I.6 Input & Output Devices and Their Types

⬆️ Back to: P-I.I. Introduction to Computing

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Page Outline — click a heading to jump. Detailed device notes are on I.7 Input Devices and I.8 Output Devices.

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Exam pattern (2016–2026): No direct question. The monitor-technology MCQ (2024 Q2) is answered on I.11 Types of Hardware.

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1. Classification Principle

• Test: which way does data flow relative to the computer?
  • Input: data flows into the computer.
  • Output: data flows out of the computer.
  • Both (I/O): data flows both ways.
• Conversion check:
  • Input: real-world form → digital.
  • Output: digital → human-usable form.

2. Types of Input

• Text: keyboard.
• Pointing: mouse, joystick, touchpad.
• Image/optical: scanner, digital camera, barcode reader.
• Audio/video: microphone, webcam.
• Direct capture: touchscreen.

3. Types of Output

• Visual: monitor, projector.
• Hard copy: printer, plotter.
• Audio: speaker, headphones.

4. Devices That Are Both

4.1 Touchscreen

• Input: sensor layer reads finger position (resistive or capacitive).
• Output: the same panel shows the image.
• Used in: phones, tablets, ATMs, POS terminals.
• Downside: less precise than a mouse; smudges and wears.

4.2 Modem (Modulator-Demodulator)

• Output side: modulates outgoing digital data into a line signal.
• Input side: demodulates incoming signals back to digital.
• Evolution: 56 kbps dial-up → DSL, cable, fibre (ONT) at hundreds of Mbps.

4.3 Network Interface Card (NIC)

• Wired (Ethernet) or wireless (Wi-Fi) adapter.
• Sends and receives packets.
• Each card has a unique 48-bit MAC address.

4.4 Storage drives

• HDD, SSD, USB drive: data is written (output) and read back (input).

5. Quick Classification Table

• Plotter vs printer: a plotter draws continuous lines from vector data (CAD, blueprints, maps); a printer builds the image from dots.
• CSS angle: Pakistan's shift from dial-up to 3G/4G and fibre (regulated by PTA) is, at device level, a change in how modems and NICs carry the same bits.

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6. ⚠️ MCQ Traps

• Touchscreen is both, not input-only.
• Modem is both, not input-only.
• Classify by data flow, not by memorising lists.

7. ✅ Self-Test Questions (with Answers)

Q1. State the principle used to tell input from output devices.

• Direction of data flow relative to the CPU and memory.
• Input brings data in; output sends results out; I/O does both.
• Ask: "does data enter, leave, or both?"

Q2. Give two devices that are both input and output.

• Touchscreen: senses touch (input) and displays (output).
• Modem: modulates out (output), demodulates in (input).
• Also: NIC.

Q3. Classify microphone, plotter, touchscreen, joystick.

• Microphone → input.
• Plotter → output.
• Touchscreen → both.
• Joystick → input (haptic one → both).