computer fundamental

COMPUTER SCIENCE

Computer Science is the study of the operating principles of computers, computer programming languages and algorithms for solving theoretical as well as practical problems. It involves the development and use of devices for processing information. It also deals with advantages and disadvantages of computer, its features, applications field and its impact on the society. Information in one form is presented to the device (input information) and information in other form is acquired from it (output information). This process of conversion of raw material into the refined form is nothing but the data processing. Data Processingmay be defined as the process of transforming data (raw material of information) into useful information by the computer.

WhatisComputer?

The term ‘Computer’ is derived from the Latin word ‘Computare’, this means to calculate.

Computer is an advanced electronic device which takes raw data as input from theuser and processes these data under the control of set of instructions (called program) and gives the result (output). It also saves output for the future use. It can process both numerical and non-numerical (arithmetic and logical) calculations.

In other words, computer is a programmable machine that stores and retrieves data and performs high speed logical and mathematical operations. The working principle of computer can be summarized as input, process and output cycle.

IPOCycle:

Input(Data):

Input is the raw information entered into a computer from the input devices. It is the collection of letters, numbers, images etc. Keyboard, Mouse, Scanner, Digital/Web Camera, Joystick etc. are some of the input devices.

Process:

Processistheoperationofdataaspergiveninstruction.It is totally internal process of the computer system. CPU (Central Processing Unit) is the main Processing Device.

Output:

Output is the processed data given by computer after data processing. Output is also called as Result. We can save these results in the storage devices for the future use. Monitor (Screen) and Printer are the major Output Devices.

CHARACTERISTICS OF COMPUTER

SPEED:

Computer performs complex calculation at avery high speed. This speed varies from a few micro second to nanoseconds. This is the major factor, which is mainly responsible for the development of computers.

FractionsofaSecond:

1 Millisecond      =    1/1000thofaSecond(10-3)

1 Microsecond    =    1/1000000thofaSecond(10-6)

1 Nanosecond    =    1/1000000000thofaSecond(10-9)

1Pico Second     =    1/1000000000000thofaSecond(10-12)

Accuracy

Computers are very accurate. We know that the computer perform any task under the set of instruction called program. So, it does not do anything without program. Thus, it can perform any operation accurately.

Computer always gives 100% actual output (result), if the user provides correct input and instructions. If any mistake occurs in any calculation they are due to manual error but not of computer. Since it is 100% accurate, it is reliable.

Storage capability:

Thecomputershavetheabilitytostoreahugeamountofdatainitssecondarydevices like floppy and hard disk. The stored information also can retrieve immediately. This helps in analyzing data and taking quick decisions. The storing capacity of computer is expressed in Bytes. Normally one byte stores one character of data.

0, 1	=	1 Bit
4 Bits	=	1 Nibble
8Bits(2 Nibble)	=	1 Byte
1 Byte	=	1 Character
1024Byte	=	1KB(KiloByte)
1024KB	=	1MB(Mega Byte)
1024MB	=	1GB(GigaByte)
1024GB	=	1TB(TeraByte)

Versatility:

Computers are being used in different fields such as offices, schools, hospitals etc. to perform various tasks. Versatile means ability to perform various task and computer can capable to do so. A computer can process any kind of data.

Diligence:

Diligence is a capability of performing repeated operation without any tiredness and any mistakes. A computer is capable of performing the required task continuously with the same speed, accuracy and efficiency without any error. This characteristic of computermakes it useful for repetitive jobs like process control and quality control.

Reliability:

Computer output is generally very reliable, if the input data and instruction is correct. Incorrect data and unreliable programs give us computer errors and wrong results.Sincethe computer is 100% accurate, it is reliable.

Indescribablebenefits:

Many organizations and companies use computers for indescribable benefits such as flexibility, business growth and the psychological factor for attracting consumers to buy their products or services.

USES OF COMPUTER

Computer, one of the most powerful machine today, is being used everywhere. Let’s discuss the uses of computer on various sectors of our society.

Business and Industry:

The uses of computers in business/offices improve their working efficiency. Record keeping becomes very easy. Information can be searched immediately. The use ofcomputers in industries has improved their efficiency. The cost of production goes down. The quality of products is improved. Unpleasant and hazardous work can be performed by using robots. Working hours of laborers are reduced; they get more leisure.

HealthCare:

Computers are also being used for planning and control purposes by health-care professionals. Computer equipment is used to monitor pulse rate, blood pressure and other vital signs. This leads to correct and fast diagnosis. Medical researchers are using computers as a tool in their search for cures of deadly diseases like Cancer and AIDS.

Education:

Computers are playing an important role in education. Once can get lessons on certain topics, special lectures prepared by experts etc on the screen as many times as he wants until he understands the topic. Computers are working as teachers or helping teachers in educational institutions.

Communication:

Computers are capable of manipulating and transmitting texts at very fast rate. Sitting at home, anybody may do office work, bank transactions, marketing, purchase of shares, reservation of place and bus tickets and so on. Officers and managers can contract any branch office anywhere in the world through the computer network. Text, voice, data and picture can easily be transmitted nowadays using modern communication systems, which heavily depend upon computers. Information is transmitted over long distances through satellites.

Humanities:

Inrecentyears,computershavebecomepopularamongpeoplehavinginterestsin history, literature, music, graphics, arts and other branches of humanities.

ScienceandTechnology:

Thousands of scientific applications are processed daily, on the computers. One of the most important daily activities is weather forecasting, which involves solution of mathematical equations using worldwide data about air pressure, temperature, humidity and other values.

RecreationandEntertainment:

Our entertainment and pleasure-time have also been affected by computerization. For example:

i)        In movies, computer generated graphics give freedom to designers so that special effects and even imaginary characters can play a part in making movies, videos, and commercials.

i)        In sports, computers compile statistics, sell tickets, create training programs and diets for athletes, and suggest game plan strategies based on the competitor’s past performance.

i)        In restaurants, almost every one has eaten food where the clerk enters an order by indicating choices on a rather unusual looking cash register; the device directly enters the actual data into a computer, and calculates the cost and then prints a receipt.

Government:

Various departments of the Government use computer for their planning, control and law enforcement activities. To name a few – Traffic, Tourism, Information & Broadcasting, Education, Aviation and many others.

DISADVANTAGESOFCOMPUTER

We see that computers have great impact on our society. They are even changing the way we work. There are certain disadvantages also. There may be cases of misuse in banks, leakage or misuse of personal information, etc.

When a person is using computer for marketing, office work, collection of information, etc. his activity is recorded. One can misuse this record. So individual privacy is not guaranteed. Someone can play misbehave on computer. He can erase certain importantdata. He may take away some important and private data. Extensive use of computers for the job, which is labor oriented, will cause unemployment. But in industries computers canbe used for machine control and process control etc. for which earlier electronic or electromechanical control systems were employed. Such applications of computer do not much affect labor employment.

HISTORYOFCOMPUTER

The history of computer starts from 4000 years ago. History of computer means the gradual change in the concept over a long period of time. Around fifth century, Hindu philosophers developed a new method of counting from 0 to 9. Counting the numbers from 0 to9canbeperformedwiththehelpoffingers.Thedevelopmentofcountingstartedfromthe development of simple counting device called ABACUS.

Abacus:

It is the early counting and calculating device that was developed by the Chinese people. The ABACUS was first used forcomputationsin3000B.C.Itwasmadeofawoodenframe on which there were strings. The frame was divided into two parts, heaven and earth, by a mid-bar. Each string in heaven had two beads each having the value of five units and each string on thee arth had five beads each having the value of one unit. During the calculation, the beads were shifted to the mid-bar. It also followed the place value system. It was used to add, subtract, divide and multiply.

Napier’s Bones:

In 1614 AD, a Scottish mathematician John Napier discovered the concept of Logarithms. In 1617 AD, he constructed a set of rods called Napier Bones fordoing mathematical calculation easily. It consisted of eleven sets of bone rods on which the numbers were engraved. It was used for multiplication. It was based on the principle of performing multiplication by the addition of logarithms.

Slide Rule:

Aftertheinventionoflogarithmin1617AD,William

Oughtred invented the Slide Rule in 1620. This device was made on the principle of logarithms. This device consists of two graduated scales, one small and other larger one.One of the scales passes over the other. It was used calculation product and quotient. The calculation was done by sliding the smaller scale over the large scale and the result was obtained by viewing the scales.

The Slide Rule was used by the engineers till 1970s. This was replaced by pocket calculator.

Pascal’sCalculating/AddingMachine:

It was developed by Blaise Pascal in 1642. It was a mechanical calculator that used toothed wheels and gears. The numbers were written on the wheels and the calculation was done by dialing the numbers. It was also called as Pascaline. It was used to add, subtract, multiply and divide.

Leibniz’sCalculator:

It was made by a German philosopher Gottrified Wilhem von Leibniz (G.V. Leibniz) in 1671 AD. It was based on Pascal’s principle. But it used gears, toothed wheels and drums. It was able toadd, subtract and even find square roots. It worked ontheprinciplethatmultiplicationanddivisioncan

be done by repetitive addition and subtraction of numbers. It was also called as Stepped Reckonor.

Difference Engine:

In 1822 AD, an English mathematician (Professor of Mathematics at Cambridge University) invented a machine called Difference Engine with mechanical memory to store results. It was based on the difference tables of squares of the numbers. Due to which it got its name as Difference Engine.

AnalyticalEngine:

It was also developed by Charles Babbage in 1830s. It consisted of the input unit for taking data and instructions, mill for performing calculation, memory (punched card) with a suitable output device that was used in giving the final result. It was designedtocalculateupto20decimalplaces.Thesameprincipleof AnalyticalEngineisusedinthemoderncomputer.Soheiscalledas the “Father of Modern Computer”. Using the principles ofCharles Babbage, about 100 years later, Mark-I was developed by Howard Aiken in 1937.

