Computer – Overview
Today’s world is an information-rich world and it has
become a necessity for everyone to know about computers. Purpose of this
tutorial is to introduce you about computer and its fundamentals.
Functionalities of a computer
Any digital computer carries out five functions in
gross terms:
·
Takes data as input.
·
Stores the
data/instructions in its memory and use them when required.
·
Processes the data and
converts it into useful information.
·
Generates the output
·
Controls all the above
four steps.
Definition
Computer is an electronic data processing device which
·
accepts and stores data
input,
·
processes the data
input, and
·
generates the output in
a required format.
Advantages
Following list demonstrates the advantages of
computers in today's arena.
High
Speed
·
Computer is a very fast
device.
·
It is capable of
performing calculation of very large amount of data.
·
The computer has units
of speed in microsecond, nanosecond, and even the picosecond.
·
It can perform millions
of calculations in a few seconds as compared to man who will spend many months
for doing the same task.
Accuracy
·
In addition to being
very fast, computers are very accurate.
·
The calculations are
100% error free.
·
Computers perform all
jobs with 100% accuracy provided that correct input has been given.
Storage
Capability
·
Memory is a very
important characteristic of computers.
·
A computer has much more
storage capacity than human beings.
·
It can store large
amount of data.
·
It can store any type of
data such as images, videos, text, audio and many others.
Diligence
·
Unlike human beings, a
computer is free from monotony, tiredness and lack of concentration.
·
It can work continuously
without any error and boredom.
·
It can do repeated work
with same speed and accuracy.
Versatility
·
A computer is a very
versatile machine.
·
A computer is very
flexible in performing the jobs to be done.
·
This machine can be used
to solve the problems related to various fields.
·
At one instance, it may
be solving a complex scientific problem and the very next moment it may be
playing a card game.
Reliability
·
A computer is a reliable
machine.
·
Modern electronic
components have long lives.
·
Computers are designed
to make maintenance easy.
Automation
·
Computer is an automatic
machine.
·
Automation means ability
to perform the given task automatically.
·
Once a program is given
to computer i.e., stored in computer memory, the program and instruction can
control the program execution without human interaction.
Reduction
in Paper Work
·
The use of computers for
data processing in an organization leads to reduction in paper work and results
in speeding up a process.
·
As data in electronic
files can be retrieved as and when required, the problem of maintenance of
large number of paper files gets reduced.
Reduction
in Cost
·
Though the initial
investment for installing a computer is high but it substantially reduces the
cost of each of its transaction.
Disadvantages
Following list demonstrates the disadvantages of
computers in today's arena
No
I.Q
·
A computer is a machine
that has no intelligence to perform any task.
·
Each instruction has to
be given to computer.
·
A computer cannot take
any decision on its own.
Dependency
·
It functions as per a
user’s instruction, so it is fully dependent on human being
Environment
·
The operating
environment of computer should be dust free and suitable.
No
Feeling
·
Computers have no
feelings or emotions.
·
It cannot make judgement
based on feeling, taste, experience, and knowledge unlike a human being.
Computer - Applications
Following list demonstrates various applications of
computers in today's arena.
Business
A computer has high speed of calculation, diligence,
accuracy, reliability, or versatility which made it an integrated part in all
business organisations.
Computer is used in business organisations for:
·
Payroll calculations
·
Budgeting
·
Sales analysis
·
Financial forecasting
·
Managing employees
database
·
Maintenance of stocks
etc.
Banking
Today banking is almost totally dependent on computer.
Banks provide following facilities:
·
Banks provide online
accounting facility, which includes current balances, deposits, overdrafts,
interest charges, shares, and trustee records.
·
ATM machines are making
it even easier for customers to deal with banks.
Insurance
Insurance companies are keeping all records up-to-date
with the help of computers. The insurance companies, finance houses and stock
broking firms are widely using computers for their concerns.
Insurance companies are maintaining a database of all
clients with information showing
·
procedure to continue
with policies
·
starting date of the
policies
·
next due installment of
a policy
·
maturity date
·
interests due
·
survival benefits
·
bonus
Education
The computer has provided a lot of facilities in the
education system.
·
The computer provides a
tool in the education system known as CBE (Computer Based Education).
·
CBE involves control,
delivery, and evaluation of learning.
·
The computer education
is rapidly increasing the graph of number of computer students.
·
There are number of
methods in which educational institutions can use computer to educate the
students.
·
It is used to prepare a
database about performance of a student and analysis is carried out on this
basis.
Marketing
In marketing, uses of computer are following:
·
Advertising - With computers, advertising professionals create art
and graphics, write and revise copy, and print and disseminate ads with the
goal of selling more products.
·
At Home Shopping - Home shopping has been made possible through use of
computerised catalogues that provide access to product information and permit
direct entry of orders to be filled by the customers.
Health Care
Computers have become important part in hospitals,
labs, and dispensaries. The computers are being used in hospitals to keep the
record of patients and medicines. It is also used in scanning and diagnosing
different diseases. ECG, EEG, Ultrasounds and CT Scans etc., are also done by
computerised machines.
Some major fields of health care in which computers
are used are:
·
Diagnostic System - Computers are used to collect data and identify cause
of illness.
·
Lab-diagnostic System - All tests can be done and reports are prepared by
computer.
·
Patient Monitoring
System - These are used to check patient's signs
for abnormality such as in Cardiac Arrest, ECG etc.
·
Pharma Information
System - Computer checks Drug-Labels, Expiry
dates, harmful drug’s side effects etc.
·
Surgery : Nowadays, computers are also used in performing surgery.
Engineering Design
Computers are widely used in Engineering purpose.
One of major areas is CAD (Computer aided design).
That provides creation and modification of images. Some fields are:
·
Structural Engineering - Requires stress and strain analysis for design of
Ships, Buildings, Budgets, Airplanes etc.
·
Industrial Engineering - Computers deal with design, implementation and
improvement of integrated systems of people, materials and equipments.
·
Architectural Engineering
- Computers help in planning towns,
designing buildings, determining a range of buildings on a site using both 2D
and 3D drawings.
Military
Computers are largely used in defence. Modern tanks,
missiles, weapons etc. Military also employs computerised control systems. Some
military areas where a computer has been used are:
·
Missile Control
·
Military Communication
·
Military Operation and
Planning
·
Smart Weapons
Communication
Communication means to convey a message, an idea, a
picture or speech that is received and understood clearly and correctly by the
person for whom it is meant for. Some main areas in this category are:
·
E-mail
·
Chatting
·
Usenet
·
FTP
·
Telnet
·
Video-conferencing
Government
Computers play an important role in government. Some
major fields in this category are:
·
Budgets
·
Sales tax department
·
Income tax department
·
Male/Female ratio
·
Computerization of
voters lists
·
Computerization of
driving licensing system
·
Computerization of PAN
card
·
Weather forecasting
Computer Generations
OBJECTIVES OF COMPUTER GENERATION
1)
Technological development
2)
Processing mode
3)
System architecture
4)
Language used
The period of first generation was
1946-1959. The computers of first generation used vacuum tubes as the basic
components for memory and circuitry for CPU (Central Processing Unit). These
tubes, like electric bulbs, produced a lot of heat and were prone to frequent
fusing of the installations, therefore, were very expensive and could be
afforded only by very large organisations. In this generation mainly batch
processing operating system were used. Punched cards, paper tape, and magnetic
tape were used as input and output devices. The computers in this generation
used machine code as programming language.
The main features of first generation are:
·
Vacuum tube technology
·
Unreliable
·
Supported machine
language only
·
Very costly
·
Generated lot of heat
·
Slow input and output
devices
·
Huge size
·
Need of A.C.
·
Non-portable
·
Consumed lot of
electricity
Some computers of this generation were:
·
ENIAC
·
EDVAC
·
UNIVAC
·
IBM-701
·
IBM-650
Second Generation
The period of second generation was
1959-1965. In this generation transistors were used that were cheaper, consumed
less power, more compact in size, more reliable and faster than the first
generation machines made of vacuum tubes. In this generation, magnetic cores
were used as primary memory and magnetic tape and magnetic disks as secondary
storage devices. In this generation assembly language and high-level
programming languages like FORTRAN, COBOL were used. The computers used batch
processing and multiprogramming operating system.
