Chapter 31: COMPUTER-OPERATION AND NETWORKING

Chapter Outline:

• Introduction
• What are Computers?
• Classification of Computers
• General Structure and Working
• Language of a Computer
• Components of a Personal Computer
• How does a personal computer machine operate?
• What is a Computer Network?
• Computer Virus
• Summary
• Reference and Suggested Readings

I.                    Introduction

             Thanks to the fascinating world of computers. Today, computers have become the part of our lives. Every field and activity our life is now affected and benefited by the application of computers and computer technology. Education is not an exception. Today, the teaching and learning is making use of computers in so many forms and ways. The learner or teacher is in a need of some working knowledge of the use of computers. This chapter will provide a necessary background for understanding the concept, structure and functioning of computers in the manner we often make use of them in our school`s computer lab.

                    

II.                  What are Computers?

            For tracing the evolution of computers, we will have to go back to the age of discovery of numbers and counting systems. Counting with the aid of pebbles was perhaps the first calculating technique used by the human beings. However, the credit for being called as the first computer goes to ABACUS.
To know the Evolution of Computer, click this Link.

·         ABACUS -a counting machine used by Ancient Orientals.

-          Is more than 5000 years old and is still the primary form of “number crunching” in many parts of the world.

The next attempt after the invention of the ABACUS, for automatic computation, was made by a French scientist Blasé Pascal in 1642. He invented an arithmetic machine actually for the purpose of helping his father in his business of tax collection. This machine had eight wheels, each wheel having the numbers 0 to 9 painted on it. The wheels were attached to gears. The gear, in turn, was attached to each other in such a way that simple addition and subtraction could take place by dialing the amounts to be added or subtracted. Pascal`s machine was, in fact, the first calculator and non-portable computer of the world. The computer world has acknowledged his contributions by naming a computer programming language as ‘Pascal’.

                In view of the above-mentioned historical evolution and also on its literal meaning, the term “computer” stands for a device helpful in computing or calculating at a faster speed with great possible accuracy. However, as we know about the modern computers, their field is not limited to computation. They handle any type of information or data and work in almost all the fields of human endeavor. Therefore, to define them merely as a device helpful in computation is not justified. In search of some alternative definition, we can safely consider a computer as a thinking machine of the human being that makes use of use some well-framed meaningful programmes (software) for its operation and utilities. Therefore, as a programmable machine, every computer is known to possess the following two characteristics:

1.       Responding to a specific set of instructions, in a well defined way.

2.       Executing a pre-recorded list of instructions (a programme) for performing various tasks.

III.                Classification of Computers

A.      MICROCOMPUTERS

-          Are low-cost small-size computers.

-          Have been so named on account of their employing micro-processors.

-          Represents typically single-user systems, meaning that a microcomputer can be used by only one user at a time.

B.      MINICOMPUTERS

-          Performs better, are larger in size, and cost more than microcomputers.

-          Also possess larger storage capacities and are faster.

-          Are designed to support more than one user at a time. That is why these may also be used as servers in local area network (LAN).

-          Can support ten to hundreds of users simultaneously.

C.      MAINFRAMES

-          These are computers that are more powerful and faster than minicomputers.

-          Have a quite larger storage capacity and are able to support many hundreds of users simultaneously.

-          Their real values lie in their processing power to handle large database systems.

D.      SUPER COMPUTERS

-          Are the most powerful, fastest and expensive machine.

-          Can be afforded only by rare organizations working on the national level.

-          Have remarkable performance as billions of calculations may be performed by them in a second.

-          Some of the areas in which these are in use are sophisticated scientific and biomedical researches, weather forecasting, designing of sophisticated machines and warfare equipment, etc.

IV.                General Structure and Working

The structure and working of a computer resembles the human brain. In general, a computer system consists of the subsystems, namely:

1.       INPUT- subsystem in the form of keyboard ,cassette recorder, etc. works for putting outside information in the machine just as our eyes, ears and other sense organs work for our brain to collect information from the environment.

