I ns t i t ut eo fMa na g e me nt & Te c hni c a lSt udi e s
I NFORMATI ONTECHNOLOGY
500
I NFORMATI ONTECHNOLOGY
www. i mt s i ns t i t ut e . c om
IMTS (ISO 9001-2008 Internationally Certified) INFORMATION TECHNOLGY
INFORMATION TECHNOLOGY
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INFORMATION TECHNOLOGY
CONTENTS: UNIT – I
01-08
Information Technology: Definition, Need and Scope – Impact of Information Technology and Library and Information Services UNIT – II
9-38
Generation of Computers- Storage Devices – Operating Systems – Types- Single – Multiuser – Functions of OS – WINDOWS, LINUX, UNIX. UNIT – III
39-54
Networking: Need- Purpose- Types – LAN, WAN, MAN, TopologiesBus- Star- Ring- Network Servers UNIT – IV
55-81
Network Protocols: TCP/IP, IP, HTTP – Hypertext – HypermediaMultimedia – ISDN- OSI. Accessories – Bridges – Routers - Switches UNIT – V
82-109
Internet: Historical Development – Types of Connectivity- ISP – Web Resources – Web Portals – Browsers- Search Engines – Internet Tools - FTP
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INFORMATION TECHNOLOGY
UNIT I : INFORMATION TECHNOLOGY 1.1 1.2 1.3 1.4 1.5 1.6 1.7
Objectives What is Information Information Science as Discipline Information Technology Impact of Information Technology Other branches of Information Technology References
1.1 OBJECTIVES This lesson gives a brief description about Information Technology. After completing this lesson one should be able to
Understand the Information Technology
Describe the need of Information Technology
Impact of Information Technology on Library and information Science
Different Branches of Information Technology
1.2 WHAT IS INFORMATION Information is an essential ingredient in decision making and the need for improved information systems in recent years has been made critical by the steady growth in size and complexity of organization and data. Information is an all pervasive resource in every human activity and helps in establishing a continuum from the past to the present and ultimately to the future. The natural consequence of all activities tends to generate large amounts of data/information. This information is recorded and stored only when it is expected to have potential importance. Thus Information is some meaningful message recorded in conventional or nonconventional media and stored and processed by systems and services with a view to providing a more or less permanent memory of the messages and their dissemination to users. Information has a synergizing effect in several areas of human activities. These can be categorized broadly as
Research and Development activities, particularly, knowledge creation, innovation, invention, diffusion, dissemination, distribution use, technology transfer, adaptation and product development.
Educational – learning and teaching at all level, both academic and professional publishing.
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INFORMATION TECHNOLOGY
Economic – employment patterns, income, prices, value, inflation, growth dynamics, development at macro and micro-levels, etc.
Political – political organizations, political systems bureaucratic systems, activities, levels of power devolution, regional and institutional development.
Social – population pressure, urbanization, rural infrastructural development, mobility group dynamics, etc.
1.3 INFORMATION SCIENCE AS A DISCIPLINE Information science is a discipline that deals with the processes of storing and transferring information. It attempts to bring together concepts and methods from various disciplines such as library science, computer sciences and engineering, linguistics, psychology, and other technologies in order to develop techniques and devices to aid in the handling — that is, in the collection, organization, storage, retrieval, interpretation, and use — of information. The transfer of information through time requires the existence of some storage medium, which is designated a document — hence the term documentation. The discipline grew in response to the growth of the periodical and the journal as the prevalent media for scientific reports. Whereas books required control through cataloguing and classification, periodicals required indexes and abstracts that would bring together for the researcher primary information originally published in divergent sources.
1.4 INFORMATION TECHNOLOGY Information technology has made the major contribution of opening up the use of computer technology to people other than computer professionals. Interactive applications in the office and home have been made possible by the development of easy-to-use software products for the creation, maintenance, manipulation, and querying of files and records. The database has become a central organizing framework for many information systems, taking advantage of the concept of data independence, which allows data sharing among diverse applications. Database management system (DBMS) software today incorporates high-level programming facilities that do not require one to specify in detail how the data should be processed. Modern information systems also bring new efficiency to the organization, retrieval, and dissemination of recorded information. The control of the world's information store has been truly revolutionized, revealing its diversity in hitherto unattainable detail. Information
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INFORMATION TECHNOLOGY services provide mechanisms to locate documents nearly instantaneously and to copy and move them electronically. New digital storage technologies make it economical for some to obtain for personal possession those collections equivalent to the holdings of entire libraries and archives. Alternately, access to information resources on electronic networks permits the accumulation of highly individualized personal or corporate collections in analog or digital form or a combination of both. As the imprint of technology expands, some of the fundamental concepts of the field, which often took centuries to evolve, are strained. For instance, information technology forces an extension of the traditional concept of the document as a fixed, printed object to include bodies of multimedia information. Because of their digital form, these objects are easy to manipulate; they are split into parts, recombined with others, reformatted from one medium to another, annotated in real time by people or machines, and readied for display in many different formats on various devices. Control of these "living" documents, which mimic human association and processing of ideas and are expected to become one of the most common units of the digital information universe, is but one of the challenges for the emerging virtual library of humankind. 1.5 IMPACT OF INFORMATION TECHNOLOGY An equally significant new dimension of modern information systems lies in their ability to manipulate information automatically. This capability is the result of representing symbolic information in digital form. Computer-based information systems are able to perform calculations, analyses, classifications, and correlations at levels of complexity and efficiency far exceeding human capabilities. They can simulate the performance of logical and mathematical models of physical processes and situations under diverse conditions. Information systems also have begun to mimic human cognitive processes: deductive inference in expert systems, contextual analysis in natural-language processing, and analogical and intuitive reasoning in information retrieval. Powerful information-transforming technologies now available or under development — data or text to graphics, speech to printed text, one natural language to another — broaden the availability of information and enhance human problem-solving capabilities. Computer visualization is dramatically altering methods of data interpretation by scientists; geographic information systems help drivers of the latest automobiles navigate cities; and interactive applications of networked multimedia computers may, for some, replace newspapers, compete with commercial broadcast television, and give new dimensions to the future of education and training at all levels of society. Information systems applications are motivated by a desire to augment the mental information-processing functions of humans or to find adequate substitutes for them. Their
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INFORMATION TECHNOLOGY effects have already been felt prominently in three domains: the economy, the governance of society, and the milieu of individual existence. Information systems may be divided into two categories:
organizational systems and
public information utilities.
Information systems in formal organizations may be further distinguished according to their main purpose: support of managerial and administrative functions or support of operations and services. The former serve internal functions of the organizations, while the latter support the purposes for which these organizations exist.
Management-oriented information systems
Administration-oriented information systems
Service-oriented information systems
Transaction-processing systems
Expert systems
1.5.1 Management-oriented information systems The most important functions that top executives perform include setting policies, planning, and preparing budgets. Depending on the nature of the organization's business, such indicators may relate to the status of high-priority programmes; health of the economy; inventory; and cash levels; performance of financial markets; relevant efforts of competitors; utilization of manpower; legislative events; and so forth. 1.5.2 Administration-oriented information systems Administrative functions in formal organizations have as their objective the husbanding and optimization of corporate resources — namely, employees and their activities, inventories of materials and equipment, facilities, and finances. Administrative information systems support this objective. Commonly called management information systems (MIS), they focus primarily on resource administration and provide top management with reports of aggregate data. Executive information systems may be viewed as an evolution of administrative information systems in the direction of strategic tracking, modelling, and decision making.
