(R)Introduction of Computer

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Introduction of computer

Let us begin with the word compute. It means to calculate. We all are

familiar with calculations in our day to day life. We apply mathematical

operations like addition, subtraction, multiplication, etc. and many other

formulae for calculations. Simpler calculations take less time. But complex

calculations take much longer time. Another factor is accuracy in calculations.

So man explored with the idea to develop a machine which can perform this

type of arithmetic calculation faster and with full accuracy. This gave birth to a

device or machine called computer.

The computer we see today is quite different from the one made in the

beginning. The number of applications of a computer has increased, the speed

and accuracy of calculation has increased. You must appreciate the impact of

computers in our day to day life. Reservation of tickets in Air Lines and

Railways, payment of telephone and electricity bills, deposits and withdrawals

of money from banks, business data processing, medical diagnosis, weather

forecasting, etc. are some of the areas where computer has becomeextremely useful.

However, there is one limitation of the computer. Human beings do

calculations on their own. But computer is a dumb machine and it has to be

given proper instructions to carry out its calculation. This is why we should

know how a computer works

Computer is an electronic device. As mentioned in the introduction it can do

arithmetic calculations faster. But as you will see later it does much more than

that. It can be compared to a magic box, which serves different purpose to

different people. For a common man computer is simply a calculator, which

works automatic and quite fast. For a person who knows much about it,

computer is a machine capable of solving problems and manipulating data. It

accepts data, processes the data by doing some mathematical and logical

operations and gives us the desired output.

Therefore, we may define computer as a device that transforms data. Data

can be anything like marks obtained by you in various subjects. It can also be

name, age, sex, weight, height, etc. of all the students in your class or income,

savings, investments, etc., of a country. Computer can be defined in terms of

its functions. It can i) accept data ii) store data, iii) process data as desired,

and iv) retrieve the stored data as and when required and v) print the result in

desired format. You will know more about these functions as you go through

the later lessons.

Characteristics of computer

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As we all know computer is an electronic device which stores, reads andprocesses the data or information or produce the meaningful results/output.

Computer is a powerful machine that assists us in our daily life. what makescomputer unique than humans is its specific characteristics, which can beenumerated as Speed, Storage , Accuracy , Ability to operate automatically ,diligence , Scientific approach and versatility.

Speed

A computer is a very high speed data processing machine capable ofoperating at electronic speeds. Most instruction in a computer is carried out inless than a million of a second. Speed of a computer can be specified in termsof number of instructions executed per second.

Storage

One of man's failing is perhaps his inability to remember and "store" largevolumes of information in his brain. The computer is capable of overriding thisdeficiency as it can store.

Accuracy and Reliability

In spite of high speed, the computers are quite accurate and reliable in theircalculations. The accuracy of operation of a computer is always 100%.Computer is only a machine and does not make error on its own. it is thusreliable.

Automatic

Once the process has been initiated, computer is quite capable of functioningautomatically. It does not require a prompt from an operator at each stage ofthe process.

Diligence/Endurance

Man suffers from physical and mental fatigue, lack of concentration andlaziness which do not permit him to carry on his task at the same level ofspeed and accuracy through the entire day. The computer , on the other handis capable of operating at exactly the same level of speed and accuracy evenif it has to carry out the most voluminous and complex operations for a longperiod of time.

Scientific Approach

The entire approach to solving problems is highly scientific, objective andsequentially carried out, leaving no room for emotional and subjectiveevaluations made by man, which are sources of potential error and unjustifiedresults.

Versatility

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Computer is becoming popular, because of its versatility i.e, it can be applied

and used a variety of application; it can be used for general purpose simple

calculations; At the same time the computer can be developed and employed

in a special purpose application.

Decision making:

Computer is capable of taking decision while choosing from many options. It

can compare 2 states of operands; depending upon the results of comparisonit can proceed to initiate actions.

Obedient:

Instructions are carried out obediently without any question or enquiries madeby the computer. Computer is not an intelligent machine but a programmableblack box which has no common sense. Computer simply listen yourinstruction and carry out them obediently without any questions.

The Limitation of Computer

The computer can outperform human beings in speed, memory and accuracybut still the computer has limitations. There are following limitations of acomputer.

Programmed by human:

Though computer is programmed to work efficiently, fast and accurately but it

is programmed by human beings to do so. Without a program, computer is

nothing. A program is a set of instructions. Computer only follows these

instructions. If the instructions are not accurate the working of computer willnot accurate.

Thinking:

The computer can not think itself. The concept of artificial intelligence showsthat the computer can think. But still this concept is dependent on set ofinstructions provided by the human beings.

Self Care:

A Computer can not care itself like a human. A computer is dependent still tohuman beings for this purpose.

Retrieval of memory:

A computer can retrieve data very fast but this technique is linear. A human

being's mind does not follow this rule. A human mind can think randomly

which a computer machine can not.

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Feelings:

One of the main limits in the computer is of feeling. A computer can not feel

about some like a human. A computer can not meet human in respect of

relations. Human can feel, think and caring but a computer machine itself can

not. A computer can not take place of human because computer is always

dependent of human.

The Impact of Computers in Society

Computers are commonly used items in many areas. It is an important thing topeople, especially the people who run organizations, industry, etc. Almostanything you know is run or made by computers. Cars and jets were designedon computers, traffic signals are run by computers, most medical equipmentuse computers and space exploration was started with computers. Most of thejobs today require the use of computers. These 'mechanical brains' made ahuge impact on our society. It would be hard if we didn't have the computeraround.

Let's visualize for a minute. Let's visualize a world without computers. Peoplein the medical field wouldn't have found a lot of cures to diseases, since mostcures were found with the help of computers. Movies like Jurassic Park, ToyStory, A Bug's Life or Godzilla would never have been made without computersbecause they used computer graphics and animation in them. Pharmacieswould have a hard time keeping track with what medications to give topatience. Counting votes would be impossible without computers and mostimportantly, space exploration wouldn't be possible without the help ofcomputers. It's a pretty tough life without computers. Some may not agreeand say, "Well, we don't need computers to live on." They maybe right but

mostly, they are wrong. Computers help in curing diseases, makeentertainment a lot better, keep track of important records, etc. Withoutcomputers, all this wouldn't be possible. The following are the some areaswhere computer are widely used.

Everyone knows that this is the age of computer and vast majority of people

are using computer. Development of science and technology has direct effect

on our daily life as well as in our social life. Computer technology has made

communication possible from one part of the world to the other in seconds.

They can see the transactions in one part of the world while staying in the

other part. Computer development is one of the greatest scientific

achievements of the 20 Th centuries. Computers are used in various fields as

well as in teaching and learning. Some of the major computer application

fields are listed below.

Business or Organization:

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Computers impacted many items in today's society. One area the computerimpacted on is the business area. Business uses computers for keeping trackof accounts, money, or items that they need. You may notice business peopleusing computers a lot, especially the laptop computers, portable computersthat can be taken to your work area. You may see people use things like pie-charts and graphs when they present information to other business people inmeetings. Most of those charts were made by computers. The business fielduses the computers a lot for their companies and organizations.

Entertainment/ Games:

Another area computers impacted on is the entertainment area. Most of thepeople out there like science fiction or action movies, especially the ones withthe neat looking effects. Well, those graphics were mostly made bycomputers. Most of the movies today use computer graphics to make thingsmore realistic but not real. Computer graphics are mostly used on spaceships,aliens, monsters, and special effects. To the left is a picture from the movie"Godzilla." Godzilla was created by computer animation, texturing, andgraphics to make him more realistic then the older version when they used aman in a costume to play Godzilla. This wasn't the only movie made withcomputers. Movies like Jurassic Park, Wing Commander, Starship Troopers,Star Wars SE, and the latest Star Trek Movies used computers to make themlook more interesting and realistic. There are even movies completely madeby computers like Toy Story and A Bugs' Life.

