1.5 · Input / Output Devices
Goal: classify common I/O devices and pick the best one for a context.
Input vs output vs both
| Direction | Examples |
|---|---|
| Input | Keyboard, mouse, scanner, microphone, camera, sensors, barcode scanner, OMR sheet reader |
| Output | Monitor, printer, speaker, plotter, projector |
| Both | Touchscreen, network card, multifunction printer |
Input devices in detail
| Device | Used for | Typical scenario |
|---|---|---|
| Keyboard | Text input | General use |
| Mouse / trackpad | Pointing | Desktop / laptop |
| Scanner | Convert paper to image | Office, library digitisation |
| Microphone | Audio capture | Voice messages, podcasts |
| Camera (still / video) | Image / video capture | Photography, conferencing |
| Touchscreen | Direct manipulation | Smartphones, tablets, kiosks |
| Barcode scanner | Decode 1D barcodes | Supermarket POS, library |
| QR scanner | Decode 2D codes | Mobile payments, Octopus QR |
| OMR reader | Read pencil marks | Exam multiple-choice sheets |
| OCR software + scanner | Convert image text → editable | Digitising books |
| MICR reader | Magnetic ink chars | Cheque processing |
| Sensors | Capture environment | Temperature, light, accelerometer, GPS |
Output devices in detail
| Device | Used for | Typical scenario |
|---|---|---|
| Monitor / display | Visual output | Everything |
| Speaker / headphones | Audio output | Music, voice |
| Inkjet printer | Colour photos / small office | Home |
| Laser printer | Fast text printing | Office, school |
| 3D printer | Physical object output | Prototype, prosthetics |
| Plotter | Large engineering drawings | CAD, posters |
| Projector | Large group display | Classroom, theatre |
Pick the right device — rubric
When the exam gives you a scenario, ask:
- Type of data: text, image, audio, video, physical object?
- Volume: occasional or high-volume?
- Quality required: rough or fine detail?
- Cost: home or enterprise budget?
- Special needs: accessibility, mobility, security?
Worked example · Library
| Task | Device |
|---|---|
| Borrow check-in | Barcode scanner (input) |
| Issue printed receipt | Thermal printer (output) |
| Member self-service kiosk | Touchscreen (both) |
| Scan old reference books | Flatbed scanner + OCR |
| Display today's events | Wall-mounted monitor |
Accessibility considerations
- Screen reader + Braille display for blind users.
- Voice input (Dragon NaturallySpeaking, OS dictation) for motor-impaired users.
- High-contrast monitors, on-screen magnifiers for low vision.
- Captioned audio output for deaf users.
Modern trends
- Voice assistants (Siri, Alexa) — microphone in, speaker out.
- AR/VR headsets — combined I/O.
- Brain-computer interfaces — early stage but growing.
- Sensors everywhere (smart-home, fitness wearables, autonomous vehicles).
Common student mistakes
- Listing a touchscreen only as output.
- Confusing scanner (digital image of paper) with OCR (image converted to editable text).
- Forgetting that a network card is also an I/O device.
- Treating speaker and headphone as different exam answers — they're both audio output devices.
Exam-style question
Q (4 marks): For each of the following scenarios, recommend a suitable input or output device and justify your choice: (a) A supermarket cashier processing customer purchases. (b) A blind student attending an online lecture. (c) A teacher conducting a Geography lesson in a 60-student lecture hall. (d) A scientist printing a small 3D model of a molecule.
Sample answer:
(a) Barcode scanner — fast, accurate reading of product codes without typing, suitable for high-volume retail transactions.
(b) Screen reader software with headphones as output — converts text on the screen into speech the student can follow, supports accessibility.
(c) Projector — projects the lesson slides onto a large screen visible to all 60 students; supports both visual and animation content.
(d) 3D printer — outputs a physical, tangible model of the molecule for hands-on study.
Key takeaways
- Know the classification: input, output, both.
- Match the device to the data type and volume.
- Don't forget accessibility options.
➡️ Next chapter: 2 · System Software