introduction & windows

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INTRODUCTION

Today computers have gained access to every aspect of our life. It is very hard to imagine a worldwithout computers. Now a days, the computers have come up in such a big way that their presence is felt everysphere of life such as education, business, research, medicine, banking, communication etc.What is a computer?

A computer is an automatic electronic device, that process data & generates meaningful information with highspeed & accuracy.

Computers are treated as data processing machines. They take data as input, process data and produces

information as out-put. Hence a computer is treated as universal information manipulator.

Characteristics of computers: - Every computer performs 4 basic functions; they are i/p, storage, processing ando/p data. Following are the characteristics of a digital computer.

1) Automatic: - Computers are automatic in operation i.e. they work without human intervention.Computers are automatic machines because once started on a Job, they work until the job is finished.

2) Speed: - As the computer is electronic, it works with a very high speed. The speed of execution ofoperation by modern computer is several million operations per second.

3) Accuracy: - Computers are very accurate, degree of accuracy of computer depends on its design,however every calculation is performed with the same accuracy.

4) Diligence: - A computer does not suffer from tiredness or lack of concentration. When a computerperforms a millions of operations, it performs the last calculation with the same accuracy and perfection, as it willdo the 1st one.

5) Versatility: -Computers are extremely versatile & are capable of performing almost any task. Computersare used in education, training, preparing electric bill, Air & Railways reservation, Banking, business, industriesetc.,

6) Storage: - Computer has in built memory, where it can store large amount of data. Also huge amount ofdata can be stored using secondary storage.

7) Reliability: - Todays computers are highly reliable & give consistent results without errors.

History of computers (Early computing devices)

1) The abacus was the first computing device, which emerged about 5000 years ago. It wasinvented in china. It is a rectangular wooden frame with beads on parallel wires.

2) The first mechanical adding machine was invented by Blaise Pascal in 1642 & calledPascaline. It was limited only for addition.3) In 1694, a German mathematician & philosophy Leibniz, improved pascaline by creating amachine where multiplication was done. It was called Rotation wheel calculator. Both Pascaline &Leibniz machines worked by a system ofGears & dials.

4) Difference engine: - In 1822, a professor of mathematics, Charles Babbage invented thedifferential Engine. It was used to calculate various mathematical functions and to perform differentialequations.

5) Analytical Engine: - After working for ten years Charles Babbage developed the analyticalengine. It consists of 5 functional units such as input unit, memory unit, arithmetic unit, control unit andout put unit. The modern computers resemble the analytical engine. Hence Charles Babbage is calledthe father of Computers.

6) Mark-I: - In 1943,an American Mathematician, Howard H.Aiken built the first electromechanical computer, Mark-I. It was capable of performing arithmetic operations

7) ENIAC (Electronic Numerical Integrator And Calculator): - ENIAC was the first all electroniccomputers. It was a general-purpose computer.

8) EDVAC (Electronic Discrete Variable Automatic Computer) : - EDVAC was the first evercomputer developed on stored program concept.

9) UNIVAC-I (Universal Automatic Computer): - UNIVAC-I was the first commercial computerused for both scientific & commercial applications. This is the first digital computer.

Generations of Computers:

Generations of computers are broadly classified in two types:

1. Non- electronic generation 2. Electronic generationNon-Electronic Generation:- These are also called Zero generation computers. They were made up of woodenor mechanical computers. They were developed before 1946.

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Ex: - Abacus, Napiers bones, differential engine etc.Electronic Generation: - Computer developed after first electronic computer ENIAC are classified into five

generations. Based on the technology used in architectural development of computers.First Generation of Computers: (era of vacuum tube): These were developed between 1946-59, and built with

vacuum tubes. Their speed was 10-3 sec. They have limited primary memory. They used punched cardand magnetic tape to input and output operations. The instructions were given in Machine language andwere machine dependent.Ex: - ENIAC, UNIVAC, EDSAC, EDVAC.Disadvantages: 1.Size of computer becomes large hence non-portable.

2. Air conditioning is required since large amount of heat is liberated by vacuum tube.3. Switching time is very high and speed of the computer is slow.4. Machine language was used which is machine dependent.

Second-generation computer: - Thee were developed between 1957-64 and were built diodes and transistors.Their speed was 10-6 sec. They had more primary memory and proved higher reliability. High Levelprogramming languages like FORTRAN, Pascal, ALGOL etc., were used in these machine. Multi-programming. Time-sharing and Real-time processing were introduced.Ex: - BURROUGHS 5000, IBM 1401, GE635, CDC 1604, HONEYWELL 400 etc.

Third Generation of Computer (1965-70): -

These were built with Integrated Circuit (I Cs), 10-1000 transistors in a single silicon chip. Their speed

was 10-9 sec (nano second). They have semi-conducting memory. They have higher reliability andreduced size. They were used in weather forecasting, airline reservation, banking services.Ex: - IBM 35060, Honeywell 6000, Cyber-175, etc.

Fourth Generation Computer (1975 onwards): -

These built with large-scale integration (LSI), 100-1000 transistor in a single chip and very largescale integration (VLSI), 1000 to millions of transistors per chip. They have huge storage capacityand their processing speed is from 10 -12 sec. The concept of networking was introduced.Ex: - IBM 3033, HP-3000, CYBER-205, all modern PCs.

Sl.

No.

GenerationsI

(1946-59)

II

(1957-64)

III

(1965-75)

IV

(1975-Onwards)

1. Technologies Vacuum Tubes Transistors Integrated CircuitsLSI circuit andVLSI circuit andsemiconductor memories

2. SoftwareMachineLanguage

COBOL, FORTRANFORTRAN-IV,COBOL-68, PL/1

PASCAL, FORTRAN-77,COBOL-74

3. Number of users 1 1 Multiple users Remote users

4. Nature of processing serial Serial Serial Serial/parallel

5. Execution speedMillisecond(Thousandth of asecond)

Micro second(Millionth of a second)

Nanoseconds(Billionth of asecond)

Pico seconds(Trillionth of a second)

6.

Representative

computers

ENIAC,

UNIVAC I etc.

IBM-7094,

CDC 1604

IBM 360, CDC-

6000

7. ApplicationsMostly scientific,simple businessapplication

Extensive businessapplication, Scientificresearch

Databasemanagementsystems, on linesystem

Personal computer,Integrated CAD/CAM,Distributed system

Fifth generation of computer:The development of super computers was the key motivation of the 5 th generation supercomputer.Computers developed with Super Large Scale Integration (SLSI), have millions of transistors per chip.Fifth generation computers have following characteristics.

1) Mega chip memories2) Extensive use of parallel processing and

3) Artificial intelligence.

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Classification of computers:

Computers can be classified into various types based on

Principle of working

Size and capabilityClassification based on Principle of working

Based on principle of working, computers are classified into 3 types:1. Analog computers2. Digital computers

3. Hybrid computersAnalog computers are used to process data that occurs in continuous flow such as temperature pressure,

voltage variation, force, acceleration etc.Digital computers are used to process alphanumeric and graphic data. They work on the principal of

counting.Hybrid computer are the combination of both analog and digital computers. They accept either the

analog or digital data for processing.Digital computers are further classified into Special purpose and General-purpose computers.Special purpose computers are designed for specific applications like computers used for air traffic

control, process control in industry, robots, etc.General-purpose computers are designed to solve wide variety of problems to meet the needs of many

different applications.e.g.: - Payroll, sales analysis, games, etc.