Not only movies used computer animations and graphics. Games on the latestgame consoles like the PC, Play station and Nintendo 64 used the computersto make the coolest games ever. Of course all of you heard of the game FinalFantasy VII. It was the first Final Fantasy game to have a 3D environment andneat computer animation. It was a big money-making seller. Games now anddays use computer graphics and animations to make the coolest games.

Computer games also have their share. Wing Commander Prophecy, Shogoand all the other new 3D games were made by really cool computer graphics.It would be really boring without all this wouldn't you think? That's howcomputers impacted today's entertainment.

Education:

Education was impacted by computers as well. Computers help out students ina lot of today's projects and essays. If a student were to do an essay on theplanet Saturn, they could look in an electronic encyclopedia in the computer orthey could look up their topic on the internet. They could also type their

essays and reports on what's called a word-processing program. This programallows you to type anything out from a school essay to business papers. Youcan make your paper look very neat by adding images and neat looking text toimpress your teacher. Now and days, typing out essays and reports aremandatory, especially in High School. Computers help students in any waythey need, researching, typing, searching, etc. Teachers use computers aswell. They use computers to keep track of grades, type out instruction for theirstudents, and to let students use the computer for school purposes.

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Medical or Hospital:

An important field computers impacted on is the medical field. The computershelped the hospitals out very much. In pharmacies, the pharmacists usecomputers to keep a record of what medication to give to a patient and theamount they need. Most computers in the hospital are used to keep data ofpatience and their status. Computers also keep track of equipment placement

and status as well. Scientists need the help of computers to find cures fordiseases that need cures like cancer and STDs. Without the computers help,cures for a lot of diseases wouldnt have been found. Computer helped themedical area a lot and we are grateful for that since they keep track of ourhealth. Other areas the computer impacted on are space exploration anddesigns of transportation.

Office automation:

Computers are omnipresent in the workplace. Word processorscomputer

software packages that simplify the creation and modification of textual

documentshave largely replaced the typewriter. Electronic mail has made iteasy to transmit textual messages (possibly containing embedded picture and

sound files) worldwide, using computers, cellular telephones, and specially

equipped televisions via telephone, satellite, and cable television networks.

Office automation has become the term for linking workstations, printers,

database systems, and other tools by means of a local area network (LAN). An

eventual goal of office automation has been termed the paperless office.

Although such changes ultimately make office work much more efficient, they

have not been without cost in purchasing and frequently upgrading the

necessary hardware and software and in training workers to use the newtechnology.

Computer-integrated manufacturing (CIM):

CIM is a relatively new technology arising from the application of many

computer science sub disciplines to support the manufacturing enterprise. The

technology of CIM emphasizes that all aspects of manufacturing should be not

only computerized as much as possible but also linked into an integrated

whole via a computer communication network. For example, the design

engineers workstation should be linked into the overall system so that design

specifications and manufacturing instructions may be sent automatically to

the shop floor. The inventory databases should be linked in as well, so product

inventories may be incremented automatically and supply inventories

decremented as manufacturing proceeds. An automated inspection system (or

a manual inspection station supplied with online terminal entry) should be

linked to a quality-control system that maintains a database of quality

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information and alerts the manager if quality is deteriorating and possibly

even provides a diagnosis as to the source of any problems that arise.

Automatically tracking the flow of products from station to station on the

factory floor allows an analysis program to identify bottlenecks and

recommend replacement of faulty equipment. In short, CIM has the potential

to enable manufacturers to build cheaper, higher quality products and thus

improve their competitiveness. Implementing CIM is initially costly, of course,

and progress in carrying out this technology has been slowed not only by itscost but also by the lack of standardized interfaces between the various CIM

components and by the slow acceptance of standardized communication

protocols to support integration. Although the ideal of CIM is perhaps just

beyond reach at the present time, manufacturers are now able to improve

their operations by, for example, linking robot controllers to mainframes for

easy and correct downloading of revised robot instructions. Also available are

elaborate software packages that simplify the building of databases for such

applications as inventories, personnel statistics, and quality control and that

incorporate tools for data analysis and decision support.

Communication:

Making a telephone call no longer should conjure up visions of operators

connecting cables by hand or even of electrical signals causing relays to click

into place and effect connections during dialing. The telephone system now is

just a multilevel computer network with software switches in the network

nodes to route calls to their destinations. The main advantage is that calls get

through much more quickly and reliably than they did in the past. If one nodethrough which a cross-country call would normally be routed is very busy, an

alternative routing can be substituted. A disadvantage is the potential for

dramatic and widespread failures; for example (as has happened), a poorly

designed routing and flow-control protocol can cause calls to cycle indefinitely

among nodes without reaching their destinations until some drastic action is

taken by a system administrator.

Banking

The banking business has been revolutionized by computer technology.

Deposits and withdrawals are instantly logged into a customers account,

which is perhaps stored on a remote computer. Computer-generated monthly

statements are unlikely to contain any errors unless they arise during manual

entry of check amounts. The technology of electronic funds transfer,

supported by computer networking, allows the amount of a grocery bill to be

immediately deducted from the customers bank account and transferred to

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that of the grocery store. Similarly, networking allows individuals to obtain

cash instantly and almost worldwide by simply stepping up to an automated

teller machine (ATM) and providing the proper card and personal identification

number (popularly known as a PIN).

The downside of this technology is the potential for security problems.

Intruders can see packets traveling on a network (e.g., being transported via a

satellite link) and can perhaps interpret them (if not carefully encrypted) to

obtain confidential information on financial transactions. Network access to

personal accounts has the potential to let intruders not only see how much

money an individual has but also to transfer some of it elsewhere.

Business Enterprises:

Computer technology has had a significant impact on retail stores. All but the

smallest shops have replaced the old-fashioned cash register with a terminal

linked to a computer system. Some terminals require that the clerk type in the

code for the item, but most checkout counters include a bar-code scanner, a

device that directly reads into the computer the Universal Product Code (UPC)printed on each package. Cash-register receipts can then include brief

descriptions of the items purchased (by fetching them from the computer

database), and the purchase information is also relayed back to the computer

to cause an immediate adjustment in the inventory data. The inventory

system can easily alert the manager when the supply of some item drops

below a specified threshold. In the case of retail chains linked by networks, the

order for a new supply of an item may be automatically generated and sent

electronically to the supply warehouse. In a less extensively automated

arrangement, the manager can send in the order electronically by a dial-uplink to the suppliers computer. These developments have made shopping

much more convenient. The checkout process is faster, checkout lines are

shorter, and the desired item is more likely to be in stock. In addition, cash-

register receipts contain much more information than a simple list of item

prices; many receipts now include discount coupons based on the specific

items purchased by the shopper. If there is a downside, it is the need for

shoppers to adjust psychologically to not seeing prices on the packages and to

the feeling that perhaps the computer is overcharging (as indeed can happen

when advertised sale prices are somehow not entered into the system).

Since the mid-1990s one of the most rapidly growing retail sectors, known as

electronic commerce, or e-commerce, involves the use of the Internet and

proprietary networks to facilitate business-to-business, consumer, and auction

sales of everything imaginablefrom computers and electronics to books,

recordings, automobiles, and real estate.

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Automotive industry

Computer technology has been incorporated into automobiles. Computers are

involved (as CAD systems) not only in the design of cars but also in the

manufacturing and testing process, perhaps making use of CIM technology.

