Introduction to Computers and windows operating system.pdf

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Introduction to Computers & Windows Operating system
Introduction to Computers: Computers are one of the biggest technical
developments of the 19th century. Computer are not only used by scientists or
engineers, it is popular today with all kinds of people from businessmen to employee
or school going children. Unlike the development of other areas of scientific and
technical , the computer science has grown up at very rapid. Today the computers are
household name.
The human brain is the most sophisticated asset of humanity and has been
blessed by god. The computers are the most versatile machine the human has ever
discovered. It is the most intelligent representative to man’s intelligence and wisdom.
Computers are not to replace the human intelligence and memory but to assist him to
reduce burden on his memory. Computers have come to assist humanity in his task
like collecting, memorizing and analyzing the large amount of information.
Computers are machines that perform tasks or calculations according to a set of
instructions, or programs. The first fully electronic computers, introduced in the 1940s,
were huge machines that required teams of people to operate. Compared to those
early machines, today's computers are amazing. Not only are they thousands of times
faster, they can fit on your desk, on your lap, or even in your pocket.
Computers work through an interaction of hardware and software. Hardware refers to
the parts of a computer that you can see and touch, including the case and everything
inside it. The most important piece of hardware is a tiny rectangular chip inside your
computer called the central processing unit (CPU), or microprocessor. It's the
"brain" of the computer—the part that translates instructions and performs
calculations. Hardware items such as your monitor, keyboard, mouse, printer, and
other components are often called hardware devices, or devices.
Software refers to the instructions, or programs, that tell the hardware what to do. A
word-processing program that you can use to write letters on your computer is a type
of software. The operating system (OS) is software that manages your computer and
the devices connected to it. Windows is a well-known operating system.
What is a Computer?
“It is an electronic calculating machine, capable
of accepting input signals (Data), performing
mathematical and logical operation(Process)
as per stored program and supplies output
signal(Result)”
Basic functions performed By a Computer
All computers performs following 3 functions
a) It performs arithmetic calculation such as addition, subtraction, multiplication
and division.

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b) It compares the values
c) It sores , searches , retrieves any information at any time
All the computers do all the above function automatically but it does not posses
any intelligent of its own. Its intelligent quotient is Zero(0) . It does not have any
thinking, decision making power of its own. This power can be intelligently feed
to it by proper programming methods.
Types of Computers.
1. Analog Computer
Analog means establishing similarities between two quantities. In analog
computers similarities are established in the form of current or voltage signals. Analog
computers operates by measuring not by counting.
“A computer that operates on data which is in the form of continually variable
physical quantities is called Analog Computer”.
Analog computers are primarily used to measure continuous physical
magnitude such as electric current, speed, temperature, pressure, voltage etc. These
computers gives an approximate result. Therefore these computers are used in
engineering and scientific application only.
Example : thermometer, Slide ruler, Speedometer, Voltmeter, ammeter, millimeter
2. Digital Computers
“ A computer which uses data to its operation which are in the form of digits is called
digital Computers.
It understands information only in the form of digits i.e. 0 & 1. These two numbers are
called as Binary Digits (BITS). The digital computers are more accurate than analog
computers. They are best suited for business, engineering and scientific application.
Digital computers are further categorized into 2 types
Computer
Analog
Computer
General purpose
Computer
Digital
Computer
Hybrid
Computer
Special purpose
Computer

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a) Special Purpose Computers
b) General Purpose Computers
Special Purpose Computers
These computers are designed to solve special type of problems. The computers
used in ships and aircraft etc. It can be used for other application when their circuits
are redesigned. These computers are not programmed. These computers used in
telephone booths, general stores, hotels, buses, KEB to print the bills.
General Purpose Computers
These computers have capability to perform variety of operation. These computers
are programmable machines. It can store different programs. Present day computers
are general purpose computers.
Hybrid computers
A hybrid computers is combination of both analog and digital computer. Hybrid
computer can handle both analog and digital data. A hybrid computer combines the
characteristics of both the analog and digital computer. It can accept data in both
analog and digital form. Hybrid computers are used in hospitals that may calculate
patient’s heart function, temperature and blood pressure etc. This calculation can be
converted into numbers Hybrid computers are also used in spaceships and missile
system.
Classifications of computes
We measure computers processing speed in terms of seconds. We can use the terms
Millisecond, Micro second, Nano second and Pico second.
Millisecond = 10-3 = 1/103 = 1/1000
Micro Second = 10-6 = 1/106 = 1000000
Nano Second = 10-9 = 1/109 = 1000000000
Pico Second = 10-12 = 1/1012 = 1000000000000
We measure the size of computer memory or data in terms of bytes. We can use the
term Kilobytes(KB), Megabytes(MB), Gigabytes(GB), Terabytes(TB) ,Petabytes
bytes(PB)
1KB = 103 = 1000 Bytes
1MB = 106 = 1000000 Bytes
1GB = 109 = 1000000000 Bytes
1TB = 1012 = 1000000000000 Bytes
1PB = 1015 = 1000000000000000 Bytes

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The digital Computers are classified on the basis of size, speed, purpose,
performance, computing power, memory capacity, cost and component used as
Micro Computers or Personal computer
Mini computer
Mainframe Computer
Super Computer
Micro Computers
Micro Computer is also called personal computer. It was introduced in 1970. It
is miniature in size and it uses microprocessor as main component It is the smallest
general purpose computer. These computers are basically designed for single user
system. These computers are also called personal computers or Desktop computers.
Computers range in size and capability. At one end of the scale are
supercomputers, very large computers with thousands of linked microprocessors
that perform extremely complex calculations. At the other end are tiny computers
embedded in cars, TVs, stereo systems, calculators, and appliances. These
computers are built to perform a limited number of tasks.
The personal computer, or PC, is designed to be used by one person at a time. This
section describes the various kinds of personal computers: desktops, laptops,
handheld computers, and Tablet PCs.
Desktop computers
Desktop computers are designed for use at a desk or table. They are typically larger
and more powerful than other types of personal computers. Desktop computers are
made up of separate components. The main component, called the system unit, is
usually a rectangular case that sits on or underneath a desk. Other components, such
as the monitor, mouse, and keyboard, connect to the system unit.
Desktop computer
Laptops and netbooks
Laptops are lightweight mobile PCs with a thin screen. Laptops can operate on
batteries, so you can take them anywhere. Unlike desktops, laptops combine the CPU,
screen, and keyboard in a single case. The screen folds down onto the keyboard when
not in use.

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Netbooks (also referred to as mini notebooks), are small, affordable laptops that are
designed to perform a limited number of tasks. They're usually less powerful than
laptops, so they're used mainly to browse the web and check e-mail.
A laptop and a netbook
Smartphones
Smartphones are mobile phones that have some of the same capabilities as a
computer. You can use a smartphone to make telephone calls, access the Internet,
organize contact information, send e-mail and text messages, play games, and take
pictures. Smartphones usually have a keyboard and a large screen.
Smartphone
Handheld computers
Handheld computers, also called personal digital assistants (PDAs), are battery-
powered computers small enough to carry almost anywhere. Although not as powerful
as desktops or laptops, handheld computers are useful for scheduling appointments,
storing addresses and phone numbers, and playing games. Some have more
advanced capabilities, such as making telephone calls or accessing the Internet.
Instead of keyboards, handheld computers have touch screens that you use with your
finger or a stylus (a pen-shaped pointing tool).
Handheld computer
Tablet PCs
Tablet PCs are mobile PCs that combine features of laptops and handheld computers.
Like laptops, they're powerful and have a built-in screen. Like handheld computers,
they allow you to write notes or draw pictures on the screen, usually with a tablet pen

