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Punched card

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A punched card is a stiff piece of paper used to store digital information. It works by using holes in very specific spots. The presence or absence of these holes tells a machine what to do.

Punched card program deck.agr
Punched card program deck.agr

For a long time, these cards were the main way to give instructions to computers. They were used to store both data and the programs that run them. Even though we use different tools now, these cards were a huge part of how technology grew. They helped organize information for governments and big businesses all over the world.

How these cards work is quite clever. A machine reads the card by looking at where the holes are located. In some systems, the holes allow levers to move or electrical signals to pass through.

Hollerith punched card
Hollerith punched card

A group of these cards is often called a deck. Each card in the deck might hold a small piece of a larger puzzle. Some cards are called master cards because they hold important starting info. Other cards are called detail cards that provide more specific facts. This step-by-step reading allowed machines to sort and count huge amounts of information very quickly.

The history of these cards began long before modern computers existed. In 1725, Basile Bouchon used paper tape with holes to control a weaving loom. Later, in 1804, Joseph Marie Jacquard made this better with a chain of cards.

DMM 29263ab Jacquardwebstuhl
DMM 29263ab Jacquardwebstuhl

These cards told the loom which threads to lift to make patterns. In 1881, Jules Carpentier even used them to record and play music on a harmonium. This showed that holes in paper could represent much more than just patterns for cloth.

In the late 1800s, Herman Hollerith changed everything for data processing. He created a method using punched cards for the 1890 U.S. census.

Keypunch operator 1950 census IBM 016
Keypunch operator 1950 census IBM 016

His machines could read the holes to summarize information. Hollerith started the Tabulating Machine Company, which later became part of IBM. By 1937, IBM was making millions of cards every single day in New York. These cards were so trusted that they were even used for legal documents like government checks.

Even though punched cards are mostly obsolete now, they left a lasting mark. In the 1960s, magnetic tape began to take their place for storing data.

Tambor para Punch Card - Photo 3165102
Tambor para Punch Card - Photo 3165102

However, the way we use computers today still remembers them. For example, many computer screens still show 80 columns of text. This is a standard that comes directly from the old 80-column punched card format. The legacy of these simple paper cards lives on in the code we write today.

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🖼️ Images & Media (25)
File:Used Punchcard (5151286161).jpg
Used Punchcard (5151286161).jpg
File:Tambor_para_Punch_Card_-_Photo_3165102.JPG
Tambor_para_Punch_Card_-_Photo_3165102.JPG
File:DMM 29263ab Jacquardwebstuhl.jpg
DMM 29263ab Jacquardwebstuhl.jpg
File:This is a card puncher, an integral part of the tabulation system used by the United States Census Bureau to compile... - NARA - 513295.jpg
This is a card puncher, an integral part...
File:Keypunch operator 1950 census IBM 016.jpg
Keypunch operator 1950 census IBM 016.jpg
File:Punched card program deck.agr.jpg
Punched card program deck.agr.jpg
File:Hollerith punched card.jpg
Hollerith punched card.jpg
File:FortranCardPROJ039.agr.jpg
FortranCardPROJ039.agr.jpg
File:Blue-punch-card-front-horiz.png
Blue-punch-card-front-horiz.png
File:IBM1130CopyCard.agr.jpg
IBM1130CopyCard.agr.jpg
File:IBM lace card.jpg
IBM lace card.jpg
File:Punch-card-5081.jpg
Punch-card-5081.jpg

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