Todays automobiles include numerous computer chips that analyze sensor

data and alert the driver to actual and potential malfunctions. For example,

the antilock braking system (ABS) is computer controlled. Other computers

provide warnings of actual and potential malfunctions. Automobile

manufacturers are developing safer, smart airbags and remote tire-pressure

monitors. Although increased reliability has been achieved by implementing

such computerization, a drawback is that only automotive repair shops with a

large investment in high-tech interfaces and diagnostic tools for these

computerized systems can handle any but the simplest repairs.

Computers have both positive and negative impact in our daily life as well asin our social life. But the gross development of the nation is faster with theapplication of computers in industries and education. The both positive andnegative impacts of computers are listed below.

Positive Impact of Computer -

The work can be done in very less time.

More information can be stored in small space.

Multitasking and multiprocessing capabilities of data.

Easy to access data.

Impartiality.

Documents can be kept secret.

Error free result.

It can be used for various purposes. i.e. It can be used in any type of work.

Negative Impact of Computer -

Highly expensive.

Accidents.

Data piracy.

Increased Unemployment.

Huge data and information can be lost sometimes.

Fast changing computer technology. Service distribution.

Illiteracy of computing and computers.

As mentioned on the above list, computers have both positive and negativeimpact in our society. But the use of computer is increasing day-by-day.

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HISTORY OF COMPUTER

History of computer could be traced back to the effort of man to count large

numbers. This process of counting of large numbers generated various

systems of numeration like Babylonian system of numeration, Greek system of

numeration, Roman system of numeration and Indian system of numeration.

Out of these the Indian system of numeration has been accepted universally. It

is the basis of modern decimal system of numeration (0, 1, 2, 3, 4, 5, 6, 7, 8,

9). Later you will know how the computer solves all calculations based on

decimal system. But you will be surprised to know that the computer does not

understand the decimal system and uses binary system of numeration for

processing.

We will briefly discuss some of the path-breaking inventions in the field of

computing devices.

Calculating Machines

It took over generations for early man to build mechanical devices for countinglarge numbers. The first calculating device called ABACUS was developed by

the Egyptian and Chinese people.

The word ABACUS means calculating board. It consisted of sticks in horizontal

positions on which were inserted sets of pebbles. It has a number of horizontal

bars each having ten beads. Horizontal bars represent units, tens, hundreds,

etc.

Napiers bones

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

Slide Rule

English mathematician Edmund Gunter developed the slide rule. This machine

could perform operations like addition, subtraction, multiplication, and

division. It was widely used in Europe in 16th century.

Pascal's Adding and Subtract Machine

You might have heard the name of Blaise Pascal. He developed a machine atthe age of 19 that could add and subtract. The machine consisted of wheels,

gears and cylinders.

Leibnizs Multiplication and Dividing Machine

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The German philosopher and mathematician Gottfried Leibniz built around

1673 a mechanical device that could both multiply and divide.

Babbages Analytical Engine

It was in the year 1823 that a famous English man Charles Babbage built a

mechanical machine to do complex mathematical calculations. It was called

difference engine. Later he developed a general-purpose calculating machine

called analytical engine. You should know that Charles Babbage is called thefather of computer.

Mechanical and Electrical Calculator

In the beginning of 19th century the mechanical calculator was developed to

perform all sorts of mathematical calculations. Up to the 1960s it was widely

used. Later the rotating part of mechanical calculator was replaced by electric

motor. So it was called the electrical calculator.

Modern Electronic Calculator

The electronic calculator used in 1960 s was run with electron tubes, which

was quite bulky. Later it was replaced with transistorsand as a result the size

of calculators became too small.

The modern electronic calculator can compute all kinds of mathematical

computations and mathematical functions. It can also be used to store some

data permanently. Some calculators have in-built programs to perform some

complicated calculations.

Fig. 1.3: Vacuum tube, transistor, IC

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Generation of computer

You know that the evolution of computer started from 16th century and

resulted in the form that we see today. The present day computer, however,

has also undergone rapid change during the last fifty years. This period, during

which the evolution of computer took place, can be divided into five distinct

phases known as Generations of Computers. Each generation of computer is

characterized by a major technological development that fundamentallychanged the way computers operate, resulting in increasingly smaller,

cheaper and more powerful and more efficient and reliable devices.

Read about each generation and the developments that led to the current

devices that we use today.

First Generation (1941-1956)

The first generation computers were developed during the period 1946 to

1956. World War gave rise to numerous developments and started off thecomputer age. In first generation computers, the operating instructions or

programs were specifically built for the task for which computer was

manufactured. The Machine language was the only way to tell these machines

to perform the operations. There was great difficulty to program these

computers and more when there were some malfunctions. First Generation

computers used Vacuum tubes and magnetic drum (for data storage).

Followings are the major drawbacks of First generation computers.

1. The operating speed was quite slow.

2. Power consumption was very high.

3. It required large space for installation.

4. The programming capability was quite low.

The characteristics of the first generation computers are:

They used vacuum tubes as their basic components.

They were very large and required a lot of space for installation.

They emitted large amount of heat because they used lots of vacuumtubes. Therefore, power condition was essential.

They were prone to frequent failure and they were unreliable.

Since machine language was used, these computers were difficult to

program and use.

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Second Generation Computers (1956-1963)

The invention of Transistors marked the start of the second generation. These

transistors took place of the vacuum tubes used in the first generation

computers. First large scale machines were made using these technologies to

meet the requirements of atomic energy laboratories. One of the other

benefits to the programming group was that the second generation replaced

Machine language with the assembly language. Even though complex in itselfAssembly language was much easier than the binary code.

Second generation computers also started showing the characteristics of

modern day computers with utilities such as printers, disk storage and

operating systems. Much financial information was processed using these

computers.

In Second Generation computers, the instructions (program) could be stored

inside the computer's memory. High-level languages such as COBOL (Common

Business-Oriented Language) and FORTRAN (Formula Translator) were used,

and they are still used for some applications now days.

The characteristics of the second generation computers are:

Transistors were used in place of vacuum tubes.

They were smaller as compared to the first generation computers.

The generated less heat and less level to failure.

Assembly language was used to program these computers.

They required air conditioning.

Third Generation Computers (1964-1971)

Although transistors were great deal of improvement over the vacuum tubes,

they generated heat and damaged the sensitive areas of the computer. The

Integrated Circuit(IC) was invented in 1958 by Jack Kilby. It combined

electronic components onto a small silicon disc, made from quartz. More

advancement made possible the fittings of even more components on a small

chip or a semi conductor. Also in third generation computers, the operating

systems allowed the machines to run many different applications. These

applications were monitored and coordinated by the computer's memory.

The characteristics of the third generation computers are:

These computers used integrated circuits instead of transistors.

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They were smaller in size and cheaper as compared to the second

generation computers.

They were able to reduce computational time and had low maintenance

cost.

High level languages were developed.

Input/output devices become more sophisticated.

Fourth Generation (1971-1990)

Fourth Generation computers are the modern day computers. The Size started

to go down with the improvement in the integrated circuits. Very Large Scale

(VLSI) and Ultra Large scale (ULSI) ensured that millions of components could

be fit into a small chip. It reduced the size and price of the computers at the

same time increasing power, efficiency and reliability. "The Intel 4004 chip,

developed in 1971, took the integrated circuit one step further by locating all

the components of a computer (central processing unit, memory, and input

and output controls) on a minuscule chip."

Due to the reduction of cost and the availability of the computers power at a

small place allowed everyday user to benefit. First came the minicomputers,

which offered users different applications, most famous of these the word

processors and spreadsheets, which could be used by non-technical users.

In 1981, IBM introduced personal computers for home and office use.

Computer size kept getting reduced during the years. It went down from

Desktop to laptops to Palmtops. Macintosh introduced Graphic User Interface

in which the users didnt' have to type instructions but could use Mouse for thepurpose.

