Reikäkorttilukijoilla

Reikäkorttilukijoilla, known in English as punch card readers, are electromechanical or electronic devices used to read data stored on punch cards. These cards were an early form of data storage and input, popular from the mid-19th century until the late 20th century.

A punch card reader operates by passing a punch card through a mechanism that detects the presence or absence of holes in specific locations. Historically, this detection was often achieved using mechanical pins that would pass through holes, completing an electrical circuit. For blank spaces, the pins would be obstructed, and no circuit would be completed. Early readers were slow, processing only a few hundred cards per minute.

As technology advanced, optical punch card readers emerged. These devices used light beams. A light source on one side of the card would shine through the holes, and photocells on the other side would detect the light. This allowed for significantly faster reading speeds compared to their mechanical predecessors.

Punch card readers played a crucial role in the development of computing and data processing. They were used in businesses for tasks like payroll, inventory management, and statistical analysis, as well as in early mainframe computers for program input and data entry. The introduction of magnetic storage and then more advanced input methods led to their eventual obsolescence.