Classification based on Size and capability

Based on size and capability, computers are classified into 4 types1. Micro computers2. Mini computers3. Mainframe computers4. Super computers

I. Microcomputers: These are also calledpersonal computers (pcs) because one person uses them at a time.Initially, pcs had very limited input-output capabilities & small storage capacity. But modern computershave large input-output capabilities, huge amount of memory &processing speed. In short these are called

micros.Depending on the size, speed and storage pcs are further classified into

1. Desktops 2. PortablesThe pcs are called as Home computers or Desktops, which are used in many applications of homes,schools, business organizations etc.Portables are small size computers that can be carried around. Different types of portables available; theyare laptops, notebooks, palmtops and wearable computers.1. Laptops: It works similar to desktops but smaller in size. They are expensive than desktops. Theyweigh around 3 to 5 kgs. It may be either AC-powered, battery powered, or both.2. Notebooks: They are as powerful as desktops but have the size of a notebook. They weigh 2 to 3 kgs.They are costlier compared to laptops.3. Palmtops: Alsocalled PDAs (personal Digital Assistant). They are small enough to be held in ones

palm. They are not as powerful as desktops. They are used for word processing, spreadsheet calculations,playing games, faxing and paging.4. Wearable computers: the size is very small and can be worn on the body itself. It has smallerprocessing power.

II. Minicomputers: Minicomputers are slightly bigger in size, memory & speed compared to microcomputers.Minicomputers are multi-user systems i.e. more than user can use the computer system at the same time.The CPU speed is 10-30 MIPS. The word length of these computers is 16 to 32 bits. In short these arecalled minis.e.g. IBM System/38,HP-3000, Digital Alpha etc.

III. Mainframe computers: Mainframe computers are larger than micros and minis and occupy a room. A

Mainframe computer is connected with several micros and minis. The CPU speed is more than100 MIPS(Million instructions per second).The word length of these computers is 32 to 64 bits and has a largestorage capacity. In short these are called midis.

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IV. Super computers: Super computers are designed for ultra high performance tasks such as weatherforecasting, defense research, space research etc. Super computers are large, expensive and have highstorage densities .Their high speed is due to the use of a number of processors working in parallel. Theyare 64 bits or 96 bits computers and process more than 10,000 MIPS.e.g. PARAM 10,000, CRAY XMP, CAAY YMP series etc.

Applications of Computers

The idea behind the invention of Computer was to make a machine that assists man in every day life.Computers changed the life of every organization. Computers are used for simple calculation to complex

applications such as, weather forecasting, weapons control etc.In this section, we discuss the following

Educational applications

Commercial applications

Telecommunication

Industrial application

1) Computers in Education:

Computers are used in the field of education for many purposes ranging from preparation of timetable toexamination results. Educational software has major influence at all levels from elementary schools to university.Connecting computers & students together over Internet opens up more educational opportunities.

2) Computers in Business:

Today each and every company depends on computers for numerous clerical and administrativefunctions. Computers are extensively used in daily transactions like pay roll, personnel, office accounts,invoicing, record keeping, stock control, sales analysis, etc.

3) Computers in Communications: -Computersused in teleconferencing to communicate and discuss on lineprojects and technologies. E-mail facility allows people to come together globally. We can have a face-to-faceconversation with a friend residing in other country. This is possible by world wide web (www). Computers usedas switching elements in telephone exchange. Computers also used in satellite communication.

4) Computers in industry: Computers have a major impact on industries where products are designed andmanufactured. Computer aided manufacturing (CAM) is used to produce them.

a. Product design: Designing complicated products need a teamwork to produce computerizeddesign. Computer aided design (CAD) is used to develop the products. Computers are used to designthe cars, jet engines, ships, roads, buildings, machine components etc.

b. Factories: Computers are used for many purposes including inventory control, planning andprocess control. Computers are used to measure & control variables like temperature, pressure etc.

5) Computers in Science and technology: Computers are used in scientific and technological activities likeweather forecasting, weapon control, controlling a satellite, medical diagnoses, remote surgery etc.

a) Chemistry: A chemical process is explored on a computer; the reactions are distinguished usingcolors. Suitable software is used to draw the structure of chemical compounds.

b) Space technology: Computers are used for designing, launching, & controlling a satellite.Computers are usedto constantly monitor and control the functioning of a satellite.

c) Medical diagnosis: Computers are used in hospitals for maintenance of drugs, surgicalequipments, hospital personnel, payroll, accounting, records of patients, diagnosis of diseases, treatment and soon.

6) Defense applications: Computers are used in various activities of air force, navy and army. Computer usestarts from recruitment and training to war and retirement. Computers are used to know the working conditions ofweapons (in army), to detect the enemy ship (in navy) and for training the pilots in air force

7) Applications of computer graphics: Computer graphics is mainly used in animation. Animation makesimages more realistic and put them in motion. There are varieties of uses for computer animation that rangefrom fun to practical applications.

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Science &Technology

Defenseapplications

Applications of Computer Graphics

Multimedia applications


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Input Unit

ALU

CU

Register

Output Unit

Memory

7) Multimedia Applications: Multimedia Applications use a collection of multiple media sources liketext, graphics, images, sound, video & animation. Multimedia can be used for entertainment, education,training, simulations, exhibitions etc.

------- #### ---------

COMPUTER ORGANIZATION

Block Diagram of a computer:

1. Input Unit [I/P]: A Device that accepts the information from the user is called InputUnit. Whose main function is to accept the data and information provided by the user of

the system and pass this information to the CPU or to the memory for storage. The inputunit basically links the external world or environment to the computr system. A systemmay consist of one or more input devices. The most commonly used input devices areKeyboard& Mouse. Other input devices are 1. Joy stick 2. Track Ball 3. Light Pen4. Scanner 5. OMR 6. OCR 7. MICR 8. BCR

2. Central Processing Unit [CPU] : It is the main part of the Computer System. Sometimes it is also called as Heart of a Computer or Brain of a computer. Most computersare identified by the type of CPU that is present in them. The Function of the CPU is tointerpret the instructions in the program and execute them one by one. It consists ofTHREE sub units. They are,a. Control Unit [CU] b. Arithmetic Logic Unit [ALU] c. Registers.

a. Control Unit [CU]: It controls and directs the transfer of program instructions anddata between various units. The main activity of the control unit is to maintain orderand direct the operations of the entire system. In other words, it controls the overallactivities of the entire system.Functions of Control Units: 1. Maintains order and controls activity in CPU2. Directs sequence of operations.3. Communicates with Input-Output devices for transfer of data/results into/Fromstorage.

b. Arithmetic and Logical Unit [ALU] : Is the place where the actual execution of theinstructions takes place during the processing operation. Arithmetic operations like

Addition (+), Subtraction (-), Multiplication (*) and division (/). Logical operation likeAND, OR, NOT and Relation operators like Less than (), Less then

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A Computer is designed using FOURbasic units. They are:1. Input Unit [ I/P ]

2. Central Processing Unit[CPU]

a. Control Unit [CU]b. Arithmetic &Logic Unit[ALU]c. Registers.

3. Output Unit [O/P]4. Memory Unit.


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or equal to (=), equal to (=) are being carried out inthis unit.Functions of ALU are 1. Performs arithmetic functions 2. Does LogicalOperations3. Does Branching on prefixed conditions.

c. Registers: The CPU consists of a number of temporary storage units, Which are usedto store instructions and intermediate data, which may be generated duringprocessing. CPU consists of FOUR general purpose registers are AX (Accumulator), BX

(Base), CX (Counter), DX (Data).3. Output Unit: It is used to print or display the results, which are stored in the memoryunit. The output unit links the computer to the outside world. As the computer workswith binary values the output generated will also in this form. The output unit convertsthe data from binary form to the user understandable form before it displays the results.Some of the output devices are ,a. Monitor b. Printer c. Speakers d. Plotter.

4. Memory Unit: It is a storage unit. The memory unit provides space to store inputdata, intermediate results and the final output generated. There are two classes ofmemory devices called Primary Storage and Secondary Storage. The primary memoryor the main memory is a fast memory capable of operating at electronic speed.