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instead of a stylus. They can also convert your handwriting into typed text. Some
Tablet PCs are “convertibles” with a screen that swivels and unfolds to reveal a
keyboard underneath.
Tablet PC
Mini Computers : Mini computers were introduced in the 1960s Mini computers is
larger and more powerful computer than personal computer. It can execute five million
instruction per second. It generally consists of two or more processor. Mimi computers
can serve up to 4000 connected users simultaneously. It is normally accessed by
users via personal computer or terminal. A device with a monitor and keyboard is
called terminal. It is also known as dumb terminal. It has no processing power and can
not work as stand alone computer.
Main Frame Computer: Mainframe computers were introduced in 1975. A mainframe
computer is a very large computer in size. It has multiple processors. It is designed to
perform multiple tasks for multiple users at the same time. Mainframes computers can
serve up to 50,000 users at the same time. The users access a mainframe computer
through terminal or personal computer. A typical mainframe computer can execute 16
million instructions per second. Example NEC 610, DEC 10. Mainframe computers are
used primarily by corporate and government organizations for critical applications such
as bulk data processing like senses, industry and consumer statistics.
Example VAX-8800 , AS-400. Mini computers are often used by small and medium
sized companies to provide centralized store of information.
Super Computer: Super computers were introduced in 1980. Super computer is the
fastest computer in the world. Super computer is the biggest in size and the most
expensive in price than any other computers. It is the most sophisticated, complex and
advanced computer. It has a very large storage capacity. It can process trillions of
instructions in one second. Super computer is the fastest and most powerful computer.
Super computer is the fastest and most powerful computer in the world. They are very
expensive and are used for highly calculation and intensive task. These computers
are also used for specialized applications that require immence amounts of
mathematical calculation. The modern super computer uses high speed facilities such
as satellite for online processing.
Application of Super Computer
 Weather forecasting

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 Animated graphics like in Hollywood movies
 Fluid dynamic calculations
 Nuclear energy research
 Space science
 Weapon and missile design
 Petroleum exploration etc.
Today supercomputers are produced by traditional companies such as Cray, IBM,
Hewlett-Packard. The Tianhe-1A super computer is the fastest super computer in the
world today and is located in china. CRAY-XP, ETA-10 PARAM & DEEP BLUE are
some of super computer names.
HISTORY OF COMPUTERS
The evolution of computer has passed through a number of stages before it reached
to the present stage. The development of computer has been undergone in
tremendous change. It has taken thousands of years to evolve from the use of sticks
to latest computer system. In early days performing a simple calculation on one’s
finger is well known example of computing. The efforts are still continuing to make the
machine more & more versatile.
One of the earliest computing mechanical devices was ABACUS. A
Chinese mathematician ABACUS invented a calculating instrument
that uses beads that strung on a series of rods. Counting is done by
shifting the beads.
In 1614 John Napier invented a
Calculation Device called Napier
Bone. In 1633 William Oughtred
invented a calculating device based on Napier’s theory called
Circles of proportion also called Slide Rule.
In 1640 Blaise Pascal invented Rotating wheel calculator
also called pascaline. His machine was simple calculator
used for addition and subtraction purpose. The machine
consists of gears, wheels and dials.
In 1972-1871 Charles Babbage invented Difference Engine
called as Analytical Engine. He used 4 Components in his
machines. 1) Input/output Device. 2) Storage Device 3) Control
Unit 4) Arithmetic & logical Unit. The same four components are
used in our present day computers. So Charles Babbage was
considered to be father of computer.

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After Charles in 19th Century Herman Hollered developed a
machine called Punched Card. This Machine used punched
cards to store and tabulates census data. This machine could
sense the punched holes, recognize the number and make the
required calculation. It had significant impact on future design
of computers. After World War II there was more need of
calculations. Realizing these needs, Howard Aiken with the
support of IBM developed a computer called Mark I.
Development of Electronic Calculating Device
The world's first digital computer was ENIAC(Electronic
Numeric Integrator And Calculator) developed by John
W Mouchly & Presper Eskert in 1943-1946 at
Pennsylvania University U.S.A. The ENIAC contained
18,000 Vacuum Tubes, 70.000 resistors, 10,000 capacitors
consumed 150 KW of power and occupied 15,000 sq. feet
of floor space, weighed 30 tons. The ENIAC processes
around 80,000 hours of work and performed 5,000 addition and subtraction, 300
multiplications per second. The main disadvantage of ENIAC was the beginning of the
First generation computers.
After that, the computers which were built on the basis of Binary code and stored
program suggested by Dr. John Von Neumann are given below
a) EDSAC (Electronic Delay Storage Automatic Computer). It was built by M.V.
Wilkes at Cambridge University in 1949
b) EDVAC (Electronic Discrete Variable Automatic Computer). It was built at
Pennsylvania University
c) LEO (Lyons Electronic Office). The First commercial Computer
d) UNIAC (Universal Automatic Computer)
In 1950 there was beginning of takeover of
computer manufacturing by commercial
companies from Government University. In
1957 IBM (International business Machine
Corporation) developed a general purpose
computer called IBM-701 and IBM-650. After
this, the development of electronic computer
had been grown up very rapidly. These
developments are called Generations.
Generation of Computer
Introduction :
The earlier computers were large in size and high cost. These computers
occupied large amount of floor space and consumed lot of electricity. In last 50 years,
the technology development has aimed at reducing the size and electricity
consumption and improves the performance of Computer. This development has been
in 4 different stages. Each of these stages is Called Generation.
First Generation of Computer(1949-1956)
ENLAC, EDVAC, EDSAC were First generation computer. These computers used
electronic valves (Vacuum Tubes) are main component. These computers wee large
in size, consumed more electricity and produced lot of heat. The first generation
computers had the following limitations.
1) Slow operating speed and restricted computing capacity

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2) High Power consumption and short life span.
3) Very large space requirement
4) Limited Programming Capability
Second Generation of Computer(1956-1965)
Second Generation (1955-1964): The second-generation computer used Transistors
for CPU components and ferrite cores for main memory & magnetic disks for
secondary memory. They used high-level languages such as FORTRAN (1956),
ALGOL (1960) & COBOL (1960 - 1961). Input Output (I/O) processor was included to
control I/O operations. Manufacturing cost was also very low. Thus the size of the
computer got reduced considerably. It is in the second generation that the concept of
Central Processing Unit (CPU), memory, programming language and input and output
units were developed. Some of the second generation computers are IBM 1620, IBM
1401,CDC 3600. • Transistors were used instead of Vacuum Tube. • Processing speed
is faster than First Generation Computers (Micro Second)
• Smaller in Size (51 square feet) • The input and output devices were faster.
Third Generation Computers(1965-1970)
The main components used in third generation computer was Integrated
circuits(IC). These circuits having higher speed, larger storage capacity, lower prize.
These computers are called Mini Computers. Several transistors are integrated with
other components and sealed in silicon chamber. This chamber is called Integrated
Circuits. In Third generation computers new magnetic storage, new input/output
devices like keyboard, monitor was introduced. New programming methods were
implemented. These computers were smaller in size, low cost, large memory and fast
processing
Example : IBM 360, ICL 1900, IBM 370
Fourth Generation of Computer(1970-1985)
The main Invention was Microprocessor. It was created revolution in computer
hardware industry. It is also called VLSI (very Large Scale Integrated circuit). It
performs all the calculation and logical functions in high speed. The functions of CU&
ALU are performed by Microprocessor. It has changed the face of computer.
Microprocessor is called Micro Computer. During this Period new programming
technologies like internet, E-Mail, Video Conferencing, Net phone, E-Commerce, E-
Business, were introduced. These Computers are smaller in size and fast and have
long storage capacity. E.g. : 4004, IBM-PC, Apple-DCM, Intel-8086 etc.
Fifth Generation of Computer (Since 1985)
The fifth generation starts the development of artificial intelligence (Al) introduced by
Japanese. These computers will have intelligent processors to interact with them in
natural languages such as English and German. Robotics is an example for Fifth
Generation Computer.
In sixth generation, computers are to function like biological brains. In the seventh
generation computers will be chemical rather than electronic with the use of large
number of Molecules. The six & seventh generation will form future.
Artificial Intelligence is the branch of computer science concerned with making