2.       MEMORY- a subsystem that helps in storing information and data electronically which can be retained indefinitely and used when needed. However, this memory is erasable and hence the stored information can be replaced with the new one within a few microseconds.

3.       ARITHMETIC AND LOGIC- is the arithmetic and logic mind of the computer. It is responsible for all types of data manipulation and computation work.

4.       OUTPUT- resembles the output system of our brain to furnish the answered information. Whereas in our case it is done orally and by writing, in computers it is carried out through display (visualized) in the screen of the monitor, the printer(in the form of printed material) or the cassette recorder(voice).

5.       CONTROL- controls the execution of the programme and coordinates all the activities of the computer. It functions in two phases in a cyclic manner:

a.       Instruction phase

b.      Execution phase

The arithmetic and logic and the control subsystems together is called the CENTRAL PROCESSING UNIT (CPU) or simply the processor signifying that what is to be processed in the machine is done through CPU.

V.                  Language of a Computer

The computer language serves much the same purpose as human language, i.e. communication. But they can’t communicate in the languages of ours. They have their own languages such as BASIC, PILOT, LOGO, FORTRAN, COBOL and JAVA, etc. If we wish to communicate with them, we have to know their languages. Each of these languages tries to adopt a particular type of number system- BINARY, HEXADECIMAL or OCTAL SYSTEM, etc. - in place of the usual decimal system adopted by the human beings for the general computation work. Most of the computers make use of the binary system with two-digit symbols, 0 and 1 (instead of ten digits, 0 and 1 to 9) for expressing any number as illustrated in Table 31.1.

NUMBER	EXPRESSED IN COMPUTER LANGUAGE
0	0000
1	0001
2	0010
3	0011
4	0100
5	0101
6	0110
7	0111
8	1000

For expressing in computer language, the alphabet, operations, etc. are first given specified code number as given in Table 31.2 and then transformed into computer`s language.

INSTRUCTION	OPERATION CODE NO.	EXPRESSED IN COMPUTER LANGUAGE
ADD	1	001
SUBTRACT	2	0010
MULTIPLY	3	0011
DIVIDE	4	0100
READ A CARD	5	0101
SQUARE	6	0110
DRAW A LINE	7	0111
TRANSFORM	8	1000

VI.                Components of a Personal Computer (PC)

Your PC has a machine-like body and components (referred to as hardware) and a set of instructions (called programmes or software) for its operation and use.

A.      INPUT DEVICES UNIT

-          Are those devices or equipment meant for feeding data and instructions into the memory of the computer?

·         KEYBOARD

-          Closely resembles a typewriter.

-          Has a set of keys for enabling you to enter data into the computer.

-          Has 101 keys containing letters, numbers and symbols, like an ordinary typewriter. Besides these, it contains a variety of other keys:

1.       FUNCTION KEYS - are 12 keys found on the top left-hand side of the keyboard and are named F1, F2, and F12.

   - are used to perform special functions depending on the software used.

2.       NUMERIC KEYBOARD - is located on the right-hand side of the keyboard.

             - Looks and functions like a calculator.

3.       SPECIAL KEYS – are meant to perform special functions like controlling the movement of the cursor on the computer screen.

While working on your PC using a keyboard, you must have noticed a flashing point on the computer screen (monitor). It is the cursor. For the movement of the cursor, the keyboard has the following special keys:

·         Four directional arrow keys for moving the cursor one space at a time either up, down, left or right direction.

·         The keys such as HOME, END, PAGE UP and PAGE DOWN for moving the cursor quickly over longer distances. The page up and page down keys are in fact used to “Scroll Up”  and “Scroll Down” the page length of the screen.

The other special keys (besides the cursor movement keys) on your keyboard are identified in Table 31.3.