The analytical Engine was never completed due to the lack of techniques and technology because of which he was unable to get all the parts that he wanted in his machine.

LadyAugustaAdaLovelace:

OneofthegreatsupportersofCharlesBabbagewasLadyAugustaAda (the daughter of famous poet, Lord Byron). She convinced Babbage to use binary concept in his Analytical Engine. She wrote different types of programs that were used in the Babbage machines. So she is rememberedas the “First Programmer” in the history of computer science and has to her credit a computer language called ADA named after her.

Dr.Herman Hollerith:

He was the first person to use punched card practically on his Census Tabulating Machine in 1880s. The information is stored as holes in cards, which are interpreted by machines with electrical sensors. The cards were punched by a machine called Punched Card Machine or Hollerith’s Tabulating Machine. Then he established Tabulating Machine Company to sell his products. Later, when other companies merged with TMC, new company were established under the name International Business Machine Company and he became the founder of IBM. It is the worlds leading computer manufacturer.

MARK-I(HowardAiken):

In the late 1930s, next important event was added in the History of computer; the electromechanical computer was born with the development of MARK-I in 1944 by Howard Aiken with the help of IBM. It also used the punched cards designed for Difference Engine. It was 51 ft long, 8 ft high and 13 ft wide. It used large numbers of valves, switches and resistors. It was used to produce ballistics tables in 2nd world war.

ElectronicNumericalIntegratorandCalculator(ENIAC):

It is the first electronic computer that was developed by John Mouchlay and J. Prisper Eckert in 1947. It was based on the decimal number system. 18,000 vacuum tubes were used in ENIAC. There were 70,000 resistors, 10,000 condensers and 6,000 switches. It weighed 30 tones and occupied a space 3,000 cubic feet. It could calculate 300 times faster than any calculating device at that time and it was based on decimal number.

ElectronicDiscreteVariableAutomaticComputer(EDVAC):

In 1949, the first electronic computer was developed by John Mauchly and John Presper Eckert with the help of A. Burks, Goldstine and Neumann. This machine was used to store the data and information as well as the instructions. This computer operated electronically.

UNIVAC-I(UniversalAccounting Computer):

John Mauchly and Eckert founded their own company in 1946 and began to work on the Universal Automatic Computer (UNIVAC): general-purpose commercial computer in1951. It was the first commercially used electronic computer in the world.

·        In1977,SteveWozniakandSteveJobsestablishthecompanyAppleComputers.

·        In1984, Appleintroduces theMacintosh, thefirstwidely availablecomputer witha “user-friendly” graphical interface using icons, windows, and a mouse device.

·        In1989,MicrosoftCorporationintroducesWindowsforIBMComputers.

GENERATIONOFCOMPUTER

Depending on the device used, system architecture, processing mode and language used in the computers are categorized in the following five generation. The development of different types of memory devices has given a sequence of development of computers from mainframe to microcomputers. In the development of computers there is lot of change from 1946 to 1990. This time is divided in different generations by scientists in a conference in 1962.

FirstGeneration(1946to1954):

Introduction of the UNIVAC I in 1951 marked the beginning of the first generation. They began to work on the Universal Automatic Computer (UNIVAC) in 1946; so we can considered the duration of First Generation starts from 1946. The computers using vacuum tubes as a memory unit are known as first-generation computers. The vacuum tube consumes a lot of power. The Vacuum tube was developed by Lee DeForest in 1908.

VacuumTubes

Features:

1.    Theyusedvalvesorvacuumtubesastheirmainelectronic component.

2.    Theywerelargeinsize,slowinprocessingandhadlessstorage capacity.

3.    Theyconsumedlotsofelectricityandproducedlotsofheat.

4.    Theircomputingcapabilitieswerelimited.

5.    Theywerenotsoaccurateandreliable.

6.    Theyusedmachinelevellanguagefor programming.

7.    They were very expensive. Example:ENIAC,UNIVAC,IBM650etc

SecondGeneration(1955to1964):

The invention of Semi-conductor transistor had made big revolution in the field of computer. The transistor replaced the Vacuum tube. The second-generation computers used transistors as a memory unit. A transistor could do the work of 1000 vacuum tubes. Second generation computers are smaller in size. They are more reliable and faster than the first generation computers. Assembly language was used for programming in second-generation computers.

Transistor

Features:

1.    TransistorswereusedinsteadofVacuumTube.

2.    ProcessingspeedisfasterthanFirstGenerationComputers(MicroSecond)

3.    SmallerinSize(51square feet)

4.  Theinputandoutputdeviceswere faster.

Example:IBM1400and7000Series,ControlData3600etc.

 

ThirdGeneration(1965to1974):

By the development of a small chip consisting of the capacity of the 300 transistors called Integrated Chip (IC). The computers, using ICs are of the Third Generations. They were smaller in size and had higher efficiency in speed & memory capacity. Very soon ICs were replaced by LSI (Large Scale Integration), which consisted about 100 components. An IC containing about 100 components is called LSI.

 

IntegratedCircuit(IC)

Features:

1.    TheyusedIntegratedCircuit(IC)chipsinplaceofthetransistors.

2.    Semiconductormemorydeviceswere used.

3.    Thesizewasgreatlyreduced,thespeedofprocessingwashigh,theyweremore accurate and reliable.

4.    LargeScaleIntegration(LSI)andVeryLargeScaleIntegration(VLSI)werealso developed.

5.    Theminicomputerswereintroducedinthisgeneration.

6.    Theyusedhighlevellanguageforprogramming. Example: IBM 360, IBM 370 etc.

FourthGeneration(1975to1990):

An IC containing about 100 components is called LSI (Large Scale Integration) and the one, which has more than 1000 such components, is called as VLSI (Very Large Scale Integration). The computers designed using VLSI, as a memory unit is known as Fourth Generation Computers. The first microprocessor 8008 was developed by American Company (Intel Corporation) in 1971 and in 1974; another more powerful microprocessor 8080 was developed. The microprocessor 8080 was used in early XT computers. Microprocessor based computers fall in fourth generation computer group. VLSI is also called as microprocessor.

VLSI(VeryLargeScaleIntegration)

Features:

1.    TheyusedMicroprocessor(VLSI)astheirmainswitchingelement.

2.    Theyarealsocalledasmicrocomputersorpersonal computers.

3.    Theirsizevariesfromdesktoptolaptopor palmtop.

4.    They have very high speed of processing; they are 100% accurate, reliable, diligent and versatile.

5.    Theyhaveverylargestoragecapacity. Example: IBM PC, Apple-Macintosh etc.

FifthGeneration(1990-presentandfuture):

The fifth-generation computers are under development stage. These computers are being made using microprocessors and will use USLI (ultra-large-scale integration) chips (BIO-Chips) in the future. Such computers will use intelligent programming and improved human-machine interfaces. It is estimated that these computers of fifth generation will have an Artificial Intelligence (AI) with a little thinking capacity and they will understand the natural languages like English, Japanese etc.

 

        

Microprocessor                          ModelofFifthGenerationComputer

Features:

1.    Theyarethefuturecomputerswhichwilluseparallelprocessororgeneticallyengineered bio-chips as their main switching element.

2.    TheywillhaveArtificialIntelligence(AI)andwillbeabletounderstandnatural language.

3.    Theywillhaveextremelyhighefficiencyandreliability.

CLASSIFICATIONOFCOMPUTER

Computerscanbeclassifiedintovariousclassesaccordingtotheirfollowingfactors.

1.    OnthebasisofWorkingPrinciple

a)  AnalogComputer

Analog computer measures continuous types of data and uses a physical quantity like, electric current, voltage, temperature etc. to present and process the data. We have seen many Analog devices in our life. It represent numbers by a physical quantity; that is, they assign numeric values by physically measuring some actual property, such as the length of an object, an angle created by two lines, or the amount of voltage passing through a point in an electric circuit. Thermometer, Multimeter, Speedometer, Fuel & Price Indicator in Petrol Pump are the examples of Analog devices. They are special purpose computers.

 

b) DigitalComputer

The computer which accepts discrete data (discontinuous data) as per the electric signals is known as digital computer. Basically, digital computer counts digits, which representnumbersorletters.Theyarethemost

widelyusedtypeof computers.

Thecomputersbasedonbinarydigitsi.e.0and

1 are called digital computer. It represents each and every information (number, letter & other special symbols) in terms of single numbers (0 and 1) and processes these information by using standard arithmetic operations. 90% of the computers are digital computers. They are general purpose computers.

c)  HybridComputer(Analog+Digital)

Hybrid computer is the combination of the features of Analog and Digital computers. IthasbothfeaturesofAnalogandDigital computer.ItcandoalltypesoftasksofDigitaland Analog. They are mostly used in scientific research, industrial application, aeroplanes etc. They are special purpose computer.

2.   OnthebasisofSize

a)  MainframeComputer

Mainframe Computers are large computers which processes at high speed and occupies a large space. This has a large capacity to handle huge numbers of records. More than100peoplecanworkatatimeandcommunicatewithdifferentcountrieswithWideArea Networks via satellite. They are generally used in large scale organizations and government offices for large-scale data processing. Such computers can be seen in the Universities, Institute of Engineering, and Scientific research centers.

MainframeComputer

MainframeProcessor

Inoneword,alargecomputer,usuallydesignedtoserveanumberofremoteterminals is called Mainframe Computer.

 

b) MiniComputer

Mini Computers are medium in size than Mainframe computers but larger than microcomputers. They are less powerful than Super and Mainframe but morepowerfulthan micro computes.They arespecially

used in data processing, Programming,Desktoppublishing fields. In other words, acomputer smaller than a mainframe and larger than a microcomputer, intended to support multiple users is called Mini Computer.

c)  MicroComputer

Micro Computer is also known as Personal Computer or Home Computer. They are made by using microprocessors. They are widely used at homes and offices. Many brands, models and sizes are available in microcomputers. They are used in many fields of business, education, desktop & graphics designing, data processing etc.

