Input/Output — Set 7

Correct Answer: B. Light Pen

• **Light Pen** = a pen-shaped, light-sensitive input device held directly against the monitor screen to select or draw; it detects the electron beam's position as the screen refreshes, translating it into screen coordinates that the computer reads as input. • **Detection method** — the pen contains a photocell that senses the brief flash of light from the CRT beam passing behind the screen surface, making it one of the earliest real-time direct-pointing tools. • Light pens were widely used in 1970s–80s CAD systems and airline reservation terminals before mice and touchscreens became common. • 💡 Option A (Mouse) is wrong because a mouse is a flat, palm-sized device moved across a surface, not held like a rod; Option C (Joystick) is wrong because a joystick controls directional movement in games, not point-and-draw on a screen; Option D (Stylus) is wrong because a stylus works on a touch-sensitive digitiser pad, not by sensing light from the monitor's own beam.

Correct Answer: B. Plotter

• **Plotter** = an output device that moves a pen (or inkjet head) along precise X-Y axes to draw vector graphics on paper; unlike raster printers, it traces continuous lines rather than printing dot patterns, making it ideal for architectural blueprints and technical diagrams. • **Paper size advantage** — plotters routinely handle A0 and custom-roll paper widths exceeding one metre, which is far beyond what any standard laser or inkjet printer supports. • Flat-bed and drum-type plotters are the two main variants; drum plotters roll the paper while the pen moves horizontally, enabling virtually unlimited paper length. • 💡 Option A (Laser Printer) is wrong because laser printers produce raster output on standard A4/A3 sheets and cannot handle the large vector formats needed for engineering plans; Option C (Monitor) is wrong because a monitor is a display device, not an output device that produces physical drawings; Option D (Scanner) is wrong because a scanner is an input device that captures existing images rather than producing new ones.

Correct Answer: A. Magnetic Stripe Reader

• **Magnetic Stripe Reader** = a device with a read head that detects the flux reversals encoded in iron-oxide particles on the card's magnetic stripe; as the card is swiped, it reads three tracks of data including account number, cardholder name, and expiry date. • **Security layer** — the stripe stores data at up to 75 characters per inch on Track 1 and 2, and this information is instantly transmitted to banking software for real-time transaction authorisation at ATMs and POS terminals. • Magnetic stripe technology dates to the 1960s IBM research project; modern cards also carry EMV chips as a more secure backup, but the stripe remains for backward compatibility. • 💡 Option B (OCR) is wrong because Optical Character Recognition reads printed text using light reflection, not magnetic fields on a card; Option C (MICR) is wrong because Magnetic Ink Character Recognition reads the special iron-oxide-ink numbers printed on bank cheques, not the stripe on a card; Option D (OMR) is wrong because Optical Mark Recognition detects pencil/pen marks on answer sheets, not encoded magnetic data.

Correct Answer: B. Speakers

• **Speakers** = electro-acoustic transducers that receive the amplified electrical audio signal from the sound card and convert it into physical vibrations via an electromagnetic voice coil, which moves a cone to produce the pressure waves we hear as sound. • **Transduction principle** — the voice coil sits inside a permanent magnet; alternating current from the audio signal creates a fluctuating magnetic force that pushes and pulls the cone at exactly the frequency of the original sound wave, reproducing pitch and timbre. • Computer speakers range from tiny 1-watt desktop units to large 2.1/5.1 surround systems, and quality is measured by frequency response (typically 20 Hz – 20 kHz for human hearing). • 💡 Option A (Microphone) is wrong because a microphone does the opposite — it converts sound waves into electrical signals, making it an input device; Option C (Keyboard) is wrong because a keyboard is a text-input device with no role in audio output; Option D (Scanner) is wrong because a scanner captures images optically and has nothing to do with audio conversion.

Correct Answer: B. Facial Recognition Camera

• **Facial Recognition Camera** = a specialised input device that uses depth sensors or structured infrared light to create a 3-D map of the face's unique bone structure and contour geometry, then compares it against a stored template to authenticate the user. • **Infrared advantage** — high-end implementations (e.g., Apple Face ID) project 30,000 invisible infrared dots onto the face and read their distortion pattern, making it impossible to spoof with a photograph because a flat image does not produce the correct depth map. • Facial recognition cameras are also deployed at border control, airport boarding gates, and smart surveillance systems where real-time 1:N matching (one face against many records) is required. • 💡 Option A (Fingerprint Scanner) is wrong because it reads the ridge pattern on a fingertip using capacitive or optical sensors, not the facial geometry; Option C (Iris Scanner) is wrong because it uses near-infrared light to photograph the unique texture of the iris of the eye, not the face as a whole; Option D (Touchpad) is wrong because a touchpad is a pressure/capacitive surface for cursor control and has no biometric sensing capability.