The continued improvement allowed the networking of computers for the

sharing of data. Local Area Networks (LAN) and Wide Area Network (WAN)

were potential benefits, in that they could be implemented in corporations and

everybody could share data over it. Soon the internet and World Wide Web

appeared on the computer scene and fermented the Hi-Tech revolution of

90's.

The characteristics of the fourth generation computers are:

These computers have microprocessor-based system.

They are cheapest among all the computer generation.

A further refinement of input/ output devices took place.

They have large memory and high functional speed.

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Many more high level languages have been introduced such as PASCAL and

C language.

Fifth Generation (1991 onwards)

The computers of 1990s are said to be Fifth Generation computers. The speed

is extremely high in fifth generation computer. Apart from this it can perform

parallel processing. The concept of Artificial intelligence has been introducedto allow the computer to take its own decision. It is still in a developmental

stage.

Fifth generations computers are only in the minds of advance research

scientists and being tested out in the laboratories. These computers will be

under Artificial Intelligence (AI), they will be able to take commands in an

audio visual way and carry out instructions. Many of the operations which

require low human intelligence will be performed by these computers.

Parallel Processing is coming and showing the possibility that the power of

many CPU's can be used side by side, and computers will be more powerful

than those under central processing. Advances in Super Conductor technology

will greatly improve the speed of information traffic. Future looks bright for the

computers.

The characteristics of the fifth generation computers are:

These computers will use super large-scale integrated chips.

They will have artificial intelligence.

They will be able to recognize images and graphs.

They will have the ability to solve the problems using database information

already stored in the computers memory.

They will able to use more than one CPU for faster processing speed.

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CLASSIFICATION OF COMPUTERS

Now let us discuss the varieties of computers that we see today. Although theybelong to the fifth generation they can be divided into different categoriesdepending upon the size, efficiency, memory and number of users. Broadlythey can be divided it to the following categories.

1. On the basis of work principle

2. On the basis of size3. On the basis of Brand4. On the basis of Processing speed (Module )

On the basis of work principle:Computers may be made for different purpose since they have been made fordifferent purpose the computer have different functions. The computer arecategorizing in following ways:

1. Analog computer

2. Digital computer3. Hybrid computer

1. Analog Computer:

Analog computers are the computers that measure physical quantities such aspressure and temperature and convert them to numeric values. They arespecial purpose machines, which perform a particular task and mainly used forscientific and engineering purpose. The main characteristics of thesecomputers are that they are very fast in operation as all the calculations aredone in parallel mode. They give approximate results since they deal with

quantities that vary continuously. The example of analog devices isthermometer, speedometer of car etc. The analog computers are divided intotwo types:

General purpose computer

Specific purpose computer

General purpose computer:

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Classification of computers

On the basis ofworkAnalog ComputerDigital Computer

Hybrid computer

On the basis of sizeSuper ComputerMain frame ComputerMini ComputerMicro Computer

On the basis ofModuleExtended TechnologyAdvance Technology

Personal System 2

On the basis ofBrandIBMIBM CompatibleApple Macintosh


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General-purpose implies programmability and adaptability to differentapplications or the ability to solve many kinds of problems. Most electronicanalog computers were general-purpose systems, either real-time analogcomputers in which the results were obtained without any significant time-scale changes, or high-speed repetitive operation computers.

Specific purpose computer:

Another type of analog computer is the Specific purpose computer, in whichthe relatively slow speeds of sequential digital increment calculations havebeen radically boosted through parallel processing. In this type of analogcomputer it is possible to retain the programming convenience and datastorage of the digital computer while approximating the speed, interactionpotential and parallel computations of the traditional electronic analogs.The Specific purpose computer typically utilizes several specially designedhigh-speed processors for the numerical integration functions, the data (orvariable) memory distributions, the arithmetic functions, and the decision(logic and control) functions. All variables remain as fixed or floating-point

digital data, accessible at all times for computational and operational needs.

2. Digital Computer:

A digital computer is an electronic computing machine that uses the binarydigits (bits) 0 and 1 to represent all forms of information internally in digitalform. Every computer has a set of instructions that define the basic functionsit can perform. Sequences of these instructions constitute machine-languageprograms that can be stored in the computer and used to tailor it to anessentially unlimited number of specialized applications. Calculators are smallcomputers specialized for mathematical computations. General-purpose

computers range from pocket-sized personal digital assistants (notepadcomputers), to medium-sized desktop computers (personal computers andworkstations), to large, powerful computers that are shared by many users viaa computer network. The vast majority of digital computers now in use areinexpensive, special-purpose microcontrollers that are embedded, ofteninvisibly, in such devices as toys, consumer electronic equipment, andautomobiles.

3. Hybrid computers

Hybrid computer is a digital computer that accepts analog signals, convertsthem to digital and processes them in digital form. This integration is obtainedby digital to analog and analog to digital converter. A hybrid computer mayuse or produce analog data or digital data. It accepts a continuously varyinginput, which is then converted into a set of discrete values for digitalprocessing. A hybrid computer system setup offers a cost-effective method ofperforming complex simulations. A hybrid computer capable of real-timesolution has been less expensive than any equivalent digital computer. Hybrid

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computers have been necessary for successful system development. Anexample of a hybrid computer is the computer used in hospitals to measurethe heartbeat of the patient. Hybrid Machines are generally used in scientificapplications or in controlling industrial processes.

On the basis of Size:On the basis of the computer size the computer is categorized into following:

1. Microcomputer2. Mini computer3. Mainframe computer4. Super Computer

1. Microcomputer:

Microcomputer is at the lowest end of the computer range in terms of speedand storage capacity. Its CPU is a microprocessor. It is cheap, compact andcan easily accommodate on a study table. Micro Computers are used as homecomputers for small business as well.

The first microcomputers were built of 8-bit microprocessor chips. The mostcommon application of personal computers (PC) is in this category. The PCsupports a number of input and output devices. An improvement of 8-bit chipis 16-bit and 32-bit chips. Examples of microcomputer are IBM PC, PC-AT, andApple Macintosh. Microcomputers include desktop, laptop and hand-heldmodels.

Desktop:

A desktop computer is the most common micro computer. It is designed to be

used by one person at a time. It typically consists of a system unit, a monitor,a keyboard, internal hard disk storage and other peripheral devices.

Laptop:

A laptop provides mobile computing technology. It is batter-operated andhence can be used anytime and any where. It is small enough to fit on the lapof the user. It is equipped with powerful microprocessors, graphic capabilities,adequate memory and a touch pad.

Han-held Computer:

A hand-held computer is a computer that can conveniently fit on the palm. So,it is also known as a palmtop computer. A stylus, which may contain specialelectronic circuitry, is used to write on the computer display. It has small cardsto store programs and data. It can be connected to printer or a disk drive togenerated output or store data. It has a limited memory and is less powerfulas compare to desktop computer.

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It is also called small mainframe computer. This is designed to support morethan one user at a time. It possesses large storage capacity and operates at ahigher speed. The mini computer is used in multi-user system in which varioususers can work at the same time. This type of computer is generally used forprocessing large volume of data in an organization. They are also used asservers in Local Area Networks (LAN).They are capable of supportingsimultaneous users. High performance workstations with graphics I/O

capability use mini computers. Example of mini computers is IBM 9375 andMotorola 68040.

3. Mainframe Computers:

These types of computers are generally 32-bit microprocessors. They operateat very high speed, have very large storage capacity and can handle the workload of many users. They are generally used in centralized databases. Theyare also used ascontrolling nodes in Wide Area Networks (WAN). It consists ofa high-end computer processor, with related peripheral devices, capable ofsupporting large volumes of data processing, high performance on-line

transaction processing system and extensive data storage and retrieval. It alsoallows its user to maintain large information storage at a centralized locationand can be able to access and process this data from different computerslocated at different locations. They are typical used in large business and forscientific purposes. Example of mainframes are DEC, ICL and IBM 3000 series.