In other words, a small computer driven by a single integrated circuit and designedfor use by one person is called Micro Computer. It is also called PC.

Microcomputerscanbesubcategorizedinto:

i.     DesktopComputer:apersonalormicrominicomputersufficienttofitonadesk.

ii.    Laptop Computer: a portable computer complete with an integrated screen and keyboard. It is generally smaller in sizethan a desktop computer and larger than a notebook computer.

LaptopwithTouchScreen                           LaptopwithTrackBall

 

iii.   PalmtopComputer/DigitalDiary/Notebook:ahand-sizedcomputer.Palmtops have no keyboard but the screen serves both as an input and output device.

d) SuperComputer

A computer that is capable of working at very great speed, and can thus process a very large amount of data within an acceptable time. Super computers are used in designing complicated machines as supersonic jets, space research, and picture composition for movie films, and for weather forecasting. Super Computers have the largest, fastest and most expensive systems in the world.

CRAY-I/II/III,CYBER-205,HITACHI-810/20aresomepopularSuperComputers.

    

CRAY-ISuper Computer

3.   OnthebasisofBrand

a)  IBMPC

The computers manufactured by IBM (International Business Machine) company are calledIBMComputers.ThemicrocomputersofIBM CompanyarecalledIBMPC.IBMisoneof the leading company in computer industry.

IBMPC

b) IBMCompatible

Computers, developed on the principles of IBM Computers are called IBMCompatible. It can perform all the tasks that an IBM computer does. They are less expensive than original (IBM) computers.

In other words, a personal computer that is compatible with the IBM PC is called IBM Compatible Computer.

c)  Apple/Macintosh

The computers manufactured by the Apple Company are called Apple Computers. They are specially used in Desktop-Designing. They are quite expensive than IBM and IBM Compatible.

TheOperatingSystemandotherperipheralsarecompletelydifferentthanIBMand IBM Compatibles.

COMPUTERARCHITECTURE

COMPUTERSYSTEM

 

All of the components of a computer system can be summarized with the simple equations.

COMPUTERSYSTEM=HARDWARE+SOFTWARE+HUMANWARE

·        Hardware=InternalDevices+PeripheralDevices

Allphysicalpartsofthecomputer(oreverythingthatwecantouch)areknownas

Hardware.

·        Software = Programs:

Softwaregives"intelligence"tothecomputer.

·        Humanware= User

Hardware

The physical parts of the computer, which can be seen and touched is known as Hardware. It is just the mechanical parts of the Computer. All the devices attached to the Computer system like: Mouse, Keyboard, Monitor, CPU, Motherboard, Hard Disk are hardware. It includes all the components used to make the computer. It also includes the cables, connectors and computer peripherals.

Software:

Software, simply are the computer programs. The instructions given to the computerin the form of a program is called Software. Software is the set of programs, which are used for different purposes. All the programs used in computer to perform specific task is called Software.

TYPESOFSOFTWARE

ComputerSoftwareisbasicallycategorizedintothreetypes:

1.     SystemSoftware

2.     ApplicationSoftware

3.     ProgrammingLanguage&Scripting

1.  System software:

The software that control and direct the operation of the computer hardware is called system software. System software is the collection of the programs written for computer, which allows the user to develop and run programs. The system software starts up the computer, makes it ready and allows the user to work on different program.

ThesystemsoftwareconsistsofOperatingSystemandUtilitysoftware.

a) OperatingSystemSoftware:

An operating system is a set of programs that controls and supervises a computer system and provides services to computer users. Operating system software controls overall activities of the Computer. It acts as an interface between a user, program and thehardware. DOS, UNIX, XENIX, Windows are the examples of Operating System.

b)  UtilitySoftware:

The software, which helps the users to manage files & folders, checking viruses, keeping PC healthy and system settings is called Utility Software. These are also thesoftware tools which help to users while preparing programs. PC TOOLS, Scandisk, Disk Defragmenter, Norton Antivirus, Language Processors (Assembler, Compiler…) are the examples of Utility Software.

LanguageProcessors:

The programs that translate the program written in high level and low level language to machine codes are called language processors.

Assembler:It translates the programs written in low level language (assembly) to machine code.

Compilers:It translates the programs written in high level language to machine codes. The compiler translates the whole program at a time thatmakes the execution faster.

Interpreter:Italsotranslatestheprogramwritteninhighlevellanguageto machine codes. Unlike compiler, it translates a single statement of a program at a time. Due to this it is easier to locate errors and debugging becomes easier.

2.  Applicationsoftware:

The software used for special purpose (specific task) written in a specific language is known as Application Software. It also may be defined as software that acts as interface between the user and the system software to allow the user to perform specific tasks. These programs perform certain task with respect to related program. Basically, there are twotypes of Application Software:

a)   PackageSoftware

This software is the set of the pre-written programs by another person or group and made available to computer users. Many kinds of related works can be performed by using any required software. Ms. Word, Ms. Excel, Ms. Access, Adobe PageMaker, Auto Cad are the examples of Package Software.

b)  TailoredorCustomSoftware

The tailored software are used to perform the specific tasks only like Accounting, Super Market Billing, Mark sheet Preparation, Inventory Control etc. They are developed on demand of the clients. GMACC, Point of Sale, MEDI-PRO, TALLY etc. are the examples of Tailored Software.

3.  ComputerProgrammingLanguages&Scripting:

A languageisaset ofcodes, whichareused towritethe programs. Therearebasically two levels of programming languages. These are:

a)  LowLevel Language

i)  MachineLevel Language

ii)  AssemblyLanguage

b)  HighLevelLanguage

a)  LowLevel Language

i)  MachineLevelLanguage:

This is computer's language. Computer understands information composed of only zeros (0s) and ones (1s) and hence it uses binary digits for its operation. Programs, written in machine language only understood by the computer. The programming in this language is highlycomplicated.So,onlysoftwareexpertsandonlyonepersonnelrelatedtoinnersystem can program in this language. These program codes or statements can be loaded directlyinto the computer's memory. Today, programs are written in special programming language, but these programs must still be translated into the machine language before the program can be executed.

ii)  AssemblyLanguage:

The writing of programs in machine language is very difficult, tiresome and boring job for a programmer. To solve this problem and to facilitate programmer, easily understandable languages have been developed. Assembly language is one of them. Programs can easily be written in alphanumeric symbols instead of 0s and 1s. Meaningful and easily rememberable symbols are selected for this purpose. For example, ADD for addition, SUB for subtraction, CMP for comparison etc. Such symbols are known as mnemonics. A program written in mnemonics is called assembly language program. The writing of programs in assembly language is easier and faster as compared to the writing of programs in a machine language. However, programming in this language must be translated into machine language beforethe program can be executed. An Assembler is a program, which converts this language into the machine code. So it is also sometimes called Assembly Language.

b) HighLevel Language:

These types of language are written in English Language with set of rules, called Syntax. Thus, itis easier to program than the other languages. These are easy to write, read and understand. Mistakes can be easily found and corrected in this language. Programs in this language also must be translated into machine language before the program can be executed. A Compiler is a program, which translates into binary digits (i.e. machine language).COBOL(COmmonBusinessOrientedLanguage),FORTRAN(FORmula

TRANslation),BASIC(Beginner'sAll-purposeSymbolicInstructionCode),C,C++etc.arethe examples of High Level Language.

Theadvantagesofhigh-languagesare:

i.        Theyareeasiertolearnascomparedtoassembly languages.

ii.       Theymakeprogramseasierandfastertowrite.

iii.      Providebetterdocumentation.

iv.     Theprogrammerdoesnothavelimitationstouseasingletypeof machine.

v.      Programsareportable,i.e.theywillrunonanycomputer,whichhasasimilar compiler.

BASIC:It is a group of similar high-level programming languages whose name is derived from the words Beginners All-purpose Symbolic Instruction Code. BASIC was developed in the mid 1960s. It is a simple programming language, is easy to learn. It allows easy modification of programs.

FORTRAN: It is the short form of FORmula TRANslation. It is the first high-level computer language developed over the period 1954 to 58. It is especially used in the field of science and engineering. FORTRAN is a structured language.

C: C is a general-purpose high-level programming language. It was developed by Dennis M. Ritchie in 1970’s. It is used to write any kinds of operating system and application software.

C++: The C++ is a superset of C language. It is an Object Oriented Programming Linage. It is an advance form of C and used to write various programs.

Visual Basic: Visual Basic is a very powerful program developing tools (not a pure programming language) that is especially used to design windows based programs. It was developed by Microsoft Corporation, USA.

There are lots of other programming languages like Java, C#, SQL etc.. used inspecific purposes.

Humanware/Liveware:

Person, who operates (handles) computer and its periphery, isknown as Human ware. It is also sometimes called User / Operator. A Computer is a totally user dependent device. It does not have its own brain, so it cannot work itself. So, a set of sequenced instructions is the soul and the user is the heart of the computer system.

MEDIA,DEVICES&PERIPHERALS

COMPUTERDEVICES

 

Different input, output and auxiliary devices that are connected with the computer are called computer devices. The different devices that help to input, output, store etc in the computer is called as computer media and peripherals. Peripheral devices are connected to the computer through ports, or sockets, that are mounted outside. Some peripherals (e.g. disk drives) are located inside the computer case, so they are connected viaexpansion slots.

The number of computer peripherals differs according to the requirement. Some computer media, devices and peripherals are discussed below.

