Earlier quoted context omitted.
Kids, today! You have no idea how lucky you are. At the time of writing this code, there were no 32" color monitors, IDEs, code text editors, or source code management systems. Code was first written out by hand and then typed onto punch cards or paper tape. These were fed into a mainframe computer for assembly. If you made a mistake, you had to find cards (by hand), remove and replace them with corrected cards. Get…
Yup..."back then" you would arrange all your cards in a shoebox and then take a marker and make a diagonal mark from top left to bottom right JUST IN CASE you dropped said shoebox on the way to class to turn in your homework/take home test. Without that mark there's no easy way to recreate the correct order of the punch cards. Source: dad was an engineering major in the early 70s.
I think they retired the punches after my freshman year or the year after.