The punch card is a recording medium for holding information for use by automated data processing machines. Made of thin cardboard, the punch card represents information by the presence or absence of holes in predefined positions on the card. In the first generation of computing, from the 1920s into the 1950s, punch cards were
the primary medium for data storage and processing. Eventually, during the late 1970’s to early 1980’s, the punch card was phased out as a medium for storage of computer data and replaced by huge floppy disks.

The cards usually had 80 columns and could hold up to 80 characters. The contents of a card could continue on another card. The cards were put one by one into the reader, that recognized the combinations of punched holes and thus read the values.

The system of reading was based on either electromechanic or photoelectric principle. The first one recognised holes, by making contact through them. The photoelectric reader had a light on one side of the card and photosensors, that sensed the light coming through the holes, on the other side. Speeds of reading, depending on the design, range from a couple of hundred to over thousand cards per minute.

Image from: Elektronski ra?unalniki, ve? avtorjev, 1971