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COMPUTERS AND BASIC CONCEPTSINTRODUCTION

The word ‘compute’ means ‘to calculate’. We all are familiar with calculations in our lifeand do mathematical operations like addition, subtraction, multiplication, etc. Simplercalculations take less time. But complex calculations take much longer time. Another factor isaccuracy in calculations. So man explored with the idea to develop a machine which canperform this type of arithmetic calculation faster and with full accuracy. This gave birth toa device or machine called ‘computer’.

WHAT IS A COMPUTER?Computer is an electronic device, which can do arithmetic calculations faster. How ever

modern computer it does much more than that. It is a machine capable of solving problemsand manipulating data. It accepts data, processes the data by doing some mathematicaland logical operations and gives us the desired output as information.Computer can be defined in terms of its functions. It there forei) Accepts dataii) Stores data,iii) Process data as desired,iv) Retrieve the stored data as and when requiredv) Prints the result in desired format.

CHARACTERISTICS OF COMPUTERSpeed

It takes few minutes for the computer to process huge amount of data and give the result. Atypical computer can perform millions (1,000,000) of instructions and even more per second.Therefore, we determine the speed of computer in terms of microsecond (10-6 part of a second)or nano second (10-9 part of a second).Accuracy

The degree of accuracy of computer is very high and every calculation is performed withthe same accuracy. The accuracy level is determined on the basis of design of computer.Whatever the errors that are committed by a computer are due to human and inaccurate datafeed. If given right data, it always give the right result with accuracy.Diligence

A computer is free from tiredness, lack of concentration, fatigue, etc. It can work for hourswithout creating any error. If millions of calculations are to be performed, a computer willperform every calculation with the same accuracy. Due to this capability computer has diligencethan humans.Versatility.

It means the capacity to perform completely any or different type of work. Computer hasthe power of storing any amount of information or data at any length of time. Any informationcan be stored and recalled as long as we require it, for any numbers of years.

No IQ-Computer is a dumb machine and it cannot do any work without instruction from theuser. It performs the instructions at tremendous speed and with accuracy as long as it is given

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right instructions in right sequence.4 Storage-The Computer has an in-built memory where it can store a large amount of data.We can also store data in secondary storage devices such as floppies, which can be kept outsidecomputer and can be carried to other computers (called Portability).

HISTORY OF COMPUTERSFollowing were some of the path-breaking inventions in the field of computing devices.

Calculating Machines-The first calculating device called ABACUS was developed by theEgyptian and Chinese people. The word ABACUS means calculating board. It consisted ofsticks in horizontal positions on which were inserted sets of pebbles. A modern form of ABACUSwhich is used to teach children simple calculations has a number of horizontal bars each havingten beads. Horizontal bars represent units, tens, hundreds, etc.

Napier’s bones-English mathematician John Napier built a mechanical device for the purposeof multiplication in 1617 A D. The device was known as Napier’s bones.

Slide Rule-English mathematician Edmund Gunter developed the slide rule. This machinecould perform operations like addition, subtraction, multiplication, and division. It was widelyused in Europe in 16th century.

Pascal’s Adding and Subtraction Machine-Blaise Pascal had developed a machine at theage of 19 that could add and subtract. The machine consisted of wheels, gears and cylinders.

Leibniz’s Multiplication and Dividing Machine-The German philosopher and mathematician Gottfried Leibniz built around 1673 a mechanical device that could both multiply and divide.

Babbage’s Analytical Engine-It was in the year 1823 that a famous English man CharlesBabbage built a mechanical machine to do complex mathematical calculations. It was calleddifference engine. Later he developed a general-purpose calculating machine called analyticalengine. For this invention he was later came to be known as the father of computer.

Mechanical and Electrical Calculator-In the beginning of 19th century the mechanicalcalculator was developed to perform all sorts of mathematical calculations. Up to the 1960s itwas widely used. Later the rotating part of mechanical calculator was replaced by electricmotor. So it was called the electrical calculator.

Modern Electronic Calculator-The electronic calculator used in 1960 s was run with electrontubes, which was quite bulky. Later it was replaced with transistors and as a result the size ofcalculators became small. After the advent of Computers not only it can compute all kinds ofmathematical computations and mathematical functions but also have become capable of storingsome data permanently.

GENERATIONS OF COMPUTERSThe period, during which the evolution of computer took place, can be divided into five distinct phases known as Generations of Computers. Each phase is distinguished from others on thebasis of the type of switching circuits used.First Generation Computers (1940-1956)First generation computers used Thermion valves. These computers were large in size andwriting programs on them was difficult. Some of the computers of this generation were:

ENIAC: It was the first electronic computer built in 1946 at University of Pennsylvania, USAby John Eckert and John Mauchy. It was named Electronic Numerical Integrator andCalculator (ENIAC).

EDVAC: It stands for Electronic Discrete Variable Automatic Computer and was developedin 1950. The concept of storing data and instructions inside the computer was introducedhere. This allowed much faster operation since the computer had rapid access to both dataand instructions. The other advantage of storing instruction was that computer could dological decision internally.


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OTHER IMPORTANT COMPUTERS OF FIRST GENERATIONEDSAC: It stands for Electronic Delay Storage Automatic Computer and was developed

by M.V. Wilkes at Cambridge University in 1949.UNIVAC-1: Ecker and Mauchly produced it in 1951 by Universal Accounting Computer

setup.CHARACTERISTICS OF 1 ST GENERATION COMPUTERS

These computers uses vacuum tube for data processing and storageThey had a memory size of 20bytes speed of 5mbpsThey produced a lot of heatIt required large space for installation.The programming capability was quite low.These computers were unreliable slow and could not work fast with a lot of dataThey uses punch card for data storageThe programmes were machine dependentFirst generation computers used to consume a lot of power

Second Generation Computers (1956-1963)Around 1955 a device called Transistor replaced the bulky electric tubes in the firstgeneration computer. It is in the second generation that the concept of Central ProcessingUnit (CPU), memory, programming language and input and output units were developed.The programming languages such as COBOL, FORTRAN were developed during this period.Some of the computers of the Second Generation were

IBM 1620: Its size was smaller as compared to First Generation computers and mostly usedfor scientific purpose.

IBM 1401: Its size was small to medium and used for business applications.CDC 3600: Its size was large and is used for scientific purposes.

Characteristics of 2nd generation computersWere capable of translating, process and store dataHad got memory size of 32bytes speed of 10mbpsWere reliable compared to first generation computersProduced less heat compared to first generation computersThey uses punch card for data storageConsumed less energy compared to first generation computers

Third Generation Computers (1964-1971)The third generation computers were introduced in 1964. They used Integrated Circuits (ICs).These ICs are popularly known as Chips. A single IC has many transistors, registers andcapacitors built on a single thin chip of silicon called ‘semi conductor’. So the size of thecomputer got further reduced. Some of the computers developed during this period were IBM-360, ICL-1900, IBM-370, and VAX-750. Higher level language such as BASIC (Beginners Allpurpose Symbolic Instruction Code) was developed during this period. Computers of thisgeneration were small in size, low cost, large memory and processing speed is very high.

They used integrated circuit(ICs.) to store dataThe integrated circuit consisted of many transistorsUsed storage disk for data storage e.g. magnetic disks, tapesThird generation computers were more reliable compared to other previous generationsFor the first time, instead of punched cards and printouts, users interacted with third

generation computers through keyboards and monitors and interfaced with an operatingsystem


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Fourth Generation Computers (1971-Present)The present day computers that we see today are the fourth generation computers that startedaround 1975. It uses large scale Integrated Circuits (LSIC) built on a single silicon chip calledmicroprocessors. The microprocessor brought the fourth generation of computers, as thousandsof integrated circuits were built onto a single silicon chip. What in the first generation filled anentire room could now fit in the palm of the hand. Due to the development of microprocessor itis possible to place computer’s central processing unit (CPU) on single chip. These computersare called microcomputers. Fourth generation computers also saw the development of GraphicalUser Interface (GUI), the mouse and other handheld devices.

Fifth Generation Computer (Present and beyond)The computers of the years beyond 1990s and presently being developed systems are said to

be Fifth Generation computers. Very large scale Integrated Circuits (VLSIC) replaced LSICs.The speed is extremely high in fifth generation computer. Apart from this it can perform parallelprocessing. The concept of Artificial intelligence has been introduced to allow the computerto take its own decision. Quantum computation and molecular and nanotechnology willradically change the face of computers in years to come. The goal of fifth-generation computingis to develop devices that respond to natural language input and are capable of learning andself-organization.

Classification of ComputersClassification of the computers may be based on either their principles of operation ortheir configuration.Classification based on Principles of OperationBased on the principles of operation, computers are classified into three types, analogcomputers, digital computers and hybrid computers.

1) ANALOG COMPUTERAn analog computer, processes or Measures physical quantities that vary continuously, suchas variations in temperature, speed, pressure, or the amount of current flowing through onelectrical conductor etc. Analogue computer does not compute directly with numbers; ratherit measures, continuous physical magnitudes (e.g., pressure, temperature, voltage, speed,etc.) Analog computers are used for a wide variety of industrial and scientific applications thatrequire the quantifying continuously varying data. Slide rule, thermometers pressure gauge,speedometer etc are often cited as examples of analogue computers.

2) DIGITAL COMPUTERDigital computer, On the other hand operates on digital data such as numbers. They representdata in discrete form. They convert all inputs into numbers before processing them. It usesbinary number system in which there are only two digits 0 and 1. These types of computersare more accurate than the analogue computers since there is no analogous representation. Allmodern electronic computers are examples of digital computers.

3) HYBRID COMPUTERA hybrid computing system is a combination of desirable features of analog and digitalcomputers. It is mostly used for automatic operations of complicated physical processes andmachines. Now-a-days analog-to-digital and digital-to-analog converters are used for transformingthe data into suitable form for either type of computation. For example, in hospital’s automatedintensive care unit, analog devices might measure the patient’s temperature, blood pressure(Which are physical quantities). These measurements which are in analog then will be convertedinto numbers and supplied in digital format or shown as a result in a computer.

