Input and Output Devices: Types, Examples and MCQs

The correct answer is C, touchscreen. A touchscreen accepts a finger tap or a stylus stroke as input and displays the result on the very same surface, so the one piece of hardware performs both jobs. The modem, the network interface card and the hard disk belong to the same dual-role list.

Option A, the scanner, only reads a document or a photograph and feeds the image into the computer, which makes it a pure input device. Option B, the plotter, only draws the output the computer sends it and can take nothing back, so it is a pure output device. Option D, the light pen, is a photo-sensitive pointing device that selects an item by touching the screen, but the display it touches is a separate output device, so the pen itself is input only. Paper setters use exactly these three distractors, so remember the short dual-role list rather than reasoning about each option in the hall.

The correct answer is A, Douglas Engelbart. He built the first mouse, a small wooden box with a pair of wheels underneath, at the Stanford Research Institute, and the patent describes it as an X-Y position indicator for a display system. The name stuck because the wire coming out of the back looked like a tail.

Option B, Charles Babbage, designed the Difference Engine and the Analytical Engine in the nineteenth century and is called the Father of the Computer, a completely different title. Option C, Jack Kilby, demonstrated the first integrated circuit and belongs to the generations chapter, not to input devices. Option D, Christopher Latham Sholes, perfected the mechanical typewriter and gave us the QWERTY keyboard layout, so he is the right answer to a keyboard question and a tempting wrong one here. Keep one invention fixed against each name.

The correct answer is C, dot matrix printer. Its print head carries a column of tiny pins that strike an inked ribbon against the paper, forming each character out of dots. Because the strike passes through the paper, a dot matrix printer can print carbon copies in one go, and it is noisy for the same reason.

Option A, the laser printer, uses a laser beam, a photosensitive drum and dry toner fused by heat, and nothing ever strikes the page. Option B, the inkjet, sprays extremely fine droplets of liquid ink onto the paper without contact. Option D, the thermal printer, heats chemically treated paper so that the characters appear, which again involves no impact. All three are non-impact printers. The one-line rule for the exam is that only the dot matrix, the daisy wheel and the line printers strike the paper.

The correct answer is A, processing of bank cheques. MICR stands for Magnetic Ink Character Recognition. The line of characters printed along the foot of a cheque is set in magnetic ink in the E-13B font, and the reader identifies each character from its magnetic signal, so the cheque is sorted correctly even when it has been folded, stamped or soiled.

Option B, reading objective answer sheets, is the work of OMR, the Optical Mark Reader, which simply detects whether a mark has been made in a fixed position. Option C, billing at a retail counter, is done by a barcode reader that decodes the bar pattern printed on the packet. Option D, recording fingerprints, is the work of a biometric scanner. Banking papers return to MICR every year, so tie it firmly to the cheque and to the E-13B font.

The correct answer is B, pixel. The word is a contraction of picture element. A screen image is a grid of these points, and the number of them across and down the screen is what is quoted as the resolution of the monitor, so a higher pixel count means a finer picture.

Option A, the bit, is the smallest unit of data, a single binary digit, not a unit of a picture, and eight of them make a byte. Option C, the byte, is the unit in which memory and file sizes are measured. Option D, dot pitch, is a real term from the same chapter but it means something else: it is the distance between two neighbouring dots of the same colour on the screen, measured in millimetres, and a smaller dot pitch gives a sharper display. Examiners like to place pixel and dot pitch in the same set of options, so read the stem carefully.

The correct answer is C, DPI, dots per inch. Print quality depends on how many separate dots of ink or toner the printer can place in one inch of paper, so a printer working at a higher DPI produces smoother curves and crisper small text.

The other three options are all speed units, which is exactly the confusion the question is built on. Option A, PPM, pages per minute, measures the speed of a page printer such as a laser printer. Option B, CPS, characters per second, measures a character printer such as the dot matrix. Option D, LPM, lines per minute, measures a line printer such as the drum or chain printer. Learn the set as one line: quality is DPI, and the speed unit changes with the amount the printer commits to at one time, a character, a line or a page.

