A punch card (also known as Hollerith cards, IBM cardsor and punched card) were widely used through much of the 20th century (1900’s) in what became known as the data processing industry. It is a stiff piece of paper that contains digital information and is an early method of data storage used with early computers. This information is represented by the presence or absence of holes in predefined positions. The information could be data for data processing applications or used to directly control automated machinery including the Pianola. The cards contain a number of punched holes that were punched by hand or machine to represent data. These cards allowed companies to store and access information by entering the card into the computer.
The idea of the punch card was first developed by Basile Bouchon to control a textile loom in 1725. The design was improved by his assistant Jean-Baptiste Falcon and Jacques Vaucanson in 1740. Further developments were made in 1890, by Herman Hollerith who developed a method for machines to record and store information to be used for the US census. Herman Hollerith later formed the company IBM.
Early computers could not store files like today’s computers as they had no memory. If you wanted to create a data file or a program the only way to use that data with other computers was to use a punch card. Whilst punch cards were the primary method of storing and retrieving data in the 20th century (1900s), after magnetic media was created in the 1960’s and began to be cheaper, punch cards stopped being used. They are very rarely used or found today.
Using a punch card machine, data can be entered into the card by punching holes on each column to represent one character.
Once a card has been completed or the return key has been pressed the card technically “stores” that information. Because each card could only hold so much data if you wrote a program using punch cards (one card for each line of code) you would have a stack of punch cards that needed to remain in order. The punch card above would have been the last card in a sequence and was used to instruct the computer to end the program.
To load the program or read a punch card data, each card is inserted into a punch card reader that input the data from the card into a computer. As the card is inserted, the punch card reader starts on the left-top-side of the card and reads vertically starting at the top and moving down. After the card reader has read a column it moves to the next column.
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