This is a detailed account of the work done to build Colossus at Bletchley Park during WWII. There is a lot of information that I haven’t read elsewhere, including a lot of detail about the individual Fish links and variants of ciphers used by the Germans.

A lot of the details are reserved for the appendix, so you can follow the narrative without getting too bogged down. (I’ve read so many accounts of wheel breaking, wheel setting, and so on, I did skip those passages in this book.)

I took lots of notes and learnt quite a few things, and something I was struck by is the number of parallels to modern software development. Although the output looks very different, many of the design principles look very familiar.

I’d recommend this for anybody interested in the history of Bletchley Park.

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