TABLE 31.3 Special keys on the Keyboard

SPECIAL KEY	FUNCTIONS
DEL	Delete characters
INS	Inserts characters
ESC	Stand for ESCAPE, is used generally for cancelling a command.
BACKSPACE	Erases the character to the left of the cursor.
CTRL AND ALT	Control key and alternate keys. They have no function alone. They are able to input special messages to the computer when passed with other keys.
ENTER	Executes an instruction or data being keyed in through the keyboard.
CAPS LOCK	Used for keying in capitalized alphabets.
SHIFT	Behaves differently when the Caps Lock key is off or on.
CAPS LOCK OFF	If pressed simultaneously with a character key, it can input a capitalized alphabet.
CAPS LOCK ON	It reverses the above effect.

·         MOUSE

   – an alternative device to the keyboard for controlling the movement of the cursor or pointer on the computer screen.

-          Looks somewhat like a mouse with tail (in the form of its connecting wire) hence the name.

-          The mouse may have one, two or three buttons.

-          The function of each button is determined by the programme that uses the mouse.

·         LIGHT PEN

     – is a pen-like pointing device used to select an option by simply pointing at it, or to draw figures and graphics directly on the computer screen.

·         SCANNER – many times you face the situation when some information (text or picture) is available on paper and you need it on computer disk for further editing or incorporating it in your prepared document.

-          The solution may be taking a photograph of the image directly from the available source, getting it converted into a form for being saved on the disk and then finally having its print through the printer.

-          That you will mostly find in your computer labs are of two types:

a.       FLAT-BED SCANNER

b.      HAND-HELD SCANNER

The scanners as input devices are advantageous on many fonts. They may be used:

a.       To produce photographs on the computer screen.

b.      As a photocopier for scanning text and graphics.

c.       To integrate text and graphic files.

d.      In so many educational, official and business purposes such as desktop publishing, storage of documents on the computer, demonstration and instructional aids in the classroom teaching, seminar and training programmes.

·         DIGITAL CAMERA

 – is used as an input device for feeding images into computer. We can take still photographs with the help of it. Such photographs after being stored in the camera are sent as digital input into the computer.

B.      OUTPUT DEVICES UNIT

-          Refers to any information or result coming out of a computer.

-          May be considered as those devices that help in providing information or results to the users by getting the same from the computer.

·         MONITOR

– is also known as visual display unit (VDU).

-          The out coming information or results (after being processed by the computer) are displayed in a visual form on the screen of the monitor.

·         DOT-MATRIX PRINTERS

– it prints the individual character in the form of dots by striking pins against an ink ribbon.

-          The number of pins in the print head may vary from 9 to 24.

-          These printers are not much favored in comparison to ink-jet and laser printers on account of the following reasons:

a.       These make much noise.

b.      Their speed of printing is quite low.

c.       Their print quality is very inferior in comparison to other printers.

·         INK-JET PRINTERS

 – use jet ink to print fully formed (not dots) characters on the paper.

-          By jets of ink we here mean that the printers are capable of spraying ink from tiny nozzles through an electrical field for the printing of characters at a high speed, i.e., 250 characters per second.

-          These printers are more popular in comparison to dot-matrix and laser printers on account of the following reasons:

a.       Do to have unpleasant noises like dot-matrix printers.

b.      More reliable in terms of their functioning and output.

c.       Capable of producing high quality printing.

d.      Require smaller mechanical parts and thereby are portable.

e.      Provide an inexpensive way to print fully closured documents.

f.        In terms of speed, quality of printing and economy, they fall midway between the dot-matrix and laser printers.

·         LASER PRINTERS

 – use a combination of micro-electronic, laser-beam technology and photocopying technology.

-          Utilizes a light beam to form images on the paper using toner ink as the medium.

-          Are very much ahead of the dot-matrix and ink-jet printers in terms of the speed and quality of printing.

-          Are capable of printing up to 20 pages per minute, both text and graphics.

·         PLOTTERS

 – devices that help in creating high quality graphics (like charts, graphs, tables, diagrams, pictures and other computer-aided designs) on paper in multiple colors.

-          Are used when the printers fail to serve the required purposes.