Secondary storage devices are additional memory devices such as floppy disks,magnetic tapes, hard disks and compact disks etc., which are used to store hugeinformation for future use.

The Storage capacity of a computer is measured in terms of Bytes. One byteincludes total of 8 individual units called as bit [Binary digIT]. One bit can store eithera 0(Zero) or 1(One).

Name Shorthand

Power Bytes

Byte 1Byte 20 1Kilobyte 1KB 210 1024

Megabyte 1MB 220

1,048,576Gigabyte 1GB 230 1,073,741,824Terabyte 1TB 240 1,099,511,627,776

The input unit, output unit and Secondary storage devices are together known asPeripheral devices.

Computer Memory: Memory is an essential component of a digital computer. It is astorage device. It stores programs, data, results etc., The two kinds of memory arecommonly used in modern computers.

6

Memory

Primary Memory Secondary Memory

RAM ROM Floppy HardDisk CD-ROM Pen Drive

Static

RAM

Dynamic

RAMPROM EPROM EEPROM


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1. Primary Memory: Is a temporary memory. It is also called as Main Memory orVolatile Memory, their contents are erased when power goes off. The primarymemory is faster, compact and lighter and it consumes less power. It is a staticdevice as there is no rotating part in it. It stores programs and data, which arecurrently needed by the CPU. The size of the main memory is comparatively muchsmaller than that of the secondary memory, because of its high cast. The CPUcommunicates directly only with the main memory.Function of the Primary Memory:1. To contain a copy of the main software [S/W] program (Operating System). This

program is loaded into the primary memory when the computer is turned on.2. Temporarily store a copy of the application program that is currently being

executed.3. Temporarily store the data input from the keyboard, which is required for

processing.4. Temporarily store the result, which is generated from processing until it is

transferred to an output device.Primary memories are of two types, a. RAM b. ROM.

a. RAM [Random Access Memory]: RAM is Volatile Memory. The informationwritten into it is retained in it as long as the power supply is on. As soon as the powersupply goes off (or is interrupted) its stored information is lost. RAM is also called as

the main memory of a computer. The user can write information into RAM and Readinformation from it. RAM is accessible to users. In RAM any memory location can beaccessed in a random manner directly without going through any other memorylocation. The access time is same for each memory location. There are two importanttypes of RAM. i. Static RAM ii. Dynamic RAM

i). Static RAM: It retains stored information as long as the power supply is on.Static RAM is costlier and consumes more power. It do not need refreshingcircuitry and have higher speed than dynamic RAM.ii). Dynamic RAM: It loses its stored information in a very short time (a fewmilliseconds) even though the power supply is on. It have to be refreshedperiodically, generally every 2 millisecond. Is cheaper and consumes less power. It

is used where large capacity of memory is needed.b. Read Only Memory [ROM]: It is nonvolatile memory i.e., the information storedin it is not lost even when the power supply goes off. It is used for permanent storageof information only at the time of Manufacturing. It is also called as Write Once andRead Many Times. There are 3 types of ROM, They are, i. PROM ii. EPROM

iii. EEPROMi). PROM [Programmable Read Only Memory]: The user can store permanentprograms, data or any other kind of information in a PROM. Special equipmentcalled PROM Programmer is available for the programming of PROM. Is onceProgrammable i.e., the user can write his information in a PROM only once.ii). EPROM [Erasable Programmable Read Only Memory]: Any number of

times erases the data and reprogrammed. EPROM IC has to be removed from thecomputer for the Exposure to high intensity ultraviolet light for about 20 minutesand erase entire data stored in EPROM and reprogrammed. The user cannot erasethe contents of certain selected memory locations. EPROM is cheap, reliable andhence they are widely used.iii). EEPROM [Electrically Erasable Programmable Read Only Memory]:Any number of times erases the data and reprogrammed with in the same circuit.It is possible to integrate the circuitry into the computer, so that the EEPROM doesnot have to be removed form its socket for programming.

2. Secondary Storage Device: Any additional storage used in a computer other thanthe primary memory may be classified as secondary memory or storage. These

devices are normally very slow compared to the primary storage. The data on thesecondary storage is not directly accessible for processing. All the data required for

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processing has to be routed through the primary or main memory as for as the CPU isconcerned.

The Secondary memory is used as auxiliary memory. Thesize of the secondary is normally large and the cost is alsoreasonable. The secondary memory is a non-volatilememory. It must store information permanently. Thesecondary memory is used for bulk storage of programs,data and other information. It has much larger capacity

than main memory. It stores system software assemblers,compiler, useful packages, large data file etc., themagnetic memories such as hard disks and floppy disksare the most common secondary memories used incomputers.

Magnetic Disks: Magnetic disks are thin circular plastic plates on which some magneticmaterial is coated. The appearance is somewhat similar to a gramophone plate.Magnetic disks come in various sizes and materials. They use the properties ofmagnetism to store the data on a magnetic surface. A disk pack normally consists of anumber of such disks mounted on a central shaft. The central shaft rotates at speeds of

about 7200 revolutions per minute (rpm).In a disk plate information is stored on both surfaces. The surface is furtherdivided into a number of invisible concentric circles called as Tracks . The tacks are

further divided into various sections called as Sectors .

Some Important Magnetic Disks are 1. Hard Disk 2. Floppy Disk

1. Hard Disk: The most common physical device for storing files is the Hard disk. Thehard disk typically contains several rotating disk plates, which are permanentlyencased in a pack or drive. The surfaces of the plates are coated with metal oxide,electromagnetic recording heads, like those on an audiocassette recorder, andperforms the read/write operation.

Into Sectors , Set of matched tracks are called Cylinder.

The time taken to access a particular block consists of:a. Seek time: Time to move the heads to the right or specified track.b. Latency time: Time waiting for the sector to come around to the head.

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The information stored on a disk can be readany number of times without affecting thestored data.

Advantages: 1. More Reliable2. High storage Capacity3. Direct access to Data.

Sectors

Tracks

There is one head for each surface, andall the heads moves together. The diskrotates at around 7200 rpm. Moderndisks typically hold 40GB to 200GB ofdata. The surface of a plate isorganized as a number of concentric


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c. Block transfer time: Time to actually transfer the data.

2. Floppy Disk: Is a removable disk. It contains a single flat piece of circular plastic diskcoated with metal oxide and enclosed in plastic cover. Diskettes are small andportable. Three common sizes are 3 inches, 5 inches and 8 inches in diameter. Themost commonly used floppy disk is of 3 inches with storage capacity of 1.44 MB and isof double-sided high-density capacities.Advantages: 1. Disks are cheap 2. Portable 3. Easy to handle.

Optical Disks: Optical disks consist of a rotating disk, which is coated with a highlyreflective material. Data recording on the disk is done by focusing a laser beam on thesurface of the spinning disk. The laser beam is turned on and off at varying rates thiscauses tiny holes to be burnt on the surface. The beam is strongly reflected by thenormal surface and weakly reflected by the pits. This sequence of reflections is thenconverted into electronic signals. There are different types of optical laser disks. Theyare 1. CD-ROM 2. DVD 3.WORM

1. CD-ROM [Compact Disk Read Only Memory]: Is a read only optical storage mediumcapable of holding up to 682MB of data approximately 3,33,000 pages of text, 74minutes of audio recording. Data accessing is faster than floppy disk but is

considerably slower than the modern hard disk. To read information from the disk weneed CD-ROM drive. Erase or written information on to the disk with the help ofCD-Writer.

