from
The Free On-line Dictionary of Computing (8 July 2008)
punched card
punch card
<storage, history> (Or "punch card") The signature medium of
computing's Stone Age, now long obsolete outside of a few
{legacy systems}. The punched card actually predates
computers considerably, originating in 1801 as a control
device for {Jacquard looms}. {Charles Babbage} used them as a
data and program storage medium for his {Analytical Engine}:
"To those who are acquainted with the principles of the
Jacquard loom, and who are also familiar with analytical
formulæ, a general idea of the means by which the Engine
executes its operations may be obtained without much
difficulty. In the Exhibition of 1862 there were many
splendid examples of such looms. [...] These patterns are then
sent to a peculiar artist, who, by means of a certain machine,
punches holes in a set of pasteboard cards in such a manner
that when those cards are placed in a Jacquard loom, it will
then weave upon its produce the exact pattern designed by the
artist. [...] The analogy of the Analytical Engine with this
well-known process is nearly perfect. There are therefore two
sets of cards, the first to direct the nature of the
operations to be performed -- these are called operation
cards: the other to direct the particular variables on which
those cards are required to operate -- these latter are called
variable cards. Now the symbol of each variable or constant,
is placed at the top of a column capable of containing any
required number of digits."
-- from Chapter 8 of Charles Babbage's "Passages from the Life
of a Philosopher", 1864.
The version patented by {Herman Hollerith} and used with
mechanical tabulating machines in the 1890 US 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 this.
{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}.
[{Jargon File}]
(1998-10-19)