Colossus computer: Difference between revisions

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{{distinguish2|the fictional computer of the same name in the movie [[Colossus: The Forbin Project]]}}
Hello! <br>I'm Portuguese male ;=). <br>I really love Shortwave listening!
 
{{Infobox information appliance
| name        = Colossus computer
| image        = [[File:Colossus.jpg|375px]]
| caption      = A Colossus Mark 2 computer being operated by [[Dorothy Du Boisson]] (left) and [[Elsie Booker]]. The slanted control panel on the left was used to set the "pin" (or "cam") patterns of the Lorenz. The "bedstead" paper tape transport is on the right.
| developer    = [[Tommy Flowers]]
| manufacturer = [[Post Office Research Station]]
| type        = Special-purpose electronic digital programmable computer
| generation  = [[First-generation computer]]
| releasedate  = Mk 1: {{Start date|1943|12|df=y}}; <br/> Mk 2: {{Start date|1944|06|01|df=y}}
| discontinued = {{End date|1945|06|08|df=y}}
| unitsshipped = 10
| media        = [[Punched tape|Paper tape]], [[teleprinter]] output
| power        =
| cpu          = Custom circuits using [[Vacuum tube|valves]] and [[Thyratron]]s. A total of 1600 in Mk 1 and 2400 in Mk 2. Also [[relay]]s and [[stepping switch]]es
| storage      = ≤ 20 000 × 5-bit characters in paper tape loop
| memory      = None (no [[Random-access memory|RAM]])
| display      = Indicator lamp panel
| input        = console switches, plug panels and photocells reading paper tape
| dimensions  =
| weight      =
}}
 
'''Colossus''' was the world's first [[electronics|electronic]] [[Digital electronics|digital]] [[computer]] that was at all [[Computer programming|programmable]]. The Colossus computers were developed for British [[cryptanalysis|codebreakers]] during [[World War II]] to help in the [[cryptanalysis of the Lorenz cipher]]. Without them, the [[Allies of World War II|Allies]] would have been deprived of the very valuable [[military intelligence]] that was obtained from reading the vast quantity of [[Encryption|encrypted]] high-level [[Telegraphy|telegraphic]] messages between the [[Oberkommando der Wehrmacht|German High Command (OKW)]] and their [[Wehrmacht|army]] commands throughout occupied Europe. Colossus used [[vacuum tube|thermionic valves (vacuum tubes)]] to perform [[Boolean algebra (logic)|Boolean operations]] and calculations.
 
Colossus was designed by the engineer [[Tommy Flowers]] to solve a problem posed by mathematician [[Max Newman]] at the [[Government Communications Headquarters#Government Code and Cypher School (GC&CS)|Government Code and Cypher School (GC&CS)]] at [[Bletchley Park]]. [[Alan Turing|Alan Turing's]] use of probability in cryptanalysis<ref>See [[Banburismus]]</ref> contributed to its design. It has sometimes been erroneously stated that Turing designed Colossus to aid the [[Cryptanalysis of the Enigma]].<ref>{{Citation | last = Golden | first = Frederic | title = Who Built The First Computer? | journal = Time Magazine | volume = 153 | issue = 12 | date = 29 March 1999 |url=http://www.time.com/time/magazine/article/0,9171,990596,00.html}}</ref> Turing's machine that helped solve [[Enigma machine|Enigma]], was the electromechanical [[Bombe]], not Colossus.<ref>{{Citation | last = Copeland | first = Jack | author-link = Jack Copeland | title = Colossus: The first large scale electronic computer | url = http://www.colossus-computer.com/colossus1.html#sdfootnote96sym | accessdate = 21 October 2012}}</ref>
 
The prototype, '''Colossus Mark 1''', was shown to be working in December 1943 and was operational at Bletchley Park by 5 February 1944.<ref name="Copeland06P75">{{Harvnb|Copeland|2006|p=75}}</ref> An improved '''Colossus Mark 2''' that used [[shift register]]s to quintuple the speed,<ref name="Flowers1983"/> first worked on 1 June 1944,<ref>{{Harvnb|Copeland|2006|p=427}}</ref> just in time for the [[Normandy Landings]]. Ten Colossi were in use by the end of the war.
 
The destruction of most of the Colossus hardware and blueprints, as part of the effort to maintain a project secrecy that was kept up into the 1970s, deprived most of those involved with Colossus of credit for their pioneering advancements in electronic digital computing during their lifetimes. A functioning replica of a Colossus computer was completed in 2007, and is on display at the [[The National Museum of Computing]] at Bletchley Park.<ref>{{Citation | title = The National Museum of Computing: The Colossus Gallery | url = http://www.tnmoc.org/explore/colossus-gallery | accessdate = 18 October 2012 }}</ref>
 
==Purpose and origins==
[[File:SZ42-6-wheels-lightened.jpg|right|340px|thumbnail|The Lorenz SZ machines had 12 wheels each with a different number of cams (or "pins").
{|class="wikitable" | border=1 | style="margin: 1em auto 1em auto"
|-
! Wheel number
|1||2||3||4||5||6||7||8||9||10||11||12
|-
! BP wheel name<ref name = "GRoT11B6">{{Harvnb|Good|Michie|Timms|1945|p=6}} in ''1. Introduction: German Tunny''</ref>
| style="text-align:center;"| <math>\psi</math><sub>1</sub>
| style="text-align:center;"| <math>\psi</math><sub>2</sub>
| style="text-align:center;"| <math>\psi</math><sub>3</sub>
| style="text-align:center;"| <math>\psi</math><sub>4</sub>
| style="text-align:center;"| <math>\psi</math><sub>5</sub>
| style="text-align:center;"| <math>\mu</math>37
| style="text-align:center;"| <math>\mu</math>61
| style="text-align:center;"| <math>\chi</math><sub>1</sub>
| style="text-align:center;"| <math>\chi</math><sub>2</sub>
| style="text-align:center;"| <math>\chi</math><sub>3</sub>
| style="text-align:center;"| <math>\chi</math><sub>4</sub>
| style="text-align:center;"| <math>\chi</math><sub>5</sub>
|-
! Number of cams (pins)
|43||47||51||53||59||37||61||41||31||29||26||23
|}
]]
 
