Difference between revisions of "Punched card"

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They were actually a hangover from a pre-[[electronic]] stage of [[data processing]]; Herman Hollerith pioneered the use of cards for data storage for the 1890 U.S. census, and [[International Business Machines|IBM]] became a world-wide colossus before World War II on its dominance of card processing.
 
They were actually a hangover from a pre-[[electronic]] stage of [[data processing]]; Herman Hollerith pioneered the use of cards for data storage for the 1890 U.S. census, and [[International Business Machines|IBM]] became a world-wide colossus before World War II on its dominance of card processing.
  
Physically, they were stiff, thin cardboard, typically slightly less than .01 inches thick. A number of different formats were used over time. but the most popular by far was IBM's format, introduced in 1928: they were 7-3⁄8 by 3-1⁄4 inches in size, with rectangular holes in 80 columns of 12 rows.
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Physically, they were stiff, thin cardboard, typically slightly less than .01 inches thick. A number of different formats were used over time, but the most popular by far was IBM's format, introduced in 1928: they were 7-3⁄8 by 3-1⁄4 inches in size, with rectangular holes in 80 columns of 12 rows.
  
In the pre-[[electronic]] era brushes were used to sense the presence or absence of a hole; later on, optical sensors were common.
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A card could hold up to 80 alphanumeric characters, one per column: numbers were indicated by a single punch in rows 1-10; letters were indicated by a punch in row 10/11/12, plus a punch in rows 1-9. Cards could also hold [[binary]] data, with more than two holes per column; by convention, a 7 and 9 punch in the first column indicated that the rest of the card held binary data.
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In the pre-electronic era brushes were used to sense the presence or absence of a hole; later on, optical sensors were common.
  
 
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[[Category: Device Basics‎‎]]
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[[Category: Device Basics]]

Latest revision as of 05:36, 11 January 2021

Punched cards were a very popular medium for input/output and data storage in the early period of computer usage. Data was stored in them by the presence, or absence, of holes punched in pre-determined locations.

They were actually a hangover from a pre-electronic stage of data processing; Herman Hollerith pioneered the use of cards for data storage for the 1890 U.S. census, and IBM became a world-wide colossus before World War II on its dominance of card processing.

Physically, they were stiff, thin cardboard, typically slightly less than .01 inches thick. A number of different formats were used over time, but the most popular by far was IBM's format, introduced in 1928: they were 7-3⁄8 by 3-1⁄4 inches in size, with rectangular holes in 80 columns of 12 rows.

A card could hold up to 80 alphanumeric characters, one per column: numbers were indicated by a single punch in rows 1-10; letters were indicated by a punch in row 10/11/12, plus a punch in rows 1-9. Cards could also hold binary data, with more than two holes per column; by convention, a 7 and 9 punch in the first column indicated that the rest of the card held binary data.

In the pre-electronic era brushes were used to sense the presence or absence of a hole; later on, optical sensors were common.