it tools and applications

8/9/2019 IT Tools and Applications

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CONTENTS

Topics Page No.

1. Definition of Computer 1

2. History and Evolution Of Computer 2

3. Application Of Computer 4

4. Anatomy of Computer 6

5. Input - Output Devices 8

6. Memory 21

7. Computer Software & Hardware 27

8. Number System and Representation 29

9. Language And Software 37

10.Disk Operating System 42

11.Windows 75

12.Linux 87

13.Microsoft Word 164

14.Microsoft Excel 165

15.Microsoft Power Point 189

16.Internet Application 229


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IT TOOLS AND APPLICATIONS APPRECIATION

TECHNO INDIA GROUP By Parijat Chakraborty Page 1

COMPUTER APPRECIATION

Definition of Computer

Computer is a device that accepts information and manipulates it for some resultbased on a program or sequence of instructions on how data is to be processed. The word computer comes from the word compute, which means to calculate.

Hence, a computer is normally considered to be a calculating device, which can performarithmetic operation at enormous speed.

More accurately, a computer may be defined as a device, which operates upon data. Datacan be any thing like marks obtained by various students in various subjects when thecomputer is used to prepare various results.

The activity of processing data using a computer is called data processing. Dataprocessing consists of three sub activities: capturing the input data, manipulating the dataand managing the output results. As used in data processing, information is data arranged

in an order and form, which is useful to people who receive it. Hence, data processingand information is the processed data obtained as the output of data processing.

CHARACTERISTIC OF COMPUTER:

AUTOMATIC: - Amachine is said to be automatic, if it works by itself withouthuman intervention. Computer is machines because once started on a job, theycarry on, until the job is finished, normally without any human assistance.

SPEED: - A computer is very fast device. It can perform in a few seconds, theamount of work that human begin can do in an entire year-if he worked day andnight and did nothing else.

ACCURACY: - In addition to being very fast, computers are very accurate. Theaccuracy of a particular computer depends upon its design.

DILIGENCE: - Unlike human beings, a computer is free from monotony,tiredness and lack of concentration. It can continuously work for hours, withoutcreating any error and without grumbling.

VERSATILITY: - Versatility is one of the most wonderful things about thecomputer. One moment, it is preparing the results of an examination, the nextmoment, it is busy preparing electricity bills, and in between, it may be helping anoffice secretary to trace an important letter in seconds.

POWER OF REMEMBERING: - As a human being acquires new knowledge,the brain subconsciously select what it feels to be important and worth retaining

in its memory, and relegates unimportant details to the back of the mind or justforgets them.

NO I.Q. :- A computer is not a magical device. It possesses no intelligence of itsown. Its I.Q. is zero.

NO FEELINGS: - Computers are devoid of emotions. They have no feelings andno instincts because they are machines.

A


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HISTORY OF COMPUTER

The history of computers will not only give the basic information about thetechnological development trends in computer in the past but also its projections in thefuture. The knowledge of history are essential to give us the feel of how much work and

efforts has been done to get the computer in this present shape.Use of tools for calculation is very old. The first use of instrument for calculation wasmade by Chinese nearly 5 thousands years ago. The name of instrument is "abacus". It ismade with a wooden or metal frame on which there are several rows of strings.The ancestors of modern age computer were the mechanical and electro-mechanicaldevices. This ancestry can be traced back in 17th century, when first machine capable ofperforming four mathematical operations addition, subtraction, division andmultiplication. The very first attempt towards this computing was made by Blaise Pascalin 1642 which consisted of lots of gears and chains and used to perform repeated additionand subtractions. The device was called pascaline. Prof. Charles Babbage- thegrandfather of modern computer. In 1833 Babbage began work on an Analytical Engine"

which perform any mathematical operation automatically. Most of today's computerdesigns are based on concepts developed by John von Neumann known as von Neumannarchitecture.

THE EVOLUTION OF COMPUTERS

First Generation: In 1945 ENIAC first designed a general-purpose computer. The ENIAC ushered in the era of what isknown as First Generation Computer. Here the vacuum tubes areused in electronic circuit. For storage magnetic drums are used.Input/output was slow due to use of punched card and tape. Due to

use of vacuum tube, the size of the machine is great and a greatamount of electricity and emitted excessive heat.


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Second Generation: - The second-generation computers startedwith the advent of transistor. Here in the electronic circuittransistor and diodes are used. In the primary internal storagemagnetic core are used. Thus increasing the main storage capacity.Input/output was faster. It is cheaper, smaller and heat generation

is less. The second-generation computers were more advanced interms of arithmetic and logic unit and control unit than firstgeneration computers. It was used for billing, payroll processingand updating inventory files. IBM 1601, Honeywell 400,CDC1604, IBM 1602 are some of the second-generation computers.

Third Generation The use of Integrated circuit(IC) in thecomputer defines the third generation computers. Because due touse of densely packed Ics, the cost is low, greater operating speed,there is a reduction in power and cooling requirement. Thesecomputers not only small but their performance and reliability are

also great. This computers are used in airline system, marketforecasting, credit-card billing.IBM system/360,370,NCR 395,ICL 1900.

Fourth Generation With the growth of micro-electronics, the ICtechnology evolved rapidly producing very large scale integration(VLSI) where thousands of transistors can be integrated on asingle chip. The VLSI-based computer architecture is referred toas fourth generation computers. Here the storage capacity andspeed are also increased. The use of microprocessor and microcomputer started in this generation. Many sophisticatedapplication program and networking facilities can be done through

these computers.CATEGORY OF COMPUTER

The digital computers are of the following four main classes.1. Micro computer2. Mini computer3. Mainframe computer4. Super computer

Micro Computer: A micro-computer's CPU is a microprocessor. The microcomputeroriginated in late 1970s. The first micro computers were built around 8-bit

microprocessor chips i.e. the chip can retrieve instructions/data from storage manipulateand process an 8 bit data a time or we can say that the chip has a built in 8-bit datatransfer path. In 1980 8 bit chip is replaced by 16 bit namely 8086 and 8088 produced byIntel Corporation. Personal computer is the types of microcomputer based on theirprocessor. These computers used in school, colleges, and offices and even in home are ofthis type. PCs are generally named as Desktop, Laptop, Home computer. In 1981 firstintroduce the personal computer. There are two types of personal computer based on theuse of processor.


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1. PC/XT (Personal Computer/Extended Technology): This type of micro computerworks with the 8088 processor.2. PC/XT (Personal Computer/Advanced Technology): This type of PC works withthe following processor.i) 80286 ii) 80386 iii) 80486 iv) Pentium Pro v) Pentium II vi) Pentium III vi)

Pentium IV.

Mini Computer: The term mini computer originated in 1960s when it was realized thatmany computing tasks do not require an expensive contemporary mainframe computerbut can be solved by a small, inexpensive computer.Later, microcomputer is replaced by 32-bit mini computer, which is also called supermini computer, which had more peripheral devices, large memory and could supportmore users working simultaneously on the computer.

Mainframe Computer: Mainframe computers are generally 32-bit machines or on thehigher side. These are suited to big organizations, to manage high volume applications.

80 terminals can be connected with mainframe computers; so 80 persons can work at atime. Popular mainframe series are MEDHA, SPERRY, DEC, ICL. Mainframe computerare used in libraries for their large scale work.

Super Computer: The upper end of the state of the art mainframe machine is the supercomputer. These are the fastest machines in terms of processing speed and usemultiprocessing techniques. Here a number of processors are used to solve a problem.Here 200 terminals can be connected and so 200 persons can work at a time.

A number of companies dominate in the field of super computers; these are CRAY-2,ETA-20 and IBM 3090 and HITACHI. The super computers are reaching up to speedswell over 25000 million arithmetic operations per second. India has also in the line ofpreparing super computer. Super computer are mainly used for weather forecasting,computational fluid dynamics, remote sensing, image processing, bio-medicalapplications. India has a mainframe super computer system CRAY XMP-14 which is atpresent being used by meteorological department.

APPLICATION OF COMPUTER

There are lots of uses of computers. In fact, in our everyday life it is used in almost everystep. Some of the places where it is used is listed below:

Airlines: Booking now you can book your ticket for a flight leaving. New York whilesitting in Melbourne. All the airlines are interconnected through computers.

