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