe reached a point where there was
agreement with the crib, a bell sounded and the machine would stop.  A human
then checked if it had got it right or not.  So they couldn't be looked on
as computers in any real sense of the word.

Craig