Computer Fundamentals, DOS & Windows Fundamentals

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    Published by CFS Documentation CellCentre for Electronics Design and Technology of IndiaAn Autonomous Scientific Society under Department of Electronics,Govt. of India,

    New Delhi.

    First Edition: 1999

    TRADEMARKS: All brand names and product names mentioned in this book are trademarks or registered trademarks oftheir respective companies.

    Every effort has been made to supply complete and accurate information. However, CEDTI assumes no responsibility for itsuse, nor for any infringement of the intellectual property rights of third parties which would result from such use.

    No part of this publication may be stored in a retrieval system, transmitted or reproduced in any form or by any means,electronic, photocopy, photograph, magnetic or otherwise, without written permission of CEDTI.

    CEDTI/CFS/99/4/1.1/R1

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    FOREWORD

    The information technology and telecom sectors have suddenly opened up avenues, which require a very

    large specially trained manpower. These sectors are highly dynamic and need training and re-training of manpower

    at a rapid rate. The growing gap of requirement of the industry and its fulfillment has created a challenging

    situation before manpower training institutes of the country. To meet this challenge most effectively, Centre for

    Electronics Design and Technology of India (CEDTI) has launched its nation-wide franchising scheme.

    Centre for Electronics Design and Technology of India (CEDTI) is an Autonomous Scientific Society under

    the Govt. of India, Department of Electronics with its Headquarters at New Delhi. It operates seven centres

    located at Aurangabad, Calicut, Gorakhpur, Imphal, Mohali, Jammu and Tezpur. The scheme will be implemented

    and coordinated by these centres.

    The scheme endeavours to promote high quality computer and information technology education in the

    country at an affordable cost while ensuring uniform standards in order to build a national resource of trained

    manpower. Low course fees will make this education available to people in relatively small, semi urban and rural

    areas. State-of-the-art training will be provided keeping in view the existing and emerging needs of the industrial

    and Govt. sectors. The examinations will be conducted by CEDTI and certificates will also be awarded by CEDTI.

    The scheme will be operated through all the seven centres of CEDTI.

    The CEDTI functions under the overall control and guidance of the Governing Council with Secretary,

    Department of Electronics as its Chairman. The members of the council are drawn from scientific, government

    and industrial sectors. The centres have separate executive committees headed by Director General, CEDTI. Themembers of these committees are from academic/professional institutes, state governments, industry and

    department of electronics.

    CEDTI is a quality conscious organisation and has taken steps to formally get recognition of the quality and

    standards in various activities. CEDTI, Mohali was granted the prestigious ISO 9002 certificate in 1997. The other

    centres have taken steps to obtain the certification as early as possible. This quality consciousness will assist

    CEDTI in globalizing some of its activities. In keeping with its philosophy of ‘Quality in every Activity’, CEDTI will

    endeavour to impart state of the ar t – computer and IT training through its franchising scheme.

    The thrust of the Software Courses is to train the students at various levels to carry out the Management

    Information System functions of a medium sized establishment, manufacture software for domestic and export

    use, make multimedia presentations for management and effectively produce various manufacturing and

    architectural designs.

    The thrust of the Hardware Courses at Technician and Telecommunication Equipment Maintenance Course

    levels is to train the students to diagnose the faults and carry out repairs at card level in computers, instruments,

    EPABX, Fax etc. and other office equipment. At Engineer and Network Engineer levels the thrust is to train them

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    as System Engineers to instal and supervise the Window NT, Netware and Unix Networking Systems and repair

    Microcontrollers / Microprocessor based electronic applications.

    An Advisory Committee comprising eminent and expert personalities from the Information Technology field

    have been constituted to advise CEDTI on introduction of new courses and revising the syllabus of existing

    courses to meet the changing IT needs of the trade, industry and service sectors. The ultimate objective is to

    provide industry-specific quality education in modular form to supplement the formal education.

    The study material has been prepared by the CEDTI, document centre. It is based on the vast and rich

    instructional experience of all the CEDTI centres. Any suggestions on the improvement of the study material will

    be most welcome.

    (R. S. Khandpur)

    Director General (CEDTI)

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    TABLE OF CONTENTS

    UNIT CHAPTER NAME PAGE NO.

    SECTION - A

    COMPUTER FUNDAMENTALS

    1 Computers - History & Generations 11

    2 Classification of Computers 15

    3 Number System 19

    4 Concepts of Hardware & Software 25

    5 Concepts of Virus & Preventive Measures 33

    SECTION - B

    MS-DOS

    6 MS-DOS Operating System 39

    7 Disk Organisation 43

    8 DOS Commands 45

    SECTION - C

    WINDOWS FUNDAMENTALS

    9 Windows 95 Basics 69

    10 Starting & Exiting from a Program 81

    11 Using Help 91

    12 Control Panel & System Settings 95

    13 Printing with Windows 95 99

    14 Keyboard Commands 105

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    PREFACE

    ‘Operating Systems’ is an essential pre-requisite for all courses in study of Computer Science.

    This study material is designed to provide the basic knowledge on this topic. MS-DOS (Disk

    Operating System) & MS-Windows are most widely used operating system on Personal

    Computers. These have been used to explain the basic concepts and principles of the operating

    system . The text has been developed using the Windows-95 operating system. Most of the

    treatment is fairly general and will apply to the subsequent upgradations in the Windows

    Operating System.

    Theoretical Concepts have been illustrated by including the practical applications. It isrecommended that a student should have an access to PC using MS DOS & MS-Windows to

    derive the maximum benefit from this course material. As far as instructors are concerned, they

    can carry out various practical exercises to illustrate the teaching points being made.

    This book begins with the general background to the subject and is divided into three sections:

    Section A discusses about the Computer Fundamentals also giving a review of the history

    and generations of computers. It further guides the students towards the basic concepts of

    Software and Hardware giving them the information about the viruses and the preventive

    measures as well.

    Section B covers MS-DOS and tells us about the details which can be effectively implemented.

    It tells students about disk organisation and the DOS commands.

    Section C elaborates the Windows Operating System in a detailed manner. From the very

    basic concepts of the Windows, it leads students towards its system settings and its high end

    practical usage.

    The document strives to make the students acquire the practical information most

    comprehensively.

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    COMPUTER - HISTORY, GENERATIONS

    DEFINITION OF COMPUTERComputer means different thing to different people. The principle of INPUT-PROCESS-OUTPUT  is applied to the computer. It is electronic device capable of solving problem ormanipulating data by accepting data, performing prescribed operation (mathematical andlogical) on the data & supplying the result of these operations as output.

    CHARACTERISTICS OF COMPUTER

    SPEED: Speed is the rate at which a computer can process instructions per second. Atypical computer is capable of doing millions of calculations per second.

    ACCURACY: Computers are not only fast, but they are highly accurate. The term“Computer Error” is commonly used as more of “Human Error”. As the computer onlycarries out programmer’s instructions efficiently, if these instructions have errors, theyare bound to appear in the computer’s output. Hence, if the data and instructions givento the computer are reliable, only then the result produced will be accurate.

    DILIGENCE: Human beings generally tire after a couple of hours of work and tend tomake mistakes. But computers simply do not get bored and can perform the sameoperations repeatedly over any length of time. Moreover the computer will take the same

    time to do the first calculation as the 1000th

     calculation.

    MEMORY: A computer can remember whatever we tell it to remember. Every piece ofinformation may be retained, in a computer memory as long as you desire it. Computerscan have very large memory.

    VERSATILITY: Even though the computer don’t have intelligence of their own, but theseare fairly versatile in performing arithmetic calculations, logic operations of comparison,moving data within the various sections of computer and input & output operations.Hence the same computer can be used to prepare marks sheets, do financial accountancy,share analysis etc.

    CHAPTER - 1

    SECTION A:COMPUTER FUNDAMENTALS

    COMPUTER FUNDAMENTALS 

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    ASSIMILATION EXERCISE

    1. Draw a single block diagram of a computer system.

    2. The function of a control unit is to ..........................

    3. RAM is a volatile / non-volatile memory.(Strike out whichever is not applicable).

    4. Dot matrix printers are of ....................... type whereas Inkjet and Laser Printers are of..................... type.

    (Impact/Non-Impact)

    5. DOS and Windows software are examples of ...................(System/Programming/Application Software)

    ACTIVITIES

    1. List the configuration of at least two of the computers with monitors, the advertisementof which you have most recently seen. Which one will you prefer for present work andwhy ?

    2. Name any ‘voice recognition software’ that you have heard about or are aware of.

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    CLASSIFICATION OF COMPUTERSComputers are usually classified as Digital, Analog and Hybrid. This classification is made

    on the basis of how they process the data.