The Colossus computers were used to help decrypt radio [[teleprinter]] messages that had been [[encryption|encrypted]] using the [[electromechanical]] [[Lorenz SZ40/42]] in-line cipher machine. To encipher a message with the Lorenz machine, the [[Baudot code|5-bit]] [[plaintext]] characters were combined with a stream of [[Key (cryptography)|key]] [[ciphertext]] characters using the [[XOR]] [[Boolean function]]. This is a [[Vernam cipher]] and the deciphering process involved an identically setup Lorenz SZ machine generating the same key sequence and XOR-ing it with the received ciphertext to reproduce the plaintext. The [[keystream]] was generated using twelve [[pinwheel (cryptography)|pinwheel]]s.
 
British codebreakers referred to encrypted German teleprinter traffic as "[[Fish (cryptography)|Fish]]" and called the SZ40/42 machine and the intercepted messages "[[Lorenz cipher|Tunny]]". Colossus was used for finding possible Lorenz key settings – not completely decrypting the message. It compared two character streams, counting a statistic based on a programmable Boolean function. The [[ciphertext]] was read at high speed from a paper tape. The other stream was generated internally, and was an electronic simulation of part of the Lorenz machine. If the count for a setting was above a certain threshold, it would be sent as output to an electric typewriter.
 
The logical structure of the Lorenz machine was [[Cryptanalysis of the Lorenz cipher#Diagnosis|diagnosed]] at Bletchley Park without a machine being seen–something that did not happen until almost the end of the war.<ref>{{Citation | last = Sale | first = Tony | author-link = Anthony Sale | title = The Lorenz Cipher and how Bletchley Park broke it | url = http://www.codesandciphers.org.uk/lorenz/fish.htm | accessdate = 21 October 2010 }}</ref> First, [[John Tiltman]], a very talented GC&CS cryptanalyst derived a key stream of almost 4000 characters from a German operating blunder in August 1941. Then [[Bill Tutte]], a newly arrived member of the Research Section used this key stream to work out the logical structure of the Lorenz machine. He correctly deduced that it had twelve wheels in two groups of five, which he named the χ (''[[chi (letter)|chi]]'') and ψ (''[[psi (letter)|psi]]'') wheels, and the remaining two the μ ''[[Mu (letter)|mu]]'' or "motor" wheels. The ''chi'' wheels stepped regularly with each letter that was encrypted, while the ''psi'' wheels stepped irregularly, under the control of the motor wheels.<ref>{{Harvnb|Tutte|2006|p=357}}</ref>
 
In order to decrypt the ciphertext of the transmitted messages, there were two tasks that had to be performed. The first was "wheel breaking", which was the discovery of the pin patterns for all the wheels. These patterns were set up once on the Lorenz machine and then used for a fixed period of time and for a number of different messages. The second task was [[Cryptanalysis of the Lorenz cipher#Steps in Wheel Setting|"wheel setting"]], which could be attempted once the pin patterns were known.<ref>{{Harvnb|Good|Michie|Timms|1945|p=15}} in ''1. Introduction: German Tunny''</ref> Each message encrypted using Lorenz was enciphered at a different start position for the wheels, and it was this start position of the ''chi'' wheels that Colossus was initially designed to discover.
 
The XOR function used in the Vernam cipher for both enciphering and deciphering, could also be used to upset the cipher's obscuring of the characteristics of the plaintext in the ciphertext. This was discovered by Alan Turing in July 1942 when he was on loan from the German Naval Enigma section to the Research Section at Bletchley Park. He was studying Tunny and invented a method of wheel-breaking that became known as [[Turingery]].<ref>{{Harvnb|Copeland|2006|pp=378–385}}</ref> With a truly random key, the Vernam cipher removes the natural language property of a plaintext message of having an uneven [[frequency distribution]] of the different characters, to produce a uniform distribution in the ciphertext. Turing worked out that if, instead of examining the frequency distribution of the characters in the ciphertext, examining the character-to-character changes of character streams showed a departure from uniformity which provided a way into the system. Providing the character-to-character changes was achieved by [[Cryptanalysis of the Lorenz cipher#Differencing|"differencing"]] in which each bit or character was XOR-ed with its successor.
 
By using differencing and knowing that the ''psi'' wheels did not advance with each character, Tutte worked out that trying just two differenced bits (impulses) of the ''chi''-stream against the differenced ciphertext would produce a statistic that was non-random. This became known as [[Cryptanalysis of the Lorenz cipher#Tutte's "1+2 break in"|Tutte's "1+2 break in"]].<ref>{{Harvnb|Budiansky|2006|pp=58–59}}</ref> The process of wheel setting found the start position of the key wheels in relation to the start of the message. Initially Colossus was used only to work out the start positions of the ''chi'' wheels, but later, methods were devised for the other wheels. Later still an additional electronic unit was designed for wheel breaking, which was added to some Mark 2 Colossi.
 
The manual processes in decrypting messages were undertaken in a section at Bletchley Park led by Major [[Ralph Tester]] which was known as the [[Testery|"Testery"]]. Colossus was developed for the "[[Newmanry]]",<ref>{{Harvnb|Good|Michie|Timms|1945|p=276}} in ''3. Organisation: Mr Newman's section''</ref> the section headed by the mathematician [[Max Newman]] at Bletchley Park responsible for machine methods against the Lorenz machine. The Colossus design arose out of a prior project that produced a counting machine dubbed "[[Heath Robinson (codebreaking machine)|Heath Robinson]]". The main problems with the Heath Robinson were the relative slowness of electro-mechanical parts and the difficulty of synchronising two [[punched tape|paper tapes]], one punched with the enciphered message, the other representing the patterns produced by the wheels of the Lorenz machine. The tapes tended to stretch when being read, at some 2000 characters per second, resulting in unreliable counts.
 
