Input & Output Devices

• Input devices let a user (or the environment) get data INTO the computer system — e.g. keyboard, mouse, scanner, microphone, touch screen.
• Output devices take processed data OUT of the computer and present it in a form a human can understand — e.g. printer, screen, speaker, actuator.
• Sensors are a special category of input device — they measure a physical property (light, temperature, sound, etc.) rather than waiting for a person to press a button.
• Sensors feed into monitoring systems (just watch and report/warn) or control systems (actually take action, e.g. switch on a heater).
• A feedback loop is when a system's output becomes its next input, creating a self-correcting cycle (e.g. thermostat).
• When choosing the "right" device for a scenario, always weigh up: user needs, user skills, environment, and cost.

An input device is any piece of hardware that lets a user (or the surrounding environment) put data or commands into a computer system. Think of the computer as a locked room — nothing that happens inside it matters unless something outside can pass a message through the door. Input devices are that door.

The computer then processes whatever comes in through the input device, and eventually sends something back out through an output device. That's the whole input → process → output cycle in one sentence.

The main input devices you must know