    ANALOG COMPUTERThe analog computers are those which continuously measure physical magnitude throughtransducers viz. Pressure, Temperature, Voltage, Speed etc. The analog computers do notoperate directly on numbers & these computers are used for scientific engineering application.

    DIGITAL COMPUTERDigital computers operate directly on number expressed in binary numbering system. Theypossess certain characteristics and abilities that are particular to them. They can:

    Perform complex and repetitive calculations rapidly and accurately. Store large amount of data. Provide information in textual and graphical manner.

    HYBRID COMPUTER Combination of Analog & Digital Computers.

    TYPES OF COMPUTERSDepending upon the cost and performance capability of machines, the computers may also

    be classified as follows :

    1. Microcomputer2. Minicomputer3. Mainframe4. Supercomputer

    The above classification is, however, purely arbitrary.

    CHAPTER - 2

    CLASSIFICATION OF COMPUTERS

    COMPUTER FUNDAMENTALS 

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    MICROCOMPUTERA microcomputer is the smallest general purpose processing system that can execute programinstructions to perform a variety of tasks. They are further classified as Personal Computersand Home Computers. Typical of the PC category is the IBM-PC which has become the world

    standard for Personal Computers in the office.

    Below is the table that describes the configuration of the different versions of the IBM-PCfamily, that have been launched ever since 1981.

    PC PC-XT PC-AT

    RAM Initially 640 Kb 1 MB onwardslaunchedwith just64KB of RAM

    Hard Disk No Hard Disk One 20 MB Hard One to several highDrive Disk Capacity Hard Disk

    Drives

    Floppy Drives Typically 1 or 2 Typically 1 or 2 Typically 1 or more.

    Microprocessor Intel 8088 Intel 8088 Intel 80286 (The lower endATs); 80386 & 80486 (Themore powerful and modernATs) Pentium Super ATscapabilities.

    MINICOMPUTERSA minicomputer may be defined as a small general-purpose computer that is capable ofhandling large amount of data from multiple users working simultaneously .

    Today’s mini system are costlier and have large storage capacity speed of arithmetic operations,and ability to support a greater variety of faster-operating peripheral devices as compared toPCs. Further, while most PC systems remain oriented toward single users, mini systems areusually designed to simultaneously handle the processing needs of multiple users.

    MAINFRAMESA computer that is more powerful than a mini is called a mainframe computer. Mainframecomputers are capable of handling a large number of application programmers. Most of theapplication packages designed in the past by the larger software development firms havebeen written for mainframe computers. All popular high level programming languages can beused on available for mainframes, and their operating system programs offer very high level ofsophistication.

    SUPERCOMPUTERSSupercomputers are the most powerful and the most expensive computers so far made. Onlyfew of these computers are produced each year, because only few organizations need their

    COMPUTER FUNDAMENTALS 

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    processing capabilities. Supercomputers are a national resource. The calculations needed insome scientific research and development areas simply cannot do without Supercomputers.These computers are used in energy sector space exploration, medicine, industry, and othercritical areas.

    Cray Research (Brand Name: CRAY), and Control Data Corporation (Brand Name: CYBER)are two primary builders of supercomputers in America.

    In India, Centre for Development of Advanced Computing (C-DAC), Pune has developed theSupercomputer “PARAM”.

    COMPUTER FUNDAMENTALS 

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    E-mail :E-mail :

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    NUMBER SYSTEMNumber system plays an important role in the design, organisation and understanding of com-

    puters. Computers are based on a number system different from our decimal number system.If we have to represent numbers inside the computer using ‘ON-OFF’ on binary idea, we shallhave to manage with just two symbols - one for ON state and the other for OFF state. In fact,there are only two signals in the code used by computers; pulse and no pulse i.e. either thesystem is ‘ON’ or ‘OFF’. This system is called binary in which digit ‘1’ is meant for ‘pulse’ anddigit ‘0’ for no pulse.

    DECIMAL NUMBER SYSTEMIn the decimal system, there are ten digits and the system is based on ‘tens’. That is, each ofthe digits in a number has importance ten times more than the digit just right to it. For in-

    stance, 1985 means reading from the right.

    5 lot of 1 (units) = 058 lot of 10 (tens) = 809 lot of 100 (hundred) = 9001 lot of 1000 (thousand) = 1000 ____________________________________ 

    Total = 1985

    The decimal number system consists of ten basic symbols or digits, each symbol has its ownabsolute value and another place value. In the number 63, six has two values, i.e. one itsabsolute value which is 6 and another place value that is 60 or 6 tens. Number 10, which iscalled the base of decimal system is not a basic digit in this system. It is a result of the twodigits 1 and 0 placed in order after the last digit of number system, i.e. 9

    Thus we see that :10 = 1 ten + 0 unit63 = 6 tens + 3 units632 = 6 hundred + 3 tens + 2 units

    COMPUTER FUNDAMENTALS 

    CHAPTER - 3

    NUMBER SYSTEM

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    The position of the digit in base 10 system thus determines the magnitude of the numbersread.

      63 = 6 × 10 1 + 3 × 10 0

    632 = 6 × 10 2 + 3 × 10 1 + 2 × 10 0

    From the above, it is clear that the decimal number system has base 10.

    BINARY NUMBER SYSTEMIn binary system, there are only two digits and the entire system is based on counting onlytwo variables. Each of the digit in a number is twice the value of the digits on its right. Forinstance, the binary number 1111 means, reading from right to left.

    1 lot of 1 = 11 lot of 2 = 21 lot of 4 = 4

    1 lot of 8 = 8 ____________________ 

    TOTAL 15

    The important thing about the binary system is that it has a base of 2, i.e. there are only twodigits (0 and 1). Thus a number 10 in the binary system, as per definition of the generalnumber system is

    10 = 1 × 21  + 0 × 20

    The value of the position in the binary system varies as powers of two’s, giving units two, four,eights, sixteens etc. in comparison to units, tens, hundreds, thousands and ten thousands etc.in the decimal system.

    Conversion from Binary to Decimal :

    1010 = 1 × 23  + 0

     × 22  + 1 × 21  + 0 × 20

    = 8 + 0 + 2 + 0= 10 (in decimal)

    101010 = 1 × 25

     + 0 × 24

     + 1 × 23

      +  0 × 22

      + 1 × 21

      + 0 × 20

    = 32 + 0 + 8 + 0 + 2 + 0= 42

    Conversion from Decimal to Binary System :For this we have to successively divide the decimal number by two, until it is reduced to 0.When divided by two, there is a remainder of one, which becomes a binary digit 1. And, ifthere is no remainder, it becomes a binary 0.

    COMPUTER FUNDAMENTALS 

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    To convert the decimal number 15 to binary :

    15/2 = 7, remainder 17/2 = 3, remainder 1

    3/2 = 1, remainder 11/2 = 0, remainder 1

    So binary equivalent of 15 is = 1 1 1 1

    OCTAL NUMBER SYSTEMIn the octal number system, the base is 8, it will have digits from 0 to 7. Learning of octalsystem is necessary because microcomputers use this system for direct input/output opera-tions.

    Conversion from Octal to Decimal :(37)8

    = 3 × 81 + 7 × 80

    = 24 + 7= (31)

    10

    (.74)8

    = 7 × 8-1 + 4 × 8-2

    = 7 × 0.125 + 4 × 0.015625= 0.875 + 0.0625= (0.9375)

    10

    Conversion from Decimal to Octal :The octal system has the base 8. Hence, for conversion of the decimal number to octalsystem, the integral part is to be divided by 8 successively till the number is completely ex-hausted.To convert decimal 983 into its octal equivalent :

    8 7

    2

    7

    1

    98 3

    12 2

    15

    10

    8

    8

    8

    Thus, decimal 983 = octal 1727

    HEXADECIMAL NUMBER SYSTEM

    The big computer manufacturers like International Business Machine (IBM), Honeywell, Spectraand many other use the hexadecimal number system. The popular micro-processors likeINTEL 8080 and INTEL 8085 also use the hexadecimal system of numbers. The reason for

    the popularity of this number system is that it represents information in a brief form, as com-pared to the binary system.

    COMPUTER FUNDAMENTALS 

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    The hexadecimal system means a system based on 16 digits. The hexadecimal number sys-tem has a base of 16 digits to represent all numbers. The digits are 0,1,2,3,4,5,6,7,8,9, A, B,C, D, E and F. Hexadecimal numbers are strings of digits such as 8AF, 4CF7, EC58.

    An easy way to understand hexadecimal numbers is to visualize a hexadecimal milometer

    (odometer) of the type used in vehicles. Each wheel has 16 digits on its circumference. As itturns, it displays 0 through 9 as before. But then instead of resetting i.e. going back to zero, itdisplay A, B, C, D, E and F.

