Input and output devices
Input and output devices
- An input device sends data into the computer.
- An output device sends results out to the user.
- Knowing how each works (and which is which) is a common exam task.
Input devices
- Keyboard (sends a code per key), optical mouse (light + sensor tracks movement).
- Barcode/QR scanner (reads a pattern), digital camera (lens → sensor → pixels).
- Microphone (sound → electrical signal), sensors (measure a physical quantity).
- A touch screen is also an input device.
Practice
Which is an input device?
A scanner brings data in. Projectors, speakers and printers are output devices.
Practice
Sort these into input or output.
Microphones and sensors bring data in; speakers send sound out.
Touch screen types
- Resistive — two layers are pressed together where you touch.
- Capacitive — it senses the tiny electric charge of your finger (used in phones).
- Infrared — your finger breaks a grid of light beams.
Practice
A capacitive touch screen works by:
Capacitive screens detect the finger's charge (multi-touch, used in phones); resistive presses layers; infrared breaks beams.
Output devices
- LCD/LED screen and projector show images; speaker makes sound.
- Inkjet printer sprays ink drops; laser printer uses a laser + toner fixed by heat; 3D printer builds an object layer by layer.
- An actuator turns a signal into movement (a motor or valve).
Practice
An actuator is an output device that:
An actuator (motor, valve) converts a signal into physical movement.
Practice
A laser printer produces a page using:
Laser printers use toner fused by heat; inkjets spray ink; 3D printers build layers.
You've got it
Key idea
- input brings data in (keyboard, scanner, sensor, camera, mic, touch screen)
- touch screens: resistive (pressed layers), capacitive (finger charge), infrared (broken beams)
- output sends results out (screen, printer, speaker, actuator = movement)
- inkjet sprays ink; laser uses toner fixed by heat