CLASSIFICATION OF COMPUTERS BASED ON CONFIGURATIONBy configuration, we mean the size, speed of doing computation and storage capacity of a


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computer. There are various types of computers depending upon the size, efficiency, memoryand number of users. Broadly they can be divided it to the following categories.

1) MicrocomputerMicrocomputer is at the lowest end of the computer range in terms of speed and storage

capacity. Its CPU is a microprocessor. So a microcomputer is a computer with amicroprocessor as its central processing unit.

The first microcomputers were built of 8-bit microprocessor chips, though currently32-bitchips are available. .

Personal computers (PCs) come in this category. They are often called personal computersbecause they are designed to be used by one person at a time. Personal computers are typicallyused at home, at school, or at a business. Examples of microcomputer are present day personalcomputers such as IBM PC, PC-AT etc.

Micro computers can further be divided in toa) Desktop computers are larger and not meant to be portable. They usually sit in one place on a

desk or table and are plugged into a wall outlet for power.b) Laptop or notebook computers are small and lightweight enough to be carried around with

the user. They run on battery power, but can also be plugged into a wall outlet. They typicallyhave a built-in LCD display. They also feature a built-in keyboard and some kind of built-inpointing device (such as a touch pad).

c) A Personal Digital Assistant (PDA)/Digital Tablet is a handheld microcomputer that tradesoff power for small size and greater portability. They typically use a touch-sensitive LCD screenfor both output and input (the user draws characters and presses icons on the screen with astylus). PDAs communicate with desktop computers and with each other either by cableconnection, infrared (IR) beam, or radio waves. PDAs are normally used to keep track ofappointment calendars, to-do lists, address books, and for taking notes.

d) A Handheld PC, or H/PC for short, is a term for a computer built around a form factor which issmaller than any standard laptop computer. It is sometimes referred to as a Palmtop.These devices typically look more like a tiny laptop than a PDA, with a flip-up screen and smallkeyboard. They may use Windows CE or similar operating system for handheld devices.

e) Netbooks (also called mini notebooks or sub notebooks) are a rapidly evolving category ofsmall, light and inexpensive laptop computers suited for general computing and accessing webbased applications; they are often marketed as “companion devices,” that is, to augment auser’s other computer access

f) A tablet personal computer (tablet PC) is a portable personal computer equipped with atouch screen as a primary input device and designed to be operated and owned by an individual.The term was made popular as a concept presented by Microsoft in 2001, but tablet PCs nowrefer to any tablet-sized personal computer, regardless of the operating system.

g) The ultra-mobile PC (UMPC) is a specification for a small form factor of tablet PCs. It wasdeveloped as a joint development exercise by Microsoft, Intel, and Samsung, among others.

h) A workstation is a powerful, high-end microcomputer. They contain one or moremicroprocessor CPUs. They may be used by a single-user for applications requiring more powerthan a typical PC (for rendering complex graphics, or performing intensive scientificcalculations).

i) Workstation-class microcomputers may be used as server computers that supply files toclient computers over a network. This class of powerful microcomputers can also be used tohandle the processing for many users simultaneously who are connected via terminals

2) Mini Computer:A minicomputer (or simply a mini) is a class of multi-user computers that lies in the


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middle range of the computing spectrum, in between the smallest multi-user systems (mainframecomputers) and the largest single-user systems (microcomputers or personal computers).

This is designed to support more than one user at a time. It possesses large storagecapacity and operates at a higher speed. The mini computer is used in multi-user system inwhich various users can work at the same time.

This type of computer is generally used for processing large volume of data in anorganization. They are also used as servers in Local Area Networks (LAN).

Since personal computers are becoming more efficient and are available in many variants,this type of computers are now almost not common. Mini computer has thus been largely takenover by high-end microcomputer workstations which are capable of serving multiple users.

However the contemporary term for this class of system is midrange computer, suchas the higher-end SPARC, POWER and Itanium -based systems from Sun Microsystems, IBMand Hewlett-Packard.

3) MainframesThese types of computers are generally 32-bit microprocessors. They operate at very high

speed, have very large storage capacity and can handle the work load of very large number ofusers.

They are generally used in centralized database management of large organizations.They are also used as controlling nodes in Wide Area Networks (WAN). Example of mainframes

are DEC, ICL and IBM 3000 series.4) Supercomputer

These are the fastest and most efficient machines. They have high processing speedcompared to other computers. They are massive multiprocessing systems.

One of the ways in which supercomputers are built is by interconnecting hundreds ofmicroprocessors.

Supercomputers are mainly being used for weather forecasting, Molecular modeling,biomedical research, remote sensing, aircraft design and other areas of science andtechnology. Examples of supercomputers are CRAY YMP, CRAY2, NEC SX-3, CRAY XMP andPARAM made by India.

FURTHER READINGAn integrated circuit (IC) is a small electronic device made out of a semiconductor material.

The first integrated circuit was developed in the 1950s by Jack Kilby of Texas Instrumentsand Robert Noyce of Fairchild Semiconductor.

Computers are, in fact, all around us. Microprocessor chips are found in many electronicdevices (in our iPod, in our DVD player, in our microwave, in our car, in our phone). Almostevery electronicgadget has a Microprocessor in them.

The Rotating Wheel Calculator called Pascaline was developed by Blaise Pascal, whichis a predecessor to today’s electronic calculator.

Charles Babbage designed a Difference engine and was helped by Ada Lovelace. Hernotes on the engine include what is recognized as the first algorithm intended to be processedby a machine and as such she is regarded as the world’s first computer programmer. Babbageis credited with inventing the first mechanical computer that eventually led to more complexdesigns so he is Considered as “father of the computer”

Alan Mathison Turing was highly influential in the development of computer science andproviding a formalization of the concept of the algorithm and computation with the Turingmachine, playing a significant role in the creation of the modern computer and is known asFather of Computer science.


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The Simputer is a, handheld computer, designed for use in such areas where using personalcomputers are deemed inappropriate. Due to the low cost, it was also deemed appropriate to beused in rural areas and is often acclaimed as Computer for masses. The device was designedby the Simputer Trust, a non-profit organization formed in November 1999 by seven Indianscientists and engineers led by Dr. Swami Manohar.

Mainframes are often colloquially referred to as Big Iron are powerful computers usedmainly by large organizations for critical applications, typically bulk data processing suchas census, industry and consumer statistics, Enterprise resource planning(ERP), and financialtransaction processing.

IBM mainframes dominate the mainframe market at well over 90% market share. Unisysmanufactures ClearPath mainframes. Hitachi co-developed the zSeries z800 with IBM toshare expenses.

The performance or speed of Mainframes are measured in millions of instructions persecond (MIPS), but supercomputers are measured in floating point operations per second(FLOPS).

Seymour Roger Cray was a U.S. electrical engineer and supercomputer architect whodesigned a series of computers that were the fastest in the world for decades and also creditedwith designing first super computer Cray-II, and for this reason Called “the father ofsupercomputing.

Cray Jaguar is the fastest supercomputer at Oak Ridge National Laboratory TennesseeUSA in the world now.

Examples of special-purpose supercomputers:a. Belle, Deep Blue, and Hydra, for playing chessb. GRAPE, for astrophysics and molecular dynamicsc. Deep Crack, for breaking the DES cipherd. MDGRAPE-3, for protein structure computatione. D. E. Shaw Research Anton, for simulating molecular dynamicsPetascale” supercomputers can process one quadrillion (1015) (1000 trillion) FLOPS.

Exascale is computing performance in the exaflops range. An exaflop is one quintillion (1018)FLOPS (one million teraflops).

PARAM is a series of supercomputers designed and assembled by the Centre forDevelopment of Advanced Computing (C-DAC) in Pune, India. The latest machine in theseries is the PARAM Yuva. Others include PARAM 10000 and PARAM 9000/SS and the PARAMPadma. The PARAM Padma was India’s first Teraflop supercomputer. Currently, C-DAC isdeveloping a Petaflop Supercomputer which is expected to be in operation by 2012.

EKA is a supercomputer built by the Computational Research Laboratories under TATAswith technical assistance and hardware provided by Hewlett-Packard. When it was installed inNovember 2007, it was the 4th fastest in the world and fastest in Asia. As of June 2010, it isranked as the 33rd fastest in the world and fourth fastest in Asia. Eka is the Sanskrit namefor number one.

Fast Moving Consumer Goods (FMCG) or Consumer Packaged Goods (CPG) are productsthat are sold quickly at relatively low cost. Examples include non-durable goods such as softdrinks, toiletries, grocery items etc.

COMPUTER ORGANISATIONBASIC COMPUTER OPERATIONS

A computer can perform basically five major operations or functions irrespective of their sizeand make. These are 1) it accepts data or instructions by way of input, 2) it stores data, 3) it can


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process data as required by the user, 4) it gives results in the form of output, and 5) it controlsall operations inside a computer. The various stages of it’s operation are as follows:

1) INPUTThis is the process of entering data and programs in to the computer system.Computer is an electronic machine and takes inputs raw data and performs some processing

giving out processed data.2) STORAGE

It is the process of saving data and instructions perma-nently is known as storage.Data has to be fed into the system before the actual processing starts. It is because the

processing speed of Central Proc-essing Unit (CPU) is so fast that the data has to be providedto CPU with the same speed. Therefore the data is first stored in the storage unit for fasteraccess and processing.

This storage unit or the primary storage of the computer system (called RAM and ROMmemory) is designed to do the above functionality. It pro-vides space for storing data andinstructions.

The storage unit performs the following major functions :All data and instructions are stored here before and after processing.Intermediate results of processing are also stored here.

3) PROCESSINGThe task of performing operations like arithmetic and logical operations is called

processing.The Central Processing Unit (CPU) takes data and instructions from the storage unit and

makes all sorts of calculations based on the instructions given and the type of data provided. Itis then sent back to the storage unit.

