Computer system organization || Class 11

COMPUTER SYSTEM ORGANIZATION
Understanding fundamental of computer
VINOD KUMAR VERMA, PGT(CS), KV OEF KANPUR &
SACHIN BHARDWAJ, PGT(CS), KV NO.1 TEZPUR
for more updates visit: http://www.python4csip.com
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What is Computer?
 A computer is an electronic device that can perform
a variety of operations in accordance with set of
instructions called program.
 A computer can be defined as an electronic device
which accepts input from the user, process the input
and produce the desired output.
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Basic Computer Components
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Introduction
 Our present day life is so automatic that most of the tasks are accomplished
with a click of a button. In every sphere of life, machines dominate human
efforts. Let us take the case of cash withdrawal from a bank ATM. The user
is required to press only a few buttons to authenticate his identity and the
amount he wishes to withdraw. Then within seconds the money pops out of
the ATM. During this process, the inside working of bank ATM is beyond
imagination of the user. Broadly speaking, the ATM receives certain data
from the user, processes it and gives the output (money). This is exactly what
a computer does. Formally, a computer can be defined as follows:
 “ An electronic device which is capable of receiving information (data) in
a particular form and of performing a sequence of operations in
accordance with a predetermined but variable set of
procedural instructions (program) to produce a result in the form of
information or signals.”
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Introduction
 computer performs basically five major functions
irrespective of its size and make.
 It accepts data or instructions by way of input
 It stores data
 It processes data as required by the user
 It controls operations of a computer
 It gives results in the form of output
INPUT PROCESS OUTPUT
I-P-O Cycle
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Block Diagram of Computer
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Block Diagram of Computer
 The above diagram describes the basic layout of a
computer. A computer receives data and instructions
through "Input Devices" which get processed in Central
Processing Unit, "CPU" and the result is shown through
"Output Devices". The "Main / primary Memory" and
"Secondary / Auxiliary Memory" are used to store
data inside the computer. These are the basic
components that each computer possess. Each of these
components exists in various types and variety that
differ in shape, size, usage and performance. The user
makes a choice according to his specific requirement.
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CPU
 Stands for Central Processing Unit
 Also known as the Brain of Computer.
 It convert the Input into Output
 CPU perform its operation with the help of its 2
subunits :-
 ALU : Arithmetic and Logic Unit
 CU : Control Unit
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ALU
 ALU Perform all the arithmetical and logical
operations.
 Arithmetic operations like +, -, *, /
 Logical operation like comparison or decision
making like: >, <, =, >=, <=, <>
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CU
 Control and guides the interpretation of all the
data and information.
 It coordinates the different units attached to
computer system.
 It takes input from Input device and store it in main
memory, then it send the data to ALU if any
arithmetic operation is required after this it transfer
the output to output devices.
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Memory of Computer
 Memory refers to the place where data is stored
temporarily or permanently.
 Input must goes to Memory Unit then only any action
on it can be performed.
 Computer Memory is basically of 2 types:
 Primary Memory
 Primary or main memory stores information(data and
instruction)
 Secondary Memory
 Stores the data permanently for future retreival
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Primary Memory
 Random Access Memory (RAM)
 It is the working memory, right from the booting of
computer till the computer is shutdown this memory is in
use to store all the operation done by the computer
 is used for primary storage in computers to hold active
information of data and instructions.
 It holds data temporarily i.e. Volatile Memory
 Data is lost if Power Off
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Primary Memory
 Read Only Memory (ROM)
 ROM (Read Only Memory) is used to store the
instructions provided by the manufacturer, which holds
the instructions to check basic hardware inter connecter
and to load operating system from appropriate
storage device
 It is also known as FIRMWARE
 Its data is stored permanently on it so it is non-volatile
device.
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Unit of Memory
GROUP OF KNOWN AS
4 BIT NIBBLE
8 BIT BYTE
1024 BYTES 1 KILO BYTE(KB)
1024 KB 1 MEGA BYTE(MB)
1024 MB 1 GIGA BYTE(GB)
1024 GB 1 TERA BYTE(TB)
1024 TB 1 PETA BYTE(PB)
The elementary unit of memory is a bit (binary digit)
Zero(0) & One(1)
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Secondary Storage Devices
 If we want to save data for future reference and retrieval
then it needs to be saved in memory other than primary
memory, which is called secondary memory, or auxiliary
memory. Normally hard disk of computer is used as
secondary memory but this is not portable so there are
many other secondary storage media in use.
 Example:
 Hard Disk
 CD/DVD
 Pen Drive
 Floppy, etc.
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 HARD DISK :
 A hard disk drive (HDD; also hard drive, hard disk, or disk
drive) is a device for storing and retrieving digital
information, primarily computer data.
