Control card

This article is about an antiquated method of using punched cardboard to control the operation of computer hardware. For other uses of the term, please see the control card disambiguation page.

A control card was a specific type of punched card used to store processing instructions.

Some of the earliest large-scale computers used stacks of punched cards for storing data to be processed. These cards acted as memory for the machine.

In addition to data, however, all computers require a place and method for storing processing instructions. On a punch card system created for a specific use, the processing instruction set was integrated with the machine, ie. hard-wired. On a general use punch card system, however, the machine's resident monitor read processing instructions from special cards called control cards, which acted as controlling elements of the data processing operation.

Artificial intelligence implications

Control cards were part of the "brain" of a punch card computer. When computers gained the ability to use control cards, they acquired a necessary tool for being programmed. Many fiction and non-fiction authors have speculated that after control cards became available, the difference between human brains and computers became only a matter of data volume and processing speed.