Keypunch

A keypunch, also known as a card punch, is a device used to input data into a computer system by punching holes in paper cards. This was a primary method of data entry for computers from the late 19th century through the mid-1970s, and in some applications, into the 1980s.

The operator would type data on a keyboard, and the keypunch would then physically punch holes in a pre-defined pattern on the card, representing the characters or instructions. Each column on the card typically represented one character. The most common card format used was the 80-column card.

The punched cards would then be fed into a card reader, which would interpret the patterns of holes and convert them into electronic signals for the computer to process. This process allowed for the efficient storage and transfer of large amounts of data, although it was a relatively slow and error-prone process compared to modern data entry methods.

Keypunches could also be used to reproduce cards (gangpunching) or verify the accuracy of previously punched cards (verifying). A verifying machine compared the operator's input with the holes already punched on the card and flagged any discrepancies.

The advent of magnetic tape, disk storage, and interactive terminals gradually replaced keypunches as the primary method of data entry. While now largely obsolete, the keypunch played a crucial role in the development of computing and data processing.