==Design and construction==
[[File:ColossusRebuild 11.jpg|right|thumbnail|320px|In 1994, a team led by [[Anthony Sale|Tony Sale]] (right) began a reconstruction of a Colossus at Bletchley Park. Here, in 2006, Sale supervises the breaking of an enciphered message with the completed machine.]]
 
[[Tommy Flowers]] was a senior electrical engineer at the [[Post Office Research Station]] at [[Dollis Hill]] who had been appointed [[Order of the British Empire|MBE]] in June 1943. Prior to his work on Colossus, he had been involved with GC&CS at Bletchley Park from February 1941 in an attempt to improve the [[Bombe]]s that were used in the [[Cryptanalysis of the Enigma|Cryptanalysis of the German Enigma]] cipher machine.<ref>{{Harvnb|Randell|1980|p=9}}</ref> He was recommended to Max Newman by Alan Turing who had been impressed by his work on the Bombes.<ref>{{Harvnb|Budiansky|2000|p=314}}</ref> The main components of Colossus's predecessor, Heath Robinson were: a tape transport and reading mechanism that ran the looped key and message tapes at between 1000 and 2000 characters per second, a combining unit that implemented the logic of [[Cryptanalysis of the Lorenz cipher#Tutte's "1+2 break in"|Tutte's method]], and a counting unit that had been designed by [[C. E. Wynn-Williams|Dr C.E. Wynn-Williams]] of the [[Telecommunications Research Establishment]] (TRE) at Malvern which counted the number of times the logical function returned a specified [[truth value]].
 
[[File:COLOSSUS, part of the machine, presented by Director GCHQ to Director NSA in 1986 - National Cryptologic Museum - DSC07890.JPG|left|thumbnail|250px|[[Stepping switch]] from an original Colossus presented by the Director of [[Government Communications Headquarters|GCHQ]] to the Director of the  [[National Security Agency|NSA]] to mark the 40th anniversary of the [[UKUSA Agreement]] in 1986<ref>Exhibit in the National Cryptologic Museum, Fort Meade, Maryland, USA</ref>]]
Flowers had been brought in to design the Heath Robinson's combining unit.<ref>{{Harvnb|Good|Michie|Timms|1945|p=33}} in ''1. Introduction: Some historical notes''</ref> He was not impressed by the system of a key tape that had to be kept synchronised with the message tape and, on his own initiative, he designed an electronic machine which eliminated the need for the key tape by having an electronic analogue of the Lorenz (Tunny) machine.<ref name="FlowersCopelandP96">{{Harvnb|Flowers|p=96}}</ref> He presented this design to Max Newman in February 1943, but the idea that the one to two thousand thermionic valves ([[vacuum tube]]s and [[thyratron]]s) proposed, could work together reliably, was greeted with great scepticism,<ref name="Flowers1983">{{Harvnb|Flowers|1983}}</ref> so more Robinsons were ordered from Dollis Hill. Flowers, however, knew from his pre-war work that most thermionic valve failures occurred as a result of the thermal stresses at power up, so not powering a machine down reduced failure rates very substantially.<ref>{{Harvnb|Copeland|2006|p=72}}</ref> Flowers persisted with the idea and obtained support from the Director of the Research Station, W Gordon Radley.<ref>{{Harvnb|Randell|2006}}</ref> Flowers and his team of some 50 people in the switching group,<ref name="FlowersCopelandP80">{{Harvnb|Flowers|2006|p=80}}</ref><ref>{{Harvnb|Randell|2006|P-143}}</ref> spent eleven months from early February 1943 designing and building a machine that dispensed with the second tape of the Heath Robinson, by generating the wheel patterns electronically.
 
This prototype, Mark 1 Colossus performed satisfactorily at Dollis Hill on 8 December 1943,<ref>{{Harvnb|Copeland|2010}}</ref> and was taken apart and shipped to Bletchley Park, where it was delivered on 18 January and re-assembled by Harry Fensom and Don Horwood.<ref name="The Colossus Computer">The Colossus Rebuild http://www.tnmoc.org/colossus-rebuild-story</ref><ref>{{Harvnb|Fensom|2010}}</ref> It attacked its first message on 5 February 1944.<ref name="Copeland06P75"/> As it was a large structure it was quickly dubbed Colossus by the WRNS operators. This machine contained 1600 thermionic valves (tubes).<ref name=FlowersCopelandP80/> and was soon followed by an improved production Mark 2 machine.<ref>{{Harvnb|Good|Michie|Timms|1945|p=35}}</ref> Nine of this version of the machine were constructed, the first being commissioned on 1 June 1944, after which [[Allen Coombs]] took over leadership of Colossus production.<ref>{{Citation | last = Randell | first = Brian | author-link = Brian | last2 =Fensom | first2 =Harry | last3 = Milne | first3 =Frank A. | title = Obituary: Allen Coombs | newspaper = The Independent | date = 15 March 1995 | url = http://www.independent.co.uk/news/people/obituary-allen-coombs-1611270.html | accessdate = 18 October 2012 }}</ref> The original Mark 1 machine was converted into a Mark 2 and an eleventh Colossus was essentially finished when the war in Europe ended.
 
The main units of Flowers' design were as follows.<ref name="FlowersCopelandP96"/>
* A tape transport and photo-electric reading mechanism very similar to Heath Robinson's.
* A coder and adder that simulated the Lorenz machine using thyratron rings.
* A logic unit that performed [[Boolean algebra|Boolean]] operations.
* A master control that contained the electronic counters.
* A printer.
 
