Punched_Card
A Punched_Card or punch card, also known as a Hollerith card, is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions. Here's an in-depth look at this historical data storage medium:
History
The concept of the punched card can be traced back to the early 19th century:
- 1804: Joseph Marie Jacquard used punched cards to control looms, allowing for the automation of weaving intricate patterns. This was an early example of using punched cards for machine control.
- 1890: Herman Hollerith, an American inventor, developed a system using punched cards for tabulating data for the US Census. His invention significantly reduced the time required to process census data.
- 1920s-1960s: Punched cards became the primary medium for data processing, used extensively by businesses and governments for a variety of data management tasks.
Structure and Function
A standard Punched_Card typically had:
- Dimensions: Typically 7-3/8 inches by 3-1/4 inches (187.325 mm by 82.55 mm).
- Columns: 80 columns, each capable of holding one character of data, though some variations existed.
- Rows: 12 rows for each column, where holes could be punched.
Cards were punched using machines like keypunch machines or later, card punches. Information was encoded by punching holes in specific patterns or codes:
- IBM Card Code: IBM developed a coding system where different combinations of holes represented different characters or digits.
- BCD (Binary Coded Decimal): A binary representation where each column could represent a binary number or character.
Applications
- Data Processing: Used for storing and processing data in early computer systems and business applications.
- Voting Systems: Punch cards were used in some voting machines, notably leading to issues in the 2000 US Presidential Election due to hanging chads.
- Control Systems: Beyond data storage, cards were used to control machinery, like Jacquard looms or early computing devices.
Decline
The use of punched cards started to decline with the advent of:
- Magnetic Tape: Introduced in the 1950s, offering higher storage capacity and reusability.
- Magnetic Disks: Provided even faster access to data.
- Optical Storage: CDs, DVDs, and later flash storage made punched cards obsolete.
Legacy
The legacy of the Punched_Card can be seen in:
- Many early programming languages were developed with punched card systems in mind.
- The term "card" in computing, like "card reader" or "card punch," is a vestige from this era.
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