Chapter 2 Q3 output devices (Monitor, Printer, Speaker,Projector

Computer Education

CHAPTER 2

Q 3: What is meant by output? Write a detailed note on output devices of a computer.

Output:
Output means result or the processed form of any thing. Suppose we want to get juice of carrot, for this we will enter carrots in juicer and juicer will provide us juice. Here juice is output of the juicer. The Juicer provides us output after processing.
So we can define that output is the processed form of input. Computer also provides us output of the data which we enter in it after processing. Output is the result of input.

Output Devices

The devices, which are used for output processed data are called output devices. A computer uses output devices to communicate with the world, which is outside the computer. Although there are many kinds of input devices, there are currently three common types of output devices:
· Monitor
· Printers
· Sound systems

The Monitor:
It is the most commonly used output device. The monitor is a soft copy (means we can modify contents of data and data is temporarily on the screen) output device. A monitor looks like a television and it displays alphanumeric and graphic output. A monitor is also called Visual display unit (VDU) or Cathode Ray Tube (CRT). The special program called Screen Dump Saves contents of the monitor screen.

Types of Monitor:
According to resolution, a monitor is of two types:
· High Resolution (Good quality of text and graphics on the screen)
· Low Resolution (Low quality of text and graphics)
Sizes of Monitor
According to screen size, a monitor is available in different sizes:
· 3 to 30 inch screens are available in the market.
· 15 and 17-inch screen are common now a day.

According to volume, a monitor is of two types:
· CRT (Cathode ray tube):
Monitors of this type screen are used commonly in homes, colleges and offices. These monitors are big and require big area to place, power and have weight more than 10 pounds. We cannot move these monitors easily.

· Flat - panel tube:
These monitors are also available nowadays in markets. These monitors are normally used in Laptop computers and we can also use these monitors in desktop computers. There are several types of flat-panel monitors, but the most common is the liquid crystal display (LCD) monitor.

According to display, a monitor is of two types:
· Monochrome
These monitors display images only in single colour. This colour can be white, green, blue, red or amber. This monitor can display shades of one colour and the computer industry uses the term gray scales to refer to the number of shades of a colour that can be shown on a monochrome monitor’s screen.

· Colour
This monitor shows graphics with full colours. These monitors produce images in three mixed colours, which are red, green and blue that is why these are also called RGB monitors. A typical monitor can display 256 to 65536 colours.

Touch Screen Monitor:
Touch Screen monitors allow the user to point directly at the computer display, usually to select from a menu of choices on the screen. Most touch-screen computers use sensors in, or near, the computer’s screen that can detect the touch of a finger. Touch screens are appropriate in environments where dirt or weather would render keyboards and pointing devices useless and where a simple interface is important.

Printers:

Printers are the most commonly used output devices that can be found in almost all computer centres. Printers are used to get prints of important documents on a paper. The output, which is generated by a printer, is called hard copy of the data. Printer is also called a hard copy output device.

Categories of printers:
Broadly there are two categories of printers:
· Impact printers
This printer uses the familiar typewriter approach of hitting a character against paper and inked ribbon.

· Non-impact printers
These printers do not hit or impact a ribbon to print. They use thermal electrostatic, chemical, and inkjet technologies. These printers move a print head across the page.

Classification of printers:
Printers are classified as:
· Character printers
· Line printers
· Page printers

Following are commonly used printers:

Dot-matrix printers:
These printers print each character as a sample of dots. The print head comprises a matrix of tiny needles, typically seven rows with nine needles in each (9 ´ 7 matrix). Printing quality of this printer is not good and speed of this printer is also very slow. The quality and price of dot-matrix printer depends on two factors.
i) Number of dots per inch termed as DPI
ii) Number of characters or words per minute

100 – 150 DPI
200 – 300 Character per minute
40 – 80 Words per minute



Laser Printers:
These are very high speed nonimpact printers which produce documents at speeds of over 20,000 lines per minute. This type of printers use a special beam of light called LASER. Where Laser stands for Light amplification by Simulated Emission of Radiation. With LASER, magnetic material in shape of powder is thrown on paper in the form of microscopic dots. The quality and cost of LASER printer depends on two factors:
· Number of dots per inch (DPI)
· Number of pages per minute

There are three qualities of a LASER printer:

Cheapest Quality Laser printer:
This type of laser printer can print
600 DPI
5 – 10 Pages per minute

Middle quality LASER:
This type of LASER can print
300 – 1200 DPI
10 – 20 Pages per minute

High quality LASER:
This type of LASER can print:
600 – 1200 DPI
30 – 300 Pages per minute

LATEST HIGH QUALITY LASER PRINTER


Inkjet Printers:
These are nonimpact character printers and similar to LASER printer. In this type of printer, ink is used in the shape of very tiny drops on the paper to form a character. This printer works slower as compared to LASER printers. Its speed is 1 to 6 pages per minute. These are cheaper in initial cost and quality of paper printing is same as laser printer but cost of per page is four times greater than a laser printer. Suppose if a LASER printer page costs you 1 rupee then an inkjet printer page will cost you 4 rupees. Remember that bubble jet and inkjet are the same printers.
Inkjet printer

Sound systems:
Just as microphones are now important input devices, speakers and their associated technology are key output systems. Today, when you buy a multimedia PC, you are getting a machine that includes a CD-ROM drive, high-quality video controller, speakers, and a sound card.
The speakers attached to these systems are similar to ones you connect to a stereo. The only difference is that they are usually smaller and they contain their own small amplifiers. Otherwise, they do the same thing any speaker does.

Projector:

Projector is also an output deivce.
It is used to show presentations. There two main types of projector.

Simple Projector
Multemedia projector.