Computer Punched Card

Computer punched cards were a popular data storage and input medium in early computer systems. Punched cards were widely used from the 1920s through the 1970s and played a significant role in the development of computing.

Computer punched cards were made of stiff cardstock and had rectangular holes punched in specific positions. These holes represented data and instructions that could be processed by machines called card readers or tabulating machines.

The most common type of computer punched card had dimensions of 7.375 inches by 3.25 inches (187.33 mm by 82.55 mm) and featured 80 columns and typically 12 rows of holes. Each column could hold a character or a specific piece of information. The absence or presence of a hole in a particular column indicated specific data or instructions.

Programs, data, and instructions were encoded onto the punched cards using keypunch machines. Operators would use the keypunch machines to punch holes in the appropriate columns and rows to represent the desired information.

Computer punched cards were used for various purposes, including data entry, data storage, and batch processing. They allowed for the input and storage of large amounts of data, such as census information, scientific data, business records, and more. Programs and instructions were also stored on punched cards, allowing for sequential execution in batch processing systems.

As technology advanced, punched cards were gradually replaced by more efficient and versatile storage and input methods, such as magnetic tape, magnetic disk, and eventually electronic storage. Today, punched cards are considered obsolete, and their usage has been largely phased out in favor of modern computer systems and storage media.

Here is a comprehensive review of various computer punched card encoding / decoding schemes.

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