THECASEANDPOWERSUPPLY UNIT

Casing

ThePCconsistsofacentralunit(referredto asthe computer)andvariousperipherals. The computer is a box, which contains most of the working electronics. It is connected with cables to the peripherals. Here is a picture of the computer:

 

                 

Casing is the outer look of the CPU box. Selecting the case unit is mostly a matter of deciding for a style. In broad terms there are two types of cases:

i.      DesktopModel (Flat)

ii.    TowerModels

Desktop(Flat)andTowerModelCasings

Both types of cases vary by size and profile. Whereas the desktop case sits (as the name implies) on the desktop, the tower case is designed to stand upright and can be much larger.

Before choosing the case we should think about our location requirements for computer. If we need a simple office machine then we might decide for a desktop style. If, however, we want to keep our options open for upgrading the computer at a later stage, maybe by adding more hard drives or other devices, then we might consider a tower with more room for add-ons.

PowerSupply:

A power supply is the heart of the computer system. The computer’s components would not be able to operate without power. A computer needs a well regulated 5-volt to 12 volt DC power supply for the proper functioning of its various parts.

SMPS-SwitchModePowerSupply

The power from the mains is 220 volts AC current, witha lot of interference, so, it cannot be directly fed to the computer. A SMPS is used in between the Computer and the mains to convert the 220 V AC Current to a well regulated 12 Volt and 5 Volt DC Current [+5 volts DC (RED wire), -5 Volts DC(ground,BLACKwire),+12VoltsDC(YELLOWwire),and–

12 Volts DC (ground, BLACK wire)]. Usually, the electronic components and circuits in the system (motherboard, adapter cards and disk drives, logic boards etc.) use the 5 Volt power andthemotorsinthediskdrivesusethe12Voltpower.The

power supply of the computer must ensure a proper, good and steady supply of both typesof current to the system, so that the complete computer system can operate properly.

APowerSupplyhasthreetypesofconnectorsusedtopowerthevariousdeviceswithin the computer. These are:

i)       FloppyDrivePowerConnectors(Bergconnector)

ii)      MolexConnector(HardDisk,OpticalDisks)&,

iii)     System Connector[P8&P9(6+6pins);forthemotherboardpowersupply.Make sure that all the black wires from both P8 and P9 are at the center facing each other.]

Thebackofpowersupply(SMPS)containsthreethings.Theyare:

i)       TheComputer’sPowerConnector

ii)      TheMonitor’sPowerConnector

iii)     TheExhaustFanPort

UninterruptiblePowerSupply(UPS):

We know that, Computer is an electronic device so Electricity is compulsory requirement to operate it. Each and every components of computer can sustain a fixed current capacity so; fluctuation of voltage may damage these components. That’s why; we have to use UPS, Volt Guard, Stabilizer etc. to maintain the voltage fluctuation.

UPS is a device that stores the electricity and supply to the computer automatically incase of electricity failure. It is used in computer to prevent the loss of data and damage of computer parts caused due to electricity failure.

INPUTDEVICES

INPUTDEVICES

 

Devices which transfer data, programs, or signals into a computer system are called Input Devices. These devices are used to give raw data (input) to the computer to perform the specific tasks. Firstly, the data, programs, or signals are fed into the input devices in a suitable form, and are then converted by the device into electrical signals from human- readable format that are transmitted to the central processing unit of the computer. Some input devices are as follows:

 

·        Mouse	·        Keyboard
·        Scanner	·        Digital Camera
·        Web Camera	·        Joysticks
·        Track Ball	·        TouchScreen
·        LightPen	·        OCR
·        BCR	·        MICRetc.

Mouse

The mouse is an input device that is used to give thecommand and sometimes input to the computer. It is a small box with a round ball at the bottom and more than one buttons on the top. It is held in one hand and moved across a flat surface. Movement of the mouse on a flat surface moves the ball which in turn controls movement of a cursor on the monitor. In addition to moving the cursor, the mouse can be used to select text or commands and to manipulate data on the screen by clicking the buttons.

Based on the method used to interface or to connect the mouse to the main computer system, mouse can be divided into following categories:

Serialmouse

A mouse that connects to a computer via a serial port is a Serial Mouse. This is the simplest type of connection.

A serial mouse is connected to either COM1 or COM2, i.e. any one of the available serial port on the computer. Connecting a serial mouseisveryeasyasoneneedtojustpluginthe connectorattached to the mouse wire to the vacant serial port on the computer. It has 9 pin and D type in shape.

PS/2mouse(BusMouse)

The other common type of mouse is a PS/2 mouse, which plugs into a PS/2 mouse port. Only difference between a bus mouse and a serial mouse is a serial mouse is connected to a serial interface card or some type of I/O card with a serial interface option, whereas the bus mouse is connected to a special card made just for the mouse. This interface was introduced with the IBM-PS/2seriesofcomputers,andwastherefore,calledPS/2.Ithas6pin

andcirculartypein shape.

USBMouse

USB Mouse connects to USB port.

USB stands for Universal Serial Bus, an external bus standard that supports data transfer rates of 12 Mbps. A single USB port can be used to connect up to 127 peripheral devices. USB also supports Plug-and-Play installation and hot plugging.

 

Wirelessmouse

Cordless (Wireless) Mouse isn’t physically connected at all. Instead they rely on infrared or radio waves to communicate with the computer. Cordless mice are more expensive than both serial and bus mice, but they do eliminate the cord, which can sometimes get in the way.

In this type of mouse, everything is similar to the conventional mouse except that no cable is used to connect the mouse to the computer system.

Keyboard:

Keyboard is the most common, familiar and most important input device. It looks likea typewriter. It has got various keys, which are used to give data and commands to the computer. Commonly, we use a standard QWERTY keyboard with letters arranged in the same order as those on a typewriter.

The most important thing to watch out for is the Keyboard connector. If you build an ATX system, you’ll need a keyboard with a PS/2 connector, if you build an AT system, you’ll need one with a DIN connector (Germany’s Deutsche Industries Norm, a committee that set German Standard).

 

PS/2Connector                                              DINConnector

Most new keyboards you come across these days have a nice non-click touch and feel and are as ergonomic as possible, hence eliminating the need for a wrist pad. Click- keyboards are still available though if you prefer to “hear” your own stokes, but it will probably only drive you crazy. The difference between click and non-click keyboards is their design. Click keyboards are mechanical, whereas non-click keyboards use soft rubber membranes to close contact.

A USB keyboard is a Computer keyboard which connects to the central computer system via a Universal Serial Bus port. It uses a separate scancode system to other types of keyboard.

TypesofKeyboard:

Different types of keyboards are used with the IBM PC computers. With each new model of the PC such as PC/PC-XT, PC-AT etc., IBM introduces a new type of keyboard. The recent Enhanced PC-AT keyboard is now being used as industry standard by most of the computer manufacturers.

A typical computer keyboard contains all letters, numbers, symbols of a regular typewriter, plus other keys which may include:

i.      Numberkeys:

These are used for numerical calculation. It contains 0 to 9 and some numerical operators like +, -, *, / etc.

ii.     Functionkeys(F1toF12):

There are used to perform a set of operation (mostly to give the commands to thecomputer) by a single keystroke.

iii.   SpecialKeys

Thespecialkeysareusedforspecifictasks.SomeofthespecialkeysareEnter, Backspace, Del, INS, Shift, ESC, Alt, Ctrl etc.

Enter            :It is one of the most important key on the keyboard. It is used to changethe paragraph and to write the short text. It is also used to enter into the selected computer program by pressing it once.

Backspace:It isusedtodeleteonecharactertotheleftof cursor.

Del               :It is used to delete one character to the right of cursor. It is also used to delete the computer items.

Shift             :It is used to capitalize the letters and write upper printed characters onevery key.

ESC              :It is used to close the dialog boxes and also to terminate the runningprocess.

Alt                :Itisusedto activatethemenubarandtoclosethecurrentwindowwiththe helpofsomeotherkeys.Itisalsousedtodefineshortcutsforthecomputer applications.

Ctrl               :Mainly it is used for shortcut keys to perform specific task inside the computer programs. It is also used to define shortcuts.

WinKey(ÿ):ItisusedtoactivatetheSTARTbutton.

Scanner:

It is an input device that helps to transfer printed text and graphics into the computer. Data read by a scanner iscaptured as a graphic element that can be manipulated by paint or othergraphicsprogram.Somescannersarealsoabletoreadandthenwritetexts,whichwill be much quicker than typing. It is a very easy input method.

To connect a scanner to the computer, you would need an additional card in the motherboard, which usually comes with the scanner. Now days, Scanner comes with USB compatible, so you needn’t insert additional card for Scanner.

Scanners come in the following sizes:

·      Pens(scana line at a time)

·      Hand-held or counter-mounted(scan bar codes or pictures)

·     
Desktop(scan one page at a time)

Desktop(Flat)Scanner

Joystick:

It is a pointing device that is used to move the cursor/pointer on the CRT screen. It is mostly used in computer-based games for selecting menus, options, to play etc.

Therearetwomaintypesofjoysticksavailable:

·        Digital joysticks

·        Analoguejoysticks

Since joysticks are mostly used for game play, it really depends on the type of games that you are interested it. Digital joysticks behave rather like thekeyboard would,in that the movement that is controlled is rather rapid than smooth. You go left, right, up and down bit- by-bit, where every bit of movement is as big (or small) as the other. Analogue joysticks behave rather differentlyin that they are essentially X/Y controllers, where every axis can be controlled variably. This makes analogue joysticks much smoother for games where fine control is important.

DigitalJoystick                                         AnalogJoystick

DigitalCamera:

It is a type of camera that stores photographed images electronically instead of on traditional film. After the image has been captured, it is downloaded by cable to the computer using software supplied with the camera. Once stored in the computer, theimagecanbemanipulatedandprocessedmuchliketheimage from a scanner or related input device.

Webcam:

Web cam is like a video camera on home computers that allow theuser to see people at the same time they communicate on the Internet. Itcan also be used to create a movie and take digital photographs. It is also called PC Cameras. It is specially used in Banks, Departmental Stores, and different organizations for the security control.