The main features of second generation are:
·
Use of transistors
·
Reliable in comparison
to first generation computers
·
Smaller size as compared
to first generation computers
·
Generated less heat as
compared to first generation computers
·
Consumed less
electricity as compared to first generation computers
·
Faster than first
generation computers
·
Still very costly
·
A.C. needed
·
Supported machine and
assembly languages
Some computers of this generation were:
·
IBM 1620
·
IBM 7094
·
CDC 1604
·
CDC 3600
·
UNIVAC 1108
Third Generation
The period of third generation was
1965-1971. The computers of third generation used integrated circuits (IC's) in
place of transistors. A single IC has many transistors, resistors and
capacitors along with the associated circuitry. The IC was invented by Jack
Kilby. This development made computers smaller in size, reliable and efficient.
In this generation remote processing, time-sharing, multi-programming operating
system were used. High-level languages (FORTRAN-II TO IV, COBOL, PASCAL PL/1,
BASIC, ALGOL-68 etc.) were used during this generation.
The main features of third generation are:
·
IC used
·
More reliable in
comparison to previous two generations
·
Smaller size
·
Generated less heat
·
Faster
·
Lesser maintenance
·
Still costly
·
A.C needed
·
Consumed lesser electricity
·
Supported high-level
language
Some computers of this generation were:
·
IBM-360 series
·
Honeywell-6000 series
·
PDP(Personal Data
Processor)
·
IBM-370/168
·
TDC-316
Fourth Generation
The period of fourth generation was
1971-1980. The computers of fourth generation used Very Large Scale Integrated
(VLSI) circuits. VLSI circuits having about 5000 transistors and other circuit
elements and their associated circuits on a single chip made it possible to
have microcomputers of fourth generation. Fourth generation computers became
more powerful, compact, reliable, and affordable. As a result, it gave rise to
personal computer (PC) revolution. In this generation time sharing, real time,
networks, distributed operating system were used. All the high-level languages
like C, C++, DBASE etc., were used in this generation.
The main features of fourth generation are:
·
VLSI technology used
·
Very cheap
·
Portable and reliable
·
Use of PC's
·
Very small size
·
Pipeline processing
·
No A.C. needed
·
Concept of internet was
introduced
·
Great developments in
the fields of networks
·
Computers became easily
available
Some computers of this generation were:
·
DEC 10
·
STAR 1000
·
PDP 11
·
CRAY-1(Super Computer)
·
CRAY-X-MP(Super
Computer)
Fifth Generation
The period of fifth generation is
1980-till date. In the fifth generation, the VLSI technology became ULSI (Ultra
Large Scale Integration) technology, resulting in the production of
microprocessor chips having ten million electronic components. This generation
is based on parallel processing hardware and AI (Artificial Intelligence)
software. AI is an emerging branch in computer science, which interprets means
and method of making computers think like human beings. All the high-level
languages like C and C++, Java, .Net etc., are used in this generation
AI includes:
·
Robotics
·
Neural Networks
·
Game Playing
·
Development of expert
systems to make decisions in real life situations.
·
Natural language
understanding and generation.
The main features of fifth generation are:
·
ULSI technology
·
Development of true
artificial intelligence
·
Development of Natural
language processing
·
Advancement in Parallel
Processing
·
Advancement in
Superconductor technology
·
More user friendly
interfaces with multimedia features
·
Availability of very
powerful and compact computers at cheaper rates
Some computer types of this generation are:
·
Desktop
·
Laptop
·
NoteBook
·
UltraBook
·
ChromeBook
·
Android phones
·
Tablets/ ipod/ipad/
·
Computer - Types
·
Computers can be broadly
classified by their speed and computing power.
Sr.No.
|
Type
|
Specifications
|
1
|
PC (Personal Computer)
|
It is a single user computer system having
moderately powerful microprocessor
|
2
|
WorkStation
|
It is also a single user computer system which is
similar to personal computer but have more powerful microprocessor.
|
3
|
Mini Computer
|
It is a multi-user computer system which is capable
of supporting hundreds of users simultaneously.
|
4
|
Main Frame
|
It is a multi-user computer system which is capable
of supporting hundreds of users simultaneously. Software technology is
different from minicomputer.
|
5
|
Supercomputer
|
It is an extremely fast computer which can execute
hundreds of millions of instructions per second.
|
·
PC (Personal Computer)
·
A PC can be defined as a
small, relatively inexpensive computer designed for an individual user. PCs are
based on the microprocessor technology that enables manufacturers to put an
entire CPU on one chip. Businesses use personal computers for word processing,
accounting, desktop publishing, and for running spreadsheet and database
management applications. At home, the most popular use for personal computers
is playing games and surfing Internet.
·
Although personal
computers are designed as single-user systems, these systems are normally
linked together to form a network. In terms of power, now-a-days High-end
models of the Macintosh and PC offer the same computing power and graphics
capability as low-end workstations by Sun Microsystems, Hewlett-Packard, and
Dell.
·
·
Workstation
·
Workstation is a
computer used for engineering applications (CAD/CAM), desktop publishing, software
development, and other such types of applications which require a moderate
amount of computing power and relatively high quality graphics capabilities.
·
Workstations generally
come with a large, high-resolution graphics screen, large amount of RAM,
inbuilt network support, and a graphical user interface. Most workstations also
have a mass storage device such as a disk drive, but a special type of
workstation, called a diskless workstation, comes without a disk drive.
·
Common operating systems
for workstations are UNIX and Windows NT. Like PC, Workstations are also
single-user computers like PC but are typically linked together to form a
local-area network, although they can also be used as stand-alone systems.
·
Minicomputer
·
It is a midsize
multi-processing system capable of supporting up to 250 users simultaneously.
·
·
Mainframe
·
Mainframe is very large
in size and is an expensive computer capable of supporting hundreds or even
thousands of users simultaneously. Mainframe executes many programs concurrently
and supports many simultaneous execution of programs
·
Supercomputer
·
Supercomputers are one
of the fastest computers currently available. Supercomputers are very expensive
and are employed for specialized applications that require immense amount of mathematical
calculations (number crunching). For example, weather forecasting, scientific
simulations, (animated) graphics, fluid dynamic calculations, nuclear energy
research, electronic design, and analysis of geological data (e.g. in
petrochemical prospecting).
Computer – Components
All types of computers follow a same basic
logical structure and perform the following five basic operations for
converting raw input data into information useful to their users.
Sr.No.
|
Operation
|
Description
|
1
|
Take Input
|
The process of entering data and instructions into
the computer system
|
2
|
Store Data
|
Saving data and instructions so that they are
available for processing as and when required.
|
3
|
Processing Data
|
Performing arithmetic, and logical operations on
data in order to convert them into useful information.
|
4
|
Output Information
|
The process of producing useful information or
results for the user, such as a printed report or visual display.
|
5
|
Control the workflow
|
Directs the manner and sequence in which all of the
above operations are performed.
|
Input Unit
This unit contains devices with the help of which we
enter data into computer. This unit makes link between user and computer. The
input devices translate the information into the form understandable by computer.
CPU (Central Processing Unit)
CPU is considered as the brain of the computer. CPU
performs all types of data processing operations. It stores data, intermediate
results and instructions(program). It controls the operation of all parts of
computer.
CPU itself has following three components
·
ALU(Arithmetic Logic
Unit)
·
Memory Unit
·
Control Unit
Output Unit
Output unit consists of devices with the help of which
we get the information from computer. This unit is a link between computer and
users. Output devices translate the computer's output into the form
understandable by users.
CPU(Central Processing Unit)
CPU consists of the following features:
·
CPU is considered as the
brain of the computer.
·
CPU performs all types
of data processing operations.