Most of the design of the electronics was the work of Tommy Flowers assisted by William Chandler, with Sidney Broadhurst working on the auxiliary electromechanical parts.<ref>{{Harvnb|Randell|2006|pp=146, 147}}</ref> The Mark 2 Colossus was designed while Mark 1 was being constructed. It contained 2400 valves and was both 5 times faster and simpler to operate than the original version.<ref>For comparison, later [[stored-program computer]]s such as the [[Manchester Mark 1]] of 1949 used 4050 valves, {{citation | last = Lavington | first = S. H. | title = The Manchester Mark 1 and Atlas: a Historical Perspective | journal= Communications of the ACM - Special issue on computer architecture|volume=21|issue=1| url=http://www.cs.ucf.edu/courses/cda5106/summer03/papers/mark1.atlas.1.pdf | date = July 1977 | accessdate = 8 February 2009 |doi=10.1145/359327.359331|pages=4–12}} while [[ENIAC]] (1946) used 17,468 valves.</ref>
 
Flowers overcame the problem of synchronizing the electronics with the message tape by generating a [[clock signal]] from the reading of the sprocket holes of the message tape. The speed of operation was thus limited by the mechanics of reading the tape. The tape reader was tested up to 9700 characters per second (53&nbsp;mph) before the tape disintegrated. So 5000 characters/second {{convert|40|ft/s|m/s mph||abbr=on|sigfig=3}} was settled on as the speed for regular use.
 
Colossus included the first ever use of what would now be called [[shift register]]s<ref name="FlowersCopelandP100">{{Harvnb|Flowers|2006|p=100}}</ref> and [[systolic array]]s, enabling five simultaneous tests, each involving up to 100 [[Boolean algebra (logic)|Boolean operations]], on each of the five channels of the punched tape (although in normal operation fewer channels were examined in most runs). This gave an effective processing speed of 25,000 characters per second.<ref name="FlowersCopelandP100"/>
 
==Operation==
{{See also|Cryptanalysis of the Lorenz cipher}}
Colossus used state-of-the-art [[vacuum tube]]s ([[Vacuum tube|thermionic valve]]s), [[thyratron]]s and [[photomultiplier]]s to optically read a paper tape and then applied programmable logical functions to the bits of the key and ciphertext characters, counting how often the function returned "true".
 
Colossus was designed to perform the task of [[Cryptanalysis of the Lorenz cipher#Steps in Wheel Setting|"Wheel Setting"]], that is determining the start point of the stream of key characters in relation to the characters of the enciphered message on the paper tape loop. Initially it was only the χ (''[[chi (letter)|chi]]'') wheels that were examined. To keep the size of the task manageable, only two bits of the ''chi''-stream were examined in the first run,<ref>{{Harvnb|Small1944|p=19}}</ref> then progressively the other bits.<ref>{{Harvnb|Small|1944|p=20}}</ref> Success at this stage allowed the production of a version of the ciphertext from which the ''chi'' component of the key had been removed, the so-called "de-''chi''". This transformation allowed manual methods to be used to work out the settings of the ψ (''[[psi (letter)|psi]]'') and μ ''[[Mu (letter)|mu]]'' "motor" wheels.
 
Later, Colossus was used for determining the settings of the ''psi'' wheels. All of this required that "wheel breaking", the discovery of the pin patterns for all the wheels, had been successfully achieved. Later Mark 2 Colossi were equipped with a special unit to achieve this as well. Programming Colossus was by setting switches and plugging appropriate units together. Sometimes, two or more Colossus computers tried different possibilities simultaneously in what now is called [[parallel computing]], speeding the decoding process by perhaps as much as double the rate of comparison.{{citation needed|date=November 2013}}
 
==Influence and fate==
Colossus was the first of the electronic digital machines with programmability, albeit limited by modern standards:<ref>[http://www.alanturing.net/turing_archive/pages/Reference%20Articles/BriefHistofComp.html#Col A Brief History of Computing. Jack Copeland, June 2000]</ref>
* it had no internally stored programs. To set it up for a new task, the operator had to set up plugs and switches to alter the wiring.
* Colossus was not a general-purpose machine, being designed for a specific cryptanalytic task involving counting and Boolean operations.
 
It was thus not a fully general [[Turing-complete]] computer, even though [[Alan Turing]] worked at [[Bletchley Park]]. It was not then realized that [[Turing completeness]] was significant; most of the other pioneering modern computing machines were also not Turing complete (e.g. the [[Atanasoff–Berry Computer]], the [[Bell Labs]] relay machines (by [[George Stibitz]] et al.), or the first designs of [[Konrad Zuse]]){{Citation needed|date=November 2013}}. The notion of a computer as a general purpose machine—that is, as more than a [[calculator]] devoted to solving difficult but specific problems—did not become prominent for several years.
 
Colossus was preceded by several computers, many of them first in some category. [[Konrad Zuse|Zuse's]] [[Z3 (computer)|Z3]] was the first functional fully program-controlled computer, and was based on electromechanical relays, as were the (less advanced) [[Bell Labs]] machines of the late 1930s ([[George Stibitz]], et al.). The [[Atanasoff–Berry Computer]] was electronic and binary (digital) but not programmable. Assorted [[analog computer]]s were semiprogrammable; some of these much predated the 1930s (e.g., [[Vannevar Bush]]). Babbage's [[Analytical engine]] design predated all these (in the mid-19th century), it was a decimal, programmable, entirely mechanical construction—but was only partially built and never functioned during Babbage's lifetime (the first complete mechanical [[Difference engine|Difference engine No. 2]], built in 1991, does work however). Colossus was the first combining ''digital'', (partially) ''programmable'', and ''electronic''. The first fully programmable digital electronic computer was the [[ENIAC]] which was completed in 1946.
 
The use to which the Colossus computers were put was of the highest secrecy, and the Colossus itself was highly secret, and remained so for many years after the War. Thus, Colossus could not be included in the [[history of computing hardware]] for many years, and Flowers and his associates also were deprived of the recognition they were due.
 
