Input and output devices
Common devices, direct data entry, and how to justify a choice.
Review these first
Learning objectives
What you need to be able to do
Teacher-mapped phrasing — check against the official Cambridge syllabus for exact wording.
- 2.1.1Identify input and output devices and describe their uses.
- 2.1.2Justify the choice of device for a given application, including direct data entry.
5 minute read
Input and output devices
Input devices
Devices that put data into the system: keyboard, mouse, touchpad, scanner, digital camera, microphone, sensors, and direct data entry devices. Direct data entry (DDE) devices read data automatically without typing, which makes them fast and accurate:
- Barcode reader — supermarket checkouts and stock control.
- OMR (optical mark reader) — reads pencil marks on multiple-choice answer sheets and questionnaires.
- OCR (optical character recognition) — converts printed or written text into editable text.
- MICR (magnetic ink character recognition) — reads the numbers on the bottom of cheques; very hard to forge.
- RFID — contactless tags for stock, passports and payment cards.
Sensors input physical data continuously: temperature, pressure, light, motion, humidity, pH. They are essential in monitoring and control systems.
Output devices
Devices that present results: monitor, printer (laser for speed and volume, inkjet for low-cost colour photos, 3D for prototypes), speakers, projectors, and actuators such as motors and buzzers in control systems.
Justifying a choice
This is where marks are won. Never just name the device — say why it suits the situation:
- Barcode reader at a checkout: fast and fewer errors than typing a product code.
- Touchscreen at an information kiosk: intuitive, needs no separate keyboard, robust in public use.
- Laser printer in an office: fast, high volume, low cost per page.
Think of it like this
Choosing an input device is like choosing a tool to open a bottle. A screwdriver might eventually work, but the question is never "can it?" — it is "which is fastest, most accurate, and suited to who is using it?"
Worked examples
Method, step by step
A supermarket wants to record which items customers buy at the checkout. Name a suitable input device and justify your choice.
- 1The items already carry printed barcodes, so a barcode reader can read them directly.
- 2Reading is much faster than typing a product code by hand.
- 3It also avoids typing errors, so stock records and prices stay accurate.
A barcode reader — it reads the existing barcode automatically, which is far faster than keying in codes and greatly reduces data entry errors.
Common misconceptions
- Thinking a touchscreen is only an input device. It is **both** input and output, which is exactly why it is used where space is limited.
- Confusing OMR and OCR. OMR reads the *position* of marks; OCR recognises the *shapes* of characters as text.
- Naming a device without justification. Exam marks for device questions are almost always for the reason, not the name.
In the exam
- Answer "give a suitable device and justify your choice" in two parts: the device, then at least two reasons tied to that specific scenario (speed, accuracy, cost, durability, ease of use).
- For sensor questions, name the specific sensor type — "temperature sensor", not just "a sensor".