4) OUTPUTThis is the process of producing results from the data for getting useful information.Similarly the output produced by the computer after processing must also be kept somewhere

inside the computer before being given to us in human readable form.Again the output is also stored inside the computer (Normally in secondary storage devices

like Hard disk etc for further proc-essing.5) CONTROL

The manner how instructions are executed and the above operations are performed. Controlling of all operations like input, processing and output are performed by control

unit.It takes care of step by step processing of all operations in side the computer.

COMPONENTS OF A COMPUTERA computer system accepts data as input processes that data and provides data as output.During the processing the data must be stored. The processing is controlled by a sequence ofinstructions - the program - which is stored in the computer. The basic components of acomputer system are therefore input devices, processor, backing storage devices and outputdevices.


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SCHEMATIC REPRESENTATION OF A COMPUTER SYSTEMEach of the components shown in the above diagram have unique contribution to make.These can be summarized as follows:Input DevicesInput devices accept data, convert data into machine readable form and transmit data to theprocessor unit. Ex Key Board, Mouse etcCentral Processing Unit (CPU)In order to carry out the operations mentioned above, the computer allocates the taskbetween its various functional units. The Central processing unit is divided into twounits for its operation. They are 1) arithmetic logical unit (ALU), 2) control unit (CU). It is justlike brain that takes all major decisions, makes all sorts of calculations and directs differentparts of the computer functions by activating and controlling the operations. CPU is thuscalled as the brain of any computer system.o Arithmetic Logical Unit (ALU)

After we enter data through the input device, it is stored in the primary storage unit.The actual processing of the data and instruction are performed by Arithmetic Logical Unit.The major operations performed by the ALU are addition, subtraction, multiplication,

division, logic and comparison.Data is transferred to ALU from storage unit when required. After processing the output is

returned back to storage unit for further processing or getting stored.o Control Unit (CU)

The next component of computer is the Control Unit, which acts like the supervisor seeingthat things are done in proper fashion.

The control unit determines the sequence in which computer programs and instructionsare executed.

Things like processing of programs stored in the main memory, interpretation of theinstructions and issuing of signals for other units of the computer to execute them etc are takencare of by Control Unit.

It also acts as a switch board operator when several users access the computersimultaneously. Thereby it coordinates the activities of computer’speripheral equipment as they perform the input and output.

Therefore it is the manager of all operations within the computer.The Memory unit

As discussed earlier that the basic function performed by a computer is the executionof a program. The program which is to be executed is a set of instructions which are stored


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in memory unit. The central processing unit (CPU) executes the instructions of the program tocomplete a task. The memory unit comprises the Main or primary memory unit and secondaryor back up memory unito The Primary Memory

This unit stores programs during their execution, stores data that are being used bythe current program, and stores the operating system which controls the operation of thecomputer system.

The Primary Memory Primary memory consists of Random Access Memory (RAM), wherethe programs (and their data) must be stored in order to be run, and

Read Only Memory (ROM), where permanent programs and data are built in by themanufacturer for starting (Booting a computer).o Secondary or backing Memory or storage Unit

It maintains a permanent record of data and programs, maintains a store for the programand data being processed if the main memory cannot accommodate the data and program,and acts as an input/output device. Ex: Hard disk, floppies etcOutput Devices

Accept data from the processor, and convert data into the required output format. Inother words, output devices translate the data in the processor into a human readable formatthat means which is suitable for people to use. Ex: Monitor, Printer etc.

The hardware devices attached to the computer are called peripheral equipments. Thesesinclude all input, output and secondary storage devices which are attached externally toa computer.

THE PROCESSING AND MEMORY STORAGEProcessing the digital data

Inside the computer, the steps followed are quite different from what we see on the monitoror screen. How will it process data will depend on the program. In computer’s memory bothprograms and data are stored in the binary form (Digits).

A computer program (also a software program, or just a program) is a sequence ofinstructions written to perform a specified task for a computer

As human beings we all understand decimal system but the computer can only understandbinary system. The binary system has only two values 0 and 1. These are called bits (Binarydigits).

It is because a large number of integrated circuits inside the computer which can be consideredas switches, which can be meant ON, or OFF.

If a switch is ON it is considered 1 and if it is OFF it is 0. So 1 bit = one on or off position.1 byte = 8 bits.So 1 byte can be one of 256 possible combinations of 0 and 1.Since Each 1 is a power of 2 so that the digits in the figure( 10101100) represent the Decimal number:

= 2 7 + 0 + 2 5 + 0 + 2 3 + 2 2 + 0 +0 = 128 +0 +32 + 0 + 8 + 4 + 0 + 0 = 172

Thus every command and every input is converted intodigital data, a string of 0’s and 1’s. So the computer takesinput in the form of 0 and 1 and gives output in the form 0and 1 only.


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If the computer gives outputs as 0’s & 1’s only and it can very well be translated in tohuman understandable decimal system, since every number in binary system can be convertedto decimal system and vice versa; for example, the above decimal number 172 meaning decimal10101100.

Therefore it is the computer that takes information or data in decimal form from us, convertit in to binary form, process it producing output in binary form and again convert the output todecimal form.

How is the Processing done?1. The central processing unit (CPU) is the portion of a computer system that carries out the

instructions of a computer program, and is the primary element carrying out the computer’sfunctions so is called Brain of a computer

The central processing unit carries out each instruction of theprogram in sequence, to perform the basic arithmetical, logical,and input/output operations of the systemThus the CPU, or Central Processing Unit, is the part of thecomputer where work gets done finally. In most computers, thereis one processing chip.Main Memory stores the commands (In the form of preloadedsoftware) that the CPU executes and the results.Two typical components of a CPU are the following:

2. The arithmetic logic unit (ALU), which performs arithmetic and logical operations such asadd, subtract, multiply, divide or one of the logical comparisons such as greater than, lessthan, equal to, not equal to etc. A command must be either a basic arithmetic operation.Everything else has to be broken down into these few operations by ALU. Only one operation isdone in each Machine Cycle. The ALU can only do one thing at a time but can work very, veryfast

3. The control unit (CU), which extracts instructions from memory and decodes and executesthem, and calling on the ALU whenever necessary. It controls the entire Machine Cycle andhence called Manager of a Computer.

PROCESSING: MACHINE CYCLEWhen we run a program which is stored in a hard disk, here is what happens:

The program is a series of instructions, which are stored inside the hard disk drive, aretransferred to the RAM memory.

The CPU, using a circuit called memory controller, loads the program data from the RAMmemory.

The data, which is now inside the CPU, gets processed in a typical cyclic way.The computer can only do one thing at a time. Each action must be broken down into the

most basic steps. One round of actions from getting an instruction and back to gettingthe next instruction is called the Machine Cycle. It takes numerous cycles to do even asimple addition of two numbers.

THE MACHINE CYCLEFetch - get an instruction from Main MemoryDecode - translate it into computer commandsExecute - actually process the commandStore - write the result to Main Memory


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What happens next will depend on the program. The CPU could continue to load andexecuting the program or could do something with the processed data, like displaying somethingon the screen.

Let us for example assume that computer has a program in the computer to add thenumbers 5 and 6 and on running that program the typical machine instructions will be asfollows.1. Fetch instruction : “Get number at address 123456” (From main memory)2. Decode instruction.3. Execute : ALU finds the number. (This happens to be 5)4. Store : The number 5 is stored in a temporary spot in Main Memory.5 - 8 Repeat steps for another number (= 6)9. Fetch instruction : “Add those two numbers”10.Decode instruction.11.Execute : ALU adds the numbers.12.Store : The answer is stored in a temporary spot.13.Fetch instruction : “Display answer on screen.”14.Decode instruction.15.Execute : Display answer on screen.

How are the instructions held in memory?Memory in a computer system is required for storage and subsequent retrieval of the

instructions and data. A computer system uses variety of devices for storing the instructionsand data which are required for its operations.

As already discussed that when we run a program which is a series of instructions, whichare stored inside the hard disk (A memory device), those instructions are transferred to anothermemory location called RAM memory.

Primary memory consists of semiconductor memory chips and is used to store the dataand programs currently in use.

Since each storage element of memory is directly (randomly) accessible and can beexamined and modified without affecting other cells and hence such memory is calledRandom Access Memory (RAM).

Main memory stores a variety of critical information required for processing by the CPU.How does a computer store the information?

A computer works by electrical impulses. Hence a binary number system which uses onlytwo digits, namely, 0 and 1 is a convenient way to represent information inside a computer. Wewould use the symbol ‘1’ to represent the presence of an electrical pulse and the symbol ‘0’ torepresent the absence of it.

Information in a computer consists of ‘Data’ (numerical and non-numerical) and‘Instructions’ which are made up of a large number of characters, namely, decimal numbers0 to 9, alphabets A to Z, arithmetical operators like (+), (-) etc., relational operators like(=), (<), etc. and many other special characters like (,), (;), etc.

Computers use eight binary digits or bits (Which make up 1 byte) to represent informationinternally. This allows up to 28=256 different characters to be represented uniquely. Acollection of eight bits is called a byte.

The memory unit stores all the information in memory cells, also called memorylocations, in binary digits.

We need a method of naming the places where Main Memory stores data.


