Punch card

The punch card (or "Hollerith" card) is a recording medium for holding information for use by automated data processing machines. Made of stiff 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 the punch card would be phased out and replaced with huge floppys for media storage, for loading data, in the late 1970's, early 1980's.

Other formats

Other coding schemes, sizes of card, and hole shapes were tried at various times. Mark sense cards had printed ovals that humans would fill in with a pencil. Specialized card punches could detect these marks and punch the corresponding information into the card. There were also needle cards with all the punch positions perforated so data could be punched out manually, one hole at a time, with a device like a blunt pin with its wire bent into a finger-ring on the other end. In the early 1970s, IBM introduced a new, smaller, round-hole, 96-column card format along with the IBM System 3 computer.

Related Topics:
Coding - Needle cards - 1970s - IBM System 3

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Aperture cards are a specialized use of punch cards for storing "blueprints". A drawing is photographed onto 35 mm film and the image is mounted in a window on the right half of the punch card. Information about the drawing, e.g. the drawing number, is punched in the left half.

Related Topics:
Blueprint - 35 mm film

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IBM punch cards could be used with early computers in a binary mode where every column (or row) was treated as a simple bitfield, and every combination of holes was permitted . In this binary mode, cards could be made in which every possible punch position had a hole: these were called "lace cards." For example, the IBM 700/7000 series scientific computers treated every row as two 36-bit words, usually in columns 1-72, ignoring the last 8 columns (but this was programable using a plugboard in the card reader and punch to select the 72 columns used). Other computers, like the IBM 1130, used every possible hole.

Related Topics:
Lace card - IBM 700/7000 series - IBM 1130

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