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computers behave like humans. The term was coined in 1956 by John McCarthy at
the Massachusetts Institute of Technology.
Artificial intelligence includes:
• Games Playing: Programming computers to play games such as chess and checkers
• Expert Systems: Programming computers to make decisions in real-life situations
(for example, some expert systems help doctors diagnose diseases based on
symptoms)
• Natural Language: Programming computers to understand natural human languages
• Neural Networks: Systems that simulate intelligence by attempting to reproduce the
types of physical connections that occur in animal brains
• Robotics: programming computers to see and hear and react to other sensory stimuli
Advantage of Computers
 A computer has a very high processing speed with high reliability (Speed)
 Along with speed all computers performs operation accurately (Accuracy)
 Large volume of information can be stored in the memory and any particular
data or program can be retrieved quickly (Storage)
 Solution to complicated problem is possible at a very high speed (versatility)
 Processing of large volume of data saves a lot of clerical work which reduces
the processing cost(steadiness)
 Computers perform operations efficiently at environments where presence of
human being not possible such as furnace, poisonous atmosphere , vaccum,
unmanned satellite etc.(Automatic)
Limitation of Computer
 High initial cost
 Input information has to be prepared in the form of statements called program
which requires a immense amount of knowledge
 Usage of computers will be economical when there is clerical data processing
or large volume of data and are repetitive in nature
Application of Computers
 Science & technology
 Education
 Medicine & Health Care
 Engineering / Architecture/ Manufacturing
 Entertainment

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 Communication
 Business Application
 Desk Top Publishing
 Banking
 Railway/ Flight Reservation System
 Telephone/ Electricity / Television / internet application
 E-Governance
Function of Computer
A Computer accepts input or data and converts them into output. This conversion is
done as per set of instruction called program.
Input or Data:
A raw facts which is required to produce result, is called an input or it is
an unprocessed facts or unevaluated facts.
Output:
The result obtained after processing is called as output
Process:
It is a method of converting input output as per the program.
Working Function Of Computer:
A digital computer is a programmable machine designed for making calculation.
Its main components are:
1) Input device
2) Central Processing Unit (C.P.U)
a) Control Unit (C.U)
b) Arithmetic & Logic Unit (ALU)
c) Memory Unit (M U)
3) Output device
1) Input Device:
It is a device through which we can send any kind of information or instruction to
computer.
E.g.:- Keyboard, Mouse, Scanner, Jay stick, Micro phone, Electronic light pen, Web

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camera, etc.
A computer receives data & instruction through input device. Then convert them into
proper Binary code.
2) Keyboard:
It is a primary input device of a computer. It has typewriter like structure. There is an
arrangement of electro mechanical keys which are used for man to machine
communication. There are more than 104 keys in a keyboard. When these keys are
pressed, the signal is passed to computer and proper action will be taken.
3) Central processing Unit :
It is a Brain & Heart of a computer system. It is a central nerve system of a computer.
It is a responsible for processing the input & converts them into output. It takes
instruction, from input device & performs, specified task as per the program & produce
the result and send into output device. It consists three main components.
a) Control unit
b) Arithmetic & logic Unit
c) Memory Unit
a) Control Unit:
Control unit keeps track (watching) of every processing, it controls entire operation of
a computer system. It controls all other devices which are connected to the CPU. It
watches the data is being received from input device, it keeps watch over working
calculation in ALU, and it controls producing of output. When the result is ready it

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sends it to memory & output device.
b) Arithmetic & Logic Unit :
As the name tells, this unit conducts all arithmetic & logic operations as per the
instructions given by CU.
ALU Performs two functions:
1) It carries out arithmetic operations like addition, subtractions, multiplications &
divisions.
2) It performs certain logical actions based ON AND & OR. Such logical operations of
ALU Enables the computer to have decision making the quality.
c) Memory Unit :
The function of memory unit is to store program, data & result. When input is received
it is stored in memory unit until CU take sit for process. During processing the CU as
well has ALU may send data to memory unit & call it back. When the output is ready
it stored in memory unit until it is sent to the output device. There are two types of
Memory.
a) Primary Memory
b) Secondary Memory
a) Primary Memory :
These memories are faster, smaller & consumes less power like a human memory it
is able to store information can be retrieved at lightning speed when the power source
is removed, its memory loses all its contents.
E.g.:- RAM Random Access Memory
ROM Read Only Memory
b) Secondary Memory :
These memories are slower, larger, consumes mare power. But it has high storage
capacity & less expensive and store information permanently i.e. when power source
is removed this memory will not loses its contents.
E.g.:- Hard Disk, Floppy Dis
k, Pen Drive, Optical disks, Zip Drive etc.
3) Output Device :-
It is a device through which we can get the result or output from the computer. E.g.:-
Monitor (screen), VDU(Visual Display Unit), CRT(Cathode Ray Tube), LCD( Liquid
Crystal Display), LED(Light Emitting Diode) TFT ( Thin Film Transistor) ,Printer,
Speakers etc.
Main Supply, Earth, Voltage and checking earth
Electric charge: Electric charge is the physical property of matter that causes it to
experience a force when placed in an electromagnetic field. Electric charge can be
positive or negative (commonly carried by protons and electrons respectively). An object with
an absence of net charge is referred to as neutral.
Voltage: Every electric charges is capable of doing work by moving another charge either by
attraction or by repulsion. This ability of a charge to do work represents its potential. The unit
of electric potential is volt.
Methods of voltage generation: Voltage can be generated by several ways. Some
methods of generating voltage are

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Voltage from friction
Voltage from moving magnets or coils
Voltage from pressure or tension in crystals
Voltage from heat
Voltage from light
Voltage from Chemical reaction
Measuring Voltage: Voltage exists between any two points with different levels of
charge. Voltage between any two points can be measured using an instrument is
called Voltmeter. Meters used to measure current is called Ammeter. There are
meters which can be used to measure voltage and current and few other electrical
parameter like resistance such meter are called Multimeter.
Types of Voltage
1. Direct Voltage
2. Alternating Voltage
3. Mixed Voltage
Direct Voltage: It is constant magnitude. It remain at the same amplitude from the
moment it is switching ON till the moment it is switched OFF
Alternating Voltage: The voltage which changes polarity at regular interval of time is
known as the alternating voltage.
Mixed Voltage: It is a combination of direct voltage and alternating voltage.
Electric Current: Electric current is produced when electric charges move in definite direction.
This movement is not only of negative charges but also o positive charges. The strength of
electric current is the quantity of charge which flows across a given cross section of conductor
every second. The unit of current strength is ampere
Measuring Current: Electric current is the flow of charge in a conductor. So to measure current,
it must pass through the measuring device. The current measuring instrument is called the
ammeter.
Types of current: Voltage causes electrical current to flow. If the cause of current flow is a
direct voltage source, then the current caused by its called direct current (d.c). On the
otherhand, then the current caused is referred as the alternating current. If a mixed voltage
AC and DC) is applied to an electrical circuit, a mixed current (AC and DC) will flow through
the circuit.
Types of power supply: Irrespective of how the electricity is generated, electricity can be
classified into two types.
• Alternating current, generally known as AC Supply
• Direct current, generally known as DC supply
AC supply: The term alternating current supply is given to a supply source that makes current
to flow through a circuit which reverses or alternates its direction periodically
Advantages of AC supply
• Reduced transmission loss over long distances.
• Voltage levels can be changed using simple devices called transformers.
• Reduced severity of electrical shock.
• Generating equipment are simple and cheaper
• Can be easily converted to DC supply.

