A Mark 2 Colossus computer. The ten Colossi were the world's first (semi-) programmable electronic computers, the first having been built in 1943. Unknown author - This file is from the collections of The National Archives (United Kingdom), catalogued under document record FO850/234. A Colossus Mark 2 codebreaking computer being operated by Dorothy Du Boisson (left) and Elsie Booker (right), 1943 The image shows a Mark 2 Colossus computer, one of the ten machines built during World War II for British codebreaking efforts. Two women, Dorothy Du Boisson (left) and Elsie Booker (right), operate the large electronic computer, which occupies an entire room. The machine is composed of panels filled with switches, dials, cables, and vacuum tubes, representing the first (semi-) programmable electronic computers in history, built in 1943 to help decipher encrypted German communications at Bletchley Park. https://en.wikipedia.org/wiki/Bletchley_Park#/media/File:Colossus.jpg