Being not widely known, it therefore had little direct influence on the development of later computers; [[EDVAC]] was the early design which had the most influence on subsequent computer architecture.
 
However, the technology of Colossus, and the knowledge that reliable high-speed electronic digital computing devices were feasible, had a significant influence on the development of early computers in the United Kingdom and probably in the US. A number of people who were associated with the project and knew all about Colossus played significant roles in early computer work in the UK. In 1972, [[Herman Goldstine]] wrote that:
 
{{quote|Britain had such vitality that it could immediately after the war embark on so many well-conceived and well-executed projects in the computer field.<ref>{{Harvnb|Goldstine|1980|p=321}}</ref>}}
 
In writing that, Goldstine was unaware of Colossus, and its legacy to those projects of people such as [[Alan Turing]] (with the [[Pilot ACE]] and [[ACE (computer)|ACE]]), and Max Newman and [[I. J. Good]] (with the [[Manchester Mark 1]] and other early Manchester computers). [[Brian Randell]] later wrote that:
 
{{quote|the COLOSSUS project was an important source of this vitality, one that has been largely unappreciated, as has the significance of its places in the chronology of the invention of the digital computer.<ref>{{Harvnb|Randell|1980|p=87}}</ref> }}
 
Colossus documentation and hardware were [[classified information|classified]] from the moment of their creation and remained so after the War, when [[Winston Churchill]] specifically ordered the destruction of most of the Colossus machines into "pieces no bigger than a man's hand"; Tommy Flowers was ordered to destroy all documentation and burnt them in a furnace at Dollis Hill. He later said of that order: {{quote|That was a terrible mistake. I was instructed to destroy all the records, which I did. I took all the drawings and the plans and all the information about Colossus on paper and put it in the boiler fire. And saw it burn.<ref>{{harvnb|McKay|2010|pp=270–271}}</ref>}} Some parts, sanitised as to their original use, were taken to Newman's [[Royal Society]] [[Computing Machine Laboratory]] at [[Manchester University]].<ref name="ManU">{{cite web | title = A Brief History of Computing | publisher = alanturing.net | accessdate = 26 January 2010 | url = http://www.alanturing.net/turing_archive/pages/Reference%20Articles/BriefHistofComp.html#ACE }}</ref> The Colossus Mark 1 was dismantled and parts returned to the Post Office. Two Colossus computers, along with two replica Tunny machines, were retained, moving to [[GCHQ]]'s new headquarters at [[Eastcote]] in April 1946, and moving again with GCHQ to [[Cheltenham]] between 1952 and 1954.<ref name="Copeland173-175">{{Harvnb|Copeland|2006|pp=173–175}}</ref> One of the Colossi, known as ''Colossus Blue'', was dismantled in 1959; the other in 1960.<ref name="Copeland173-175"/> In their later years, the Colossi were used for training, but before that, there had been attempts to adapt them, with varying success, to other purposes.<ref>{{Harvnb|Horwood|1973}}</ref> Jack Good relates how he was the first to use it after the war, persuading [[NSA]] that Colossus could be used to perform a function for which they were planning to build a special purpose machine.<ref name="Copeland173-175"/> Colossus was also used to perform character counts on [[one-time pad]] tape to test for non-randomness.<ref name="Copeland173-175"/>
 
Throughout this period the Colossus remained secret, long after any of its technical details were of any importance. This was due to the UK's intelligence agencies use of Enigma-like machines which they promoted and sold to other governments, and then broke the codes using a variety of methods. Had the knowledge of the codebreaking machines been widely known, no one would have accepted these machines; rather, they would have developed their own methods for encryption, methods that the UK services might not have been able to break{{Citation needed|date=March 2012}}. The need for such secrecy ebbed away as communications moved to digital transmission and all-digital encryption systems became common in the 1960s.
 
Information about Colossus began to emerge publicly in the late 1970s, after the secrecy imposed was broken when Group Captain Winterbotham published his book ''The Ultra Secret''. More recently, a 500-page technical report on the Tunny cipher and its cryptanalysis – entitled ''General Report on Tunny'' – was released by [[GCHQ]] to the national [[Public Record Office]] in October 2000; the complete report is available online,<ref>{{Harvnb|Good|Michie|Timms|1945}}</ref> and it contains a fascinating [[paean]] to Colossus by the cryptographers who worked with it:
 
{{quote|It is regretted that it is not possible to give an adequate idea of the fascination of a Colossus at work; its sheer bulk and apparent complexity; the fantastic speed of thin paper tape round the glittering pulleys; the childish pleasure of not-not, span, print main header and other gadgets; the wizardry of purely mechanical decoding letter by letter (one novice thought she was being hoaxed); the uncanny action of the typewriter in printing the correct scores without and beyond human aid; the stepping of the display; periods of eager expectation culminating in the sudden appearance of the longed-for score; and the strange rhythms characterizing every type of run: the stately break-in, the erratic short run, the regularity of wheel-breaking, the stolid rectangle interrupted by the wild leaps of the carriage-return, the frantic chatter of a motor run, even the ludicrous frenzy of hosts of bogus scores.<ref>{{Harvnb|Good|Michie|Timms|1945|p=327}} in ''51. Introductory: Impressions of Colossus''</ref>}}
 
==Reconstruction==
[[File:ColossusRebuild 12.jpg|right|thumbnail|320px|Colossus rebuild seen from the rear]]
Construction of a fully functional replica<ref>{{cite web | title = The Colossus Rebuild Project – by Tony Sale | url = http://www.codesandciphers.org.uk/lorenz/rebuild.htm }} Retrieved 30 October 2011</ref> of a Colossus Mark 2 was undertaken by a team led by [[Tony Sale]]. In spite of the blueprints and hardware being destroyed, a surprising amount of material survived, mainly in engineers' notebooks, but a considerable amount of it in the U.S. The optical tape reader might have posed the biggest problem, but [[Arnold Lynch|Dr. Arnold Lynch]], its original designer, was able to redesign it to his own original specification. The reconstruction is on display, in the historically correct place for Colossus No. 9, at [[The National Museum of Computing]], in H Block [[Bletchley Park]] in [[Milton Keynes]], Buckinghamshire.
 