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DC supply: The term direct current supply is given to a supply source that
makes current to flow through a circuit in one direction only. Example of DC supply is
batteries. Some types of generators are also designed to give d.c. supply. Such
generators are called DC generators.
Low tension (LT) voltage: The domestic voltage of 240 volts AC (generated and
supplied by hydro or Thermal or Nuclear generating stations) is called the low tension
(LT) voltage. LT lines enters residential buildings from electricity poles called as
service connection.
This 240 volts is used to light up the lamps, run fans etc in homes. To connect
electrical appliances at home, 240V AC is available in either two-pin or three - pin
sockets. This LT voltage of 240 volts, 50Hz is also used to supply electrical and
electronic gadgets such as Iron box, washing machine, personal computer etc.
Phase, Neutral and Earth points of LT supply: The domestic AC mains supply
of 240V, 50Hz, is available at consumers residence either in a 2-pin outlet (Phase
Neutral) or in a 3-pin outlet (phase -Neutral and Ground). These are commercially
referred to as 2/3 pin sockets. These sockets look similar to the ones shown in Fig.
Phase: The line or phase point in a socket, can be termed as the point from where the
electricity starts flowing into a closed circuit.
Neutral: The neutral point in the socket, can be termed as the point which receives
electricity from the closed circuit.
Earth / Ground: The ground (some call it Earth) point in an electrical socket provides
the easiest path for the leakage current and other minor electrical defect currents of
appliances.
Two pin mains sockets are used to supply main to such equipment or apparatus
or gadgets generally having its cabinets/chassis made of plastic such as radio, tape
recorders etc., Hence such gadgets does not need earth pin/point on the socket. Iron

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box, washing machines, drill guns, Desk top computer invariably need sockets with
provision of earth pin, because of the possibility of shock while using these
equipments. Hence such equipments/gadgets make use of AC mains socket with
earth.
Connection of 3-pin AC mains socket: Fig shows how the main supply is connected
to the socket.
Note that in a AC outlet be it a 2-pin or a 3-pin phase is always connected to
the socket through a switch. This prevents the users from getting electrical shock when
the switch is put in off position.
The standard voltage appearing across the 3-pin terminals is shown in Fig
The voltages across the pins of the socket can be measured using an AC
voltmeter or a multimeter in AC volts range. As a quick test to find out whether or not
a socket is delivering the AC supply as required, a simple instrument called line tester

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which looks similar to a small screw driver can be used. This instrument will have a
small bulb in it which glows if it is touched to the phase pin in the socket.
Most Desk top computers need AC mains supply for its operation. Although the
mains supply available in the 3pin socket shown above can be used, mostly this AC
supply is cleaned fro spikes before connecting to computers. The device used for
cleaning the spikes in the mains AC supply are called Spike Arrestors or Spike busters.
Computers are used with spike busters because, AC spikes are likely to damage the
costly computers. In addition to spike busters, most computers use other power safety
devices called the voltage stabilizers and uninterrupted power supplies
Power supply in computers:
The power supply connects to nearly every device in the PC to provide power.
It is located at the rear of the case. The system unit draws power from the AC mains
through a power protection device.This power is not directly supplied to the internal
components. Instead, one of the components, called the internal power supply,
converts the AC input into DC output of 5 and 12 volts. Normally, the internal power
supply is referred to as Switched Mode Power Supply (SMPS).The SMPS provides
cable connectors to supply the required voltage to the other internal components like
the floppy drives, the hard disk drive, the motherboard and external device such as
the keyboard. The ON/OFF switch of the system unit is actually a part of the SMPS.
A switched-mode power supply (SMPS) is an electronic circuit that converts
power using switching devices that are turned on and off at high frequencies, and
storage components such as inductors or capacitors to supply power when the
switching device is in its non-conduction state.
Switching power supplies have high efficiency and are widely used in a variety
of electronic equipment, including computers and other sensitive equipment requiring
stable and efficient power supply.
A switched-mode power supply is also known as a switch-mode power supply
or switching-mode power supply.

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Introduction to CPU architecture and motherboard
Computer science is divided into three categories
1. Hardware
2. Software
3. Firmware
Computer Hardware
The physical units of a computer are called as the hardware of a computer. Computer
hardware is a collective term used to describe any of the physical components of an
analog or digital computer. The term hardware distinguishes the tangible aspects of a
computing device from software, which consists of written, machine-readable
instructions or programs that tell physical components what to do and when to execute
the instructions.
Hardware and software are complementary. A computing device can function
efficiently and produce useful output only when both hardware and software work
together appropriately.
Computer hardware can be categorized as being either internal or external
components. Generally, internal hardware components are those necessary for the
proper functioning of the computer, while external hardware components are attached
to the computer to add or enhance functionality.
What are internal computer hardware components?
Internal components collectively process or store the instructions delivered by the
program or operating system (OS). These include the following:
Motherboard. This is a printed circuit board that holds the central processing unit
(CPU) and other essential internal hardware and functions as the central hub that all
other hardware components run through.
 CPU. The CPU is the brain of the computer that processes and executes digital
instructions from various programs; its clock speed determines the computer's
performance and efficiency in processing data.

19
 RAM. RAM -- or dynamic RAM -- is temporary memory storage that makes
information immediately accessible to programs; RAM is volatile memory, so
stored data is cleared when the computer powers off.
 Hard drive. Hard disk drives are physical storage devices that store both
permanent and temporary data in different formats, including programs, OSes,
device files, photos, etc.
 Solid-state drive (SSD). SSDs are solid-state storage devices based on NAND
flash memory technology; SSDs are non-volatile, so they can safely store data
even when the computer is powered down.
 Optical drive. Optical drives typically reside in an on-device drive bay; they enable
the computer to read and interact with nonmagnetic external media, such as
compact disc read-only memory or digital video discs.
 Heat sink. This is a passive piece of hardware that draws heat away from
components to regulate/reduce their temperature to help ensure they continue to
function properly. Typically, a heat sink is installed directly atop the CPU, which
produces the most heat among internal components.
 Graphics processing unit. This chip-based device processes graphical data and
often functions as an extension to the main CPU.
 Network interface card (NIC). A NIC is a circuit board or chip that enables the
computer to connect to a network; also known as a network adapter or local area
network adapter, it typically supports connection to an Ethernet network.
Other computing components, such as USB ports, power supplies, transistors and
chips, are also types of internal hardware.
What are external hardware components?
External hardware components, also called peripheral components, are those
items that are often externally connected to the computer to control either input or
output functions. These hardware devices are designed to either provide instructions
to the software (input) or render results from its execution (output).
Common input hardware components include the following:
 Mouse. A mouse is a hand-held pointing device that moves a cursor around a
computer screen and enables interaction with objects on the screen. It may be
wired or wireless.
 Keyboard. A keyboard is an input device featuring a standard QWERTY keyset
that enables users to input text, numbers or special characters.

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 Microphone. A microphone is a device that translates sound waves into electrical
signals and supports computer-based audio communications.
 Camera. A camera captures visual images and streams them to the computer or
through a computer to a network device.
 Touchpad. A touchpad is an input device, external or built into a laptop, used to
control the pointer on a display screen. It is typically an alternative to an external
mouse.
 USB flash drive. A USB flash drive is an external, removable storage device that
uses flash memory and interfaces with a computer through a USB port.
 Memory card. A memory card is a type of portable external storage media, such
as a CompactFlash card, used to store media or data files.
Other input hardware components include joysticks, styluses and scanners.
Examples of output hardware components include the following:
 Monitor. A monitor is an output device similar to a TV screen that displays
information, documents or images generated by the computing device.
 Printer. Printers render electronic data from a computer into printed material.
 Speaker. A speaker is an external audio output device that connects to a computer
to generate a sound output.
 Headphones, earphones, earbuds. Similar to speakers, these devices provide
audio output that's audible only to a single listener.


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INPUT DEVICE
An input device is any hardware device that sends data to a computer,
allowing you to interact with and control it. It is a device through which we
can send any kind of information to computer.

