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Brief Bio: Tommy Flowers

July 16, 2014 mgroves 0 Comments
Tags: Brief Bio

Welcome to the latest installment of the Brief Bio series, where I'm writing up very informal biographies about major figures in the history of computers. Please take a look at the Brief Bio archive, and feel free to leave corrections and omissions in the comments.

Tommy Flowers

Tommy Flowers was born in London in 1905. He was the son of bricklayer (not a banker). While working as a mechanical engineer's apprentice, he tooks night classes to get an EE degree. It's interesting to compare his father's profession with others in this series. Sons of bankers seem to very math and theory oriented, while Tommy Flowers seems to be more mechanically and hands-on oriented. There's plenty of overlap, and all are brilliant, of course.

From 1935 on, Tommy Flowers seemed to be most focused on phone exchanges, and was interested in making them completely electronic.

Were it not for the start of World War II, Flowers might have devoted his entire career to phone exchanges. In 1941, Alan Turing (whom I will definitely get to later), working at the famed Bletchley Park, asked for Tommy Flowers to build a decoder for the Bombe. This decoder wasn't ever completed, but this was the start of a professional relationship between Flowers, Turing, and the best code-breakers in England.

One of the codebreaking devices created at Bletchley Park was the Heath Robinson. Tommy Flowers built the "combining unit" for this machine. This module used vacuum tubes (the British call them "valves") to implement boolean XOR logic. This may sound trivial now, but the use of vacuum tubes was a key innovation here that Tommy Flowers would later apply to the Colossus.

Vacuum tubes are all but obsolete these days--mainly replaced by the transistor for most applications. The "T" in "CRT" stands for tube, so maybe you have a few of those still around. Traditional light bulbs are also vacuum tubes. Here's a video on the many applications of vacuum tubes. In particular note, at 7:10, it talks about how tubes are used for amplification. If you then move ahead to 13:14, you'll see that the same grid used for amplication can also be used for control: closing, opening, or modifying a circuit (closing and opening being useful for logic, but computers aren't mentioned in this video).

Flowers is most famous for the design and creation of Colussus, which is often considered to be the first electronic, programmable computer. It was used for code breaking, and especially key in the Normandy invasion. This machine used around 2000 vacuum tubes, which is over 10 times as many as other electronics (like RADAR) used and put reliability into doubt: they often broke and/or just wore out. That's a headache when you depend on a handful of tubes; it's debilitating with thousands. However, Flowers previous work with vacuum tubes caused him to believe that keeping the tubes running continuously was key to improving their reliability.

There are a lot of videos and information out there about Colossus, so I thought I'd link to a few that I found particularly interesting.

After the war, Flowers went back to work on phone systems at the Post Office Research Station, where he continued to advance electronic phone exchanges. He retired in 1969, and he published a book on telephone exchanges in the early 70s. It wasn't until the 1970s that Flowers's work on Colussus was able to be made public. Until then it was a closely guarded secret that Flowers couldn't even tell his family about. They just knew it was important, top secret work. Flowers went on to write about Colossus in The Design of Colossus. He started receiving general recognition for his accomplishments, and received many awards and honors.

He died in 1998 at age 92.


Matthew D. Groves

About the Author

Matthew D. Groves lives in Central Ohio. He works remotely, loves to code, and is a Microsoft MVP.

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