    The idea of reset and carry applies to hexadecimal odometer also. When a wheel turns fromF back to 0, it forces the next higher wheel to advance by 1. In other words, when a wheelruns out of hexadecimal digits, it resets to zero and carries the next wheel to 1.

    If used in a car, a hexadecimal milometer (odometer) would count as follows. When the car is

    new, it shows all 0’s :0000 (Zero)

    The next 9 kilometers produce readings of:

    0001 (One)

    0002 (Two)

    0003 (Three)

    0004 (Four)

    0005 (Five)

    0006 (Six)

    0007 (Seven)

    0008 (Eight)

    0009 (Nine)

    The next 6 kilometers give

    000A (Ten)

    000B (Eleven)

    000C (Twelve)

    000D (Thirteen)

    000E (Fourteen)000F (Fifteen)

    At this point, the least significant wheel has run out of digits. Therefore, the next kilometer ofdistance forces reset-and-carry to 0010 (Sixteen).

    The next 15 kilometers produce these readings :0011, 0012, 0013, 0014, 0015, 0016, 0017, 0018, 0019, 001A, 000B, 000C, 001D, 001E and001F. Again, the least significant wheel has run out of digits. Therefore, the next kilometerresults in reset-and-carry.

    COMPUTER FUNDAMENTALS 

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    Subsequent readings are 0021, 0022, 0023, 0024, 0025, 0026, 0027, 0028, 0029, 002A, 002B,002C, 002D, 002E, 002F.

    Each 15 kilometers advances the least significant wheel by 1. When this wheel runs out of

    hexadecimal digits, it resets and carries. And so on for the other wheels. For instance, if theodometer reading is 835F the next reading is 8360 and in the case of 5FFF, the next hexa-decimal number is 6000.

    COMPUTER FUNDAMENTALS 

    ASSIMILATION EXERCISE

    1. Computer system use octal system for direct input/output operations.

    2. Decimal equivalent of the binary 1111 is .............3. Binary equivalent of the decimal number 1542 will be .................

    4. Hexadecimal number system is used by manufacturer like ............... and .........................

    5. What are the uses of Hexadecimal system ?

    ACTIVITIES

    Ask from your instructor at the authorised training centre, the type of numbering system beingused for addressing the memory location of the microprocessors being used in Pentium III

    computers.

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    HARDWARE / SOFTWARE:

    DEFINITIONSA computer system can be viewed as a system of two components:

    1. COMPUTER HARDWARE2. COMPUTER SOFTWARE

    “Anything physical / tangible about a computer system is a part of the hardware of the system.Anything abstract / intangible about a computer system (i.e. which exists, but cannot be touchedor seen), is a part of the software of the system”.

    The above definition is better understood by drawing an analogy between a Computer Systemand the Stereo System. The Cassette Deck, Amplifier, Speakers, Cassettes etc. fall into thecategory of hardware of the Stereo System. However, the music recorded on the cassettes,which exists, but cannot be touched or seen, forms part of the software of the Stereo System.

    In a similar manner, all physical components of a computer system are part of the hardware ofthe system, whereas data and programs comprise the software of the computer system.

    The relationship that exists between hardware and software, is of Neither-Can-Do-Without-The-Other relationship.

    A computer system, with all hardware components in good working condition is of no usewithout software to run on it. Similarly even the latest and most sophisticated software wouldgather dust unless the owner has access to hardware to run it on.

    Computer hardware will run any software that has been designed to work by its rule.

    ARCHITECHTURE OF COMPUTERThe conventional discussion of the Computer System centres around the core system whichis made up of two parts:

    COMPUTER FUNDAMENTALS 

    CHAPTER - 4

    CONCEPTS OF HARDWARE & SOFTWARE

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    The first part is the Central Processing Unit (also known as CPU or the microprocessor).CPU is ‘Electrical Brain’ in computer system. It consists of two components:

    Control Unit: It controls all input and output to and from the computer.

    Arithmetic and Logic Unit (ALU): It actually performs the arithmetic and logicaloperations within the CPU.

    The second part is the Memory Unit, can be compared to a desk where all data and instructionsthat the computer is working on currently is kept.

    The following Block Diagram of Computer best represents the conventional discussion of acomputer system.

    C P UI N P U T

    D E V I C EO U T P U TD E V I C E

    M em ory( R A M / R O M )

    (Microprocessor)

    Let us elaborate Memory unit of computer. The memory of a computer is also referred to bysome of its internal or primary storage (external or secondary storage is discussed in latersection). This internal storage is of two types, namely, the RAM and the ROM.

    RAM (Random Access Memory):

    It is the storage location within the computer where all data and instructions required forcurrent working are stored. The significant feature of the RAM is that data can be read from it,as well as written onto it. It is a temporary or volatile memory. It means as soon as the power isswitched off, any information stored in the memory will be lost.

    ROM (Read Only Memory):It comes with programs already built into it. These are the programs the computer requires forits internal working. The significant feature of ROM is that data/programs can only be readfrom it. No data/programs can be written onto it.It is Non-Volatile, as it retains anything within it irrespective of the power being on or off.

    PROM (Programmable Read Only Memory):A variation of ROM is PROM. It can be programmed to record information using a facility.PROM is one time programmable. Once the chip has been programmed, the informationcannot be changed, i.e. the PROM becomes a ROM and the stored information can only beread.

    EPROM (Erasable Programmable Read Only Memory):As the name suggests information can be erased and the chip can be programmed to recorddifferent information using a special PROM PROGRAMMABLE facility. When an EPROM isused in the microcomputer, it behaves like a ROM.

    COMPUTER PERIPHERALS

    COMPUTER FUNDAMENTALS 

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    Users of a computer cannot communicate directly with CPU. Similarly the CPU cannot outputdata directly to the user of a computer. Such communication is done via devices which establisha workable interface between the computer and the outside world. These devices are referredto as peripherals .

    Peripheral devices can be one of the following three types: Input Devices Output Devices Secondary Storage Devices

    INPUT DEVICESInput devices are used to feed data and instructions to the computer, e.g. Keyboard, Mouse,Track ball, Light pen etc.

    KEYBOARDThe keyboard is a device that enables input to the computer. Its layout is very similar to that ofa type-writer. A typical computer keyboard includes Alphanumeric keys in the centre, Numerickeypad to the right, set of function keys, cursor movement keys and other special keys. Atypical PC Keyboard contains between 84 and 101 keys.

    MOUSEA mouse is a pointing device that is used to print to various objects on thecomputer screen. It has two or three buttons on the top and a ball on theunderside. The mouse is moved on a flat surface.

    Its movement causes the rotation of the ball. The ball on the underside is able to track thedirection of movement because of the friction between itself and the flat surface. Movementsof a mouse guide a “mouse pointer” (an arrowhead displayed on the screen) in the direction ofthe movement.

    MAGNETIC INK CHARACTER READER (MICR)MICR is an input device used to read characters printed using a special magnetic ink. Checkamounts written in magnetic ink are read by MICR. This ensures accurate data entry tocomputers.

    OPTICAL MARK READER (OMR)OMR is an input device used to read marks on a paper form. These preprinted forms aredesigned with boxes which can be marked in dark pencil or ink. OMR converts these marksinto electrical pulses which are transmitted to computer. OMR are used in objective tests,market surveys, population surveys, order forms etc.

    OPTICAL CHARACTER READER (OCR)OCR is an input device used to read any text either in handwritten or printed form. The text isscanned by OCR and converted to a machine readable form. This text can then be reformatted,stored and printed. OCR improves the accuracy of data entry. It is expensive and used insituations where large quantities of documents are to be entered in computer.

    COMPUTER FUNDAMENTALS 

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    LIGHT PENA light pen is similar to pen in size and shape and is used for pointing objects on screen. Itconsists of a light sensor (photodiode or phototransistor) and an amplifier. Light pen is brought

    near the screen for pointing to an object. During scanning when the cathode ray passes thelight pen tip, a signal is generated by light pen and is sent to computer. Computer can determinethe position of light pen on screen from this signal.

    JOYSTICKIt is most commonly used games controller. It consists of a box (the base), a stick coming outof it (the controller) and one or more buttons. The stick can be moved in different directions tocause the movement of objects on screen. The button is usually used to fire guns, missiles ingames (hence called fire button) or for some other purposes in other programs e.g. menuselection. Two types of joystick are available analog and digital. The analog joysticks are morepopular. They use two potentiometers, controlled by X and Y movements of the stick.

    TRACK BALLA track ball consists of a ball which moves freely in all directions. It rests on rollers or wheels,two of them are placed at right angles to each other and used in the measurement. When theball is rotated, the rollers also rotate. The movement of roller is measured by using potentiometeror a rotating disk which acts as a digital sensor. A track ball can be spinned in any onedirection forever and it will continue to produce result.

    OUTPUT DEVICESOutput devices are used to get results from the computer e.g. Monitor, Printer and Plotter.