In November 2007, to celebrate the project completion and to mark the start of a fundraising initiative for [[The National Museum of Computing]], a Cipher Challenge<ref>{{cite web | title=Cipher Challenge | url=http://www.tnmoc.org/cipher1.htm | accessdate=1 February 2012 | archiveurl=http://web.archive.org/web/20080801175842/http://www.tnmoc.org/cipher1.htm | archivedate=1 August 2008 }}</ref> pitted the rebuilt Colossus against radio amateurs worldwide in being first to receive and decode three messages enciphered using the [[Lorenz SZ42]] and transmitted from radio station DL0HNF in the [http://en.hnf.de/ ''Heinz Nixdorf MuseumsForum''] computer museum. The challenge was easily won by [[radio amateur]] Joachim Schüth, who had carefully prepared<ref>{{cite web | title = SZ42 Codebreaking Software | url = http://www.schlaupelz.de/SZ42/SZ42_software.html }}</ref> for the event and developed his own signal processing and code-breaking code using [[Ada (programming language)|Ada]].<ref>{{cite web | title = Cracking the Lorenz Code (interview with Schüth) | url = http://www.adacore.com/home/ada_answers/lorenz-code/ }}</ref> The Colossus team were hampered by their wish to use World War II radio equipment,<ref>{{cite news | title = BBC News Article | url = http://news.bbc.co.uk/1/hi/technology/7098005.stm | date = 16 November 2007 | accessdate = 2 January 2010 | first = Mark | last=Ward }}</ref> delaying them by a day because of poor reception conditions. Nevertheless the victor's 1.4&nbsp;GHz laptop, running his own code, took less than a minute to find the settings for all 12 wheels. The German codebreaker said: "My laptop digested ciphertext at a speed of 1.2&nbsp;million characters per second—240 times faster than Colossus. If you scale the CPU frequency by that factor, you get an equivalent clock of 5.8&nbsp;MHz for Colossus. That is a remarkable speed for a computer built in 1944."<ref>{{cite web | title = German Codebreaker receives Bletchley Park Honours | url = http://www.bletchleypark.org.uk/news/docview.rhtm/487682 }}</ref>
 
The Cipher Challenge verified the successful completion of the rebuild project. "On the strength of today's performance Colossus is as good as it was six decades ago", commented Tony Sale. "We are delighted to have produced a fitting tribute to the people who worked at Bletchley Park and whose brainpower devised these fantastic machines which broke these ciphers and shortened the war by many months."<ref>{{cite web | title = Latest Cipher Challenge News 16.11.2007 | url = http://www.tnmoc.org/cipher7.htm | archiveurl = http://web.archive.org/web/20080418084956/http://www.tnmoc.org/cipher7.htm | archivedate = 2008-04-18 }}</ref>
 
==See also==
* [[History of computing hardware]]
* [[List of vacuum tube computers]]
* [[Lorenz Cipher]]
* [[Supercomputer]]
* [[Z3 (computer)|Z3]]
* [[Z4 (computer)|Z4]]
 
