Output Devices
An output device is any hardware device that makes information from a computer available to the user.
A computer produces output using the combination of output devices, media, and software available
with a particular system. Some output devices include monitors and printers.
Monitors
A monitor is fundamental component of a computer system and is the most common soft copy output
mechanism for displaying text, images, graphics, and video on a screen. Available in a variety of shapes,
sizes, costs, and capabilities, monitors allow users to view information temporarily.
CRT Monitor
One type of monitor for desktop computers is the cathode ray
tube (CRT) monitor (see Figure 1). A CRT is a large, sealed glass
tube housed in a plastic case. The front of the tube is the screen. A
cable at the rear of the monitor plugs into a graphics adapter
board on the motherboard inside the system unit. An electric cord
on the monitor plugs into an electrical outlet. CRT monitors use
the same cathode ray tube technology used in television sets, so
most are fairly large and bulky.
Flat-Panel Monitor
Flat-panel displays use a technology that allows them to be smaller,
thinner, and lighter than CRT monitors (see Figure 2). An additional benefit
of these lightweight compact screens is that they consume less power
compared to CRT monitors. The majority of flat-panel displays use liquid
crystals to produce information on the screen. In a liquid crystal display
(LCD), liquid crystals are sandwiched between two sheets of material.
Electric current passing through the crystals causes them to twist. This
twisting effect blocks some light waves and allows other light waves to pass
through, creating image on the screen.
Printers
A printer is the most common type of device for producing hard-copy output on a physical medium,
such as paper or transparency film. Almost all printers are capable of printing in either portrait or
landscape format. In portrait format, a printed page is taller than it is wide. Portrait format is usually
used for letters, memos, reports, and newsletters. In landscape format, a printed page is wider than it is
tall. Landscape format is best suited for financial spreadsheets and other types of tabular reports. Two
types of printers include ink-jet printers and laser printers.
Ink-Jet Printers
An ink-jet printer is a nonimpact printer that forms characters and
images by spraying thousands of tiny droplets of electrically charged
ink onto a sheet of paper as the sheet passes through the printer (see
Figure 3). Most ink-jet printers use two or more ink cartridges, one for
black print and one or more for color printing. Each cartridge has
multiple holes, called nozzles. During printing, combinations of tiny ink
droplets are propelled through the nozzles by heat and pressure onto
the paper, forming characters and images.
Laser Printers
A laser printer is a nonimpact printer that produces output of exceptional quality using a technology
similar to that of a photocopy machine. Laser printers are used for any printing application, including
those requiring output of printing-press quality material (see Figure 4). Their speed and ability to
produce clear, crisp text and images have made them the fastest growing segment of the printer
market. A laser printer creates text and graphics on a rotating metal drum using a laser beam. During
printing, components inside the printer read characters and relay them to a printer device called a laser
mechanism. A laser beam produces characters and
images on a rotating drum inside the printer by
altering the electrical charge wherever the beam
strikes the drum. The charges produce tiny
magnetic fields (dots) on the drum, forming
characters. As the drum rotates, it picks up an inklike powder called toner, similar to copy machine
toner. The sensitive dots on the drum are then
deposited onto the paper. Using heat and pressure,
a set of rollers fuses the toner onto the paper,
forming the printed image.