There are 2 types of CD-ROMs,a. CD-R: It is also called as the Recordable-CD. It is written once and read many

times. Data once written cannot be erased.

b. CD-RW: This is Rewritable-drive. This allows the user to erase previouslyrecorded information and then to record new information onto the same physicallocation on the disk.

2. DVD [Digital Versatile Disk]: It works exactly like CD-ROM but packs more data bitsinto the same area. Physically, CD-ROM & DVD-ROM disks are similar but DVD holdsupto 25 times more than CD-ROM. Each side of DVD can hold upto 4.7GB [i.e., it canhold 4 films in a single disk.]

3. WORM [Write Once Read Many]:Once the data has been fixed onto the surface of aWORM disk they cannot be changed. WORM is an ideal medium for making apermanent record of data. e.g. many banks use WORM disks to store a record of eachday transactions. The transactions are written to an optical disk& become apermanent record that can be read but never be altered.

Cache Memory: The word cache is pronounced as cash. The cache memory is placed

in between the CPU and main memory. It ismuch faster than main memory. Its accesstime is much less compared to that of mainmemory. The cache memory is anintermediate memory and is not accessible tousers. It stores instructions and data, whichare to be immediately executed. The cachememory increased the operating speed of thesystem. But it is much costlier than mainmemory.

Difference between Primary and Secondary Memory:

Primary Memory Secondary Memory

9

CPU

RAMCache

SystemBus


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1. Is a Temporary Memory 1. Is a Permanent Memory

2. Is a Volatile Memory 2. Is a Non-Volatile Memory

3. Limited Storage space 3. Huge Storage Space

4. Access time is nano seconds 4. Access time is milliseconds

5. High Cost 5. Cheaper than Primary memory

6. Power goes, Erase all the data presentin the memory.

6. Power goes, Data present in thesecondary memory is not erased.

Input-Output Devices: Computer systems are proved to be useful only whenthey are able to communicate with the external environment. The process ofexecuting a program requires us to provide some data from the externalenvironment to the system so that it can be used for computations. The inputand output devices provide a means for this interaction. They are also called as

Peripheral devicesInput-Output devices are of two types:1. Hard-copy devices and 2. Non-hard-copy devices

Hard-copy devices provide the output on paper or other permanent form.Non-Hard-copy devices present the output directly to the user in a nonpermanentform, such as the screen of a terminal or input the information directly to theusers a result of some action of the user, such as the pressing of a key on theterminal keyboard.

1. Input Devices: Data & instructions are entered into a computer throughinput devices. An input device converts input data and instructions intoelectrical signals (binary form) that can be accepted by the computer. A largevariety of input devices are available. They are, Keyboard, Mouse, MICR, OCR,OMR, Scanner, Trackball, Joystick, Light Pen.

a. Keyboard: The keyboard is the most conventional of all input devices. It isused to enter data directly into the computer. The prices of keyboards arereasonable and it is very simple to operate. The keyboard provides different keysto perform various operations. The arrangement of keys is similar to that of theconventional typewriter, but it has additional keys. The computer keyboard hasthree categories of keys. 1. Alphanumeric keys 2. Special keys 3. Functionkeys.

The alphanumeric keys consists of alphabets and numbers and otherspecial keys which represent certain symbols such as , .>


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OMR Answer Sheet

1.a b c d

2.a b c d

classified as either Regular Keyboard [Used with PCs and ATs] with 84 keys orEnhanced keyboard with 101keys and Multimedia keyboards.b. Mouse [Mechanically Operated User Serial Engine]: One of the most popularof specialized input devices for terminals or microcomputers is the mouse. Themouse is used as a pointing device. It is a small device, which was developed atthe Stanfordresearch institute.

It has two wheels at right angles to each other. Each of these wheels isconnected to the shaft encoder. For every incremental rotation of the wheel, the

shaft encoder produces an electrical signal. As the device is moved on a flatsurface, the movement is coded in the x and y direction. The device can be usedfor moving a cursor around the display screen.

There are basically three types of mouse:i. Mechanical Mouse 2. Optomechanical 3. Optical

i. Mechanical Mouse: This mouse has a small hard rubber ball underneaththat moves against two roller as it passes across a flat surface. Mechanicalsensors detect the movement of the rollers as an X and Y-axis and thecursor on screen is moved accordingly.

Optomechanical Mouse: This mouse works on the same principle. The rollershave wheels on the end of them with evenly spaced holes. As the wheels spin, alight-Sensitive

optical device counts the number of holes that pass by and convert thosenumbers to an X and Y-axis.ii. Optical Mouse: This mouse more accurate or precise and has no moving

parts. It uses a laser to detect movement and has to be paired with aspecial mat that has an embedded optical reference grid.

Devices Using Optical Media: Direct Data Entry [DDE] refers to entry of datadirectly into the computers through machine readable source documents. DDEdoes not require manual transcription of data from original paper documents.DDE devices can scan source documents magnetically or optically to capturedata for direct entry into the computer. The devices are,i. OMR ii. OCR iii. MICR

i. OMR [Optical Mark Reader]: The main use of these devices is to recognizecertain pre-specified types of marks suchas marks made by pencil or pen. Thesetypes of scanners are normally used ingrading objective type tests such as theCET conducted by the Pre-Universityboard. In these types of exams thestudent has to mark the answers toquestions on a special-scoring sheetcalled OMR Sheet by darkening a square

or circular space by a pencil to indicate the correct choice out of variousalternatives

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These answer [OMR] sheet are then fed into the computer with the use of aOMR. The OMR focuses light on the page being scanner and detects the reflectionpattern. Space which has been marked with the pencil or pen normally reflectslight.ii. OCR [Optical Character Recognition]:The main use of these devices is to

recognize alphabetic and numeric character printed on paper. Thecharacters may be typewritten or handwritten. Handwritten recognitionrequires extra care to ensure that the characters are of standard size,

shape and that the characters are connected with no stylish loops and soon. The OCR may be used to recognize certain standard typewritten fontssome OCR recognize computer outputs also.

The OCR goes through each character in detail as if the character is madeup of number of minute points. Once the whole character has beenscanned it compares the character with a standard font, which the systemhas been programmed to recognize. Wherever there is a pattern match thecharacter is considered to be read. Even if there is a slight difference thecharacters is rejected.

OCRs are used in applications such as credit card billing and reading of pincode numbers in large post offices to sort mail geographically. This eliminates

the duplication of human effort required to get data into the computer. Opticalcharacter readers are also used in banks, insurance companies, airlines andsome retail outlets.Advantages of OCR:1. OCR eliminates the human effort of transcription.2. Paper work explosion can be handled because OCR is economical for a high

rate of input.3. Since documents have only to be typed or handwritten, not very skilled staff is

required.Disadvantages of OCR:

1. Only certain types of printed or handwritten characters can be read.2. Is Expensive.3. The reject and/or error rate may exceed user requirements.4. Slight damage to the document could cause the reader to reject it or read it

incorrectly.

MICR [Magnetic Ink Character Recognition]:The device is normally used to assistthe banking sector in processing the cheques that are issued by the customersevery day.iii. American Banking Association has set special font for these characters.MICR reads these characters by examining their shapes, using a 7 x 10 matrix

With MICR devices a special type of cheque is normally used. In a cheque,the branch code and the cheque number are preprinted at the bottom usingmagnetic ink. When a filled cheque is presented at the bank, the cheque can beprocessed using MICR.Advantages of MICR: 1. Provides automated, reliable source data entry.2. MICR possesses a very high reading accuracy. Cheques may be smearedstamped, roughly handled yet they are accurately read.3. Cheques can be read both by human beings and machines.Disadvantages of MICR: 1. Not fully automatic2. Damaged documents, cheques not encoded with amount etc, have still to bemanually processed.