Banks: Computers in Banks have made it possible that you can get your accountinformation while sitting at home only. For this your bank must be an e-bank, which mostof them are. ATM is another computer application of bank.


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Business: For most of the companies, all the work relating to accounts is now doneon computers, for accuracy and speed ness. You can even have your correspondence onit.

Cartoons: There are various programs available in computers which allow you to

create animations. By learning about them you can become an expert animator. You mayeven make a movie of your own.

Cinema: Now a days computers do most of the film editing. You can add and deletefilm clips at a snap using computer. In fact, some movies are totally made usingcomputers. Films like Toy Story are made using computers.

Defense: America has used the computers in defense for the fullest with pin pointingthe position of enemy targets. Most of the missiles these days are computer controlled.

DTP: It has revolutionized how composing for printing used to done. Now every

book for printing is composed on computer since it is very easy to edit and read onscreen.

Education: Computers can help in teaching too. In fact this books on computers wascreated using computers. Most of the schools now use computers for accounting, studentsrecord management, papers preparations and even results compilation.

Home: At home it has become an additional entertainment media. You can use it forplaying games, watching movies, listening to songs, writing letters, creating your owndatabase of friends.

Library Maintaining: the records in library manually used to be very cumbersomemethod. Computers have dramatically changed the way the cataloging is done inlibraries.

Medicine: Lots of research in medicine is done using computers. Doctors now a dayscan see the complete inside of the human beings using the computer.

Space Technology: All the movements of the satellite are controlled using thecomputer.

Weather: Using computers and satellites you can predict the weather for the next fewdays. In fact, the biggest computer in India is with the Meteorological Department ofIndia, at New Delhi.


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ANATOMY OF COMPUTER

Computer consists of three (3) main parts. They are:

Input Unit Output Unit Central Processing Unit

Input unit - Data and instruction are entered into computer with the help of a unit, calledInput unit. Input unit turns data and instructions into binary form (either 0 or 1) to makethem comprehensible to computers. Generally, as a primary input device, keyboard isused.

In short, the following functions are performed by an Input unit:

1. It accepts (or reads) the instructions and data from the outside worlds.2. It converts these instructions and data in computer acceptable form.

3. It supplies the converted instructions and data to the computer system for furtherprocessing.

Output Unit The job of an output unit is just the reverse of that of an input unit. Itsupplies the information obtained from data processing to the outside world. Monitor,also known as Visual Display Unit (VDU) is primarily used as an output unit.


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In short, the following functions are performed by an Output unit:

1. It accepts the results produced by the computer, which are the coded form,and hence, cannot be easily understood by us.

2. It converts these coded results to human acceptable (readable) form.

3. It supplies the converted results to the outside world.

Central Processing Unit - Central processing unit (CPU) is referred to as the brain ofcomputer. In a human body, all major decisions are taken by the brain, and the otherparts of the body functions as directed by the brain. Similarly, in a computer system, allmajor calculation and comparisons are made inside the CPU and the CPU is responsiblefor activating and controlling the operation of other units of the computer system. Itmainly executes the data and instruction provided by the users.

It consists of three (3) main units:

Arithmetic and logic unit (ALU) Storage unit ( Main memory Unit / Primary Storage)

Control Unit (CU)

Arithmetic Logic Unit: The arithmetic logic unit (ALU) of a computer system is theplace, where the actual execution of the instruction takes place, during the processingoperation. To be more precise, calculations are performed, and all comparisons are madein the ALU. The arithmetic operations like +, - , * and / are performed here. The logicaloperations like , =. = and are also performed here. In most of the arithmetic


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operations the result is in numerical form while in the case of logical operations the resultcan be YES / NO or TRUE / FALSE.

Control Unit: This unit controls the flow and manipulation of data and information.It also controls the flow of data from input devices to memory and from memory to

output devices.

Storage Unit: The data and instructions, which are entered into the computer systemthrough input units, have to be stored inside the computer, before the actual processingstarts. Similarly, the result produced by the computer after processing, must also be keptsomewhere inside the computer system, before being passed on to the output units. Moreover, the intermediate results produced by the computer, must also be preserved forongoing processing. The storage unit of a computer system is designed for all thesepurpose.

In short, the specific functions of the storage unit are to store :

1. The data and instructions required for processing (received from input devices)2. Intermediate results of processing.3. Final results of processing, before these results are released to an output device

The storage unit of all computers is comprised of the following two (2) types of storage:

1.Primary storage: The primary storage, also known as main memory. It is alsocalled primary memory and it is Memory is one of the most wonderful features oncomputer. It is one of the most important parts of this system. Details discuss later.

2.Secondary storage: The secondary storage, also known as auxiliary storage, isused to take care of limitation of the primary storage. It is used to supplement the limitedstorage capacity and the volatile characteristic of primary storage. Details discuss later.

INPUT - OUTPUT DEVICESA computer system can be useful, only when it is able to communicate with its externalenvironment. In the following figure, the input-output devices (abbreviated I/O devices)provide the means of communication between the computer and outside world. They arealso known as peripheral devices. Input devices are used to enter data from the outsideworld into primary storage. Input devices are used to enter data from the outside worldinto primary storage and output devices supply the results of processing from the primary

storage to the users. A wide variety of I/O devices are now available.

Figure : Illustrating the role of I/O devices in a computer system

Inputdata fromexternalworld

Inputdata fromexternal

world

Input

Devices

CPU

And

Memory

Output

DevicesInput datacoded ininternal form

Processed datain internalform


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INPUT DEVICES

A device that converts our information to a form which computer understands is

known as Input Device. An input device is an electromechanical device, which acceptsdata from the outside world, and translates them into a form, which the computer can

interrupt. A keyboard terminal is the most common input device. Several input devicesare available today. They can be broadly classified into the following categories.

1. Keyboard devices 4. Electronic cards based devices2. Point- and draw devices 5. Voice recognition devices3. Data scanning devices 6. Vision based devices

The various types of input devices along with their typical applications are

described below.

1. Keyboard Devices: Keyboard is the most commonly used input devices today.This is the only input device, which works using characters or symbols. Keyboards arereferred to as Character User Interface (CUI).

Its structure is similar to that of a typewriter and works also almost in the same way. Butit has certain advantages over the type writer, such as:

(a) It has function keys (F! to F12) which is programmable(b)Almost all the keys are dual function keys.


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WE can also classify the keys of keyboard in four types as The alphanumeric keys The numeric keypad The function keys

Special Purpose keys

The Alphanumeric keys

The alphanumeric keys are centrally located in a keyboard quite like you see in atraditional manual typewriter. The alphanumeric keys include alphabet ( A Z or a z ) ,numeric characters (0 9), special symbols (~!@#$%^&*()_+|\)). The special symbolscan be used by holding Shift and numeric keys.

The Numeric Keypad

The numeric keypad includes a set of 17 keys containing 0-9 digits, mathematicaloperators, arrow keys and some special keys (Home, Pg Up, Pg Dn, End, Ins, Enter and

Del).

The Function Keys:On the upper side of the there are 12 Function keys denoted by F1, F2 F12. These keyslet you use commands in a short cut manner.

Special purpose keys:

With the advent of advanced software, keyboards have been equipped with special keyswhich work accordingly to new programs in operating system. These are

The most popular keyboard used today is the 101- keys QWERTY keyboard.

2. Point- and Draw Devices : These input devices have made computers a muchmore easily usable tool, and have established the computer as a versatile tool for graphicdesigners. It was realized that many of these devices, like mouse and light pen, could alsobe very effectively used to create graphic elements on the screen such as lines, curves,and freehand shapes. With this new ability, these devices came to be known as point-and-draw devices. Some of the most commonly used point-and-draw devices are describedbelow:

a) Mouse: Mouse is the most popular point-and-draw device. It is an online inputdevice which can be used by single hand. By moving a mouse on a plane surface, a ball

inside the mouse rolls which in turn moves the rollers in-built in the mouse. The graphicscursor, which is used to point and draw, is displayed on the screen as variety of symbols,such as arrow ( ) , a wrist with a pointing finger ( ) etc.Mouse has two or more buttons. Left hand side button is most in use while right handside button is used in special cases. By the way, you can change it with the help of theoptions available in the operating system software. ON pressing the button of mouse wecan select the icons on the screen. The pressing of button of mouse by finger is calledclicking.


