Colossus was designed during World War II for one purpose -- decoding top secret encrypted messages sent by Germany using the Enigma Machine. Germany thought their messages were safe, but the Allies had cracked the code using these computers, and were therefore able to win the war. The Colossus was purpose built, is not a general purpose computer but instead performs a specific processing task. Several instances of the Colossus was built during World War II.
The Harwell Decatron was designed to automate mathematical computations which it did for several years.
About the Author(s)
David Herron:
David Herron is a writer and software engineer focusing on the wise use of technology. He is especially interested in clean energy technologies like solar power, wind power, and electric cars. David worked for nearly 30 years in Silicon Valley on software ranging from electronic mail systems, to video streaming, to the Java programming language, and has published several books on Node.js programming and electric vehicles.