·
It stores data,
intermediate results and instructions(program).
·
It controls the
operation of all parts of computer.
CPU itself has following three components.
·
Memory or Storage Unit
·
Control Unit
·
ALU(Arithmetic Logic
Unit)
Memory or Storage Unit
This unit can store instructions, data and
intermediate results. This unit supplies information to the other units of the
computer when needed. It is also known as internal storage unit or main memory
or primary storage or Random access memory(RAM).
Its size affects speed, power and capability. Primary
memory and secondary memory are two types of memories in the computer.
Functions of memory unit are:
·
It stores all the data
and the instructions required for processing.
·
It stores intermediate
results of processing.
·
It stores final results
of processing before these results are released to an output device.
·
All inputs and outputs
are transmitted through main memory.
Control Unit
This unit controls the operations of all parts of
computer but does not carry out any actual data processing operations.
Functions of this unit are:
·
It is responsible for
controlling the transfer of data and instructions among other units of a
computer.
·
It manages and
coordinates all the units of the computer.
·
It obtains the
instructions from the memory, interprets them, and directs the operation of the
computer.
·
It communicates with
Input/Output devices for transfer of data or results from storage.
·
It does not process or
store data.
ALU(Arithmetic Logic Unit)
This unit consists of two subsections namely
·
Arithmetic section
·
Logic Section
Arithmetic
Section
Function of arithmetic section is to perform
arithmetic operations like addition, subtraction, multiplication and division.
All complex operations are done by making repetitive use of above operations.
Logic
Section
Function of logic section is to perform logic
operations such as comparing, selecting, matching and merging of data.
Input Devices
Following are few of the important input devices which
are used in a computer:
·
Keyboard
·
Mouse
·
Joy Stick
·
Light pen
·
Track Ball
·
Scanner
·
Graphic Tablet
·
Microphone
·
Magnetic Ink Card
Reader(MICR)
·
Optical Character
Reader(OCR)
·
Bar Code Reader
·
Optical Mark Reader(OMR)
Keyboard
Keyboard is the most common and very popular input
device which helps in inputting data to the computer. The layout of the
keyboard is like that of traditional typewriter, although there are some
additional keys provided for performing additional functions.
Keyboards are of two sizes 84 keys or 101/102 keys,
but now keyboards with 104 keys or 108 keys are also available for Windows and
Internet.
The keys on the keyboard are as follows:
Sr.No
|
Keys
|
Description
|
1
|
Typing Keys
|
These keys include the letter keys (A-Z) and digit
keys (0-9) which generally give same layout as that of typewriters.
|
2
|
Numeric Keypad
|
It is used to enter numeric data or cursor movement.
Generally, it consists of a set of 17 keys that are laid out in the same
configuration used by most adding machines and calculators.
|
3
|
Function Keys
|
The twelve function keys are present on the keyboard
which are arranged in a row at the top of the keyboard. Each function key has
unique meaning and is used for some specific purpose.
|
4
|
Control keys
|
These keys provide cursor and screen control. It
includes four directional arrow keys. Control keys also include Home, End,
Insert, Delete, Page Up, Page Down, Control(Ctrl), Alternate(Alt),
Escape(Esc).
|
5
|
Special Purpose Keys
|
Keyboard also contains some special purpose keys
such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen.
|
Mouse
Mouse is most popular pointing device. It is a very
famous cursor-control device having a small palm size box with a round ball at
its base which senses the movement of mouse and sends corresponding signals to
CPU when the mouse buttons are pressed.
Generally it has two buttons called left and right
button and a wheel is present between the buttons. Mouse can be used to control
the position of cursor on screen, but it cannot be used to enter text into the
computer.
Advantages
·
Easy to use
·
Not very expensive
·
Moves the cursor faster
than the arrow keys of keyboard.
·
Joystick
·
Joystick is also a
pointing device which is used to move cursor position on a monitor screen. It
is a stick having a spherical ball at its both lower and upper ends. The lower
spherical ball moves in a socket. The joystick can be moved in all four
directions.
·
The function of joystick
is similar to that of a mouse. It is mainly used in Computer Aided
Designing(CAD) and playing computer games.
·
Light Pen
·
Light pen is a pointing
device which is similar to a pen. It 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 the tip of a light pen is moved over the
monitor screen and pen button is pressed, its photocell sensing element detects
the screen location and sends the corresponding signal to the CPU.
·
Track Ball
·
Track ball is an input
device that is mostly used in notebook or laptop computer, instead of a mouse.
This is a ball which is half inserted and by moving fingers on ball, pointer
can be moved. Since the whole device is not moved, a track ball requires less
space than a mouse. A track ball comes in various shapes like a ball, a button
and a square.
·
Scanner
·
Scanner is an input
device which works more like a photocopy machine. It is used when some
information is available on a paper and it is to be transferred to the hard
disc of the computer for further manipulation. Scanner captures images from the
source which are then converted into the digital form that can be stored on the
disc. These images can be edited before they are printed.
·
Digitizer
·
Digitizer is an input
device which converts analog information into digital form. Digitizer can
convert a signal from the television or camera into a series of numbers that
could be stored in a computer. They can be used by the computer to create a
picture of whatever the camera had been pointed at. Digitizer is also known as
Tablet or Graphics Tablet because it converts graphics and pictorial data into
binary inputs. A graphic tablet as digitizer is used for doing fine works of
drawing and image manipulation applications.
·
Microphone
·
Microphone is an input
device to input sound that is then stored in digital form. The microphone is
used for various applications like adding sound to a multimedia presentation or
for mixing music.
·
Magnetic Ink Card Reader(MICR)
·
MICR input device is
generally used in banks because of a large number of cheques to be processed every
day. The bank's code number and cheque number are printed on the cheques with a
special type of ink that contains particles of magnetic material that are
machine readable. This reading process is called Magnetic Ink Character
Recognition (MICR). The main advantages of MICR is that it is fast and less
error prone.
·
Optical Character Reader(OCR)
·
OCR is an input device
used to read a printed text. OCR scans text optically character by character,
converts them into a machine readable code and stores the text on the system
memory.
·
Bar Code Readers
·
Bar Code Reader is a
device used for reading bar coded data (data in form of light and dark lines).
Bar coded data is generally used in labelling goods, numbering the books etc.
It may be a hand held scanner or may be embedded in a stationary scanner. Bar
Code Reader scans a bar code image, converts it into an alphanumeric value
which is then fed to the computer to which bar code reader is connected.
·
Optical Mark Reader(OMR)
·
OMR is a special type of
optical scanner used to recognize the type of mark made by pen or pencil. It is
used where one out of a few alternatives is to be selected and marked. It is
specially used for checking the answer sheets of examinations having multiple
choice questions.
Output Devices
Following are few of the important output devices
which are used in a computer.
·
Monitors
·
Graphic Plotter
·
Printer
Monitors
Monitors, commonly called as Visual Display Unit
(VDU), are the main output device of a computer. It forms images from tiny
dots, called pixels that are arranged in a rectangular form. The sharpness of
the image depends upon the number of pixels.
There are two kinds of viewing screen used for
monitors.
·
Cathode-Ray Tube (CRT)
·
Flat- Panel Display
Cathode-Ray
Tube (CRT) Monitor
The CRT display is made up of small picture elements
called pixels. The smaller the pixels, the better the image clarity, or
resolution. It takes more than one illuminated pixel to form whole character,
such as the letter ‘e’ in the word help.
A finite number of characters can be displayed on a
screen at once. The screen can be divided into a series of character boxes -
fixed location on the screen where a standard character can be placed. Most
screens are capable of displaying 80 characters of data horizontally and 25
lines vertically. There are some disadvantages of CRT:
·
Large in Size
·
High power consumption
Flat-Panel
Display Monitor
The flat-panel display refers to a class of video
devices that have reduced volume, weight and power requirement in comparison to
the CRT. You can hang them on walls or wear them on your wrists. Current uses
of flat-panel displays include calculators, video games, monitors, laptop
computer, graphics display.