==Footnotes==
{{reflist|30em}}
 
==References==
{{refbegin|60em}}
* {{Citation | last = Budiansky | first = Stephen | year = 2000 | title = Battle of wits: The Complete Story of Codebreaking in World War II | publisher = Free Press | isbn = 978-0684859323 }}
* {{Citation | last = Budiansky | first = Stephen | author-link = Stephen Budiansky | title = Colossus, Codebreaking, and the Digital Age | year = 2006 }} in {{Harvnb|Copeland|2006|pp=52–63}}
* {{Citation | last = Chandler | first = W. W. | title = The Installation and Maintenance of Colossus | journal = [[IEEE Annals of the History of Computing]] | volume = 5 | issue = 3 | pages = 260–262 | year = 1983 | doi = 10.1109/MAHC.1983.10083 }}
* {{Citation | last = Coombs | first = Allen W. M. | author-link = Allen Coombs | title = The Making of Colossus | journal = [[IEEE Annals of the History of Computing]] | volume = 5 | issue = 3 | pages = 253–259 |date=July 1983 | url = http://www.ivorcatt.com/47d.htm | doi = 10.1109/MAHC.1983.10085 }}
* {{Citation | last = Copeland | first = B. Jack | author-link = Jack Copeland | title = Colossus and the Dawning of the Computer Age | origyear = 2001 | year = 2011 }} in {{Harvnb|Erskine|Smith|2011|pp=305–327}}
* {{Citation | last = Copeland | first = B. J. | author-link = Jack Copeland | title = Colossus: its origins and originators | journal = [[IEEE Annals of the History of Computing]] | volume = 26 | issue = 4 | pages = 38–45 |date=Oct–Dec 2004 | doi = 10.1109/MAHC.2004.26 }}
* {{Citation | last = Copeland | first = Jack | author-link = Jack Copeland | title = Machine against Machine | year = 2006 }} in {{Harvnb|Copeland|2006|pp=64–77}}
* {{Citation | editor-last = Copeland | editor-first = B. Jack | editor-link = Jack Copeland | title = Colossus: The Secrets of Bletchley Park's Codebreaking Computers | place = Oxford | publisher = Oxford University Press | year = 2006 | isbn = 978-0-19-284055-4 }}
* {{Citation | last = Copeland | first = B. Jack | author-link = Jack Copeland | title = Colossus: Breaking the German ‘Tunny’ Code at Bletchley Park. An Illustrated History | journal = The Rutherford Journal | volume = 3 | year = 2010 }}
* {{Citation | editor-last = Erskine | editor-first = Ralph | editor2-last = Smith | editor2-first = Michael | editor2-link = Michael Smith (newspaper reporter) | title = The Bletchley Park Codebreakers | publisher = Biteback Publishing Ltd | year = 2011 | isbn = 9781849540780}} Updated and extended version of ''Action This Day: From Breaking of the Enigma Code to the Birth of the Modern Computer'' Bantam Press 2001
* {{Citation | last = Fensom | first = Jim | title = Harry Fensom obituary | date = 8 November 2010 | url = http://www.guardian.co.uk/theguardian/2010/nov/08/harry-fensom-obituary | accessdate = 17 October 2012 }}
* {{Citation | last = Fensom | first = Harry | title = How Colossus was Built and Operated - One of its Engineers Reveals its Secrets | year = 2006 }} in {{Harvnb|Copeland|2006|pp=297–303}}
* {{Citation | last = Flowers |first= Thomas H. |authorlink=Tommy Flowers |url=http://www.ivorcatt.com/47c.htm | title =The Design of Colossus |journal=Annals of the History of Computing |volume=5 |issue=3 |year= 1983|pages=239–252 |doi=10.1109/MAHC.1983.10079}}
* {{Citation | last = Flowers | first = Thomas H. | author-link = Tommy Flowers | title = D-Day at Bletchley Park | year = 2006 }} in {{Harvnb|Copeland|2006|pp=78–83}}
* {{Citation | last = Flowers | first = Thomas H. | author-link = Tommy Flowers | title = Colossus | year = 2006 }} in {{Harvnb|Copeland|2006|pp=91–100}}
*{{Citation | last = Gannon | first = Paul | title = Colossus: Bletchley Park's Greatest Secret | year = 2006 | place = London | publisher = Atlantic Books | isbn = 9781843543305 }}
*{{Citation | last = Goldstine | first = Herman H. | author-link = Herman H. Goldstine | title = The Computer from Pascal to von Neumann | publisher = Princeton University Press | year = 1980 | isbn = 978-0-691-02367-0 }}
* {{Citation | last = Good | first = Jack | author-link = I. J. Good | last2 = Michie | first2 = Donald | author2-link = Donald Michie | last3 = Timms | first3 = Geoffrey | title = General Report on Tunny: With Emphasis on Statistical Methods | year = 1945 | id = UK Public Record Office HW 25/4 and HW 25/5 | url = http://www.alanturing.net/turing_archive/archive/index/tunnyreportindex.html | accessdate = 15 September 2010 }} That version is a facsimile copy, but there is a transcript of much of this document in '.pdf' format at: {{Citation | last = Sale | first = Tony | author-link = Anthony Sale | title = Part of the "General Report on Tunny", the Newmanry History, formatted by Tony Sale| year = 2001 | url = http://www.codesandciphers.org.uk/documents/newman/newman.pdf | accessdate = 20 September 2010 }}, and a web transcript of Part 1 at: {{Citation | last = Ellsbury | first = Graham | title = General Report on Tunny With Emphasis on Statistical Methods | url = http://www.ellsbury.com/tunny/tunny-001.htm | accessdate = 3 November 2010 }}
* {{Citation | last =Good |first=I. J. |authorlink=I. J. Good| title =Early Work on Computers at Bletchley|journal=IEEE Annals of the History of Computing|volume=1|issue=1|year= 1979|pages=38–48|doi=10.1109/MAHC.1979.10011}}
* {{Citation | last =Good |first=I. J. |authorlink=I. J. Good| chapter=Pioneering Work on Computers at Bletchley|editor1-first=Nicholas |editor1-last=Metropolis|editor2-first=J. |editor2-last=Howlett|editor3-first =Gian-Carlo |editor3-last=Rota|title=A History of Computing in the Twentieth Century|publisher=Academic Press|location=New York|year= 1980|isbn=0124916503}}
* {{Citation | last = Horwood | first = D.C. | title = A technical description of Colossus I: PRO HW 25/24 | year = 1973 | url = http://www.youtube.com/watch?v=JF48sl15OCg |format=YouTube video}}
* {{Citation | last = McKay | first = Sinclair | title = The Secret Life of Bletchley Park: The WWII Codebreaking Centre and the men and women who worked there | place = London | publisher = Aurum Press | year = 2010 | isbn = 9781845135393 }}
* {{Citation | last = Randell | first = Brian | author-link = Brian Randell |chapter=Colossus: Godfather of the Computer|origyear=1977|title=The Origins of Digital Computers: Selected Papers|publisher= [[Springer Science+Business Media|Springer-Verlag]]|location= New York|year= 1982|isbn=9783540113195 }}
* {{Citation | last = Randell | first = Brian | author-link = Brian Randell | editor-last = Metropolis | editor-first = N. | editor-link = Nicholas Metropolis| editor2-last = Howlett | editor2-first = J. | editor2-link = Jack Howlett | editor3-last = Rota | editor3-first = Gian-Carlo | editor3-link = Gian-Carlo Rota| title = A History of Computing in the Twentieth Century | chapter = The Colossus | pages = 47–92 | year = 1980 | url = http://www.cs.ncl.ac.uk/publications/books/papers/133.pdf | isbn = 978-0124916500 }}
* {{Citation | last = Randell | first = Brian | authorlink = Brian Randell | title = Of Men and Machines | year = 2006 }} in {{Harvnb|Copeland|2006|pp=141–149}}
* {{Citation | last = Sale | first = Tony | authorlink = Tony Sale | editor1-last = Rojas | editor1-first = Raúl | editor2-last = Hashagen | editor2-first = Ulf | title = The First Computers: History and Architecture | year = 2000 | publisher = The MIT Press | location = Cambridge, Massachusetts | isbn = 0-262-18197-5 | pages = 351–364 | chapter = The Colossus of Bletchley Park – The German Cipher System }}
* {{citation|first= Albert W. |last=Small|url=http://www.codesandciphers.org.uk/documents/small/smallix.htm |title=The Special Fish Report|date=December 1944}} describes the operation of Colossus in breaking Tunny messages
* {{Citation | last = Tutte | first = William T. | authorlink = W. T. Tutte | year = 2006 | title = Appendix 4: My Work at Bletchley Park }} in {{Harvnb|Copeland|2006|pp=352–369}}
* {{Citation | last = Wells | first = B | title = A Universal Turing Machine Can Run on a Cluster of Colossi | journal = Abstracts of the American Mathematical Society | volume = 25 | pages = 441 | year = 2004}}
* {{Citation | last = Wells | first = Benjamin | title = The PC-User's Guide to Colossus | year = 2006 }} in {{Harvnb|Copeland|2006|pp=116–140}}
{{refend}}
 
