Communication between a user and a computer can only be carried out with the aid of input and output devices.
Computer input device is a hardware that gives data to a computer, it allows interaction between other computer components, it also gives the user ability to control the computer. The most common input devices are keyboard and mouse, others include scanner, joystick, webcam and microphone.
Computer output device is a hardware that sends out information from the computer. This include devices use to display information and devices use for production of information. Examples: monitor, projector, printers and speakers.
They are some devices that serve as both input and output devices, they are called input and output devices. Examples are modems, disk drives and network cards.
Input and output devices are relatively simple to define based on the words themselves. An input device would be something like a mouse or a keyboard that allows you to 'input' things, thoughts, or manipulations into the computer. By using these types of devices, you're telling the computer, phone, or tablet what you want it to do. Output devices would be those items that give or tell the user something.
Printers and monitors are both examples of output devices because the monitor outputs information to you allowing you to operate the computer. A printer outputs whatever printed material is needed. Many communication devices like modems and network cards perform both input and output functions.