The flat-panel display is divided into two categories:
·
Emissive Displays - The emissive displays are devices that convert
electrical energy into light. Example are plasma panel and LED(Light-Emitting
Diodes).
·
Non-Emissive Displays - The Non-emissive displays use optical effects to
convert sunlight or light from some other source into graphics patterns.
Example is LCD(Liquid-Crystal Device)
Printers
Printer is an output device, which is used to print
information on paper.
There are two types of printers:
·
Impact Printers
·
Non-Impact Printers
Impact Printers
The impact printers print the characters by striking
them on the ribbon which is then pressed on the paper.
Characteristics of Impact Printers are the following:
·
Very low consumable
costs
·
Very noisy
·
Useful for bulk printing
due to low cost
·
There is physical
contact with the paper to produce an image
These printers are of two types
·
Character printers
·
Line printers
Character
Printers
Character printers are the printers which print one
character at a time.
These are further divided into two types:
·
Dot Matrix Printer(DMP)
·
Daisy Wheel
Dot Matrix Printer
In the market one of the most popular printers is Dot
Matrix Printer. These printers are popular because of their ease of printing
and economical price. Each character printed is in form of pattern of dots and
head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out
to form a character that is why it is called Dot Matrix Printer.
Advantages
·
Inexpensive
·
Widely Used
·
Other language
characters can be printed
Disadvantages
·
Slow Speed
·
Poor Quality
Daisy Wheel
Head is lying on a wheel and pins corresponding to
characters are like petals of Daisy (flower name) that is why it is called
Daisy Wheel Printer. These printers are generally used for word-processing in
offices which require a few letters to be sent here and there with very nice
quality.
Advantages
·
More reliable than DMP
·
Better quality
·
The fonts of character
can be easily changed
Disadvantages
·
Slower than DMP
·
Noisy
·
More expensive than DMP
Line
Printers
Line printers are the printers which print one line at
a time.
These are of further two types
·
Drum Printer
·
Chain Printer
Drum Printer
This printer is like a drum in shape so it is called
drum printer. The surface of drum is divided into number of tracks. Total
tracks are equal to size of paper i.e. for a paper width of 132 characters,
drum will have 132 tracks. A character set is embossed on track. The different
character sets available in the market are 48 character set, 64 and 96
characters set. One rotation of drum prints one line. Drum printers are fast in
speed and can print 300 to 2000 lines per minute.
Advantages
·
Very high speed
Disadvantages
·
Very expensive
·
Characters fonts cannot
be changed
Chain Printer
In this printer, chain of character sets are used so
it is called Chain Printer. A standard character set may have 48, 64, or 96
characters.
Advantages
·
Character fonts can
easily be changed.
·
Different languages can
be used with the same printer.
Disadvantages
·
Noisy
Non-impact Printers
Non-impact printers print the characters without using
ribbon. These printers print a complete page at a time so they are also called
as Page Printers.
These printers are of two types
·
Laser Printers
·
Inkjet Printers
Characteristics of Non-impact Printers
·
Faster than impact
printers.
·
They are not noisy.
·
High quality.
·
Support many fonts and
different character size.
Laser
Printers
These are non-impact page printers. They use laser
lights to produce the dots needed to form the characters to be printed on a
page.
Advantages
·
Very high speed
·
Very high quality output
·
Give good graphics
quality
·
Support many fonts and
different character size
Disadvantages
·
Expensive.
·
Cannot be used to
produce multiple copies of a document in a single printing.
Inkjet
Printers
Inkjet printers are non-impact character printers
based on a relatively new technology. They print characters by spraying small
drops of ink onto paper. Inkjet printers produce high quality output with
presentable features.
They make less noise because no hammering is done and
these have many styles of printing modes available. Colour printing is also
possible. Some models of Inkjet printers can produce multiple copies of
printing also.
Advantages
·
High quality printing
·
More reliable
Disadvantages
·
Expensive as cost per
page is high
·
Slow as compared to
laser printer
Memory
A memory is just like a human brain. It is used to
store data and instructions. Computer memory is the storage space in computer
where data is to be processed and instructions required for processing are
stored. The memory is divided into large number of small parts called cells.
Each location or cell has a unique address which varies from zero to memory
size minus one. For example if computer has 64k words, then this memory unit
has 64 * 1024=65536 memory locations. The address of these locations varies
from 0 to 65535.
Memory is primarily of three types
·
Cache Memory
·
Primary Memory/Main
Memory
·
Secondary Memory
Cache Memory
Cache memory is a very high speed semiconductor memory
which can speed up CPU. It acts as a buffer between the CPU and main memory. It
is used to hold those parts of data and program which are most frequently used
by CPU. The parts of data and programs are transferred from disk to cache
memory by operating system, from where CPU can access them.
Advantages
The advantages of cache memory are as follows:
·
Cache memory is faster
than main memory.
·
It consumes less access
time as compared to main memory.
·
It stores the program
that can be executed within a short period of time.
·
It stores data for
temporary use.
Disadvantages
The disadvantages of cache memory are as follows:
·
Cache memory has limited
capacity.
·
It is very expensive.
Primary Memory (Main Memory)
Primary memory holds only those data and instructions
on which computer is currently working. It has limited capacity and data is
lost when power is switched off. It is generally made up of semiconductor
device. These memories are not as fast as registers. The data and instruction
required to be processed reside in main memory. It is divided into two
subcategories RAM and ROM.
Characteristics
of Main Memory
·
These are semiconductor
memories
·
It is known as main
memory.
·
Usually volatile memory.
·
Data is lost in case
power is switched off.
·
It is working memory of
the computer.
·
Faster than secondary
memories.
·
A computer cannot run
without primary memory.
Secondary Memory
This type of memory is also known as external memory
or non-volatile. It is slower than main memory. These are used for storing
data/Information permanently. CPU directly does not access these memories
instead they are accessed via input-output routines. Contents of secondary memories
are first transferred to main memory, and then CPU can access it. For example :
disk, CD-ROM, DVD etc.
Characteristic
of Secondary Memory
·
These are magnetic and
optical memories
·
It is known as backup
memory.
·
It is non-volatile
memory.
·
Data is permanently
stored even if power is switched off.
·
It is used for storage
of data in a computer.
·
Computer may run without
secondary memory.
·
Slower than primary
memories.
Random Access Memory
RAM(Random Access Memory) is the internal memory of
the CPU for storing data, program and program result. It is read/write memory
which stores data until the machine is working. As soon as the machine is
switched off, data is erased.
Access time in RAM is independent of the address that
is, each storage location inside the memory is as easy to reach as other
locations and takes the same amount of time. Data in the RAM can be accessed
randomly but it is very expensive.
RAM is volatile, i.e. data stored in it is lost when
we switch off the computer or if there is a power failure. Hence a backup
uninterruptible power system(UPS) is often used with computers. RAM is small,
both in terms of its physical size and in the amount of data it can hold.
RAM is of two types
·
Static RAM (SRAM)
·
Dynamic RAM (DRAM)
Static RAM (SRAM)
The word static indicates that the memory
retains its contents as long as power is being supplied. However, data is lost
when the power gets down due to volatile nature. SRAM chips use a matrix of
6-transistors and no capacitors. Transistors do not require power to prevent
leakage, so SRAM need not have to be refreshed on a regular basis.
Because of the extra space in the matrix, SRAM uses
more chips than DRAM for the same amount of storage space, thus making the
manufacturing costs higher. So SRAM is used as cache memory and has very fast
access.
Characteristic
of the Static RAM
·
It has long life
·
There is no need to
refresh
·
Faster
·
Used as cache memory
·
Large size
·
Expensive
·
High power consumption
Dynamic RAM (DRAM)
DRAM, unlike SRAM, must be continually refreshed
in order to maintain the data. This is done by placing the memory on a refresh
circuit that rewrites the data several hundred times per second. DRAM is used
for most system memory because it is cheap and small. All DRAMs are made up of
memory cells which are composed of one capacitor and one transistor.