Lightpen:

A light pen is also a pointing device like mouse. It can be used to choose a displayed menu option. It is a light sensitive pointing device that can work by pointing on the CRT (Cathode Ray Tube) screen by sensing the position of CRT. It can be used for drawingdirectly on the screen as well as Computer Aided Designing (CAD) purposes.

BarCodeReader(BCR):

A bar code is an identification code given on different products. Lines having different thickness represent the data. The device used to read the barcode, convert the data into electrical signal and send them to computer for processing is called a Bar Code Reader.

OpticalCharacterReader(OCR):

It is a direct entry input device that is used to scan the printed alphanumeric data and transfer the data into the computer. It is generally used in departmental stores for billing.

TrackBall:

A track ball uses a hard sphere to control cursor movement. The ball can be rolled by hand in any direction. The track ball translates the sphere’s direction and speed of rollinginto a digital signal that controls the cursor.

 

TouchScreen:

A touch screen registers input when a finger or other object comes in beams and ultrasonic acoustic waves. Infrared beams zigzag the surface of the screen and when a light beam is broken, that location is recorded. The user can give instructions simply by pressing the graphical box. It is applicable in conducting quizzes, design interior decorations etc.

PointOfSalesTerminal(POS):

Itisaterminalthatconsistsofkeyboard,CRTscreenandinternalprinter.Itisusedfor issuing customer slip in departmental stores. It contains item codes, rate, quantity, total amount etc.

THEPROCESSOR (CPU-CENTRALPROCESSINGUNIT)

CENTRALPROCESSINGUNIT(CPU)

 

The main unit inside the computer is the CPU. This unit is responsible for all events inside the computer. It controls all internal and external devices, performs arithmetic and logicoperations.TheCPU(CentralProcessingUnit)isthedevicethatinterpretsandexecutes instructions.

 

The operations, a microprocessor performs are called the instruction set of this processor. Processors differ from one to another by the instruction set. If the same program can run on two different computer brands they are said to be compatible. Programs written for IBM compatible computers will not run on Apple computers because these two architectures are not compatible.

Mainframes and early minicomputers contained circuit boards full of integrated circuits cards that implemented the central processing unit. Today's single-chip central processing units, called microprocessors, make personal computers and workstations possible. The CPU has the ability to fetch, decode, and execute instructions and transfer information to and fromotherresourcesoverthecomputer'smaindata-transferpath,thebus.Bydefinition,the CPU is the chip that functions as the "brain" of a computer. In some instances, however, the term encompasses both the processor and the computer's memory or, even more broadly, the main computer console (as opposed to peripheral equipment).

All processors use transistors as switches to produce signals, much like a light switch, which digitizes the information and breaks them up into small chunks. If you have one transistor you can perform two signals - on and off. If you have two transistors you can perform four signals - both on, both off, first on, second off, first off, second on. This is interpreted in binary, such as: 00111001 - 0 for off, 1 for on.

TheCPUiscomposedofseveral units...

AsimplifieddiagramoftheCPU

The Control Unit (CU) directs and controls the activities of the internal and external devices. It interprets the instructions obtained into the computer, determines what data are needed, where it is stored, where to store the results of the operation, and sends the control signals to the devices involved in the execution of the instructions.

The Arithmetic and Logic Unit (ALU) is the part where actual computations take place. It consists of circuits, which perform arithmetic operations (e.g. addition, subtraction, multiplication, division) over data received from memory and capable to compare numbers.

OUTPUTDEVICES

OUTPUTDEVICES

 

Output devices are used to get Final Result from the computer. Firstly, Output is displayedonMonitor.ThenwecanprintouttheseoutputsonapaperwiththehelpofPrinter. The purpose of the output devices is to translate data and information from electrical impulses to human-readable format.

The output device, which is necessary for the computer to display messages to the user, is a monitor. If we want to keep the copy of the work on paper, we use printers. Plotters are devices that are more suitable for the large scale outputs like engineering drawings and high quality graphics.

MONITOR

Monitor is the most important peripheral of all the components within a computer system. It is the most important output device. It is also known as Screen or Visual Display Unit (VDU). All information is displayed on the Monitor.The information shown on the monitor is called Soft Copy i.e. temporary. But when it is printed on the paper then it is called Hard Copy.

When we use a computer we needsomedevicetoseetheresultsof the work we are doing. Presently our first choice for this is Monitor.Monitors have now become anintegralpartofmodernday

computers. They are available in many different size and screen resolution. Most monitors in the current market can produce 'watchable' resolutions of at least 800 x 600 pixels. But that was not always the case.

CLASSIFICATIONOFMONITOR

1.        Onthebasisofworkingprinciple

i.      CathodeRayTube(CRT)

ii.     LCD(LiquidCrystalDisplay)

iii.   Gas Plasma

2.       OnthebasisofDisplayAdapterUsed

i.      Monochrome

a.  CompositeMonochrome

b.  VGAMonochrome

c.  Multi-scanningMonochrome

ii.    ColorMonitor

a.  CompositeColour

b.  EGAMonitor(EnhancedRGB)

c.  VGAMonitor

d.  Multi-scanningMonitor

PRINTER

Printer is a hard output device. A printer produces output usually in the form of text, on paper. There are lots of different printers available in the market. The most commonly used types of printers are:

1.    DotMatrix Printers

2.    InkJet Printers

3.    LaserPrinters

·       DotMatrixPrinters:

A type of printer that produces characters and illustrations by striking pins against an ink ribbon to print closely spaced dots in the appropriate shape. Dot-matrix printers are relatively expensive and do not produce high-quality output. However, they can print to multi-page forms (that is, carbon copies), something laser and ink-jet printers cannot do.

It forms characters on a page according to patterns set for each character. It is mostly used in commercial environments for invoice and report printing, where quality and speedare not important. They are cheap to run and to maintain but do not produce high quality output.It gives an output by striking its head onto the paper through ribbon cartridge.

·       InkJetPrinters:

A type of printer that works by spraying ionized ink at a sheet of paper. Magnetized plates in the ink's path direct the ink onto the paper in the desired shapes. Ink-jet printers are capable of producing high quality print approaching that produced by laser printers. A typical ink-jet printer provides a resolution of 300 dots per inch, although some newer models offer higher resolutions.

Normally, InkJet printer holds two cartridges (color and black) produces much better results of black prints. Inkjet printers that only take one cartridge at a time will either not be abletoprintincolor(whentheblack cartridgeisinserted)orhavetoproducethecolorblack by heavily mixing its primary colors cyan, yellow and magenta. This will slow down the printing process and achieve less quality but these types of inkjets are the cheapest. Don'tbe mislead though, as the individual cartridges can be more expensive and they don't last as long, making the printer less economical in the long run. We recommend a printer that takes two cartridges. They're also easier to use and less troublesome.

·       LaserPrinters:

Atypeofprinterthatutilizesalaserbeamtoproduceanimageonadrum.Thelightof the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of thedrum. Finally, the toner is transferred to the paper through a combination of heat and pressure. Thisisalso the way copy machines work.

It uses laser technology to create an image that is transferred to a paper or film. Laser printers are more expensive but are much stronger than inkjets. Lasertoner can be as low in cost as inkjet cartridges. They are faster and give higher quality printing.

Laser Printers are an entirely different breed. They are non-impact printers. Using a combination of light, electricity pressure and head, they have the ability to create very high quality images and text on the printer page.

PLOTTER

A device that draws pictures on paper based on commands from a computer. Plotters differ from printers in that they draw lines using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced series of dots. Multicolor plotters use different-colored pens to draw different colors. In general, plotters are considerably more expensive than printers. They are used in engineering applications where precision is mandatory.

In other words, a plotter is a vector graphics printing device that connects to a computer. Plotters print their output by moving a pen across the surface of a piece of paper. This means that plotters are restricted to line art, rather than raster graphics as with other printers. They can draw complex line art, including text, but do so very slowly because of themechanicalmovementofthepens.(Plotters are incapable of creating a solid regionof color; butcanhatchanareabydrawinganumberof

close, regular lines.) When computer memory was very expensive, and processor power was very slow, this was often the fastest way to produce color high-resolution vector-based artwork, or very large drawings efficiently.

Generally,itisusedinthefieldofEngineeringandMedical, wherelargesizeof outputs is required. Reports generated by Medical equipments, Engineering Maps are produces with the help of Plotters.

MEMORYDEVICES

MEMORYUNITS

 

Computer use memory to hold the programs and data in use by the CPU. Most computers have several type of memory. The main purpose of the memory is to store programs and data so that the CPU may access and process it. It also can store partial solutions during the Computer run.

Mainly, there are two general categories of memory device inside the computer, commonly used today.

1.PRIMARYMEMORY(MAINMEMORY)

 

Though the CPU has calculating capability, it needs some space in which it can actually store the data or to perform calculation. This space in computer is called Primary Memory. Primary Memory is also known as Main Memory. There are two types of Primary Memory:

A.    RAM(RandomAccessMemory/Read-WriteMemory)

Random Access Memory (RAM) is what most of us think of when we hear the word memory associated with computers. It is the running workspace of computer. Initially, every task is stored in RAM, when we save information; they are stored in Secondary Memory (Storage Devices). It is also called Volatile Memory because the information are erased when the power is switched off. 128 MB, 256 MB, 512 MB, 1GB are the sizes of RAM available in market.

RAMisoftenreferredtoasmainmemory orprimary storage. RAMusually occupiesa number of chips connected together. It is used to store programs and data during the execution of program. But when the computer is turned off any information is erased from the RAM. It is electrically dependent.

