computer science

1. 1

2. What is a computer?
 A computer is a machine that is
controlled by internally stored
programmers and that can perform
operations without human intervention
 It is a collection of hardware and software
components
 The hardware parts consist of one or
more processing units, memory units,
and input and output devices
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3. Cont…
 Hardware part is the equipment you see
and the parts you can touch
 The Software is the set of instructions,
called a program, which tells the computer
what to do, when and how to do it.
 Inventers (mathematicians or physicists)
were initially invent computers for making
calculations only.
 But today’s computers not only process
numbers, they process texts, pictures,
multimedia and so on.
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4. Cont…
 Therefore, the meanings of the computer,
nowadays, are broader than computing
concepts.
 In general, computer is an electronic device;
Operating under the control of instructions
stored in its own memory unit and that can
accept data, process data, produce output
and store the results for future use
 So a computer is a programmable electronic
machine capable of accepting data,
processing, storing and then displays the
output to the user
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5. 2. Characteristics of
computers
 Automatic: once a program is in the
computer’s memory, it continues without
the need for human intervention until
completion. Or once started on a job, they
carry on until the job is finished.
 Speed: a computer is a very fast device.
Units of time are ms(10-6 second), ns(10-9
second) or even picoseconds (10-
12second). A powerful computer is capable
of performing several billion (109) simple
arithmetic operations per second.
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6. Cont…
 Accuracy: The computer’s accuracy is
consistently high.
 Almost without exception, the errors in computing are
due to human rather than to technological weakness,
that is to in correct programming, or to inaccurate
data or to poorly designed systems.
 Storage capacity: computer can store large
amount of data.
 For example data stored on paper that filled the
shelves of a registrar office can be stored in a single
computer with larger storage capacity.
 This saves space, money to buy paper, ink and
shelves. This also helps to have backup (copy) of the
data and put it somewhere else for security purpose
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7. Cont…
 Diligence: unlike human beings, a computer
is free from boredom, tiredness, lack of
concentration, etc, and hence can work for
hours without creating any error and without
grumbling.
 Versatility: A computer is capable of
performing almost any task provided that the
task can be reduced to a series of logical
steps.
 Power of remembering: a computer can
store and recall huge amount of information
because of its secondary storage capability.
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8. Cont..
 No IQ: a computer can only perform tasks
that a human being can.
 But it can do tasks with unthinkable speed and
accuracy.
 Its IQ is zero.
 It has to be told what to do and in what sequence.
 Hence, only the user can determine what tasks a
computer will perform.
 No feeling: computers are devoid of
emotion.
 They have no feelings and no instincts because
they are machines.
 Computers can not make judgment on their own.
 Their judgment is based on the instructions given
to them in the form of programs that are written by
us
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9. Cont…
 Reliability: computers are used in sensitive areas that need
very high reliability.
 For example hospitals are using computers in patient
diagnosis, monitoring patient operations.
 They are also monitoring activities in industries that may
cause failure or success of the company.etc.
 Resource sharing: by connecting computers each other resource
sharing is achievable in the computer system. E.g. printer
 Flexibility: a computer is a versatile machine.
 It is difficult to find an area where computers are not
being used.
 All other machines like television or a typewriter do the
one thing they are designed for.
 Unlike such machines, a computer can be used to play
music, watch films, type letters, send faxes, diagnose
illness, design buildings and bridges, etc…
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10. Application of computers
 Science: scientists have been using
computers to develop theories, to analysis,
and test the data.
 The fast speed and the accuracy of the computer
allow different scientific analysis to be carried out.
E.g. detail study of how earth quakes affect
buildings or population affect weather pattern,
satellite based application.
 Education: computers have also
revolutionized the whole process of education.
 Currently, the class room, libraries, and museums
are effectively utilizing computers to make the
education much more interesting. 10

11. Cont…
 Medicine and health care: now doctors are
using computers right from diagnosing the
illness to monitoring a patient’s status during
complex surgery.
 Engineering : the architects and engineering
are extremely using computers in designing and
drawings.
 By using the techniques like virtual reality architects
can explore houses that have been designed.
 Entertainment: computers are used to control
the images and sounds.
 The special effects, which mesmerize the audience,
would not have been possible without the computer.
 In addition, computerized animation and color full
graphics have modernized the film industry.
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12. Cont…
 Communication: E-mail or electronic mail is one
of the communication media in which computer is
used.
 Though e-mail the message and report are passed from
one person to one or more person by the aide of
computer and the telephone line.
 The advantage of this service is that while transferring
the message it save time, avoids wastage of paper, and
so on.
 Business application: There are various
concerns for which computer are used such as in
business applications (like at the sale counter)
that requires immediate response from computer.