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There are three (3) types of mouse:-

Mechanical Mouse Optical Mouse Cordless Mouse

Mechanical Mouse: Most of the mice we see today are mechanical mouse. This typeof mouse, commonly used on personal computer, has a small rubber ball inside the caseand can roll in all direction.

Optical Mouse: Optical mouse is a new type of non-mechanical mouse. It is quickerbut more expensive than the mechanical one. It emits a beam of light from its underside.It detects the distance, direction and speed of mouse with its reflection.

Cordless Mouse: Cordless mouse being the most advanced technology, relieves you

from botheration of wires. It uses radio frequency to communicate information to yourcomputer.


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Figure : Types of Mouse

b) TRACK BALL :A trackball is a pointing device that works like a mouse. It has an exposed ball on its

upper surface and buttons. While operating in, your thumb is positioned on its ball andother fingers are on its different buttons. Unlike mouse, trackball is fixed and hence itoccupies less space. Track ball became popular with the of Laptop computers as you canuse laptop anywhere as per your choice and needs.Track ball is available in several models. It is available in both big and small balls.Models with two buttons and three buttons for left handed and right handed users are alsoavailable.

c) JOYSTICKJoystick is a pointing device, which works on the same principle as a track ball. It is

generally used for playing video games. It has a handle which can help us in navigatingthe turtle or graphics on the screen. This generally is used to play games by children andhence is a good medium to create interest of children in computers. Although all thecomputer games can also be played by keyboard but a joystick provides speed andconvenience in these games.

d) ELECTRONIC PENAnother point-and-draw device is an electronic pen. In a pen based system, you hold the

pen in your hand and directly point with it on the screen to select menu items or icons;directly draw graphics on the screen with it ; or write with it on a special pad for directinput of the written information to the system.

e) TOUCH SCREENTouch screen is the most simple and easiest to learn of all input devices. A touch screenenables the users to choose from available options by simply touching with their fingerthe desired icon or menu item displayed on the computer screen.


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Touch screen are the most preferred human-computer interface devices used ininformation kiosks. An information kiosk is an unattended system. For example,information kiosks may be located

1. At an airport or a railway station to provide information to arriving passengersabout hotels, tourists spot etc in the city.

2. In large museums or zoos to guide the visitors to the location of variousattraction and facilities.

3. DATA SCANNING DEVICESData scanning devices are input devices, which are used for direct data entry into thecomputer system from source documents. Some of the data scanning devices are alsocapable of recognizing marks of characters

Data scanning devices are of many types. These are: Image Scanner Optical Mark Reader ( OMR) Optical Character Recognition Device / Optical Character Reader (OCR) Bar Code Reader Magnetic Ink Character Reader

IMAGE SCANNERAn image scanner is an input device, which translates paperdocuments into an electronic format, which can be stored ina computer. The input documents may be typed text,

pictures, graphics or even handwritten materials. They arecapable of entering information directly into the computer.The main advantage of direct entry of information is thatusers do not have to key in the information. This providesfaster and more accurate data entry. This input device has

been found to be very useful in preserving paper documents in electronic form.

Image scanners come in various shaped and sizes. The two commonly used types are

Fi ure : Touch Screen


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1) Flatbed scanner2) Hand-held scanner

Optical Mark Reader (OMR )

It is popularly used for evaluating objective-answer scripts in examinations. In theanswer-scripts, the answer is marked by filling up circular, square or oval areas withpencil marks. While evaluating the scripts with an OMR, light is made incident on thescript, some of which is reflected off by the highly reflective pencil marks and is pickedup by a sensor. Then the computer cross matches the co-ordinates of the answer given byan examinee with the correct ones.

Optical Character Reader (OCR )

It is special types of scanner which is popularly used for scanning alphabetic, numericand alpha-numeric symbols written using normal ink on plain paper. It may be hand heldscanner or a page scanner to detect light reflected from a line or from a page of the text.The change in the reflected light is converted to binary data which is sent to theprocessor. The light is absorbed by the dark areas while the light is reflected from thelighted areas. OCR can scan several thousands of printed or type written characters persecond. So optical character readers are used in large volume applications .This avoidsdata mis-entry and errors that may occur due to normal entry. It is popularly used inbanks for reading the current status of passbook.

Bar- Code Reader

Data coded in the form of small lines (known as bars) are known as bar codes. Bar codesrepresent alphanumeric data by a combination of adjacent vertical lines (bars) by varyingtheir width and spacing between them to indicate the desired information. They areparticularly used for unique identification of all types of goods, books, postal packagesetc.

A bar-code reader is a device, which is used for reading (decoding) bar-coded data. Itmay be hand held scanner. It scans bar-code image and converts it into an alphanumericvalue, which is then fed to the computer to which the bar-code reader is connected.A bar-code reader uses a laser beam scanning technology. The laser beam is stroked

across the pattern of bars of a bar code. Different bar codes, having different patterns ofbars, reflect the beam in different ways, which is sensed by a light sensitive detector.Reflected light patterns are converted into electrical pulses.

The most commonly used bar code is Universal Product Code (UPC), which nowappears on almost all retail packages in USA. The UPC code uses a series of vertical barsof varying widths. These bars are detected as ten digits. The first five digits identify thesupplier or manufacturer of the item. The second five digits identify individual product.


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Magnetic- Ink Character Reader (MICR)

Magnetic Ink Character Reader (MICR) is widely used in banking where one has to deal

with a great number of cheques. MICR known in short is a method of machine readingcharacters made of ink containing magnetized particles. A special purpose machineknown as a reader/ sorter reads characters made of ink containing magnetized particles.The MICR system contains 14 globally approved characters by banking sector.

The method is fast, accurate and automatic. Moreover, the chances of error are negligible.

4. Electronic Card Reader

Electronic Cards and their associated readers offer another means of direct data entry intoa computer system. Electronic cards are small plastic cards having encoded data, whichare appropriate for the application for which they are used. Electronic cards are oftenused by banks and issued to the customers for use in automatic teller machines (ATM).

Electronic card Reader nowadays is used to read smart cards. It is also called smart cardreader. Smart card is a device like debit card and credit Card., in which there is anelectronic memory and is used for different functions. Smart cards used in big hotels arefunctioning as key for room locks.

Card reader reads the stored information in the card. Today, card reader also helps in safe

online shopping.

5. Voice Recognition Device

Voice recognition devices are input devices, which allow a person to input data tocomputer system by speaking to it. Hence, they computers are much easier to use.However, as a data input device, currently voice recognition systems have limitedsuccess, because correct interpretation by a machine of the large of words in thevocabulary of a language is difficult.

Although in its infancy, voice recognition systems are already being used for a wide

range of application. Some of its typical applications are as follows:

1) For Example, doctors in an operation room can request certain information abouta patient while operating.

2) For authentication of a user by a computer system based on voice input.


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OUTPUT DEVICES

An output device is an electromechanical device, which accepts data from a computer andtranslates them into a form, which is suitable for use by the outside world. (the users).Several output devices are available today. They can be broadly classified into the

following categories:

1. Monitors2. Printers3. Plotters4. Screen Image Projector5. Voice Response System

Output devices generate computer output, which can be broadly classified into thefollowing two (2) types

1. SoftCopy Output: A soft-copy output is an output, which is not produced on apaper or some material, which can be touched or carried for being shown toothers. They are temporary in nature and vanish after use.For example, output displayed on a terminal screen or spoken out by a voiceresponse system are soft-copy output.

2. HardCopy Output: A hard-copy output is an output, which is produced on apaper or some material, which can be touched and carried for being shown toothers. They are permanent in nature and can be kept in paper files or can belooked later, when the person is not using the computer.For example, output produced by printers or plotters on paper are hard-copy

output.

1. Monitors

Monitor is an output device, where you can get your output on a TV- like screen. It iscommonly classified as Monochrome,Gray-Scale and Color Monitor based on thecolors they display.

Monochrome is derived from Mono which means single and

Chrome means color; which means single color. Monochromemonitors are single color monitor like a black and white screen.