-          There are 2 types of PLOTTERS:

a.       FLAT-BED PLOTTER – the paper is held stationary while the arm and the pens move over it.

b.      DRUM PLOTTER – the paper is wrapped around a drum and anchored at both ends.

·         SOUND CARDS AND SPEAKERS

– devices help the user to get output from the computers in the shape of sounds (information and results through hearing).

-          Devices that are quite common to the PC`s nowadays.

-          The sound cards usually help:

a.       In the output of sound through speakers connected to the motherboard of the computer whenever instructed by software programmes.

b.      In manipulating sound stored on a disk.

C.      CENTRAL PROCESSING UNIT

-          Falls midway between the input and output devices.

-          Whenever the data is fed into the computer through the input devices, it is processed and the resultant output is provided through the output devices.

·         MICROPROCESSOR

– it’s the main component responsible for the actual processing.

-          Is the man driving engine of the computer.

a.       PENTIUM – is the most powerful microprocessor manufactured by Intel.

b.       BIT – each of the binary digits.

c.       BYTE – the collection of 8 bits representing a character of storage.

·         MEMORY (STORAGE AND RETRIEVAL DEVICES) – is that component of the computer system which works for the storage and retrieval of data and instructions.

Types of Memory:

a.       Internal Memory – is present on the motherboard of the computer in the form of chips.

-          Also referred to as internal storage, primary storage or main memory.

Two Types of Internal Memory:

i.                     Random Access Memory (RAM) – is the memory that the computers use for storing the programmes and their data while working on them.

-it is possible to use any location in the memory at random to store data and instructions temporarily

ii.          Read Only Memory (ROM) - the information on such chip can only be  Read.

                                      -nothing fresh can be written on it.

b.      External Memory (secondary storage devices) - places restriction on the amount of data processed.

-          You will need some extra means for the storage of more data.

-          You have also noticed that in case of a power failure or switching off the PC by you, all the data stored in the internal; storage is lost.

•  FLOPPY DISKS
  

-are small, flexible and soft magnetic disks.

-are removable as well as portable.

-you can insert or remove them from a disk drive of your computer at your will.

-are in two sizes: 5 ½ inch and 3 ½ inch floppies.

-are made up of flexible plastic coated with magnetic oxide.

-the FLOPPY DRIVE is used for the task of reading or writing data on the floppy.

•  HARD DISK – is a hard and inflexible magnetic disk.

-is made from aluminum and other metals.

-is permanently housed in a sealed and contamination-free container and is located inside CPU of the computer.

-are faster than floppy disks and can also hold more data (as high as 500 MB on a disk of 3 ½ inch diameter).

•  OPTICAL DISK – the data is read and written by using a laser beam.

-the storage capacity of theses disks so much more than the magnetized disks (as far as up to 6 GB)

•  CD-ROM –is a short name used for the Compact Disk Read-only Memory.

-this optical disk is capable of storing large amount of data (up to 1GB) just equal to storage capacity of 700 floppy disks.

•  CD-RW – is a short name for Compact Disk Re-Writable.

-differs from CD-ROM in the sense that here you can write and read data in the way you do with a floppy or hard disk.

•  MAGNETO-OPTICAL DISK (MO DISKS) – advanced types of disks make use of the magnetic as well as optical disk technologies thus getting the facilities of both magnetic and optical disks.
•   PEN DRIVES – in the sequence of modern computer memory (storage and retrieval) devices, pen drives represent a portable USB (universal serial bus) flash memory devices that can be used for storage of audio, video and data files with the additional facility of quickly transfer these files from the hard drive of one computer to another.

VII.              How does a personal computer machine operate?

The Computer Hardware is in three board Categories:

i.                     INPUT DEVICES

ii.                   OUTPUT DEVICES

iii.                  CPU

Computer Machine or Hardware along with its three types of Components is only a machine in its structure and functioning. It can’t do anything of its own for us without the help of computer software.

