With the UK getting ready to celebrate V.E. Dayâs 75th anniversary with a Bank Holiday this Friday (albeit in lockdown conditions) we take a look at the world of the Digital Computer and the role of Bletchley Park on the development of todayâs computers.
In our quarantine, weâve been able to remotely access our company resources over the internet, hold video conferencing meetings over Skype, Teams and Zoom and keep up with friends and family over social media. Back at the start of the second world war, the digital computer was only just being born.
The Term âComputerâ in 1939 referred to a person whoâs job was to perform calculations, and the only way to keep in contact remotely was via the telephone and a manned operator switchboard.
The UK Security Agency GCHQ evolved from the Government Code and Cypher School (GC&CS). At the outbreak of war, the GC&CS consisted of a handful of people working on deciphering diplomatic encrypted messages, based in a single room in a building in London.
Prior to war, Germany started to invest in encryption machines to speed up and secure the encryption of information that was broadcast over wireless stations. These machines were thought to create ciphers that were unbreakable.
Through a network of listening stations around the cost of the UK, British intelligence services could intercept the wireless transmissions sent in standard Morse Code, but messages meant nothing without a way to decipher them.
It quickly became obvious that being based outside of London would be sensible, and Bletchley Park, a stately home in modern day Milton Keynes, was chosen for itâs central location, easy access to London, Birmingham, Manchester and other cities via train and road, proximity to Oxford and Cambridge universities for students, and close to the main trunk telephone and telegraph networks for the UK.
BP as it became know, or sometimes Station X due to the radio intercept station that was setup on the site, soon expended and by the end of the war 10,000 personnel were working at the site, mostly in brick built outbuildings referred to as the Huts and Blocks.
Most of these staff were female and weâre involved in performing complex calculations and programming electronic machines to enable them to rapidly crack the encrypted intercepted messages. These we BPâs first Computers.
Some of Britainâs finest mathematicians and professors were recruited via various secret (and sometimes not so secret) ways into BP, and were set to work on finding a way to break into the various ciphers that the Germans were using to encrypt their messages.
Names such as Alan Turing, Gordon Welchman, Bill Tuttle, Max Newman and Joan Clarke were amongst the many cryptanalysts working on various codebreaking problems, including the well known Enigma traffic.
Early in the War, British, French and Polish codebreakers met up in a forest in France to discuss a combined codebreaking effort. It was clear that the Polish team had achieved significantly more success against German codes and ciphers, and had started designing a machine to help break the German Enigma traffic.
Alan Turing and Gordon Welchman later replicated the Polish machine at Blethcley Park. Called the Bombe, it was the first electromechanical device used to rapidly check encrypted messages against an array of possible encryption settings, stopping when it found a possible match.
The Germans continuously made improvements to their encryption machines, adding additional encryption devices or changing how the devices were used, but the basic machine remained relatively the same.
Then, in 1941 a new machine was used. British broadcasting stations could hear the signal, but it wasnât sent in Morse Code. The Germans had used a device that encrypted the information as it was entered, and sent it automatically in teleprinter code at about ten characters per second, far too fast for a human to write down.
Using a British teleprinter, the British were able to intercept the messages but they could not crack the cipher.
With the help of other signal intelligence, it was realised that these messages were being sent to and from German high command to the army commandos in Europe, and as such they were of great importance.
By studying the encrypted messages, and with the help of German operator errors, a team of cryptanalysts working under Ralph Tester devised a machine that could help to decrypt this new cipher.
Their work eventually produced the Colossus, the worlds very first programmable digital electronic computer.
Tommy Flowers, a post office engineer, helped build the first Colossus prototype. He then helped refine the design into the Colossus Mark 2 which went operational in June 1944.
Colossus was programmed by means of a plug board and switches, it used vacuum tubes (Thermionic Valves) to perform boolean operations much like the bits in modern computers.
Itâs classed as the first âFirst Generationâ computer; it was digital and programmable. This meant it could be used to solve different problems simply by reprogramming it.
By the end of the war, there were 10 Colossi in operation. The British government ordered their blueprints be destroyed asking with most of the machines in order to keep the secret that Britain could intercept and decrypt messages sent on this need system.
After the war, some of the mathematicians who had worked on designing machines for BP carried their ideas forward in UK universities, designing ever more complex and more universal computers.
American mathematicians who had been working at Bletchly Park in the latter years of the war had more freedom to advance their development of digital computers, being outside the scope of the British Official Secrets Act.
The second generation of computers built upon the likes of Colossus, but moved to digital switches rather than vacuum tubes, and made use of storable programs that could be recalled from the computers memory.
This then evolved into the third generation of computers which is what we have today, making use of integrated circuits, long term storage and human interface devices.
So as part of your VE Day celebrations, give a moment to remember the service of all the staff based at Bletchly Park and itâs listening stations who worked together and gave birth to the digital age.
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