Input and output devices
Devices for entering data (including direct data entry devices) and devices for outputting results, with their uses, advantages and disadvantages.
📌 Key points
- Manual input devices include the keyboard, numeric keypad, mouse, touchpad, trackerball, remote control, joystick, driving wheel, touch screen, scanner, digital camera, microphone and light pen.
- Direct data entry (DDE) devices read data straight into the computer without typing: magnetic stripe reader, chip and PIN reader, RFID reader, OMR, OCR, barcode reader and QR code scanner. DDE is faster and more accurate than typing.
- OMR (optical mark recognition) reads marks made in set positions on a form, e.g. multiple-choice answer sheets and lottery tickets; OCR (optical character recognition) turns an image of text into editable text, e.g. scanned documents and number plates.
- RFID uses radio waves to read data from tags at a distance, without needing line of sight, so many tags can be read at once, e.g. stock tracking, passports, pet chips and contactless cards.
- Chip and PIN cards are more secure than magnetic stripe cards because the chip is hard to copy and a PIN is needed; contactless payment is fast but has a spending limit for each transaction.
- Sensors (temperature, light, pressure, moisture, humidity, pH, gas, infrared/motion) send analogue data, so an ADC is needed; they are used in monitoring and control systems.
- Output devices include monitors (LCD, LED), touch screens, multimedia projectors, printers, speakers, headphones and actuators (e.g. motors, buzzers, heaters and lights in control systems).
- Laser printers are fast and cheap per page for large print runs; inkjet printers are cheap to buy and give high-quality photos but are slower and ink is expensive; dot matrix printers are noisy impact printers that can print multi-part (carbon copy) forms and work in dirty or damp places.
- 3D printers build solid objects layer by layer from a design file, e.g. prototypes, prosthetic limbs and spare parts.
📖 Key terms
- Direct data entry (DDE)
- Entering data directly into a computer without using a keyboard.
- OMR
- Optical mark recognition: reads marks made in set positions on a form.
- OCR
- Optical character recognition: converts an image of text into editable text.
- RFID
- Radio frequency identification: reads data from a tag using radio waves.
- Actuator
- An output device that causes movement or a physical change, e.g. a motor.
- 3D printer
- A printer that builds a solid object layer by layer.
✏️ Worked example
A school wants to mark 600 multiple-choice exam papers quickly. Explain which input method should be used and why.
- Students shade boxes on a printed answer sheet.
- An OMR reader detects the position of each mark on the sheet.
- The answers are compared with the correct answers and scores are calculated automatically.
- This is much faster than marking by hand and avoids typing errors, because no data is entered manually.
Make the device fit the scenario: read the question for clues such as "large volume", "noisy factory", "photographs", "from a distance". Generic answers like "it is fast" rarely score; say why it is fast in that situation.
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