Punched cards

A punched card or punch card is a piece of stiff paper that can be used to contain digital information represented by the presence or absence of holes in predefined positions. The information might be data for data processing applications or, in earlier examples, used to directly control automated machinery. The terms IBM card, or Hollerith card specifically refer to punched cards used in semiautomatic data processing.

Punched 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.

While punched cards are now obsolete as a recording medium, as of 2012, some voting machines still use punched cards to record votes.

Basile Bouchon developed the control of a loom by punched holes in paper tape in 1725. The design was improved by his assistant Jean-Baptiste Falcon and Jacques Vaucanson (1740) Although these improvements controlled the patterns woven, they still required an assistant to operate the mechanism. In 1801 Joseph Marie Jacquard demonstrated a mechanism to automate loom operation. A number of punched cards were linked into a chain of any length. Each card held the instructions for shedding (raising and lowering the warp) and selecting the shuttle for a single pass. It is considered an important step in the history of computing hardware.

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