Reading a card is simple. There are 80 columns on a classic card. If a column has a single punch over a number, then that’s what that column represents. So if you had a card with a punch over ...

but those never really caught on to the same scale as the classic 80-column card. To punch a number on the card, a machine made a hole in one of the bottom 10 columns. So a hole in the “1” row ...