 

B.    ROM(Read-only-memory)

It is the programming chip, where all of the system information is kept at the time of manufacture. We can see the information of ROM at the time of booting the computer. We can only read the information of ROM; we can’t write/edit ordelete the information available on it. The ROM allows you to read the content of that memory as many times as desired but does not allow modifications. The contents of this memory cannot be edited by the users. ROMs are non-volatile and non-destructive. They are permanent.

When we turn on the computer, the CPU gets its first instructions from the ROM. These instructions are burnt into the chip with the help of special equipment before the chip is installed inside the computer. Users do not have access to the ROM, so they can't change these instructions. It is electrically independent. The data stored in ROM is called Firmware.

2.SECONDARYMEMORY(STORAGEDEVICES)

Secondary Memory i.e. Storage Devices hold files that are not currently being used. Forafiletobeuseditmustfirstbecopiedtomainmemoryfirst.Afteranymodificationsfiles must be saved to secondary storage. It is advisable to save your data files at the regular intervals as you work on them as data can be lost unexpectedly because of various reasons like interruption in power supply, memory management problems, freezing keyboard, etc.

As secondary storage media can be damaged and files on them become corrupted, it is suggested to make back-up copies of valuable files on a regular basis.

Therearemainlythreetypesofmemorydevices:

A.     FlexibleorFloppyDisks(A:orB:)

B.     SolidorHardDisk(C:orD:orE:)

C.     OpticalDisk-CD,DVD(D:orE:orF:-dependsuponthepartitionofharddisk.)

A.    FlexibleorFloppyDisks(A:orB:)

A floppy disk is a small data storage device which is generally used to transfer data from the hard disk. It is also called as Removable Disk. Itis a flexible or portable type. It has 1.44 MB capacity till now. Its drive also lies inside the System Board.

Diskettes, often called floppy disks, are single platter plastic disks in a plastic jacket.The plastic jacket is quite hard on modern 3½"diskettes.

Floppy disks are characterized by several parameters:

A)          On the basis of Size:

i.       3½”Microfloppydisk

ii.      5¼”Mini floppy disk

Size

Sizemeansthediameterofthedisk.BecausefloppydisksweredevelopedintheUSA,

the sizes are still in imperial measurements. The first floppy disks were 8". They are not inuse any more.

The next size was 5¼". These disks are getting out of date and used mainly in oldersystems.

Thestandardsizeoffloppydiskstodayis 3.5".

B)           OnthebasisofDensity:

i.       2DD(DoubleSidedDouble Density)

ii.      2HD(DoubleSidedHighDensity)

Singleordouble-sided

Single-sided disks are not in use any more. Floppy drives have two read/write heads – one for each surface.

Densityisthenumberofbytesthatcanbestoredoneach track.

As diskettes were developed there have been changes in the density. Originally onDOS computers the density was 1.25 kilobytes per inch of track. As disk drive and disk technologies were improved disks that could hold 2.5 kilobytes per inch were released and called (logically) double density disks. Later again further improvements permitted quad density, now commonly called high-density disks and drives. The original low-density disks have now disappeared, leaving only double and high-density disks. This results in some confusion for new users, as the name double density seems to imply it holds more than the other current type - high density.

Double density diskettes are no longer common. They are generally labeled DD or 2D. In addition, on 5¼" disks they have a ring around the hub and on 3½" disks the hole near the bottom right corner is filled in.

High-densitydisksareusuallylabeledHD.3.5"high-densitydiskscanholdupto

1.44Mof data.

In the past couple of years the density was increased and disks that can hold 2.88M appeared on the market but they are not widely used.

C)           OnthebasisofCapacity:

i.       360KB(5¼”–2DD)

ii.      1.2MB(5¼”– 2HD)

iii.     720KB(3½”–2DD)

iv.     1.44MB(3 ½”–2HD)

The details about the various types of floppy disks used on DOS/Windows computers are summarized in the table below:

 

Size	Density	TracksperSide	Sectors	Total KB
5¼"	Double	40	9	360
5¼"	High	80	15	1,200
3½"	Double	80	9	720
3½"	High	80	18	1,440

The total capacity of a disk is a multiplication of surfaces by tracks by sectors. So, a 3½" high-density disk can hold 2 x 80 x 18 x 512 = 1,474,560 bytes (1,024 = 1,440K).

All disk drives have indicator lights that show when the disk is actually being used. A disketteshouldneverberemovedwhilethislightison.Youshouldalwaysglanceatthislight before removing a diskette.

Floppy disks, like audio and video cassett es, can be delete-protected. On diskettes it is called write protection. It protects data from deletion and alteration. If the diskette is never to be altered or contains important data this is a useful facility. If you are attempting to save onto a diskette and DOS responds with the message Write Protect Error, this indicates the diskette has been write-protected. To write protect a 3½" disk, the notch on the bottom left corner should be opened. To remove write protection you reverse these actions.

Advantages of usingfloppy disks:

·      Theyallow tocopy filesfrom onecomputer to another;

·      Theyarequite cheap.

Disadvantages of using floppy disks:

·      Theyhavealimitedcapacity(graphicsfilesoftendon’tfitonadisk);

·      Theyarerelativelyslow;

·      They are less reliable than hard disks so proper care should be taken to prevent loss of data.

Itisimportanttotakepropercareofyourdiskstominimizethedangeroflosingdata.

Taking Care of Floppy Disks:

Assoonasyouplaceafileonadisk,itsvalueincreases,atleastforyou.Soitis important to take some precautions in order not to lose your valuable files.

·        Keepbackupcopiesofallvaluablefiles

·        Write-protectthefloppydisksintendedforread-onlyuse

·        Keepdisksawayfromthesunandheat(theyaremadeofplasticandplasticmelts)

·        Keepthemawayfrommagnetism(thiswillinterferewiththe data).

·        Cleanfloppydrivesperiodicallywithacleaningkit(butdon'twashorcleanthediskswith a cloth)

·        Keepthemawayfromsmoke(dangerofsurfacecontamination)

·        Don'ttouchthedisksurfacethroughtheaccessslots(dangeroffingerprints)

·        Don'tforceadiskintoadiskdrive.Itshouldslideinwithlittleornoresistance.

·        Don'tinsertorremoveafloppydiskfromthedriveifthelightindicatingthatthedisk drive is active is on.

·        Don'tbendorsquash5¼"disks,asthiswillpreventspinningofdiskinsidethejackets.If a disk is bending or squashed, don't iron it.

·        Evenlabelingdiskettesmaycauseproblemsifyoupresshardwhenwritingonthe label.

B.       HardDiskorFixedDiskorSolidDisk(C:orD:or E:)

It is the main storage device. It consists of all of the Computer’s item as well as documents created by using all software. It lies inside the System Board (CPU Box).Technically microcomputer hard disks are called or fixed disks, as they are a pack of disks permanently sealed inside a disk drive.

The sealed case contains platters fixed in place, read/write heads and other part of mechanisms. It overcomesmuchofthedangerofdust,magnetismand

fingerprints interfering with the data. The read/write heads do not actually touch the surface of the disk (as in floppy disk drives) but fly over it on a cushion of air.

Fixed disks have much greater capacity than floppy disks and can access data faster than any other storage devices. Today’s hard disks capacities are measured in gigabytes.The increased capacity is in part because of the metal surface, in part because they are sealed inside a case and in part because the disks are multi-layered.

To connect a hard disk to a microcomputer, a hard disk controller card must be installedonthemotherboard.Thiscardincludescircuitrythatservesasaninterfacebetween the motherboard and the hard disk. The circuitry must conform to standards. Two most common standards today are Small Computer System Interface (SCSI) and Integrated Drive Electronics (IDE). The IDE standard has a size limit of 528M, which is too small for modern PCs. EIDE superceded IDE and has increased the maximum size allowing up to 4 hard drives to be connected at once.

It is possible to have more than one hard disk inside your computer. In this case the main disk is called master, and the second is called slave.

Invention of hard disks certainly eliminated the difficulties faced by microcomputer users of a few years ago of having to locate and insert a number of different floppy disks whenever they wished to use their computer.

The disadvantage of storing everything on a hard disk is that data, if not programs, is often required to be transferable between computers. In consequence, floppy disks retain valueasameansofmovingdata.Butontheotherhandmodern filesareoftenbiggerthana floppy disk can hold. So new technologies like zip drive and jaz drive appeared on themarket.

C.    OpticalDisks(D:orE:or F:)

Optical disks are produced using laser technology, and as a result offer much higher density and reliability than magnetic disks. Disks are made of plastic or metal with highly reflective coating, usually aluminum. Like magnetic disks, they allow direct access to data.

Therearemainlythreetypesofopticaldisksavailableinthemarket.

·        CD-ROM(CompactDisk-ReadOnly Memory)

·        CD-RW(Re-writeablememory)

·        DVD(DigitalVideo/VersatileDisk)

CD-ROM (Compact Disk Read-Only Memory) is the most popular and the least expensive type of optical disks. As the name indicates they come prerecorded with data, which cannot be altered. It is an offshoot of the CD audio disk. The advantage of CD-ROM over other optical disks is that the introduced standard ensures that any CD-ROM drive will read any CD-ROM disk.

  

They can store up to 750M and are used for distribution of massive quantities of data (e.g., encyclopedias, document archiving, manuals, statistics, and software packages) at relatively low cost. Today when you buy a software package, you have a choice between one CD-ROM and a bundle of floppy disks.

A CD-ROM has one track that spirals from the center to the outside edge. The track is divided into sectors of equal length and density. Files are stored on contiguous sectors. Fragmentation of files cannot happen because data can be written only once.