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iv. Scanner: A Scanner is a direct entry input device that can be moved overa drawing or photograph or any other document. The scanner converts thedata that has been scanned into a digital format. The scanned document orphotograph can then be used in any form that is suitable for the computeruser. DTP operators who scan images and then reproduce them in thedocuments being prepared extensively use this process. The scanner can beused for recognizing any type of data i.e., either for image processing orcharacter recognition. Some important characteristics are ,

1. They eliminate the duplication of data, which may have occurred when ahuman being is made to enter data to the system.

2. Reducing human involvement improves the accuracy of the work and the timeinvolved in performing the entire operation.

3. The data to be scanned has to be of a higher quality; otherwise the scannermany reject it directly.

Out Put Devices: When a computer has completed its processing activities theinformation that has been produced has to be output in a format that it is usefulfor further activities. There is a wide range of devices available for outputs; thechoice of these devices depends on the following considerations.

Suitability of the application.

The speed at which the output is required.

Whether a printed version of the output is required.

The volume of data, which is output.

The cost of the method chosen to the benefits derived.Some of the output devices are: Printer, Monitor, Plotter, Speakers.

Printers: A printer is an output device that produces text and graphics on apaper. Printed information is often called Hard Copy because the informationexists physically and is a more permanent form of output and can not be

modifiable.The main advantage of the printer is information produced is permanent and thedisadvantage of the printer is time to get the printout is slow when comparedwith display devices.

There are two main classifications of printers.

i. Impact Printer: In impact printers, the print head mechanism strikes aninked ribbon located between the print head and the paper.

Features: 1. Uses force by applying hammer pins to strike the paper.2. Slow speed in characters per second3. Print on most paper types4. Transparencies not supported.5. Multiple copies may be printed at once.The two main types of impact printers are Dot matrix and Daisy Wheel.a. Dot Matrix Printer: A dot matrix creates an images by using a mechanism

called a print head which contains a cluster (or matrix) of short pinsarranged in one or more columns. By pushing out pins in various combinationsthe print head can create alphanumeric characters.When pushed out from the cluster, the protruding pins ends strike a ribbon,which held in place between the print head and the paper. When the pin

strikes the ribbon, they press ink from ribbon onto a piece of paper. The morepins that a print head contains the higher the printers resolution. The lowestresolution printers have only nine pins and the highest resolution printer have

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24 pins. The speed of the printer is measured in characters per second (cps).Printers speed range from 50 to 500 cps.

Non-Impact: With non-impact printers, the print head does not make contactwith the paper and no inked ribbon is necessary.

Features: 1. Printed head does not make contact with the paper.

2. Higher speed in characters per second is possible3. Prints on most paper types but better quality obtained with better paper.

4. Transparencies usually supported.The Three main types of non-impact printers are Inkjet Printer, LaserJet, &Thermal printer.The printer speed of a printer is usually expressed in Pages per minute (PPM).Printer resolution is often expressed in dpi (dots per inch). The Larger thenumber, the higher the resolution.

a. Inkjet Printer: Ink-Jet printers have become the defacto standard for homecomputers and low cost printing. They offer good quality at an affordableprice.

Conductive ink is forced through a small nozzle producing a small droplet ofink, which is propelled towards the screen surface. The size and spacing of theink drops is kept constant by vibrating the nozzle at a high frequency(100KHz). Each drop of ink, after leaving the nozzle, is charged as it passes anelectrode. The drops are deflected using another electrode. Characters areformed from a dot matrix; typically there are 103 drops per character. Printquality is high; speed is slow, typically about 100cps.

b. Laser Jet Printer: Laser printers are page printers. A page of text or pictureis composed at a time. A laser printer utilizes a laser beam that sensitizesselected areas on the print page. The laser-exposed areas attract a toner orink powder that attaches itself to the laser generated charges on the page.The toner is the permanently fused on the paper with heat or pressure. Theresolution of printing varies from 300 to 1200 dots per inch (dpi). It produces avery high quality print. It can handle large volumes of printed output. Thespeed range from 10 pages to about 200 pages per minute. This technology ischeaper and most popular in high quality printing operations.

Display Devices: A display device is an output device that conveys text,graphics and video information to a user. Information on a display device issometimes called as Soft Copy because it exists electronically and displaysonly for a temporary period. Display devices can be monochrome or color. Two

main types of display devices are CRT [Cathode Ray Tube] monitors and LCD[Liquid Crystal Display] monitors. A video card is required to display color on amonitor. The viewable size of a display device is the diagonally measurementof the screen. The quality of a display devices depends on resolution, pixeland refresh rate.

Advantages of display devices are 1. The time to display the image is fast.

2. Screen displays can include text, graphics and colors

3. No paper is wasted for obtaining the output.

Disadvantages: 1. Needs a separate device to produce the hard Copy.

2. Information produced on the screen is only temporary.

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Monitor or Visual Display Unit [VDU]: Monitor are devices used to display

both text and graphics images from the computer. Monitors come in various

sizes, commonly starting at 14 , then 15 , as well as 17 and 19. The larger

the size the more expensive and it required for higher resolutions.

Resolution refers to the number of dots displayed in the X(across) and

Y(down) coordinates. Typical screens are capable of displaying 640x 480 dots.

Refresh rate refers to the number of times per second that the image is

redrawn on the monitor screen. A refresh rate of 60hz means the images is

redrawn 60 times a second. Typical refresh rates are 60hz, 72hz and75hz.

Higher refresh rates required for larger resolutions else viewer tends to notice

the image on the screen flicker.

Data can be represented on the screen in two modes- text and graphics

mode. In text mode only text or individual characters can be displayed. The

VDU screen is divided into specific character positions-usually 80 columns of

characters across the width of the screen and 25 lines of characters from top

to bottom.

In the graphic mode, constructing an image on the screen using dots can

show the pictures. In the graphics mode, the screen is treated as an array of

tiny dots called pixels [picture element] and any thing that appears on the

screen is shown using these dots. Resolution of the screen indicates the

number of dots or pixels on the screen. A typical high resolution display ahs

640 columns of dots and across 480 rows of dots.

Modem: Modem stands for Modulator/DEModulator. In the simplest form, it

is an encoding as well as decoding device used in data transmission. It

converts a digital computer signal into an analog telephone signal [Modulate

the signal] and converts an analog telephone signal to digital computer signal

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[Demodulates the signal] in a data communication system. Modems are

required to Tele-communication computer data with ordinary telephone lines

because computer data is digital form but telephone lines are analog. Modems

are built with different ranges of transmission speeds. It is used in Internet

working to connect the computer with telephone lines.

Modems can be categorized according to speed, price and other features. But

most commonly, people classify them as internal and external modems.

Internal modems is very small and the fit inside the computer. External

modems connect to the serial port of the computers. Another category of

modems called PCMCIA [Personal Computer Memory Card International

Association]. These modems are used only with laptop computers. They are

small, about the size of a visiting card and are quite expensive.

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CHAPTER 3

COMPUTERHARDWAREAND SOFTWARE

Computer hardware: The term computer hardware refers to all physical devices, which are visible to

the user. The user can directly operate these devices. Computer hardware includes input devices,output devices, processing devices and other peripheral devices. These devices are required to beinterconnected so that they can function properly to perform their required task.Definition: The physical component of the computer system is called hard ware.e.g.: keyboard, mouse, monitor, printers, scanners, hard disk drives, floppy drives etc.Computer Software: Software is the general term describing programs written by the user, whichmakes it possible for individuals to use the computer. It is any prepared set of instructions that controlsthe operations of the computer, which deals with the codes, coded instructions according to which thecomputer operates.Definition: A set of programs written to a computer is called software.Software generally classified into two types 1. System software

2. Application software

1. System Software:

System software refers to all programs, which are responsible for maintaining and using thesystem i.e. they are responsible for the working of the computer. The manufactures of the systemcommonly supply system software.Definition: System software is a set of one or more programs, which are designed to control theoperation and extend the processing capability of the computer system. It is acts as intermediatorybetween hardware and application programs.