 It consists of one or more rigid (hence "hard") rapidly
rotating discs (often referred to as platters), coated with
magnetic material and with magnetic heads arranged to
write data to the surfaces and read it from them.
 Generally hard disks are sealed units fixed in the cabinet. It
is also known as fixed disk
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 FLOPPY DISK : It is a data storage medium that is made
up of a disk of thin, flexible magnetic material enclosed in
a cover. Its capacity is 1.44 MB.
 COMPACT DISK (CD) : Capacity of standard 120mm CD
is 700MB. It is a thin optical disk which is commonly used
to store audio and video data. Transfer speed is
mentioned as multiple of 150 KB/s. 4x means 600 KB/s.
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 DIGITAL VIDEO DISK (DVD) : This is an optical disc
storage device. It can be recorded on single side or on
double side. Its capacity may range from 4.7 GB to
8.5 GB.
 PEN DRIVE :This is small, portable memory, which can be
plugged into a computer with USB Port.
They have capacity lesser than hard disk but much
larger than a floppy or CD. They are more reliable also.
They are also called pen drive.
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Input Devices
 These are the devices used to give input to
computer for processing.
 Input may be in form of text, images, audio, etc.
 Input Devices example:
 Keyboard
 Mouse
 Joystick
 Scanner
 Etc.
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KEYBOARD
Control Key
Alt KeyEnter Key
Numeric Keys
Function Keys
This is the most common input device which uses an arrangement of buttons or
keys. In a keyboard each press of a key typically corresponds to a single
written symbol. However some symbols require pressing and holding several
keys simultaneously or in sequence. While most keyboard keys produce
letters, numbers or characters, other keys or simultaneous key presses can
produce actions or computer commands.
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MOUSE
Mechanical Mouse Optical Mouse
Wired Wireless
A mouse is a pointing device that functions by detecting two-dimensional
motion relative to its supporting surface. The mouse's motion typically
translates into the motion of a cursor on a display, which allows for fine
control of a Graphical User Interface. A mouse primarily comprises of
three parts: the buttons, the handling area, and the rolling object. Using
left button of mouse different operations like selection, dragging, moving
and pasting can be done. With the right button we can open a context
menu for an item, if it is applicable.
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SCANNER
Scanner is a device that optically scans images,
printed text, handwriting, or an object, and
converts it to digital image.
JOYSTICK
A joystick is an input device consisting of a stick that pivots
on a base and reports its angle or direction to the device it
is controlling.
Many people use joysticks on computer games involving
flight such as flight simulator.
Joysticks are often used to control video games, and usually
have one or more push-buttons whose state can also be
read by the computer
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TOUCH SCREEN
A touch screen is a computer display screen that is also an input device.
The screens are sensitive to pressure; a user interacts with the computer
by touching pictures or words on the screen.
You may see it at as KIOSKS installed in various public places like ATM
machines, Railway’s PNR Checking machine etc.
MICROPHONE
It is used to input audio data into the computer. They are mainly used
for sound recording.
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OUTPUT DEVICE
 Output device is used to display the output to user
either in soft copy or hard copy.
 Soft copy output appears on monitor whereas hard
copy output appears on paper by printer.
 Various output devices are:
 Monitor
 Printer
 Speaker
 Projector etc.
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Monitor
 Also known as Visual Display Unit (VDU)
 It is the primary output device where we see the
output. It looks like TV.
 Its display may be CRT, LCD or LED
 CRT – Cathode ray tube
 LCD – Liquid Crystal Display
 LED – Light Emitting Diode
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Printer
 Printer produces output on paper.
 There are various types of printer available in
market like:
 Dot Matrix Printer : uses ribbon and hammer
technology. Its quality is not very good. Output is
printer by making object using small dots.
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Printer
 Inkjet/Deskjet Printer: is a type of computer printer that
creates a digital image by propelling droplets of ink onto
paper.
 Laser Printer : These printers use laser technology to
produce printed documents. These are very fast printers
and are used for high quality prints.
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CMOS
 complementary metal-oxide semiconductor
 CMOS is an onboard, battery powered semiconductor
chip inside computers that stores information.
 This information ranges from the system time and date to
system hardware settings for your computer.
 CMOS battery is generally used to give backup support
to BIOS program.
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BIOS
 The basic input/output system (BIOS) is also commonly
known as the System BIOS. The BIOS is boot firmware, a
small program that controls various electronic devices
attached to the main computer system.
 It is designed to be the first set of instructions run by a
Computer when powered on. The initial function of the
BIOS is to initialize system devices such as the RAM, hard
disk, CD/DVD drive, video display card, and other
hardware.
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Computer system organization || Class 11

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