A CD-ROM drive reads disks differently from a music disk, in that it spins at a constant linear velocity (CLV), instead of a constant angular velocity (CAV). This means that there is not a constant data transfer rate across the CD (more data per rotation can be stored in the outer regions). By utilizing CAV techniques, the data transfer rate can be significantly increased for the majority of your data. Another way of doing that is by increasing the rotation speed of the drive itself. Eachmultiplier ofthe standard 150 KB/sec. makes the data transfer rate faster, so a 2X drive reads 300 KB/sec., a 4x 600 KB/sec and so forth.However, top reading speed can only be achieved at the outer regions of the CD. Therefore the transfer rate may start at 3600 KB/sec (24X) at the inner regions and increase to 7200 KB/sec (48X) at the end of the disc, giving an overall performance of about 36X.

Re-writable optical disks (CD RW) typically are used for data backup and archiving very big amounts of data, such as image databases.

Digital Versatile Disks (DVD): Like CD ROM drives, DVD drives are optical storage devices that use lasers to write to and read from their media, and essentially DVDs use the same principles as CDs. When writing to a DVD, a laser creates pits on its surface to represent data. Areas not burned into pits by the laser are called lands. The laser reads back the data on the optical disk by scanning for pits and lands. There are, however a number of differences that make the DVD superior to the CD.

CaringforCDs:

AlthoughCDsaresturdy,theycanbecomescratchedandunreadable.Ascratchonthe label side on the disk can be more damaging than on the data side because the protective coating on the label side is thinner than that on the data side. A scratch on a data side can oftenbecompensatedby anerrorcorrectionwhereasascratch onthelabel sidecandamage pits and lands into unrecoverable errors.

So protect your disks from scratches, strong sunlight, heat, humidity, and extreme cold. Store your disks in the cases in which you purchase them.

Toavoidfingerprints,alwayshandleyourdisksbytheoutsideedges.

Othersecondarystoragedevices:

ZIP Drive:

A small portable disk drive supplied by Iomega Corporation. Disks come in two sizes, 100 Mb and 250 Mb. A Zip drive is needed to read and write 3.5 inch Zip disks; t is available in either a parallel or SCSI version. When using a parallel Zip drive a printer can be chained off the drive so bothcanusethesameparallelport.Adiskdrivefrom IomegaCorporationwhichtakesremovable100megabyte

hard disks. Both internal and external drives are manufactured, making the drive suitablefor backup, mass storage or for moving files between computers. Software is included to help with file organization. The internal SCSI model offers up to 60 MB / minute transfer rate.

The Zip drive was awarded Byte's Readers' Hardware Choice Award 1996. The companyhasstartedtomanufacturealargerJazdrive,which

takesonegigbytedisks.

Jaz Drive:

A high-capacity removable hard disk system from Iomega. The Jaz has been very popular. In 1997, 2 GB drives were introduced, which support 1 GB and 2 GB disks.

 

PenDrives(MemoryStick/Flash Drive):

When using PC's and very often while building or upgrading PC's, you'll need totransfer some data between machines. No problem, just throw in a floppy disk, copy all your data onto it and copy it off again at the other PC. Easy.

But is it ever that simple? With the increasing complexity and size of today's applications and file sizes, our old friend the floppy disk just doesn't seem to have the capacity to keep up. At 1.44MB, you're usually going to need to compress your files, and even then you'll need to make sure that the compressed file is less than 1.44MB so it will actually fit.

"No problem!" you say, "I'll get myself a Zip Drive." Fine. With up to 250MB capacity you can store everythingyou want and more on it. But already those nasty problems have started to creep in. The most significant of those being "Does the other PC have a Zip drive?"

To solve these problems, Pen Drive is in your hand. Usingthisdeviceyoucaneasily transferthefilesmorethan1 GB easily.

Pen Drive is a small keyring-sized device that can be used to easily transfer files between USB-compatible systems. Available in a range of capacities (and in some cases, with an MP3 player built-in) this handy little gizmo can save all those data-transfer hassles.

It looks like a pen and contains memory more than 100 Mega Bytes. 32MB, 64MB, 256MB, 512MB, 1GB, 2GB, 4GB are the available Pen Drive Size in the Market.

PERIPHERALDEVICES

PERIPHERALDEVICES

 

Peripheral devices are devices connected to the computer but external in relation tothe processing unit. If a peripheral device is disconnected, the computer will still be able to work;onlyfunctionsperformedbythisperipheraldevicewillnotbeavailable.Forexample,if you disconnect a keyboard, you would not be able to type in information but you will be able work with the graphical user interface by clicking the mouse. If you remove the hard disk, youwillhavetostartupyourcomputerusingfloppydiskandyouwillhavetosaveyourdata on floppy disks only but the computer will still be working.

Peripheral devices can reside inside the computer case or outside. For example, a mouse, a keyboard, a monitor are always outside the case and they are connected to the computer via ports which are situated on the back of the case. Disk drives are positioned inside the case and they are connected to the motherboard via disk controller cards whichare inserted in the expansion slots on the motherboard.

ExceptInput/Outputdevices,therearesomeotherimportantperipheraldeviceslike:

TheModem/InternetAdapter

A device that converts the digital signals produced by terminals and computers into the analog signals that telephone circuits are designed to carry. Despite the availability of several all-digital transmission networks, the analog telephone network remains the most readily available facility for voice and data transmission. Since terminals and computers transmitdatausingdigitalsignaling,whereas

telephone circuits are designed to transmit analog signals used to convey human speech, a device is required to convert from one to the other in order to transmit data over telephone circuits. The term modem is a contraction of the two main functions of such a unit, modulation and demodulation. The device is also called a data set.

In its most basic form a modem consists of a power supply, transmitter, and receiver. The power supply provides the voltage necessary to operate the modem's circuitry. The transmitter section contains a modulator as well as filtering, wave-shaping, and signalcontrol circuitry that converts digital pulses (often input as a direct-current signal with one level representing a digital one and another level a digital zero) into analog, wave-shaped signals that can be transmitted over a telephone circuit. The receiver section contains a demodulator and associated circuitry that is used to reverse the modulation process by converting the received analog signals back into a series of digital pulses.

In order to connect to the Internet you need some form of Modem or Adapter. Computers are digital machines in that the information is represented by codes of small currents. Standard telephone lines however, are analogue devices in that the information is directly represented by analogue waves. That's why we need Modems to convert (modulate) the digital code into analogue waves and convert them back into digital (demodulate) at the other end. Modem provides you with 56k (56 thousand bytes) per second download speed and 34k upload speed.

Modemsare available as internal and as external devices. External modems areslightly more expensive (because of the housing, the cable, the power supply, etc.) but are generally more reliable and less troublesome. There are still internal modems around that cause conflicts. Remember that a modem is a serial device. If you connect your external modem to one of your COMs ports, you use a port that's already present.

Speakers

Computerspeakersdifferfromconventionalspeakersonlyintwoways,theyare:

·        Selfamplified(mostly)

·        Magneticallyshielded

Depending on the power of your sound card it might be possible for you to get some half decent sound out of non-amplified speakers, but the "On" switch really makes all the difference. Most speakers can take standard AC power supplies and have separate volume and tone controls. Others come with a power connector that plugs into your PSU.

Microphones

There is not that much to say about PC microphones. They are essentially exactly the same kind of microphones than any other microphone you can buy. The recording quality depends more on the quality of your sound card than on the microphone itself. Depending whether you have a stronger or a weaker soundcard, you might need a microphone with higher impedance. There are some microphones available that feature their own little amplifier, which is powered by a lithium battery.Whenmakinganykindofrecording,makesurethatthe

background noiseofyourenvironment(i.e.yourlivingroom)isaslowaspossible.Especially if you are making telephone calls over the Internet or are in a video/audio conference. Audio signals transmitted over the Internet are not as good by far than what you are used to from your telephone.

SoundCards

The sound card is a hardware device that allows you to hear audio from files, movies, games, even CD's, through your computer.

Information   is    passed   through   the   CPU   to                               the processingchiponthesoundcard.As withthevideocard, the work of processing this data into something you can hear (an analog signal) is done in the RAM. After the digital sound data isconverted,itissenttotheoutputconnectionswherethe speakers,headphones,orotheroutputdevicesarepluggedin.

This process is reversed if you plug a microphone into the sound card. The sound of your voice is converted into digital data by the sound card and can be stored on your computer.

One may ask though, how does CD sound get through mysoundcardandoutthespeakers.WhenaCD-ROMdriveis

installed,oneofitsoutputsisconnectedthroughacabletothesound card.

The sound card is located at #8 (See Picture). The small, round connectors are for the speakers, microphone, and a line in/out to an external device. Most sound cards also have a connector for a joystick, game pad, etc (the large, pin-type connector at the left side of the card).

TVTunercard

ATVtunercardisacomputercomponentthatallowstelevisionsignalstobereceived by a computer. Most TV tuners also function as video capture cards, allowing them to record television programs onto a hard disk.

InternalTVTuner Card                                                 ExternalTVCard

TVtunersareavailableasPCI-busexpansioncardorUSBdevices.Thetrendis

towardsUSB devices.Inaddition,somevideocards doubleasTVtuners,notablytheATI All- In-Wonder series. The card contains a receiver, tuner, demodulator, and an analog-to-digital converter for analog TV. Many cards are limited to the radio frequencies and video formats used in the country of sale. However, many TV tuners used in computers use DSP, so a firmware upgrade is often all that's necessary to change the supported video format. Many newer TV tuners have flash memory big enough to hold the firmwares for decoding several different video formats, making it possible to use the tuner in many countries without having to flash the firmware. In addition to the frequency tuner, many include a composite video input. Many TV tuners can function as FM radios: this is because the FM radio spectrum lies between television channels 6 and 7, and the DSP can be easily programmed to decode FM.

Therearecurrentlythreekindsoftunercardonthe market:

·         Cards for analog TV. Cheaper models output raw tuner data, which requires CPU- intensive encoding by another device, normally the system CPU. More expensive models encode the signal to MPEG, relieving the main CPU of this load. Many cards also have analog input (composite video or S-Video). and many also provide FM radio reception.

