Following
are some of the important output devices 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. It
takes more than one illuminated pixel to form a whole character, such as the
letter ‘e’ in the word help.
A finite number of characters can be displayed on a screen at
once. The screen can be divided into a series of character boxes - fixed
location on the screen where a standard character can be placed. Most screens
are capable of displaying 80 characters of data horizontally and 25 lines
vertically.
There are some disadvantages of CRT −
- Large in Size
- High power
consumption
Flat-Panel Display Monitor
The flat-panel display refers to a class of video devices that
have reduced volume, weight and power requirement in comparison to the CRT. You
can hang them on walls or wear them on your wrists. Current uses of flat-panel
displays include calculators, video games, monitors, laptop computer, and
graphics display.
The flat-panel display is divided into two categories −
· Emissive
Displays − Emissive displays are devices that convert electrical energy
into light. For example, plasma panel and LED (Light-Emitting Diodes).
· Non-Emissive
Displays − Non-emissive displays use optical effects to convert sunlight
or light from some other source into graphics patterns. For example, LCD
(Liquid-Crystal Device).
Printers
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
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
These 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
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 the 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 which is why it is called Dot Matrix Printer.
Advantages
- Inexpensive
- Widely Used
- Other language
characters can be printed
Disadvantages
- Slow Speed
- Poor Quality
Daisy Wheel
Head is lying on a wheel and pins corresponding to characters
are like petals of Daisy (flower) which is why it is called Daisy Wheel
Printer. These printers are generally used for word-processing in offices that
require a few letters to be sent here and there with very nice quality.
Advantages
- More reliable
than DMP
- Better quality
- Fonts of
character can be easily changed
Disadvantages
- Slower than
DMP
- Noisy
- More expensive
than DMP
Line Printers
Line printers are the printers which print one line at a time.
These are of two types −
- Drum Printer
- Chain Printer
Drum Printer
This printer is like a drum in shape hence it is called drum
printer. The surface of the drum is divided into a number of tracks. Total
tracks are equal to the size of the paper, i.e. for a paper width of 132
characters, drum will have 132 tracks. A character set is embossed on the
track. 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
- Very high
speed
Disadvantages
- Very expensive
- Characters
fonts cannot be changed
Chain Printer
In this printer, a chain of character sets is used, hence it is
called Chain Printer. A standard character set may have 48, 64, or 96
characters.
Advantages
- Character
fonts can easily be changed.
- Different
languages can be used with the same printer.
Disadvantages
- Noisy
Non-impact Printers
Non-impact printers print the characters without using the
ribbon. These printers print a complete page at a time, thus they are also
called as Page Printers.
These printers are of two types −
- Laser Printers
- Inkjet
Printers
Characteristics of Non-impact Printers
- Faster than
impact printers
- They are not
noisy
- High quality
- Supports 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
- Very high
speed
- Very high
quality output
- Good graphics
quality
- Supports many
fonts and different character size
Disadvantages
- 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. Color printing is also possible. Some
models of Inkjet printers can produce multiple copies of printing also.
Advantages
- High quality
printing
- More reliable
Disadvantages
- Expensive as
the cost per page is high
- Slow as
compared to laser printer