Gray- Scale monitors are special types of monitors for displayingoutput in different gray shades. These monitors in flat-panel arecommonly used in handy computers.


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Color monitors can give output as a combination of RGB (Red-Green-Blue) radiations. Due to RGB concept, they are capable of presentinggraphics in a higher resolution.

According to the technology monitors are classified in to following categories:

CRT Monitors

Almost monitors are based on Picture Tube Element as same as a television set. Thistube is known as Cathode Ray Tube or CRT in short. CRT technology is cheaper andcapable of presenting high quality colored output.

FLAT-PANEL Monitors

Recently a new technology in the display devices has been developed. In this technology,charged chemical gases adopt various chemical configurations to create images on the

screen. These are called Flat Panel Display. This device is mainly used in laptopcomputers.Flat panel monitors also have LCD technology which means Liquid Crystal Display. Theflat panel monitors are thinner and lighter.

PLASMA Monitors


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Plasma monitor is quite thin that is manufactured using a special type of gas between twoglass sheets. This special type of gas is neon or xenon. When gas is electrified through agrid of small electrodes, it shines.

2. Printers

Printers are the most commonly used output devices today for producing hard-copy

output.

The printers have two (2) basis of classification:

A. Classification based on the basis of printing technology, they aremainly categorized in two classes.

Impact Printers: In this type, the printers head physicallytouches the paper surface to produce the output. The head,always being in contact with the paper while printing, produces

high friction thus making it noisy. Graphical outputs are of lowquality in the case of impact printers.

Non-impact printers: In this type, the printers head does notphysically touch the paper to produce the impression. Generally,in this case, a fine jet of ink is spread over the paper surface. Dueto no contact between the printer head and paper, the frictiongenerated i9s very low, making it virtually noiseless. More over,multicolored output is possible. Graphics out generated is also ofhigh quality here.

B. Classification based on speed of printing : Here the various types ofprinters are classified as :

Low Speed printers: It is also called serial or character printer.It can print one character at a time. It is slowest and the cheapest

Plasma Monitor


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form of printers. Its speed is measured in characters per second.(CPS).

High speed printer, which print output as single line or wholepage at a time.It has following two types:

Line printer: It can print one line at output at atime. Its speed is measured in lines per minute(LPM).

Page printer: Here, the printer can generate onepage of output at a time. It is the fastest but thecostliest of printers. Its speed is measured in pagesper minute (PPM).

The various types of common printers in use today are described below.

Dot Matrix Printer

It is an impact printer. It is also character printer, which print one character at a time.They form characters and all kinds of images as a pattern of dot. So, it is called Dot-matrix printer. In this printer there is a print head, which has a matrix of pins in it. Eachpin when strikes with ribbon make a dot on a paper. Many dots constitute a character.Dot matrix printers are normally slow with speeds usually ranging between 30 to 600characters per second. However, they are cheap in terms of both initial cost and cost ofoperation. Hence, they are preferred by individuals and organizations for generatingprinted outputs, if the speed and quality of printing are not important factors. Many dotmatrix printers can print lines from left to right as well as from right to left. They are also

used for applications, which require multi copy output.

Inkjet Printer

Inkjet printers are character printers, which form character and all kinds of images byspraying small drops of ink on to the paper. The print head of an inkjet printer containsup to 64 tiny nozzles. TO print a character, the printer selectively heats the appropriateset of nozzles as the print head moves horizontally.

Inkjet printers produce higher quality output than dot-matrix printers, because they formcharacters by very tiny ink dots.

Inkjet printers are non-impact printer, because they print by spraying ink on the paper.Hence, they are quiet in operation.

Inkjet printers are slower than dot-matrix printer with speeds usually ranging between 40to 300 characters per second. The ink, which can be of various colors, is absorbed intothe paper and dries instantly. Typically, an inkjet printer is more expensive than a dot-matrix printer.


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Laser Printer

Laser printers are page printers, which print one page at a time. Laser printer produces

characters and other images on paper by directing a laser beam at a mirror, whichbounces the beam onto drum. The laser leaves a negative charge on the drum, to whichpositively charged black tones powder will stick. As paper rolls by the drum the toner istransferred to the paper. A hot roller then bonds the toner to the paper.

Laser printers produce very high quality output, because they form characters by verytiny ink particles. The most common laser printers have resolution of 600 dpi(dots perinch). Because, of their high resolution, these printers give excellent graphics art quality.

Laser printers are non-impact printers, because they do not have hammers striking on aninked ribbon or paper. Hence, they are very quiet in operation.

Laser printers are faster in printing speed than other printers. Low speed laser printer canprint 4 to 12 pages per minute. Very high speed laser printers are also available, whichcan print 500 to 1000 pages per minute. Because of their better print quality and printingspeed, laser printers are more expensive than other printers.

3. Plotter

The growth of computer aided design and drafting has created a demand for device thatcan produce high quality graphics in multiple colors. A plotter produces drawing usingpens that are attached to movable arms and are directed across the surface of a stationary

piece of paper. Many plotters, however, combine a movable pen armed with paper thatcan also roll back and forth to make the drawing.Plotter applications are not limited to computer aided design (CAD). High quality bargraphs and pie charts created with plotter can add interest and meaning to businesspresentations. One can print charts, drawing, maps and three dimensional illustrationswith plotter. Generally, plotter is of two types

Drum pen plotter

Flat bed plotter


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4. Screen Image Projector

Screen image projector is an output device, which is used to project information from acomputer on to a large screen (such as a cloth screen or a wall), so that it can besimultaneously viewed by a large group of people. This output device is very useful for

making presentation to a group of people with the direct use of a computer. Specialmarker pens had to be used for marking certain portions of the contents on thetransparency sheets during the presentation. A screen image projector greatly simplifiesthis job.Screen image projectors have become common presentation equipment today. They arecommonly used with portable notebook computers to quickly setup a modernpresentation facility at any place with great ease.

5. Voice Response System

Just as a voice recognition system allows a user to talk to a computer, similarly, a voice

response system enables a computer to talk to a user. A voice response system has anaudio-response device, which produces audio output. Obviously, the output is temporary,soft-copy output.Voice response systems are of two (2) types

1) Voice Reproduction System2) Speech Synthesizer

MEMORY

INTRODUCTION

Computer structure is not different for the human anatomy. Our entire body works like acomputer. We memories works we do and its duration and size depend upon ourindividual capacity. Computer also avails the facility of memory that helps us rememberour work. Computer memory is more efficient and more reliable than human memory.

WHAT IS MAIN MEMORY?

Memory is the working storage of computer. This is a very important part of computerwhich stores data temporarily or permanently for future use. Memory is also called

primary memory or main memory. Memory uses several spaces for storage that aredefinite in number called capacity or size of memory. The unit, that measures capacity ofmemory called byte.

Memory CapacityMemory capacity is defined in terms of the number of bytes a computer system can store.


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Memory capacity of a computer system is normally stated in terms ofKilobytes (KB) ,Megabytes (MB) , Gigabytes (GB).

Unit Size Description

Bit One Binary Digit Stores either a binary 0 or 1

Byte Eight bits One characterKilobyte (KB) 210 bytes About one page

Megabytes (MB) 220 bytes About the size of a short bookGigabyte (GB) 230 bytes 1,000 short book

Classification of MemoryMemory classification has been shown as under the chart

Cache Memory

Memory

CacheMemory

PrimaryMemory

SecondaryMemory

AnalogMemory

DigitalMemory

RAM(RandomAccess

Memory

ROM(Read Only

Memory

SRAM(Static RAM)

DRAM(Dynamic RAM)

PROM(Programmable

ROM)

EPROM(ErasableProgrammableROM)

EEPROM(ElectronicallyErasableProgrammable

Sequential AccessDevice

Direct AccessDevice

Magnetic Disk Optical Disk

Floppy Disk Hard Disk

CD - ROM WORM Disk

MagneticTape


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(i) PRIMARY MEMORYPrimary memory is a part of the CPU whereas the secondary memory is the external tothe CPU. The secondary memory stores the data and keeps it even when the electricity tothe PC is cut off whereas the primary looses its contents immediately.