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Each location needs a unique name, just like houses in a town need a unique street address.Each memory location has thus a unique address. Now when the program is run, the instructions which are stored in memory location as bits

of data are provided to the central processing unit (CPU) by referring to the address of thememory location. The amount of information that can be held in the main memory is knownas memory capacity. A memory address holds 1 byte of data where -

1 bit = 0 or 1, on or off

1 byte = 8 bits

1 kilobyte (K or KB) 1024 bytes or 210 bytes

1 megabyte (MB) 1024 kilobytes or 10242 bytes or 220 bytes

1 gigabyte (GB) 1024 megabytes or 10243 or 230 bytes

terabyte (TB) 1024 gigabytes or 10244 bytes, or 240 bytes

petabyte (PB) 1024 terabytes or 10245 bytes 250 bytes

zettabyte (ZB) 1024 peta bytes or 10246 bytes 270 bytes

yottabyte (YB) 1024 zetta bytes or 10247 bytes 280 bytes

Factors affecting the Speed of ProcessingMany different factors determine how fast the computer can get the things done. They are-o Processor speed

Clock speed or rate is the speed at which a microprocessor executes instructions.Every computer contains an internal clock that regulates the rate at which instructions are

executedand synchronizes all the various computer components.The CPU requires a fixed number of clock ticks (or clock cycles) to execute each instruction.The faster the clock, the more instructions the CPU can execute per second.Clock speeds are expressed in megahertz (MHz) or millions of pulses a second/ or gigahertz

(GHz) where 1 GHz = 1 billion cycles per second.If a computer is a 6.4 GHz processor. It’s clock rate is 6.4 billion cycles per second.Clock speed depends on the internal architecture of a CPUSome microprocessors are superscalar, which means that they can execute more than one

instruction per clock cycle.o Bus width

A BUS is a collection of wires through which data is transmitted from one part of acomputer to another. We can think of a bus as a highway on which data travels within acomputer.

When used in reference to personal computers, the term bus usually refers to internal bus.This is a bus that connects all the internal computer components to the CPU and mainmemory.

There’s also an expansion bus that enables expansion boards to access the CPU andmemory.

All buses consist of two parts — an address bus and a data bus. The data bus transfersactual data whereas the address bus transfers information about where the data shouldgo.

The size of a bus, known as its width, is important because it determines how much datacan be transmitted at one time. For example, a 16-bit bus can transmit 16 bits of data, whereas


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a 32- bit bus can transmit 32 bits of data.Every bus has a clock speed measured in MHz. A fast bus allows data to be transferred

faster, which makes applications run faster. On PCs, the old ISA bus is being replaced byfaster buses such as PCI (Peripheral Component Interconnect, a local bus standard developedby Intel Corporation).

Nearly all PCs made today include a local bus for data that requires especially fast transferspeeds, such as video data. The local bus is a high-speed pathway that connects directly tothe processor.o Word size

A word is the amount of data the CPU can process at one time. An 8-bit processor canmanipulate 8 bits at a time. Processors can be 8-, 16-, 32-, or 64-bit so far. So Bigger thenumber = faster processing

The size of a word varies from one computer to another, depending on the CPU. For computerswith a 16-bit CPU, a word is 16 bits (2 bytes). On large mainframes, a word can be as long as 64bits (8 bytes)

MEMORY HIERARCHYMemory usually refers to a form of semiconductor storage known as Random-Access Memory,and other forms of fast but temporary storage which is directly accessible by the CPU.Similarly, Memory storage today more commonly refers to storage devices and their medianot directly accessible by the CPU which is called secondary or tertiary storage or AuxiliaryMemory. However Historically, memory has been called main memory, real storage or internalmemory while storage devices such as hard disc, have been referred to as secondary storage,external memory or auxiliary/peripheral storage. A memory system in a computer can beconsidered to consist of the following groups of memories. These are:I. Primary Memory or Main Memory or System main memory:

Primary storage, simply known as memory, is the only memory directly accessible tothe CPU. The CPU continuously reads instructions stored there and executes them.

This memory unit stores all the information in memory cells also called memory locations,in binary digits. Each memory location has a unique address. The contents of the desiredmemory locations are provided to the central processing unit by referring to the address of thememory location.

Main memory is directly or indirectly connected to the CPU via a memory bus, todaysometimes referred to as a front side bus (FSB).The CPU continuously reads instructionsstored there and executes them.

The amount of information that can be held in the main memory is known as memorycapacity. The capacity of the main memory is measured in kilobytes (KB) or Megabytes (MB).All modern computers use semiconductor memory as its main memory.

The following are the sub-layers of the primary storage.1) Random Access Memory (RAM):

It is a Primary memory consists of semiconductor memory chips and is used to store thedata and programs currently in use.

The CPU continuously reads instructions stored there and executes them. Each storageelement of memory is directly (randomly or in any sequence) accessible and can be examinedand modified without affecting other cells and hence primary memory is often referred to asRandom Access Memory (RAM).

This memory stores a variety of critical information required for processing by the CPU. RAMis an immediate and temporary memory where data pertaining to the current program isloaded temporarily for the CPU to interact with it, retrieve data stored therein, and to go


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through instructions and execute them as per the requirement of the current program.Data and application are loaded there in uniform manner and CPU accesses (Read) and

modifies (Write) such data in any fashion (randomly), so called Random Access Memory.However this memory is Volatile that means it requires continuous supply of power for

the memory to be retained or else the memory is lost/ erased automatically. If the computerwas to be turned off anything stored currently in RAM would be erased.

Because of RAM’s volatile nature users must frequently save their work to a permanentmedium, such as a hard drive, which is non-volatile to avoid losing data if the system’s poweris interrupted. The following are the different types of RAMsI. Dynamic random access memory (DRAM) is a type of Random access memory that storeseach bit of data in a separate capacitor within an integrated circuit. Because of this design,these cells must be refreshed with new electricity every few milliseconds allowing the memoryto keep its charge and hold the data as long as needed.II. Static random access memory (SRAM) is a type of semiconductor memory where theword static indicates that it, unlike Dynamic RAM (DRAM), does not need to be periodicallyrefreshed.III. DDR RAM- Double Data Rate RAM is a double pumped, dual-pumped, and double transitionhigh speed data transfer used in high end computers.IV. DDR SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory) is aclass of RAM to achieve nearly twice the bandwidth of the single data rated RAMs.

2) Internal Processor Memories (Registers)These consist of the small set of high speed memory cells namely registers which are

located on a processor itself and are used as temporary locations where actual processing isdone.

Processor registers, are a kind of switching transistors integrated on the CPU’s chip whichare the fastest forms of memory devices in a computer, and contain a word of data (usually32 or 64 bits).

The CPU instructs and helps the Arithmetic and logic unit to perform a number of calculationson this data or with the help of it.

3) Processor cache or Cache Memory or Buffer MemoryCache Memory which is meant for enhancing the performance of the computer links the

fast registers to the slower main memory.Cache is a memory unit used by the central processing unit of a computer to reduce the

average time to access memory.The cache is a smaller, faster memory which stores copies of the data from the most

frequently used main memory locations.Cache memory loads the duplicated information that is used most actively and

repetitively.When the processor needs to read from or write to a location in main memory, it first

checks whether a copy of that data is in the cache. If so, the processor immediately readsfrom or writes to the cache, which is much faster than reading from or writing to main memory(RAM).

It is much faster than the main memory but relatively can store limited data. It is alsomuch slower but much larger than the processor registers.

Cache setup is further split into different levels with smallest and fastest primary cachesnamely L1 cache, L2 cache, and L3 cache.

4) Non-volatile primary memory or Read-Only Memory (ROM)


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Usually known by its acronym, ROM is a class of Memory unit used in computers and otherelectronic devices. ROM is the memory that is capable of holding data and being read from.

However, it is not capable of being written to or having its data modified by either theUser or the Processor.

Unlike RAM, ROM is non-volatile and capable of keeping its contents regardless if ithas power or not. Because of that data stored in ROM, cannot be modified, it is mainly used inBIOS which is a chip located on all computer motherboards that contains instructions andsetup for how our system should boot and how it operates.

It is also used to distribute firmware (software that is very closely tied to specific hardwareand is provided by the firm in a non modifiable format).

However, more modern types such as EPROM and flash EEPROM can be erased andre- programmed multiple times; they are still described as “read-only memory” becausethereprogramming process is generally infrequent, comparatively slow, and often does not permitrandom access writes to individual memory locations, which are possible when reading a ROM.

Use of ROM for program storage :Every stored-program computer requires some form ofnon-volatile storage to store the initial program that runs when the computer is powered on orotherwise begins execution (a process known as bootstrapping, often abbreviated to “booting”or “booting up”)

Types of ROMThese are Classic mask-programmed ROM chips and are integrated circuits that physicallyencode the data to be stored, and thus it is impossible to change their contents afterfabrication. Other types of non-volatile solid-state memory permit some degree ofmodification. These are

Programmable read-only memory (PROM), or one-time programmable ROM (OTP), canbe written to or programmed via a special device called a PROM programmer. Typically, thisdevice uses high voltages to permanently destroy or create internal links (fuses or anti fuses)within the chip. Consequently, a PROM can only be programmed once.

Erasable programmable read-only memory (EPROM) can be erased by exposure to strongultraviolet light (typically for 10 minutes or longer), then rewritten with a process that againrequires application of higher than usual voltage. Repeated exposure to UV light willeventually wear out an EPROM

Electrically erasable programmable read-only memory (EEPROM) is based on a similarsemiconductor structure to EPROM, but allows its entire contents (or selected banks) to beelectrically erased, then rewritten electrically, so that they need not be removed from the computer(or camera, MP3 player, etc.). Writing or flashing an EEPROM is much slower (milliseconds perbit) than reading from a ROM or writing to a RAM (nanoseconds in both cases).

Electrically alterable read-only memory (EAROM) is a type of EEPROM that can be modifiedone bit at a time. Writing is a very slow process and again requires higher voltage (usuallyaround 12 V) than is used for read access. EAROMs are intended for applications that requireinfrequent and only partial rewriting.

Flash memory (or simply flash) is a modern type of EEPROM invented in 1984.Flash memorycan be erased and rewritten faster than ordinary EEPROM, and newer designs feature very highendurance (exceeding 1,000,000 cycles). Flash memory is sometimes called flash ROM or flashEEPROM when used as a replacement for older ROM types, but not in applications that takeadvantage of its ability to be modified quickly and frequently.

II. Secondary Memory/Auxiliary Memory/Backing StoreAuxiliary memory in fact is much larger in size than main memory but is slower than

main memory.


