An output device is any piece of computer hardware equipment
used to communicate the results of data processing carried out by
an information processing system(such as a computer) to the
What are Printers.....?
Printer are the most commonly used output devices that provides
the user with a permanent visual record of the output data in
human readable form known as hard copy. They can print on
plain paper or on specially prepared forms such as invoices,
labels, bills, checks and other special purpose forms used in
business. Their are several types of printers designed for wide
range of application.
Impact printer produces text and images when tiny
wire pins on print head strike the ink ribbon by
physically contacting the paper.
Non Impact Printers
Non-impact printer produces text and graphics on
paper without actually striking the paper.
Impact vs. Non-impact
Impact - These printers have a mechanism that touches the paper in order to create
an image. There are two main impact technologies:
Dot matrix printers use a series of small pins to strike a ribbon coated with ink, causing
the ink to transfer to the paper at the point of impact.
Character printers are basically computerized typewriters. They have a ball or series of
bars with actual characters (letters and numbers) embossed on the surface. The appropriate
character is struck against the ink ribbon, transferring the character's image to the paper.
Character printers are fast and sharp for basic text, but very limited for other use.
Non-impact - These printers do not touch the paper when creating an image. Inkjet
printers are part of this group, which includes:
Inkjet printers, which are described in this article, use a series of nozzles to spray drops of
ink directly on the paper.
Laser printers, covered in-depth in How Laser Printers Work, use dry ink (toner), static
electricity, and heat to place and bond the ink onto the paper.
Dot Matrix refers to the way the printer creates characters or images on paper. This
is done by several tiny pins, aligned in a column, striking an ink ribbon positioned
between the pins and the paper, creating dots on the paper. Characters are
composed of patterns of these dots by moving the printhead laterally across the
page in very small increments.
Print letters in italics or bold
Used to print carbon copies
An old line printer technology that used formed character images
around a cylindrical drum as its printing mechanism. When the desired
character for the selected position rotated around to the hammer line,
the hammer hit the paper from behind and pushed it into the ribbon
and onto the character.
Impact Printer - Print head has 9 or 24 pins
Pins strike paper through a ribbon.
24 pins give better print quality – dots closer
NLQ (Near Letter Quality) obtained by printing each
line twice, which second pass slightly displaced so as to
fill any spaces.
Printers are often bi-directional
Colour possible via 4-colour ribbon – but quality not too
Can be very noisy
Working of Drum Printer
Fixed font character set is engraved onto number of print wheels
The wheels, joined to form a large drum, and spin at high speed and paper and an
inked ribbon are stepped (moved) past the print position
The hammer pushes the paper into the type slug when it rotated around to the proper position. Such printer technologies seem
ridiculous compared to the quiet, high-speed workings of today's laser printers
Use Less Ink
An early line printer that used type slugs linked together in a chain as its
printing mechanism. The chain spins horizontally around a set of hammers.
When the desired character is in front of the selected print column, the
corresponding hammer hits the paper into the ribbon and onto the character
in the chain. Chain and train printers gave way to band printers in the early
Working of Chain Printers
Chain printers (also known as train printers) placed the type on moving bars (a
horizontally-moving chain). As with the drum printer, as the correct character
passed by each column, a hammer was fired from behind the paper. By selecting
chains that had a smaller character set (for example, just numbers and a few
punctuation marks), the printer could print much faster than if the chain
contained the entire upper- and lower-case alphabet, numbers, and all
special symbols. This was because, with many more instances of the numbers
appearing in the chain, the time spent waiting for the correct character to
"pass by" was greatly reduced. IBM was probably the best-known chain
printer manufacturer and the IBM 1403 is probably the most famous example
of a chain printer.
Daisy Wheel Printers
Daisy wheel printers use an impact printing technology invented in 1969 by
David S. Lee at Diablo Data Systems. It uses interchangeable pre-formed
type elements, each with 96 glyphs, to generate high-quality output
comparable to premium typewriters such as the IBM "Golfball" Selectric,
but three times faster. Daisyand-wheel printing was used in electronic
typewriters, word processors and computer systems from 1972.
Working of Daisy Wheel Printer
The heart of the system is an interchangeable metal or plastic "daisy
wheel" holding an entire character set as raised characters moulded on
each "petal". Daisy Printer use a servo motor rotates the daisy wheel to
position the required character between the hammer and the ribbon. The
solenoid-operated hammer then fires, driving the character type on to
the ribbon and paper to print the character on the paper. The daisy wheel
and hammer are mounted on a sliding carriage similar to that used by dot
Different typefaces and sizes can be used
Possible to use multiple fonts
Bold type facility
Electrostatic printers use a special photographic paper that allows
characters to be etched onto the paper using a stylus. The stylus, made up of
tiny wires, forms characters by
placing an electrostatic charged image on the paper. Then, as the paper
is moved through a toner solution containing ink particles, the ink adheres
to the charges that form a pattern on the paper to develop the character.
This type of printer can be used for both printing and plotting (displaying
graphic output), and can print up to 5,000 lines per minute
Types of Non Impact Printers
Non Impact Printer’s
Inkjet printers are non-impact printers which print text and images by
spraying tiny droplets of liquid ink onto paper. They are the most popular
printers for home use.
The inkjet head design is also divided into two main groups: fixed-head and
disposable head. Fixed-head is built into the printer and should last for the
whole life of the printer. It produces more accurate output than cheap
disposable head. The ink cartridges for fixed head printers are also cheaper
as the print head does not need to be replaced. However, if the head is
damaged, the entire printer has to be replaced.
Very popular – often bundled with PC
Cheap with very good resolution, particularly on special
Droplets of ink are fired at the paper
Large areas of colour may get the page too wet unless
special paper is used
Colour printing can be quite expensive
Advantages of inkjet printers
High quality of output, capable of printing fine and smooth details
Capable of printing in vivid color, good for printing pictures
Easy to use
Quieter than dot matrix printer
No warm up time
Disadvantages of inkjet printers
Print head is less durable, prone to clogging and damage
Expensive replacement ink cartridges
Not good for high volume printing
Printing speed is not as fast as laser printers
Ink bleeding, ink carried sideways causing blurred effects on some
Aqueous ink is sensitive to water; even a small drop of water can cause
Cannot use highlighter marker on inkjet printouts
Laser printers are non-impact printers which can print
text and images in high speed and high quality
resolution, ranging from 600 to 1200 dpi.
Unlike inkjet printers, laser printer use toner (black or
colored powder) instead of liquid inks
Working of Laser Printer
A laser printer consists of these major components: drum cartridge,
rotating mirror, toner cartridge and roller. The drum cartridge rotates as
the paper is fed through. The mirror deflects laser beam across the surface
of the drum. Laser beam creates charge that causes the toner to stick to
the drum. As the drum rotates and presses on paper, toner is transferred
from the drum to paper, creating images. Rollers then use heat and
pressure to fuse toner to paper. Colored laser printers add colored toner in
three additional passes.
High print speed
Low cost per page (compared to inkjet printers)
Printout is not sensitive to water
Good for high volume printing
More expensive than inkjet printers
Except for high end machines, laser printers are less
capable of printing vivid colors and high quality
images such as photos.
The cost of toner replacement and drum replacement
Bulkier than inkjet printers
Warm up time needed
Factors affecting choice
Volume of output
High volume require fast, heavy-duty printer
Quality of print required
Location of printer
Are multiple copies required?
Is colour required?