May 10, 2006


OUP has just (May 4) published "Colossus : The secrets of Bletchley Park's code-breaking computers", edited by Jack Copeland.

According to the blurb on amazon's site,

The American ENIAC is customarily regarded as having been the starting point of electronic computation. This book rewrites the history of computer science, arguing that in reality Colossus--the giant computer built by the British secret service during World War II--predates ENIAC by two years.

Colossus was built during the Second World War at the Government Code and Cypher School at Bletchley Park. Until very recently, much about the Colossus machine was shrouded in secrecy, largely because the code-breaking algorithms that were employed during World War II remained in use by the British security services until a short time ago. In addition, the United States has recently declassified a considerable volume of wartime documents relating to Colossus. Jack Copeland has brought together memoirs of veterans of Bletchley Park--the top-secret headquarters of Britain's secret service--and others who draw on the wealth of declassified information to illuminate the crucial role Colossus played during World War II. Included here are pieces by the former WRENS who actually worked the machine, the scientist who pioneered the use of vacuum tubes in data processing, and leading authorities
on code-breaking and computer science.

A review by Alan Cane in today's Financial Times (subscription only) explains that

... the full significance of the Colossi in shortening the war is now becoming clear, with the release a few years ago of a 500-page document under the curious title "General Report on Tunny" that had remained highly classified since the war.

Written by three of the Bletchley Park codebreakers, Jack Good, Donald Michie and Geoffrey Timms, the report describes how the 11 Colossi were designed and used. Not to break the Enigma traffic - that was the preserve of Alan Turing's "bombes" - but to attack the German's most secret cipher which the Allies codenamed Tunny. This cipher carried the highest grade of German intelligence. Breaking Tunny was key to the success of the D-Day landings.

The "General Report on Tunny" can be found here. The FT review goes on to say that

Computing history, therefore, has to be rewritten. The credit for creating the first electronic computer has so far rested with ENIAC, an 18,000 thermionic valve monster built by Presper Eckert and John Mauchley at the University of Pennsylvania.

ENIAC, however, ran its first program at the end of 1945, two years after Colossus successfully attacked the Tunny codes.

After the war the Colossi were largely broken up, the documentation destroyed and any mention of Colossus or the part it played in the Allied victory suppressed under the weight of the Official Secrets Act.

The article concludes:

Are there lessons to be learned from Colossus? Only that the UK still lacks the skills to profit from its ability to innovate: and that until it acquires them, it will have to be satisfied with the tacit knowledge that "We did it first."

Well, ENIAC didn't bring Philadelphia any lasting dominance in the digital hardware business, either.

[More information can be found in the Wikipedia article on the Colossus, including some discussion of the code-breaking methods that Colossus was designed to implement. You'll see from that description

The Colossus computers were used to help decipher teleprinter messages which had been encrypted using the Lorenz SZ40/42 machine. Colossus compared two data streams, counting each match based on a programmable boolean function. The encrypted message was read at high speed from a paper tape. The other stream was generated internally, and was an electronic simulation of the Lorenz machine at various trial settings. If the match count for a setting was above a certain threshold, it would be output on an electric typewriter.

that it's not clear that Colossus should be considered to be a "general purpose" computing machine: perhaps ENIAC's laurels are safe.]

[Update: I should have known that I couldn't get away without citing Atanasoff and Zuse.

Linda Seebach wrote:

Eckert-Mauchly don't deserve credit for the first digital computer; John Atanasoff at Iowa State was ahead of them. But he didn't patent it.
[section below quoted from cited URL]
The Atanasoff-Berry Computer was the world's first electronic digital computer. It was built by John Vincent Atanasoff and Clifford Berry at Iowa State University during 1937-42. It incorporated several major innovations in computing including the use of binary arithmetic, regenerative memory, parallel processing, and separation of memory and computing functions. On October 19, 1973, US Federal Judge Earl R. Larson signed his decision following a lengthy court trial which declared the ENIAC patent of Mauchly and Eckert invalid and named Atanasoff the inventor of the electronic digital computer -- the Atanasoff-Berry Computer or the ABC.

Clark Mollenhoff in his book, Atanasoff, Forgotten Father of the Computer, details the design and construction of the Atanasoff-Berry Computer with emphasis on the relationships of the individuals. Alice and Arthur Burks in their book, The First Electronic Computer: The Atanasoff Story, describe the design and construction of the ABC and provide a more technical perspective. Numerous articles provide additional information. In recognition of his achievement, Atanasoff was awarded the National Medal of Technology by President George Bush at the White house on November 13, 1990.

Julia Hockenmeier asked:

I was also wondering, how exactly does Zuse's Z3 compare to the Colossus and the ENIAC?

And Mike Albaugh wrote:

Colossus vs. Enigma: sounds like a WWF match. Anyway, neither machine was as "General Purpose" as Konrad Zuse's Z1, built from scrounged metal bits in the living-room of his parents' apartment, in 1936. Of course, within their domains they were undoubtledly faster, as Z1 was purely mechanical. (Z2 was a later version in electro-mechanical form.)

As a docent at the Computer History Museum, I have learned to very carefully lay out the adjectives when describing a "first". There are a huge number of "first" computers, depending on the precise mix of adjectives.

Further details are available from the Wikipedia articles on Atanaoff and Zuse.

Meanwhile, my copy of Copeland's Colossus book has just arrived, which was the point for me here in the first place.]

Posted by Mark Liberman at May 10, 2006 11:41 AM