Correct Answer: B. Tab

• **Tab key** = a keyboard key originally borrowed from typewriters that moves the cursor to the next preset horizontal tab stop, typically set at every 0.5 inch or every 4–8 character spaces; pressing it at the start of a paragraph indents the first line in one keystroke. • **Multi-purpose function** — in modern computing, Tab serves beyond indentation: it cycles focus between form fields in browsers, triggers code auto-completion in IDEs, switches between open apps when combined with Alt (Alt+Tab), and inserts a tab character (ASCII 9) in plain-text editors. • The original mechanical typewriter had metal tab stops on a rail that the carriage physically jumped to; word processors digitalised this as adjustable ruler stops. • 💡 Option A (Shift) is wrong because Shift temporarily activates uppercase letters or the upper symbol on dual-character keys, not indentation; Option C (Alt) is wrong because Alt is a modifier key used in keyboard shortcuts like Alt+F4 and does not indent text on its own; Option D (Ctrl) is wrong because Ctrl is another modifier key for commands such as Ctrl+C (copy) and does not move the cursor to an indent stop.

Correct Answer: A. Scanner

• **Scanner** = an input device that shines a cold-cathode fluorescent lamp or LED array across a document and uses a CCD or CIS sensor strip to capture the reflected light at each point, converting it into a matrix of pixel colour values stored as a digital image file. • **Resolution measurement** — scanner quality is rated in DPI (dots per inch); a flatbed scanner at 300 DPI is sufficient for document OCR, while 1200+ DPI models preserve fine photographic grain for archival use. • Modern scanners also function as the copy engine inside all-in-one printers, and some handheld wand scanners can digitise a book page in seconds by dragging them across the text. • 💡 Option B (Printer) is wrong because a printer is an output device that transfers digital data onto physical paper, which is the reverse process; Option C (Monitor) is wrong because a monitor displays digital content visually but does not capture or ingest physical images; Option D (Speaker) is wrong because a speaker converts digital audio signals to sound and has nothing to do with image digitisation.

Correct Answer: B. Touch Screen

• **Touch Screen** = a dual-function device that combines a visual display (output) with a capacitive or resistive sensor layer (input), allowing the screen to detect the location and pressure of finger touches and report them as coordinate data to the software. • **Why it is classified as both** — the LCD/OLED panel beneath continuously outputs images and menus while the transparent touch overlay simultaneously reads user gestures, making a single piece of hardware serve both I/O roles without any separate pointing device. • Touch screens in public kiosks (ATMs, railway ticket machines, airport check-in counters) reduce the risk of mechanical failures from physical keyboards and allow dynamic on-screen layouts that change between tasks. • 💡 Option A (Mouse) is wrong because a mouse is purely an input device with no display or output capability; Option C (Keyboard) is wrong because a keyboard only sends key-press signals to the computer and produces no visual or audio output of its own; Option D (Printer) is wrong because a printer is purely an output device that receives data and prints it — it takes no input from the user in real time.

Correct Answer: B. PPM

• **PPM (Pages Per Minute)** = the standard industry benchmark that measures printer throughput by counting how many A4/Letter-size pages are printed in 60 seconds under normal operating conditions; manufacturers publish separate PPM figures for black-and-white and colour modes. • **Practical context** — a typical home inkjet printer achieves 8–15 PPM in black-and-white, while a fast office laser printer can exceed 50 PPM; high-speed production printers used by banks for statements can surpass 200 PPM. • PPM is tested under ISO/IEC 24734 standards to ensure comparable figures across brands; real-world speed is often lower due to first-page warm-up time and complex graphics. • 💡 Option A (DPI) is wrong because DPI (Dots Per Inch) measures print resolution — the sharpness of output — not the speed at which pages are produced; Option C (Baud) is wrong because Baud measures the number of signal changes per second in data communication, completely unrelated to printing; Option D (Hz) is wrong because Hertz measures frequency of cycles per second, used for processor speed or electrical current, not printer throughput.

Correct Answer: B. Optical Mouse

• **Optical Mouse** = an input device that contains a miniature CMOS image sensor and an LED (or laser) which together illuminate the surface and capture thousands of micro-photographs per second; a DSP chip compares consecutive frames to calculate the direction and speed of movement, translating it into cursor displacement. • **Advantage over mechanical** — older ball mice relied on a rubber ball rolling against two orthogonal rollers that could collect dust and slip; the optical mouse has no moving parts on its underside, so it never needs cleaning and works reliably on most flat surfaces. • High-end optical mice sample at up to 8,000 frames per second and offer adjustable DPI (sensitivity) settings, making them essential for precision tasks like graphic design and competitive gaming. • 💡 Option A (Mechanical Mouse) is wrong because it uses a rubber ball and physical rollers to detect movement, not a camera or light sensor; Option C (Scanner) is wrong because a scanner captures static images of documents placed on its glass surface and is not a pointing device; Option D (Webcam) is wrong because a webcam is a camera used for video capture and conferencing, not for tracking surface movement as a cursor-control input device.