2. Application Software:

Application Software is a program used for specific purpose. Some important applicationsoftware includes Payroll systems, Inventory system, student maintenance system, Librarymanagement system and so on.Definition: Application software is a set of one or more programs designed to do a specific task suchas processing of student admission, examination result, pay calculation, etc.

The most widely used general purpose application packages are EXCEL, WORD, ORACLE,DTP packages and etc.COMPUTERLANGUAGES

A language is a means of communication between any two people. Similarly if we have tocommunicate with the computer we need a language. Such a language is called as programming

language. With the help of programming language a user can tell the computer what he wants it to do.Definition: Programming language is a set of rules which a user has to follow to instruct the computerwhat operations are to be performed.Programming languages are classified into following categories:

1. Low level languagesa. Machine level languageb. Assembly level language

2. High level languagesa. Specific purpose languagesb. General purpose languages

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1. Machine level languages: The computer understands only 0s and 1s.This language of the computer is called as the machine language ormachine code. The instruction provided by the machine language aredirectly understood by the computer and converted into electrical signalsto run the computer.

An instruction given in the machine language has two parts.a. OPCODE (operation code)

b. Operand (Address/ Location)11100000011111000 00011100

OPCODE OperandThe operation code denotes the operations, which is to be performed (such as add, multiply,

divide, move, data and so on). The operand part gives the location or address of the data on which theoperation code is to be applied.Definition: Machine language is the basic language of the computer, representing data as1s & 0s.Advantages of Machine language:

1. Machine language makes efficient use of storage (instructions and their storage in computermemory can be easily controlled).

2. Instructions of a machine language program are immediately executed. They require no

compilation or translation.3. Machine language instructions can be used to manipulate the individual bits in a byte of

computer storage.Disadvantages of Machine language:

1. Machine languages are machine dependent.2. Machine language is difficult to program.

2. Assembly level languages:

The draw back of the machine language has lead to introduce of a new language called assemblylanguage. The language is substitutes letters and symbols (mnemonics) for numbers in machineprogram. Assembly language is also called as symbolic language. A program written in symboliclanguage is called an assembly code or symbolic program.Definition: Assembly language is a low-level programming language that allows a user to writeprograms using letters and symbols which are more easily remembered.For example:

Statements Action

STA AADD BSTR CPRT CHLT

Load the data to accumulatorAdd the content of B to accumulatorStore the result in location CPrint the resultsStop

A computer can directly execute only machine language programs, which use numbers representing

instructions and storage locations. Hence, an assembly language program must be converted into itsequivalent machine language program, before it can be executed program. This translation is donewith the help of translator program, which is known as assembler.Assembler: Assembler is system software, which translates an assembly language program into itsequivalent machine language program.Advantages:

1. They are more standardized and easier to use than machine language2. They operate very effectively and easier to use than machine language.3. They are easier to debug because programs locate and identify syntax errors

Disadvantages:

1. Assembly language programs are usually very long.

2. Through less abstract than machine language, assembly language program are still complex3. Through more standardized than machine language, assembly languages are still machine

independent.

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3.High level languages:

To overcome the difficulties of low-level language such as machine dependency, difficult tounderstand and so on new high level problem oriented languages were developed. Such aprogramming languages have on extensive vocabulary of words and symbols which is English likeand are used to instruct a computer to carry out the necessary procedures, regardless of the type ofmachine being used.

Example: A typical program in high level language to add two numbers may like

However a program in high-level language has to be converted to its equivalent machine language tobe executed on a computer. The program that converts high-level language code into machine code iscalled translator. The translates programs are two types namely compiler and interpreters

High level languages are classified into two types. Namely,1. General purpose language 2. Specific purpose language

General purpose language can be used to solve a wide variety of problems such as business

problems, scientific problems, and graphical applications and so on.Example: BASIC, Pascal and C

Specific purpose languages can be used to solve only certain types of problemsExample: COBOL, FORTRAN.

ADVANTAGESOF HIGH-LEVELLANGUAGES:

1. Machine Independent: High-level languages are machine independent. This is a veryvaluable advantage because it means that a company changing computers even to one from adifferent manufacturer will not be required to rewrite all the programs that is currently using.2. Easy to learn and use: These languages are very similar to the languages normally used by usin our day-today life. Hence they are easy to learn and use. The programmer need not learn

anything about the computer is going to use.3. Fewer Errors and easier modification: In case of high level languages, since theprogrammer need not to write the entire small steps carried out by the computer, he is much lesslikely to make an error. Modifications to a program can be easily done with little or no effort at all.4. Better documentation: Higher level language is designed in such a way that its instructionsmay be written more like the language of the problem.5. High level programs may be used with different makes of computer with little modification.Thus, reprogramming expenses are greatly reduced, when new machines are acquired.6. Writing a programming in high-level language does not require the knowledge of the internalstructure of the computer.

DISADVANTAGES:

1. Lack of flexibility: Because the automatic feature of high-level languages always occur and arenot under the control of the programmer, they are less flexible than assembly language.

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2. Slower in execution: Runs slower due to generality of the statements and the fact that they areportable between different machines provide a suitable compiler is available. Such a languages aremachine independent.

Machine language High level language

1Uses only two symbols 0(zero) and 1 (one)

1Uses alphabets, digits, punctuations andsome special symbols.

2Each instructions is a sequence of 0s and 1s

2Each instruction is English likestatement

3 Can be directly executed 3 Cannot be directly executed4 Machine independent 4 Machine independent

5Difficult to understand modify, write and debug

5Easy to understand, write, modify anddebug

6 Efficient (Fast) 6 Less efficient (slow)

7 Not standardized 7 Standardized

8Called as the first generation programming

language8

Called as the third generationprogramming language.

Differentiate between Assembly language and high level language

Assembly language High level language

1 Mnemonic or symbolic instructions 1 English like statements

2 Machine dependent 2 Machine independent

3 Efficient 3 Less efficient

4It is not directly executed. First it should betranslated into machine language by theprocess called assembly

4It is also not directly executed. It shouldbe translated into machine language bythe process called compilation

5An assembler is used in translation process

5An interpreter or a complete is used intranslation process

6This is converted to machine readable fromin one step 6

It is first converted into machinesassembly language and then into machinelanguage. Hence two steps.

TRANSLATOR:

ASSEBLER: is a language translator for low-level language. Assembler is a system program ortranslator program that translates (converts) inputs source program written in Assembly language intooutput object program that consist machine language binary code 0s and 1s.INTERPRETERANDCOMPLIER

Interpreter and compliers are the language translators for high level languages. Although interpreter &compiler are used for high-level language translations, they differ in their operating mode.INTEPRETER: An interpreter is a language translator (for system program) which translate inputhigh level language program line by line (or instruction by instruction) into equivalent machinelanguage instructions and immediately executes each instructions if they are free from errors (if there

no grammatical or semantic mistakes)COMPILER: A compiler is a language translator which translate input high level language sourceprogram into equivalent machine level language program (called object program) the whole programis translated into equivalent machine level language if there are no syntax errors, but there is noimmediate execution of instruction by instruction as in case of interpreter.Differentiate between a complier and interpreter.

Compiler Interpreter

1It takes entire high-level language programas input and translates it into machinelanguage.

1It takes one statement of a high levellanguage program as input and translates itinto machine language and executes it.