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Typically, administrative information systems consist of a number of modules, each supporting a particular function. The modules share a common database whose contents may, however, be distributed over a number of machines and locations. Financial information systems have evolved from the initial applications of punched cards before World War II to integrated accounting and finance systems that cover general accounting, accounts receivable and payable, payroll, purchasing, inventory control, and financial statements such as balance sheets. Functionally close to payroll systems are personnel information systems, which support the administration of the organization's human resources. Job and salary histories, inventory of skills, performance reviews, and other types of personnel data are combined in the database to assist personnel administration, explore potential effects of reorganization or new salary scales (or changes in benefits), and match job requirements with skills. 1.5.3 Service-oriented information systems Such information systems provide support for the operations or services that organizations perform for society. The systems are vertically oriented to specific sectors and industries
(manufacturing,
financial
services,
publishing,
education,
health,
and
entertainment). Rather than addressing management and administrative functions, they support activities and processes that are the reason for an organization's existence —in most cases, some kind of manufacturing activity or the rendering of services. Systems of this kind vary greatly, but they tend to fall into three main types: manufacturing, transaction, and expert systems. The conceptual goal of modern factories is computer-integrated manufacturing (CIM). The phrase denotes data-driven automation that affects all components of the manufacturing enterprise: design and development engineering, manufacturing, marketing and sales, and field support and service. Computer-aided design (CAD) systems were first applied in the electronics industry. Today they feature three-dimensional modelling techniques for drafting and manipulating solid objects on the screen and for deriving specifications for programmes to drive numerical-control machines. Once a product is designed, its production process can be outlined using computer-aided process planning (CAPP) systems that help to select sequences of operations and machining conditions. Models of the manufacturing system can be simulated by computers before they are built. The basic manufacturing functions — machining, forming, joining, assembly, and inspection — are supported by computer-aided manufacturing (CAM) systems and automated materials-handling systems. Inventory control systems seek to maintain an optimal stock of parts and materials by tracking inventory movement, forecasting requirements, and initiating procurement orders.
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INFORMATION TECHNOLOGY 1.5.4 Transaction-processing systems In non-manufacturing service organizations the prevalent type of information system supports transaction processing. Teleprocessing transaction systems constitute the foundation of service industries such as banking, insurance, securities, transportation, and libraries. They are replacing the trading floor of the world's major stock exchanges, linking the latter via online telecommunications into a global financial market. Again, the core of a transaction system is its integrated database. The focus of the system is the recipient of services rather than the system operator. Because of this, a local travel agent is able to plan the complete itinerary of a traveller — including reservations for airlines, hotels, rental cars, cultural and sports performances, and even restaurants, on any continent — and to tailor these to the traveller's schedule and budget. 1.5.5 Expert systems A relatively new category of service-oriented information systems is the expert system, so called because its database stores a description of decision-making skills of human experts in some narrow domain of performance, such as medical image interpretation, taxation, brickwork design, configuration of computer system hardware, troubleshooting malfunctioning equipment, or beer brewing. The motivation for constructing expert systems is the desire to replicate the scarce, unstructured, and perhaps poorly documented empirical knowledge of specialists so that it can be readily used by others. Expert systems have three components: 1. a software interface through which the user formulates queries by which the expert system solicits further information from the user and by which it explains to the user the reasoning process employed to arrive at an answer, 2. a database (called the knowledge base) consisting of axioms (facts) and rules for making inferences from these facts, and 3. a computer programme (dubbed the inference engine) that executes the inference-making process. The building of information systems falls within the domain of engineering. As is true with other engineering disciplines, the nature and tools of information systems engineering are evolving owing to both technological developments and better perceptions of societal needs for information services. Early information systems were designed to be operated by information professionals, and they frequently did not attain their stated social purpose. Modern information systems are increasingly used by persons who have little or no previous
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INFORMATION TECHNOLOGY hands-on experience with information technology but who possess a much better perception about what this technology should accomplish in their professional and personal environments. A correct understanding of the requirements, preferences, and "information styles" of these end users is crucial to the design and success of today's information systems. 1.6 INFORMATION TECHNOLOGY BRANCHES Internet is a network connecting many computer networks and based on a common addressing system and communications protocol called TCP/IP (Transmission Control Protocol/Internet Protocol). From its creation in 1983 it grew rapidly beyond its largely academic origin into an increasingly commercial and popular medium. Electronic mail (e-mail) is messages transmitted and received by digital computers through a network. An e-mail system allows computer users on a network to send text, graphics, and sometimes sounds and animated images to other users. Cryptology (from the Greek kryptos, "hidden", and logos, "word") is the science of secure (generally secret) communications. The need to protect sensitive data ( for national security) has led to extensive research in cryptography and the development of encryption standards for providing a high level of confidence that the data is safe from decoding by even the most powerful computer attacks. This security obtains from legitimate users, the transmitter and the receiver, being able to transform information into a cipher by virtue of a key — that is, a piece of information known only to them. Cryptography (from the Greek kryptos and graphein, "to write"), is the study of the principles and techniques by which information can be concealed in ciphers and later revealed by legitimate users employing the secret key, but in which it is either impossible or computationally infeasible for an unauthorized person to do so. Cryptanalysis (from the Greek kryptos and analyein, "to loosen" or "to untie") is the science (and art) of recovering information from ciphers without knowledge of the key. Cryptography was concerned initially with providing secrecy for written messages. Its principles apply equally well, however, to securing data flow between computers, to digitized speech, and to encrypting facsimile and television signals. Most communications satellites, for example, routinely encrypt the data flow to and from ground stations to provide both privacy and security for their subscribers. Because of this broadened interpretation of cryptography, the field of cryptanalysis has also been enlarged to include the recovery of information from ciphers concealing any form of data.
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INFORMATION TECHNOLOGY Applied computer technologies and more recently, the theoretical areas of study of information science have since permeated many other disciplines and have even been appropriated by new fields, each preferring a more descriptive designation of its subject domain. The institutionalization of information science as a discrete discipline thus has not occurred, and the number of its scientist-practitioners is low. Computer science and engineering tend to absorb the theory- and technology-oriented subjects of the field, and management science tends to absorb the information systems subjects. Hundreds of professional associations do exist that are concerned with information-related disciplines, providing a forum where people can exchange ideas about information processing. The proliferation of automatic data-logging devices in scientific laboratories, hospitals, transportation, and many other areas has created a huge body of primary data for subsequent analysis. Machines even generate new information: original musical scores are now produced by computers, as are graphics and video materials. Electronic professional workstations can be programmed to carry out any of a variety of functions. Some of those that handle word processing not only automatically look for spelling and punctuation errors but check grammar, diction, and style as well; they are able to suggest alternative word usage and rephrase sentences to improve their readability. Machines produce modified versions of recorded information and translate documents into other languages. 1.8 CONCLUSION Thus Information Technology provides a dominating face in each and every profession. The boundaries of Information Technology gets expanded from Science, Medical, Engineering, Technology to Society and find intrusion in day to day offers of the human life cycle.
It created an instinct in such a manner that now-a-days, most of the computer
illiterates rush to learn the development of Information Technology and to finding the possibilities of applying the same in their day to day activities. 1.9 UNIT QUESTIONS Answer the following questions 1. What is information 2. “Whether the information Science is a discipline?� Discuss. 3. Discuss the impact of Information Technology in LIS 4. What are the branches of Information Technology?
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UNIT II OVER VIEW OF COMPUTER TECHNOLOGY 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10
Objectives Introduction to Computers Generation of Computers Storage Devices Software and its types Operating system – types and functionality Unix Linux Windows References
2.1 OBJECTIVES After studying this lesson, you should be able to
Understand the computer technology
Describe the various storage devices
What is Operating System
Different types of Operating System
Functionality of Windows, Unix, Linux
2.2 INTRODUCTION TO COMPUTERS
A computer is an electronic machine. It can do variety of jobs at a faster rate. It is being used in many places, like offices, industries, medical centres, banks, schools etc. It is basically a calculating machine.
