Subject: Computer Science
Output devices are those devices which display the required result in simple words to the users. The output device provides the output of data or information. The purpose of the output devices is to translate data and information from electrical impulses to a human-readable format. There are two principal kinds of output. They are described below:
It refers to data that is shown on a display screen or sound produced by a speaker. It is present in a digital form on a computer. This kind of output is untouchable. It is temporary in nature. For example, content displayed on a screen.
It refers to printed output printed on the paper or some material that can be touched and carried for being shown to others. It is permanent in nature and can keep in paper files or can be looked later when a person is not using the computer. For example, outputs produced on paper by printer or plotter in the form of text or graphics, etc.
The monitor is display screen that is used to display text and graphics, allowing users to view the result of the processing. It is the most common and popularly used output device for producing soft copy output. It displays the generated output on a television-like a screen. Monitor is classified on the following basis:-
Classification of monitor on the basis of the colors displayed:
It displays only the color such as green or white against a contrasting background which is usually black. This monitor is used for text-only displays. It basically processes only two colors, one for foreground and one for the background.
The grayscale monitor is a special monochrome monitor such that it can show the varying intensity of gray against a white or off-white background.
This monitor can display 16 colors to several million colors. Color CRT in a graphics system is designed as RGB monitor. Color graphics system can be designed by several types of CRT display device.
Classification of monitor on the basis of their display technique:
CRT operates much like a television set. A single electron gun in a monochrome CRT sends a beam of electrons towards phosphor coated to the screen surface. The screen’s phosphor coating is organized into a grid of dots. The color CRT system uses three electron guns to scan dots of red, green, and blue. So, color monitors are sometimes called RGB monitors.
There are several types of flat panel monitor such as LCD, LED, and Plasma Display
i) Liquid Crystal Display (LCD) Monitor:
A liquid crystal display (LCD) monitor is a computer monitor or display that uses LCD technology to show clear images and is found mostly on laptop computers and flat panel monitors. This technology has replaced the traditional cathode ray tube (CRT) monitors, which were the previous standard and once were considered to have better picture quality than early LCD variants. With the introduction of better LCD technology and its continuous improvement, LCD is now the clear leader over CRT, in terms of color and picture quality, not to mention capabilities for large resolutions. Also, LCD monitors may be made much more cheaply than CRT monitors. The liquid crystalline material is sandwiched between two glass or plastic plates. The front plate is transparent and the back is reflective. LCD is lighter in weight, not bulky but expensive compared to CRT monitors. It consumes low voltage and power consumption.
ii) Light Emitting Diode (LED) Monitor:
LED monitor contains an array of light emitting diodes as a video display. These diodes are turned on or off to display the output. Initially, it was used only for simple digital display like calculator, digital watch. At present, it is the popular monitor for a television set, desktop PC,laptop, mobile phones, tablet PC.
ii) Gas-Plasma Display:
Gas-plasma display is like a neon bulb, in which the display uses a gas that emits light in the presence of an electric current. At present, gas-plasma technology is more expensive and thus not used as often as LCD and LED technology. The arrangement of the transistor in the screen can be an active matrix or passive matrix. It can be used in portable computing devices. It has a larger viewing angle of almost 180 degrees. It is also an expensive monitor.
The printer is a peripheral device used to print text, picture, illustration, figure and image. It is used to produce hard copy output i.e. in the permanent readable form. There are two types of printers.They are Impact printer and Non-impact printer.
An impact printer has mechanism resembling that of a typewriter. The efficiency of impact printer is less as compared to the non-impact printer because it uses electrical energy which is further converted into heat and sound. It is slow while printing. It uses ink ribbon for printing.
A non-impact printer is faster and quieter than impact printer because they have fewer moving parts. It is faster than an impact printer. It produces low noise compared to impact printer. It can not produce multiple copies at the same time. It uses liquid or powder ink for printing.The examples of printers are described below:
DOT MATRIX PRINTER or impact matrix printing is a type of computer printing which uses a print head that moves back-and-forth, or in an up-and-down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like the print mechanism on a typewriter. In this printers, there are 9, 18, or 24 pins, with the 24-pin head offering the best print quality. This printer can print draft quality, a coarser- looking 72 dots per inch vertically, or near letter quality, a crisper looking 144 dots per inch vertically.
It is an older type of impact printer used with microcomputers, which has a removable print wheel the flower like daisy wheel consisting of spokes. It is letter-quality impact character printer. Daisy wheel printer usually gives a better quality of print but more expensive than dot matrix printer. It has a speed about 90 characters per second. It has a fixed font and cannot print graphics.
It is another type of impact printer which prints a whole line of characters at once rather than a single character at a time. Some of these can print up to 3,000 lines a minute. It can print only text of fixed size and font. It is appropriate for continuous printing such as printing mark-sheet, bank statement, bill receipt.
It is a Non-impact character printer which forms images with little dots, but the dots are much smaller and more numerous. Most color printing is done on an ink-jet printer. It sprays small, electrically charged droplets of ink from four nozzles through holes in a matrix at high speed onto paper. In this printer, the multiple nozzles print fine images at high speed.
A laser printer is a Non-impact page printer. An entire page is printed at a time. It produces a high-quality print. This printer has print resolution range from 300 to more than 2400 dpi. It is expensive than other printers. A laser printer also uses the principle of dot-matrix printers in creating dot-like images. They produce sharp, crisp images of both text and graphics. They can print 4-20 pages per minute for individual microcomputers.
A thermal printer uses colored waxes and heat to produce images by burning dots onto special heat sensitive paper. It can provide the highest quality desktop color printing available. They are expensive and require expensive paper. So, they are generally used for high volume printing.
A plotter is a specialized output device designed to produce high-quality graphics in a variety of colors. The plotters is especially useful for creating maps and architectural drawings, although they may also produce less complicated charts and graphs. It uses ink pen or inkjet mechanism to draw graphics or drawings. The pen is driven by monitor. Drawing can be prepared on paper or plastic sheets. Pen plotter is slower than inkjet plotters. It is used for low to medium volume job. The plotter is much more expensive than printers. Drum plotter, micro-grip plotter, inkjet plotter, etc are the examples of plotters.
The multimedia system without speaker is incomplete. It amplifies sound output. A good pair of speakers connected to the sound card will give you loads of listening pleasure. The audio output of the computer system relates through the speakers. This enables audible alerts to be given to the user, as well as the playback of other sounds and music. moe advanced speaker systems exist, allowing certain programs (such as music, creation software and games) to use surround sound capabilities to beneficial effect.
(Shrestha & Manandhar, 2014)
Shrestha, R. P., & Manandhar, s. (2014). Computer Essential. Kathmandu: Ashmita publication.
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