·         Cardsfordigital TV,includingsatelliteTV. Digital TVisbroadcast asanMPEGstream, so no encoder is necessary; instead, the digital cards must extract the correct PIDs from the transport stream, which requires much less processing power.

·         Hybridtunersthathandlebothanaloganddigitalinputs.

A related device is a digital television adapter, a device that receives DVB transmissions and converts them to analog for use on analog TVs.

STARTINGSYSTEMOFCOMPUTER

We know that a computer is simply a machine which works under the control of a setof instructions called program. For a computer to be ready to work, all its peripherals should be checked and activated, and the relationship between hardware and software needs to be established. For this purpose, a special type of software is used, which is called as an Operating System.

Starting process of Computer varies from one operating system to another. There are different processes to enter into the programs. It depends upon the operating system installed into the computer. So, you have to know about operating system of computerbefore running the programs.

Therearemainlytwotypesofoperatingsystemusedinthe computer:

1.   Ms.DOS(MicrosoftDiskOperatingSystem)

2.   Ms.Windows(MicrosoftWindows3.11,’95,’98,’Me,’00, ’XP..)

However,theinnerprocessofstartingyourComputerissame,whichiscalledBooting.

Booting:

The process of loading the system files of the operating system from the disk into the computer memory to complete the circuitry requirement of the computer system is called booting. The system files of MS. DOS are:

·      IO.SYS:It checks all the input and output devices and their activities and make them ready.

·      MS.DOS.SYS:      Itbuildstherelationbetweenthehardwareandtheapplication software-acting as interface.

·      COMMAND.COM:It helps to make the instructions given to the computer using thedifferent programs executable.

IO.SYSANDMSDOS.SYSarehiddenfilesbutCOMMAND.COMisvisible.

 

TypesofBooting:

Therearetwotypesof booting:

·        Cold Booting:If the computer is in off state and we boot the computer by pressing the power switch ‘ON’ from the CPU box then it is called as cold booting.

·        Warm Booting: If the computer is already ‘ON’ and we restart it by pressing the ‘RESET’ button from the CPU box or CTRL, ALT and DEL key simultaneously from the keyboard then it is called warm booting.

HowtostarttheComputerinMs.Windowsmode?

Thereisnothingspecialyouneedtostartthissystem.Just,

1.   SwitchONthePower Supply.

2.   SwitchONtheCPU and,

3.   SwitchONtheScreen (Monitor).

Then, wait for sometime, you will directly enter into the Windows Environment (i.e. Desktop) and see the following window. With the help of this Environment, you can perform any types of work related to the computer.

 

HowtoShutdown(TurnOff)theComputer?

BeforeshuttingdowntheComputer,closeallopenedwindowsatfirst. Then,

1.    Click onStartbutton.

2.    ClickonShutdown(TurnOffComputer). Then, Computer asks you:

Whatdo you want the Computer to do?

·      Standby

·      Shutdown (Turn Off)

·      Restart

·      RestartinMS-DOS mode.

Note: The options willbedifferentfromone OS toanother.

3.    Choose2ndoption(i.e.Shutdown/TurnOff).

4.    Click onOK.

Then,wait until the message “It’s nowsafe to turnoff yourComputer”.

5.    Then,SwitchOffthe screen.

6.    SwitchOffthe CPU.

7.    Atlast,SwitchOffthepower supply.

Note:ShutdowningsystemofWindowsvariesfromoneOperatingSystemto another.

APPLICATIONFILENAMESOFSOMEPROGRAMS

1.      typshala.exe                   :Typeshalatypingprogram

2.      tt?.exe/tt.exe                 :Typing Tutors

3.      wordpad.exe                  :Simplewordprocessingprogram(WordPad)

4.      notepad.exe                   :Simplewordprocessingprogram(Notepad)

5.      calc.exe                           : Calculator

6.      mspaint.exe                    :MicrosoftPaint(PaintBrush)

7.      command.com                :DOSPrompt

8.      winword.exe                   :MicrosoftWord

9.      excel.exe                         :MicrosoftExcel

10.      powerpnt.exe                 :MicrosoftPowerPoint

11.      msaccess.exe                 :MicrosoftAccess

12.      pm65.exe/pm70.exe     :AdobePageMaker6.5/7.0

13.      coreldrw.exe                   :CorelDraw

14.      photoshp.exe/

photoshop.exe               :AdobePhotoshop6.0/7.0

15.      msoffice.exe                   : Shortcut Bar

16.      frontpg.exe                     :Microsoft Front Page.

17.      charmap.exe                   :Character Map

18.      mplayer.exe;

wmplayer.exe;

wmplayer2.exe              :Media Players

19.      cdplayer.exe                   : CD Player

20.      explorer.exe                   :Windows Explorer

21.      flash.exe                         :Free hand Flash

22.      Iexplore.exe                   :Internet Explorer

23.      msimn.exe                      :Outlook Express

Most Reliable method to search application programs:

1.    Click on Start button.

2.    Choose Search.

3.    ChooseForFilesorFoldersandclickonit;againclickonAllFilesorFoldersoptionin case of Windows’ XP.

Then the following dialog box will appear.

Windows’00                                                         Windows’XP

4.    Type any above required application file name at the Search for Files or Folders (All or part of the file name) box.

5.    Select My Computer or Local Hard Drives from the Look in dropdown menu.

6.    Click on Search now(Search) button.

Then, the icon of the selected program will display.

7.    Give double  click unit.

Then, you will directly enterinto the program.

Note: You can also run the applications by using its application file name. Start - Run - type application file name and click on OK.

Wild Card:

Youcanusethefollowingcharacteratthetimeofsearchinganytypesofunknown item inside the Computer.

1.    Question mark(?)–It representssing leun known character.

2.    Asteriskor Star mark(*)–It represents group of unknown characters.

NAMESOFKEYBOARDKEYS

 

~ ! @	= = =	Tiled key Exclamation Atthe rate
#	=	Hash
$	=	Dollar

 

%	=	Percentage
^	=	Carat
&	=	And
*	=	Asteriskor Starmark
( )	=	Parentheses
-	=	Dash
_	=	Underscore
|	=	Vertical mark orpipeline
;	=	Semicolon
:	=	Colon
‘…’	=	Single quote mark (smart)
“…”	=	Double quote mark (smart)
'	=	Single quote mark(straight)
"	=	Double quote mark(straight)
/	=	Slash
\	=	Backslash
<	=	Less than
>	=	Greater than

|(blinking)=Cursoror Insertion Pointeror blinking verticalline

¯®­¬         =     Arrow keys

¿                  =     Enter key

FULLFORMSOFSOMEBASICCOMPUTERTERMS

AC                        :            Alternating Current

ALU                      :            Arithmetic And Logical Unit

ARPANET              :            Advanced Research Project Agency Network

ASCII                    :                            American Standard Code For Information Interchange AT                            :            Advanced Technology

ATX                      :            Advanced Technology Extended

BIOS                     :            BasicInputOutputSystem

BIT                       :            Binary digit

CAD                      :            Computer Aided Design

CD                        :            Compact Disk

CD-ROM               :                            Compact Disk Read Only Memory CD-RW                       :            Compact Disk Re-writable

CMOS                   :                            Complementary Metal oxide Semiconductor COM                            :            Communication

CPU                      :            Central Processing Unit

CRT                      :            Cathode Ray Tube

CU                        :            Control Unit

DBMS                   :            Database Management System

DC                        :            Direct Current

DNA                      :            Digital Network Architecture

DNS                      :            Domain Name System

DOS                     :            Disk Operating System

DVD                     :            Digital Versatile/Video Disk

E-commerce         :                            Electronic Commerce/Business EGA                            :            Enhanced Graphics Adaptor

E-mail                   :            Electronic Mail

FAT                       :            File Allocation Table

FDD                      :            Floppy Disk Drive

FTP                       :            File Transfer Protocol

GB                        :            Giga Byte

GHz                      :            Giga Hertz

GUI                      :            Graphical User Interface

HDD                     :            Hard Disk Drive

I/O                       :            Input/Output

IBM                      :            International Business Machine

IC                         :            Integrated Circuit

IDE                       :            Integrated Device Electronic

IP                         :            Internet Protocol

ISA                       :            Industry Standard Architecture

ISDN                    :            Integrated Services Digital Network

KB                        :            Kilo Byte

LAN                      :            Local Area Network

LCD                      :            Liquid Crystal Display

LED                      :            Light Emitting Diode

LU                        :            Logical Unit

MAN                     :            Metro Area Network

Mb                        :            Mega Bits

MB                        :            Mega Bytes

MHz                      :            Mega Hertz

Ms.                       :            Microsoft

MS-DOS               :            Microsoft Disk Operating System NETBIOS  :                            NETwork Basic Input Output System Net BUI                  :            NetBIOS Extended User Interface NFS       :            Network File System

NIC                       :            Network Interface Card

NOS                      :            Network Operating System

NTFS                    :                            New/Networking Technology File System OS                            :            Operating System

PC                        :            Personal Computer

PING                     :            Packet Inter Net Gopher

PSDN                    :            Packet Switching Data Networking

RAM                      :            Random Access Memory

RAS                      :            Remote Access Server

ROM                     :            Read Only Memory

SCSI                     :            Small Computer System Interface

SMPS                    :            Switch Mode Power Supply

TB                        :            Tera Byte

TCP                      :            Transmission Control Protocol

TCP/IP                  :                            Transmission Control Protocol/Internet Protocol TT                            :            Typing Tutor

UPS                      :            Uninterruptible Power Supply

VDU                      :            Visual Display Unit

VGA                      :            Video Graphic Array

VLSI                     :            Very LargeScale Integration

VPN                      :            Virtual Private Network

WAN                     :            Wide Area Network

XT                        :            Extended Technology