Basic components of a computer system

The governing concept is the classification of computer peripherals as input or output devices. A joystick sends the player’s directional and movement commands into the computer, so option C is correct. A scanner captures documents, while a printer and speaker produce output. These devices do not normally provide continuous game-direction control. Therefore, a joystick is the suitable gaming input device.

The governing concept is input technology used for automatic identification. A barcode reader scans the pattern of bars and spaces printed on a product and converts it into digital data for the shop’s billing system. Thus, option D is correct. A webcam captures general images, a keyboard requires manual typing, and a projector displays information. None of these is specifically designed to decode retail barcodes.

The governing concept is optical recognition of marks rather than letters. Optical Mark Recognition, or OMR, scans an answer sheet and detects which circles or bubbles have been darkened, making option B correct. OCR is intended for printed or handwritten characters, MICR reads magnetic-ink characters on cheques, and barcode recognition reads bar-and-space patterns. Filled bubbles are the key clue for OMR.

The governing concept is converting a scanned image of writing into machine-readable characters. Optical Character Recognition, or OCR, analyses the shapes of printed letters and produces text that can be searched, copied, and edited, so option C is correct. OMR reads filled marks, MICR reads magnetic characters on cheques, and RFID identifies tagged objects using radio signals. Only OCR performs printed-text recognition.

The governing concept is display resolution, which describes how many pixels are arranged across the screen, commonly as width by height. A higher suitable resolution generally allows finer detail and a sharper image, so option A is correct. Volume concerns sound, storage capacity concerns saved data, and network speed concerns data transfer. None of those directly measures screen image detail.

The governing concept is print resolution. Dots per inch, abbreviated DPI, states how many individual ink or toner dots a printer can place within one inch. A higher DPI generally supports finer detail and sharper output, so option B is correct. Hertz measures frequency, a byte measures digital data, and a volt measures electric potential. These units do not directly describe printer resolution or print quality.

The governing concept is selecting an output device according to the size and precision of the work. A plotter is designed to create large-format, accurate line drawings such as maps, engineering plans, and architectural layouts, so option D is correct. Inkjet and laser printers are mainly intended for ordinary documents, while a scanner is an input device that captures existing paper images rather than printing new drawings.

An Uninterruptible Power Supply, or UPS, contains a battery and power-control circuitry that provide temporary electricity when the main supply fails. This short backup period allows the user to save files and shut down safely. A modem and router communicate over networks, while a scanner captures images or text; none is designed to provide computer power. Thus, option B is correct.

An expansion slot is a connector on the motherboard designed to receive an additional card. Examples include graphics, sound, and network cards, depending on the slot type and system design. A memory slot holds RAM, the processor socket holds the CPU, and a power button starts or controls the system rather than accepting a card. Therefore, option C is correct.

The input-process-output model explains the basic working cycle of a computer. First, an input device such as a keyboard supplies data; next, the CPU processes or calculates it; finally, an output device such as a monitor presents the result. Option A follows this order. The other choices assign impossible functions to monitors, mice, printers, keyboards, speakers, or scanners.

An input device sends data or commands into the computer. A keyboard enters text, a mouse supplies pointing and selection actions, and a microphone captures sound; all three are input devices. A monitor, printer, and speakers are output devices. Drives are storage devices, while the CPU, RAM, and motherboard perform processing, temporary memory, or system-connection roles. Therefore, option A is the only all-input combination.

The governing concept is volatility. RAM uses electronic memory cells that need a continuous electrical supply to represent and preserve their current states while programs are running. When the computer is switched off, that supply ends, the states are lost, and the temporary data disappears. Hence, option C is correct. RAM is not optical storage, not an input device, and not mechanical memory. Non-volatile devices such as ROM, SSDs, and hard drives retain data without continuous power.

The governing concept is the purpose of computer ports and the type of signal they carry. HDMI is designed to transmit high-quality digital video and digital audio together through one cable, so option B is correct. A parallel port and a serial port are older general-purpose interfaces, while a legacy keyboard port is intended for keyboard input, not combined high-definition media.

An expansion slot is a connector on the motherboard that allows an additional circuit card to be installed. A graphics card, sound card, or network adapter can add or improve a computer function, so option C is correct. Renaming a file is a software operation, and holding paper or writing a password has no connection with motherboard hardware.

The governing distinction is physical location. Internal hardware, such as the motherboard, processor, memory, and internal storage, is installed inside the computer cabinet. External hardware, such as a keyboard, mouse, monitor, or printer, connects outside the cabinet. Therefore option D is correct; the other statements incorrectly confuse hardware with software or location.

A touchscreen combines two computer functions. Its display produces visual output by showing text, images, and controls, while its touch-sensitive surface receives input when a user taps, swipes, or types. Thus option A is correct. It is not primarily a storage device, a CPU component, or a power supply, so options B, C, and D do not describe its combined role.

A barcode scanner is an input device. It reads the pattern of dark and light bars, decodes that pattern into numbers or characters, and sends the resulting digital data to a computer or point-of-sale system. Thus option A is correct. It does not print a paper image, provide electrical backup, or produce a sound wave as its direct output.

The governing concept of biometrics is identity verification through measurable human characteristics. A biometric device may capture a fingerprint, facial pattern, iris feature, or voice characteristic and compare it with stored reference data. Therefore option B is correct. Printing passwords, increasing storage, and cooling the CPU are unrelated computer functions, not biometric identification.

The key distinction is the printing material and mechanism. A laser printer uses a charged image, a laser beam, and powdered toner that is fixed to paper with heat. An inkjet printer places tiny droplets of liquid ink on the page. Therefore option D is correct; the other options wrongly describe both devices as scanners or deny the inkjet's use of ink.

Monitor resolution is the number of pixels arranged across the screen, usually expressed as width × height, such as 1920 × 1080. More pixels can show finer detail and a sharper image, although clarity also depends on screen size and viewing distance. Therefore, option A is correct. Weight, speaker volume, and keyboard keys describe different hardware features, not resolution.

A pixel, short for picture element, is one tiny addressable point of a digital image or display. Each pixel has a colour or brightness value, and a large collection of pixels forms the complete picture. Thus option B is correct. A sound unit belongs to audio, a storage unit concerns capacity, and a keyboard key is an input control, so none of those describes a pixel.

A speaker is an audio output device. It receives an electrical or digitally processed audio signal, moves its diaphragm, and creates pressure variations in the air that our ears perceive as audible sound. Therefore option A is correct. Digital text is displayed or printed, optical marks belong to visual input or scanning, and a storage path is a location for files rather than an output produced by a speaker.

A webcam and a digital camera both use an image sensor to receive light from a scene and convert it into digital visual data. That data may become a still image or a sequence of frames forming video, so option B is correct. They are not limited to producing sound, they are not paper printers, and neither device is the computer’s central processing unit. Their connection and typical uses may differ.

The governing concept is optical data reading. An optical drive shines a focused laser onto the disc surface and detects differences in reflected light from the recorded areas; the drive’s electronics interpret these differences as digital information. Therefore option B is correct. A magnetic needle belongs to neither normal CD reading nor this optical process, while sound waves and paper signals are unrelated methods.

A computer uses a small clock battery to preserve the real-time clock when the main power is disconnected. If the date repeatedly resets or becomes inaccurate after shutdown, that battery may be weak and need replacement. Thus option A is correct. A cartridge, graphics-card fan, and mouse wheel have no role in retaining the system date, so the other options do not explain the symptom.