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It normally stores system programs (programs which are used by system to performvarious operational functions), other instructions, programs and data files. Hard disks, opticaldisc, magnetic tape are some of the Secondary storage devices.

Some other examples of secondary storage technologies are: flash memory (e.g. USB flash(Pen) drives or keys), floppy disks, magnetic tape, paper tape, punched cards, standalone RAMdisks, and Zip drives.

The secondary storage is often formatted according to a file system format, whichprovidesthe abstraction necessary to organize data into files and directories, providing alsoadditional information (called metadata) describing the owner of a certain file, the accesstime, the access permissions, and other information.

The concept of virtual memory is one of the most important memory management schemeadopted in modern computer operating systems.

Virtual memory is the process of allowing utilization of more primary storage capacitythan is physically available in the system. As the primary memory fills up, the system movesthe least-used chunks ( called pages) to secondary storage devices (to a swap file or page file),retrieving them later when they are needed

In computer operating systems, paging is one of the memory-management schemes bywhich a computer can store and retrieve data from secondary storage for use in mainmemory. In the paging memory-management scheme, the operating system retrieves data fromsecondary storage in same-size blocks called pages.

Different Characteristics of Memory devicesNon-volatile memory: Will retain the stored information even if it is not constantly

supplied with electric power. It is suitable for long-term storage of information. Nowadaysused for most of secondary, tertiary, and off-line storage. In 1950s and 1960s, it was alsoused for primary storage, in the form of magnetic core memory. Ex: Memory in ROM,BIOSchips etc

Volatile memory: Requires constant power to maintain the stored information. The fastestmemory technologies of today are volatile ones (not a universal rule). Since primary storage isrequired to be very fast, it predominantly uses volatile memory. Ex: RAM, Cache Memory etc.

Dynamic Memory: A form of volatile memory which also requires the stored informationto be periodically re-read and re-written, or refreshed, otherwise it would vanish. Ex: Themain memory (the “RAM”) in modern personal computers is Dynamic RAM (DRAM)

Static Memory: A form of volatile memory similar to DRAM with the exception that it doesnot refresh on occasion. Ex: SRAM used in some personal computers, workstations, routers andperipheral equipment like printer.

Read/write storage or mutable storage: It Allows information to be overwritten at anytime. Ex: Floppy Disc, Zip etc.

Read only storage –It Retains the information stored at the time of manufacture, and writeonce storage (Write Once Read Many -WORM) allows the information to be written only onceat some point after manufacture. These are called immutable storage. Immutable storage isused for tertiary and off-line storage. Examples includei. CD-ROM which is a pre-pressed compact disc that contains data accessible to, but not

writable by, a computerii. CD-R. (Compact Disc-Recordable) is an optical medium, where the whole disk does not

have to be entirely written in the same session.Slow write, fast read storage: It is a Read/write storage which allows information to be

overwritten multiple times, but with the write operation being much slower than the readoperation.


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i. Examples include CD-RW (Compact Disc-Rewritable)ii. Flash memory which is a non-volatile computer storage chip that can be electricallyerased and reprogrammed. Ex: Flash drives, Jump drives and pen drives are USB storagedevices based on flash memory. It is primarily used in memory cards, USB flash drives, MP3players

Random Access Memory: Any location in storage can be accessed at any moment inapproximately the same amount of time in any fashion or order. Such characteristic is wellsuited for primary and secondary storage. Ex: RAM, Hard disk drive etc

Sequential Access Memory It allows the accessing of information in a serial order, one after the other; therefore the

time to access a particular piece of information depends upon which piece of information waslast accessed. Ex: A tape drive is an example of a sequential access drive, where the drive mustmove the tape forward or backward until it reaches its destination.

Types of Secondary storage devicesSemiconductor storageSemiconductor memory uses semiconductor-based integrated circuits to store information.A semiconductor memory chip may contain millions of tiny transistors or capacitors. Bothvolatile and non-volatile forms of semiconductor memory exist. In modern computers, primarystorage almost exclusively consists of dynamic volatile semiconductor memory or dynamicrandom access memory (DRAM).Magnetic storageMagnetic storage uses different patterns of magnetization on a magnetically coated surface tostore information. Magnetic storage is non-volatile. In modern computers, magnetic storagecomprises of :o Floppy disk, used for off-line storageo Hard disk drive(HDD),used for secondary storageo Magnetic tape data storage, used for tertiary and off-line storage In early computers,magnetic storage was also used for primary storage in a form ofmagnetic drum, or core memory.Optical storageOptical storage is the typical optical disc, which stores information in deformities on thesurface of a circular disc and reads this information by illuminating the surface with alaser diode and observing the reflection. Optical disc storage is non-volatile. The deformities may be permanent (read only media),formed once (write once media) or reversible (recordable or read/write media). The followingforms are currently in common use

CD, CD-ROM, DVD, Blue ray Disc (BD-ROM): Read only storage, used for massdistribution of digital information (music, video, computer programs)

CD-R, DVD-R, DVD+R, BD-R: Write once storage, used for tertiary and off-line storageCD-RW, DVD-RW, DVD+RW, DVD-RAM, BD-RE, High Definition RE (HD-RE) : Slow write,

fast read storage, used for tertiary and off-line storageUltra Density Optical or UDO is similar in capacity to BD-R or BD-RE and is slow write,

fast read storage used for tertiary and off-line storage.Network StorageA secondary or tertiary storage may connect to another computer utilizing computer networks.

Direct-attached storage (DAS) is a traditional mass storage that does not use anynetwork. This is still a most popular approach.


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Network-attached storage (NAS) is mass storage attached to a computer which anothercomputer can access at file level over a local area network, a private wide area network(PWAN),or in the case of online file storage, over the Internet.

Storage area network (SAN) is a specialized network that provides other computerswith storage capacity. The crucial difference between NAS and SAN is the former presents andmanages file systems to client computers, whilst the latter provides access at block-addressing(raw) level, leaving it to attaching systems to manage data or file systems within the providedcapacity. SAN is commonly associated with Fibre Channel networks.

COMPUTER SOFTWAREWHAT IS SOFTWARE?

We know computer cannot do anything without instructions from the user. In order todo any specific job we have to give a sequence of instructions to the computer. This set ofinstructions is called a computer program.

Software refers to the set of computer programs, procedures that describe the programs,how they are to be used.

It is the collection of programs, which increase the capabilities of the hardware.Software guides the computer at every step where to start and stop during a particular job.

The process of software development is called programming.Software and hardware are complementary to each other. Both have to work together toproduce meaningful result.

SOFTWARE TYPESComputer software is normally classified into two broad categories.

o Application Softwareo System software

I. Application SoftwareApplication Software is a set of programs to carry out operations for a specific application.

For example, payroll is application software for an organization to produce pay slips as anoutput. Application software is useful for word processing, billing system, accounting, producingstatistical report, analysis of numerous data in research, weather forecasting, etc.

Most applications allow the production and editing of documents (which are the data filescreated by the application programs). The document files (such as a report created in Word, ora PowerPoint presentation, or a excel spreadsheet) can then be printed, displayed on ascreen.

Applications (and other programs) are stored in computer as executable files (.exe fileswhich contain program steps that the computer can understand and execute) documentsare stored as data files.§ Some programming languages are suitable for developing some application programs. Amongthe programming languages COBOL (Common Business Oriented Language) is more suitablefor business application whereas FORTRAN (Formula Translation) is useful for scientificapplication.Some common application software on personal computers include:a) A word processor- A word processor (such as MS Word or Word Perfect) allows us to typeand format text (as well as some graphics) to create reports, letters, etc. Formatting optionsinclude changing the text size, font (typeface), line spacing, and page margins. We may alsodefine styles. We can also use document templates that contain pre-made formatting, styles,and content which allows us to create a document quickly without repeating work unnecessarily.


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b) Word and the other products of the Microsoft Office Suite of programs (including Excel,Access, and PowerPoint) can exchange data using OLE (Object Linking and Embedding).This integration of the programs allows us to copy a chart from Excel into a Word documentc) Desktop Publishing software (such as QuarkXPress and Adobe) go beyond word processors,giving us more control over the typesetting and graphic placement of a document. DTP softwareis used to layout books, magazines, newsletters, complex reports, etc.d) Spreadsheet software (such as MS Excel) allows the user to do numerical calculationsand produce charts of the results.

In a spreadsheet program, the user works in a worksheet consisting of rows and columns(labeled with numbers and letters).

The intersection of each row and column is a cell that can contain text, numbers, orformulas. The formulas use the contents of other cells to calculate new results; but theformulas use the cell reference (the row & column location of the cell) and not the contentsof the cell — so if the contents of a cell is changed, all dependent formulas automaticallyrecalculate their results. This gives the user to perform “what if” experiments with a complexcalculation.e) Database management software (such as MS Access or FileMaker Pro) allows users tomanipulate large amounts of information and retrieve any part of the information that isof interest.

A structured database contains data tables that are arranged in a uniform structure ofrecords and fields. An example would be a listing of a company’s customers (and the informationabout each one), and a listing of all orders placed by those customers.

A different type of database is free-form, and does not have the rigid structure forcategorizing the information (the World Wide Web, for example, is a huge collection of dataarchives with no common structure).f) Graphics software (such as Adobe Photoshop, coral draw and Illustrator) are used tocreate digital media art images and illustrations, or to edit digital images from scanners ordigital cameras.g) Presentation software (such as MS PowerPoint) is used to create presentations of slidescontaining text and graphics (and also incorporating sound and visual effects). Thesepresentations can be projected from a computer display projection unit, or the slides can beprinted out onto transparencies.h) Web authoring software (such as Dream weaver or GoLive) allows users to create complexweb pages without the user having to know XHTML or CSS or JavaScript. The user simplyinserts text and graphics into a WYSIWYG (what you see is what you get) editing window tolayout the material as desired, and the application software write the necessary web page codein the background.i) Integrated software packages (such as AppleWorks or Microsoft Works) combine severaldifferent application program functions (such as word processor, spreadsheet, database,graphics, and presentation) into one application. The individual modules of the packagesare not as powerful as the separate applications in the MS Office Suite, for example, but theymay provide the home user with the functionality they need at a much cheaper price.

