Hardware, Memory & Number Systems

high importance7 formulas⚡ 14 shortcuts6 subtopics

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Subtopic 4 of 6·← Number systems: binary, octal, decimal, hexadecimal·Ports and connectors →

Input and output devices

Input devices feed data to the CPU: keyboard, mouse, trackball, joystick, light pen, touch screen, scanner, digital camera, webcam, microphone, barcode/QR reader, biometric (fingerprint/retina) scanner, stylus, and the classic readers:

Device	Reads	Used in
OMR (Optical Mark Recognition)	Pencil/ink marks (bubbles)	OMR answer sheets, surveys
OCR (Optical Character Recognition)	Printed/written characters into editable text	Digitising documents
MICR (Magnetic Ink Character Recognition)	Iron-oxide ink characters	Cheque processing (9-digit code)
Barcode reader	Parallel black-white bars	Shops, libraries

Output devices: monitor/VDU (CRT -> LCD/LED/OLED), printer, plotter, speaker, projector, headphone.

Printers: Impact (physical strike - Dot Matrix, Daisy Wheel; noisy, carbon-copy possible) vs Non-impact (no strike - Inkjet (sprays ink), Laser (electrophotographic, fast, office standard), Thermal (bills, ATMs)). Plotter draws large precise hard copies (engineering drawings).

Both input & output: touch screen, modem, network card, headsets with mic, and storage devices generally.

📖 Notes 🧩 4 question types 🎯 17 practice Q

Detailed notes

Input devices — data goes IN

Anything that feeds data or commands to the computer is an input device.

Group	Devices
Typing / pointing	Keyboard, mouse, trackball, touchpad, joystick, light pen, stylus
Capture	Scanner, digital camera, webcam, microphone
Readers	Barcode/QR reader (shops), OMR (answer sheets), OCR (scanned text), MICR (bank cheques), biometric scanner (fingerprint, iris)

The reader trio by one word each: OMR = Marks (pencil bubbles), OCR = Characters (printed text becomes editable text), MICR = Ink (magnetic characters on cheques).

Output devices — results come OUT

Device	Gives
Monitor	Soft copy — output you can see but not touch
Printer	Hard copy — output on paper
Speaker / headphones	Sound
Plotter	Hard copy of large drawings and maps (engineering, architecture)
Projector	A big soft copy on a screen

Printers: impact vs non-impact

Type	How it works	Examples
Impact	Physically strikes the paper through a ribbon	Dot matrix, daisy wheel — noisy, cheap, multi-copy forms
Non-impact	No hitting — sprays ink, fuses toner, or heats paper	Laser (toner, fast, office), inkjet (liquid ink, home), thermal (bills)

Devices that do BOTH

A touch screen takes your finger's input and displays output. A headset has a mic (in) and speakers (out). Exams ask 'which is both input and output?' — touch screen is the standard answer.

Pointing devices in one line each

Mouse — the standard pointing device; a ball or optical sensor tracks movement.
Trackball — an upside-down mouse: you roll the ball, the device stays put.
Touchpad — the laptop's flat mouse replacement.
Joystick — direction control for games and flight simulators.
Light pen / stylus — draw or point directly on the screen.
Touchpad + pointers all feed position data IN — every one is an input device.

Pairing questions (device ↔ use)

Device	Classic use in exams
Barcode reader	Supermarket billing
OMR	Evaluating pencil-bubble answer sheets
MICR	Reading the cheque code line in banks
OCR	Converting a scanned page into editable text
Biometric scanner	Attendance, Aadhaar-style identity checks
Plotter	Engineering drawings, maps, posters
Webcam + mic	Video calls

Modern extras

3D printer — builds a physical solid object layer by layer (an output device).
Webcam + microphone — the video-call input pair.

Quick revision

Input: keyboard, mouse, scanner, mic, camera, barcode/OMR/OCR/MICR readers, biometrics.
OMR = Marks, OCR = Characters, MICR = magnetic Ink (cheques).
Output: monitor (soft copy), printer/plotter (hard copy), speaker, projector.
Impact = hits paper (dot matrix); non-impact = laser, inkjet, thermal.
Touch screen = both input and output. 3D printer = solid object output.

Types of questions asked

Every way this subtopic shows up in exams — how to recognise it, the formula or logic to use, and a solved example.

Type 1: Input device identificationvery common4 practice Q

How to spot it:

'Which is an input device?', 'a barcode reader is used to…', 'joystick is used in…' — pick the device that feeds data in.

Test each option: does data flow INTO the computer (input) or OUT (output)?
Scanner, microphone and camera are input even though they feel like 'media' devices.
Monitor, printer, speaker, plotter, projector are always output.

Example: Which of the following is an input device?

Scanner — it feeds a paper document into the computer as an image. Monitor, speaker and plotter all send data out.

Type 2: Output device identification; soft vs hard copyvery common3 practice Q

How to spot it:

'Which is an output device?', 'printed output is called a … copy', 'monitor output is called a … copy'.

Soft copy = on screen (monitor, projector); hard copy = on paper (printer, plotter).
Speaker and headphones are output (sound).
'Touch screen' is the planted trap in output-only questions — it is both.

Example: Output shown on paper (a printout) is called a —

Hard copy — permanent, touchable output. Output on a monitor is a soft copy.

Type 3: Both input and output / odd one outcommon3 practice Q

How to spot it:

'Which device works as both input and output?', 'which is NOT an input device?' — one option breaks the family.

Both-direction devices: touch screen, headset (mic + speaker), fax machine (classic), smart TV with voice remote.
For 'not an input', look for the printer, monitor or speaker hiding in the list.
Classify each option before reading the stem twice — speed comes from the table.

Example: Which device acts as both an input and an output device?

Touch screen — your touch is input and the display is output. A mouse is input-only; a monitor is output-only.

Type 4: Printer technology and reader classificationcommon4 practice Q

How to spot it:

'Which is an impact printer?', 'laser printer is non-impact because…', 'OCR converts…', 'plotter is used for…', '3D printer makes…'.

Impact = physical strike (dot matrix, daisy wheel); non-impact = laser, inkjet, thermal.
Readers by one word: OMR marks, OCR characters, MICR magnetic ink.
Plotter = large-format drawings; 3D printer = solid objects layer by layer.

Example: Which of the following is an impact printer?

Dot matrix — its pins physically strike the ribbon against the paper. Laser, inkjet and thermal printers never touch the paper with force.

Shortcut tricks

⚡ Mark-Character-Ink

OMR = Marks (bubbles), OCR = Characters (text), MICR = Ink on cheques (banks). Marks, Characters, Ink - match the noun in the question.

Example: Bank cheque reading uses?

MICR - magnetic ink characters.

⚡ Impact = hit

If the printer physically hits paper (dot matrix, daisy wheel) it is impact - noisy but makes carbon copies. Inkjet/Laser/Thermal never touch with force: non-impact.

Example: Which is a non-impact printer - Dot Matrix or Laser?

Laser (dot matrix strikes the ribbon).

Where students lose marks

Marking a touch screen as input-only - it is both input and output.
Calling MICR an optical technology - it reads magnetic ink.
Saying plotters are for office documents - plotters are for large-format drawings/graphs.

Practice sets — 17 questions

Sets of 10, mixed across the question types above. Each answer comes with a step-by-step explanation.

Topic test · 10 questions

Suggested time 4 min · wrong answers go to your mistake notebook automatically.