==Further reading==
*{{Youtube|id=knXWMjIA59c|title=Colossus: Creating a Giant }} A short film made by Google to celebrate Colossus and those who built it, in particular Tommy Flowers.
* {{Citation | last = Cragon | first = Harvey G. | title = From Fish to Colossus: How the German Lorenz Cipher was Broken at Bletchley Park | place = Dallas | publisher = Cragon Books | year = 2003 | isbn = 0-9743045-0-6 }} – A detailed description of the cryptanalysis of Tunny, and some details of Colossus (contains some minor errors)
* {{Citation | last = Enever | first = Ted | title = Britain's Best Kept Secret: Ultra's Base at Bletchley Park | publisher = Sutton Publishing, Gloucestershire | year = 1999 | edition = 3rd | isbn = 978-0-7509-2355-2 }} – A guided tour of the history and geography of the Park, written by one of the founder members of the Bletchley Park Trust
* {{Citation | last = Gannon | first = Paul | title = Colossus: Bletchley Park's Greatest Secret | year = 2007 | publisher = Atlantic Books | isbn = 978-1-84354-331-2 }}
* {{Citation | last = Rojas | first = R. | last2 = Hashagen | first2 = U. | title = The First Computers: History and Architectures | publisher = MIT Press | year = 2000 | isbn = 0-262-18197-5}} – Comparison of the first computers, with a chapter about Colossus and its reconstruction by Tony Sale.
* {{citation|authorlink=Tony Sale|last=Sale|first= Tony|title=The Colossus Computer 1943–1996: How It Helped to Break the German Lorenz Cipher in WWII|publisher=M.&M. Baldwin|location= Kidderminster|year= 2004|isbn= 0-947712-36-4}} A slender (20 page) booklet, containing the same material as Tony Sale's website (see below)
* {{Citation | last = Smith | first = Michael | authorlink = Michael Smith (newspaper reporter) | title = Station X: The Codebreakers of Bletchley Park | edition = Pan Books | series = Pan Grand Strategy Series | year = 2007 | origyear = 1998 | publisher = Pan McMillan Ltd | location = London | isbn = 978-0-330-41929-1 }}
 
==Other meanings==
There was a fictional computer named ''Colossus'' in the movie ''[[Colossus: The Forbin Project]]''. Also see [[List of fictional computers]]. [[Neal Stephenson]]'s novel ''[[Cryptonomicon]]'' (1999) also contains a fictional treatment of the historical role played by Turing and Bletchley Park.
 
==External links==
* [http://www.tnmoc.org/ The National Museum of Computing]
* [http://www.codesandciphers.org.uk/index.htm Tony Sale's Codes and Ciphers] Contains a great deal of information, including:
** [http://www.codesandciphers.org.uk/virtualbp/fish/colossus.htm Colossus, the revolution in code breaking]
** [http://www.codesandciphers.org.uk/lorenz/index.htm Lorenz Cipher and the Colossus]
*** [http://www.codesandciphers.org.uk/lorenz/colossus.htm The machine age comes to Fish codebreaking]
*** [http://www.codesandciphers.org.uk/lorenz/rebuild.htm The Colossus Rebuild Project]
*** [http://www.codesandciphers.org.uk/lorenz/mk2.htm The Colossus Rebuild Project: Evolving to the Colossus Mk 2]
*** [http://www.codesandciphers.org.uk/lorenz/colwalk/colossus.htm Walk around Colossus] A detailed tour of the replica Colossus – make sure to click on the "More Text" links on each image to see the informative detailed text about that part of Colossus
** [http://www.codesandciphers.org.uk/lectures/ieee.txt IEEE lecture] – Transcript of a lecture Tony Sale gave describing the reconstruction project
* [http://news.bbc.co.uk/1/hi/technology/3754887.stm BBC news article reporting on the replica Colossus]
* [http://news.bbc.co.uk/1/hi/technology/7094881.stm BBC news article: "Colossus cracks codes once more"]
* [http://news.bbc.co.uk/1/hi/technology/8492762.stm BBC news article: BBC news article: "Bletchley's code-cracking Colossus" with video interviews 2010-02-02]
*[http://www.colossus-computer.com/contents.htm Website on Copeland's 2006 book] with much information and links to recently declassified information
* [http://www.bcs.org/upload/pdf/ewic_tur04_paper3.pdf Was the Manchester Baby conceived at Bletchley Park?]
* [http://www.youtube.com/watch?v=NWYzwIjSk6s Walk through video of the Colossus rebuild at Bletchley Park]
 
{{Use dmy dates|date=April 2012}}
{{commons category|Colossus computer}}
 
{{DEFAULTSORT:Colossus Computer}}
[[Category:Bletchley Park]]
[[Category:Cryptanalytic devices]]
[[Category:Military computers]]
[[Category:World War II British electronics]]
[[Category:Early British computers]]
[[Category:Vacuum tube computers]]
[[Category:1940s computers]]
[[Category:English inventions]]
[[Category:History of electronic engineering]]

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