A punch card is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions. The information might be data for data processing applications or, as in earlier times, used to directly control automated machinery.

The terms IBM card, or Hollerith card, specifically refer to punch cards used in semiautomatic data processing.

Punch cards were widely used through much of the 20th century in what became known as the data processing industry, where specialized and increasingly complex unit record machines, organized into data processing systems, used punched cards for data input, output, and storage. Many early digital computers used punched cards, often prepared using keypunch machines, as the primary medium for input of both computer programs and data.

Punched cards are now obsolete as a recording medium, as the last election in which they were used was the 2014 midterms, according to the Pew Research Center.

Semen Korsakov was the first to use punch cards in informatics for information store and search. Korsakov announced his new method and machines in September 1832; rather than seeking patents, he offered the machines for public use.

Herman Hollerith

In 1881, Herman Hollerith began designing a machine to tabulate census data more efficiently than by traditional hand methods. The U.S. Census Bureau had taken eight years to complete the 1880 census, and it was feared that the 1890 census would take even longer. Hollerith invented and used a punched card device to help analyze the 1890 U.S. census data. His great breakthrough was his use of electricity to read, count and sort punched cards whose holes represented data gathered by the census-takers.

His machines were used for the 1890 census and accomplished in one year what would have taken nearly 10 years of hand tabulating. In 1896, Hollerith founded the Tabulating Machine Company to sell his invention, the Company became part of IBM in 1924.

Hollerith first got his idea for the punch-card tabulation machine from watching a train conductor punch tickets. For his tabulation machine, he used the punch card invented in the early 1800s, by a French silk weaver called Joseph-Marie Jacquard. Jacquard invented a way of automatically controlling the warp and weft threads on a silk loom by recording patterns of holes in a string of cards.

Hollerith's punch cards and tabulating machines were a step toward automated computation. His device could automatically read information which had been punched onto a card. He got the idea and then saw Jacquard's punchcard. Punch card technology was used in computers up until the late 1970s. Computer "punched cards" were read electronically, the cards moved between brass rods, and the holes in the cards created an electric current where the rods would touch.

What Is a Chad?

A chad is a small piece of paper or cardboard produced in punching paper tape or data cards; also can be called a piece of chad. The term originated in 1947 and is of unknown origin. In laymen's terms, chad is the punched out parts of the card — the holes.