II. System Software This is a set of programs that has to be fed to the computer for operation of computer

system as a whole.When we switch on the computer the programs written in ROM is executed which activates

different units of computer and makes it ready for us to work on it. This set of program canbe called system software.


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Therefore system software may be defined as a set of one or more programs designed tocontrol the operation of computer system.

System software controls a computer’s operations and manages a computer’s resources.System software includes the operating system (OS), utilities, and computer programmingtools.

System software are general programs designed for performing tasks such as controllingall operations required to move data into and out of the computer. It communicates withprinters, card reader, disk; tapes etc. monitor the use of various hardware like memory, CPUetc.

Also system software is essential for the development of applications software. SystemSoftware allows application packages to be run on the computer with less time and effort.It is not possible to run application software without system software.Some of the important system softwareOperating system (OS)

The operating system (OS) controls the allocation of hardware resources such as memoryspace and CPU processing time, and handles the basic input and output (I/O) for data flowingfrom and to storage devices (such as hard disks) and peripherals (such as your keyboard).

The operating system allows application software to access system resources withoutthe applications having to know the details about the system hardware.

The operating system often allocates resources and processing time between severalprograms which are running at once, which is called multitasking.

Multitasking allows us to perform multiple tasks at the same time, such copying achart from an open Excel document and pasting it into a report you have open in Word, all whileyour web browser is downloading a large file from the Internet in the background.

It is the OS that plays traffic cop in this situation, deciding which program gets time on theCPU when, and handles the flow of data.

The operating system also includes software that provides the user with an operatingenvironment for interacting with the computer. An operating environment could be acommand-line interface (requiring the user to type in commands to control the computer),or it could be a graphical user interface (GUI) that allows users to interact with the computerusing a mouse to point and click on icons, buttons, menus, etc.

IBM PC computers originally used the PC-DOS operating system also by Microsoft as MS-DOS. DOS is a general term that means “Disk Operating System” which is a command-lineinterface Operating system.

Modern PCs use (Graphical user Interface) GUI user environment like Microsoft Windowsoperating system such as Windows 2000 or Windows XP, Linux operating system, Unixetc.

Macintosh computers use some variation of the Macintosh OS, which is a GUI operatingsystem. Older macs may use Mac OS 9, but newer Macs use Mac OS X

High-end microcomputer workstations, file servers, and mainframes often run some variationof the UNIX operating system.DEVICE DRIVERSSystem software also includes the software needed to access a peripheral device connected tothe computer. Such software is called a device driver, and it controls I/O instructions to theperipheral devices. The device drivers may come already installed in the OS, or we have toinstall or update a driver when we add a new peripheral device.


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Virus checkerSystem software may also include security software, such as Virus checkers and firewalls. Avirus checker searches files for potentially harmful programs such as viruses, worms, or Trojanhorses that are written by malicious programmers.FirewallA firewall, or similar program like virus checker, protects computer from unauthorized accessover a network or telecom connection and also prevent users from doing such actionswhich may pose potential threat for the system resources. Now a days firewalls come in builtwith Operating Systems.UtilitiesUtilities are programs that perform a very specific task, usually related to managing systemresources such as disk drives, printers, etc. Unlike application software, utilities tend to besmaller in size and perform activities related to the computer system (scanning for viruses,manipulating file settings, scanning for disk errors, etc.). Some utilities are memory-residentprograms that are loaded into RAM and operate in the background.Software toolsSystem software also includes the tools used to write other programs. These include compilers,assemblers, and debuggers for various computer programming languages. A programminglanguage allows a person to write computer instructions in a language that is easier for a humanto understand, but which is then converted into the low level numerical instruction codesthat a computer processor unit can understand and execute. Some programming languagesinclude C, C++, Java, FORTRAN, COBOL, PASCAL, BASIC, and Visual Basic.

EXTENDED STUDY CONCEPTSOPERATING SYSTEM (OS)

It is a software that manages computer resources and provides programmers/users withan interface used to access those resources. Between the hardware and the application softwarelies the operating system. The operating system is a program that conducts the communicationbetween the various pieces of hardware like the video card, sound card, printer, themotherboard and the applications.

An operating system processes system data and user input, and responds by allocating andmanaging tasks and internal system resources as a service to users and programs of the system.

the operating system is not the first code to run on the computer at startup (boot) time.The initial code executing on the computer is usually loaded from firmware, which is stored inFlash ROM called the BIOS or boot ROM.

The firmware loads and executes the operating system kernel (usually from disk) and isusually responsible for the first graphics or text output the user sees onscreen.

The kernel is the central component of most computer operating systems (OS). Itsresponsibilities include managing the system’s resources (enabling the the communicationbetween hardware and software components).

Functions of Operating SystemAll operating systems must handle the same basic tasks. These functions can be divided intofour groups:1) Allocating System ResourcesThe operating system directs the traffic inside the computer, deciding what resources will beused and for how longa) Time: Time in the CPU is divided into time slices which are measured in milliseconds. Eachtask the CPU does is assigned a certain number of time slices. When time expires, another task


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gets a turn. The first task must wait until it has another turn. Since time slices are so small.Tasks can be assigned priorities so that high priority (foreground) tasks get more time slicesthan low priority (background) tasks.b) Memory: Memory must be managed also by the operating system. All those rotating turnsof CPU use leave data waiting around in buffers. Care must be taken not to lose data. One wayto help out the traffic jam is to use virtual memory. That means creating some memoryspace in hard disk to be used as a part main memory. While it is slower to put data on a harddisk, it increases the amount of data that can be held in memory at one time. When the memorychips get full, some of the data is paged out to the hard disk. This is called ‘swapping’. Operating system uses a swap file for this purpose

2) Input and output (I/O) controla) I/O Flow control is also part of the operating system’s responsibilities. The operating systemmust manage all requests to read data from disks or tape and writes all instructions to printers. b) To speed up the output to printers, most operating systems now allow for print spooling,where the data to be printed is first put in a file. This frees up the processor for other work inbetween the times data is going to the printer. A printer can only handle so much data at a time.Without print spooling we have to wait for a print job to finish before you can do anything else.With it you can request several print jobs and go on working. The print spool will hold all theorders and process them in turn.

3) Monitoring System Activitiesa) System performance: System performance would include response time (how long it takesfor the computer to respond when data is entered) and CPU utilization (comparing the time theCPU is working to the time it is idle.)b) System security Some system security is part of the operating system For multiple userswho are not all allowed access to everything, there must be a logon or login procedure wherethe user supplies a user name or ID and a secret password. An administrator must set up thepermissions list of who can have access to what programs and what data.

4) File and Disk Managementa) File management Keeping track of what files are where is a major job. So an operatingsystem comes with basic file management commands. A user needs to be able to createdirectories for storing files. A user needs to copy, move, delete, and rename files. This is thecategory of operating system functions that the user actually sees the most.b) Disk management A more technical task is that of disk management. Under some operatingsystems hard disk can be divided up, or partitioned into several virtual disks. The operatingsystem treats each virtual disk as though it were a physically separate disk. OS takes careof this function.Common Operating Systems

MS-DOS, Microsoft’s Disk Operating System, and its twin at IBM, PC-DOS, also written byMicrosoft are Text command interface OS

Microsoft Windows versions (95, 98, Me, NT, 2000, XP, Vista, and 7) are the most widelyacclaimed OS in the world.

Windows XP is an upgrade to Windows 2000. It is the world’s most popular Operatingsystem. It comes in two versions - Home and Professional. The word XP stands for Experience.The Professional version contains all the features of the Home version plus more business features,like networking and security features.

Windows Vista was released in early 2007. It has higher requirements for memory andprocessor speed than previous versions of Windows. Vista comes in several different flavors forhome and business purposes.


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Windows 7 was released in late 2009. There are several versions with differing prices.Apple Macintosh is a multitasking operating system that was the first graphical interface

to achieve commercial success. The Mac was an immediate success in the areas of graphicsproduction and DTP applications.

The current version is Mac OS X, which is version 10. Since January 2002, all new Maccomputers use Mac OS X. Subversions are named Jaguar, Panther, Tiger, Leopard.IBM’s 32-bit operating system, OS/2, was a popular system for businesses with complex

computer systems from IBM. It is no longer available.UNIX is an operating system developed by Bell Labs to handle complex scientific

applications. University networks are likely to use UNIX, as are Internet Service Providers. A lotof people have experience with UNIX from their college work. Many computer old-timers loveUNIX and its command line interface. But all those commands are not easy to remember fornewcomers.

Linux is an operating system similar to UNIX that is becoming more and more popular. It isan open-source program created by Linus Torvalds at the University of Finland, starting in1991. Open source means that the underlying computer code is freely available to everyone.Programmers can work directly with the code and add features. They can sell their customizedversion of Linux, as long as the source code is still open to others.

Operating system typesThe Concept of operating systems progressed and developed a lot that so many features arebeing added to improve their functionalities. The following is the list of OS with categories oftheir own. Many computer operating systems will fall into more than one of the below categories.

A command-line interface (CLI) operating system: command line is a user interface thatis navigated by typing commands at prompts. A prompt is either a text or symbols used torepresent the system’s readiness to perform the next command. For example, a MS-DOS promptor Windows command prompt may look like the below example. C:\Windows>

GUI – Short name for Graphical User Interface. a GUI Operating System contains graphicsand icons and is commonly navigated by using a computer mouse. Ex: windows all versions,GNOME, KDE, QNX Photon, CDE, GEM, Aqua

Some operating systems contain both features of GUI and CLI. Ex: Linux, UNIX. Thesesare command user interface in personal computers but can be graphical interface in X WindowSystem. The X Window System (commonly X or X11) is a computer software system and networkprotocol that provides a graphical user interface (GUI) for networked computers.