    MONITORMonitor enables visual output (text and graphic) from the computer. It is very much like TVscreen. It acts as a window which displays a part of the total information. The commonlyavailable monitors can display upto 25 lines and each line can display upto 80 characters.Different types of monitors are used depending upon the type of display card used in thesystem. The few examples are:

    Display type Resolution supported Color supported

    Color Graphics Array (CGA) 320 x 200 4640 x 200 2

    Enhanced Graphics Array (EGA) CGA Resolutions640 x 350 16

    Video Graphics Array (VGA) CGA & EGA320 x 200 256640 x 480 16

    Super VGA CGA, EGA & VGA640 x 480, 800 x 600 256, 32K

    1024 x 768 64K1280 x 1024 16 Millions

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    The size of dot (also called as pixel), the pixel density i.e. total pixels available on screen andcolours available decide the quality (resolution) of output text or graphics.

    PRINTER

    Printer is a commonly used output device. The printer allows a hard copy of the output whichcan be stored for later reference. There are many kinds of printers available in market.

    Two broad categories of printers are :

    1. Impact Printers: In these printers image is created by pressing a typeface against aninked ribbon which makes mark on the paper. (Physical contact)

    2. Non-Impact Printers: In these printers image is created without any direct contact withthe paper.

    Dot Matrix PrintersThese are most popular impact printers. Dot Matrix printers can print on paper 80 or 132characters in width. They print character by character and their speed is measured in characterper second (cps). Speed is high, most of them are capable of printing graphics, but they sufferfrom a print quality that is poor compared to that of Daisy Wheel Printers.

    These printers utilize an array of (7 × 9 or 24 × 9) pins that forms a letters made up of dot byhitting out the appropriate combination of pins on paper through the inked ribbon.Most Dot Matrix printers have NLQ (near letter quality) facility i.e. they smooth the edges ofthe fonts resulting in much more clearer output in this mode, but at slower speeds. Apart fromthis, these printers can be made to print in compressed mode. These printers can offer upto

    150dpi.

    Daisy Wheel PrintersThese are impact printers, where each character is mounted on the edge of a each spoke ofa wheel. The wheel spins at high speeds and the required character is struck by a hammer.Print quality is typically very good (Letter Quality) but speed is slow as compared to otherimpact printers.

    Ink Jet PrinterThis is non-impact printer which spreads ink on the paper which is deposited as small dots.

    As the ink in controlled by a magnetic field the quality of the output is very good Ink Jetprinters noiseless and extremely fast. They are capable of printing an entire page in a second.These printers can offer upto 720dpi.

    Laser PrinterThis is a non-impact printer. Laser printers are silent. They produce high quality output andtypically used for publishing. These printers output a page at a time and their speeds aremeasured in pager per minute (ppm).Laser printers use a light beam to form images on the paper using a toner ink as the medium.The light beam strikes parts of a drum surface to form an image. These parts of the drum

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    surface which are exposed to the light beam becomes electrically charged. Only theseelectrically charged areas attract the toner ink particles. These toner particles are then depositedon paper and permanently fixed to the paper using heat or pressure. These printers can offerupto 1200dpi.

    PLOTTERA plotter is an output device used to produce good quality drawings and graphs. They are oftwo types :

    Drum plotter Flat bed plotter

    Upto 4 or 8 pens are used in plotters to generate coloured drawings.

    A drum plotter consists of a drum and a pen mounted on a carriage. The drum can rotate inclockwise or anti-clockwise direction. The pen also can be raised or lowered. The paper ismounted on plotting surface. The movements of carriage are controlled by the computer togenerate drawings. A disadvantage of this plotter is the limited paper size that can be used.This plotter is also called as X-Y plotter.

    SECONDARY STORAGE DEVICESPrimary memory (RAM) of the computer is of volatile nature. Therefore, secondary memory isrequired. Some of the secondary storage devices are:

    FLOPPY DISK

    It is flexible plastic disk coated with metallic oxide and kept in protective plastic jacket with aopening, to allow access to the magnetic medium. There are two sizes of floppy disks; the5.25 inch floppy and the 3.5 inch floppy. Storage capacities for these vary from 360 Kb to 1.44Mb. Information is written into or read from the floppy along concentric circles called Trackswhich are further divided into sectors. Floppy disks are comparatively cheaper and can betaken from one place to another. It is a direct access device.

    HARD DISKHard Disks are where most of the PC user’s data resides. The whole system consists of twoparts the hard drive and Interface. Hard drive are disks with rigid platters (Floppy Disk like

    surfaces, every surface requires a Read/Write heads on each side) made of an aluminumalloy which are magnetically coated stacked inside an air filtered enclosure. Because of manyfactors, like faster speed of rotation and higher recording density (storage capacity, hard disksneed to be carefully protected from dust and other contamination. So hard disks are sealedinside the disk drive and are not removable like floppy disk.The hard disk is also Direct Access Device.

    MAGNETIC TAPEMagnetic Tape provides facilities for reading, storing, and erasing the information. It is widelyused when large amount of data is to be stored sequentially. It is made of plastic that is coatedon one side with metallic oxide. Information is recorded on the coated side of the tape. These

    are mostly used for keeping a Backup of data.

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    Advantages :1. Tapes are extremely compact in design.2. These cost much less and are reusable.

    Disadvantages :1. When the tape tears, some data will always be lost.2. Magnetic tapes provide serial access i.e. when any information is required one will

    have to run the tape from initial position to that point where it is recorded.

    OTHER MODERN INPUT/OUTPUT DEVICES

    VOICE - INPUTA voice - input device usually a microphone accepts spoken input. The wave form created byspoken input is analyzed, and patterns are extracted and matched against pre-stored patternsto identify the input. Once identified, the appropriate coding is generated for handling withinthe computer.Before a voice-input device can be used, it must first be provided with a vocabulary. Thewords and phrases the device is to recognize are “spoken” to the voice-input device with thevoice-input device operating in a so called “training mode”. In this mode, the sound patters arecreated and stored for future matching. A voice-input device may be trained to recognize boththe voice of one or more operators and a given vocabulary for each operator, in which caseunwanted inputs or unauthorized speakers are rejected.

    OPTICAL DISKS

    A very exciting development in disk storage is that of CD-ROM (Compact Disk-Read OnlyMemory). CD-ROM is able to provide enormous storage capacity in comparison to otherbacking storage medium like floppy/hard disks. A single silvery plastic disk, or “platter” as it ismore commonly called, one more than 4.72 inches in diameter, is able to store up to 600 Mbof data. This is the equivalent of 1000 or more floppies, or approximately 20,000 pages of text.CD-ROM uses the same metal-coated plastic platters as are used for digital audio recordings.The digital information is burned on by a laser at the time of manufacture. The surface iscoated with a thin film of aluminum. As the name suggests, information stored in a CD-ROMcan only be read. It cannot be modified in anyway.

    CLASSIFICATION OF SOFTWARE

    Computer Software can be divided as : System Software Programming Languages Application Software

    1. SYSTEM SOFTWARESystem Software is software that enhances the inherent capabilities of the computer.Examples of how it does this include :

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    By providing an easy interface between the computer and user. By controlling the activities of the computer, and its interaction with peripherals

    connected to it. These utility services are offered by the operating system are part ofthe system software.

    2. PROGRAMMING LANGUAGESProgram is nothing but a set of successive instructions to achieve the results.Programming Language compilers are specialized translator (compilers are the programswhich translate high level language into low level language). i.e. Programming Languagecompilers translate users instructions into machine readable instructions e.g. ‘C’, COBOL,PASCAL, FORTRAN etc.

    3. APPLICATION SOFTWAREApplication Software is software that is directly application - oriented. Application softwarepackages are built to confirm to specific needs of users (for example to enable use ofcomputer for Financial Accounting, Payroll Accounting, Inventory Control, etc.) The bulkof commercially developed software today falls into this category. Typical applicationsoftware packages provide an extremely “user-friendly” interface.

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    the boot sector. All hard disks have a partition table. Corruption of this table results in totalinaccessibility of the hard disk. The first logical sector of any disk formatted under DOS iscalled the boot sector.

    The boot sector consists of executable code and data. The data area contains importantinformation of about disk characteristics. In a disk having a boot sector virus, the first instructionin the boot sector is changed so that it points to the area where the virus is located. Hencewhen the computer is booted with a boot sector virus, the virus gets into the system beforeDOS. The File Allocation Table of FAT is an index to every assignable space on the disk. FATis the prime target of many destructive virus, as when this area of a disk is corrupted, DOScannot retrieve any data from the disk.

    Boot sector viruses can remain active at all times. They can survive warm boots and contaminateuninfected startup disk whenever systems are restarted midstream. Boot sector viruses can

    change the directory listing to show correct files sizes, when infact file sizes have been changedas a result of the addition of viral code.