4. Supercomputer:

They are the fastest and most expensive machines. They have high processingspeed compared to other computers. They have also multiprocessingtechnique. One of the ways in which supercomputers are built is by

interconnecting hundreds of microprocessors. They have a large memorycapacity and very high processing speeds for solving scientific andengineering problems. A super computer contains number of CPUs whichoperate in parallel to make it faster. They are used for massive problems.Supercomputers are mainly being used for whether forecasting, biomedicalresearch, remote sensing, aircraft design and other areas of science andtechnology. Examples of supercomputers are CRAY YMP, CRAY2, NEC SX-3,CRAY XMP and PARAM from India.

On the basis of Brand:There are many personal computer manufactures. They give their own names

and model. But actually the computer are classify of the computer brand ofthe computer is categorized into following:

1. IBM PC ( PC- Personal Computer)2. IBM Compatible3. Apple/ Macintosh

1. IBM PC:

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The computers manufactured by IBM (International Business Machine)company are called IBM Computers. The microcomputers of IBM Company arecalled IBM PC. IBM is one of the leading companies in computermanufacturing. These are reliable, strong and high processing speed. IBM hasbeen well known through most of its recent history as the world's largestcomputer company and systems integrator. These are quite expensive thanothers and of original types. IBM manufactures and sells computer hardware

and software (with a focus on the latter), and offers infrastructure services,hosting services, and consulting services in areas ranging from mainframecomputers to nanotechnology. It has been nicknamed "Big Blue" for itsofficial corporate color.

2. IBM Compatible:

Computer developed on the principles of IBM Computers are called IBMCompatible. It can perform all the tasks than an IBM computer does. Suchcomputers used to be referred to as PC clones, or IBM clones since they almostexactly duplicated all the significant features of the PC architecture, facilitated

by various manufacturers' ability to legally reverse engineer the BIOS throughclean room design. Columbia Data Products built the first clone of an IBMpersonal computer through a clean room implementation of its BIOS. Manyearly IBM PC compatibles used the same computer bus as the original PC andAT models. They are less expensive than original (IBM) computers. IBMcomputers are nearly 80% in the world and 95% in Nepal.

3. Apple/ Macintosh:

The computers manufactured by the Apple Company are called AppleComputers. They are specially used in Desktop Designing. These are originals

and quite expensive than IBM and IBM Compatible. The Operating System andother peripherals are completely different than IBM and IBM Compatibles. As achip maker, IBM has been among the Worldwide Top 20 Semiconductor SalesLeaders in past years. Apple is a prominent hardware and software companybest known for its series of personal computers, the iPod and its innovativemarketing strategies for its products.Introduced in 1984, the Macintosh was the first widely sold personal computerwith a graphical user interface (GUI). That feature and others -- such as animproved floppy drive design and a low-cost hard drive that made dataretrieval faster and more reliable -- helped Apple cultivate a reputation forinnovation, which the company still enjoys today.

Extended Technology) the first IBM PC with a hard disk, introduced in 1983. Itused the same 8088 CPU as the original PC but included a whopping 128KB ofRAM and a 10MB hard drive.

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On the basis of Module:The advancement in the technology has enabled us to classify computers onthe basis of model. Let us see how IBM compatible computers are classified onthe basis model:

1. Extended Technology (XT)2. Advanced Technology (AT)3. Personal System-2 (PS/2)

1. Extended Technology (XT):These are the early personal computers. The main processors of thesecomputers are 8080 or 8086 or 8088 which constituted the CPU of thecomputer. The speed of the early XT computers was 4.77 MHz. Thesecomputers have become outmoded.

2. Advanced Technology (AT):AT computers arrived with newer microprocessors such as 80286 SX.But newer computers have 80286 SX or 80386 SX or 80486 SX or80486DX Pentium. These computers are very fast and can even process

faster than early minis. In connection with 80286 and 80386 processor aco-processor is used to supplement the processing of complexmathematical operations. This co-processor is 80287 and 80387respectively. In case of 80486 computers the co-processors are builtinside the main processor. Therefore the most advance computer withlatest microprocessor is being replaced by new processor.

3. Personal System /2 (PS/2):In early 1990, IBM developed another model of computers called PS/2.PS/2 model computes are much faster than IBM compatible computers.It has different architectural design and most of the laptop computers of

IBM Corporation after 1990, are based on PS/2 architecture. This is thelatest model development is Pentium. As its original stage ofdevelopment there was Pentium MMX which evolved into PI, PII andgradually into PIV computers. The PIV processors are the fastestprocessor at present stage where as early Pentium processors were atthe speed of 200 MHz

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COMPUTER ORGANISATION

INTRODUCTION

In the previous lesson we discussed about the evolution of computer. In thislesson we will provide you with an overview of the basic design of a computer.You will know how different parts of a computer are organized and howvarious operations are performed between different parts to do a specific task.

As you know from the previous lesson the internal architecture of computermay differ from system to system, but the basic organization remains thesame for all computer systems.

BASIC COMPUTER OPERATIONS

A computer as shown in Fig performs basically five major operations orfunctions irrespective of their size and make. These are 1) it accepts data orinstructions by way of input, 2) it stores data, 3) it can process data asrequired by the user, 4) it gives results in the form of output, and 5) it controlsall operations inside a computer. We discuss below each of these operations.

Input:

This is the process of entering data and programs in to the computer system.

You should know that computer is an electronic machine like any other

machine which takes as inputs raw data and performs some processing giving

out processed data. Therefore, the input unit takes data from us to the

computer in an organized manner for processing.

Fig

Basic computer Operations

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Storage:

The process of saving data and instructions permanently is known as storage.Data has to be fed into the system before the actual processing starts. It isbecause the processing speed of Central Processing Unit (CPU) is so fast thatthe data has to be provided to CPU with the same speed. Therefore the data isfirst stored in the storage unit for faster access and processing. This storageunit or the primary storage of the computer system is designed to do theabove functionality. It provides space for storing data and instructions.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.

Processing:

The task of performing operations like arithmetic and logical operations iscalled processing. The Central Processing Unit (CPU) takes data andinstructions from the storage unit and makes all sorts of calculations based onthe instructions given and the type of data provided. It is then sent back to thestorage unit.

Output:This is the process of producing results from the data for getting usefulinformation. Similarly the output produced by the computer after processingmust also be kept somewhere inside the computer before being given to youin human readable form. Again the output is also stored inside the computerfor further processing.

Control Unit: The manner how instructions are executed and the aboveoperations are performed. Controlling of all operations like input, processingand output are performed by control unit. It takes care of step by stepprocessing of all operations in side the computer.

FUNCTIONAL UNITS

In order to carry out the operations mentioned in the previous section thecomputer allocates the task between its various functional units. Thecomputer system is divided into three separate units for its operation. Theyare 1) arithmetic logical unit, 2) control unit, and 3) central processing unit.

Arithmetic Logical Unit (ALU)After you enter data through the input device it is stored in the primarystorage unit. The actual processing of the data and instruction are performed

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by Arithmetic Logical Unit. The major operations performed by the ALU areaddition, subtraction, multiplication, division, logic and comparison. Data istransferred to ALU from storage unit when required. After processing theoutput is returned back to storage unit for further processing or getting stored.

Control Unit (CU)

The next component of computer is the Control Unit, which acts like thesupervisor seeing that things are done in proper fashion. The control unitdetermines the sequence in which computer programs and instructions areexecuted. Things like processing of programs stored in the main memory,interpretation of the instructions and issuing of signals for other units of thecomputer to execute them. It also acts as a switch board operator whenseveral users access the computer simultaneously. Thereby it coordinates theactivities of computers peripheral equipment as they perform the input andoutput. Therefore it is the manager of all operations mentioned in the previous

section.

