Output Devices

Output:
The data that has been processed into useful information is called output.

Types of Output:
Different types of output are as follows:
  • Soft Copy: The output shown on display screen is called soft copy output.The common devices to produce soft copy are monitors and speakers.
  • Hard Copy: The output printed on paper is called hard copy output.The common devices to produce  hard copy output are printers and plotters.
Output Devices:
The hardware components that are used to receive information from the computer are called output devices.Output devices take information from the computer and convert it in a from that is understandable by the users.

1. Printers
A printer is an output device that prints characters, symbols and graphics on paper . The printed output is called hard copy. Printers are commonly used in businesses to print different documents. 

Different categories of printers are as follows:
  1. Impact Printers
  2. Non-Impact Printers

1.Impact Printers:
An impact printer works like a typewriter.It prints characters or images by striking a print hammer or set of pins against an inked ribbon . The ink is pressed from ribbon on the paper to produce the output.Impact printers are the oldest print technologies which are still produced. The impact printers are used where low-cost printing is required.
Three most common forms of impact printers are as follows:
  • Dot Matrix Printers                                                                               
  • Daisy Wheel Printer
  • Line Printer

1.Dot Matrix Printer:

A dot matrix printer is an impact printer.It produces printed images when tiny pins on a print head strike an inked ribbon. When the ribbon presses against the paper, it creates dots that from characters and graphics.The print head on a dot matrix printer can contain nine to twenty-four pins.A higher number of pins print more dots that produce higher quality.Dot matrix printers do not provide high quality
output.They produce a lot of noise while printing. The printing cost of these printers is very cheap.

2.Daisy Wheel printer:
Daisy wheel printer is similar to a typewriter.It uses a print wheel. The print wheel is called daisy wheel. Each petal of daisy wheel contains character. A motor rotates the wheel. A hammer strikes a petal against the ribbon when the desired character reaches the position on the paper. This prints the character on the paper. Daisy wheel printer is slower than dot matrix printer but better in quality.


3.Line Printer:
Line printer is a fast impact printer. It can print multiple characters on the sam line at a time. Its speed is measured in lines per minute (lpm). The speed range of line printer is from 300 LPM to to 2400 LPM. The line printers are faster than dot matrix and daisy wheel printers. They are more noisy and provide limited font capability. They produce lower print quality than recent printing technologies. Band printer and chain printer are the examples of line printers.

4. Non-Impact Printers:
A non-impact printer prints characters and graphics on paper without striking paper. The characters are printed on paper with some means such as laser. Some printers use spray ink while others use heat and pressure to create images. These printers are faster than impact printer. However, they are most costly than impact printers. They produce no noise during printing. The print quality of non-impact printers is better than impact printers. Different kinds of non-impact printers are laser printer and inkjet printer.

Different types of non-impact printers are as follows:

a. Laser Printer 
Laser printers are non-impact printers. Its working similar to  a photocopying machine. The laer printer creates image on the paper by laser beam. LASER stands for Light Amplification by Stimulated Emission of Radiation. Laser throws magnetic material powder on paper in the form of microscopic dots. The density of these dots ranges from 300 to 2000 Dots Per Inch (DPI). The printing speed of laser printers can be from 5 to 300 pages per minute (ppm). Laser printers are also called page printers. They print complete page at a time. They produce very high quality print. They are faster than inkjet and dot matrix printers. Laser printers are mostly used in business field.

b. Inkjet Printer                                               
An ink-jet printer is a type of non-impact printer.It prints characters and graphics by spraying tiny drops of liquid ink on paper .These printers can produce quality text and graphics in both black- and white and color. 
Inkjet prints are slower than laser printers. They can print 1 to 6 pages per minute.Its print quality is higher than dot matrix printer.They are also relatively inexpensive.
2. Plotter:
A plotter is an output device that is used to produce image-quality graphics a variety of colors . Plotters are used to create maps, architectural drawings, graphs and charts. A plotter works by drawing lines on paper using pens held in a mechanical arm.



3. Monitor or Display Screen:
Monitor is the most common output device. The output displayed by monitor is called soft copy. A monitor looks like a television and displays text and graphics. Different display screens can distinguished on the basis of the following features:
  • size
  • colors
  • Resolution
  • Video Display Adapters
  • Refresh Rate
  • Dot pitch
Types of Display Screens

1. CRT Monitor
CRT monitor is the most common form of display screen. It can display text and graphics. It uses a cathode ray tube (CRT) that creates an image by an electronic beam.CRT consists of one or more guns that fire a beam of electrons inside the screen .The screen is coated with very tiny phosphor dots from inside. The beam of electrons repeatedly falls on the surface of screen.CRT  in color monitors consists of three guns. These guns generate red, green and blue (RGB)colours.
2. Flat panel Monitors :
Laptop PCs use flat - panel monitors.These monitors take less space. Flat panel monitors use a variety of technologies.The most common technology is LCD  .LCD monitors use much less power than CRT monitor.These monitors are available in different sizes such as 15'' , 17'' 18'' 21'' 23''.
4.Speakers & Headsets

A type of output produced in the form of sound, voice or music is known as audio output. Speakers and headsets are two commonly used audio output devices.Many personal computers have internal speaker. Headsets are also used to produce audio output.


5. Data Projectors:
Data projector is an output device that projects the output of computer screen onto a larger screen. The output projected by data projector can be viewed by a number of people very clearly.Data projectors are used in classes to deliver lectures to many students etc.