    At some appropriate time when these viruses are triggered they can interrupt normal processingand some of them even destroy data on the disk. Boot sector viruses are also called memoryresident infectors as they remain loaded and active in the computer’s memory when thecomputer is being run. The boot sector/partition table viruses, one generally encounters areAlameda virus, Golden Gate virus, Brain virus, Italian virus, Joshi virus, Stoned virus etc.

    FILE VIRUSESThese viruses do not infect the boot sector partition table but they infect the executable files(i.e. EXE and COM extension files) and sometimes even overlay files (i.e. OV/OVR extension).

    Viruses do not infect data files as these are not executed and changes in them are moreeasily detected. Suppose the COMMAND.COM file is infected by a virus. All users request areinterpreted by this file, and hence if the user gives a simple command like DIR, the virusinfects other command files on the disk and then allows execution of the DIR command. Eventhough the execution time is 16:59:53, while others like the Jerusalem virus slows down thecomputer, and on any Friday which happens to be the 13th, all executable files that you attemptto run are deleted.

    SYMPTOMS OF A VIRUS :1. Frequent hanging of the system.2. RAM (main memory) gets decreased, causing problems when executing large programs.3. Increase in the file size of the infected files.4. Partial destruction of FAT causes loss of data from files.5. Decrease in the Speed of the System.6. Strange messages or strange patterns appear on the screen.

    METHODS OF ELIMINATING VIRUSESIt is generally known that if you format your disk any viruses present on it will be automatically

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    destroyed. But this is a panic step. You should do this only as a last resort, as it will destroy alldata and programs on that disk. Also sometime a hardware or a software problem is notidentified and one presumes it has to be some kind of viral attack. If you are not sure, it maybe better to call in a reliable and knowledgeable person, to diagnose your problem. All the

    same use of the following steps may be of help:-

    1. Isolate that computerAs we have already discussed if infected disks are used the virus infection spreads.Hence one of the simplest ways of stopping this is to stop using that computer andfloppies till you have eliminated the virus.

    2. Backup data and Anti Viral UtilitiesUse fresh disks and backup all your data files. Do not back up files with COM and EXEextensions as they may be infected with the virus. Also make sure you have clean copiesof your Anti Virus Software, as while eliminating the virus, you might contaminate your

    anti virus utilities.3. Use proper Anti Virus SoftwareOne of the most popular utilities to detect and remove viruses is SCAN and CLEAN ofMcAfee Associates. These utilities are regularly updated and hence if you have a copy ofthe latest version, it would in all probability be in a position to detect and eliminate thevirus.

    4. Format only as a last resortAs mentioned earlier if other methods fail, then you have this last option open to you, if itis a boot sector virus, apart from formatting you may try transferring the system (DOSSYS program) if the virus is in the partition table, a low level format of the hard disk couldbe done.

    5. Copy back your filesOnce you have cleared the virus, copy back your system files, program files and datafiles. Keep a track of the size of files, as it is a sure clue to the presence of file viruses.

    6. Backup your Data regularlyAs final precaution, it is advisable to make regular backups of your data files using DOSbackup programs.

    But the best cure is precaution. Hence if you follow some of the steps outlined below you mayrun a smaller risk of infection than you normally do. Here are some precautions :

    Make all your important disks which contain your programs written protected. Do not boot with a floppy (without checking for virus) which may have been used on other

    computers, that is sure to commit suicide. Do not use pirated software, specially computer games, as many of them contain

    viruses. Make sure you have backups of all your important software, and make regular backup

    of your data file.

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    ASSIMILATION EXERCISE

    State True or False:

    1. Computer virus cannot replicate itself.

    2. You can remove virus with any of the antivirus software.

    3. If your computer has virus, just format it.

    4. Viruses only affect the executable files like files with .EXE and .COM extensions

    5. Data files are not affected by virus.

    6. Y2K is a virus problem.

    7. Scan and Clean McAfee Associates is one of the most popular anti-virus utilities.

    ACTIVITIES

    Pick up one of the latest computer magazine from the library of your Authorised TrainingCentre and identify the latest virus doing the rounds affecting computer.

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    MS DOS

    COMPETENCY OBJECTIVES

    The objective of this section is to introduce the students to the basic principles of the operatingsystrems and the salient features of the Microsoft Disk Operating System. Both internaland external commands are discussed in detail with stress on syntax and various switchoptions available. At the end of the course, a student should be able to :-

    Appreciate the requirement of an Operating System for a computer/computernetwork.

    Understand salient features of MS-DOS. Carry out Files & Directory Management. Apply Internal and External DOS commands.

    Manage the day-to-day office keeping functions with the help of computers.

    “Computers in the future may weigh no more than 1.5 tons.”—Popular 

     Mechanics, forecasting the relentless march of science, 1949.

     But DOS has changed all that. It has brought computers in lap not 

    weighing more than a newly born baby.

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    OPERATING SYSTEMAn Operating System (abbreviated as OS) is a computer user’s silent partner. It is a piece of

    systems software that resides within the memory of the computer at all points of time. Formost computer systems, the OS is the interface between the Computer and its users.

    Thus the purpose of operating system is to manage and control the resources of the computerhardware in such a way that they will work together to perform useful work for you. A computercan’t work without operating system. It co-ordinates the flow of information from the computerto the user and vice versa.

    Operating system isolate the user of the computer from the technicalities of the actual workingof the computer. The user of the computer then has to only concentrate on providing instructions

    for the specific application to be performed. The nitty-gritty of how the instructions will actuallybe executed are handled by the operating system.

    Operating system is responsible for : Memory Management CPU Management DISK Management I/O Device Management User-Interface

    Memory ManagementMemory is the term always referred to Random Access Memory (RAM) - the main memory ofyour system. When you run the program, OS retrieves it from the disk and loads it into itsmemory. But before it is loaded, the OS must check whether memory is available for it or not,and if available, it allocates it to your job. Once the execution of the job is over the job shouldbe removed from memory and this freed memory allocated to another job.

    CPU ManagementIt is the assignment of the CPU that allows processor to accomplish job assigned to it. Thatassignment is a complex problem handled by OS. The function of assigning jobs for processingis also called as job scheduling. The OS helps the CPU to schedule its activities.

    MS - DOS 

    CHAPTER - 6

    SECTION - BMS - DOS OPERATING SYSTEM

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    Disk ManagementThe OS helps you to store files and retrieve files whenever, required by you.

    Input / Output Management

    All peripheral devices communicate with the computer for getting the job and getting it done,which is again monitored by the OS.

    User - InterfaceAs computer can understand the language of only 0’s and 1’s, OS as command interpreterhelps in bridging the gap between machine level language and human language. The mostpopular operating system for microcomputer is MS-DOS. (Microsoft Disk Operating Systemwhich is a current standard for IBM-PC and its clones).

    LOADING THE OPERATING SYSTEM

    When computer is switched on, a sequence of activities takes place before the user can startinteracting with the computer.

    As a first step, the processor starts executing the ROM-BIOS instructions which are inthe ROM portion of the memory. ROM-BIOS instructions are permanently stored in ROMand activated each time the power is switched on.

    The first of the ROM-BIOS instructions is the start-up-routine. These instructions test tosee if the computer is in good working condition. This activity is known as Power-on-self-test (POST). POST checks all areas of RAM memory for defects and also look atthe connections to the various peripheral devices.

    The next activity of ROM-BIOS instructions is the “Bootstrap” process. Booting meansloading the operating system from the disk into the memory.

    Bootstrap process involves a number of activities.

    First ROM-BIOS attempts to read a boot record (every disk formatted using FORMAT/Scommand, contains boot area in its 1st sector). In order to load the boot record, the ROM-BIOS searches for a disk first in ‘A’ drive. If it cannot find a boot record in a ‘A’ drive, itattempts to access a boot record from a hard disk (‘C’ drive), if it is connected to the

    computer. If a boot record is not found on either of these drives, then an error messageappears indicating that the boot record is not found.

    Bringing in DOS : If ROM-BIOS is able to read a boot record, it hands over control to theshort program on the boot record. These instructions now access two files from the diskcalled the IBMBIO.COM and IBMDOS.COM (DOS is made up of three files which arethe IBMBIO.COM, IBMDOS.COM and COMMAND.COM. Of these, the IBMBIO.COMand IBMDOS.COM are hidden from the directory of the disk. These files are also referredto as IO.SYS and MSDOS.SYS respectively.

    After these two files of DOS are loaded into the memory, the computer next searches for

    the file CONFIG.SYS and if present (the presence of this file is optional), loads it. TheCONFIG.SYS file allows the user to specify certain parameters to DOS.