Characteristics
of the Dynamic RAM
·
It has short data
lifetime
·
Need to be refreshed
continuously
·
Slower as compared to
SRAM
·
Used as RAM
·
Lesser in size
·
Less expensive
·
Less power consumption
RAM(Random Access Memory) is the internal memory of
the CPU for storing data, program and program result. It is read/write memory
which stores data until the machine is working. As soon as the machine is
switched off, data is erased.
Access time in RAM is independent of the address that
is, each storage location inside the memory is as easy to reach as other
locations and takes the same amount of time. Data in the RAM can be accessed
randomly but it is very expensive.
RAM is volatile, i.e. data stored in it is lost when
we switch off the computer or if there is a power failure. Hence a backup
uninterruptible power system(UPS) is often used with computers. RAM is small,
both in terms of its physical size and in the amount of data it can hold.
RAM is of two types
·
Static RAM (SRAM)
·
Dynamic RAM (DRAM)
Static RAM (SRAM)
The word static indicates that the memory
retains its contents as long as power is being supplied. However, data is lost
when the power gets down due to volatile nature. SRAM chips use a matrix of
6-transistors and no capacitors. Transistors do not require power to prevent
leakage, so SRAM need not have to be refreshed on a regular basis.
Because of the extra space in the matrix, SRAM uses
more chips than DRAM for the same amount of storage space, thus making the
manufacturing costs higher. So SRAM is used as cache memory and has very fast
access.
Characteristic
of the Static RAM
·
It has long life
·
There is no need to
refresh
·
Faster
·
Used as cache memory
·
Large size
·
Expensive
·
High power consumption
Dynamic RAM (DRAM)
DRAM, unlike SRAM, must be continually refreshed
in order to maintain the data. This is done by placing the memory on a refresh
circuit that rewrites the data several hundred times per second. DRAM is used
for most system memory because it is cheap and small. All DRAMs are made up of
memory cells which are composed of one capacitor and one transistor.
Characteristics
of the Dynamic RAM
·
It has short data
lifetime
·
Need to be refreshed
continuously
·
Slower as compared to
SRAM
·
Used as RAM
·
Lesser in size
·
Less expensive
·
Less power consumption
Read Only Memory
ROM stands for Read Only Memory. The memory from which
we can only read but cannot write on it. This type of memory is non-volatile.
The information is stored permanently in such memories during manufacture. A
ROM, stores such instructions that are required to start a computer. This
operation is referred to as bootstrap. ROM chips are not only used in the
computer but also in other electronic items like washing machine and microwave
oven.
Following are the various types of ROM
MROM (Masked ROM)
The very first ROMs were hard-wired devices that
contained a pre-programmed set of data or instructions. These kind of ROMs are
known as masked ROMs which are inexpensive.
PROM (Programmable Read only Memory)
PROM is read-only memory that can be modified only
once by a user. The user buys a blank PROM and enters the desired contents
using a PROM program. Inside the PROM chip there are small fuses which are
burnt open during programming. It can be programmed only once and is not
erasable.
EPROM(Erasable and Programmable Read Only Memory)
The EPROM can be erased by exposing it to ultra-violet
light for a duration of up to 40 minutes. Usually, an EPROM eraser achieves
this function. During programming, an electrical charge is trapped in an
insulated gate region. The charge is retained for more than ten years because
the charge has no leakage path. For erasing this charge, ultra-violet light is
passed through a quartz crystal window(lid). This exposure to ultra-violet
light dissipates the charge. During normal use the quartz lid is sealed with a
sticker.
EEPROM(Electrically Erasable and Programmable Read
Only Memory)
The EEPROM is programmed and erased electrically. It
can be erased and reprogrammed about ten thousand times. Both erasing and
programming take about 4 to 10 ms (milli second). In EEPROM, any location can
be selectively erased and programmed. EEPROMs can be erased one byte at a time,
rather than erasing the entire chip. Hence, the process of re-programming is
flexible but slow.
Advantages of ROM
The advantages of ROM are as follows:
·
Non-volatile in nature
·
These cannot be
accidentally changed
·
Cheaper than RAMs
·
Easy to test
·
More reliable than RAMs
·
These are static and do
not require refreshing
·
Its contents are always
known and can be verified
Motherboard
The motherboard serves as a single platform to connect
all of the parts of a computer together. A motherboard connects CPU, memory,
hard drives, optical drives, video card, sound card, and other ports and
expansion cards directly or via cables. It can be considered as the backbone of
a computer.
Features of Motherboard
A motherboard comes with following features:
·
Motherboard varies
greatly in supporting various types of components.
·
Normally a motherboard
supports a single type of CPU and few types of memories.
·
Video Cards, Hard disks,
Sound Cards have to be compatible with motherboard to function properly
·
Motherboards, cases and
power supplies must be compatible to work properly together.
Popular Manufacturers
·
Intel
·
ASUS
·
AOpen
·
ABIT
·
Biostar
·
Gigabyte
·
MSI
Description of Motherboard
The motherboard is mounted inside the case and is
securely attached via small screws through pre-drilled holes. Motherboard
contains ports to connect all of the internal components. It provides a single
socket for CPU whereas for memory, normally one or more slots are available.
Motherboards provide ports to attach floppy drive, hard drive, and optical
drives via ribbon cables. Motherboard carries fans and a special port designed
for power supply.
There is a peripheral card slot in front of the motherboard
using which video cards, sound cards and other expansion cards can be connected
to motherboard.
On the left side, motherboards carry a number of ports
to connect monitor, printer, mouse, keyboard, speaker, and network cables.
Motherboards also provide USB ports which allow compatible devices to be
connected in plug-in/plug-out fashion for example, pen drive, digital cameras
etc.
Memory Units
Memory unit is:
·
the amount of data that
can be stored in the storage unit.
·
that in which storage
capacity is expressed in terms of Bytes.
Following are the main memory storage units:
Sr.No.
|
Unit
|
Description
|
1
|
Bit (Binary Digit)
|
A binary digit is logical 0 and 1 representing a
passive or an active state of a component in an electric circuit.
|
2
|
Nibble
|
A group of 4 bits is called nibble.
|
3
|
Byte
|
A group of 8 bits is called byte. A byte is the
smallest unit which can represent a data item or a character.
|
4
|
Word
|
A computer word, like a byte, is a group of fixed
number of bits processed as a unit which varies from computer to computer but
is fixed for each computer.
The length of a computer word is called word-size or
word length and it may be as small as 8 bits or may be as long as 96 bits. A
computer stores the information in the form of computer words.
|
Few higher storage units are following
Sr.No.
|
Unit
|
Description
|
1
|
Kilobyte (KB)
|
1 KB = 1024 Bytes
|
2
|
Megabyte (MB)
|
1 MB = 1024 KB
|
3
|
GigaByte (GB)
|
1 GB = 1024 MB
|
4
|
TeraByte (TB
|
1 TB = 1024 GB
|
5
|
PetaByte (PB)
|
1 PB = 1024 TB
|
Ports
What is a Port?
A port:
·
is a physical docking
point using which an external device can be connected to the computer.
·
can also be programmatic
docking point through which information flows from a program to computer or
over the internet.
Characteristics
A port has the following characteristics:
·
External devices are
connected to a computer using cables and ports.
·
Ports are slots on the
motherboard into which a cable of external device is plugged in.
·
Examples of external
devices attached via ports are mouse, keyboard, monitor, microphone, speakers
etc.
Following are few important types of ports:
Serial
Port
·
Used for external modems
and older computer mouse
·
Two versions : 9 pin, 25
pin model
·
Data travels at 115
kilobits per second
Parallel
Port
·
Used for scanners and
printers
·
Also called printer port
·
25 pin model
·
Also known as IEEE
1284-compliant Centronics port
PS/2
Port
·
Used for old computer
keyboard and mouse
·
Also called mouse port
·
Most of the old
computers provide two PS/2 port, each for mouse and keyboard
·
Also known as IEEE 1284-compliant
Centronics port
Universal
Serial Bus (or USB) Port
·
It can connect all kinds
of external USB devices such as external hard disk, printer, scanner, mouse,
keyboard etc.