A Computer Software is nothing but a programme or set of programmes (complete set of instructions written in a language understood by the computer machine) helpful in directing, controlling and coordinating the activities performed by the various components of the computer.

TWO TYPES OF SOFTWARES:

A.      APPLICATION SOFTWARE

-          Are programmes designed for the users to make general or specific application of the computer machine?

-          May be as simple as to draft a letter or add a few numbers or as complex as preparation for landing on the moon.

-          For general Application, you may have softwares:

a.       Word Processors

b.      Spreadsheets such as Microsoft Excel

c.       Presentation graphics like Microsoft PowerPoint

d.      Database management systems like Microsoft Access

B.      SYSTEM SOFTWARE

-          Are computer machine-dependent programmes that are generally provided by the manufacturer along with the computer hardware?

-          Are installed in the computer machine for the purpose of easy functioning of the computer system.

Types of System Software:

a.       Complier Software- is helpful in converting various types of computer languages like FORTRAN, PASCAL, COBOL and BASIC, into a language of electrical signals called MACHINE LANGUAGE only understood by the computer machine.

b.      Utility Software – provides services and utilities for supporting the operations, management and uses of a computer system.

Examples:

•  Back up and restore
•  Sort and merge utility software
• Calculator utility
•  Screen savers

c.       Operating Systems – are most essential for operating a computer in the most convenient and effective way.

VIII.            What is a Computer Network?

Computer Network- is an arrangement for linking two or more computer, so that the can communicate with each other over a transmission medium referred as Data Communication Channel. The data communication channels mostly employed for the desired interconnection between two locations (two or more computer terminals) are cables, telephone lines, microwaves and satellite links.

NETWORK MODELS

A.      STAR NETWORK

– there is one centralized computer (called host computer or server) which is inter-connected with other computers.

-          No two computers can communicate with each other directly.

-          Is the centralized computer that controls the whole process of communication?

-          Suits the purpose of those institutions, offices and establishments which have to share the pooled database or costly device like laser printer.

B.      BUS NETWORK

 – each computer is connected to ingle common communication cable or bus (an electronic path).

-          Facilititates direct inter-communication among the different computers or devices included in the network.

-          Is frequently used in LAN.

C.      RING NETWORK

- all the different computers are connected to each other on a ring shape.

-          All computers can communicate with each other without the help of a centralized host computer as happens in the case of star-shaped networking.

D.      COMPLETELY CONNECTED NETWORK

-          Each computer has complete interaction with all other computers in the network.

-          The communication between two computers is highly reliable, fast and independent.

-          The breakdown of any line doesn’t affect the communication between two computers.

E.       LAN (LOCAL AREA NETWORK)

 – a network connects two or more computers with a geographically close vicinity and relatively small area.

-          Such arrangement serves the purpose well in sharing the information/data and resources within a limited and small area like an office building, school or college campus.

-          Here, the task of networking may be carried out by following model like star, ring, and bus or completely connected according to the needs and circumstances.

F.       MAN (METROPOLITAN NETWORK AREA)

 - falls midway between LAN and WAN.

-          Indicates the type of network maintained for connecting the computers in different parts of metropolitan city.

G.     WAN (WIDE AREA NETWORK)

 - covers a relatively large geographical area and greater distances.

-          You certainly neon WAN for establishing a network between different locations in a large city or among different cities or places within a province and country or among different nations of the world.

-          Are commercial networks subscribed by anyone or may be run privately by companies or big concerns only for their internal use.

IX.                What is Internet?

Internet- is the short name for the Internet System.

-          Is known as the largest WAN in the world.

-          May be defined as the world’s largest inter-network system (the network of networks) that provides the fastest, easiest and cheapest means for the countless users to get provide and communicate information on a global crisis.

·         INTERNET ACCESS

Connecting your PC to the Internet you may avail benefits from its so many valuable applications like e-mail, World Wide Web (WWW) and file transfer. You may do it simply by establishing a dialing-up connection to the Internet by the following arrangement:

a.       A telephone connection.

b.      A modem-internal or external

c.       Computer PC.

d.      An account with some Internet Access provider such as VSNL, Mantra, HCL, and Satyam.

e.      The appropriate software.