It is capable of performing the operations like addition,
multiplication, subtraction, division etc. The computer is also capable of storing information which can be used for the future use.
2.2.1Definition for Computer:
Computer is a machine which is able to accept data in a prescribed form, process the data and supply the results of the processing in a specified format as information or as signals for controlling automatically some other process or function. The word computer has been derived from the Latin Word “computare” which means “to calculate”. The word Computer according to the Oxford English Dictionary is a “automatic
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electronic apparatus for making calculations or controlling operations that are expressible in numerical or logical terms.”
Computers can also be defined as under:
Computer is an electronic data processing device.
Computer is a machine for storing, communicating and manipulating information.
2.3 CLASSIFICATION OF COMPUTER Functions Analog Digital Hybrid Optical Quantum
Size & Capacity Embedded Mainframe Mini Computer Micro Computer Personal Computer PC PC/XT PC/AT PS/2 PC Clone Portable Laptop Note Book Palmtop SUPER COMPUTER
Generation FIRST SECOND THIRD FORTH FIFTH
2.3.1 COMPUTERS BASED ON FUNCTION Generally computers are classified into four broad categories based on their functions. They are
1. ANALOG COMPUTERS 2. DIGITAL COMPUTERS 3. HYBRID COMPUTERS 4. OPTICAL COMPUTERS 2.3.1.1 ANALOG COMPUTERS The analog machine does not compute directly with numbers, rather it measures physical measurements. (eg. Pressure, Temperature, voltage etc.). Speedometer in a vehicle, and fluid flow meters are some of the good examples of this kind.
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INFORMATION TECHNOLOGY 2.3.1.2 DIGITAL COMPUTERS. It operates directly on numbers expressed as digits in the familiar decimal system or some other numbering system. It gives results in greater accuracy. It can produce results with 10000th decimal places in a short period. According to the purpose of digital computers we can classify them into two types.
(i) Special purpose computers (ii) General purpose computers
(i) Special purpose computers.
As the very name implies, it is designed to perform a specific task. We cannot use it for some other purpose. Computers installed in process control equipments; computers used in pilot cabins are some of the examples of this kind.
(ii) General purpose computers. It
has the ability to store different programs of instructions and thus to perform a
variety of operations. It is used for both scientific and business applications. Now it is available for reduced price, and used commonly.
2.3.1.3 HYBRID COMPUTERS Machines that combine both analog and digital capabilities are called Hybrid computers.
Much business, scientific and Industrial computer applications rely on the
combination of analog and digital devices. The ultrasonic diagnostic system in a hospital is a good example of this system.
Analog signals generated by the Scanner as continuous
voltage are `digitized' and supplied to a small digital computer that monitors patient’s condition.
2.3.1.4 OPTICAL COMPUTERS A super high speed computer which will work on optical system i.e light signals.
2.4 GENERATION OF COMPUTERS The generation of computers can be categorized as Pre Generation and Generation Period.
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INFORMATION TECHNOLOGY 2.4.1 PRE GENERATION STAGE The development of computers to Pre generation stage comprises of eight major stages of developments. 1. ABACUS
Used mainly to add and substract numbers
First used by the Babylonians.
Used in many forms. i.e. Pebble tray, Knotted strings, Frame of beads.
Frame of beads was the most popular form.
Chinese perfected it.
This form is used in Japan & China. Even to-day it is used in Japan.
2. NAPIER'S BONES
Used for multiplying any two selected numbers.
Developed by John Napier, a Scottish mathematician.
Series of rods carved out of bones were used.
11 rods were used. Each rod is divided into nine parts. Each part is divided into two half’s.
3. PASCALINE MACHINE
Devised by Blaise Pascal, a French mathematician.
Could perform only addition and subtraction.
4. DIFFERENCE ENGINE
Designed by Charles Babbage.
Calculate the results of two 28 digits number.
5. ANALYTICAL ENGINE
Charles Babbage designed this machine.
This machine was not fully build.
This mechanical computer contains five components. They are: 1. a store to hold numbers 2. an arithmetic unit to perform arithmetic operations 3. a control unit to co-ordinate the various activities in a sequence. 4. an input device to transfer both numbers and instructions into the machine.
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INFORMATION TECHNOLOGY 5. an output device to display the results.
It is a first scale model for the present day computers
6. CENSUS TABULATOR [PUNCHED CARD]
Designed by Herman Hollerith.
Data are recorded in punched holes.
This is used to record and tabulate the US census.
7. MARK - I COMPUTER - Built by Howard H.Aiken. Supported by IBM. 8. ENIAC - Stands for Electronic Numeric Integrator And Calculator
Designed by Eckert and Mauckly.
18,000 vacuum tubes were used in their model.
It generates over heat.
It could do 5000 additions per second.
2.4. 2 GENERATION OF COMPUTERS GENERATION FIRST
SECOND
THIRD
FOURTH
CHARACTERISTICS Vacuum tubes for internal operation Low primary memory Magnetic drums & Punched cards Slow input, processing and output Low level language for programming Heat and maintenance problem eg. - EDSAC, EDVAC, LEO, UNIVAC are different computer Transistor for internal operations Primary memory: Magnetic core memory Magnetic tapes and disks were used Increase in processing speed Use of high level language started Reduction in heat and reliability eg. - IBM 7000, LEO MARK III, ATLAS Integrated circuit [IC] for operation Increased Primary memory capacity Increased speed and reliability Increased use in computers Reduction in size and cost. eg. - IBM 360, ICL 1900. Large Scale Integration [LSI], Very Large Scale Integration [VLSI] for internal operation. Introduction microprocessors Increase in speed, power and storage eg.. - DEC 10, Star 1000, PDP 11
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FIFTH
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Super Large Scale Integration [SLSI] technology Parallel processing Artificial Intelligence[AI] & Expert Systems Robotics, Multimedia etc
2.4. 3 COMPUTER BASED ON SIZE DESCRIPTION FEATURES MAINFRAME very large in size used for general purpose very extensive Input/ output facilities MINICOMPUTER
smaller than mainframe greater than micro performs better than mainframe
MICROCOMPUTER
Microprocessors are used reduction in size Special purpose computers
SUPERCOMPUTER
VLSI technology Speed of operation more eg. 10000M flops (floating operations)
COMPUTER NAME IBM 360, IBM 370 ICL 1900 ICL 2900 DEC 10 PDP11 VAX range
APPLE Commodore PET Model 4004 CRAY Cyber PARAM 2000
2.5 INPUT, OUTPUT & I/O DEVICE INPUT DEVICE Punched card Paper tapes Key Board MICR Mouse Optical Mark reader Optical Character Recogniser Light Pen Joy stick Track Ball Scanners Touch Screen
OUTPUT DEVICE VDU Printer Plotter COM Teledata/View data system
I/O DEVICE Magnetic tapes Magnetic Disks Floppy Disks Disk Pack Magnetic cards & OCR strips Magnetic drum Thumb drives Optical Storage devices - CD-Rom - DVD Technology
2.6 DIRECT ACCESS STORAGE DEVICES Storage Devices also called Direct Access Storage Devices and Secondary Access Storage Devices or Auxiliary Storage Devices Some of the storage devices are used for both offline and online purpose. These storage devices can further be categoried as Magnetic Storage devices and Opticacl Storage Devices. They are:
Magnetic drums.
Magnetic disks.
Magnetic cards and strips.
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2.6.1 MAGNETIC DRUMS
Magnetic drum is a cylinder that has an outer surface plated with a metallic magnetizable film. A motor rotates the drum on its axis at a constant speed. Data are recorded on the rotating drum and read from the drum by read-write head. We can also erase the older data and write a new one on the surface.
