Who is Tommy Flowers?
Tommy Flowers was born in 1905. He was an apprentice in the field of mechanical engineering and eventually earned a degree in electrical engineering at the University of London. He worked primarily for the General Post Office in the Telecommunications branch. By 1939 he had deduced that an all-electronic switching system was possible for telephone conversations. His background in switching electronics proved beneficial during World War II.
Photo of Tommy Flowers
WWII Encryption and the Lorenz Cipher Machine
Before I explain why Tommy Flowers played a significant part in computing history, I will explain what the initial problem, posed by Max Newman at the Government Code and Cypher School at Bletchley Park, was. During WWII, the German army used something called the electro-mechanical Lorenz SZ40/42 in-line cipher machine to encrypt important messages. Max Newman posed the problem of how those radio teleprinter messages could be deciphered. The Lorenz machine enciphered messages by combining 5-bit plain-text characters with a stream of key characters. The keystream itself was produced by twelve pin-wheels. To decrypt the messages, code-breakers had to figure out what the Lorenz key settings were. Flowers and his team were able to come up with a way to solve that problem.
Lorenz cipher machine with cover removed
Colossus
Developed by Tommy Flowers and his team, Colossus was the first programmable electronic digital computer in the world. These computers were used by British code-breakers during the war to help analyze the Lorenz cipher. It is said that if the Allies did not have the information contained in the encrypted telegraphic messages between the German High Command and their armies, the war would have been at least two years longer. Colossus used vacuum tubes to perform Boolean operation and calculations. The machines were used primarily to find possible Lorenz key settings, not to decrypt messages completely as is often thought.
Colossus Mark 2 computer
History with Alan Turing
Because most of the hardware and blueprints for Colossus were destroyed, the creators did not receive proper credit for their advancements in digital electronic computing, at least not during their lifetimes. There was an effort to keep the project secret, which led to the destruction of any documentation. It has been wrongly stated in some publications that Alan Turing designed Colossus to aid in decoding a different cipher machine, called Enigma. Turing’s machine however, was called Bombe and was not the same as the computer that Tommy Flowers developed. Prior to Colossus’ development, Flowers was involved in improving the Bombes machines that Turing developed, and it was Alan Turing himself who recommended Flowers to Max Newman.
Why is this important?
Flowers was a computing pioneer, not only did the device he develop use vacuum tubes, it also had the first practical use of shift registers and systolic arrays. These arrays enabled five tests to happen simultaneously, each test involving up to 100 Boolean calculations. Most importantly though, both models of Colossus were programmable using switches and plug panels, something that had not been implemented whatsoever in previous deciphering devices. Unfortunately, this was a single purpose machine. If we compare it to the later stored-program computers, which used around 4050 thermionic valves (vacuum tubes), and the ENIAC, which used 17,468 , Colossus used a modest 1500 in the first version and 2400 in the second. It is quite a shame that Thomas Flowers was not rewarded for his pioneering work in World War II, he passed away from heart failure at the age of 92 in 1998.
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