·
It was introduced in
1997.
·
Most of the computers
provide two USB ports as minimum.
·
Data travels at 12
megabits per seconds
·
USB compliant devices
can get power from a USB port
VGA
Port
·
Connects monitor to a
computer's video card.
·
Has 15 holes.
·
Similar to serial port
connector but serial port connector has pins, it has holes.
Power
Connector
·
Three-pronged plug
·
Connects to the
computer's power cable that plugs into a power bar or wall socket
Firewire
Port
·
Transfers large amount
of data at very fast speed.
·
Connects camcorders and
video equipments to the computer
·
Data travels at 400 to
800 megabits per seconds
·
Invented by Apple
·
Three variants : 4-Pin
FireWire 400 connector, 6-Pin FireWire 400 connector and 9-Pin FireWire 800
connector
Modem
Port
·
Connects a PC's modem to
the telephone network
Ethernet
Port
·
Connects to a network
and high speed Internet.
·
Connect network cable to
a computer.
·
This port resides on an
Ethernet Card.
·
Data travels at 10
megabits to 1000 megabits per seconds depending upon the network bandwidth.
Game
Port
·
Connect a joystick to a
PC
·
Now replaced by USB.
Digital
Video Interface, DVI port
·
Connects Flat panel LCD
monitor to the computer's high end video graphic cards.
·
Very popular among video
card manufacturers.
Sockets
·
Connect microphone,
speakers to sound card of the computer
Hardware
Hardware represents the physical and tangible
components of a computer i.e. the components that can be seen and touched.
Examples of Hardware are following:
·
Input devices -- keyboard, mouse etc.
·
Output devices -- printer, monitor etc.
·
Secondary storage
devices -- Hard disk, CD, DVD etc.
·
Internal components -- CPU, motherboard, RAM etc.
Relationship between Hardware and Software
·
Hardware and software
are mutually dependent on each other. Both of them must work together to make a
computer produce a useful output.
·
Software cannot be
utilized without supporting hardware.
·
Hardware without set of
programs to operate upon cannot be utilized and is useless.
·
To get a particular job
done on the computer, relevant software should be loaded into the hardware
·
Hardware is a one-time
expense.
·
Software development is
very expensive and is a continuing expense.
·
Different software
applications can be loaded on a hardware to run different jobs.
·
A software acts as an
interface between the user and the hardware.
·
If hardware is the
'heart' of a computer system, then software is its 'soul'. Both are
complimentary to each other.
Software
Software is a set of programs, which is designed to
perform a well-defined function. A program is a sequence of instructions
written to solve a particular problem.
There are two types of software
·
System Software
·
Application Software
System Software
The system software is collection of programs designed
to operate, control, and extend the processing capabilities of the computer
itself. System software are generally prepared by computer manufactures. These
software products comprise of programs written in low-level languages which
interact with the hardware at a very basic level. System software serves as the
interface between hardware and the end users.
Some examples of system software are Operating System,
Compilers, Interpreter, Assemblers etc.
Features of system software are as follows:
·
Close to system
·
Fast in speed
·
Difficult to design
·
Difficult to understand
·
Less interactive
·
Smaller in size
·
Difficult to manipulate
·
Generally written in
low-level language
Application Software
Application software products are designed to satisfy
a particular need of a particular environment. All software applications
prepared in the computer lab can come under the category of Application
software.
Application software may consist of a single program,
such as a Microsoft's notepad for writing and editing simple text. It may also
consist of a collection of programs, often called a software package, which
work together to accomplish a task, such as a spreadsheet package.
Examples of Application software are following:
·
Payroll Software
·
Student Record Software
·
Inventory Management
Software
·
Income Tax Software
·
Railways Reservation
Software
·
Microsoft Office Suite
Software
·
Microsoft Word
·
Microsoft Excel
·
Microsoft Powerpoint
Features of application software are as follows:
·
Close to user
·
Easy to design
·
More interactive
·
Slow in speed
·
Generally written in
high-level language
·
Easy to understand
·
Easy to manipulate and
use
·
Bigger in size and
requires large storage space
Number System
When we type some letters or words, the computer
translates them in numbers as computers can understand only numbers. A computer
can understand positional number system where there are only a few symbols
called digits and these symbols represent different values depending on the
position they occupy in the number.
A value of each digit in a number can be determined
using
·
The digit
·
The position of the
digit in the number
·
The base of the number
system (where base is defined as the total number of digits available in the
number system).
Decimal Number System
The number system that we use in our day-to-day life
is the decimal number system. Decimal number system has base 10 as it uses 10
digits from 0 to 9. In decimal number system, the successive positions to the
left of the decimal point represent units, tens, hundreds, thousands and so on.
Each position represents a specific power of the base
(10). For example, the decimal number 1234 consists of the digit 4 in the units
position, 3 in the tens position, 2 in the hundreds position, and 1 in the
thousands position, and its value can be written as
(1x1000)+ (2x100)+ (3x10)+ (4xl)
(1x103)+ (2x102)+ (3x101)+ (4xl00)
1000 + 200 + 30 + 4
1234
As a computer programmer or an IT professional, you
should understand the following number systems which are frequently used in
computers.
S.N.
|
Number System and Description
|
1
|
Binary Number System
Base 2. Digits used : 0, 1
|
2
|
Octal Number System
Base 8. Digits used : 0 to 7
|
3
|
Hexa Decimal Number System
Base 16. Digits used : 0 to 9, Letters used : A- F
|
Binary Number System
Characteristics
of binary number system are as follows:
·
Uses two digits, 0 and
1.
·
Also called base 2
number system
·
Each position in a
binary number represents a 0 power of the base (2). Example 20
·
Last position in a
binary number represents a x power of the base (2). Example 2x where
x represents the last position - 1.
Example
Binary Number : 101012
Calculating Decimal Equivalent:
Step
|
Binary Number
|
Decimal Number
|
Step 1
|
101012
|
((1 x 24) + (0 x 23) + (1 x 22)
+ (0 x 21) + (1 x 20))10
|
Step 2
|
101012
|
(16 + 0 + 4 + 0 + 1)10
|
Step 3
|
101012
|
2110
|
Note : 101012 is
normally written as 10101.
Octal Number System
Characteristics
of octal number system are as follows:
·
Uses eight digits,
0,1,2,3,4,5,6,7.
·
Also called base 8
number system
·
Each position in an
octal number represents a 0 power of the base (8). Example 80
·
Last position in an
octal number represents a x power of the base (8). Example 8x where
x represents the last position - 1.
Example
Octal Number : 125708
Calculating Decimal Equivalent:
Step
|
Octal Number
|
Decimal Number
|
Step 1
|
125708
|
((1 x 84) + (2 x 83) + (5 x 82)
+ (7 x 81) + (0 x 80))10
|
Step 2
|
125708
|
(4096 + 1024 + 320 + 56 + 0)10
|
Step 3
|
125708
|
549610
|
Note : 125708 is
normally written as 12570.
Hexadecimal Number System
Characteristics
of hexadecimal number system are as follows:
·
Uses 10 digits and 6
letters, 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F.
·
Letters represents
numbers starting from 10. A = 10. B = 11, C = 12, D = 13, E = 14, F = 15.
·
Also called base 16
number system
·
Each position in a
hexadecimal number represents a 0 power of the base (16). Example 160
·
Last position in a
hexadecimal number represents a x power of the base (16). Example 16x
where x represents the last position - 1.
Example
Hexadecimal Number : 19FDE16
Calculating Decimal Equivalent:
Step
|
Binary Number
|
Decimal Number
|
Step 1
|
19FDE16
|
((1 x 164) + (9 x 163) + (F x
162) + (D x 161) + (E x 160))10
|
Step 2
|
19FDE16
|
((1 x 164) + (9 x 163) + (15 x
162) + (13 x 161) + (14 x 160))10
|
Step 3
|
19FDE16
|
(65536+ 36864 + 3840 + 208 + 14)10
|
Step 4
|
19FDE16
|
10646210
|
Note : 19FDE16 is
normally written as 19FDE.
