PRINTERS

ABOUT PRINTERS AND ITS TYPES

Output is data that has been processed into a used form, called information.

An output device is any hardware component that can display information to

a user. The main and most common output devices in a computer system are

the Printer and the V.D.U.

Printer 

A printer is an output device that produces text and graphics on a

physical medium such as paper. Printed information is often

called hard copy because the information exists physically

and is a more permanent form of output than that presented

on a VDU (Monitor). Printers can be grouped into impact

and non-impact printers.

An impact printer forms characters and graphics on a piece of paper by

striking a mechanism against an ink ribbon that physically contacts the

paper

.
A non-impact printer forms characters and graphics on a piece of paper
without actually striking the paper
.
The printing speed of a printer is usually expressed in pages per minute
(ppm). Printer resolution is often expressed in dpi (dots per inch). The larger
the number, the higher the resolution.
  Advantages of printers include
Information produced is permanent.
 Disadvantages of printers include
The time to get the printout is slow, when compared with display
 devices.

 Paper is wasted for obtaining the output.
Printers are generally noisier than display devices.
 The following types of printers will be considered in more detail;
 1. Daisy wheel Printer
 2. Dot-matrix printer
 3. Line printer
 4. Ink-jet printer
 5. Laser printer
 6. Plotter

Printers
Impact 
Daisy wheel Printer
Dot Matrix
Line Printer

Non - Impact
Ink-jet printer
Laser printer
 Plotter


Daisy Wheel printer 

A daisywheel printer is an impact printer that uses a wheel as a print head.
As the wheel rotates, a hammer strikes the backside of the spoke and presses
it against the paper to print a character.

Advantages of a daisywheel printer
Can print letter quality characters.

Disadvantages of a daisywheel printer
1)Printing speed is very slow.
2)Cannot print graphics.

Dot-Matrix Printer 
A dot-matrix printer is an impact printer that produces
printed images with a print head striking mechanism.
Most dot-matrix printers use continuous-form
paper. A higher number of pins on the print
head means more dots are printed, which
results in higher print quality (i.e., a 24-pin
printer has better print quality than a 9-pin
printer).

The diagram above shows the grid (or dot matrix), the way the letter A is
designed on this matrix, how the letter A is formed on paper, and what a close
up of the printout would look like. Note that the final image is fuzzy and not
cleanly formed because the cloth ribbon and the paper texture cause the ink
to smear, and also because of slight misalignment of the pins.
The speed of a dot-matrix printer is normally measured by the number of
characters per second (cps) it can print.

Advantages of dot-matrix printers
1)Dot-matrix printers can print multipart forms.
2)Dot-matrix printers can withstand dusty environment, vibrations, and
extreme temperature.
Disadvantages of dot-matrix printers
1) Dot-matrix printers are generally noisy because of the striking
mechanism.
2)Print quality of dot-matrix printers is not as good as those from ink-jet
printers and laser printers.

Line Printer 
A line printer is a high-speed impact printer that prints an
entire line at a time. The speed of a line printer is
measured by the number of lines per minute (lpm) it can
print. Line printers are often used with mainframes,
minicomputers, or with a network in applications such as
manufacturing, distribution, or shipping.
Ink-Jet printer glossary pg.157
An ink-jet printer in a non-impact printer that forms
characters and graphics by spraying tiny drops of liquid
ink onto a piece of paper. Ink-jet printers can produce
letter-quality text and graphics in both black-and-white
and colours. Some ink-jet printers can print photo-quality
images on any type of paper. Printer resolution is
measured in dots per inch (dpi). The speed of an ink-jet
printer is measured in lines per minute (lpm).

Advantages of inkjet printers include
1) Inkjet printers are generally quiet.
2)Inkjet printers can produce high quality colour output.

Disadvantages of inkjet printers include
 1) Specialized papers are required to produce high quality colour output.
2)The ink cartridges and specialized papers are expensive.
3)The ink may smear when printed on ordinary paper.

Laser Printer 
The mechanism of how a laser printer works is similar to
a photocopier. Laser printers are also known as page
printers because they process and store the entire page
before they actually print it. Most laser printers today
can print text and graphics in very high quality
.
resolutions, ranging from 600 dpi to 1200 dpi. Laser printers can print text at
speeds of four to over thirty pages per minute.

Advantages of laser printers include
1) Laser printers are generally quiet and fast.
2)Laser printers can produce high quality output on ordinary papers.
3)The cost per page of toner cartridges is lower than other printers.

Disadvantages of laser printers include
1) The initial cost of laser printers can be high.
2) Laser printers are more expensive than dot-matrix printers and ink-jet
printers
plotters:
A plotter is a large printer that generates high-quality
documents by moving ink pens over the surface of a page.
Plotters are particularly useful to engineers and architects, as
they produce high-quality blueprints, maps, and floor plans.

Two basic types of plotters are pen plotters and X-Y plotters.

Advantages of plotters include
Can print on large printers.
High quality printing
Raster vs Vector Devices
Dot-matrix, inkjet and laser printers are called Raster imaging devices,
because they construct the image from a matrix (raster) of dots.
Plotters
Plotters are Vector imaging devices – it constructs the image from a series of
line segments produced by dragging a pen over a sheet of paper under
computer control. A Vector in computer graphics is a line that is defined by its
start and end point.

A Comparison of Impact and Non-impact Printers
Impact Printer Nonimpact Printer

Advantages
Ideal for printing composite
forms because they can easily
print through many layers of
paper.
Can normally withstand dusty
environment, vibrations, and
extreme temperature.
Generally much quieter than
impact printers because there is
no striking mechanism.
Can produce high quality output.

Disadvantages
Generally noisy because of the
striking activity.
Produce near letter quality print
only, which is just suitable for
printing mailing labels, envelopes,
or invoices.
Cannot print composite forms.