 Other applications like business forecasting, to prepare
pay bills and personal record, in banking operation and
data storage, in the various types of life insurance
business, and as an aid to management.
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13. Cont…
 Publishing: computers have created a field
known as DTP (Desk Top Publishing).
 In DTP, with the help of computer and laser printer
one can perform the publishing job all by oneself.
 Banking: in the field of banking and
insurance computers are extensively used.
 People can use the ATM (Automatic Teller
Machine) services 24 hours of the day in order to
deposit and withdraw cash.
 Industries: - it is used for designing
products, assisting labors, controlling the
work of the machineries in factory e.t.c.
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14. 4. Limitation of computers
 Computers can’t decide how to be
programmed.
 It is always persons or humans that are
responsible for programming the computers.
 Computers can only perform what it is
programmed to do, nothing more and
nothing less.
 Computers don’t provide their own inputs
unless people provide it with the inputs.
 Interpretation of data and implementation
of decisions is always left for humans
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15. 5. Generation of
computers
 All modern computers can be
categorized in to five generation based
on the following five dimensions:-
Basic electronic component used by the
computer
Secondary storage device used
Operating system
Access time of the computer
Computer language used.
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16. Cont…
 The most common improvements which
are made from one generation to next.
 Enhanced power in terms of speed
processing data, storage
 More Convenient to use
 Better reliability
 Reduced physical size & loss Expensive
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17. First generation
This generation of computer is characterized by:
 It uses vacuum tubes as main component
 It is very big ,expensive & slow
 It required expensive air condition
 It generates large heat
 It uses magnetic drums for memory
 It is very expensive to operate.
 It uses machine language to perform
operation.
 It uses punched cards and paper tape for
input purpose.
 Output was displayed on printouts.
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18. Second generation
 it uses transistor instead of vacuum tubes
 B/c of the transistors, the computer
becomes smaller in size, fast in speed &
more reliable than 1st generation.
 It uses punched cards for input and
printouts for output
 It controls by Assembly programming
language
 Magnetic tape is introduced for data
storage
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19. Third generation
 integrated circuits(IC) called chips are
replaced to transistor.
 IC is a collection of transistor.
 Transistors were placed on silicon chips
called Semiconductors.
 Because of IC, Computers became:-
Smaller in size & power requirement
Very fast & more reliable
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20. Cont…
Magnetic disk is replaced to magnetic tape
storage device.
It uses keyboard instead of punched cards.
It uses monitors instead of printout.
It uses operating system which allows the
computer to run many applications at one
time with a central program that monitored
the memory.
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21. Fourth generation
 This generation of computer is
Characterized by:-
It uses Microprocessor replaces
Integrated Circuit.
Thousands of Integrated Circuits are
built onto a single silicon Chip.
Cheaper in price
More powerful
Efficient &reliable
It uses Graphical user interface and
mouse.
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22. Fifth Generation
 It uses an artificial intelligence & interact
with the natural language
 The main goal is to narrow the gap
between human being and computer.
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23. What is Information?
 It is a collection of meaningful facts and
figures that can be used as a base for
guidance and decision-making
 Any fact or figure is not necessarily
information
 To call it information, it has to be useful
and meaningful for you (individual,
group, organization, or society)
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24. Cont…
 Information can also be defined as
something that someone did not know
before.
 Information is something that
reduces uncertainty.
 Information is a processed data.
 Information is a clue.
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25. Assignment I
1. Describe the three main types (primary,
secondary and tertiary) of
documentary Sources of information
2. What are Non-Documentary Sources of
information?
3. List and explain characteristics of
information
4. What is technology and Information
Technology?
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26. Types of computers
classifications
 Computers can differ based on their
data processing abilities.
 Hence, computers can be classified
according to purpose, data handling,
and functionality
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27. Cont…
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28. Computers classification according to
purpose
1. General purpose
 Design to perform a range of tasks
 These computers have the ability to store
numerous programs
 These machines can be used for various
applications, ranging from scientific as well
as business applications.
 Even though such computers are versatile,
they generally lack in speed and efficiency.
 Computers that you use home and schools
are general purpose computers
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29. Cont…
2. Specific purpose
 Design to handle a specific problem or to
perform a single specific task built into the
machine.
 They lacked versatility
 Since they are designed for specific tasks;
they can be providing the result very
quickly and effectively.
 These computers are used for airline
reservation, satellite tracking, and air traffic
control.
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30. Classification of computers according
to the method of operation
1. Analog computers - are operate by
measuring.
 They deal with continues variable.
 They do not compute directly with numbers,
rather, they operate by measuring physical
magnitude such as pressure temperature,
voltage, current and etc.
 Analogue computer measures continuous
types of data and uses physical quantities
such as electric current.