Central Processing Unit (CPU)

The ALU and the CU of a computer system are jointly known as the centralprocessing unit. You may call CPU as the brain of any computer system. It isjust like brain that takes all major decisions, makes all sorts of calculations anddirects different parts of the computer functions by activating and controllingthe operations.

MEMORY SYSTEM IN A COMPUTER

There are two kinds of computer memory: primary and secondary. Primarymemory is accessible directly by the processing unit. RAM is an example ofprimary memory. As soon as the computer is switched off the contents of theprimary memory is lost. You can store and retrieve data much faster withprimary memory compared to secondary memory. Secondary memory such asfloppy disks, magnetic disk, etc., is located outside the computer. Primarymemory is more expensive than secondary memory. Because of this the sizeof primary memory is less than that of secondary memory. We will discussabout secondary memory later on.

Computer memory is used to store two things: i) instructions to execute aprogram and ii) data. When the computer is doing any job, the data that haveto be processed are stored in the primary memory. This data may come froman input device like keyboard or from a secondary storage device like a floppydisk.

As program or the set of instructions is kept in primary memory, the computeris able to follow instantly the set of instructions. For example, when you book

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ticket from railway reservation counter, the computer has to follow the samesteps: take the request, check the availability of seats, calculate fare and waitfor money to be paid, store the reservation and get the ticket printed out. Theprogramme containing these steps is kept in memory of the computer and isfollowed for each request.

But inside the computer, the steps followed are quite different from what wesee on the monitor or screen. In computers memory both programs and dataare stored in the binary form. You have already been introduced with decimalnumber system that is the numbers 1 to 9 and 0. The binary system has onlytwo values 0 and 1. These are called bits. As human beings we all understanddecimal system but the computer can only understand binary system. It isbecause a large number of integrated circuits inside the computer can beconsidered as switches, which can be made ON, or OFF. If a switch is ON it isconsidered 1 and if it is OFF it is 0. A number of switches in different states willgive you a message like this: 110101....10. So the computer takes input in theform of 0 and 1 and gives output in the form 0 and 1 only. Is it not absurd if

the computer gives outputs as 0s & 1s only? But you do not have to worryabout. Every number in binary system can be converted to decimal systemand vice versa; for example, 1010 meaning decimal 10. Therefore it is thecomputer that takes information or data in decimal form from you, convert itin to binary form, process it producing output in binary form and again convertthe output to decimal form.The primary memory as you know in the computer is in the form of ICs(Integrated Circuits). These circuits are called Random Access Memory (RAM).Each of RAMs locations stores one byte of information. (One byte is equal to 8bits). A bit is an acronym for binary digit, which stands for one binary piece of

information. This can be either 0 or 1. You will know more about RAM later.The Primary or internal storage section is made up of several small storagelocations (ICs) called cells. Each of these cells can store a fixed number of bitscalled word length.

Each cell has a unique number assigned to it called the address of the cell andit is used to identify the cells. The address starts at 0 and goes up to (N-1).You should know that the memory is like a large cabinet containing as manydrawers as there are addresses on memory. Each drawer contains a word andthe address is written on outside of the drawer.

Capacity of Primary Memory

You know that each cell of memory contains one character or 1 byte of data. So thecapacity is defined in terms of byte or words. Thus 64 kilobyte (KB) memory iscapable of storing 64 1024 = 32,768 bytes. (1 kilobyte is 1024 bytes). A memory sizeranges from few kilobytes in small systems to several thousand kilobytes in largemainframe and super computer. In your personal computer you will find memorycapacity in the range of 64 KB, 4 MB, 8 MB and even 16 MB (MB = Million bytes).

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The following terms related to memory of a computer are discussed below:

Random Access Memory (RAM):

The primary storage is referred to as random access memory (RAM) because it ispossible to randomly select and use any location of the memory directly store and

retrieve data. It takes same time to any address of the memory as the first address. Itis also called read/write memory. The storage of data and instructions inside theprimary storage is temporary. It disappears from RAM as soon as the power to thecomputer is switched off. The memories, which loose their content on failure of powersupply, are known as volatile memories .So now we can say that RAM is volatilememory.

Read Only Memory (ROM):

There is another memory in computer, which is called Read Only Memory (ROM).Again it is the ICs inside the PC that form the ROM. The storage of program and datain the ROM is permanent. The ROM stores some standard processing programs

supplied by the manufacturers to operate the personal computer. The ROM can onlybe read by the CPU but it cannot be changed. The basic input/output program isstored in the ROM that examines and initializes various equipment attached to the PCwhen the switch to made ON. The memories, which do not loose their content onfailure of power supply, are known as non-volatile memories. ROM is non-volatilememory. There are various types of ROM

PROM:There is another type of primary memory in computer, which is called ProgrammableRead Only Memory (PROM). You know that it is not possible to modify or eraseprograms stored in ROM, but it is possible for you to store your program in PROMchip. Once the program are written it cannot be changed and remain intact even ifpower is switched off. Therefore programs or instructions written in PROM or ROMcannot be erased or changed.

EPROM:This stands for Erasable Programmable Read Only Memory, which over come theproblem of PROM & ROM. EPROM chip can be programmed time and again by erasingthe information stored earlier in it. Information stored in EPROM exposing the chip forsome time ultraviolet light and it erases chip is reprogrammed using a specialprogramming facility. When the EPROM is in use information can only be read.

Cache Memory:

The speed of CPU is extremely high compared to the access time of main memory.Therefore the performance of CPU decreases due to the slow speed of main memory.To decrease the mismatch in operating speed, a small memory chip is attachedbetween CPU and Main memory whose access time is very close to the processingspeed of CPU. It is called CACHE memory. CACHE memories are accessed much fasterthan conventional RAM. It is used to store programs or data currently being executedor temporary data frequently used by the CPU. So each memory makes main memory

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Fig Magnetic Tape

Advantages of Magnetic Tape:

Compact: A 10-inch diameter reel of tape is 2400 feet long and is able to hold800, 1600 or 6250 characters in each inch of its length. The maximumcapacity of such tape is 180 million characters. Thus data are stored muchmore compactly on tape.

Economical: The cost of storing characters is very less as compared to otherstorage devices.

Fast: Copying of data is easier and fast.

Long term Storage and Re-usability: Magnetic tapes can be used for longterm storage and a tape can be used repeatedly with out loss of data.

Magnetic Disk:

You might have seen the gramophone record, which is circular like a disk andcoated with magnetic material. Magnetic disks used in computer are made onthe same principle. It rotates with very high speed inside the computer drive.Data is stored on both the surface of the disk. Magnetic disks are most popularfor direct accessstorage device. Each disk consists of a number of invisibleconcentric circles called tracks. Information is recorded on tracks of a disk

surface in the form of tiny magnetic spots. The presence of a magnetic spotrepresents one bitand its absence represents zero bit. The information storedin a disk can be read many times without affecting the stored data. So thereading operation is non-destructive. But if you want to write a new data, thenthe existing data is erased from the disk and new data is recorded.

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Floppy Disk:

It is similar to magnetic disk discussed above. They are 5.25 inch or 3.5 inch indiameter. They come in single or double density and recorded on one or bothsurface of the diskette. The capacity of a 5.25-inch floppy is 1.2 mega bytes

whereas for 3.5 inch floppy it is 1.44 mega bytes. It is cheaper than any otherstorage devices and is portable. The floppy is a low cost device particularlysuitable for personal computer system.

