I remember when I where a wee whippersnapper; My dad kept a program's worth of punch cards stacked on one of the shelves at his work. They where on the shelf off to the side in one of the print rooms under his care. It was years before I was old enough to comprehend how they would have worked back in the day.

Even now with far more knowledge of systems, imagining feeding those into a reader one at a time is almost like legend. If you screwed up the order you'd be starting over because the whole thing would be loaded into ram; no save points on some storage disk inside the mini.