    MS - DOS 

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    The last step in the boot strap process is the loading of the COMMAND.COM file, once itis loaded the computer is under the control of the operating system.

    At the end of the sequence of activities DOS searches for a file AUTOEXEC.BAT and if

    found automatically executes the commands that are included in this batch file otherwiseDOS prompt A:> or C:> appears on the screen depending on whether DOS was loadedfrom the A drive or the C drive.

    BATCH FILESFiles with an extension BAT are called batch files. Assume that the sequence of DOS commandshave to be given again and again, then instead of entering these DOS commands individuallyat the DOS prompt and waiting for each to get executed, you can save this sequence ofcommands in a file with an extension BAT, say SAMPLE.BAT. If now the command entered is,

    A>SAMPLE

    DOS executes the commands in the file SAMPLE.BAT one after the other.

    When all batch files are executed by entering the name of the file as a command, the batchfile with the name Autoexec.bat is treated by DOS in a special manner.

    Each time when computer is booted DOS searches for this file in the root directory and iffound, automatically executes the commands that are included in this batch file.

    MS - DOS 

    ASSIMILATION EXERCISE

    1. Describe the boot up sequence of a MS-DOS compatible computer.

    2. What are the batch files and what is their significance.

    3. What is the role of operating system.

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    DISK ORGANISATION

    FILES AND DIRECTORIESYou are already aware that all the work you do on your computer has to be stored in files. Likethe files put away in an office cabinet, you can stack the whole lot of them in one area ororganize them into separate racks or shelves.

    If you look at the first option where the files are stacked into one area, finding a specific filefrom a stack of files, at a glance is very difficult.

    Therefore, to facilitate your information retrieval, you will stack them into different shelves andracks, possibly based on their subject contents. Further you may even arrange them in thealphabetical order of their labels.

    Likewise, you can either place all your files into the hard disk’s or on the floppy disk’s mainstorage area. This area is termed as the Root Directory .

    But stacking all your files on the root directory will be as inefficient as stacking your paperdocument files into the same area in your cabinet. Just as you have racks or shelves in yourcabinet to store files of the same category, you can create subdirectories  on your hard disk orfloppy disk to store files of a particular category into one specific area.

    The root directory is identified by the drive letter (A: or C: or F: followed by a ‘\’ (backslash).Thus when you see c:\> on your monitor, it represents the root directory on the C drive.

    Subdirectories are generally given names that indicate the kind of files they store. For instance,the Accounts related files are put into a subdirectory called ACCOUNTS, the personal datafiles are put into another subdirectory called PERSONAL and so on.

    A subdirectory may, in turn, contain other files and subdirectories. The PERSONAL subdirectory

    can be further subdivided into two or more subdirectories - BANDRA and OPERA HOUSE.Each of the two subdirectories have their own files.

    R O O T

    P E R S O N A L

    B A N D R A O P E R A H O U S E

    A C C O U N T S

    This whole structure - the root directory containing subdirectories and files is termed as theDirectory Tree  of your hard disk or floppy disk.

    MS - DOS 

    CHAPTER - 7

    DISK ORGANISATION

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    FILEA file can be looked upon as folder in filing cabinet containing information on a particular topic.Just as each folder has a label, each file has a name. A filename has two parts separated bya period (.). Primary Name Secondary Name or Extension

    Rules for filename : The primary name can be from 1 to 8 characters long, while the secondary name or

    extension can contain 1 to 3 characters.

    Filename can include any of the following characters

    A-Z or a-z, 0-9, $ & # ! % ‘ () - {} _ / \ 

    Files with secondary name or extensions like EXE, COM, BAT are called executable files asthey are in the form that can be understood by the computer.

    Some of the valid filenames are

    Sales.dat, Project.prg, Person.dbf etc.

    DIRECTORYDirectory organises your common programs and files into related groups, hence locatingwhat you need becomes relatively easy.

    Every DOS directory must have a name which can be maximum, eight characters long with 1to 3 character extension preceded by period. But normally the extension is not used withdirectory character names as it then tends to be difficult to distinguish between files anddirectories.

    Some of the valid directory names are :

    MAHESH, REKHA, LETTERS, NOTES etc.

    WILDCARDS CHARACTERS

    * The asterisk stands for one or more characters in a filename or extension. Fore.g. *.com represents files having any primary name but with secondary namecom. Similarly Pay.* represents files having any extension but with primary namepay, while Q*.* represents files with primary names beginning with letter Q andany extension.

    ? The question mark (?) is used within filename to represent any one character. Fore.g. A??.* represents files with primary name beginning with character A andhaving 2 or less characters next and any extension. B??T.BAK represents fileswith primary name beginning with B, then any two characters, then character Tand extension BAK.

    MS - DOS 

    ASSIMILATION EXERCISE

    1. How are the files and directories organised.

    2. What do you mean by file allocation table (FAT).

    3. What rules should be followed for naming a file in DOS ?

    4. Write a simple config.sys and autoexec.bat file for your system.

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    TYPES OF DOS COMMANDSDOS commands are of two types

    Internal Commands External Commands

    INTERNAL COMMANDSThese are the part of the command processor i.e. command.com which is loaded in thememory. These commands can be given at any time. Required instructions are already storedin the main memory, and these command do not require special file on the disk to run them.

    EXTERNAL COMMANDSThose commands which are not included in Command Processor but exists as external files

    are known as External Commands. When we give the external commands DOS requiresthese instructions stored in a file.

    When DOS is loaded into the memory of the computer [the RAM], it displays a

    C> _ 

    on the screen. This symbol is called the DOS COMMAND PROMPT. The DOS commandprompt is DOS’s way of indicating that it is ready to take in commands/instructions, and performtasks for you.

    INTERNAL COMMANDS

    CLS

    Syntax : CLS This command will clear the screen and display the DOS command prompt onthe left hand corner of the screen.

    CHAPTER - 8

    DOS COMMANDS

    MS - DOS 

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    DIR

    Syntax : DIR [drive:] [path] [filename] [/P] [/W][/A[ [:] attributes] ] [/O[[:]sortorder]] [/S] [/B] [/L] [/C]

    The DIR command will produce a list of files that exist on a disk. When thecommand DIR is issued, DOS displays 5 columns of information.

    COLUMN 1 : Primary NameCOLUMN 2 : ExtensionCOLUMN 3 : The physical size of the file in terms of the bytes that it

    occupies on the disk.COLUMN 4 : The Date when the file was last referenced and modified.COLUMN 5 : The Time when the file was last referenced and modified.

    Parameters [drive:][path]Specifies the drive and directory for which you want to see a listing.[filename]Specifies a particular file or group of files for which you want to see a listing.

    Switches  /P

    The /P option of the DIR command will produce a page-wise list of file details,i.e., when the screen fills up with the filenames, the DIR command will pause itsoperation and display a message “Press any key to continue.” On the last line ofthe screen, allowing the contents to be examined.

    The DIR command resumes its operations after any key is pressed.

     /W

    The /W option of the DIR command will produce a widthwise listing of files,allowing many more filenames to be displayed on a single screen than the normal

    DIR>

    The /W option suppresses the display of all columns other than the primaryname and extension columns.

     /A[[:]attributes]

    Displays only the names of those directories and files with the attributes youspecify. The following list describes each of the values you can use for attributes.

    MS - DOS 

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    H Hidden files -H Files that are not hiddenS System files -S Files other than system filesD Directories -D Files only (not directories)A Files ready for archiving (backup) -A Files that have not changed since

    the last backupR Read only files -R Files that are not read-only

     /O [[:]sortorder]

    Controls the order in which DIR sorts and displays directory names and filenames.If you omit this switch, DIR displays the names in the order in which they occurin the directory.

    N In alphabetical order by name -N In reverse alphabetic order by

    name.E In alphabetic order by extension. -E In reverse alphabetic order byextension.

    D By date and time, earliest first. -D By date and time, earliest first.S By size, smallest first. -S By size, largest first.G With directories grouped before files. -G With directories grouped after

    files. /B Lists each directory name or filename, one per line. /L Displays unsorted directory names and filenames in lowercase. /S Lists every occurrence, in the specified directory and all subdirectories, of

    the specified filename.

    RENAME (REN)

    Syntax : REN [drive:] [path] filename1 filename 2

    Parameters [drive:][path] filename1 : Specifies the location and name of the file or set of files you want to rename.Filename 2 : Specifies new name for the file.

    To rename a filename report.96 to memo.96 type the following command:

    REN REPORT.96 MEMO.96

    CHDIR (CD)Changes the current directory.

    Syntax : CD [drive:][path]

    Parameters 

    [drive:][path]

    MS - DOS 

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    Specifies the drive (if other than the current drive) and directory to which youwant to change.

    To change from subdirectory to the parent directory type CD..