2 All errors that occur in the program arelisted and displayed 2 Errors that occur only in the statementbeing taken for transaction are displayed

3 Debugging is faster 3 Debugging is slower

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4 Require more memory 4 Require less memory

5 Costlier 5 Cheaper

6 Security of source code 6 No security of source code

b. Computer Virus:

Computer viruses are every where. Their very names give computer users a scare-klez, Melissa, myheart, W32 and Michelangelo. With the use of the internet and endless communication betweencomputers, virus spreading faster than ever. The only way to prevent their growth is trough publicawareness of safe computing.

DEFINITIONOFVIRUS:A computer program, which is designed to replicate itself by copying itself into other program storedin a computer. It may have a negative effect, such as causing a program to operate incorrectly or itmay corrupt a computers memory. OR

A computer is simply a set of computer instructions or computer code that is written by someunscrupulous persons.TYPESOF VIRUS: Virus can be divided into classes according to the environment.i. File Virus: Either infect execution in various ways (parasitic-the most common type of virus), or

create file doubles (companion viruses),or use file system specific features(link virus)ii. Boot Virus: Either save them selves in disk boot sector, or to the Master Boot Record, or change

the pointer to achieve boot sector.

iii. Macro Virus: Infect document files, electronic spreads sheets and database of several popularsoftware packages.

iv. Network Virus: Use protocols and commands of computer network or email to spreadthemselves.

How does a computer get a virus?

Just as a human being virus is passed from person to person, a computer virus passed from computerto computer. Computer viruses spread from machine to machine on disks and telephone lines. A viruscan be attached to any file that you copy to your computer. If you download the files from the internetor copy programs or files from friends on floppy disks or pirated software, you are very susceptive toviruses. Many viruses are spread through e-mail.

Prevention of virus before they attack:

A computer virus can do extensive damage. Many viruses do wired little things that are adverselyaffect your computer. The most usual symptoms of a computer virus are erratic behavior. If yourcomputer starts to act a little wired, the first thing to do is to check for a virus.

If you are smart, you will stop viruses before they enter your computer. You can do this bypurchasing a good virus protection program. Such a program will check all files for viruses. Onceinstalled, an anti-virus program can be set to work in the background. It will check all files before theyenter your computer and will alert you if a virus is detected before it contaminates your system. If avirus is detected, your anti-virus program will quarantine or eliminate it so that it cannot harm yourcomputer.

Keep virus protection software up-to-date:New viruses are written everyday. It seems that there are many people in the world we have a lot otime on their hands and slightly warped idea of ho to use their intelligence. Luckily, companies likeMacAfee, Symantec and Panda software are consultancy scouting for new viruses and updating theiranti-virus software tools. They use any of the growing arsenals of weapons to detect and fight viruses.

ANTIVIRUSAntivirus software is a special kind of program that is written to isolate or remove viruses from yourcomputer.

Some antivirus programs are installed and run as you need them. Other more advancedantivirus can configured to automatically scan your computer for viruses and update them selves on aset schedule.

Viruses are usually very small programs that contain fragments of unique code. This codefragments can be used as a method of identification, or Fingerprints. Antivirus companies thencombine these fingerprints into one large data base called Virus definition

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When an antivirus programs scans computer for viruses, it compares the contents of each fileon your computer to its database of virus definition. If it finds a match, generally a virus is present.Some of the popular antivirus softwares are semantic, McAfee, Dr Solomon and sophos.Computer security:

Computers are every where in todays society. They are used to help control our telephonecommunication networks, and to process our paychecks. The computers play a big role and have a bigresponsibility. Mistakes can lead some one to loose his/her savings overnight, could lead to a loss of alife should an advance medical equipment malfunctions or could cause a plane to crash.

INTRODUCTION TO DATA BASE MANAGEMENT SYSTEM

The computer is invented as a calculating machine to solve scientific problems. As the hardwaretechnology is developed, the role of computers gradually changed towards solving business problems.Most of the real world problems involve a huge amount of information to be collected, stored, andretrieved and finally a report is generated. Hence database technology is one of the most rapidly growingareas of computer technology. Data and information system plays an important role in everyday life.Data processing by a computer is called Electronic Data processing (EDP).

Data and information: The word data is the plural of datum, which means facts.

Information is the processed data that is organized meaningful to the person receiving it. Hence dataprocessing is a process that converts data into information.

Database: A database is a collection of logically related data. Hence database is a collection ofdata that is organized and recorded in suitable format.

e.g. Telephone catalog is a database with the related data such as names, telephone numbers andaddress of the people.

A database can be simple or complex. It may be small or big. The colleges may have theirstudent database and library database. The student database may consist of the names of the students,date of birth, fees, address, combination etc. The library database may have the title of the books,authors, publishers, price, editions etc.

Data base management system [DBMS]: DBMS is software, which helps theuser to perform all related operations such as defining, sorting,retrieving and modifying information from a database. Hence DBMS is asoftware tool used INTRODUCTION TO DATA BASE MANAGEMENTSYSTEM

The computer is invented as a calculating machine to solve scientific problems. As the hardwaretechnology is developed, the role of computers gradually changed towards solving business problems.Most of the real world problems involve a huge amount of information to be collected, stored, andretrieved and finally a report is generated. Hence database technology is one of the most rapidly growingareas of computer technology. Data and information system plays an important role in everyday life.Data processing by a computer is called Electronic Data processing (EDP).

Data and information: The word data is the plural of datum, which means facts., quantities,characters or symbols operated on by a computer. Information is the processed data that is organizedmeaningful to the person receiving it.

Hence data processing is a process that converts data into information.

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Input(Data)

Process(Data processing)

Output(Information)

Input(Data)

Process(Data

processing)

Output(Information)


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Database: A database is a collection of logically related data. Hence database is a collection ofdata that is organized and recorded in suitable format.

e.g. Telephone catalog is a database with the related data such as names, telephone numbers andaddress of the people.

A database can be simple or complex. It may be small or big. The colleges may have theirstudent database and library database. The student database may consist of the names of the students,

date of birth, fees, address, combination etc. The library database may have the title of the books,authors, publishers, price, editions etc.

Data base management system [DBMS]: DBMS is software, which helps the user to perform allrelated operations such as defining, sorting, retrieving and modifying information from a database.Hence DBMS is a software tool used to process data into useful information. A DBMS allowsdifferent class of users to access and manipulate different portions of data in the database. A DBMSalso ensures the security, integrity, and privacy by providing a centralized control of database.

Advantages of data base management system

1. Data sharing and multiple accesses: Since different users present at differentphysical locations, data must be sharable. Data must be sharable since a large number of operationsmay be common to the different user groups.

2. Data consistency:

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CHAPTER - 4

OPERATING SYSTEM (OS)For the proper functioning of a computer it is necessary that the Hardware and its

corresponding Software work together with each other. WithoutSoftware a computer is a useless scrap

of metal, with software a computer can perform a vide variety of operations such as storinginformation, processing data and retrieving information, spell checking, playing games and manyother valuable activities.

Computer Software is divided into two types.1) System Software2) Application Software

1) System Software: This manages the operations of the computer.e.g. Windows, DOS, Unix etc.

2) Application Software: This solves the problems for the user.e.g. Word-processing, Excel etc.

What is Operating System?

An Operating System is a computer program, which acts as an intermediary between the userof the computer& the computer Hardware. The main aim of the operating system is to provide aproper environment in which the user can use the computer in an efficient manner.

There cannot be any computer without an operating system to help in its functioning. Acomputer system can be roughly divided into four components, the Hardware, the operating System,the application programs and the users.

User1 User2 ..User N

System Structure

System Structure: At the lowest level lies the Physical Device, consisting of integratedcircuits, the power supply & other components of the system necessary for its functioning. Next liesthe layer of primitive software, which directly controls the physical device and provides a neatinterface to the next layer. This software is called the micro-program. The micro-program is usually

located only in the read only memory (ROM), it is actually an interpreter, which gets a machinelanguage instruction & carries them as a series of small steps. The set of instructions, which the micro-program interprets, is called the machine language.