(ii) SECONDARY MEMORY

All computers except very small systems contain both semiconductor as well as magneticmemory. This semiconductor memory is employed is employed as the main memory ( or primary memory) of the computer . It stores programs and data which are currentlyneeded by the CPU. The magnetic memory is used as secondary (or auxiliary memory).

The secondary memory is employed for bulk storage (mass storage) of programs, dataand other information. It has much larger capacity than the main memory. It storessystem software, assemblers, compilers, useful packages, large data files etc. Thesecondary memory is non-volatile in nature.

(iii) Cache Memory

Cache Memory is a high speed storage unit. It is much faster than main memory. Cachestorage is extremely expensive compared to main memory. The characteristics of cachememory compared to main memory are as under(i) Access time is less (ii) Access speed is more.

TYPES OF PRIMARY MEMORY

Primary Memory is basically used for doing the computers internal task. Primary is oftwo types from the technology point of view. These are:

(a)Analog Memory(b)Digital Memory

Based on its working methodology, it can be classified as follows:

1. Random Access Memory (RAM): It is the part of the primary memory which is usedby the computer for performing all jobs supplied by the user. Generally, all data storedhere is based on charge, and hence is power dependent. In this case, the user has bothread and write permission. At power off condition, the Ram looses all its contentspermanently. Basically, RAM comes into use when the user uses the computer.

Based on its functioning, Ram is of two types(i) Static Random Access Memory (SRAM): It is faster and hence costlier.

For this reason, it is available in limited amount in the computer. (SRAMcomprises only about 10% of total RAM).

(ii) Dynamic Random Access Memory (DRAM): This part of RAM isCapacitor based and hence it needs to be recharged at frequent intervals oftime to retain the information. This extra activity makes it comparatively


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slower than S-RAM. For this same reason, it is cheaper and is available inlarge amount in the computer.

2. Read Only Memory (ROM): This part of the memory is circuit based and all the

instructions stores here use logic gates rather electric charge. This makes ROM nonvolatile and hence its contents are not erased due to power shutdown or due to humanmanipulation. The contents of ROM remain unchanged through its life. Generally, ROMstores instruction necessary for ensuring proper working of the computer. Theseinstructions are never changed and are stored using hardware circuits. These instructionsare called FIRMWARE.

Types of ROM:

(i) Programmable Read Only Memory (PROM)(ii) Erasable Programmable Read Only Memory (EPROM)(iii) Electronically Erasable Programmable Read Only Memory (EEPROM)

TYPES OF SECONDARY MEMORY

Secondary memory is generally used by the users for storing large amount ofinformation. Based on the methods of accessing information, secondary memory can beof two types

(1)SEQUENTIAL ACCESS STORAGE DEVICE :In this type of storage device, the access time varies according to storage locationbecause here informations are accessed sequentially. . It finds its application inpreparation of telephone bills etc.

MAGNETIC TAPE:

Magnetic tape is the most popular storage medium for large data, which are sequentiallyaccessed and processed.

The magnetic tape medium is a plastic ribbon, which is usually inch or inch wide,and 50 to 2400 feet long. It is located with a magnetically recording material, such as ironoxide or chromium oxide.


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Like audio or videotape, the magnetic tape used in computer systems can also be erasedand reused indefinitely.

(2)DIRECT ACCESS STORAGE DEVICEThis type of storage device is used in those applications where information has to be

accessed at random or directly. In this type of device, accessing of any information takessame time irrespective of its position. This type of device is used in reservation system.

MAGNETIC DISK :Magnetic Disk is the most popular storage medium for direct access secondary storage.

Due to their random access capability, magnetic disks are the most popular on linestorage device.

A magnetic disk is a thin, circular plate/ platter made of metal or plastic, which is usuallycoated on the both sides with a magnetizable recording material. The disk itself is storedin a specially designed protective envelope or cartridge.

Types of Magnetic Disk :

(a)Floppy Disk : Floppy disks are made of thin , flexible plastic material. Here aread write head is available for each surface and the head physically touches thesurface reading data. Floppy disks are portable, quite cheap, but have less storagecapacity. Floppy disks are basically of the following types :

(i) Single Sided Single Density (SSSD)(ii) Single Sided Double Density (SSDD)

(iii) Double Sided Single Density (DSSD)

(iv) Double Sided Double Density (DSDD)

The most commonly used variety of floppy disk is DSDD having a capacity of 1.44 MB


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b) Hard Disk : Hard disks are thin circular disks made of a rigid metallic materialand coated with magnetic oxide. A read and write head is available for each of itssurfaces but to avoid friction, the head does not physically touch the surface of thehard disk. Because of their extremely high capacity and high speed, hard disks arecostlier. For protection, hard disk is permanently housed inside the computer in a

protective metallic jacket and for this it is also known as fixed disk. Generally, harddisks have capacities in the range of gigabytes.

OPTICAL DISK

Optical disk or optical media are mass storage devices with huge capacity. The advent ofcompact disk (CD) , anon erasable optical disk, made it possible to develop a new lowcost storage technology.

An optical disk storage system consists of a rotating disk which is coated with a thinmetal or some other material that is highly reflective. Laser beam technology is used forrecording / reading of data on the disk. Due to use of laser beam technology, optical disksare also known as laser disks or optical laser disk.

Compact Disk (CD) :

Compact Disks have got extremely high capacity of data storage and works very fast. Ithas got a long life , provided that it is used properly . Generally, compact disks are usedto store extremely important software. Here, data is stored optically on spiral tracks. Atthe time of recording some information in the CD, laser beam of very high intensity ismade incident on the spinning disk.


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Three types of CD are available :

(a)CD-ROM (Compact Disk Read Only Memory) :The original, standard CD, CD-ROM stands for Compact Disc, Read-OnlyMemory. What this means is that you can only read information from a CD-ROM; you cant add new information in a way.

(b)CD-R :If you have a CD-RW drive you can permanently store information on a CD-R(Compact Disc Record able) disc. The information you write or burn to a CD-R ispermanent and cant be changed or erased. You can also use CD-r discs to createmusical CDs that you can listen to in a stereo system.You can read from it, but you cant write to it.

(c)CD RW :Unlike CD-R discs, a CD-RW (Compact Disc-ReWritable) disc can be written toomany times. You can also modify and erase information on a CD-RW disc ifyou have a CD-RW drive, of course.

COMPUTER SOFTWARE

INTRODUCTION

Two basic things make up a computer: hardware and software. You simply cantone without the other.

COMPUTER HARDWAREMechanical, electrical and electronic parts of a computer are called computerhardware. In other words, the parts of a computer system that we can touch andsee are hardware. Input, Output, Storage, processing and control devices of acomputer system are called hardware.


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COMPUTER SOFTWARE

The software is the programs that are required to control the several devices.Without software the system can not be initialized or controlled and all thehardware components still machine.

CLASSIFICATION OF SOFTWARE

SOFTWARE

SYSTEM SOFTWARE APPLICATION SOFTWARE UTILITY PROGRAM

Operating System Language Translator Disk fragmenetor Virus Scanner Virus remover

User application software Application package


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Number System and Representation

Binary Number System

We have already mentioned that computer can handle with two types of signals,therefore, to represent any information in computer; we have to take help of these twosignals. These two signals correspond to two levels of electrical signals, and symbolicallywe represent them as 0 and 1.In our day to day activities for arithmetic, we use the Decimal Number System. Thedecimal number system is said to be of base, or radix 10, because it uses ten digits andthe coefficients are multiplied by power of 10.

A decimal number such as 5273 represents a quantity equal to 5 thousands plus 2

hundreds, plus 7 tens, plus 3 units. The thousands, hundreds, etc. are powers of 10implied by the position of the coefficients. To be more precise, 5273 should be written as:

However, the convention is to write only the coefficient and from their position deducethe necessary power of 10.In decimal number system, we need 10 different symbols. But in computer we haveprovision to represent only two symbols. So directly we can not use decimal numbersystem in computer arithmetic.For computer arithmetic we use binary number system. The binary number system usestwo symbols to represent the number and these two symbols are 0 and 1.

The binary number system is said to be of base 2 or radix 2, because it uses two digitsand the coefficients are multiplied by power of 2.The binary number 110011 represents the quantity equal to:

(in decimal)

We can use binary number system for computer arithmetic.