22
Keyboard : A keyboard is one of the primary input devices used with a
computer. Similar to an electric typewriter, a keyboard is composed of
buttons used to create letters, numbers, and symbols, and perform
additional functions.
Numeric Keypad : The numeric keypad allows an individual to quickly input numbers
into a computer. For example, the keypad is often used for anyone who deals with
numbers frequently or has to perform calculations with a software calculator.
Mouse or Pointing Device : A computer mouse is a handheld hardware input
device that controls a cursor in a GUI (graphical user interface) for pointing, moving
and selecting text, icons, files, and folders on your computer. In addition to these
functions, a mouse can also be used to drag-and-drop objects and give you access to
the right-click menu.
Joy Stick : A joystick is an input device that control a character or machine in a
computer program, such as a plane in a flight simulator. They look similar to the control
device you would find on an arcade game, but nearly always include extra buttons for
additional functionality.
Touch Screen : A touch screen is a display device that allows users to interact with
a computer using their finger or stylus. They're a useful alternative to a mouse or
keyboard for navigating a GUI (graphical user interface). Touch screens are used on
various devices, such as computer and laptop displays, smartphones, tablets, cash

23
registers, and information kiosks. Some touch screens use a grid of infrared beams to
sense the presence of a finger instead of utilizing touch-sensitive input.
Scanner : When referring to hardware, a scanner, image scanner, or optical
scanner is a hardware input device that optically "reads" an image and converts it to a
digital signal. For example, a scanner may be used to convert a printed picture,
drawing, or document (hard copy) to a digital file that can be edited on a computer.
Two Types of Scanner: 1) Hand Held Scanner 2) Flatbed Scanner
Hand Held Scanner : Handheld scanners are small helpful electronic devices that
are widely used for digitizing printed documents. Although considered lower
quality scanners, they are still very popular because they are small and less
expensive than their flatbed counterparts, and they are able to scan items that
could not fit in a flatbed scanner due to size or location. Their function includes
moving them over the material being captured with the aid of a tray to keep it in
a straight line. Example Bar Code Reader
Flat Bed Scanner : A flatbed scanner is an optical scanner which makes use of a flat
surface for scanning documents. The scanner is capable of capturing all elements on
the document and does not require movement of the document. Flatbed scanners are
effective scanners for delicate materials such as vintage photographs, papers and
other documents which are fragile.
Graphic Tablet : It is also called a drawing tablet or a pen tablet, a graphics
tablet is a natural input device that converts information from a handheld stylus. The
user uses the stylus like a pen, pencil, or paintbrush, pressing its tip on the tablet
surface. The device can also be used in replacement of a computer mouse.
Microphone : . originally invented by Emile Berliner in 1877. A microphone is a device
that translates sound vibrations in the air into electronic signals... It is used to convert
sound waves into electric waves or input the audio into computers. The microphone
plugs into the computer sound card microphone port on the back of desktop
computers. Some computer cases may also have a microphone port on the front.
Digital Camera : A digital camera is a hardware device that takes photographs and
stores the image as data on a memory card. Unlike an analog camera, which exposes
film chemicals to light, a digital camera uses digital optical components to register the
intensity and color of light, and converts it into pixel data. Many digital cameras are
capable of recording video in addition to taking photos.
Web Cam: A webcam is a camera that connects to a computer. It captures either
still pictures or motion video, and with the aid of software, can transmit its video on
the Internet in real-time. Unlike a digital camera and digital camcorder, a webcam does
not have any built-in storage. Instead, it is always connected to a computer and uses
the computer hard drive as its storage.

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Light Pen: A light pen is a light-sensitive pointing input device commonly
used to select or otherwise modify text or data on a screen. Used with
a CRT monitor, these devices were an early form of manipulating and
highlighting data on the screen. Light Pen (similar to the pen) is a pointing device
which is used to select a displayed menu item or draw pictures on the monitor screen.
It consists of a photocell and an optical system placed in a small tube. When its tip is
moved over the monitor screen, and pen button is pressed, its photocell sensing
element detects the screen location and sends the corresponding signals to the CPU.
Output device : A device through which we can get result from the computer is called
Output device. There are two types of output devices. 1) Hardcopy Output Device 2)
Softcopy Output device.
Hardcopy Output Device : These devices are devices that provide output on printed
paper or Other permanent media that is human readable. Example 1) Printer 2) Plotter
Printer : A printer is an external hardware output device that takes the electronic data
stored on a computer or other device and generates a hard copy. A printer is a
hardware output device that is used to generate hard copy and print any document. A
document can be of any type such as a text file, image, or the combination of both. It
accepts input command by users on a computer or on other devices to print the
documents. There are two types of printer 1) Impact Printer 2) Non-Impact Printer

25
Impact Printer: An impact printer is a class of printers that functions by making
physical contact with an ink ribbon before striking the page. Daisy wheel, dot
matrix and line printers are all examples of impact printers. It creates Sound during
printing. Example 1) Dot Matrix Printer 2) Daisy Wheel Printer 3) Line Printer
Dot Matrix Printer : The term dot matrix refers to the use of dots to form an image.
In a dot matrix image, the quality is determined by the number of dots per inch. Dot
matrix printers use print heads to shoot ink or strike an ink ribbon to place hundreds
to thousands of little dots to form text and images. Today, dot matrix printers are
utilized far less than they used to be due to their low quality images and slow print
speed compared to inkjet printers and laser printers. However, they still see a lot of
use in certain sectors such as auto part stores and package delivery companies.
Daisy Wheel Printer : A daisy wheel printer is an early type of impact printer invented
in 1969 by David S. Lee at Diablo Data Systems. The printer uses a metal or plastic
disk containing each of the letters, numbers, and other characters it supports. When
printing, the printer rotates the disk to each character and, using a hammer, strikes
each character into an ink ribbon to create characters on paper. Daisy wheel printers
were popular in the 1970s and 1980s, but are no longer used today. They have a low
quality of print, are very slow and loud, and were replaced by laser printers as they
came down in cost.
Line Printer : Alternatively referred to as a band printer, chain printer, drum printer,
and barrel printer, a line printer is a high-speed printer capable of printing an entire
line of text at once. These types of printers are too fast to be measured in words or
characters per minute, and instead are measured in lines per minute. For example, a
line printer may be capable of printing over 3,000 lines of type per minute.
Non Impact Printer : This printer prints without making contact with the paper. They
are generally quieter and more efficient than their impact
counterparts. Laser and inkjet printers are both good examples of a non-impact printer.

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Inkjet Printer : The most popular printer for home computer users that prints by
spraying streams of quick-drying ink on paper. The ink is stored in disposable
ink cartridges, and often a separate cartridge is used for each of the major colors.
These colors are usually CMYK (cyan, magenta, yellow, and black). Although inkjet
printers themselves are often relatively inexpensive, the ink cartridges used in the
printers can increase the overall cost of the printer.
Thermal Printer : A thermal impact printer or electrothermal printer is a printer
that uses heated pins to "burn" images onto heat-sensitive paper. These printers are
commonly used in calculators and fax machines; and although they are inexpensive
and print relatively fast, they produce low resolution print jobs. A thermal
printer, thermal transfer printer, or thermal wax-transfer printer uses thermal wax
ribbon to melt colored wax on paper for a photo print. It was invented by Jack Kilby.
Laser Printer : The laser printer was first developed at Xerox PARC by Gary
Starkweather and released in 1971 that utilizes laser technology to print images on
the paper. Laser printers are often used for corporate, school, and other environments
that require print jobs to be completed quickly and in large quantities.
How a laser printer works and its printing steps
Cleaning :This process removes the prior image information and toner from the drum.
Conditioning :The corona wire applies a uniform, positive charge to the photoreceptor
drum.
Writing :The image to be printed is drawn onto the drum using a laser to "carve-out"
positive charges and leave behind negative ones. As an aside, the laser in the printer
uses light sources, like LED (light-emitting diode) or LCS (liquid crystal shutter).
Developing :The toner in the ink roller is ionized with a positive charge, attracting it to
negatively charged areas on the drum.
Transfer :The drum's toner is transferred to the paper by either a positively ionized
field (created by a transfer corona wire) or a transfer roller in newer printers. The toner
is not yet permanently set on the paper and requires the last stage.
Fusing :Heat and pressure are applied to the paper and toner by two fuser units. The
toner melts and is pressed into the paper like doing an iron-on transfer to a T-shirt.
Difference between Impact Printer & Non Impact Printer
Impact Printer Non Impact Printer
Produces characters and graphics on a
piece of paper by striking it is called
impact printer.
A type of printer that produces
characters and graphics on a piece of
paper without striking.