    To return to the root directory from any directory type CD\ 

    MKDIR (MD)

    Creates a directory. You can use the MKDIR or MD command to create amultilevel directory structure.

    Syntax : MKDIR [drive:] path OR MD [drive:]path

    Parameters[drive:]path

    Specifies the drive on which you want to create the new directory. Path specifiesthe name and location of the new directory. The maximum length of any singlepath from the root directory to the new directory is 63 characters, includingbackslashes (\).

    Suppose you want to create a directory on the disk in the current drive to storestudents related files, type the following command :

    MD STUDENT

    RMDIRRemoves a directory. But while removing the directory it should be completelyempty i.e. it should not contain any subdirectory or file in it. Also directory can beremoved only from its parent directory.

    Syntax : RMDIR [drive:]path OR RD [drive:]path

    Parameter [drive:]pathSpecifies the location and the name of the directory you want to delete.

    To remove a directory exam which is a subdirectory of student type the command:

    RD\STUDENT\EXAM

    PATHIndicates which directories MS-DOS should search for executable files.

    Syntax : PATH [[drive:]path[;…]]

    To display the current search path, type :

    PATH

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    Parameters [drive:]pathSpecifies a drive, directory and any other subdirectories to search. If you enterthe PATH command with a semicolon clears all search-path settings and specifies

    that MS-DOS is to search only the current directory.

    The maximum length of the PATH command is 127 characters. To specify morethan one path for MS-DOS to search, separate entries with a semicolon (;).

    By using the PATH command in your AUTOEXEC.BAT, you can set for all theSubdirectories you require for work on DOS. Doing so reduces the time taken tosearch for files.

    TYPE

    Displays the contents of a text file.

    Syntax : TYPE [drive:][path]filename

    Parameter [drive:][path]filenameSpecifies the location and name of the file that you want to view.

    To see the contents of the text file report.txt type :

     TYPE REPORT.TXT

    DEL (ERASE)Deletes the files you specify.

    Syntax : DEL [drive:][path]filename [/P]ERASE [drive:][path]filename [/P]

    Parameter [drive:][path]filenameSpecifies the location and name of the file or set of files you want to delete.

    Switch  /P prompts you for confirmation before deleting the specified file.

    If you use the /P switch, it displays the name of a file and prompts you with amessage in the following format :

    Delete (Y/N)?

    Press Y to confirm the deletion N to cancel the deletion.

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    You can also use wildcard’s to delete more than one file at a time.DEL *.*

    DOS displays the following message :

    All files in directory will be deleted ! Are you sure (Y/N)?

    VOLDisplays the disk volume label and serial number, if the disk has them.

    Syntax : VOL [drive:]

    Parameters [drive:]Specifies the drive that contains the disk for which you want to display the volume

    label and serial number.

    COPYCopies one or more files to the location you specify. This command can also beused to combine files.

    Syntax : COPY

    Parameters

    Specifies the location and name of a file or set of files from which you want tocopy.

    Specifies the location and name of a file or set of files to which you want to copy.

    Switches  /Y

    Indicates that you want COPY to replace existing file(s) without prompting youfor combination.

     /VVerifies that new files are written correctly.

    If you do not specify a destination file, MS-DOS creates a copy with the samename, creation date, and creation time as the original file, placing the new copyin the current directory on the current drive. If the source file is on the currentdrive and in the current directory and you do not specify a different drive ordirectory for the destination file, the COPY command stops and MS-DOS displaysthe following error message :

    File cannot be copied onto itself.0 File(s) copied

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    Combination files with the COPY command :If you specify more than one source, separating entries with a plus sign (+),COPY combines the files, creating a single file.

    If the name of the destination file is the same as the name of one of the filesbeing copied (except the first file), the original contents of the destination file arelost. When this happens, COPY displays the following message :

    Contents of destination lost before copy

    For e.g.COPY REPORT.DOC EXAM.DOC

    COPY MAR97.RPT + APR97.RPT + MAY97.RPT REPORT

    EXTERNAL COMMANDS

    FORMATFormat a disk for use with MS-DOS. The FORMAT command creates a new rootdirectory and file allocation table for the disk. It also checks for bad areas on thedisk, and it deletes all data on the disk. In order to use new disk for MS-DOS, youmust first use this command to format the disk.

    Syntax : FORMAT drive: [/V[:label]] [/Q] [/U] [/F:size][/BI/S] [/C]

    Parameter Drive :Specifies the drive containing the disk you want to format.

    Switches  /V:label Specifies the volume label /Q Specifies a quick format of a disk /U Specifies an unconditional format of a disk /S Copies the operating system files

    Do not format a floppy disk at a size higher than it was designed for. For example,do not format a 360K floppy disk at 1.2 MB.After formatting a floppy disk, FORMAT displays the following message :

    Volume label (11 characters, Enter for none)?

    The volume label can be maximum of 11 characters (including spaces). If youdo not want your disk to have a volume label, press ENTER.

    When you use the FORMAT command to format a hard disk, MS-DOS displays

    a message similar to the following before attempting to format the hard disk:

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    WARNING, ALL DATA ON NON-REMOVABLE DISK DRIVE x: WILL BE LOST!

    Proceed with Format (Y/N)?

    To format the hard disk, press Y; If you do not want to format the disk, press N.To format a new floppy disk in drive A using the default size, type the followingcommand

    FORMAT A:

    To perform a quick format on a previously formatted disk in drive A, type thefollowing command

    FORMAT A:/Q

    To format a floppy disk in drive A, completely deleting all data on the disk, typethe following command:

    FORMAT A:/U

    DISKCOPYCopies the entire contents of one floppy disk to another floppy disk. The Diskcopycommand can be used to get exact replica of the source. Diskcopy writes overthe existing contents of the destination disk as it copies the new information toit.

    This command determines the number of sides to copy based on the sourcedrive and disk.

    Syntax : DISKCOPY [drive1:[drive2:]] [/1] [/V] [/M]

    Parameters drive 1 : Specifies the drive containing the source disk.drive 2 : Specifies the drive containing the destination disk.

    The Diskcopy command works only with floppy disks. You cannot use Diskcopywith a hard disk or a network drive.If you specify a hard disk drive for drive1 or drive 2, DISKCOPY displays thefollowing error message :

    Invalid drive specificationSpecified drive doesn’t existOr is non-removable

    The DISKCOPY command prompts you to insert the source and destinationdisks and waits for you to press any key before continuing.

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    If your system has only one floppy disk drive, drive A, and you want to comparetwo disks, type the following command :

    DISKCOMP A: A:DISKCOMP prompts you to insert each disk, as required.

    TREEGraphically displays the structure of a directory.

    Syntax : TREE [drive:][path][/F][/A]

    Parameters Drive:Specifies the drive that contains the disk for which you want to display the directorystructure.

    Switches /F Displays the names of the files in each directory. /A Specifies that TREE command has to use text characters instead

    of graphic characters to show the lines linking subdirectories.

    To display the names of all the subdirectories on the disk in your current drive,type the following command :

    TREE/ 

    To display, one screen at a time, the files in all the directories on drive C, typethe following command :

    TREE C:\ /F | MORE

    To print the same list that the previous example displayed, type the followingcommand:

    TREE C:\ /F > PRN

    DELTREEDeletes a directory and all the files and subdirectories that are in it.

    Syntax : DELTREE [/Y] [drive:] path [[drive:]path[…]]

    Parameter Drive:pathSpecifies the name of the directory you want to delete. The DELTREE commandwill delete all the files contained in the directory you specify, as well as allsubdirectories and files in the subdirectories subordinate to this directory. Youcan specify more than one directory.

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    If you omit destination, the XCOPY command copies the files to the currentdirectory.

    If destination does not contain an existing directory and doesn’t end with a

    backslash (\), XCOPY prompts you with a message in the following format:Does destination specify a filenameOr directory name on the target (F=file, D=directory)?

    Press F if you want the file(s) to be copied to a file. Press D if you want thefile(s) to be copied to a directory.

    Xcopy does not copy hidden and system files.

    XCOPY vs. DISKCOPY

    If you have a disk that contain files in subdirectories and you want to copy it to a disk thathas a different format, you should use the XCOPY command instead of DISKCOPY.Since the DISKCOPY command copies disks track by track, it requires that your sourceand destination disks have the same format. XCOPY has no such requirement. In general,use XCOPY unless you need a complete disk image copy. However, XCOPY will notcopy hidden or system files such as IO.SYS and MSDOS.SYS. Therefore, use DISKCOPYto make copies of system disks.

    The following example copies all the files and subdirectories (including any emptysubdirectories) from the disk in drive A to the disk in drive B:

    XCOPY A: B: /S/E

    ATTRIBDisplays or changes file attributes.This command displays, sets or removes the Read-only, Archive, System andHidden attributes assigned to files or directories.