Decimal Number Systems

The Decimal Number System uses base 10. It includes the digits from 0 through 9. Theweighted values for each position are as follows:

10^4 10^3 10^2 10^1 10^0 10^-1 10^-2 10^-3

10000 1000 100 10 1 .1 .01 .001

You have been using the decimal (base 10) numbering system for so long that you oftentake it for granted. When you see a number like "123", you don't think about the value


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123. Instead, you generate a mental image of how many items this value represents. Inreality, however, the number 123 represents:

1 * 10^2 + 2 * 10^1 + 3 * 10^0 =

1 * 100 + 2 * 10 + 3 * 1 =

100 + 20 + 3 =

123

Each digit appearing to the left of the decimal point represents a value between zero andnine times power of ten represented by its position in the number. Digits appearing to theright of the decimal point represent a value between zero and nine times an increasingnegative power of ten. For example, the value 725.194 is represented as follows:

7 * 10^2 + 2 * 10^1 + 5 * 10^0 + 1 * 10^-1 + 9 * 10^-2 + 4 * 10^-3 =

7 * 100 + 2 * 10 + 5 * 1 + 1 * 0.1 + 9 * 0.01 + 4 * 0.001 =

700 + 20 + 5 + 0.1 + 0.09 + 0.004 =

725.194

Hexadecimal number:The hexadecimal number system is said to be of base, or

radix 16, because it uses 16 symbols and the coefficients are multiplied by power of 16.Sixteen digits used in hexadecimal system are: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, Eand F.

Octal Number:The octal number system is said to be of base, or radix 8, because ituses 8 digits and the coefficients are multiplied by power of 8.Eight digits used in octal system are: 0, 1, 2, 3, 4, 5, 6 and 7.


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Method for conversion from Binary to Decimal

Conversion from base-2 to base-10 proceeds by applying the preceding algorithm, so tospeak, in reverse. The bits of the binary number are used one by one, starting with the

most significant bit. Beginning with the value 0, repeatedly double the prior value andadd the next bit to produce the next value. This can be organized in a multi-column table.For example to convert 100101011012 to decimal:

Prior value 2 + Next Bit Next value

= 0

0 2 + 1 = 1

1 2 + 0 = 2

2 2 + 0 = 4

4 2 + 1 = 9

9 2 + 0 = 18

18 2 + 1 = 37

37 2 + 0 = 74

74 2 + 1 = 149

149 2 + 1 = 299

299 2 + 0 = 598

598 2 + 1 = 1197

The result is 119710. This method is an application of the Horner scheme.

Bin: 1 0 0 1 0 1 0 1 1 0 1

Dec: 12^10 + 02^9 + 02^8 + 12^7 + 02^6 + 12^5 + 02^4 + 12^3 + 12 2 + 02^1+ 12^0 = 1197

The fractional parts of a number are converted with similar methods. They are againbased on the equivalence of shifting with doubling or halving.

In a fractional binary number such as .110101101012, the first digit is , the

second , etc. So if there is a 1 in the first place after the decimal, then the

number is at least , and vice versa. Double that number is at least 1. This suggests thealgorithm: Repeatedly double the number to be converted, record if the result is at least 1,and then throw away the integer part.


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For example, 10, in binary, is:

Converting Result

0.

0.0

0.01

0.010

0.0101

Thus the repeating decimal fraction 0.3... is equivalent to the repeating binary fraction0.01... .

Or for example, 0.110, in binary, is:

Converting Result

0.1 0.

0.1 2 = 0.2 < 1 0.0

0.2 2 = 0.4 < 1 0.00

0.4 2 = 0.8 < 1 0.000

0.8 2 = 1.6 1 0.0001

0.6 2 = 1.2 1 0.00011

0.2 2 = 0.4 < 1 0.0001100.4 2 = 0.8 < 1 0.0001100

0.8 2 = 1.6 1 0.00011001

0.6 2 = 1.2 1 0.000110011

0.2 2 = 0.4 < 1 0.0001100110

This is also a repeating binary fraction 0.000110011... . It may come as a surprise thatterminating decimal fractions can have repeating expansions in binary. It is for thisreason that many are surprised to discover that 0.1 + ... + 0.1, (10 additions) differs from1 in floating point arithmetic. In fact, the only binary fractions with terminating

expansions are of the form of an integer divided by a power of 2, which 1/10 is not.

The final conversion is from binary to decimal fractions. The only difficulty arises withrepeating fractions, but otherwise the method is to shift the fraction to an integer, convertit as above, and then divide by the appropriate power of two in the decimal base. Forexample:


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x = 1100 .101110011100...

= 1100101110.0111001110...

= 11001 .0111001110...

= 1100010101

x = (789/62)10

Method for conversion from Binary to Hexadecimal

To convert a binary number into its hexadecimal equivalent, divide it into groups of fourbits. If the number of bits isn't a multiple of four, simply insert extra 0 bits at the left(called padding). For example:

10100102 = 0101 0010 grouped with padding = 5216

110111012 = 1101 1101 grouped = DD16

Method for conversion from Binary to Octal

The process is the reverse of previous algorithm. The binary digits are grouped by threes,starting from the decimal point and proceeding to the left and to the right. (Add leadingor trailing 0s to fill out the last group of 3 if necessary.) Then replace each trio with theequivalent octal digit.

For instance, convert binary 1010111100 to octal:

001 010 111 100

1 2 7 4

Thus 10101111002 = 12748

Method for conversion from Decimal to Binary

Let's convert the decimal number 15610 to binary. Write the decimal number as thedividend inside an upside-down "long division" symbol. Write the base of the destinationsystem (in our case, "2" for binary) as the divisor outside the curve of the division symbol.

2)1561. Write the integer answer (quotient) under the long division symbol, and write theremainder (0 or 1) to the right of the dividend.2)156 0

78

2. Continue downwards, dividing each new quotient by two and writing the remaindersto the right of each dividend. Stop when the quotient is 1.2)156 0

2)78 0


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2)39 1

2)19 1

2)9 1

2)4 0

2)2 0

2)1 1

2)0 0

3. Starting with the bottom 1, read the sequence of 1's and 0's upwards to the top. Youshould have 10011100. This is the binary equivalent of the decimal number 156. Or,written with base subscripts: 15610 = 100111002

Method for conversion from Hexadecimal to Binary

Binary may be converted to and from hexadecimal somewhat more easily. This is becausethe radix of the hexadecimal system (16) is a power of the radix of the binary system (2).More specifically, 16 = 24, so it takes four digits of binary to represent one digit ofhexadecimal.

The following table shows each hexadecimal digit along with the equivalent decimal valueand four-digit binary sequence:

Hex Dec Binary

0 0 0000

1 1 0001

2 2 0010

3 3 0011

4 4 0100

5 5 0101

6 6 0110

7 7 0111

8 8 1000

9 9 1001

A 10 1010

B 11 1011

C 12 1100

D 13 1101

E 14 1110F 15 1111

To convert a hexadecimal number into its binary equivalent, simply substitute thecorresponding binary digits:

3A16 = 0011 10102


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E716 = 1110 01112

Method for conversion from Octal to Binary

To convert octal to binary, replace each octal digit by its binary representation.Example: Convert 518to binary:

58 = 101218 = 0012Thus: 518 = 101 0012

Binary-coded decimal (BCD)

In computing and electronic systems, binary-coded decimal (BCD) (sometimescalled natural binary-coded decimal, NBCD) is an encoding for decimal numbers inwhich each digit is represented by its own binary sequence. Its main virtue is that itallows easy conversion to decimal digits for printing or display and faster decimalcalculations. Its drawbacks are the increased complexity of circuits needed to implementmathematical operations and a relatively inefficient encodingit occupies more space

than a pure binary representation.

In BCD, a digit is usually represented by four bits which, in general, represent thevalues/digits/characters 09. Other bit combinations are sometimes used for a sign orother indications.

Although BCD is not as widely used as it once was, decimal fixed-point and floating-point are still important and continue to be used in financial, commercial, and industrialcomputing. Modern decimal floating-point representations use base-10 exponents, but notBCD encodings. Current hardware implementations, however, convert the compresseddecimal encodings to BCD internally before carrying out computations. Software

implementations use BCD or some other 10n base, depending on the operation.

