Many many years ago, computers were programmed using punch cards. Below are a couple that I've scanned, they're from when I was in high school (during the mid 1980s). For a couple of math classes, we were allowed to pick from several programs (e.g. to print a banner, a calendar, biorhythm charts, etc.), and we filled in the cards to suit (to call the program we wanted, and provide it with parameters).
The first one is really a punch card—those black rectangles are holes cut through the card. This one's a cover card for a deck, it's prepared for processing batches of programs that have some commonality between them. It's precut to do something that we didn't have a choice about, which was never explained to us, but I might guess from the other printing on the card that it's something specific to our school.
The second one is slightly different, instead of punching holes, you fill in specific spaces with a lead pencil (they're designed to be simpler for people to create—easier than punching holes into a card). If you wanted to use a character within one of the bubbles, you filled it in; or if you wanted to use a character between two bubbles, you filled in the bubbles either side of it.