What is the difference between an input and output device?

An input device sends information to a computer system for processing, and an output device reproduces or displays the results of that processing. Input devices only allow for input of data to a computer and output devices only receive the output of data from another device.

Most devices are only input devices or output devices, as they can only accept data input from a user or output data generated by a computer. However, some devices can accept input and display output, and they are called I/O devices (input/output devices).

For example, as shown in the top half of the image, a keyboard sends electrical signals, which are received as input. Those signals are then interpreted by the computer and displayed, or output, on the monitor as text or images. In the lower half of the image, the computer sends, or outputs, data to a printer. Then, that data is printed onto a piece of paper, which is also considered output.

Input devices

An input device can send data to another device, but it cannot receive data from another device. Examples of input devices include the following.

• Keyboard and Mouse - Accepts input from a user and sends that data (input) to the computer. They cannot accept or reproduce information (output) from the computer.
• Microphone - Receives sound generated by an input source, and sends that sound to a computer.
• Webcam - Receives images generated by whatever it is pointed at (input) and sends those images to a computer.

Output devices

An output device can receive data from another device and generate output with that data, but it cannot send data to another device. Examples of output devices include the following.

• Monitor - Receives data from a computer (output) and displays that information as text and images for users to view. It cannot accept data from a user and send that data to another device.
• Projector - Receives data from a computer (output) and displays, or projects, that information as text and images onto a surface, like a wall or screen. It cannot accept data from a user and send that data to another device.
• Speakers - Receives sound data from a computer and plays the sounds for users to hear. It cannot accept sound generated by users and send that sound to another device.

Input/output devices

An input/output device can receive data from users, or another device (input), and send data to another device (output). Examples of input/output devices include the following.

• CD-RW drive and DVD-RW drive - Receives data from a computer (input), to copy onto a writable CD (compact disc) or DVD (digital versatile disc). Also, the drive sends data on a CD or DVD (output) to a computer.
• USB flash drive - Receives, or saves, data from a computer (input). Also, the drive sends data to a computer or another device (output).