Optical Disk:

With every new application and software there is greater demand for memorycapacity. It is the necessity to store large volume of data that has led to thedevelopment of optical disk storage medium. Optical disks can be divided intothe following categories:

Compact Disk/ Read Only Memory (CD-ROM): CD-ROM disks are made ofreflective metals. CD-ROM is written during the process of manufacturing byhigh power laser beam. Here the storage density is very high, storage cost isvery low and access time is relatively fast. Each disk is approximately 4 1/2inches in diameter and can hold over 600 MB of data. As the CD-ROM can beread onlywe cannot write or make changes into the data contained in it.

Write Once, Read Many (WORM): The inconvenience that we can not write anything in to a CD-ROM is avoided in WORM. A WORM allows the user to writedata permanently on to the disk. Once the data is written it can never beerased without physically damaging the disk. Here data can be recorded from

keyboard, video scanner, OCR equipment and other devices. The advantage ofWORM is that it can store vast amount of data amounting to gigabytes (109bytes). Any document in a WORM can be accessed very fast, say less than 30seconds.

Erasable Optical Disk: These are optical disks where data can be written,erased and re-written. This also applies a laser beam to write and re-write thedata. These disks may be used as alternatives to traditional disks. Erasableoptical disks are based on a technology known as magnetic optical (MO). Towrite a data bit on to the erasable optical disk the MO drive's laser beam heatsa tiny, precisely defined point on the disk's surface and magnetizes it.

INPUT OUTPUT DEVICES

A computer is only useful when it is able to communicate with the externalenvironment. When you work with the computer you feed your data andinstructions through some devices to the computer. These devices are calledInput devices. Similarly computer after processing gives output through otherdevices called output devices.

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For a particular application one form of device is more desirable compared toothers. We will discuss various types of I/O devices that are used for differenttypes of applications. They are also known as peripheral devices because theysurround the CPU and make a communication between computer and theouter world.

Input Devices:

Input devices are necessary to convert our information or data in to a formwhich can be understood by the computer. A good input device should providetimely, accurate and useful data to the main memory of the computer forprocessing followings are the most useful input devices.

Keyboard:

This is the standard input device attached to all computers. The layout of

keyboard is just like the traditional typewriter of the type QWERTY. It alsocontains some extra command keys and function keys. It contains a total of101 to 104 keys. You have to press correct combination of keys to input data.The computer can recognize the electrical signals corresponding to the correctkey combination and processing is done accordingly.

Mouse:

Mouse is an input device shown in Fig. 2.7 that is used with your personalcomputer. It rolls on a small ball and has two or three buttons on the top.When you roll the mouse across a flat surface the screen censors the mouse in

the direction of mouse movement. The cursor moves very fast with mousegiving you more freedom to work in any direction. It is easier and faster tomove through a mouse.

Scanner:

The keyboard can input only text through keys provided in it. If we want toinput a picture the keyboard cannot do that. Scanner is an optical device thatcan input any graphical matter and display it back. The common opticalscanner devices are Magnetic Ink Character Recognition (MICR), Optical MarkReader (OMR) and Optical Character Reader (OCR).

Magnetic Ink Character Recognition (MICR):

This is widely used by banks to process large volumes of cheques and drafts.Cheques are put inside the MICR. As they enter the reading unit the chequespass through the magnetic field which causes the read head to recognize thecharacter of the cheques.

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Optical Mark Reader (OMR):

This technique is used when students have appeared in objective type testsand they had to mark their answer by darkening a square or circular space bypencil. These answer sheets are directly fed to a computer for grading where

OMR is used.

Optical Character Recognition (OCR):

This technique unites the direct reading of any printed character. Suppose youhave a set of hand written characters on a piece of paper. You put it inside thescanner of the computer. This pattern is compared with a site of patternsstored inside the computer. Whichever pattern is matched is called acharacter read. Patterns that cannot be identified are rejected. OCRs areexpensive though better the MICR.

Output Devices

Visual Display Unit:The most popular input/output device is the Visual Display Unit (VDU). It is alsocalled the monitor. A Keyboard is used to input data and Monitor is used todisplay the input data and to receive massages from the computer. A monitorhas its own box which is separated from the main computer system and isconnected to the computer by cable. In some systems it is compact with thesystem unit. It can be coloror monochrome.

Terminals:

It is a very popular interactive input-output unit. It can be divided into twotypes: hard copy terminals and soft copy terminals. A hard copy terminalprovides a printout on paper whereas soft copy terminals provide visual copyon monitor. A terminal when connected to a CPU sends instructions directly tothe computer. Terminals are also classified as dumb terminals or intelligentterminals depending upon the work situation.

Printer:It is an important output device which can be used to get a printed copy of

the processed text or result on paper. There are different types of printers thatare designed for different types of applications. Depending on their speed and

approach of printing, printers are classified as impactand non-impactprinters.Impact printers use the familiar typewriter approach of hammering a typefaceagainst the paper and inked ribbon. Dot-matrix printers are of this type. Non-impact printers do not hit or impact a ribbon to print. They use electro-staticchemicals and ink-jet technologies. Laser printers and Ink-jet printers are ofthis type. This type of printers can produce color printing and elaborategraphics.

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LANGUAGE/SOFTWARE

INTRODUCTION

In the previous lesson we discussed about the different parts and configurations of

computer. It has been mentioned that programs or instructions have to be fed to the

computer to do specific task. So it is necessary to provide sequence of instructions so

that your work can be done. We can divide the computer components into two major

areas, namely, hardware and software. Hardware is the machine itself and its various

individual equipment. It includes all mechanical, electronic and magnetic devices

such as monitor, printer, electronic circuit, floppy and hard disk. In this lesson we will

discuss about the other part, namely, software.

WHAT IS SOFTWARE?

As you know computer cannot do anything without instructions from the user. In

order to do any specific job you have to give a sequence of instructions to the

computer. This set of instructions is called a computer program. Software refers tothe set of computer programs, procedures that describe the programs, how they are

to be used. We can say that it is the collection of programs, which increase the

capabilities of the hardware. Software guides the computer at every step where to

start and stop during a particular job. The process of software development is called

programming.

You should keep in mind that software and hardware are complementary to each

other. Both have to work together to produce meaningful result. Another important

point you should know that producing software is difficult and expensive.

SOFTWARE TYPES

Computer software is normally classified into two broad categories.

Application Software

System software

Application Software: Application Software is a set of programs to carry out

operations for a specific application. For example, payroll is application software for

an organization to produce pay slips as an output. Application software is useful for

word processing, billing system, accounting, producing statistical report, analysis of

numerous data in research, weather forecasting, etc. In later modules you will learn

about MS WORD, Lotus 1-2-3 and dBASE III Plus. All these are application software.

Another example of application software is programming language. Among the

programming languages COBOL (Common Business Oriented Language) is more

suitable for business application whereas FORTRAN (Formula Translation) is useful for

scientific application. We will discuss about languages in next section.

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System Software: You know that an instruction is a set of programs that has to be

fed to the computer for operation of computer system as a whole. When you switch

on the computer the programs written in ROM is executed which activates different

units of your computer and makes it ready for you to work on it. This set of program

can be called system software. Therefore system software may be defined as a set of

one or more programs designed to control the operation of computer system.

System software are general programs designed for performing tasks such as

controlling all operations required to move data into and out of the computer. It

communicates with printers, card reader, disk; tapes etc. monitor the use of various

hardware like memory, CPU etc. Also system software is essential for the

development of applications software. System Software allows application packages

to be run on the computer with less time and effort. Remember that it is not possible

to run application software without system software.

