Higher medical and business- technological
school of applied studies Sabac
Profile: Information technologies
SEMINARY WORK FROM THE SUBJECT THE ENGLISH
LANGUAGE
External devices of the computer system
Students: Nebojsa Trifunovic
Zoran Simic
Professor:
Ana Matić
Sabac, April 2018
Introduction
External devices of PC computers are called peripheral devices because they are located at the
periphery i.e. outside of the computer’s processor. They enable users to receive processing
results performed by the computer, while other computers use these results for additional work.
Inserting of the large amount of data in the computer will not be very useful unless we have
opportunity to find out results of its processing by some external device. Most common external
devices are monitor and printer. Monitors and graphic cards display text, graphics and images,
while LCD-panels are more and more used for public presentations. Quality graphic cards can
also display video clips on monitors. We can use printers to print text and graphics, from ready-
made pictures to professional engineering blueprints. Some peripheral devices such as
fax/modem can be either internal or external devices because they can both receive and send
data. Speakers are becoming standard part of multimedia computers which can reproduce
music, human voice or speech synthesis.
Monitors
Monitor or screen is an electric external device for displaying images sent from another
device, usually from graphic card in the computer. On monitor we can track results of data
processing and current activities. Its purpose is to display letters or images which can be
moving or steady. The image usually displayed on monitor is created in graphic card, special
structure with the function of creating and recovering images. There are several different
technologies used for monitors. Based on applied technology we shall present the following
types of monitors:
1.
Cathode Ray Tube Monitors
(CRT)
2.
Liquid Crystal Display Monitors
(LCD)
3.
Plasm monitors
(ionized gas)
CRT monitors
This type of monitor possesses so-called cathode or vacuum tube. On one side of this tube
there is a screen that is coated with phosphorus and on the other side is the neck
with
electronics. Electronics emit the rays of electrons which collide with phosphorus, creating the
light of specific color, and the collection of those lights represents the image. Basic
characteristics are frequency and space between pixels, i.e. spots which are expressed in
