The printers are one of the most useful
output device for use with a computer.
In the early days of computing, it was
the only source of information about
what the computer had done. Printers
are used to produce hard copy or
permanent record of computer’s
output. In computer is a printer is a
device that accepts text and graphic
output from a computer and transfers
the information to paper, usually to
standard size sheets of paper. Printers
are sometimes sold with computers,
but more frequently are purchased
separately. Printers are in different
sizes,speed,sophistication,and cost. In
general, more expensive printers are
used for higher-resolution color
Two Categories Of Printers
Printers are classified into two main
1( :-.An impact printer is a type of printer
that operates by striking a metal or
plastic head against the paper,
marking the page with the appropriate
character, dot, line, or symbol. Impact
printers work like typewriters.
Types Of Impact Printers
A(:- Dot Matrix Printers
B(:- Daisy Wheel Printers
C(:- Line Printers
Dot Matrix Printer:- Dot matrix printer is an impact printer. Dot matrix printing or impact
matrix printing is a type of computer printing which uses a print head that moves back
and forth, or in an up and down motion, on the page and prints by impact, striking an
ink-soaked cloth ribbon against the paper, much like the print mechanism on a
typewriter. Each dot is produced by a tiny metal rod, also called a “wire” or “pin”,
which is driven forward by the power of a tiny electromagnet or solenoid, either
directly or through small levers (pawls(. In a dot matrix printer a letter is formed by the
combination of dots. It has 9,18,24 or 32 pins arranged vertically in a print head. It
can make pictures also. A normal dot matrix printer has speeds varying from 50 to
600 characters per second. The carriage width of a printer also varies ranging from
80 columns to 132 columns. A standard-width printer prints 80 characters per line.
Daisy Wheel Printers
The daisy wheel printer uses a flat
disk or wheel with petal like
projections each with a
different character at the tip.
The wheel rotates to bring the
desired character into position.
A character is formed when
hammer strikes the petal under
it. Daisy wheels are available
in several formats (bold letter,
italics etc(. A daisy wheel
printer is slower than a dot
matrix machine. As print wheel
takes more rime to bring the
desired petal in position.
However produces high-quality
Daisy wheel printing is an impact printing technology invented in 1969 by David S.
Lee at Diablo Data Systems. It uses interchange able pre-formed type element
s, each with typicaly96 glyphs, to generate high-quality output comparable to
premium typewriters such as the IBM Selectric, but two to three times faster.
Daisy wheel printing was used in electronic typewriters, word processors and
computers from 1972. The daisy wheel is considered to be so named because
of its resemblance to the daisy flower. A number of different types of high
speed printers have been developed to satisfy the needs of large computer
systems. These are called line printers as they print one complete line at a
time. Line printers are also impact printers and may be further divided into
drum printers and band or chain printers. Some of these printers can produce
over 3000 lines per minute.
2(:-Non-Impact Printers:- Non-impact printers have been developed
which produce a printed image without striking the paper. These
printers use new methods that have improved printing quality and
speed. Non-impact printers are noiseless and faster than impact
Some types of non-impact printers:-
A(:- Electrostatic printers B(:- Electro thermal
C(:- Ink jet printers D(:- Laser printers
A):- Electrostatic printers:- Electrostatic printers are high-speed non-
impact line printers.
Electrostatic Printing Process:-Electrostatic printing is a printing
technique done without plate, ink or form. The paper is coated with a
thin layer of zinc oxide, making it an insulator in the dark and
simultaneously a conductor of electricity when exposed to light.
These machines are used for printing of geographic maps. With the
advancement in technology and higher speed, the machines are
also being used to print small books. Electrostatic printers are used
for short run printing as they are faster and also do not cost much.
Electrostatic printing use a positively charged toner/inks that is
attracted to paper which in turn is negatively charged. The paper is
moved through a digital ink bath; positively charged particles in ink
stick to the negative charge on the paper. The printers print in black
and white or color as the case may be, and some handle paper up
to six feet wide.
Application of Electrostatic Printing:-Electrostatic printers are widely
used in different industries for short run printing. They are popular
for photocopying jobs both black & white and colored . These
printers are faster than inkjet printers.
B):-Electro thermal printers:-Electro thermal printers
produce characters on heat sensitive waxy paper. It is an type of
printer in which a thermoplastic ink is transferred from a ribbon to
the base medium (usually paper or transparent film) by localized
heating. The heating occurs as current is passed from discrete
electrical contacts on the print head through a resistive layer in the
ribbon to a common return layer. Compared with thermal transfer
printers, the print quality is less dependent on the surface finish of
the receiving medium but the complexity of the ribbon makes the
cost of usage higher. Improvements in thermal transfer printers
have made electro thermal technology obsolete. These were
popular a few years ago because they are portable and low cost.
But the drawback is that they require special heat sensitive waxy
C):-Inkjet printers:-Ink jet printers work in the same way as dot
matrix printers except that ink jet printers have fine tiny nozzles
instead of tiny pins used in dot matrix print head.
1):-Ink jet printing is a type of computer printing that recreates a digital
image by propelling droplets of ink onto the paper, plastic, or
other substrates. Nozzles spray a stream of ink onto the paper.
Because the ink is put directly on the paper, therefore, these
printers require ink in reservoirs instead of ribbon. Since no
mechanical movement is involved, hence these printers are much
quieter and have speed of about 200 character per second. Ink jet
printers are also available which have more than one ink
reservoir, each with a different colour. The colours can be chosen
through software to allow the printer to print in rainbow colours.
Thus a full colour graphic image from a computer screen can be
obtained very quietly on paper.
2):-Ink jet printers are the most commonly used type of printer, and the
range from small inexpensive consumer models to expensive
3):-The concept of ink jet printing originated in the 19th
century, and the
technology was first extensively developed in the early 1950s.
Starting in late 1970s ink jet printers that could reproduce digital
images generated by computers were developed, mainly by
Epson, Hewlett-Packard (HP), and Canon.
•D):-Laser printers:-Laser printers are the faster non-impact printers.
These printers use laser and electro-photographic technology. Laser printer,
a computer printer that produces high-resolution output by means of a
process that is similar to photocopying. A bit-mapped image of a page is
formed in the computer by software. This is transferred to the printer which
activates a laser beam. The laser beam duplicates the image on a rotating
drum and forms a charged image on it. The image is transferred on the
paper that passes between the drum and positively charged corona wire.
The dots of the toner forming the image get fused onto the paper under the
combined effect of heat and pressure when passing through the roller. The
printed result from a laser printer is impressive and better in quality.
•In place of reflected light from an image (as is used in xerography), a laser
printer uses data sent from a computer to turn a laser beam on and off
rapidly as it scans a charged drum. The drum then attracts toner powder to
the area not exposed to the light. Finally, the toner is fused to paper over a
belt by heated rollers. In a write-black printer the laser positively charges
the printed areas to attract the toner, which gives better detail than a write-
white printer. In a write-white printer, the beam charges the areas not to be
printed to repel the toner, which gives a denser image. Faster , quieter, and
capable of producing more attractive results than standard printers, laser
printers have become an important means of printing business documents
since they became more generally available in (1984) for personal
computers. See also with desktop publishing.. A laser printer have a speed
of greater than 20,000 lines per minute.