2.6.2 MAGNETIC DISKS
Magnetic disks were invented to overcome the sequential processing requirements of magnetic tapes. They are the most popular direct access storage medium. They are made of thin metal plates coated on both sides with a magnetizable disks may remain permanently fixed in side the cabinet.
recording material.
These
This is called Hard disk or
Winchester disk. It can hold Memory capacity from 20 mb to 400 mb. The other one is portable and removable type. This is called Floppy Diskette.
2.6.3 FLOPPY DISKS
Floppy disks were introduced in early 1970's and have become very popular with the invention of the microcomputer. A diskette is permanently covered by a plastic envelope. The envelope is rigid and smoothly lined and serves as a protective covering for the diskette. Data are recorded in specific locations as magnetized spots in these diskettes.
Once
recorded, the stored data remain intact even if the power fails in the system. This disk is placed on a vertical rotating shaft and
rotates at constant speed. The read-write head
above this disk may read or write according to our instructions.
Varieties of Floppy disks Floppy disk size 1 8 inch, low 2 5 1/4 inch, low 3 5 1/4 inch, high 4 3 1/2 inch, low 5 3 1/2 inch, high 6 3 1/2 inch, extended
Capacity Low capacity, 128 K Low capacity, 360 K, or DS/DD High capacity, high-density, 1.2 MB Low capacity, 720 K, or DS/DD High capacity, high-density, 1.4 MB Extended capacity, 2.8 MB
2.6.4 MAGNETIC CARDS AND STRIPS A magnetic card is considered to be a length of flexible plastic material upon which short strips of magnetic tape have been mounted. A number of cards may be placed in a cartridge which, like disk packs, may be removed and stored offline.
Cards and strips
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INFORMATION TECHNOLOGY equipment has high storage capacity and data are erasable, but access speed is slow when compared with drums and disks. 2.6.4.1 THUMB DRIVE/PEN DRIVE
Towards the development of magnetic strips, today there exist a pen drive. Sometime it is also termed as thumb drive. These thumb drives are having a minimum storage capacity of 256 MB to 10 GB. These thumb drives are easily portable and attachable to any system with USB port. This technology certainly replace the concept of hard disk shortly.
2.6.5 DISK PACK A disk Pack consists of a number of inseparable disks joined together as a single unit, the number usually being either 6 or 11. Each disk can store 30 - 60 million characters and the capacity of a disk pack is around 200 million characters. But for the outer-most two surfaces, all the other surfaces in a pack are used for recording. So in a 6 disk pack, there are 10 recording surfaces [(6 x 2) - 2] and in a 11 disk pack there are 20 recording surfaces [(11 x 2) - 2].
2.6.6. FLOPTICAL DISK & DRIVE Floptical disk or drive which uses the optical principle of storage rather than the magnetic will become a new standard. Floptical drives cost nearly 10 times as much as the conventional 3.5 inch variety - but the flopical disk too store about 10 times as much.
2.6.7 OPTICAL STORAGE DEVICES 2.6.7.1 CD ROM CD ROM is a powerful peripheral for personal computers emerging in the PC marked in 1985 and gaining momentum ever since.
CD ROM or Compact Disk - Read Only Memory, is a significant new technology that enables millions of bytes of data to be stored on an ordinary compact disc. CD ROM provides numerous benefits compared with other form of information storage and retrieval.
CD ROM discs are circular, 120mm diameter objects made from bulletproof polycarbonate, with a shiny under layer that stores digital information. Only one side of the disc is used for data storage.
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INFORMATION TECHNOLOGY CD ROM disc can store up to 660 mega bytes of information. This is about 260,000 pages of text or 74 minutes of music or video.
Another way of looking at the storage capacity is to compare CD ROM to its ubiquitous relative, the floppy disc. Squeezing 660,000 bytes on to a single floppy disc using the 9 tracks per inch format of a standard MS DOS 360 k diskette would require a diskette approximately 800 ft. across. ADVANTAGES OF CD-ROM 1.
Permanent storage - it cannot be erased, scratched or mutilated.
2.
High density storage - more than 2,50,000 pages can be recorded
3.
The drive head does not touch the plate when scanned for retrieval. Hence the drive head will not crash or no wear and tear.
4.
Physically portable and can be mailed in cover.
5.
Data recorded can easily be transferred to any other medium through PC.
6.
Low cost.
7.
Text, Image and Multimedia based information storage and retrieval gets gaining momentum.
DISADVANTAGES 1.
As the name implies the discs are read only, data cannot be written into them. For retrieval systems this may, however, be an advantage as users are prevented from accidentally or deliberately erasing data.
2.
The information on the discs cannot be as current as is possible with an on-line retrieval system using magnetic storage.
3.
Access time as compared with hard magnetic disc is more
4.
The systems single-user, the data base(s) on a disc may be accessed only by one user.
5.
Although the capacity is large, it is still not nearly large enough for the largest data bases.
2.6.7.2 DIGITAL VIDEO TECHNOLOGY DVD, which is once stood for Digital Video Disc and later Digital Versatile Disc, is now just "DVD". It is no longer an acronym that it once was. DVD is today's premiere format for video, audio, and data storage.
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The Disc As a disc, DVD looks very much like the CD. Both are shiny discs that are 4 3/4 inches (12.0 cm) in diameter. Both are optical formats containing digital information. This means a laser pickup is used to read the digital data encoded on the disc. But that's where the similarities end.
DVD is actually a family of physical and application formats. As far as the physical format, DVD can hold anywhere from seven times to over 25 times the digital data on a CD, depending on the disc's construction. Additionally, the DVD may be used for video, audio, or data storage applications as a DVD-Video, DVD-Audio, or DVD-ROM application format, respectively.
DVD Physical Specifications Specification Diameter Thickness Numerical aperture Readout wavelength Track pitch Pit length Capacity (per side) Scanning speed Rotational speed (1x) Reflectivity User data rate (1x)
CD 12 cm 1.2 mm .60 780nm 1.6 micrometers
DVD 12 cm 1.2 mm (.6 mm x2) .38 to .45 650 or 635 nm .74 micrometers .400 to 1.866 micrometers .440 to 2.054 .822 to 3.560 micrometers micrometers 4.7 GB (single layer), 8.5 GB (dual 650 MB layers) 1.2 to 1.4 m/s 3.49 m/s 3.84 m/s 200 to 500 rpm 570 to 1600 rpm 70% minimum 45 to 85% 1.41 Mbps 11.08 Mbps Physical Format
There are three reasons for DVD's greater data capacity: 1. Smaller pit size 2. Tighter track spacing 3. Multiple layer capability Application Formats The various application formats of DVD are:
DVD-Video, DVD-Audio, and
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Each of these three application formats are based on the physical specifications are discussed.
DVD-Video. The DVD-Video format is by far the most widely known, as it is the first DVD application format to really take off. As the name indicates, DVD-Video is principally a video and audio format used for movies, music concert videos, and other video-based programming. This format first emerged in the spring of 1997 and is now considered mainstream.
DVD-Audio. The DVD-Audio format features high-resolution 2-channel stereo and multi-channel (up to 6 discrete channels of) audio. The format made its debut much later, in the summer of 2000, due to delay in squaring away the copy protection issue. To date, DVDAudio titles are still very few in number and have not reach mainstream status, even though DVD-Audio/Video players are numerous and widely available. DVD-ROM. DVD-ROM is a data storage format just like CD-ROM. DVD-ROMs can only be used in DVD-ROM drives in computer systems. They allow for data archival and mass storage, as well as interactive and/or web-based content.