Multi-user - A multi-user operating system allows for multiple users to use the samecomputer at the same time and/or different times. With a multi-user system, a time-slice is theset amount of processing time each user gets. Below are some examples of multi-user operatingsystems.Ex: Linux, UNIX, Windows 2000

Multiprocessing - An operating system capable of supporting and utilizing more thanone computer processor. Ex: Linux, UNIX, Windows 2000

Multitasking - An operating system that is capable of allowing multiple software processesto run at the same time. Ex: Linux, UNIX, Windows 2000/XP

Multithreading - Operating systems that allow different parts of software program to runconcurrently. Ex: Linux, UNIX, Windows 2000/XP

Real-time operating system (RTOS) is a computer operating system designed to handleevents as they occur. Real-time is a term used to describe a process or event that occursimmediately or without being waited for. Real-time operating systems are commonly foundand used in robotics, complex multimedia and animation, communications and has various


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military and government uses. Some examples of real-time operating systems are WindowsCE, Chimera, Lynx, MTOS, QNX, RTMX, RTX, and VxWorks.

Server operating systems: It is the operating system that is widely used in servers or in thecentral computer of a network EX Windows NT/Server 2003/ Windows Server 2008, OS/2, OS/4 (By IBM)

Time sharing Operating System: The process of giving multiple users access to a systemor group of systems at the same time. With a time sharing setup, a computer gives users asmall portion of its processing power in pieces. This enables the computer’s processing power tobe more evenly distributed. Ex:Windows NT

Networking operating system an operating system designed to allow shared file and printeraccess among computers in a network, typically a local area network (LAN), a private network orto network. Examples include: Novell Netware, Windows NT.

64-bit operating system for mainframe computers - z/OS, produced by IBMChrome is an operating system based on the Linux kernel and designed by Google. Chrome

targets computer users that spend most of their time on the InternetHow does the sysytem boots?

The first screen that we see when we turn on our computer will be about the BIOS (BasicInput/Output System). The BIOS is a set of instructions on a ROM chip (Read-Only Memory)that controls how the hardware and the operating system communicate. It’s a very limitedset of instructions.

After the BIOS have gone through its start up routine, it runs the POST (Power on SelfTest). This is a set of tests of the hardware. If, for example, a keyboard is not plugged in or isbroken, a message about “Keyboard failure” will be beamed and the computer will stop where itis in the POST.

Next the computer looks for some kind of operating system that we have loaded earlier inthe computer and down load it from its destination disk(Either a hard disk or a bootableCD). This part of the operating system has various names. Kernel, master program, supervisor,control program are a few. In PCs using DOS or Windows the term kernel is used.

When the kernel is loaded, the computer looks for following three files:Command language interpreter- The command language interpreter is the program that

turns our key board strokes into all those 1’s and 0’s for the processor to understand.config.sys-From the config.sys the computer finds what devices are connected to the

computer, such as a mouse, CD drive, or scanner. The file tells where to look for the directions,called drivers, for using these devices.

autoexec.bat -This file does optional tasks like loading programs that we want to startevery time the computer is turned on (Called custom settings). This file also tells the computerwhere to look for files, called the path. Many programs add their own directories to the pathwhen they are installed. The more the custom settings the more time will it take for booting.

COMPUTER PROGRAMMING LANGUAGESProgramming Language Concepts

Language is a system of communication between people. These are the languages used tocommunicate among various categories of persons. But the computer will not understand anyof these natural languages for transfer of data and instruction. So there are artificial programminglanguages specially developed so that we could pass data and instructions to the computer todo specific job. A programming Language is a set of vocabulary and grammatical rules forinstructing a computer to perform specific tasks. So instructions or programs are writtenin a particular language based on the type of job. Each language has a unique set of keywords


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called Semantics (words that a computer understands) and a special syntax (Grammar forwriting program) for organizing program instructions. BASIC, C, C++, COBOL, FORTRAN, Ada,and Pascal etc are some of the examples of Programming Languages.

Programming LanguagesThere are two major types of programming languages. These are Low Level Languages andHigh Level Languages. Low Level languages are further divided in to Machine language andAssembly language.

1) Low Level LanguagesThe term low level means closeness to the way in which the machine has been built. Low levellanguages are machine oriented and require extensive knowledge of computer hardwareand its configuration.(a) Machine Language

It is also considered to the first generation language§ Sometimes referred to as machine code or object code, machine language is a collectionof binary digits or bits that the computer reads and interprets. Machine language is the onlylanguage a computer is capable of understanding.

It does not need any translator program and is called machine code/Native code and it iswritten as strings of 1’s (one) and 0’s (zero).

When this sequence of codes is fed to the computer, it recognizes the codes and convertsit in to electrical signals needed to run it. For example, a program instruction may look likethis: 1011000111101

This is a sequence of instructions written in the form of binary numbers consisting ofl s, 0s to which the computer responds directly.

An instruction prepared in any machine language will have at least two parts. The firstpart is the command or Operation, which tells the computer what functions, is to be performed.All computers have an operation code (op code) for each of its functions.The second part of the instruction is the operand or it tells the computer where to find or storethe data that has to be manipulated.Advantage

The only advantage is that program of machine language run very fast because no translationprogram is required for the CPU.Disadvantages1) It is very difficult to program in machine language. The programmer has to know details ofhardware to write program.2) Anybody going through this program will have a difficult task understanding the binarycoded instructions.3) The programmer has to remember a lot of codes to write a program which results in programerrors.4) It is difficult to detect and remove program errors (called debugging) from the program.

(b) Assembly Language/Symbolic Language.It is called second generation Language since it had improved the programming structure

and made it moderately easy programming language.We know that computer can handle numbers and letter only. Therefore some combination

of letters can be used to substitute for number of machine codes which are called Mnemonics.As we employ symbols (letter, digits or special characters) for the operation part, the address

part and other parts of the instruction code, this representation is also called symboliclanguage. This is considered to be the second-generation language.


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Assembly language uses structured commands as substitutions for numbers allowinghumans to read the code more easily than looking at binary. Although easier to read thanbinary, assembly language is still a complex language. For example a instruction in binary toadd some numbers looks like full of number jargaon. Instead to improve writing a programsome abbreviated words can be used such as “sub” (subtract), “div” (divide), “add” (add) and“mul” (multiply).

However ‘Mnemonics’ are the set of symbols and letters such as forms the AssemblyLanguage and a translator program is required to translate the Assembly Language to machinelanguage(Binary code). This translator program is called ‘Assembler’.

The following program is an example of an assembly language program for adding twonumbers X and Y and storing the result in some memory location.

From this program, it is clear that usageof mnemonics in our example LD,ADD,HALT are the mnemonics) hasimproved the readability of programsignificantly.Commonly used Assembly languagearchitecture are ARM, MIPS, x86

Advantages:1) The symbolic programming of Assembly Language is easier to understand and saves a lot of

time and effort of the programmer.2) It is easier to correct errors and modify program instructions than Machine language.3) Assembly Language has the same efficiency of execution as the machine level language. Because

this is one-to-one translator between assembly language program and its corresponding machinelanguage program.

Disadvantages:1) One of the major disadvantages is that assembly language is machine dependent. A program

written for one computer might not run in other computers with different hardware configuration.That means that it has no portability of being run on some other different configuration computer.

I. HIGH LEVEL LANGUAGESAssembly language and machine level language require deep knowledge of computer hardware

where as in higher language we have to know writing instructions in any human languagelike English and logic of the problem irrespective of the type of computer we are using.

A programming language such as C, FORTRAN, or Pascal that enables a programmer towrite programs those are more or less independent of a particular type of computer.

Such languages are considered high-levelbecause they are closer to human languagesand further from machine languages. Incontrast, assembly languages are consideredlow-level because they are very close tomachine languages.Higher level languages are simple languages that use Natural Languages and mathematical

symbols like +, -, %, / etc. for its program construction. The following is the sample programwritten in BASIC language to add two numbers.

However Instructions that were written in higher level language has to be convertedto machine language for the computer to understand. Programs written in a high-level


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language must be translated into machine language by a compiler or interpreter.a) Compiler

It is a program translator that translates the instruction of a higher level language tomachine language.tions for every program instructions of higher level language. Thus compileris a program translator like assembler but more sophisticated. Itscans the entire program first and then translates instructions intomachine code.

During the process of translation, the Compiler reads the source programs statementwise and checks the syntax (grammatical) errors. If there is any error, the computer generatesa printout of the errors it has detected. This action is known as diagnostics.

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

program.A compiler can translate only those source programs, which have been written, in that

language for which the compiler is meant for. For example FORTRAN compiler will not compilesource code written in COBOL language.

b) InterpreterAn interpreter is another type of program translator used for translating higher level

language into machine language. It takes one statement of higher level languages line by line, and translate it into

machine language line by line and then executes it. Translation and execution are carried out for each statement. It differs from compiler, which

translatethe entire source program where as it does involve in line by line translation.The advantage of interpreter compared to compiler is its fast response to changes in

source program. It eliminates the need for a separate compilation after changes to each program. Interpreters are easy to write and do not require large memory in computer. The disadvantage of interpreter is that it is time consuming method because each time a

statement in a program is first translated and then executed. Thus compiled machine languageprogram runs much faster than an interpreted program.

Difference betweenCompiler and InterpreterCompiler Interpreter1. Scans the entire program first and then 1. Translates the program line by line.Converts the entire program to machine code;

2. when all the syntax errors are 2. Each time the program is executed, every line isremoved execution takes place. checked for syntax error and then converted

to equivalent machine code.