Development of system software is a complex task and it requires extensive

knowledge of computer technology. Due to its complexity it is not developed inhouse. Computer manufactures build and supply this system software with the

computer system. DOS, UNIX and WINDOWS are some of the widely used system

software. Out of these UNIX is a multi-user operating system whereas DOS and

WINDOWS are PC-based. We will discuss in detail about DOS and WINDOWS in the

next module.

So without system software it is impossible to operate your computer. The following

picture is shown in Fig. 3.1 relation between hardware, software and you as a user of

computer system.

WHAT IS LANGUAGE?

You are aware with the term language. It is a system of communication between you

and me. Some of the basic natural languages that we are familiar with are English,

Hindi, Oriya etc. These are the languages used to communicate among various

categories of persons. But how you will communicate with your computer. Your

computer will not understand any of these natural languages for transfer of data and

instruction. So there are programming languages specially developed so that you

could pass your data and instructions to the computer to do specific job. You must

have heard names like FORTRAN, BASIC, COBOL etc. These are programming

languages. So instructions or programs are written in a particular language based on

the type of job. As an example, for scientific application FORTRAN and C languagesare used. On the other hand COBOL is used for business applications.

Programming Languages

There are two major types of programming languages. These are Low Level

Languages and High Level Languages. Low Level languages are further divided in to

Machine language and Assembly language.

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Low Level Languages

The term low level means closeness to the way in which the machine has been built.

Low level languages are machine oriented and require extensive knowledge of

computer hardware and its configuration.

Machine Language

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

It does not needs any translator program. We also call it machine code and it is

written as strings of 1's (one) and 0s (zero). When this sequence of codes is fed to

the computer, it recognizes the codes and converts it in to electrical signals needed

to run it. For example, a program instruction may look like this:

1011000111101

It is not an easy language for you to learn because of its difficult to understand. It is

efficient for the computer but very inefficient for programmers. It is considered to thefirst generation language. It is also difficult to debug the program written in this

language.

Advantage

The only advantage is that program of machine language run very fast because no

translation program is required for the CPU.

Disadvantages

1. It is very difficult to program in machine language. The programmer has to know

details of hardware to write program.

2. The programmer has to remember a lot of codes to write a program which results

in program errors.

3. It is difficult to debug the program.

(b) Assembly Language

It is the first step to improve the programming structure. You should know that

computer can handle numbers and letter. Therefore some combination of letters can

be used to substitute for number of machine codes.The set of symbols and letters forms the Assembly Language and a translator

program is required to translate the Assembly Language to machine language. This

translator program is called `Assembler'. It is considered to be a second-generation

language.

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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.

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 machine language 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.

HIGH LEVEL LANGUAGES

You know that assembly language and machine level language require deep

knowledge of computer hardware where as in higher language you have to know only

the instructions in English words and logic of the problem irrespective of the type of

computer you are using.

Higher level languages are simple languages that use English and mathematical

symbols like +, -, %, / etc. for its program construction.

You should know that any higher level language has to be converted to machine

language for the computer to understand.

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

suitable for solving a particular problem. For example COBOL (Common Business

Oriented Language) is mostly suitable for business oriented language where there is

very little processing and huge output. There are mathematical oriented languages

like FORTRAN (Formula Translation) and BASIC (Beginners All-purpose Symbolic

Instruction Code) where very large processing is required.

Thus a problem oriented language designed in such a way that its instruction may be

written more like the language of the problem. For example, businessmen use

business term and scientists use scientific terms in their respective languages.

Advantages of High Level Languages

Higher level languages have a major advantage over machine and assembly

languages that higher level languages are easy to learn and use. It is because that

they are similar to the languages used by us in our day to day life.

Compiler

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It is a program translator that translates the instruction of a higher level language to

machine language. It is called compiler because it compiles machine language

instructions for every program instructions of higher level language. Thus compiler is

a program translator like assembler but more sophisticated. It scans the entire

program first and then translates it into machine code.

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.

Higher Level Language --> (Compile) ---> Program --> Machine Language 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 compile source code written in COBOL language.

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

compiled for one type of machine will not run in another type. Therefore every type ofmachine must have its personal compiler for a particular language. Machine

independence is achieved by using one higher level language in different machines.

Interpreter

An interpreter is another type of program translator used for translating higher level

language into machine language. It takes one statement of higher level languages,

translate it into machine language and immediately execute it. Translation and

execution are carried out for each statement. It differs from compiler, which translate

the entire source program into machine code and does involve in its execution.

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 executed then it is first translated.

Thus compiled machine language program runs much faster than an interpreted

program.

Operating Systems

An operating system is a complex set of software modules that manages the overalloperations of a computer. It is a master control program that acts as a manager, ahousekeeper and a traffic cop for the computer system. Depending on the type ofcomputer the operating system performs a number of functions, such as allocatingresources, tracking the use of different computer resources, ensuring optimalutilization of various resources, and acting as an interface between the user and the

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computer. Application programs, such as word processors and spreadsheets, rununder the supervision of the operating system.

An operating system loads programs, performs and manages input/output operations,manages files, monitors and manages the use of computer memory, allocatesresources for various computer functions and resolve conflicts.

The operating system loads programs to be executed into primary memory and sendsa message to the user when the execution is completed. It also notifies the user ofany errors in the system or error that it encounters during program executions.

An operating system is to manage files, a file is a place in computer memory wheredata and instructions are stored. The computer reads creates, deletes, merges andrenames files and performs other related tasks with help from the operating system.

There are two types of operating system environments and a brief description ofeach.

Multiprogramming: Multiple users can run multiple programs on a single CPUcomputer at same time. The CPU switches between programs, however at any giventime it is executing only one program.

Multiprocessing: A multiprocessing system has a number of processors that processdata and instructions, unlike systems that have only one CPU. Ideally suited forcomplex and computationally intensive operations that require processing.

Types of Operating system:

Within the board family of operating systems, there are generally different categories

based on the types of computers they control and the sort of applications theysupports. The categories are:

Single-user, single task: It is an operating system is designed to manage thecomputer so that one user cann effectively do one thing at a time. The Palm OS forPalm handheled computer is a good example of modern single-user, single-taskoperating system.

Single-user, multi tasking: It is an operating system support execution of morethan one job at a time on a computer. Microsoft's Windows and Apple's MacOSplatforms are the examples of single-user, multi-tasking operating system.

Multi-User: It is an operating system allows many different users to take advantageof the computer's resources simultaneously. The operating system must make surethat the requirements of the various users are balanced and that each of theprograms they are using has sufficient and separate resources so that a problem withone user doesn't affect the entire community of users. Unix and MVS are example ofmulti-user operating system.

Utility Program:

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Utility Programs are among the most popular types of system support software. Itperforms routine tasks, such as formatting disks, copying files from a disk, sortingfiles and editing files, as well as other important housekeeping functions. Manyoperating system have utility programs built directly into the operating system itself.

Application Software:

Application software is designed to perform people-related tasks such as payroll,

inventory and sales analysis. There are two types of applications, such as payroll and

so on and dedicated software (designed for specific application, such as the space

shuttle).

Application software can manipulate text, numbers, graphics or a combination of

these depending on the work for which it was designed. Applications software thus

includes word processors, spreadsheets, database management, inventory and

payroll programs and many other applications. Application software may be written

by a large software house which distributes its products widely and addresses a

general class of problems or may be written by an individual and address a particular

problem. There are two types of applications software:

Customized or Tailored software

Package software

Customized or Tailored software:

Customized or Tailored software is the software designed to meet the specific

requirements of an organization or individual. Tailored software is written on demand

of the individual's need and serve only singled organization. It is written in high levellanguages such as Visual basic and Visual C++. Some of the example of tailored

software are payroll package, inventory package and library information system.

Package software:

Package software is generalized set of programs that allow the computer to perform a

specific data processing job for the user. These programs are user friendly and

designed for use in more than one envir