What category do light pens belong to?

Light pens are categorized as input devices because they are used to interact with a computer by allowing the user to point at or select items displayed on a screen. They function by detecting light emitted from the screen, enabling users to draw or select items directly on the display. This capability to provide data or commands to the computer system is what classifies them as input devices.

In contrast, output devices are designed to convey information from the computer to the user, such as monitors or printers, which serve entirely different functions. The category of both input and output devices would refer to devices that can perform both tasks, like a touchscreen, which is not applicable to light pens, as they solely provide input. Thus, considering the functionality and intended use of a light pen, it is correctly classified as an input device.