3. Slow for debugging (removal of 3. Good for fast debuggingmistakes from a program)

4. Execution time, is less 4. Execution time is more.

Advantages of High Level LanguagesHigher level languages have a major advantage over machine and assembly languages that higher

level languages are easy to learn and use. It is because that they are similar to the languagesused by us in our day to day life. The following are the main advantages of high-level programminglanguages. These are:


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i. Readability: Programs written in these languages are more readable than assembly andmachine language.ii. Portability: Programs could be run on different machines with little or no change. We can,therefore, exchange software leading to creation of program libraries.iii. Easy debugging: Errors could easily be removed (debugged).iv. Easy Software development: Software could easily be developed. Commands of programminglanguage are similar to natural languages like English

Generation of Programming languages1. The first generation languages or 1GL are low-level languages that are machine language.2. The second generation languages or 2GL are also low-level languages that generally consist of

assembly languages.3. The third generation languages or 3GL are high-level languages such as C.4. The fourth generation languages or 4GL are languages that consist of statements similar to

statements in a human language. Fourth generation languages are commonly used in databaseprogramming and scripts. Ex: SQL

5. The fifth generation languages or 5GL are programming languages that contain visual tools tohelp develop a program. A good example of a fifth generation language is Visual Basic.

Extended study conceptsList of the Different Types of High Level Programming Languages

1) Interpreted Programming LanguagesThe programming languages that are implemented by means of an interpreter are known asinterpreted languages. Interpreters execute the source code directly by translating the sourcecode into a binary representation.

BASIC (Beginner’s All-purpose Symbolic Instruction Code) is a family of high-levelprogramming languages. The original BASIC was designed in 1964, by John George Kemenyand Thomas Eugene Kurtz to provide access for non-science students to computers. BASICremains popular for business applications and in developing tools for banking industry.

Lisp: (List Processing) It is the second-oldest high level computer programming language.Lisp is a general purpose programming language.

Pascal: It is programming language that was intended to use data structuring and structuredprogramming. Niklaus Wirth, a Swiss computer scientist designed this language and

it was named after Blaise Pascal, a French mathematician and philosopher.Perl: Perl is a high level interpreted programming language that supports dynamic

programming and supports writing scriptsPostScript: It is used in the desktop publishing field and is known as a page description

language.Python: It is a high-level programming language that supports writing scripts.

2) Compiled Programming LanguagesThese programming languages make use of a compiler for the execution of code. Compilers cantranslate source code into machine code and thus bring out the implementation of theprogramming language instructions

Ada: It is a statically typed, structured, imperative programming language that is based onPascal and is an internationally standardized computer programming language.

ALGOL: (Algorithmic Language) It proved instrumental in the creation of Programminglanguages like C.

C: Dennis Ritchie at the Bell Telephone Laboratories developed C to be used on the UNIXplatform. It is a general purpose, cross-platform, procedural, imperative programming language.


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It is used for implementing system software and application software and is one of the most-used computer programming languages of today.

C++: It consists of a combination of high-level and low-level language features and is henceconsidered as a middle-level programming language. Bjarne Stroustrup developed C++ as anextension of the C language.

COBOL: The name stands for Common Business-Oriented Language that is designed for thebusiness and finance domain. It is one of the oldest programming languages still in active use

FORTRAN: It is the oldest procedural, imperative, general purpose computerprogramming language that works well for scientific computations and numeric operations.After IBM developed it in the 1950s, it soon gained popularity in programming. It is very popularin the field of high- performance computing and such intensive areas such as climate modeling],numerical weather prediction, finite element analysis, computational fluid dynamics (CFD),computational physics, and computational chemistry. It is one of the most popular languages inthe area of High- performance computing and programs to benchmark and rank the worldsfastest supercomputers are written in Fortran.

Java: Sun Microsystems developed Java. Java applications are compiled to byte code, whichcan run on any virtual machine, thus making Java programs platform-independent. It is verypopular language of the modern times for applications on internet.

Visual Basic: It inherits many of its features from BASIC. Its graphical development featuresmake it easy for beginners to learn VB.

3) Procedural Programming LanguagesProcedural programming is synonymous with imperative programming, which implies specifyingor sequencing the steps that the programs should take to reach to an intended state. Apart fromthe very well-known languages like COBOL, BASIC, FORTRAN, Ada, C, C++, C#, Visual Basicand Java, there are many other languages that follow procedural programming.

RPG :( Report Generator) this programming language is used for business applications4) Scripting Languages

Scripting languages are programming languages that control an application in which they areembedded. Scripts can execute independent of any other application. They are mostly embeddedin the application that they control and are used to add functionality to web pages. Forexample,Dynamic pop ups/Advertisements that appear while browsing a web page are thescripts written in Scripting Languages. Ex: JavaScript, ASP, JSP, PHP, Perl, Tcl

AppleScript: It is a scripting language that is built into the Mac OS.PHP: PHP is one of the very popularly used general purpose scripting languages. It is developed

for creating dynamic web pages and supports a command line interface capability. Tcl: It is a scripting language, which is believed to be easy to learn. It is used for rapid

prototyping and has found utility in embedded systems.VBScript: It is an active scripting language that Microsoft developed as a variation of Microsoft

Visual Basic. VBScript is a default component with each of the Desktop releases of MicrosoftWindows.

Markup Languages:A markup language is an artificial language that uses annotations to text that define how thetext is to be displayed. The language specifies code for formatting, both the layout andstyle, within a text file. The code used to specify the formatting is called tags.

Curl: It is a reflective object-oriented programming language. It is a markup language similarto HTML and also an object-oriented programming language supporting multiple inheritances.

SGML: Standardized General Markup Language.HTML: Hypertext Markup Language, abbreviated as HTML, is the most prominent markup


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language that is used for web pages. It is written in the form of HTML tags that are surroundedby angular brackets. HTML tags describe the appearance of the text in a document and can beembedded into certain other code to affect the web browser behavior.

XML: The name stands for Extensible Markup Language. It is extensible because it allowsthe users to define their own XML elements.

XHTML: It is a markup language that is similar to HTML and follows the XML syntax. It ismidway between HTML and XML. XHTML documents allow automated processing of data.

Logic-based Programming LanguagesLogic programming is the use of mathematical logic for computer programming. Logic-basedprogramming languages specify the attributes for a solution and also the steps to arrive at thesolution.

Prolog: It is a general purpose programming language that supports logic programming andis often linked with artificial intelligence and computational linguistics.

MICROSOFT OFFICE SUITEMicrosoft Office is an office suite of inter-related desktop applications, servers and

services for the Microsoft Windows and Mac OS X operating systems, introduced by Microsoft..Initially it was a bundled set of applications, the first version of Office contained MicrosoftWord, Microsoft Excel, and Microsoft PowerPoint. Additionally, a “Pro” (Professional) versionof Office included Microsoft Access and Schedule Plus. Over the years, Office applicationshave grown substantially closer with shared features such as a common spell checker, OLEdata integration and Microsoft Visual Basic for Applications scripting language. Microsoftalso positions Office as a development platform for line-of-business software under the OfficeBusiness Applications (OBA) brand.

Microsoft WordMicrosoft Word is a word processor and was previously considered to be the main program

in MS Office suit. It has a file extension ‘.DOC’ format is considered a de facto standard for anyword processor. Word 2007 now uses a new Microsoft Office-optimized format called ‘.DOCX’.A word processor more formally known as document preparation system is a computerapplication used for the production including composition, editing, formatting, and possiblyprinting of any sort of printable material.

Microsoft ExcelMicrosoft Excel is a spreadsheet program which originally competed with the dominant

Lotus 1-2-3. A worksheet, a spreadsheet is a data file made up of rows and columns that areused to sort data and allow a user to manipulate and arrange data easily, commonly numericaldata. What makes a spreadsheet software program most unique is its ability to calculatevalues using mathematical formulas and the data in the cells. A good example of how aspreadsheet may be used is creating an overview of a bank’s balance. It is available for theWindows and Mac platforms and now a dominant spread sheet programme.

Microsoft OutlookMicrosoft Outlook is a personal information manager (PIM) from Microsoft available a

part of the Microsoft Office suite. A personal information manager (often referred to as a PIMtool or, more simply, a PIM) is a type of application software that functions as a personalorganizer. The acronym PIM is now, more commonly, used in reference to Personal informationmanagement as a field of study. MS Outlook Although often used mainly as an e-mailapplication, it also includes a calendar, task manager, contact manager, note taking, ajournal and web browsing applications useful foe marketing and management executives intheir daily routine business applications.


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Microsoft PowerPointMicrosoft PowerPoint is a popular presentation program for Windows and Mac. It is

used to create slideshows, composed of text, graphics, movies and other objects, which canbe displayed on-screen through over the head projector or through a computer. It also printsout the presentations on transparencies or slides. This is convenient for school or workpresentations.

Microsoft PublisherMicrosoft Publisher is a program mostly used for designing brochures, labels, calendars,

greeting cards, business cards, newsletters, and postcards.Microsoft Access

Microsoft Access provides an inexpensive yet powerful database solution for small-scale projects. Microsoft Access is used to create simple database solutions. Access tablessupport a variety of standard field types, indices, and referential integrity. Simple tasks canbe automated through macros with point-and-click options. Microsoft Access is very popularamong non-programmers who do not have the knowledge of programming and RDBMSconcepts and yet want to create advanced data base solutions on their own.

Other desktop applications (Windows version only)Microsoft Access — Database managerMicrosoft Info Path — an application to design rich XML-based formsMicrosoft One Note — Note-taking software for use with both tablet and conventional

PCsMicrosoft Project — Project management software to keep track of events and to create

network charts and Gantt charts (not bundled in any Office suite)Microsoft Share Point Workspace (formerly known as Groove) — a proprietary peer-to-

peer collaboration software leveled at businessesMicrosoft Visio — Diagram and flowcharting software (not bundled in any Office suite)Microsoft Office Document Imaging — an application that supports editing scanned

documents.Microsoft Office Document Scanning — a scanning and Optical character

recognition(OCR) application.Microsoft Office InterConnect — business-relationship database available only in JapanMicrosoft Office Picture Manager — basic photo management software (similar to

Google’s Picasa or Adobe’s Photoshop Elements), replaced Microsoft Photo Editor.


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