Page 68 - DCAP101_BASIC_COMPUTER_SKILLS

Unit 4: Secondary Storage Devices

Notes
Figure 4.18: An Inkjet Printer

Inkjet printers produce higher quality output than dot-matrix printers do because they form
characters by very tiny ink dots. A high-resolution inkjet printer has as many as 64 nozzles
within a height of 7mm’providing print resolution of around 360 dots per inch.
Since inkjet printers produce printed output as patterns of tiny dots, they can print any shape
of characters that a program can describe. This allows the printer to print many special
characters, different sizes of print, and the ability to print graphics such as charts and graphs.
Inkjet printers are non-impact printers because they print by spraying ink on the paper.
Hence, they are quieter in operation. Being of non-impact type, they cannot be used to
produce multiple copies of a document in a single printing. A color inkjet printer usually
comes with two ink cartridges—black and tri-color. The tri-color cartridge contains red, blue,
and yellow colors in a package that can mix appropriate amount of these colors with black
from the other cartridge to get any desired color with saturation. This makes it possible to
get multi-colored and photo quality output from inkjet printers.
Inkjet printers are slower than dot-matrix printers are with printing speeds ranging from
40 to 300 characters per second. Typically, an inkjet printer is more expensive than a dot-
matrix printer. They are preferred if speed of printing is not an important factor.

Drum Printers

Drum printers are line printers that print an entire line at a time. Recall that dot matrix and
inkjet printers print one character at a time. Figure 4.19 shows the print mechanism of a
drum printer. It consists of a solid cylindrical drum with characters embossed (raised
characters) on its surface in the form of circular bands. Each band consists of all the printing
characters supported by the printer in its character set. Total number of bands is equal to
the maximum number of characters (print positions) that can be printed on a line. Hence,
a drum printer with 132 characters per line and supporting a character set of 96 characters
will have altogether 12,672 (132 x 96) characters embossed on its surface.

In addition to the drum, the printer has a set of hammers (one opposite each band) mounted
in front of the drum in a manner that an inked ribbon and paper can be placed between the
hammers and the drum. The total number of hammers is equal to the total number of bands
on the drum, which is also equal to the total print positions per line.

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