Number Conversion
There are many methods or techniques which can be used
to convert numbers from one base to another. We'll demonstrate here the
following:
·
Decimal to Other Base
System
·
Other Base System to
Decimal
·
Other Base System to
Non-Decimal
·
Shortcut method - Binary
to Octal
·
Shortcut method - Octal
to Binary
·
Shortcut method - Binary
to Hexadecimal
·
Shortcut method -
Hexadecimal to Binary
Decimal to Other Base System
steps
·
Step 1 - Divide the decimal number to be converted by the value
of the new base.
·
Step 2 - Get the remainder from Step 1 as the rightmost digit
(least significant digit) of new base number.
·
Step 3 - Divide the quotient of the previous divide by the new
base.
·
Step 4 - Record the remainder from Step 3 as the next digit (to
the left) of the new base number.
Repeat Steps 3 and 4, getting remainders from right to
left, until the quotient becomes zero in Step 3.
The last remainder thus obtained will be the most
significant digit (MSD) of the new base number.
Example
Decimal Number : 2910
Calculating Binary Equivalent:
Step
|
Operation
|
Result
|
Remainder
|
Step 1
|
29 / 2
|
14
|
1
|
Step 2
|
14 / 2
|
7
|
0
|
Step 3
|
7 / 2
|
3
|
1
|
Step 4
|
3 / 2
|
1
|
1
|
Step 5
|
1 / 2
|
0
|
1
|
As mentioned in Steps 2 and 4, the remainders have to
be arranged in the reverse order so that the first remainder becomes the least
significant digit (LSD) and the last remainder becomes the most significant
digit (MSD).
Decimal Number : 2910 = Binary Number :
111012.
Other base system to Decimal System
Steps
·
Step 1 - Determine the column (positional) value of each digit
(this depends on the position of the digit and the base of the number system).
·
Step 2 - Multiply the obtained column values (in Step 1) by the
digits in the corresponding columns.
·
Step 3 - Sum the products calculated in Step 2. The total is
the equivalent value in decimal.
Example
Binary Number : 111012
Calculating Decimal Equivalent:
Step
|
Binary Number
|
Decimal Number
|
Step 1
|
111012
|
((1 x 24) + (1 x 23) + (1 x 22)
+ (0 x 21) + (1 x 20))10
|
Step 2
|
111012
|
(16 + 8 + 4 + 0 + 1)10
|
Step 3
|
111012
|
2910
|
Binary Number : 111012 = Decimal Number :
2910
Other Base System to Non-Decimal System
Steps
·
Step 1 - Convert the original number to a decimal number (base
10).
·
Step 2 - Convert the decimal number so obtained to the new base
number.
Example
Octal Number : 258
Calculating Binary Equivalent:
Step
1 : Convert to Decimal
Step
|
Octal Number
|
Decimal Number
|
Step 1
|
258
|
((2 x 81) + (5 x 80))10
|
Step 2
|
258
|
(16 + 5 )10
|
Step 3
|
258
|
2110
|
Octal Number : 258 = Decimal Number : 2110
Step
2 : Convert Decimal to Binary
Step
|
Operation
|
Result
|
Remainder
|
Step 1
|
21 / 2
|
10
|
1
|
Step 2
|
10 / 2
|
5
|
0
|
Step 3
|
5 / 2
|
2
|
1
|
Step 4
|
2 / 2
|
1
|
0
|
Step 5
|
1 / 2
|
0
|
1
|
Decimal Number : 2110 = Binary Number :
101012
Octal Number : 258 = Binary Number : 101012
Shortcut method - Binary to Octal
Steps
·
Step 1 - Divide the binary digits into groups of three
(starting from the right).
·
Step 2 - Convert each group of three binary digits to one octal
digit.
Example
Binary Number : 101012
Calculating Octal Equivalent:
Step
|
Binary Number
|
Octal Number
|
Step 1
|
101012
|
010 101
|
Step 2
|
101012
|
28 58
|
Step 3
|
101012
|
258
|
Binary Number : 101012 = Octal Number : 258
Shortcut method - Octal to Binary
Steps
·
Step 1 - Convert each octal digit to a 3 digit binary number
(the octal digits may be treated as decimal for this conversion).
·
Step 2 - Combine all the resulting binary groups (of 3 digits
each) into a single binary number.
Example
Octal Number : 258
Calculating Binary Equivalent:
Step
|
Octal Number
|
Binary Number
|
Step 1
|
258
|
210 510
|
Step 2
|
258
|
0102 1012
|
Step 3
|
258
|
0101012
|
Octal Number : 258 = Binary Number : 101012
Shortcut method - Binary to Hexadecimal
Steps
·
Step 1 - Divide the binary digits into groups of four (starting
from the right).
·
Step 2 - Convert each group of four binary digits to one
hexadecimal symbol.
Example
Binary Number : 101012
Calculating hexadecimal Equivalent:
Step
|
Binary Number
|
Hexadecimal Number
|
Step 1
|
101012
|
0001 0101
|
Step 2
|
101012
|
110 510
|
Step 3
|
101012
|
1516
|
Binary Number : 101012 = Hexadecimal Number
: 1516
Shortcut method - Hexadecimal to Binary
steps
·
Step 1 - Convert each hexadecimal digit to a 4 digit binary
number (the hexadecimal digits may be treated as decimal for this conversion).
·
Step 2 - Combine all the resulting binary groups (of 4 digits
each) into a single binary number.
Example
Hexadecimal Number : 1516
Calculating Binary Equivalent:
Step
|
Hexadecimal Number
|
Binary Number
|
Step 1
|
1516
|
110 510
|
Step 2
|
1516
|
00012 01012
|
Step 3
|
1516
|
000101012
|
Hexadecimal Number : 1516 = Binary Number :
101012
Data and Information
What is data?
Data can be defined as a representation of facts,
concepts or instructions in a formalized manner which should be suitable for
communication, interpretation, or processing by human or electronic machine.
Data is represented with the help of characters like
alphabets (A-Z,a-z), digits (0-9) or special characters(+,-,/,*,<,>,=
etc.).
What is Information?
Information is organised or classified data which has
some meaningful values for the receiver.
Information is the processed data on which decisions
and actions are based.
For the decision to be meaningful, the processed data
must qualify for the following characteristics:
·
Timely - Information should be available when required.
·
Accuracy - Information should be accurate.
·
Completeness - Information should be complete.
Data Processing Cycle
Data processing is the re-structuring or re-ordering
of data by people or machine to increase their usefulness and add values for
particular purpose. Data processing consists of basic steps input, processing
and output. These three steps constitute the data processing cycle.
·
Input - In this step the input data is prepared in some
convenient form for processing. The form will depend on the processing machine.
For example, when electronic computers are used, the input data could be
recorded on any one of several types of input medium, such as magnetic disks,
tapes and so on.
·
Processing - In this step input data is changed to produce data in
a more useful form. For example, pay-checks may be calculated from the time
cards, or a summary of sales for the month may be calculated from the sales
orders.
·
Output - Here the result of the proceeding processing step are
collected. The particular form of the output data depends on the use of the
data. For example, output data may be pay-checks for employees.
Networking
What is a Computer Network?
A computer network is a system in which multiple
computers are connected to each other to share information and resources.
Characteristics of a computer network
·
Share Resources from one
computer to another
·
Create files and store them
in one computer, access those files from the other computer(s) connected over
the network
·
Connect a printer,
scanner, or a fax machine to one computer within the network and let other
computers of the network use the machines available over network.
Following is the list of hardware's required to setup
a computer network.
·
Network Cables
·
Distributors
·
Routers
·
Internal Network Cards
·
External Network Cards
Network
Cables
Network cables are used to connect computers. The most
commonly used cable is Category 5 cable RJ-45.