It should be noted that a DVD disc might contain any combination of DVD-Video, DVD-Audio, and/or DVD-ROM application content. For example, some DVD movie titles contain DVD-ROM content portion on the same disc as the movie. This DVD-ROM content provides additional interactive and web-based content that can be accessed when using a computer with a DVD-ROM drive. As another example, some DVD-Audio titles are actually DVD-Audio/Video discs that actually have additional DVD-Video content that provide videobased bonus programming such as artist interviews, music videos, or a Dolby Digital and/or DTS surround soundtrack that can be played back by any DVD-Video player (in conjunction with a 5.1-channel surround sound home theater system). Recordable DVD Formats?
DVD is actually a family of formats. As such, the DVD format also includes recordable formats. The DVD specifications define three different recordable DVD formats:
DVD-R (and DVD-RW, the re-writeable version of DVD-R, like CD-RW is to CD-R)
DVD+R (and DVD+RW, the re-writeable version of DVD+R)
DVD-RAM (re-writeable by definition)
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INFORMATION TECHNOLOGY Each of these recordable DVD formats are slightly different. Their differences are enough to create mutually incompatibility issues. In other words, one recordable format can not be used interchangeably with the other two recordable formats. And one of these recordable formats is not even compatible with most of the 17 million existing DVD-Video players. The benefits of DVD The major advantages are:
Pure Digital Format
Improved Picture Quality and Color
State-of-the-Art Surround Sound
Multiple Language Dialogues and Soundtracks
Multiple Angles Option
Random Access To Scenes
Durable Disc Format
2.7 WHAT IS SOFTWARE? Software is the brain of the operation. The instruction, which tell the computer what to do, how to act. SOFTWARE
SYSTEM SOFTWARE
APPLICATION SOFTWARE (PROGRAMMING LANGUAGE)
OPERATING SYSTEM TRANSLATORS & CONTROL PROGRAMS
ASSEMBLERS COMPILERS INTERPRETERS | | | | | | COMMERCIAL SCIENTIFIC SPECIAL COMMAND UTILITIES LANGUAGE LANGUAGE LANGUAGE LANGUAGE eg COBOL eg. BASIC eg. PL/1 eg. JCL FORTRAN PASCAL | DBMS
| | | TEXT SPREED GRAPHICS EDITOR SHEET eg. dBASE eg. WS eg.LOTUS eg. AUTOCAD
2.7.1 PROGRAMMING LANGUAGES As mentioned earlier, programming languages are mainly of two types:
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(a) LOW-LEVEL LANGUAGES These languages are machine-oriented and hence are called low-level languages. Assembly language is an example of a low level language.
(b) HIGH-LEVEL LANGUAGES These languages have been developed to make programming easier.
These
languages are very close to the English language and are more sophisticated. They move away from
machine dependence,
unlike the low-level languages.
extensive vocabulary of words, symbols and sentences.
They have
an
All instructions have to be written
adhering to some rules known as the syntax of the language. These correspond to the grammatical rules in English. The high-level languages are also translated into the machine code and the translators used may be Compilers or Interpreters. There are many types of high-level languages. (i)
COMMERCIAL LANGUAGES:
As their name suggests,
well suited for all commercial applications.
these languages are
The most common commercial language,
introduced in 1961, is COBOL which means COmmon Business Oriented Language. This language is very close to the English language and can be understood by all.
(ii)
SCIENTIFIC LANGUAGES: These high-level languages are used for scientific
and engineering purposes. They have very powerful mathematical facilities. FORTRAN, ALGOL & BASIC are examples of scientific languages.
(iii) SPECIAL-PURPOSE LANGUAGES: These languages cater to some specific problems like simulation and control of experiments. eg. Ada
(iv) COMMAND LANGUAGES FOR OPERATING SYSTEMS: These languages are required to control the operation of the computer system. An example of the command language is JCL (Job Control Language).
(v)
MULTIPURPOSE LANGUAGES: These languages have a very wide range of
applications and can be used for scientific, engineering, commercial and other purposes. eg. PL/1, PASCAL
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2.8 WHAT IS OPERATING SYSTEM? Operating System is a computer program that manages the resources of a computer. In other words Operating system is a program or set of programs which co-ordinates the running of all the units of a computer, and provides communication between the computer and the person operating it.
It reads the command from keyboard, mouse; displays the information on screen and prints to a printer.
2.8.1 FUNCTIONS OF AN OPERATING SYSTEM
The functions of the operating system include assignment of system resources; scheduling of resources and jobs, and monitoring activities of a computer system. It carries out following four major management functions.
1. Task management 2. Data management 3. Program management 4. System management
2.9 DIFFERENT TYPES OF OPERATING SYSTEMS
Generally Operating systems are two different types. They are
Single User Operating system
Multi User operating system
Single User Operating System It is a single user single programming system eg. MSDOS, PCDOS, CP/M
Multi User Operating System It is a multi-user, multi programming and multitasking system eg. UNIX, ZENIX, OS/2
Different operating systems and the descriptions are given below: S.No. 1
OPERATING SYSTEM MSDOS, PCDOS
2 3 4
CP/M UNIX APPLE DOS, APPLE PRODOS
DESCRIPTION Most common PC operating system 8 bit Microcomputer OS Multiuser multitasking OS Apple II series of computer
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XENIX, VENIX TRS-DOS
7 8 9 10 11
Amiga DOS MVS,OS/VS,VM GCOS VAX/VMS AOS/VS
23 Two Unix like Operating System Tandy’s TRS-80 series micro computer Commodore Amiga IBM Mainframe Honeywell mainframe DEC’s VAX series Data general minicomputer
WHAT IS FILENAME? If any information is stored in the computer it is to be given a specific name for identifying the information. This specific name is known as FILENAME.
Single User Operating Systems filename mostly comprises of 11 characters. For example in the case of MSDOS File name should not exceed 11 characters. These 11 characters forms two part. The first part is known as User defined which comprises of 8 characters. The second part is known as file extension which comprises of 3 characters. The first part and second part is separated by a DOT. eg. RAMAN.TXT. It also holds good for MSDOS commands and the commands are stored in the form of file.
Multi User Operating Systems file name mostly comprises of 14 characters. For example In UNIX, Sco Unix one can have file name up to the maximum of 14 characters. The features of file name are
Any amounts of file extensions are allowed.
File names are case sensitive.
File extension depends on Programming languages
Any character can be used as file name.
File name must be in the form of string.
It is not advisable to begin the file name with period ie. Dot. The file name begins with “dot” then the file is hidden.
In Windows, one can have file name to the maximum extension of 254 characters. The other characteristics of the file name in windows are
The file name can have any character.
Space is also allowed between the letters.
Windows provide first line of the program/text as file name.
The same file name occurs, instead of over writing the file, it adds chorological number with the file name
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2.9.1 MSDOS OPERATING SYSTEM MS-DOS stands for Microsoft Disk Operating System. This is a must for working with IBM Personal Computers or compatibles that help to manage the peripherals i.e. system board, disk storage, printers, keyboard, visual display unit etc. It is a disk operating system for 80xx family of 16 bit computers. MS-DOS now runs on 8088, 80186, 80286, 80386, 80486, PENTIUM based systems etc.
Features:
It is a single user single programming environment
It supports both floppies and hard disks
It can coexist with other operating systems on a hard disk
It supports a hierarchical file system
It supports a variety of languages.
WHAT ARE THE IMPORTANT FILES IN DOS?
There are five important files in DOS. Two of them are MSDOS.SYS and IO.SYS, almost always hidden. They are also called system files. Other files are COMMAND.COM, CONFIG.SYS and AUTOEXEC.BAT
There are different version of DOS are available. Among the different version that are used are version 5, 6 and 6.22 etc.
