Punch Card

Punched cards have been around for far longer than computers have. The earliest form that I am aware of is the Jacquard Machine (circa 1800) to control a loom. Charles Babbage incorporated the idea into his Analytical Engine (circa 1837). Herman Hollerith designed tabulating machines around the concept and saved the 1890 US Census. His design and company evolved to become the IBM Corporation. This is the card of which I speak…

Here is an example of a blank punch card used by IBM devices.

A blank punch card

And here is one with content punched.


The card holds 80 characters of information coded from right to left. The top can also have printed information which the computer does not see. The card is arranged into an 12X80 array with the 12 rows corresponding to an encoding scheme. Each character is represented as holes punched in the rows within a column. The encoding scheme is called Hollerith code.

The rows have an unusual naming scheme with the top two being 12 and 11. These are also called the zone rows and indicate which block a character belongs to. For example alphabetic or numeric. The remaining 10 rows are 0 through 9 indicating the place of the character within the code block. More details are available at The Virtual Keypunch, a site where you can actually get bespoke virtual card images punched.

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