To BCD-encode decimal number using the common encoding, each decimal digit isstored in a four-bit nibble.

Decimal: 0 1 2 3 4 5 6 7 8 9

BCD: 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001

Thus, the BCD encoding for the number 127 would be:

0001 0010 0111

Since most computers store data in eight-bit bytes, there are two common ways of storingfour-bit BCD digits in those bytes:

each digit is stored in one nibble of a byte, with the other nibble being set to allzeros, all ones (as in the EBCDIC code), or to 0011 (as in the ASCII code)

two digits are stored in each byte.


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Unlike binary-encoded numbers, BCD-encoded numbers can easily be displayed bymapping each of the nibbles to a different character. Converting a binary-encodednumber to decimal for display is much harder, as this generally involves integermultiplication or divides operations. BCD also avoids problems where fractions that canbe represented exactly in decimal cannot be in binary (e.g. one-tenth).

American Standard Code for Information Interchange (ASCII)

American Standard Code for Information Interchange (ASCII), is a character-encodingscheme based on the ordering of the English alphabet. ASCII codes represent text incomputers, communications equipment, and other devices that work with text. Mostmodern character-encoding schemeswhich support many more characters than did theoriginalhave a historical basis in ASCII.

Historically, ASCII developed from telegraphic codes. Its first commercial use was as aseven-bit teleprinter code promoted by Bell data services. Work on ASCII formally

began October 6, 1960, with the first meeting of the American Standards Association'ssubcommittee. The first edition of the standard was published in 1963 a major revision in1967 and the most recent update in 1986. Compared to earlier telegraph codes, theproposed Bell code and ASCII were both ordered for more convenient sorting (i.e.,alphabetization) of lists, and added features for devices other than teleprinters.

ASCII includes definitions for 128 characters: 33 are non-printing control characters(now mostly obsolete) that affect how text is processed:94 are printable characters, andthe space is considered an invisible graphic. The most commonly used characterencoding on the World Wide Web was US-ASCII until 2008, when it was surpassed byUTF-8.


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IT TOOLS AND APPLICATIONS LANGUAGE AND SOFTWARE


LANGUAGE AND SOFTWARE

3.1 INTRODUCTION

In the previous lesson we discussed about the different parts and configurations ofcomputer. It has been mentioned that programs or instructions have to be fed to the

computer to do specific task. So it is necessary to provide sequence of instructions so thatyour work can be done. We can divide the computer components into two major areas,namely, hardware and software. Hardware is the machine itself and its various individualequipment. It includes all mechanical, electronic and magnetic devices such as monitor,printer, electronic circuit, floppy and hard disk. In this lesson we will discuss about theother part, namely, software.

3.2 OBJECTIVES

After going through this lesson you will be able to

explain the concept of software distinguish between different types of software differentiate application software from system software define a language

differentiate between different types of language

distinguish between compiler and interpreter

3.3 WHAT IS SOFTWARE?

As you know computer cannot do anything without instructions from the user. In order todo any specific job you have to give a sequence of instructions to the computer. This setof instructions is called a computer program. Software refers to the set of computerprograms, procedures that describe the programs, how they are to be used. We can saythat it is the collection of programs, which increase the capabilities of the hardware.Software guides the computer at every step where to start and stop during a particular job.The process of software development is called programming.

You should keep in mind that software and hardware are complementary to each other.Both have to work together to produce meaningful result. Another important point youshould know that producing software is difficult and expensive.

3.4 SOFTWARE TYPES

Computer software is normally classified into two broad categories.

Application Software

System software

Application Software: Application Software is a set of programs to carry out operationsfor a specific application. For example, payroll is an application software for anorganization to produce pay slips as an output. Application software is useful for word


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processing, billing system, accounting, producing statistical report, analysis of numerousdata in research, weather forecasting, etc. In later modules you will learn about MSWORD, Lotus 1-2-3 and dBASE III Plus. All these are application softwares.

Another example of application software is programming language. Among the

programming languages COBOL (Common Business Oriented Language) is moresuitable for business application whereas FORTRAN (Formula Translation) is useful forscientific application. We will discuss about languages in next section.

System Software: You know that an instruction is a set of programs that has to be fed tothe computer for operation of computer system as a whole. When you switch on thecomputer the programs written in ROM is executed which activates different units ofyour computer and makes it ready for you to work on it. This set of program can becalled system software. Therefore system software may be defined as a set of one or moreprograms designed to control the operation of computer system.

System software are general programs designed for performing tasks such as controllingall operations required to move data into and out of the computer. It communicates withprinters, card reader, disk, tapes etc. monitor the use of various hardware like memory,CPU etc. Also system software are essential for the development of applicationssoftware. System Software allows application packages to be run on the computer withless time and effort. Remember that it is not possible to run application software withoutsystem software.

Development of system software is a complex task and it requires extensive knowledgeof computer technology. Due to its complexity it is not developed in house. Computermanufactures build and supply this system software with the computer system. DOS,

UNIX and WINDOWS are some of the widely used system software. Out of these UNIXis a multi-user operating system whereas DOS and WINDOWS are PC-based. We willdiscuss in detail about DOS and WINDOWS in the next module.

3.5 WHAT IS LANGUAGE?

You are aware with the term language. It is a system of communication between you andme. Some of the basic natural languages that we are familiar with are English, Hindi,Oriya etc. These are the languages used to communicate among various categories ofpersons. But how you will communicate with your computer. Your computer will notunderstand any of these natural languages for transfer of data and instruction. So there areprogramming languages specially developed so that you could pass your data andinstructions to the computer to do specific job. You must have heard names likeFORTRAN, BASIC, COBOL etc. These are programming languages. So instructions orprograms are written in a particular language based on the type of job. As an example, forscientific application FORTRAN and C languages are used. On the other hand COBOL isused for business applications.


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3.5.1 Programming Languages

There are two major types of programming languages. These are Low Level Languagesand High Level Languages. Low Level languages are further divided in to Machine

language and Assembly language.

3.5.2 Low Level Languages

The term low level means closeness to the way in which the machine has been built. Lowlevel languages are machine oriented and require extensive knowledge of computerhardware and its configuration.

(a) Machine Language

Machine Language is the only language that is directly understood by the computer. It

does not needs any translator program. We also call it machine code and it is written asstrings of 1's (one) and 0s (zero). When this sequence of codes is fed to the computer, itrecognizes the codes and converts it in to electrical signals needed to run it. For example,a program instruction may look like this:

1011000111101

It is not an easy language for you to learn because of its difficult to understand. It isefficient for the computer but very inefficient for programmers. It is considered to thefirst generation language. It is also difficult to debug the program written in this

language.

Advantage

The only advantage is that program of machine language run very fast because notranslation program is required for the CPU.

Disadvantages

1. It is very difficult to program in machine language. The programmer has to knowdetails of hardware to write program.2. The programmer has to remember a lot of codes to write a program which results inprogram errors.3. It is difficult to debug the program.


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(b) Assembly Language

It is the first step to improve the programming structure. You should know that computercan handle numbers and letter. Therefore some combination of letters can be used tosubstitute for number of machine codes.

The set of symbols and letters forms the Assembly Language and a translator program isrequired to translate the Assembly Language to machine language. This translatorprogram is called `Assembler'. It is considered to be a second-generation language.

Advantages:

1. The symbolic programming of Assembly Language is easier to understand and savesa lot of time and effort of the programmer.2. It is easier to correct errors and modify program instructions.3. Assembly Language has the same efficiency of execution as the machine levellanguage. Because this is one-to-one translator between assembly language program and

its corresponding machine language program.

Disadvantages:

1. One of the major disadvantages is that assembly language is machine dependent. Aprogram written for one computer might not run in other computers with differenthardware configuration.

3.6 HIGH LEVEL LANGUAGES

You know that assembly language and machine level language require deep knowledge

of computer hardware where as in higher language you have to know only theinstructions in English words and logic of the problem irrespective of the type ofcomputer you are using.

Higher level languages are simple languages that use English and mathematical symbolslike +, -, %, / etc. for its program construction.

You should know that any higher level language has to be converted to machine languagefor the computer to understand.