MS-DOS COMMANDS: There are two types of MS-DOS commands,
Internal
External
INTERNAL COMMANDS
The internal command gets loaded automatically in the memory of PC as and when the system is switched on. The switching on the system is known as Booting. These commands are available so long as the machine is kept on. Internal commands are stored in TWO hidden files and in COMMAND.COM. Some of the internal commands are given in Table 1.
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TABLE 1: LIST OF INTERNAL COMMANDS CD or CHDIR CLS MD or MKDIR RD or RMDIR REN or RENAME LOADHIGH or LH
COPY DEL DIR DATE CALL BREAK ERASE ECHO EXIT DATA EXIT GOTO IF PAUSE PROMPT SET VOL VERIFY TYPE REM CHCP
PATH VER SHIFT
EXTERNAL COMMANDS External commands are on disk as program files. So, they must be read from the disk before they are executed. This means that the disk containing the commands must be in a drive. The external commands normally stored in the command name itself as the file name with extension either .BAT or .EXE or .COM. The external commands are shown in Table 2. TABLE 2: SOME EXTERNAL COMMANDS FORMAT DISKCOPY XCOPY BACKUP SCANDISK DOSSHELL
CHKDSK PRINT TREE MODE MORE RESTORE ATTRIB FDISK EDIT FIND UNDELETE UNFORMAT KEYBxx DOSKEY SHELL
2.9.2 UNIX UNIX is the most popular operating system on multi-user. It can be defined as a collection of programs that coordinates the operations of computer hardware and software. It has the following main features.
Multiuser, time sharing operating system
Multi-tasking operating system
Portability
Modularity
System security
File structure and security
I/O Redirection and piping
I/O independence
Communication
The major functions are
Command interpreting
Resource management
House Keeping
Program development aids
Communication
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2.9.2.1 HISTORY OF UNIX Unix is also known as UNIPLEXED Information and Computing system. It is evolved from Multics. It is developed by Ken Thompson and Kernighan in 1969. It is first loaded in to PDP-7. Originally it is written in Assemply language. In 1973 UNIX was written in ‘C’. Initally Unix was used in academic environment but quickly spread to commercial environment. 2.9.2.2 VERSIONS OF UNIX The flexibility of UNIX, which allows it to be shaped to meet a variety of needs, has always, been of its major attractions. This flexibility led to a proliferation of different version of UNIX. The different types of UNIX are -
AT & T version
-
BSD Version
-
Derivatives of UNIX – XENIX from Microsoft; UNIPLUS from UNISOFT
-
Unix looks alike – Sco Unix; Solarix, cromix, UNOS
2.9.2.3 STRUCTURE OF UNIX SYSTEMS The structure comprises of
the Kernel – implements Unix file system
the Shell – component interacts directly with user-interaction
Utilities/tools and application
User programs
2.9.2.4 TYPES OF USER Unix supports three different type of users. They are (i) Supervisor; (ii) Group user and (iii) Ordinary User. Every user has a home directory. To find out the user home directory the command is - $echo$home
2.9.2.5 FILES AND FILE SYSTEM Files can be categorized as follows:
Ordinary files – completely under user control – also called as flat files.
Directory files – contains information about files like ordinary file
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Device files – represents all hardware devices.
Unix file systems can be viewed as inverted tree.
Bin : consist of user related command file Dev : special file associated with various devices Etc : files essentially required for system administrator Lib : library routines Tmp: buffer files Usr : user defined files
User can provide their file name to the maximum of 14 characters. Unix is a case sensitive system. 2.9.2.6 SIMPLE UNIX COMMANDS The syntax of the Unix commands are $ command [options] [arguments] The options are usually preceded by “-“
2.9.2.7 FEW UNIX COMMANDS $ who - List current users of the system, terminal number, login date and time $ who am I - provides information about the user $ whoami - will display only user name $ date - will display date $ cal 2002 - displays calendar for entire year 2002 $ cal 03 2002 - displays calendar for 2002 March $ mkdir <name> - creates the directory under the given name $ cd/<name> - changes to the particular directory $ rmdir<name> - removing the directory $ cp file1 file 2 - copying file
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$ cp file1,file2 dir1 - coping all files in a particular sub directory $ ls[options][dir] - displays the list of files $ ls – l - displays the list of files – long listing format $ ls – a - displays all files including hidden files $ ls – d - displays directories alone $ ls:pg or ls|more - lists file name in pause format $ man [command] - displays the manual for the command $ diff file1 file2 - difference between file1 and file2 $ mv file1 file2 - renaming a file1 as file2 $ pr file1 - print a file $ pr –l25 filename - prints 25 lines for the page – default value is 66 lines $ pr – t - suppresses the header and trailer $ pr –h “text” - replaces the header with a string $ pr –n - produces multicolumn output $ pr –d - double spaces the output $ cat file1 file2 - compares the two files $ cat file1 - to see the contents of the file $ cat>filename - to create the file $ rm filename - delete the file $ pwd - to see the present working directory $ wc filename - to count the number of words in a given file $ cut –c1-c12 file - cuts first twelve letters of the given file $ tail -5 filename - displays last 5 lines th $ tail +6 filename - displays from 6 line onwords $ clear - clear the screen $ comm. File1,file2 - compares file1 and file2 $ grap “raman” file1 - displays occurrence of the word “raman” in the said file $ sort file1 - sorts the contents of a file into alphabetical or numerical order $ split –n filename - splits the indicated file into parts of “n” lines
2.9.3 WINDOWS
Microsoft Windows is a series of software operating systems produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs).
[1]
Microsoft Windows came to dominate the world's personal computer market, overtaking Mac OS, which had been introduced previously. At the 2004 IDC Directions conference, IDC Vice President Avneesh Saxena stated that Windows had approximately 90% of the client operating system market.
[2]
The most recent client version of Windows is Windows Vista. The
current server version of Windows is Windows Server 2008.
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2.9.3.1 Different versions of Windows Product name
Version
Release date
Last IE
Windows 1.01
1.01
November 1985
-
Windows 2.03
2.03
November 1987
-
Windows 2.11
2.11
March 1989
-
Windows 3.0
3.0
May 1990
-
Windows 3.1
3.1
March 1992
5
Windows For Workgroups 3.1
3.1
October 1992
5
Windows NT 3.1
NT 3.1
July 1993
5
Windows For Workgroups 3.11
3.11
December 1993
5
Windows 3.2 (released in Simplified Chinese only)
3.2
January 1994
5
Windows NT 3.5
NT 3.5
September 1994
5
Windows NT 3.51
NT 3.51
May 1995
5
Windows 95
4.0.950
August 1995
5
Windows NT 4.0
NT 4.0
July 1996
6
Windows 98
4.10.1998
June 1998
6
Windows 98 SE
4.10.2222
May 1999
6
Windows 2000
NT 5.0.3700.6690
February 2000
6
Windows Me
4.90.3000
September 2000
6
Windows XP
NT 5.1.2600
October 2001
8
Windows XP 64-bit Edition 2003
NT 5.2.3790
March 2003
6
Windows Server 2003
NT 5.2.3790
April 2003
8
Windows XP Professional x64 Edition
NT 5.2.3790
April 2005
8
Windows Fundamentals for Legacy PCs
NT 5.1.2600
July 2006
-
Windows Vista
NT 6.0.6000
November 2006 (volume licensing)/January 2007 (retail)
8
Windows Home Server
NT 5.2.4500
July 2007
-
Windows Server 2008
NT 6.0.6001
February 2008
8
Windows 7 (codenamed Blackcomb, then Vienna)
NT 7.0
2010 (planned)
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Navigation around the computer is easier than ever, because which made single clicking to open files and the addition of Browse buttons in every window.
Multiple monitors with a single computer, dramatically increases the size of your workspace.