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Impact Printer Non Impact Printer
It prints by hammering a set of metal
pin or character set.
Printing is done by depositing ink in
any form.
Electromechanical devices are used No electromechanical device is used.
Faster speeds around 250 words per
second.
Slower speeds around 1 page per 30
seconds.
Have banging noise of needle on paper Works silently
Dot-matrix printer, Daisy wheel
printers, line printer are examples .
inkjet printers, photo printers, laser
printers are examples .
It generally cost less. It cost more than impact printers.
They are not suited for printing
photograph or any high quality media.
They are best suited for printing
photograph or any high quality media.
Plotter : A plotter is a computer hardware device much like a printer that is used for
printing vector graphics. Instead of toner, plotters use a pen, pencil, marker, or another
writing tool to draw multiple, continuous lines on paper rather than multiple dots, like
a traditional printer. Plotters produce a hard copy of schematics and other similar
applications. Though once widely used for computer-aided design, these devices were
more or less phased out by wide-format printers.
Softcopy output device : Softcopy output is an output that is not produced on paper
or some materials which cannot be touched or carried for being shown to others. They
are temporary in nature and vanish after use. Example 1) CRT Monitor, LED Monitor,
LCD Monitor , TFT Monitor 2) Speakers, Head Phones, ear buds
CRT Monitor : Short for cathode ray tube, a CRT is the electron beams in a monitor
moving across your screen either interlaced or non-interlaced, hitting phosphor dots
inside the glass tube.
LCD Monitor : A liquid crystal display (LCD) monitor is a computer monitor or
display that uses LCD technology to show clear images, and is found mostly in laptop
computers and flat panel monitors. This technology has replaced the traditional
cathode ray tube (CRT) monitors, which were the previous standard and once were
considered to have better picture quality than early LCD variants. With the introduction
of better LCD technology and its continuous improvement, LCD is now the clear leader
over CRT, in terms of color and picture quality, not to mention capabilities for large
resolutions.

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LED Monitor : Short for light-emitting diode monitor, an LED monitor or LED display
is a flat screen, flat-panel computer monitor or television. It has a very short depth and
is light in terms of weight. The actual difference between this and a typical LCD monitor
is the backlighting. The first LCD monitors used CCFL instead of LEDs to illuminate
the screen.
TFT monitor : A TFT monitor uses thin-film transistor technology in an LCD display.
LCD monitors, also called flat panel displays, are replacing the old-style cathode ray
tubes (CRTs) in both televisions and computer displays. Nearly all LCD monitors today
use TFT technology.
Speaker : A computer speaker is an output hardware device that connects to a
computer to generate sound. The signal used to produce the sound that comes from
a computer speaker is created by the computer's sound card. Speakers are made up
of a cone, an iron coil, a magnet, and housing (case). When the speaker receives
electrical input from a device, it sends the current through the causing it to move back
and forth. This motion then vibrates the outer cone, generating sound waves picked
up by our ears.
Head Phone : Sometimes referred to as earphones, headphones are a
hardware output device that plug into a computer line out or speakers port.
Headphones allow you to listen to audio or watch a movie without disturbing people
around you.
Ear Buds : Ear buds are basically a pair of tiny speakers that you wear inside your
ears. At low volumes, they're useful little devices. But playing loud music so close to
your eardrums can cause permanent hearing loss.
Internal Hardware Devices
CPU(Microprocessor),Hard Disk drive, Motherboard, RAM, Sound card, Video
card, Blu-Ray, CD-ROM, and DVD , SMPS
CPU/Microprocessor: Central Processing Unit (CPU) is the heart and brain of the
Computer. It is the hardware that carries out the instructions of a computer program
by performing the basic arithmetical, logical, and input/output operations of the system.
Alternately referred to as a processor, central processor, or microprocessor,
the CPU is the central processing unit of the computer. A computer's CPU handles
all instructions it receives from hardware and software running on the computer. For
example, the CPU processed the instructions to use a web browser to open and
display this web page on your computer.
The CPU is often referred to as the brain of the computer. However, it is more
appropriate to refer to software as the brain and the CPU as a very efficient calculator.
A CPU is really good with numbers, but if it wasn't for the software it wouldn't know
how to do anything else.

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The processor is placed and secured into a compatible CPU socket found on
the motherboard. Processors produce heat, so they are covered with a heat sink to
keep them cool and running smoothly. To help transfer the heat between the CPU and
the heat sink. The CPU's main function is to take input from a peripheral (keyboard,
mouse, printer, etc) or computer program, and interpret what it needs. The CPU then
either outputs information to your monitor or performs the peripheral's requested task.
Motherboard : The motherboard is a printed circuit board and foundation of a
computer that is the biggest board in a computer chassis. It allocates power and allows
communication to and between the CPU, RAM, and all other
computer hardware components. A motherboard provides connectivity between the
hardware components of a computer, like the processor (CPU), memory (RAM), hard
drive, and video card. A computer motherboard is located inside the computer
case and is where most of the parts and computer peripherals connect. With tower
computers, the motherboard is on the left or right side of the tower and is the
biggest circuit board.
Memory Devices: Computer memory is any physical device capable of storing
information temporarily, like RAM (random access memory), or permanently,
like ROM (read-only memory). Memory devices utilize integrated circuits and are used
by operating systems, software, and hardware. There are two types of memories.
1. Primary Memory/Semiconductor Memories/ main memory/ system memory
2. Secondary Memory / auxiliary memory / Magnetic Memory/ Permanent Memory
Primary Memory : A primary storage device is a medium that holds memory for short
periods of time while a computer is running. Although it has a much lower access
time and faster performance, it is also about two orders of magnitude more costly
than secondary storage. Example RAM & ROM
RAM : Alternatively referred to as main memory, primary memory, or system
memory, RAM (random-access memory) is a hardware device that allows
information to be stored and retrieved on a computer. RAM is usually associated
with DRAM, which is a type of memory module. Because data is accessed randomly
instead of sequentially like it is on a CD or hard drive, access times are much faster.
However, unlike ROM, RAM is a volatile memory and requires power to keep the data
accessible. If the computer is turned off, all data contained in RAM is lost.
The different types of RAM are DRAM(Dynamic Random Access Memory &
SRAM(Static Random Access Memory), SDRAM(Synchronized Dynamic Random
Acees Memory , DDR RAM(Double Data Rate Random Access Memory. DDR2 RAM,
DDR3 RAM, DDR4 RAM(Latest)

