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A punch card is a simple piece of paper stock that can hold data in the form of small punched holes, which are strategically positioned to be read by computers or machines. It is an early computer programming relic that was used before the many data storage advances relied upon today.
A punch card is also known as a punched card, IBM card or Hollerith card.
In the earliest, most primitive computing setups, punch cards were fed into large computers that held very little memory or data. These large computers were sometimes called big iron machines. One example of the use of punch card technology is in the renowned Turing machine invented by Alan Turing, a leader at the time in the information technology movement.
Obvious design weaknesses led punch card technology to become quickly obsolete, as newer forms of data storage were invented. Interestingly, the unit of data used by a punch card does not typically correlate to the smallest units of data held in today’s storage media. Rather than using binary data, as they do today, punch cards used individual characters - mostly letters and numbers - wherein each punch in the card represented the selection of one particular character.
Punch cards, like mainframe and supercomputers of the late 20th century, are now mostly historical items of curiosity.