Installing new hardware is easy because Windows supports the Universal Serial Bus (USB) standard, which allows users plug in new hardware and use it immediately-without restarting the computer.
Windows also helps to use digital cameras and other digital imaging devices.
More Reliable
Windows supports Online Web site for answers to common questions and help to keep the copy of Windows up-to-date.
Windows tools help in regular testing of hard disk and check the system files-and even automatically fix some problems.
The troubleshooters and the Dr. Watson diagnostic tool also help to solve computer problems.
Faster
By the use of Maintenance wizard, the speed and efficiency of the computer is easily improved.
The power management feature allows newer computers to go into hibernation mode and awaken instantly, instead of requiring shutting down and restarting the computer.
FAT32 file system provides the usage to store files more efficiently and save the hard disk.
The speed system performance which makes Windows 98 more stable and reliable which includes:
Preemptive multitasking and multithreading support. This allows multiple applications and system tasks to run well concurrently.
32-bit device drivers for all system components, ensuring better resource management.
True Web Integration
Windows makes the accessing speed of WWW more easily and faster than ever. The Internet Connection Wizard makes connecting to the Web simple.
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Using the Web-Style Active Desktop, we can view Pages in any window and we can even make our own favorite Web page as the desktop wallpaper.
Through Microsoft Outlooks Express, we send e-mail and post messages to Internet newsgroups.
By using Microsoft Net Meetings, we can collaborate on documents and hold conferences over the Internet.
Windows Media Player plays live “streaming” media over the Internet.
More Entertaining
Windows supports DVD, digital audio, and VRML, so that we can play high-quality digital movies and audio on the computer with full effect of web pages that use virtual reality features.
We can also watch television broadcasts and check TV program listings by using Microsoft Web TV for windows.
Applying a theme can change the look and sound of the desktop. Several themes are included with Windows.
Each desktop theme includes unique Wallpaper, screen savers, 3-D icons, sounds, fonts, color schemes and mouse pointer.
More on Windows Windows supports the new Win32 Driver Model (WDM). WDM is a unified driver model that will allow developers to write drivers that work on both Windows and Windows NT 5.0. This is possible because Microsoft added selected NT Kernel services into Windows via a virtual device driver (ntkern.vxd). This allows Windows to maintain full support for legacy device drivers while adding support for new WDM drivers. The 32-bit kernel in Windows provides improved memory management and process scheduling, improved system-wide robustness, and better cleanup after an application closes or fails.
2.9.3.3 RESOURCES INCLUDED WITH WINDOWS The additional Microsoft resources are:
Support Online Web Site: This interactive site does the work like gathering resources likely to solve the problem, such as technical articles from the Microsoft Knowledge Base, troubleshooting tools, patches can be download, drivers and so on. The
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INFORMATION TECHNOLOGY connection to Support Online is done by clicking the Web Help button in Windows help or by connecting to: http://support.microsoft.com/support ď ł
Windows Update Web Site: Windows will also ship with a hyperlink on the Start menu that takes users directly to a new Windows Update Web Site. Registered users who visit the site can download the latest Windows drivers and operating system files there, ensuring that their copy of Windows stays up to date. The Web site launches software that automatically scans each system to determine what it needs, and then prompts users to download the appropriate updates. Network administrators who don't want employees updating their own systems can remove this link to the site.
ď ł
Hardware Compatibility List: The most sweeping change in Windows is the vast support for new hardware. This built-in support may not become obvious until next year, when many of the hundreds of new devices supported by Windows reach market.
This includes many types of PC peripherals that didn't exist when Windows 95 was released, such as AGP graphics cards, DVD drives, and USB devices of every class. Windows will also support yet-to-be-released devices that will connect through an IEEE 1394 high-speed bus. Finally, the new operating system will provide users with the latest drivers for many of their existing cards and peripherals.
2.9.3.4 WINDOWS HELP
Windows help is your principal source of information about windows. Helps, provides with the links to the online version of the Windows, the online tutorial, the troubleshooters, the Read me files, and the Web-based resources. Importantly, help provides how to perform a wide variety of tasks - from setting up a printer to connecting to the Internet and it also locates topics, the Index tab to look up keywords, and the search tab to search for text.
2.9.3.5 TROUBLESHOOTERS
Windows includes a wide range of helpful troubleshooters that assist the users with many common computer problems. The troubleshooters are available through the
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INFORMATION TECHNOLOGY contents tab in Windows Help, and theyâ&#x20AC;&#x2122;re constantly updated and supplemented on the Support Online Web site.
2.9.4 LINUX
Linux is the name usually given to any Unix-like computer operating system that uses the Linux kernel. Linux is one of the most prominent examples of free software and open source development: typically all underlying source code can be freely modified, used, and redistributed by anyone. The name "Linux" comes from the Linux kernel, started in 1991 by Linus Torvalds. The system's utilities and libraries usually come from the GNU operating system, announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative name GNU/Linux. Predominantly known for its use in servers, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat, and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, supercomputers, , and embedded devices such as E-book readers, video game systems (PlayStation 2, PlayStation 3 and XBox), mobile phones and routers.
2.9.4.1 History of Linux The Unix operating system was conceived and implemented in the 1960s and first released in 1970. Its wide availability and portability meant that it was widely adopted, copied and modified by academic institutions and businesses, with its design being influential on authors of other systems.
The GNU Project, started in 1984, had the goal of creating a "complete Unixcompatible software system" made entirely of free software. In 1985, Richard Stallman created the Free Software Foundation and developed the GNU General Public License (GNU GPL). Many of the programs required in an OS (such as libraries, compilers, text editors, a Unix shell, and a windowing system) were completed by the early 1990s, although low level elements such as device drivers, daemons, and the kernel were stalled and incomplete. Linus Torvalds has said that if the GNU kernel had been available at the time (1991), he would not have decided to write his own.
MINIX, a Unix-like system intended for academic use, was released by Andrew S. Tanenbaum in 1987. The source code for MINIX 1.0 was printed in his book Operating Systems: Design and Implementation. While easily available, modification and redistribution
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INFORMATION TECHNOLOGY were restricted (though that is not the case today). The code was covered by the copyrights of the textbook, published by Prentice Hall. In addition, MINIX's 16-bit design was not well adapted to the 32-bit design of the increasingly cheap and popular Intel 386 architecture for personal computers.
In 1991, Torvalds began to work on a non-commercial replacement for MINIX while he was attending the University of Helsinki. This eventually became the Linux kernel.
In 1992, Tanenbaum posted an article on Usenet claiming Linux was obsolete. In the article, he criticized the operating system as being monolithic in design and being tied closely to the x86 architecture and thus not portable, which he described as "a fundamental error". Tanenbaum suggested that those who wanted a modern operating system should look into one based on the microkernel model. The posting elicited the response of Torvalds, which resulted in a well known debate over the microkernel and monolithic kernel designs.
Linux was dependent on the MINIX user space at first. With code from the GNU system freely available, it was advantageous if this could be used with the fledgling OS. Code licensed under the GNU GPL can be used in other projects, so long as they also are released under the same or a compatible license. In order to make the Linux kernel compatible with the components from the GNU Project, Torvalds initiated a switch from his original license (which prohibited commercial redistribution) to the GNU GPL. Linux and GNU developers worked to integrate GNU components with Linux to make a fully functional and free operating system.
Commercial and popular uptake
Today Linux is used in numerous domains, from embedded systems to supercomputers, and has secured a place in web server installations with the popular LAMP application stack. Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components. These third-party components comprise a vast body of work and may include both kernel modules and user applications and libraries. Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.
