Punch cards used to be a key part of computing. The IBM 1402 Card Reader/Punch (1959) could read or punch hundreds of cards a minute. But the punch at https://twitter.com/ComputerHistory stopped punching the first 16 columns. An explanation of the punch unit and how we fixed it... 1/9
A punch card holds 80 characters, one per column. The holes in each column represent the character. Cards can be punched manually with a typewriter-like keypunch. Or the computer can punch cards at high speed through an attached reader/punch. 2/9