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RAM slots: Random-Access Memory (RAM) stores programs and data currently being
used by the CPU. RAM is measured in units called bytes. RAM has been packaged in
many different ways 1) SIMM-Single inline memory module -32 or 72 Pin 2) DIMM-
Dual Inline Memory module -168 pin. In most of the PC's uses of the DIMM module
ROM: Short for read-only memory, ROM is a storage medium that is used with
computers and other electronic devices. As the name indicates, data stored in ROM
may only be read. It is either modified with extreme difficulty or not at all. ROM is
mostly used for firmware updates. The Different types of ROM are PROM
(Programmable Read Only Memory), EPROM (Erasable Programmable Read Only
Memory, EEPROM (Electrically Erasable Programmable Read Only Memory)
Secondary Memory Devices: Alternatively referred to as external
memory, secondary memory, and auxiliary storage, a secondary storage
device is a non-volatile device that holds data until it is deleted or overwritten.
Secondary storage is about two orders of magnitude cheaper than primary storage.
Consequently, a hard drive or an additional, slower SSD may use as secondary
storage to a primary, faster. Example: Hard drive ,Solid-state drive, USB thumb drive,
SD card, CD,DVD, Floppy diskette, Tape drive
Hard Disk Drive : A hard disk drive (sometimes abbreviated as a hard drive, HD,
or HDD) is a non-volatile data storage device. It is usually installed internally in a
computer, attached directly to the disk controller of the computer's motherboard. It
contains one or more platters, housed inside of an air-sealed casing. Data is written
to the platters using a magnetic head, which moves rapidly over them as they spin.
Internal hard disks reside in a drive bay, connected to the motherboard using
an ATA, SCSI, or SATA cable (Serial Advanced Technology Attachment They are
powered by a connection to the computer's PSU (power supply unit).
A computer requires an operating system to allow users to interact with and use
it. The operating system interprets keyboard and mouse movements and allows for
the use of software, like an Internet browser, word processor, and video games. To
install a computer operating system, a hard drive (or another storage device) is
required. The storage device provides the storage medium where the operating
system is installed and stored.
A hard drive is also required for the installation of any programs or other files
you want to keep on your computer. When downloading files to your computer, they
are permanently stored on your hard drive or another storage medium until they are
moved or uninstalled.
Modern computers often use an SSD (solid-state drive) as the primary storage
device, instead of an HDD. HDDs are slower than SSDs when reading and writing
data, but offer greater storage capacity for the price.
Although an HDD may still be used as a computer's primary storage, it's
common for it to be installed as a secondary disk drive. For example, the primary SSD

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may contain the operating system and installed software, and a secondary HDD may
be used to store documents, downloads, and audio or video files.
SSD Hard Disk : Short for solid-state drive, an SSD is a storage medium that
uses non-volatile memory to hold and access data. Unlike a hard drive, an SSD has
no moving parts, which gives it advantages, such as faster access time, noiseless
operation, higher reliability, and lower power consumption.
USB Drive : A USB drive is any drive connected to a USB port on a computer. The
most common type of USB drive is a flash drive. A USB drive can also refer to a disc
drive, external hard drive, RAID, or any other media connected to a computer using
the USB port.
USB (Universal serial bus) Ports : Devices like digital cameras, scanners and
printers often connect to the motherboard via the USB ports. A USB connector's
distinctive rectangular shape makes it easily recognizable. USB has a number of
features that makes it particularly popular on PCs. First, USB devices are hot
swappable. You can insert or remove them without restarting your system
SD Card : Short for Secure Digital card, the SD card is one of the more common
types of memory cards used with electronics. The SD technology is used by over 400
brands of electronic equipment and over 8000 different models, including digital
cameras and cell phones. It is considered the industry standard due to the wide use.
CD/DVD/Blue Ray : Abbreviated as CD, a compact disc is a flat, round, optical
storage medium. Compact disc (CD), a molded plastic disc containing digital data that
is scanned by a laser beam for the reproduction of recorded sound and other
information. Storing Capacity of CD is 650 MB to 700 MB
DVD : Short for digital versatile disc or digital video disc, a DVD or DVD-ROM is
a disc capable of storing a significant amount more data than a standard compact disc.
DVDs are widely used for storing and viewing movies and other data. Storing capacity
of DVD is 4.2GB. To read and play DVDs on a computer, you must have a DVD-ROM
drive and DVD player software.
Blue Ray Disc: A Blu-ray disk (BD) is a high-capacity optical disk medium
developed for recording, rewriting and playing back high definition video. It can
store large amounts of data and was designed to supersede the DVD. The storage
capacity of BD is 25GB to 50 GB
Sound Card : Alternatively referred to as an audio output device, sound board,
or audio card. A sound card is an expansion card or IC for producing sound on a
computer that can be heard through speakers or headphones. Although the computer
doesn't need a sound card, it's included on every machine as either in an expansion
slot or built into the motherboard (onboard).

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Video Card : Alternatively known as a display adapter, graphics card, video
adapter, video board, or video controller, a video card is an expansion card that
connects to a computer motherboard. It is used to create a picture on a display; without
a video card, you would not be able to see this page. More plainly, it's a piece
of hardware inside your computer that processes images and video, some of the tasks
normally handled by the CPU. Video cards are used by gamers in place of integrated
graphics due to their extra processing power and video ram.
CPU Ports and Connectors :A port is a connector at the back of a Computer cabinet
where you plug in an external
device such as a printer, keyboard,
scanner, modem etc. This allows
instructions and data to flow
between the computer and the
device. The computer ports are also
commonly referred to as the
Input/output ports (I/O ports).
These ports can be either serial or
parallel. Most connectors are
separated, permitting the cable to
be plugged in only in the correct
direction. The keyboard and mouse
use "PS2" (Personal System 2)
connectors. The PS2 connectors
are color-coded. The purple
connector is for the keyboard. The green connector is for the mouse.
USB (Universal serial bus) Ports : Devices like digital cameras, scanners and
printers often connect to the motherboard via the USB ports. A USB connector's
distinctive rectangular shape makes it easily recognizable. USB has a number of
features that makes it particularly popular on PCs. First, USB devices are hot
swappable. You can insert or remove them without restarting your system
LAN(Local Area Network) Port: The LAN port is used to connect the PC to a local
network or to high speed Internet services.
VGA (Video Graphics Array) Ports: The VGA port provides access to integrated
video.
Audio ports: It provides access to integrated audio. The audio jacks are the most
confusing connectors on the back panel. Although the jacks are sometimes color
coded, the devices that plug into them rarely.
Fan
The SMPS has a small fan, called the exhaust fan, attached to SMPS. This fan rotates
as long as the computer is switched on. Its function is to cool the SMPS unit.

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Front Panel of CPU: The front panel of the
computer consists the following parts and
CPU cabinet is vary based on manufacturer.
1. CD/DVD Drive 2) CD/DVD Tray open
Button 3) CD/DVD LED light 4) USB ports 5)
Head Phone/ MIC ports 6) Power Switch 7)
Reset Button
Drive Bays: The 5.25" and 3.5" drive bays
house the many kinds of storage devices a
computer might contain.
Expansion Slots: An expansion slot is a slot located inside a computer mother board
that allow additional peripherals to be connected to it.
Memory Slot
Memory Slot is used to insert a Random Memory(RAM) shown in following
picture
Storage Drivers
Storage drivers such as hard drives, optical drives and floppy drives all connect
to the motherboard via cables and is mounted inside the computer. IDE & SATA
Cables: Fig 6 shows two hard disk drives that connect in different ways to the
motherboard. One uses the older IDE cable connection while the other uses
SATA(Serial Advanced Technology Attachment) cable which provides for faster hard
drive access.
Motherboard :
The motherboard is a printed circuit that is the foundation of a computer and allows
the CPU, RAM, and all other computer hardware components to function with each
other. The motherboard is the primary component of the entire system. A mother board
is a large board containing a number of tiny electronic circuits and other components
are visible. All peripheral devices are connected to the motherboard. The components
of the motherboard are:
• Keyboard / mouse port • Parallel and Serial port • Processor Socket
• AGP Slot • PCI Slots • ISA Slot • CMOS Battery • Data Card Connector
• Memory Slots • Floppy Port • Fan Header • Main Power Connector
CMOS Battery: CMOS (Complementary Metal-Oxide-Semiconductor) is the term
usually used to describe the small amount of memory on a computer motherboard that
stores the BIOS settings. Most CMOS batteries will last the lifetime of a motherboard
(up to 10 years in most cases) but will sometimes need to be replaced. Incorrect or