Higher level languages are problem-oriented languages because the instructions are

suitable for solving a particular problem. For example COBOL (Common BusinessOriented Language) is mostly suitable for business oriented language where there is verylittle processing and huge output. There are mathematical oriented languages likeFORTRAN (Formula Translation) and BASIC (Beginners All-purpose SymbolicInstruction Code) where very large processing is required.


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Thus a problem oriented language designed in such a way that its instruction may bewritten more like the language of the problem. For example, businessmen use businessterm and scientists use scientific terms in their respective languages.

Advantages of High Level Languages

Higher level languages have a major advantage over machine and assembly languagesthat higher level languages are easy to learn and use. It is because that they are similar tothe languages used by us in our day to day life.

3.6.1 Compiler

It is a program translator that translates the instruction of a higher level language tomachine language. It is called compiler because it compiles machine languageinstructions for every program instructions of higher level language. Thus compiler is aprogram translator like assembler but more sophisticated. It scans the entire program firstand then translates it into machine code.

The programs written by the programmer in higher level language is called sourceprogram. After this program is converted to machine languages by the compiler it iscalled object program.

A compiler can translate only those source programs, which have been written, in thatlanguage for which the compiler is meant for. For example FORTRAN compiler willnot compile source code written in COBOL language.

Object program generated by compiler is machine dependent. It means programs

compiled for one type of machine will not run in another type. Therefore every type ofmachine must have its personal compiler for a particular language. Machineindependence is achieved by using one higher level language in different machines.

3.6.2 Interpreter

An interpreter is another type of program translator used for translating higher levellanguage into machine language. It takes one statement of higher level languages,translate it into machine language and immediately execute it. Translation and executionare carried out for each statement. It differs from compiler, which translate the entiresource program into machine code and does involve in its execution..

The advantage of interpreter compared to compiler is its fast response to changes insource program. It eliminates the need for a separate compilation after changes to eachprogram. Interpreters are easy to write and do not require large memory in computer. Thedisadvantage of interpreter is that it is time consuming method because each time astatement in a program is executed then it is first translated. Thus compiled machinelanguage program runs much faster than an interpreted program.


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IT TOOLS AND APPLICATIONS DOS


Disk Operating System

The Operating System

Most Personal Computers run under the MSDOS Operating System. MSDOS being the

Microsoft Disk Operating System. It is estimated that almost 10 million machines rununder the MSDOS Operating System and some 20,000 or more end-user applicationshave been published to run with it.

The Operating System is the program which provides organized services to the computeruser and the application programs that they wish to use. These services consist mainly ofaccess to the hardware resources such as the disk drives, keyboard, etc.

The Operating System has three main constituents:-

The system files which are hidden. Their function is to perform such basic tasks as

reading the keyboard, displaying characters on the screen, opening and closing files etc.

The command interrupter, COMMAND.COM which reads commands typed at thekeyboard and attempts to obey them. COMMAND.COM has some simple commandsbuilt in - these are known as internal commands.

A series of utility programs covering functions not handled by the internal commands.There are approximately 52 of these commands, the exact number varies betweendifferent versions of MSDOS , ranging from COPY to copy files to EDIT the text editor,and many more

Disks and Drives

Because most of your computers Memory (RAM) is temporary, its contents are erasedwhen you switch off the power. You need a place to store the Operating System,application programs and your work. That's where disks come in, you store anyinformation you want to keep onto disks.

There are two types of disk: Floppy disks & Hard disks.

Floppy disks (Diskettes)

A disk is a magnetically coated disk of thin plastic, inside a rigid plastic cover.

You can use Floppy disks to:

Transfer information from one computer to another.

Store the Operating System, or application program and your work, if you don't have aHard disk.


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Keep a copy of information that you have on your Hard disk (Backup).

You need only format a disk once. After that, you can use the disk again and againwithout having to reformat it. Formatting a disk you have previously used erases any dataon the disk, so only reformat a disk if you are sure you don't need any of the data on it.

Choosing disks

Diskettes come in various forms, so it is important to choose diskettes that match the typeof diskette drive installed in your computer. Several different types are available :

5.25inch 360 Kbyte - Very rarely used now

5.25inch 1.2 Mbyte - Uncommon but still in use

3.5inch 720 Kbyte - Getting less common, still in use

3.5inch 1.44 Mbyte - The standard in most modern computers.

It should be noted that :-

A 720 Kbyte drive can only read and write to a 720 Kbyte diskette

A 1.44 Mbyte drive can read and write to both 720 Kbyte and 1.44 Mbyte diskettes.However you must use special formatting instructions to format a 720 Kbyte diskette in a1.44 Mbyte drive.

The visible difference between a 720 Kbyte diskette and a 1.44 Mbyte diskette is thatthere is no extra notch on a 720 Kbyte diskette.

Hard disks

A Hard disk is a disk that is enclosed in a permanently sealed metal housing. Hard disksare better than Floppy diskettes in two main respects:

You can store much more information on a Hard disk than on a diskette. For example, a40 Mbyte Hard disk holds the equivalent of almost twenty nine 1.44 Mbyte Floppydiskettes.

They are up to 600 times faster at finding and loading information into the computersMemory .


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What is Booting?

To run DOS on a computer, it should be the first program to be executed when thecomputer is switched on. This led to a problem for the designers: "How can DOS beloaded and executed when there is no DOS program running to load and execute

*it*??!!". Well, just as the fictional Baron Munchausen managed to pull himself up by hisown bootstraps, the computer manages this seemingly impossible trick, and the term"bootstrapping", or "booting up" is applied to this process.

How do you communicate with DOS?

DOS is an entirely text based system. All it provides for the user is a prompt: "C:>" or"A:>", where the user can type in commands from the keyboard. The system is entirelycase insensitive: so either "Format C:" or "format c:" would erase your hard disk...

The latter example is of course a small warning: with DOS comes power, you can very

easily mess up your system if you use powerful commands in the wrong way. Thecommands you should be careful of are: "Format", "Recover", and "Del". All of theseperform useful functions, when used correctly, and all the others are pretty much safe touse.

How are files named?

While newer versions of DOS support longer filenames, the standard DOS filenameformat remains: 1-8 letter name, period, 3 letter extension eg:

PROGRAM.EXEDATA.DATLETTER.DOC

The extension to a file's name is there to allow files of a similar type to be groupedtogether. I.e. all word processor files might have the extension .DOC, while all picturefiles might have the extension .PIC While these extensions can be specified by the user,many programs have used them to differentiate between formats, and so they havegradually become standardized. For example you would expect a ".TXT" file to be a filecontaining unformatted text, or a ".BMP" file to be in a bit mapped graphics file format.

To completely specify a file on your computer you must specify its drive and directorypath, and its filename. However a file does not always have to be specified in thiscomplete form: If it is in the current directory, then you can just enter its filename.


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How are directories named?Every disk drive has a root directory which can have subdirectories which are named in

the same format as filenames, (though generally without any extension). Thesubdirectories can have subdirectories and so on. Eg: a floppy disk might contain thefollowing directory structure:

PICTURESHOLIDAYITALYFRANCE

FAMILYPETS

TEXTLETTERSEMAIL

A directory path name includes the disk drive and all subdirectories needed to specify adirectory on a disk. The disk drive is specified by a single letter. Eg: The floppy diskdrive is A and the hard disk drive is C.

The drive letter, is followed by a colon, the directory path names are separated bybackward slashes (\), (*Not* forward slashes like internet addresses). Eg. In the aboveexample "A:\PICTURES\HOLIDAY\FRANCE" would be more than likely to containpictures of a few baguettes and onions.

How is DOS used?

When you type anything at the DOS prompt, and press enter, you are telling DOS to runa program.

It will first look to see if there is an internal command program which has that name,and if it does not find one, then it will look to see if there is a file on disk with that name.

If it finds an external file with the extension .COM (command), or .EXE (executable),then the program is loaded and run. At this point DOS looses control of the computeruntil the program has ended. However parts of it are still used by the programs as they arerunning, e.g. to load and save files etc.

MS-DOS Commands.

A command is the name of a special program that makes your computer carry out a task.There are two types of MS-DOS commands - internal and external.


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IT TOOLS AND APPLICATIO

it tools and applications

Documents