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punched card

punched card:: alt. `punch card' [techspeak] n.obs. The
   signature medium of computing's Stone Age, now obsolescent
   outside of some IBM shops.  The punched card actually predated
   computers considerably, originating in 1801 as a control device for
   mechanical looms.  The version patented by Hollerith and used with
   mechanical tabulating machines in the 1890 U.S. Census was a piece
   of cardboard about 90 mm by 215 mm.  There is a widespread myth
   that it was designed to fit in the currency trays used for that
   era's larger dollar bills, but recent investigations have falsified

IBM (which originated as a tabulating-machine manufacturer) married the punched card to computers, encoding binary information as patterns of small rectangular holes; one character per column, 80 columns per card. Other coding schemes, sizes of card, and hole shapes were tried at various times.

The 80-column width of most character terminals is a legacy of the IBM punched card; so is the size of the quick-reference cards distributed with many varieties of computers even today. See chad, chad box, eighty-column mind, green card, dusty deck, lace card, card walloper.