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Application Program

Operating System

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The layer above is the operating system, which hides the complexity present below and givesthe user a convenient set of instructions to work with. On the top of the operating system softwareincludes command interpreters, compilers, editors and other similar programs, which are independent.

Finally, above the entire system lie the application programs. The user creates these applicationprograms and in his activities such as commercial data processing, game playing or any otherapplication.MAINFUNCTIONSOF OPERATING SYSTEMS.

1) Loads and Executes programs and Utilities.

2) Schedules and controls input and output operations and jobs.3) Allocates peripherals to programs after checking their availability.4) Controls storage space for their allocation and de-allocation.5) Supervises the overall operation of the computer.DIFFERENT VIEWSOFTHE OPERATING SYSTEM

1) The Operating System as an extended machine.

The Operating System hides the internal details of the hardware from the programmer and presentshim with a virtual system or view, which concentrates on data as named files. The operating systemalso hides the user from a number of unpleasant tasks concerning interrupts, timers, memorymanagement and other important functions at the lower level.2) The Operating system as a resource manager.

Todays computer is made up of a number of components such as processors, co-processors,memories, various drives, network interfaces, printers, modems and so on. The aim of the operatingsystem is to provide an orderly controlled allocation of the various resources among the variousprograms competing for them.

3) The Operating System as a Guardian and Accountant.

The Operating System is a Guardian, to perform a number of specialized tasks in a predefined order.The present day systems may have to perform more specialized tasks, which are highly complex. TheOperating System is also responsible to provide proper access controls so that users do no interferewith each others programs and also the operating system is restricted from unauthorized access..

DOS (DISK OPERATING SYSTEM)

CP/M (Control Program for Microcomputers) developed in 1974 by Gary kildal of DigitalResearch was the first most popular OS. Simultaneously a number of other companies also startedOSs. This created a problem of incompatibility. IBM at this time approached Bill Gates the owner ofa small company called Microsoft to develop an OS similar to CP/M. The agreement was that IBMwould use it as PC-DOS and Microsoft could sell it as MS-DOS.

MS-DOS created in 1980 became so popular that many companies started producing hardwarefor this software. Disk Operating System is so called because much of its work involves managingdisks & disk files and also the fact that it physically reside on the disk.Structure of MS-DOS

MS-DOS is structured in three ways.i. BIOS (Basic Input Output System)ii. Kerneliii. The Shell (Command.com)i. BIOS: Contains a collection of low-level device drivers, which isolates MS-

DOS from details of the Hardware. The file IO.sys is present in all MS-DOS Systems, and isloaded immediately after booting and contains a module, which is used to boot the system one,which isolates kernel from hardware details.

ii. Kernel : The Kernel is present in another hidden file MS-DOS.SYS. Kernelcontains the machine independent part of the Operating System. It mainly handles processmanagement, memory management, file system and interpretation of all systems calls.

iii. The Shell (COMMAND.COM): Most people feel the shell as the operatingsystem but in reality it is not so, in fact it is actually not a part of the operating system and can be

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replaced by the user program whenever the user programs need memory. It is a commandinterpreter.

How MS-DOS organizes Information?

MS-DOS organizes information through files, directories and drives.File : A file is collection of related information stored by DOS under a single

name. The file name consists of the root name (1 to 8 characters) alsoreferred to as Primary name, a period(.) and the extension (1 to 3 characters).The extension is optional.

Directories : A group of files can be stored under a unit called as a directory. Storinggroups of files in different directories makes files easier to find.

Current Directory : The directory you are in is called the current directory.eg . C:\Computer>

Sub-Directory : A directory within another directory is called a sub-directory.Root Directory : All directories are sub-directories, except for one, which is called the root

directory. The root directory is the starting point from which all otherdirectories braches out. The root directory does not have a name. Instead, it isrepresented by a backslash (\).

eg. C :\>Computer

unit1chapter1

unit2Kannada

Drives : Drives are usually associated with a piece of hardware called a disk. Themost common types of disks are the hard disk, which is inside yourcomputer, and the floppy disk and compact disc, which you insert into slot inyour computer.

A drive is a grouping of all the directories on a disk. A drive is named with asingle letter. Generally A drive refers to as Floppy disk drive & C driverefers to as Hard disk.

Command Prompt: C:\>_This is called command prompt. The flashing underscore next to thecommand prompt is called the cursor. The cursor shows when the commandyou type will appear.

DOS COMMANDS

DOS commands can be classified into two types.1) Internal commands2) External commands

Internal Commands: DOS supports the user of about 25 commands. Some of these commands are inbuilt into a program called as COMMAND.COM. This program is automatically loaded into thememory when the computer is started. These commands can be directly executed. Such commands arecalled as internal commands.

External Commands: DOS supports the use of about 45 additional commands. These commands areprovided as separate programs. Each program represents a command. To execute the command the

name of the program has to be typed at the prompt along with its arguments. Such commands arecalled as external commands.

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INTERNAL COMMANDSDIR : This command gives a listing of the files & directories on a disk.

C:\>dirCOPY CON : This command is used to create a new file. If an existing filename is given, then the

previous file is lost.C:\>copy con filename------------------------- ^zCtrl+Z (^Z) is used to save the file.

TYPE : This command is used to display the contents of a text file to your screen.C:\> type filename

DEL : This command is used to delete a file or a group of files from the disk.C:\>del filename

MD : Create or make a new directoryC:\>md tumkur

CD : Change or moves the user from the current directory.C:\>cd tumkurC :\> tumkur>

CD.. (go to the previous or parent directory)C:\>tumkur>cd..

C :\>COPY : Copy from one file to another file. It does not remove the source file after

writing the new file.C :\> copy file1 file2

RD : Remove or delete a directory. You must empty the directory to be deleted firstor you will just get an error message.

C:\>rd tumkurVER : This command tells us the version of DOS which we are using.

C:\>verREN : This command renames a file on the disk. The old & new names have to be

specified.C:\>ren file1 newname

VOL : This command tells you the volume label of your hard drive or floppy disk. Itwill also give you a serial number too.

C:\>volDATE : This command is used to display or change the system date.

C:\>dateTIME : This command lets you set your systems time.

C:\>timeCLS : Clear the screen. It also places your cursor at the top left-hand corner of your

screen also called the home position.

C:\>clsPROMPT : This command is used to set your command prompt. If you use it by itself yourprompt will change to just C> form C:\>

C:\>prompt $p$gChanges the prompt to the default type which include the path ($p) and thegreater than symbol ($g) in it.

Some of the other variations which can be used with the command are$$ adds a $ to your prompt $t states the date$p lists your current directory and drive letter$g the > character $l the < character

$q the = character $b the | character $v adds your DOS version $n lists just your current drive

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EXTERNAL COMMANDSATTRIB : This command either Displays or Changes file attributes.

C:\>attrib +r filenameThe options used in the syntax include.

+ sets an attribute

- clear an attributeR Read-only file attributeH Hidden file attribute

CHKDSK : This command analyzes disk or diskette and displays a disk and memory statusreport.

C:\>chkdsk[dirve name:] [/f] [/v]FORMAT : This command Prepares a diskette or drive for use by DOS. The successful execution

of the command deletes all the previous data and prepares the disk as if it is a newdisk for use.

C:\> format [drive name :]DISKCOPY: This command makes an exact copy of a diskette, including hidden system files if they

are presentC:\> diskcopy A B

XCOPY : This command is designed to copy the contents of entire directories, alongwith all of their sub-directories, and all of the files contained in those sub-directories.

C:\> xcopy directory1 directory2

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