Distributors
A computer can be connected to another one via a
serial port but if we need to connect many computers to produce a network, this
serial connection will not work. The solution is to use a central body to which
other computers, printers, scanners etc. can be connected and then this body
will manage or distribute network traffic.
Router
A router is a type of device which acts as the central
point among computers and other devices that are part of a network. A router is
equipped with holes called ports and computers and other devices are connected
to a router using network cables. Now-a-days router comes in wireless modes
using which computers can be connected without any physical cable.
Network
Card
Network card is a necessary component of a computer
without which a computer cannot be connected over a network. It is also known
as network adapter or Network Interface Card (NIC). Most branded computers have
network card pre-installed. Network cards are of two types : Internal and
External Network Cards.
Internal Network Cards
Motherboard has a slot for internal network card where
it is to be inserted. Internal network cards are of two types in which first
type uses Peripheral Component Interconnect (PCI) connection while the second
type uses Industry Standard Architecture (ISA). Network cables are required to
provide network access.
External Network Cards
External network cards come in two flavours : Wireless
and USB based. Wireless network card need to be inserted into the motherboard
but no network cable is required to connect to network
Universal Serial Bus (USB)
USB card are easy to use and connect via USB port.
Computers automatically detect USB card and can install the drivers required to
support the USB network card automatically.
Operating System
It is a program with following features:
·
An operating system is a
program that acts as an interface between the software and the computer
hardware.
·
It is an integrated set
of specialised programs that are used to manage overall resources and
operations of the computer.
·
It is specialised
software that controls and monitors the execution of all other programs that
reside in the computer, including application programs and other system
software.
Objectives of Operating System
·
To make a computer
system convenient to use in an efficient manner
·
To hide the details of
the hardware resources from the users
·
To provide users a
convenient interface to use the computer system
·
To act as an
intermediary between the hardware and its users and making it easier for the
users to access and use other resources
·
To manage the resources
of a computer system
·
To keep track of who is
using which resource, granting resource requests, according for resource using
and mediating conflicting requests from different programs and users
·
To provide efficient and
fair sharing of resources among users and programs
Characteristics of Operating System
·
Memory Management -- keeps tracks of primary memory i.e. what part of it is
in use by whom, what part is not in use etc. and allocates the memory when a
process or program requests it.
·
Processor Management -- allocates the processor(CPU) to a process and
deallocates processor when it is no longer required.
·
Device Management -- keeps track of all devices. This is also called I/O
controller that decides which process gets the device, when, and for how much
time.
·
File Management -- allocates and de-allocates the resources and decides
who gets the resources.
·
Security -- prevents unauthorized access to programs and data by
means of passwords and similar other techniques.
·
Job accounting -- keeps track of time and resources used by various jobs
and/or users.
·
Control over system
performance -- records delays between
request for a service and from the system.
·
Interaction with the
operators -- The interaction may take place via the
console of the computer in the form of instructions. Operating System
acknowledges the same, does the corresponding action and informs the operation
by a display screen.
·
Error-detecting aids -- Production of dumps, traces, error messages and other
debugging and error-detecting methods.
·
Coordination between
other software and users -- Coordination and
assignment of compilers, interpreters, assemblers and other software to the
various users of the computer systems.
Internet and Intranet
Internet
It is a worldwide system which has the following
characteristics:
·
Internet is a world-wide
/ global system of interconnected computer networks.
·
Internet uses the
standard Internet Protocol (TCP/IP)
·
Every computer in
internet is identified by a unique IP address.
·
IP Address is a unique
set of numbers (such as 110.22.33.114) which identifies a computer’s location.
·
A special computer DNS
(Domain Name Server) is used to give name to the IP Address so that user can
locate a computer by a name.
·
For example, a DNS
server will resolve a name http://www.tutorialspoint.com to a particular
IP address to uniquely identify the computer on which this website is hosted.
·
Internet is accessible
to every user all over the world.
Intranet
·
Intranet is system in
which multiple PCs are connected to each other.
·
PCs in intranet are not
available to the world outside the intranet.
·
Usually each company or
organization has their own Intranet network and members/employees of that
company can access the computers in their intranet.
·
Each computer in
Intranet is also identified by an IP Address which is unique among the
computers in that Intranet.
Similarities in Internet and Intranet
·
Intranet uses the
internet protocols such as TCP/IP and FTP.
·
Intranet sites are
accessible via web browser in similar way as websites in internet. But only
members of Intranet network can access intranet hosted sites.
·
In Intranet, own instant
messengers can be used as similar to yahoo messenger/ gtalk over the internet.
Differences in Internet and Intranet
·
Internet is general to
PCs all over the world whereas Intranet is specific to few PCs.
·
Internet has wider
access and provides a better access to websites to large population whereas
Intranet is restricted.
·
Internet is not as safe
as Intranet as Intranet can be safely privatized as per the need.
How to Buy?
This chapter gives the following information:
·
In this guide, we'll
help you to buy a desktop on component by component basis.
·
As desktops are highly
customizable, so it is better to learn about main parts and then go to
manufacturer or retailer shop or site instead of looking at some specific model
directly.
·
Popular desktop brands
are Dell, Lenovo, HP and Apple.
·
Compare the desktops
based on their specifications and base price.
Monitor
·
Size - It is the diagonal size of the LCD screen. Larger the
area, bigger the picture screen. A bigger picture is preferable for movie
watching and gaming. It will increase productivity as well.
·
Resolution - This is the number of pixels on the screen. For
example, 24-inch display is 1920x1200 (width by length) and 22-inch display
which is 1680x1050. High resolution provides better picture quality and a nice
gaming experience.
·
Inputs - Now-a-days monitors can accept inputs from cable as
well apart from computer. They also can have USB ports.
·
Stand - Some monitors come with adjustable stands while some
may not.
·
Recommended - 24 Inch LCD.
Operating System
·
Operating System is the
main software of the computer as everything will run on it in one form or
other.
·
There are primarily
three choices : Windows, Linux, Apple OS X.
·
Linux is free but people generally do not use it for home
purpose.
·
Apple OS X works only on Apple Desktops.
·
Windows 7 is very popular among desktop users.
·
Most of the computers
come pre-equipped with Windows 7 Starter edition.
·
Windows 8 is recently introduced and is available in market.
·
Windows 7 and Windows 8 come in multiple versions from starter, home basic,
home premium, professional, ultimate and enterprise editions.
·
As edition version
increases, their features list and price increases.
·
Recommended - Windows 7 Home Premium.
Optical Drive (CD / DVD / Blu-ray)
·
Optical drive is the
drive on a computer which is responsible for using CD, DVD and Blu-ray discs.
·
Now-a-days, DVD burners
are industry standards.
·
DVD Burner can burn CD,
DVD and play them.
·
DVD Burner is cheaper
than Blu-ray drives.
·
Blu-ray drives can play
HD movies but are costlier component.
·
Recommended - DVD Burner.
Memory
·
RAM is considered as
Computer Memory as performance of a computer is directly proportional to its
memory and processor.
·
Today's software and
operating system require high memory.
·
Today commonly used RAM
is DDR3 which operates at 1066Mhz
·
As per Windows 7, 1 GB
is the minimum RAM required to function properly.
·
Recommended - 4 GB.
Hard Drive
·
Hard disk is used for
storage purpose. Higher the capacity, more data you can save in it.
·
Now-a-days computers are
equipped with 500GB hard drive which can be extended to 2TB.
·
Most hard drives in
desktop operate at the standard performance speed of 7200RPM.
·
Recommended - 500GB.
CPU
·
Frequency (GHz) - This determines speed of the processor. More the
speed, better the CPU.
·
Cores - Now-a-days CPUs come with more than one core, which is
like having more than one CPU in the computer. Programs which can take
advantage of multi-core environment will run faster on such machines.
·
Brand - Intel or AMD. Both are equivalent. Intel is in lead.
·
Cache - Higher the L1, L2 cache, better the CPU performance
·
Recommended - Intel Core i3 i3-3225 3.30 GHz Processor.