    Syntax : ATTRIB [+R|-R] [+A|-A] [+S|-S] [+H|-H] [[drive:][path]filename] [/S]

    To display all attributes of all files in the current directory, use the following

    syntax:ATTRIB

    Parameter [drive:][path]filenameSpecifies the location and name of the file(s) you want to process.

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    Switches +R Sets the Read-Only file attribute.-R Clears the Read-Only file attribute.+A Sets the Archive file attribute.

    -A Clears the Archive file attribute.+S Sets the file as a System file.-S Clears the System file attribute.+H Sets the file as a Hidden file.-H Clears the Hidden file attribute. /S Processes files in the current directory and all of its Subdirectories.

    If a file has both the Hidden and System attributes set, you can clear bothattributes only with a single ATTRIB command. For example, to clear the Hiddenand System attributes for the STUDENT.TXT file.

    ATTRIB –S –H STUDENT.TXT

    You can use wildcards (? And *) with the filename parameter to display or changethe attributes for a group of files.

    Changing the attributes for a directoryYou can display or change the attributes for a directory. To use ATTRIB with adirectory, you must explicitly specify the directory name; For example, to hidethe directory c:\report, give the following command.

    ATTRIB + H C:\REPORT

    The following command would affect only files, not directories:ATTRIB +H C:*.*

    To assign the Read-Only attribute to the file REPORT.TXT type the followingcommand:

    ATTRIB +R REPORT.TXT

    To remove the Read-Only attribute from files in the \STUDENT\EXAM directoryon a disk in drive A and from files in any subdirectories of \STUDENTS\EXAM,

    type the following command.ATTRIB –R A:\STUDENT\EXAM\*.*/s

    SYSCreates a startup disk by copying hidden MS-DOS system files (IO.SYS andMSDOS.SYS), the MS-DOS command interpreter (COMMAND.COM)

    Syntax : SYS [drive:]

    Parameter

    drive:

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    If you press Y, MS-DOS saves each lost chain in the root directory as a file witha name in the format FILEnnnn.CHK. When CHKDSK finishes, you can examinethese files to see if they contain any data you need. If you press N, MS-DOSfixes the disk but does not save the contents of the lost allocation units.

    The CHKDSK command finds only logical errors in the file system, not physicaldisk errors. To find out how much data is stored on drive C and how much spaceis still free, and to check the disk for errors, type the following command:

    CHKDSK C:

    MSBACKUPRuns Microsoft Backup for MS-DOS, which backs - up or restores one or morefiles from one disk onto another.

    You can backup all files on a disk or files that have changed since your lastbackup.

    Syntax : MSBACKUP [setup_file][/BW | /LCD | MDA]

    Parameter setup_fileSpecifies the setup file that defines files to backup and the type of backup youwant to perform. MSBACKUP creates a setup file when you save program settingsand file selections. Setup files must have a SET extension. If you do not specifya setup file, MSBACKUP use DEFAULT.SET.

    MSBACKUP must start from a hard disk.

    Backup catalogsAs part of the backup process, MSBACKUP creates a backup catalog thatcontains information about the files you backed up. When you need to restoreone or more files, you can load the backup catalog and easily select files from abackup set. The backup catalog includes information about the:

    Backup disk’s directory structure,

    Names, sizes and attributes of the directories and files that were selected,Total number of files,Total size of the backupName of the setup file that was used,Date the backup was made.

    MSBACKUP gives each catalog file a unique name that helps you identify abackup set. Each character is the catalog name contains information about aparticular backup set. For example, consider a typical catalog name such asCD20823A. FUL. Reading left to right, the character(s) in the filename mean the

    following:

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    Character(s) Meaning

    C The first drive backed up in the set.D The last drive backed up in this set.

    2 The last digit of the year, as determined by the system date. In the example,the year is 1992.

    08 The month the backup set was created.23 The day of the month the backup set was created.

    If more than one backup of the same drive(s) is performed on the same day andif Keep Old Backup Catalogs option is set to on, MSBACKUP assigns a letterfrom A to Z to indicate the order in which the backups were performed (A is thefirst backup you created that day, B is the second, C the third, and so on). If theKeep Old Backup Catalogs option is set to off, this alternates between A and B.

    FULThe backup type DDFUL indicates a full backup, INC indicates an incrementalbackup, and DIF indicates a differential backup.

    You can easily locate the catalog for a backup set by using the informationcontained in the catalog filenames, even if you have many catalog files in yourdirectory.

    Each time you perform a full backup using a specific setup file, MSBACKUPcreates a master catalog. The master catalog keeps track of all the backupcatalogs made during the backup cycle. When the next full backup is performedand a new backup cycle begins, a new master catalog is created.

    The master catalog is used if you need to restore a complete backup cycle.When you load the master catalog, the catalogs of all the backups that werecreated during the backup cycle are automatically merged. Then the latest versionof each backed - up file can be automatically restored (or you can choose torestore an earlier version).

    You can choose whether you want to keep all of the old catalogs or only the

    current catalogs on your hard disk. The catalogs will remain part of your backupsets.

    When you backup files, MSBACKUP places one copy of the backup catalog onyour hard disk, and a second coy on the disk that contains your backup set. Tostart Backup for MS-DOS type the following at the command line:

    C:>MSBACKUP

    The changes you make to the configuration of Backup for MS-DOS are saved in

    the BACKUP directory on drive C.

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    Suppose you created a setup file named WEEKLY.SET that defines a weeklyfull backup procedure on specified files. To use this setup file, type the followingat the command line:

    MSBACKUP WEEKLY

    FDISKStarts the Fdisk program, which configures a hard disk for use with MS-DOS.Fdisk displays a series of menus to help you partition your hard disk(s) for MS-DOS.

    To start the Fdisk program, use the following syntax :

    FDISK

    Creating a primary MS-DOS partitionCreating an extended MS-DOS partitionSetting a partition to activeDeleting a partitionDisplaying partition data

    Selecting the next hard disk for partitioning, if a system has multiple hard disks.

    CAUTION : Do not experiment with Fdisk. If you accidentally delete a drive’spartition you loose all the data from your hard disk.

    Viewing partition information quickly and easily.

    To change the size of a partition, you must actually delete the partition andcreate a new one with a different size.

    The maximum partition size is 2 gigabytes.

    CAUTION : Deleting a partition deletes all the data stored on that partition.

    UNFORMATRestores a disk that was erased by using the FORMAT command.UNFORMAT restores only local hard disk drives and floppy disk drives; it cannotbe used on network drives. The UNFORMAT command can also rebuild acorrupted disk partition table on a hard disk drive.

    Syntax : UNFORMAT drive [/L] [/TEST] [/P]

    Parameter drive:

    Specifies the drive that contains the disk on which you want to recover files.

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    If the FORMAT command was used with the /U switch, UNFORMAT cannotrestore the disk to its previous condition.

    To determine whether UNFORMAT can restore a formatted disk in drive A, type

    the following commandUNFORMAT A:/TEST

    MOVEMoves one or more files to the location you specify. The MOVE command canalso be used to rename directories.

    Syntax : MOVE [/Y|/-Y] [drive:][path]filename[,[drive:][path]filename[…]]destination

    Parameters [drive:][path]filenameSpecifies the location and name of the file or files you want to move.DestinationSpecifies the new location of the file, or the new name of the directory. Destinationcan consist of a drive, a directory name, or a combination.

    Switches

     /Y Indicates that you want MOVE to replace existing file(s) withoutprompting you for confirmation.

     /-Y Indicates that you want MOVE to prompt you for confirmation whenreplacing an existing file.

    Suppose C:\LETTERS is a directory. To move the files ED.TXT and SIGRID.TXTfrom the current directory to the LETTERS directory on drive C, type the followingat the command prompt:

    MOVE ED.TXT, SIGRID.TXT C:\LETTERS

    To move the BILL.TXT file from the current directory to the LETTERS directoryon drive C and rename it ANN.TXT, type the following at the command prompt:

    MOVE BILL.TXT C:\LETTERS\ANN.TXT

    To rename the report 97 directory on drive C to report 98, type the following atthe command prompt.

    MOVE C:\REPORT97 C:\REPORT98

    EDITStarts MS-DOS Editor, a text editor you can use to create and edit ASCII textfiles.

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    MS-DOS Editor is a full-screen editor that allows you to create, edit, save andprint ASCII text files. Using MS-DOS Editor, you can choose commands frommenus and specify information and preferences in dialog boxes.

    Syntax : EDIT [[drive:][path]filename]

    Parameter [drive:][path]filenameSpecifies the location and name of an ASCII test file. If the file doesn’t exist, MS-DOS Editor creates it. If the file exists, MS-DOS Editor opens it and displays itscontents on the scre