The correct answer is B, OCR, Optical Character Recognition. A plain scan is only a picture of the page, and nothing in it can be searched or corrected. OCR examines the shape of every character in that picture, matches it against the letters it knows and hands back real text that can be edited in a word processor.

Option A, OMR, the Optical Mark Reader, is a simpler device that only registers whether a mark is present at a fixed spot on the sheet, which is enough for an objective answer sheet but useless for reading words. Option C, MICR, reads only the special magnetic-ink characters of the E-13B font at the foot of a bank cheque. Option D, the QR code, is a two-dimensional barcode that stores encoded data in a pattern of squares; it is read by a scanner but it does not recognise ordinary printed text.

The correct answer is C, maps and engineering drawings. A plotter holds a pen against the paper and moves it, so it draws continuous lines rather than building the image out of dots. That is exactly what large technical drawings need, which is why plotters are used for architectural plans, survey maps and output from design software. The drum plotter and the flatbed plotter are its two types.

Option A, photographs on glossy paper, calls for an inkjet or a photo printer that can lay down blended colour dots. Option B, carbon copies of receipts, needs an impact printer such as the dot matrix, because only a strike through the ribbon presses onto the sheet below. Option D, cash memos at a billing counter, is the ordinary work of a small thermal printer. Note also that a plotter is an output device, although its pen makes it look like a drawing input.

The correct answer is C, laser printer. It builds the image of a whole page on a photosensitive drum with a laser beam, then picks up dry toner on that image and fuses it onto the paper with heat and pressure. Since it commits to one complete page at a time, its speed is quoted in pages per minute and the machine is called a page printer.

Option A, the dot matrix, is a character printer: its head prints a few characters at a time and its speed is given in characters per second. Option B, the daisy wheel, is also a character printer; it carries fully formed letters on the petals of a wheel and strikes them through a ribbon. Option D, the inkjet, sprays droplets line by line as the head sweeps across the paper, so it is treated as a line-by-line printer rather than a page printer. Character, line and page is the ladder to remember.

The correct answer is C, plotter. A plotter takes a drawing that the computer has already prepared and puts it on paper with a moving pen, so data travels out of the machine and never into it. That makes it an output device, and the pen misleads many candidates into marking it as an input.

Option A, the joystick, sends the position of its lever to the computer and is therefore an input device used in games, simulators and machine control. Option B, the light pen, is a photo-sensitive pointing device that tells the computer which point of the screen it is touching, again an input. Option D, the barcode reader, shines light on the printed bars, measures the reflection and sends the decoded number in, which is how billing counters and libraries use it. The safe test is simply the direction in which the data moves.

The correct answer is A, LPM, lines per minute. A line printer, such as a drum or chain printer, sets up and prints a whole line of characters at one stroke, so counting the lines it finishes in a minute is the natural measure of its speed.

Option B, DPI, dots per inch, is not a speed unit at all: it measures the quality of the print, that is, how finely the dots are packed. Option C, PPM, pages per minute, belongs to page printers such as the laser printer, which prepares an entire page before printing it. Option D, CPS, characters per second, belongs to character printers such as the dot matrix and the daisy wheel, which print a few characters at a time. The three speed units line up with the three classes of printer, character, line and page, and the odd one out in this set is always the quality unit DPI.

The correct answer is B, Modulator-Demodulator. The device does two opposite jobs, and the name simply joins them. While sending, it modulates: it converts the digital signal of the computer into an analogue signal that an ordinary line can carry. While receiving, it demodulates: it converts the incoming analogue signal back into digital form that the computer understands.

Because data moves through it in both directions, the modem is one of the standard answers to the question about devices that are both input and output. Options A, C and D are invented expansions of the kind examiners place beside the correct one to test whether the candidate has learnt the phrase or is guessing from the sound of the word. None of them describes any real device. Remember the pair of actions, modulate while sending and demodulate while receiving, and the full form cannot be forgotten.