لخّصلي

Computer Basics
This chapter lays a foundation for one of the most influential forces available in
modern times, the computer. A computer is an electronic device, operating under
the control of instructions, which tells the machine what to do. It is capable of ac-
cepting data (input), processing data arithmetically and logically, producing output
from the processing, and storing the results for future use. The chapter begins with
the characteristics, evolution, and various generations of computers. The discus-
sion also explores the classification of computers and their features. The chapter
concludes with an overview on basic computer units and computer applications.
1.1 Introduction
In the beginning of the civilization, people used fingers and pebbles for computing
purposes. In fact, the word digits in Latin actually means finger and calculus
means pebble. This gives a clue into the origin of early computing concepts. With
the development of civilization, the computing needs also grew. The need for a
mechanism to perform lengthy calculations led to the invention of, first, calculator
and then computers
The term computer is derived from the word compute, which means to calculate.
A computer is an electronic machine devised for performing calculations and con-
trolling operations that can be expressed either in logical or in numerical terms. In
simple words, a computer is an electronic device that performs diverse opera-
tions with the help of instructions to process the data in order to achieve desired
results. Although the application domain of a computer depends totally on human
creativity and imagination, it covers a huge area of applications including educa-
tion, industries, government, medicine, scientific research, law, and even music
and arts.
Computers are one of the most influential forces available in modern times. Har-
nessing the power of computers enables relatively limited and fallible human ca-
pacities for memory, logical decision making, reaction and perfection to be ex-
tended to almost infinite levels. Millions of complex calculations can be done in
a mere fraction of time; difficult decisions can be made with unerring accuracy
for comparatively little cost. Computers are widely seen as instruments for fu- ture
progress and as tools to achieve sustainability by way of improved access to
information with the help of video-conferencing and e-mail. Indeed, computers
have left such an impression on modern civilization that we call this era as the
“information age”.
1.1.1 Characteristics of Computers
The human race developed computers so that it could perform intricate operations,
such as calculation and data processing, or simply for entertainment. Today, much
of the world’s infrastructure runs on computers and it has profoundly changed our
lives, mostly for the better. Let us discuss some of the characteristics of comput-
ers, which make them an essential part of every emerging technology and such a
desirable tool in human development.
Speed: The computers process data at an extremely fast rate, at millions or
billions of instructions per second. A computer can perform a huge task in
a few seconds that otherwise a normal human being may take days or even
years to complete. The speed of a computer is calculated in MHz (mega-
hertz), that is, one million instructions per second. At present, a powerful
computer can perform billions of operations in just one second.
• Accuracy: Besides the efficiency, the computers are also very accurate. The
level of accuracy depends on the instructions and the type of machines being
used. Since the computer is capable of doing only what it is instructed to do,
faulty instructions for data processing may lead to faulty results. This is
known as Garbage In Garbage Out (GIGO).
• Diligence: Computer, being a machine, does not suffer from the human traits
of tiredness and lack of concentration. If four million calculations have to be
performed, then the computer will perform the last four-millionth calculation
with the same accuracy and speed as the first calculation.
• Reliability: Generally, reliability is the measurement of the performance of
a computer, which is measured against some predetermined standard for op-
eration without any failure. The major reason behind the reliability of the
computers is that, at hardware level, it does not require any human interven-
tion between its processing operations. Moreover, computers have built-in
diagnostic capabilities, which help in the continuous monitoring of the sys-
tem.
• Storage Capability: Computers can store large amounts of data and can
recall the required information almost instantaneously. The main memory of
the computer is relatively small and it can hold only a certain amount of data;
therefore, the data are stored on secondary storage devices such as magnetic
tape or disks. Small sections of data can be accessed very quickly from these
storage devices and brought into the main memory, as and when required,
for processing.
• Versatility: Computers are quite versatile in nature. It can perform multiple
tasks simultaneously with equal ease. For example, at one moment it can be
used to draft a letter, another moment it can be used to play music and in
between, one can print a document as well. All this work is possible by
changing the program (computer instructions).
• Resource Sharing: In the initial stages of development, computers used to
be isolated machines. With the tremendous growth in computer technologies,
computers today have the capability to connect with each other. This has
made the sharing of costly resources like printers possible. Apart from device
sharing, data and information can also be shared among groups of computers,
thus creating a large information and knowledge base.
Although processing has become less tedious with the development of computers,
it is still a time-consuming and expensive job. Sometimes, a program works
properly for some period and then suddenly produces an error. This happens
because of a rare combination of events or due to an error in the instruction provided
by the user. Therefore, computer parts require regular checking and maintenance in
order to give correct results. Furthermore, computers need to be installed in a dust-
free place. Generally, some parts of computers get heated up due to heavy
processing. Therefore, the ambient temperature of the computer system should be
maintained.