How did punch card systems work? Professor Brailsford delves further into the era of mainframe computing with this hands-on look at punch cards. Extra Material on Punch Cards: Extra Material - behind the scenes: Mainframes to Unix: Near to the Metal: Addendum: "ICL punched cards actually have 12 rows -- not 11 as stated in the film. Choosing any two hole positions out of 12 gives 66 combinations -- which can represent 66 different characters. This in turn is more than enough for the 64 possibilities of a 6-bit character held in ICL computer memory. Also, some special characters could actually utilise three hole configurations adding further to the possibilities." This video was filmed and edited by Sean Riley. Computer Science at the University of Nottingham: Computerphile is a sister project to Brady Haran's Numberphile. See the full list of Brady's video projects at: