Crossroads - Spring 2012

The CAPTCHA test used extensively on websites these days is a reversed form of the Turing test used to test a computer for artificial intelligence.

“Captain Ridley’s Shooting
Party”: The guise that
codebreakers, including
Alan Turing, went to work
under in Bletchley Park at the
beginning of W WII.
Photo courtesy of Flickr user
pingsandneedles, Sarah Witherby

mechanical machine that could find settings for the Enigma machine.

Turing was thought to be a bit ec-
centric at Bletchley Park. In Ronald
Lewin’s Ultra Goes to War: The Secret
Story Jack Good, a cryptanalyst who
worked with Turing, had this to say
about the “Father of Computer Sci-
ence”:
“In the first week of June each year
he would get a bad attack of hay fever,
and he would cycle to the office wear-
ing a service gas mask to keep the pol-
len off. His bicycle had a fault—the
chain would come off at regular inter-
vals. Instead of having it mended he
would count the number of times the
pedals went round and would get off
the bicycle in time to adjust the chain
by hand. Another of his eccentricities
is that he chained his mug to the radia-
tor pipes to prevent it being stolen.”
On June 19, 2007 a 1.5-ton, life-
size statue of Turing was unveiled at
Bletchley Park. The statue is built from
approximately half a million pieces of
Welsh slate and was sculpted by Ste-
phen Kettle.

VISI TING THE SI TE

In case you find yourself visiting London, Bletchley Park is just a 40-50 minutes train ride from central railway stations—a great half-day trip for you and your friends. You will have the opportunity to see their Enigma collection, a reconstruction of the Bombe machine, an authentic rebuild of Colossus, the world’s first semi-programmable computer, and visit the National Museum of Computing. The park often hosts a big number of computing-oriented events throughout the year. Don’t forget to have a coffee at the Hut 4, the code-breaking hut that housed the wartime Naval Intelligence Section where decrypted Enigma messages were translated and forwarded to the Admiralty during the war.

Turing’s Bombe

We’ve seen in this issue the tremendous impact that Alan Turing had on defining the field of the computer science. One of his most notable contributions is the design of the Bombe, an electromechanical device used by British cryptologists to help decipher German Enigma machine-encrypted signals during W WII. A fully rebuilt and working Bombe now resides in Bletchley Park in Milton Keynes, England. How does it compare with computers of today?—James Stanier

Year introduced Manufacturer Dimensions Weight Interface Common usages

BOMBE

1941

British Tabulating Machine Company Height: 6 feet 6 inches, Width: 7 feet, Depth: 2 feet About a ton Rotating drums Cracking encoded messages from German Enigma machines