Which device can both input and output information?

A touchscreen is a device that serves both input and output functions. It allows users to interact with a computer system directly by touching the display, which registers the input. This includes gestures like tapping, swiping, and pressing, making it a versatile tool for user interaction. At the same time, a touchscreen displays visual output to the user, such as images, videos, and application interfaces.

In contrast, monitors and speakers primarily serve to provide output; monitors display visual information, while speakers emit sound. A printer is also solely an output device, as it produces a physical copy of digital documents but does not take input in terms of user interaction like a touchscreen does. This dual functionality of touchscreens makes them unique among the options listed, allowing for a more interactive experience in various applications, such as smartphones, tablets, and kiosks.