Which device can function as both an input and output device?

The device that can function as both an input and output device is a keyboard, particularly in the context of modern technology like a keyboard with an integrated screen or LED signals indicating its functions. Traditionally, keyboards are primarily input devices because they allow users to enter data into a computer. However, some advanced keyboards include features that provide feedback to the user, such as backlit keys that can display different colors for different functions, or screens that show information.

This capability to both receive input (from the user typing) and provide output (by displaying information or signals) justifies the keyboard as a dual-function device. Understanding the roles of various devices in computing, especially how newer technologies have integrated features, is essential for grasping the evolution of input and output devices in technology.