34
slow system date and time and loss of BIOS settings are major signs of a dead or
dying CMOS battery.
ISA Slot: : (Industry Standard Architecture) It is the standard architecture of the
Expansion bus. Motherboard may contain some slots to connect ISA compatible
cards.
PCI Slot : Intel introduced the Peripheral Component Interconnect bus protocol. The
PCI bus is used to connect I/O devices to the main logic of the computer. PCI bus has
replaced the ISA bus. PC motherboards have one PCI slot but generally more than
one.
AGP Slot: The Accelerates Graphics Port (AGP) is a high-speed point-to-point
channel for attaching a video card to a computer's motherboard.
Floppy Port : The floppy drive connects to the computer via a 34-pin ribbon cable,
which in turn connects to the motherboard. A floppy controller is one that is used to
control the floppy drive.
RAM Slots: Random-Access Memory (RAM) stores programs and data currently
being used by the CPU. RAM is measured in units called bytes. RAM has been
packaged in many different ways
• SIMM-Single inline memory module -32 or 72 Pin
• DIMM- Dual Inline Memory module -168 pin.
In most of the PC uses DIMM Module
ROM BIOS Chip
This means Read Only Memory Basic Input Output System. The built in
software that determines what a computer can do without accessing programs from a
disk. On pc the BIOS contains all the code required to control the keyboard, display
screen, disk drives, serial communications and a number of miscellaneous functions
The BIOS is typically placed in a ROM chip that comes with the computer (it is
often called a ROM BIOS). This ensures that the BIOS will always be available and
will not be damaged by disk failures.
It also makes it possible for a computer to boot itself. Because RAM is faster
than ROM, though, many computer manufacturers design systems so that the BIOS
is copied from ROM to RAM each time the computer is booted. This is known as
shadowing.
Many modern PCs have flash BIOS, which means that the BIOS have been
recorded on a flash memory chip, which can be updated if necessary. The PC BIOS
is fairly standardized, so all PCs are similar at this level (although there are different
BIOS versions). Additional DOS functions are usually added through software
modules. This means you can upgrade to newer version of DOS without changing the

35
BIOS. PC BIOS that can handle Plug-In-Play (PnP) devices are known as PnPBIOS.
These bios are always implemented with flash memory rather than ROM.
Power supply plug in: The Power supply, as its name implies, provides the
necessary electrical power to make the PC (Personal Computer) operate. The power
supply takes standard 110-V AC power and converts into +/-12-Volt, +/-5-Volt, and
3.3-Volt DC power. The power supply connector has 20-pins, and the connector can
go in only one direction.
Hard Disk and Partitions: Partitioning is a process of dividing the Hard disk
into several chunks, and uses any one of the portion or partition to install OS or use
two or more partitions to install multiple OS.
But it can always have one partition, and use up the Entire Hard disk space to
install a single OS, but this will become data management nightmare for users of large
Hard disks.
Now, because of the structure of the Master Boot Record (MBR), has only four
partitions, and these four partitions are called Primary Partitions.
Extended Partition is not a usable partition by itself, but it's like a "container"
and it is used to hold Logical Drives! That is this Extended Partition can be subdivided
into multiple logical partitions.
In order to boot into a Partition, it must be designated as bootable partition or
Active Partition. Active Partition is that partition which is flagged as bootable or which
contains OS, this is generally a Primary Partition.
Types of Partitions:
• Master
• Partition
• Extended and
• Logical Extended
Master Boot Record (MBR): MBR is a small 512 bytes partition which is at the
first physical sector of the hard disk. The location is denoted as CHS 0,0,1 meaning
0th Cylinder, 0th Head and 1st Sector.
MBR contains a small program known as bootstrap program which is
responsible for booting into any OS.MBR also contains a table known as Partition
Table.
This Partition Table is a table which lists the available Primary Partitions in the
hard disk. Partition table considers whole Extended Partition as one Primary Partition
and lists it in the table! So a Partition table can have two possible entries:•
Up to 4 Primary Partitions.
Up to 3 Primary Partitions and 1 Extended Partition.(Total not exceeding 4) .

36
Partition Boot Sector (PBR): This is the logical first sector that is sector at the start
of a Primary Partition. This is also 512 byte area, which contains some programs to
initialize or run OS files. All Primary Partitions have its own PBRs.
Extended Boot Sector (EBR): This is the logical first sector that is the sector at the
start of the Extended Partition. This EBR contains a Partition Table, which lists the
available Logical Partitions inside Extended Partition. That is it contains the Starting
addresses of each Logical Partitions.
Logical Extended Boot Sector (LEBR): This is the logical first sector residing at the
start of each Logical Partition. This is similar to PBR for Primary Partitions.
Booting: Booting is a process of loading the operating system (OS) and checking all
the system software and hardware those are installed in the computer.
Booting procedure of Windows operating system
Functions of BIOS
The first process starts, when the computer switched on Basic Input Output
System (BIOS) perform two functions, to conduct POST and read MBR
POST : - POST stands for Power On Self Test. POST checks all the hardware devices
connected to a computer like RAM, hard disk etc. and make sure that the system can
run smoothly with those hardware devices. If the POST is a failure the system halts
with a beep sound. Now BIOS checks the boot priority. We can set the boot priority as
CD drive, hard disk or floppy drive.
MBR - The next duty of BIOS is to read the MBR. MBR stands for Master Boot Record
and it's the first sector on a hard disk. MBR contains the partition table and boot loader.
Functions of Boot loader : Now BIOS has passed the control to boot loader and boot
loader is a small program which loads kernel to computers memory. Actually there are
two stages of boot loaders, stage 1 boot loader and stage 2 boot loader.

37
The stage 1 boot loader is a link to the stage 2 boot loader.
The stage 2 boot loader resides in the boot partition and
it loads the kernel to memory.
Boot files and functions: There are three boot files in a Windows operating system
and they are NTLDR, NTDETECT.COM and Boot.ini. The boot files are found in the
active partition of hard disk and its normally C drive in a Windows machine.
NTLDR - NTLDR stands for NT Loader and it's the second stage boot loader. The path
of NTLDR is C:Windowsi386NTLDR.
Boot.ini : - Boot.ini contains the configuration files of NTLDR. When the operating
system is loaded we cannot pass any arguments to kernel, so those arguments are
passed through boot.ini. You can edit boot.ini by opening through notepad. The path
of Boot.ini is C:boot.ini.
NTDETECT.COM
This file detects hardware's and passes information to NTLDR. Using the collected
information the NTLDR creates a hardware key and this key is used to detect
hardware's.
A new hardware key is generated after each reboot of the operating system
and that's why system asks to reboot after installation of a new hardware. The
hardware keys created by NTLDR can be found in Windows registry at
HKEY_LOCAL_MACHINE ' HARDWARES.
Kernel and its functions
After executing the functions of boot files, the control is passed to Kernel
NTOSKRNAL.EXE is the kernel file in windows machine and its path is
C:Windowssystem32ntoskrnal.exe
Kernel acts as a layer between software and hardware. The library file hal.dll
(C;Windowssystem32hal.dll) helps Kernel to interact with hardware's. HAL stands
for Hardware Abstraction Layer and this hal.dll file is machine specific. Now the drivers
for hardware's are loaded from the file C:Windowssystem32configsystem and the
Kernel is loaded to primary memory.
Services and log in procedure
When kernel is loaded in the primary memory, services for each process is
started and the registry entry for those services can be found at
HKEY_LOCAL_MACHINE System - Current control set -Services.
Winlogon.exe (C:Windowssystem32winlogon.exe) is the last service started during
this process.Winlogon.exe starts the log in procedures of windows machine. It first
calls the library filemsgina.dll (C:Windowssystem32msgina.dll).

38
MSGINA stands for Microsoft Graphics Identification and Authentication and it
provides he log in window.Nowmsginal.dll passes the control to LSA (Local Security
Authority), it verifies the username and password from the SAM file. SAM (Security
Accounts Manager) contains the information about all users created in a Windows
operating system.
Now the booting procedure is over and it has reached the desktop of Windows
operating system
OPERATING SYSTEM
Objectives:
 Define a system software and operating system and mention its functions
 Define application software
 List the types of operating system

Introduction to Computers and windows operating system.pdf

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