Output Devices
Following are few of the important
output devices which are used in a computer.
- Monitors
- Graphic Plotter
- Printer
Monitors
Monitors, commonly called as Visual
Display Unit (VDU), are the main output device of a computer.
It forms images from tiny dots,
called pixels that are arranged in a rectangular form.
The sharpness of the image depends
upon the number of pixels.
There are two kinds of viewing screen
used for monitors.
- Cathode-Ray Tube (CRT)
- Flat- Panel Display
Cathode-Ray Tube (CRT) Monitor
The CRT display is made up of small
picture elements called pixels. The smaller the pixels, the better the image
clarity, or resolution.
There are some disadvantages of CRT:
- Large in Size
- High power consumption
Flat-Panel Display Monitor
Emissive Displays - The emissive
displays are devices that convert electrical energy into light. Example are
plasma panel and LED(Light-Emitting Diodes).
Non-Emissive Displays - The
Non-emissive displays use optical effects to convert sunlight or light from
some other source into graphics patterns. Example is LCD(Liquid-Crystal Device)
Printer
Printer is an output device, which is used to print
information on paper.
There are two types of printers:
- Impact Printers
- Non-Impact Printers
Impact Printers
The impact printers print the characters by striking them on
the ribbon which is then pressed on the paper.
Characteristics of Impact Printers are the following:
- Very low consumable costs
- Very noisy
- Useful for bulk printing due to low cost
- There is physical contact with the paper to produce an image
Impact printers are of two types
- Character printers
- Line printers
Character Printers
Character printers are the printers which print one
character at a time.
These are further divided into two types:
- Dot Matrix Printer(DMP)
- Daisy Wheel
1)Dot Matrix Printer
In the market one of the most popular printers is Dot Matrix
Printer. These printers are popular because of their ease of printing and
economical price. Each character printed is in form of pattern of dots and head
consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to
form a character that is why it is called Dot Matrix Printer.
Advantages of Dot Matrix Printer
- Inexpensive
- Widely Used
- Other language characters can be printed
Disadvantages of Dot Matrix Printer
- Slow Speed
- Poor Quality
2)Daisy Wheel
Head is lying on a wheel and pins corresponding to
characters are like petals of Daisy (flower name) that is why it is called
Daisy Wheel Printer. These printers are generally used for word-processing in
offices which require a few letters to be sent here and there with very nice
quality.
Advantages of Daisy Wheel
- More reliable than DMP
- Better quality
- The fonts of character can be easily changed
Disadvantages of Daisy Wheel
- Slower than DMP
- Noisy
- More expensive than DMP
Line Printers
Line printers are the printers which print one line at a
time.
Line Printer are of further two types
- Drum Printer
- Chain Printer
1)Drum Printer
This printer is like a drum in shape so it is called drum
printer. The surface of drum is divided into number of tracks. Total tracks are
equal to size of paper i.e. for a paper width of 132 characters, drum will have
132 tracks. A character set is embossed on track. The different character sets
available in the market are 48 character set, 64 and 96 characters set. One
rotation of drum prints one line. Drum printers are fast in speed and can print
300 to 2000 lines per minute.
Advantages of Drum Printer
- Very high speed
Disadvantages of Drum Printer
- Very expensive
- Characters fonts cannot be changed
Chain Printer
In this printer, chain of character sets are used so it is
called Chain Printer. A standard character set may have 48, 64, or 96
characters.
Advantages of Chain Printer
- Character fonts can easily be changed.
- Different languages can be used with the same printer.
Disadvantages of Chain Printer
- Noisy
Non-impact Printers
Non-impact printers print the characters without using
ribbon. These printers print a complete page at a time so they are also called
as Page Printers.
Non-Impact printers are of two types
- Laser Printers
- Inkjet Printers
Characteristics of Non-impact Printers
- Faster than impact printers.
- They are not noisy.
- High quality.
- Support many fonts and different character size.
Laser Printers
These are non-impact page printers. They use laser lights to
produce the dots needed to form the characters to be printed on a page.
Advantages of Laser Printers
- Very high speed
- Very high quality output
- Give good graphics quality
- Support many fonts and different character size
Disadvantages of Laser Printers
- Expensive.
- Cannot be used to produce multiple copies of a document in a single printing.
Inkjet Printers
Inkjet printers are non-impact character printers based on a
relatively new technology. They print characters by spraying small drops of ink
onto paper. Inkjet printers produce high quality output with presentable
features.
They make less noise because no hammering is done and these
have many styles of printing modes available. Colour printing is also possible.
Some models of Inkjet printers can produce multiple copies of printing also.
Advantages of Inkjet Printers
- High quality printing
- More reliable
Disadvantages of Inkjet Printers
- Expensive as cost per page is high
- Slow as compared to laser printer