·         INTERNET PROTOCOLS

-is a set of rules observed by the software in the Internet operation.

Types of Internet Protocols:

a.       FILE TRANSFER PROTOCOL (FTP)

-          Is the protocol that helps in transferring files between the computers connected through a network?

b.      HYPERTEXT TRANSFER PROTOCOL (HTTP)

-          May be defined as the protocol that governs the transfer of hypertext between two or more computers.

-          Is the powerful tool for accessing information on the web?

HOW DOES HTTP WORK?

        It works on the client/ server principle. Your PC works as a client to establish a connection on the computer (server) having resources at its command, the client programme uses HTTP to initiate a connection with the server, to make request regarding seeking some information about a particular area.

·         INTERNET TOOLS AND SERVICES

a.       ELECTRONIC MAIL- stands for an internet tool or service that is used for exchanging information and documents between the people, no matter sitting anywhere across the country or around the world.

b.      WORLD WIDE WEB (WWW) – is one of the fast growing valuable services offered on the Internet to the users at a time worldwide.

HOW TO ACCESS INFORMATION THROUGH WWW?

        You can request a web page from a website or server by using the web browser. Web browser helps you as a client in contacting a web server, sending a request for the information you desire, receving the information, and then displaying it on your PC.

SURFING- is a process of browsing without tools.

·         E-COMMERCE – a short name for the electronic commerce.

-          Stands for the services in the field of business, trade and commerce through the use of Internet.

-          Has revolutionized the field of trade and commerce on the pattern set by e-mail in the area of communication.

VARIOUS UTILITIES OF E-COMMERCE:

a.       Internet services, utilized in e-commerce, have made possible to have big advertisements n provides worldwide information on the part of business establishments and commercial concerns for there products and services.

b.      It enables purchased through electronic means.

c.       It has made the financial transaction of all kinds possible in a quite convenient and speedily way.

d.      The use of AUTOMATIC TRANSACTION PROCESS (ATP), AUTOMATED TELLER MACHINES (ATM) and smart cards has almost revolutionized the commercial and personal banking in a very big way.

e.      Through ATP, now you can provide transaction instruction using your PC and enjoy deposit and withdrawal facilities at your home.

f.        Through ATM, you can have electronic funds transferfrom the computer terminals by using the ATM cum-debit card.

g.       Smart cards are the latest development in the field of electronic fund transfer.

X.                  COMPUTER VIRUS

-          Is all about the biological viruses.

-          Actually is not an organism but a software programme or code that has been written to copy itself into another computer files.

-          Gets executed automatically whenever the infected file is used and destroys data and other programmes in the host computer`s storage media.

HOW DOES A COMPUTER VIRUS HARM AND SPREAD?

                A computer virus normally gets attached itself to other computer programmes and becomes part of them. A virus programme is written in such a way that it gets loaded into the computer`s memory and executed automatically. Then it copies the virus instructions into all the other programmes that are being executed on that computer. This activity is also called as “infecting” the system/files.

                The infection can then spread itself to other computers through sharing floppy disks, LAN, memory-storage devices, computer networks-mail, internet or other on-line systems. Some viruses are harmless as they display jokes or messages on the screen without damaging the system. But some other viruses can crash (destroying data and programmes) a large computer system within minutes.

TYPES OF VIRUSES

A.      Based on threat:

·         BENIGN –may cause annoyance by slowing performance, displaying messages on a certain date or playing a song at a given time, but they do not cause real damage.

·         MALIGNANT – ca cause major disasters such as destroying or damaging file and crashing the entire system.

B.      Based on Computer Associates:

·         FILE INFECTORS – these viruses attach themselves to or replace the .com and .exe files. When you run the infected programme the virus code first executes. After it has finished loading and executing, it loads the programme it has infected.

