Page 71 - DCAP101_BASIC_COMPUTER_SKILLS

Basic Computer Skills

Notes Laser printers produce very high quality output because they form characters by very tiny
ink particles. The most -common laser printers have resolution of 600 dpi (dots per inch),
whereas some high-end laser printers have resolution. of 1200 dpi. Due to their high
resolution, these printers give excellent graphics art quality.
Since laser printers produce printed output as patterns generated by the laser beam, they can
print any shape of characters that a program can describe. They, therefore, can print many
special characters, different sizes of print, : also have the ability to print graphics such as
charts and graphs.

Laser printers are non-impact printers. Hence, they are very quiet in operation. Being of
non-impact type, they can not be used to produce multiple copies of a document in a single
printing.
Although most laser printers can print in black color only because they have a single toner-
drum arrangement, now even color laser printers are available at affordable price. A color
laser printer like color inkjet printer four color toners, each with a drum of its own. The
usage of drums and toners are same as earlier, but drum is charged in such a way that
together they produce the desired color output.
Laser printers are faster in printing speed than other printers discussed earlier. Low speed
laser printers can print 4 = pages per minute. High-speed laser printers are also available.
Owing to their better print quality and printing speed, laser printers are more expensive
than other types of printers.
4.2.2.4 Plotters

We learnt earlier that dot matrix, inkjet, and laser printers are capable of producing
graphics output. However, engineering design applications like architectural plan of a
building, design of mechanical components of an air craft or a car etc., often require high-
quality, perfectly-proportioned graphic output on large sheets. The various: types of
printers discussed above are not suitable for meeting this output requirement of such
applications. A special type of output device, called plotters, is used for this purpose.
Plotters are an ideal output device for architects, engineers, city planners, and others who
need to routinely generate high-precision, hard-copy, graphic output of widely varying
sizes. ‘Two commonly used types of plotters are drum plotter and flatbed plotter. They
are described below:

Drum Plotter
In a drum plotter, the paper on which the design is to be made is placed over a drum that
can rotate in both clockwise and anti-clockwise directions to produce vertical motion. The
mechanism also consists of one or more penholder mounted perpendicular to the drum’s
surface. The pen(s) clamped in the holder(s) can move left to or right to left to produce
horizontal motion. A graph-plotting program controls the movements of the drum and
pen(s) that is, under computer control, the drum and pen(s) move simultaneously to draw
designs and graphs; sheet placed on the drum. The plotter can also annotate the designs
and graphs so drawn by using the pen to draw characters of various sizes. Since each pen
is program selectable, pens having ink of different colors can be mounted in different
holders to produce multi-colored designs. Figure 4.22 shows a drum plotter.

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