 E.g. Thermometer, voltmeter, speedometer
 Generally, they are computers designed for
special purpose.
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31. Cont…
2. Digital Computers- deal with discrete
variables.
 They operate by counting rather than
measuring.
 They operate directly upon numbers (or digits)
that represent numbers, letters, or other
special symbols.
 Digital computer is a computing device in
which data is represented by discrete
numerical quantities.
 It is represented by discrete voltage states (0s
and 1s)
 E.g. Personal Computers
 They have very high accuracy and speed than
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32. Cont…
3. Hybrid Computers
 The combination of analog and digital
computers.
 It processes the information by collecting
input data with analog method, converts
it into digital quantities, processes the
digital values and converts the output
from digital to analog form.
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33. Classification of computers
according to functionality
 Based on the functionality (size, speed,
cost and performance) we can divide
digital computers in to four categories.
1. Microcomputers
2. Minicomputers
3. Mainframe computers
4. Supercomputer
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34. Microcomputers
 Microcomputer (PCs ) are the smallest but
most important and most frequently used of
computer particularly for end users.
 They are relatively small or compact in size
and are often found on a tabletop or
desktop
 Microcomputers come in a variety of sizes
and shapes for a variety of purposes.
 Basically they can be grouped into three:
 Laptop
 Palmtop
 Desktop
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35. Cont…
 Laptop: are smaller versions of
microcomputers about the size of a
briefcase designed for portability
 People can easily carry these personal
computers with them in their car, on
airplane, or when walking from one location
to another.
 Unlike desktop PCs that have mostly
detachable components, laptops include all
their components (except their printer) in a
single unit
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36. Cont…
 Palmtop: is the smallest microcomputer
that is about the same size as a pocket
calculator.
 It is the most portable computer and is
growing in popularity among the latest
entries in the microcomputer market.
 Palmtops are typically used from a
limited number of functions, such as
maintaining personal calendar, name
and address files, or electronic
worksheets.
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37. Cont…
 Desktop: Desktop computer is the most
widely used type of personal computer.
 Unlike laptop and personal computers,
desktop computers have detachable
parts.
 However, since its size is larger than
the other types of personal computers, it
is not easily portable.
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38. Cont…
 Generally , microcomputers are used
for
 Word processing to prepare letters, reports,
memos and other documents.
 Computerized worksheet analysis and
modeling.
 Graphics in the generation of charts and other
graphic images.
 Engineering activities
 Personal and home use.
 Entertainment, home management, personal
finances, education, and other activities can
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39. Minicomputers
 Minicomputers are midrange computers
that are larger and more powerful than
most microcomputers but are smaller
and less powerful than mainframe
computer systems.
 The minicomputers size prevents it from
being easily portable although it can be
moved more easily than a mainframe
computer.
 Minicomputers cost less to buy and
maintain than mainframe computers.
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40. Cont…
 Most minicomputers can function in
ordinary operating environments, as they
do not need special air conditioning or
electrical wiring.
 Minicomputers are being used for a large
number of business and scientific
applications.
 They are popularly used in scientific
laboratories, research centers, universities
and colleges, engineering firms, industrial
process monitoring and control etc.
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41. Mainframes
 Mainframe computers are large,
powerful computers that are physically
larger than micros and minis and
usually have processors with faster
instruction processing speeds.
 For example, they may be able to
process from 10 to 200 million
instructions per second (MIP).
 A mainframe computer is generally
found in a special computer room
where environmental factors such as
temperature, humidity, dust and air
conditions are closely monitored.
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42. Cont…
 Since they are costly, authorized personnel are
only enter to the location room.
 Mainframe computers are designed to handle
the information processing need of
organization with many employees and
customers or with complex computational
problems.
 For example, mainframes can handle the
processing of thousands of customer inquiries,
employee paychecks, student registrations,
sale transactions, and inventory changes.
 They are also used as the center of computer
networking.
 These computers are used by organizations
that have enormous and complex data
processing assignments.
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43. Supercomputer
 A supercomputer is characterized as the
fastest, most powerful, and most expensive
computer
 As many as sixty miles of wiring are closely
packed inside supercomputers, and
tremendous amounts of heat are
generated.
 Because of this, supercomputers demand
special cooling requirement and the room
itself should be air-conditioned.
 Some supercomputers require extra floor
support to hold the extreme weight of the
complete system that includes storage
units. 43

44. Cont…
 In addition, highly trained data processing
professionals are required to operate
supercomputers.
 These computers can take inputs from over
10,000 individual computers and users at
the same time.
 Super computers are largely used by
research organizations, military defense
systems, national weather for casting
agencies, large corporations, aircraft
manufacturer, etc.
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