·         BOOT SECTOR VIRUSES – contains information related to the formatting of the disk, the data stored there and also a programme called the boot programme. It places their code in this sector, because the machine will automatically execute this code when booting. These viruses are spread by leaving an infected diskette in the drive.

·         MULTI-PARTITE VIRUSES – are a combination of a file and a boot sector infector. They will infect both boot files and boot areas.

·         MACRO VIRUSES – viruses that consist of instructions in world Basic or some other macro language, and reside in documents or templates. They attach these macros to these documents in such a way that when an application loads the file, the first instructions it executes are those of the virus.

EVOLUTION OF THE COMPUTER VIRUSES

        Computer viruses are not new. They have been around since the 1980s. In 1983, Dr. Frederick Cohern of the University of Pennsylvania experimented with a self-replicating computer code and called it ‘virus’. However, the first known virus was brain, created in 1985 by two Pakistani brothers-Basid and FarooqAlvi, who ran a small software company in Lahore. Since the, the field of viruses has been in a constant state of evolution day by day.

        In their early days, viruses could spread only through the shared diskettes and floppies. At that time you would have only got a virus by booting your machine with an infected floppy disk or perhaps downloading a game or programme that could reach the hard drive.

HOW TO FACE THE EVIL?

·         Preventive measures:

1.       Just like diseases of the body, computer viruses are best fought before they occur.

2.       Just as biological viruses hit a human body with weak immune system, the computer viruses damage machines that aren’t protected. And just like you vaccinate your body to avoid being infected, you need to vaccinate your machines to avoid the computer viruses.

3.       Ensure scanning all the incoming floppy disks by using anti-virus software before using them.

4.       If your institution has a network, al floppy drives must be disabled, except one or two; preferably in the IT support cell.

5.       Be careful while using the internet services.

6.       You should always maintain a complete backup of all important  information and data, which should be updated regularly

7.       While surfing on the net, appropriate care should be taken.

·         CURATIVE MEASURES

There is an urgent necessity of having an early detection and confirmation that there has been a virus attack. You can detect the presence of a virus by strange messages that may pop up on the screen.

XI.                SUMMARY

1.       A computer may be known as a thinking machine of the human being that makes use of some well-framed, meaningful programmes (software) for its operation and utilities.

2.       Depending upon their performance, size and cost, modern computers may be classified into four categories, namely MINICOMPUTERS, MAINFRAMES, SUPER COMPUTERS and MICROCOMPUTERS.

3.       The hardware of your PC may be divided into three main units, i.e. INPUT DEVICES UNIT, OUTPUT DEVICE UNIT and CENTRAL PROCESSING UNIT.

4.       Computer machine or hardware for its operation makes use of two types of software, application and system software.

5.       A computer network is an arrangement for linking two or more computers so that they can communicate with each other over a transmission-medium like cables, telephone lines, microwaves and satellite links.

6.       The terms LAN, MAN and WAN used in the field of networking signifies the largeness or smallness of the distance and area covered by a network system.

7.       Internet may be considered as a name for a largest and fast World Wide System consisting of people, information and computers capable of communicating and sharing data among the indefinite number of users at a time scattered all over the world.

8.       The users of the computers may be haunted many times with a major problem or difficulty named as computer virus.

XII.              REFERENCES AND SUGGESTED READINGS

·         Besag, Frank p., Computer Literacy for Teachers, Beverly Hills: Sage Publications, 1984.

·         Fitting, Marjorie Anne and Roy Dubisch, Computer Literacy, Pacific Grove, CA: Midwest Publications, 1984.

·         Gill, N.S., Essentials of  Computer  and Network Technology, Delhi, Khanna Book Publishing Co., 2000

·         Kershner,Helene G., Computer Literacy, (2^nd ed.), Lexington, Mass:D.C. Health, 1992.

·         Koch, Warren J., The Use of Computers in Education in Secondary Schools, Washington: National Association of Secondary School Principals, 1972.