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Design
Linux is a modular Unix-like operating system. It derives much of its basic design from principles established in Unix during the 1970s and 1980s. Linux uses a monolithic kernel, the Linux kernel, which handles process control, networking, and peripheral and file system access. Device drivers are integrated directly with the kernel. Much of Linux's higher-level functionality is provided by separate projects which interface with the kernel. The GNU userland is an important part of most Linux systems, providing the shell and Unix tools which carry out many basic operating system tasks. On top of the kernel, these tools form a Linux system with a graphical user interface that can be used, usually running in the X Window System. Linux can be controlled by one or more of a text-based command line interface (CLI), graphical user interface (GUI) (usually the default for desktop), or through controls on the device itself (common on embedded machines).
On desktop machines, KDE, GNOME and Xfce are the most popular user interfaces,
[19]
though a variety of other user interfaces exist. Most popular user interfaces run
on top of the X Window System (X), which provides network transparency, enabling a graphical application running on one machine to be displayed and controlled from another.
Other GUIs include X window managers such as FVWM, Enlightenment, Fluxbox and Window Maker. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X window system.
A Linux system usually provides a command line interface of some sort through a shell, which is the traditional way of interacting with a Unix system. A Linux distribution specialized for servers may use the CLI as its only interface. A â&#x20AC;&#x153;headless systemâ&#x20AC;? run without even a monitor can be controlled by the command line via a protocol such as SSH or telnet.
Most low-level Linux components, including the GNU Userland, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication. A graphical terminal emulator program is often used to access the CLI from a Linux desktop.
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INFORMATION TECHNOLOGY A summarized history of Unix-like operating systems showing Linux's origins. Note that despite similar architectural designs and concepts being shared as part of the POSIX standard, Linux does not share any non-free source code with the original Unix or Minix. The primary difference between Linux and many other popular contemporary operating systems is that the Linux kernel and other components are free and open source software. Linux is not the only such operating system, although it is the best-known and most widely used. Some free and open source software licences are based on the principle of copyleft, a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU GPL, is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU project. Linux systems adhere to POSIX, SUS, ISO and ANSI standards where possible. To date, however, only the Linux-FT distribution has been POSIX.1 certified. Free software projects, although developed in a collaborative fashion, are often produced independently of each other. However, because the software licenses explicitly permit redistribution there is a basis for larger scale projects that collect the software produced by stand-alone projects and make this software available together in a Linux distribution. A Linux distribution, commonly called a â&#x20AC;&#x153;distroâ&#x20AC;?, is a project that manages a remote collection of Linux-based software, and facilitates installation of a Linux operating system. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. They include system software and application software in the form of packages, and distribution-specific software for initial system installation and configuration as well as later package upgrades and installs. A distribution is responsible for the default configuration of installed Linux systems, system security, and more generally integration of the different software packages into a coherent whole. 2.10 CONCLUSION The Information Technology primarily depends on computer and their accessories. Every development in computer technology, either in hardware or in software will have a high impact in the development of Information Technology. Similarly the development Communication Technology will also have the substantial impact in information technology. These two things together, today we are terming it as ICT implications.
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INFORMATION TECHNOLOGY UNIT QUESTIONS 1. 2. 3. 4. 5. 6. 7. 8.
Discuss on different generations of Computers Write different Input and Output devices used in computers What is software and discuss various types of software What are the functions of operating system and the types of OS Briefly discuss MS DOS Discuss Unix operating system What are the advantages of Windows over other OS Describe Linux OS
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UNIT III COMPUTER NETWORKING 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10
Objectives Networking – Need, Purpose, Type LAN MAN WAN Wireless LAN Network Topologies Basic Elements in Networking Network Cabling Network Operating System
3.1 OBJECTIVES
After studying this lesson, you should be able to
Understand the concept of Computer Networking
Describe the various Type of Network
What is Operating System
Different types of Networking Topologies
Network Servers
3.2 NETWORKING
A computer network is the linking together of CPUs and terminals via a communication system. A network allows users at different locations to share files, devices and programs. Many terminals may share the resources of one CPU, or multiple CPUs may be linked together. Terminals and CPUs may be geographically dispersed or situated within the physical constraints of a single office or building. The computer network means an interconnected collection of autonomous computers. Two computers are said to be interconnected if they are able to exchange information. With a network, users must log onto one machine, submit jobs remotely, move files around explicitly. It is nothing but an interconnection of computer systems and/or peripheral devices with carriers and data communications devices for the purpose of exchanging data and information
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Uses of computer networks
The main uses of computer network are
Resources sharing
High reliability
Saving money
Communication medium
Access to remote information
Person to person communication
Interactive transfer of information
Components of network
The different components of networks are
S.No.
Components
Description
1.
Signals
Analog signals, Digital signals
2.
Communication Media
Bounded media, Un-bounded media
3.
Communication Channels
Simplex, Half-duplex, Full-duplex
4.
Topology
Bus, Ring, Hierarchical, Star
Types of network
Network can be divided into following types
Local Area Networks – LAN
Metropolitan Area Networks – MAN
Wide Area Networks – WAN
Wireless Networks
Internet
3.3 LOCAL AREA NETWORKS (LAN)
A Local Area Networks (LAN) is two or more computers directly linked within a small well defined area such as room, building, or a campus. The main benefit of a LAN is the
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reduction of hardware and software costs because users can share several computers, peripheral devices such as laser printers, colour-printers, Scanners, Softwares. Another benefit is that the users can share the same data.
A LAN is a geographically small network of computers and supporting components used by a group or department to share related software and hardware resources.
Some LANs specifically require all the computers to be of a certain brand, while others allow a variety of brands to be connected. The number of computers in LAN varies widely from small LANs that connect two to twenty five computers, to large LANs that may connect more than 10,000 computers.
LAN must get the data to its destination, transmit the data correctly, and prevent unauthorized users from gaining access to that data.
The length of the cable connecting to computer through a LAN also varies. Most of the LANs permit cables of about one thousand feet, but some permit cables of several miles to be used. The speed of data transfer ranges from several thousand bits per second to 10 million bits per second.
A LAN generally consists of the following:
Two or more computers
Software to control the operation of the computers
Peripheral devices such as modems, printers, plotters
Coaxial or fiber optic cables are usually used to connect the computers and other devices
Ports and hubs for connecting computers
3.4 METROPOLITAN AREA NETWORK (MAN)
A Metropolitan Area Network (MAN) is a network that is larger than a LAN. It is called metropolitan since it normally covers the area of a city.
Different hardware and
transmission media are often used in MANs because they must efficiently cover these
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3.5 WIDE-AREA NETWORKS (WAN)
A Wide-Area Network (WAN) is two or more geographically dispersed computers, linked by communication facilities such as telecommunication or microwave relays. In other words, one of the most significant aspects of a wide-area network while comparing it with the freedom of a local-area nework, is the involvement of a public telecommunications authority. WAN is usually limited to use by the large organizations and government agencies due to high costs involved in building and maintaining them.
A special designation has also been given to two specific WAN categories:
Enterprise : An enterprise network connects all LANs of a single organization. The term is normally used for networks connecting extremely large organizations, or for those that cross regional boundaries.
Global : A global network is one that spans the earth. While global networks may not cover the entire globe, they cross multiple national boundaries and may include the networks of several organizations.
3.6 WIRELESS LANS
Not all networks are connected with cabling; some networks are wireless. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations and the file server or hubs. Each workstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed between transceivers as if they were physically connected. For longer distance, wireless communications can also take place through cellular telephone technology, microwave transmission, or by satellite.
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INFORMATION TECHNOLOGY Wireless networks are great for allowing laptop computers or remote computers to connect to the LAN. Wireless networks are also beneficial in older buildings where it may be difficult or impossible to install cables.
The two most common types of infrared communications used in schools are line-ofsight and scattered broadcast. Line-of-sight communication means that there must be an unblocked direct line between the workstation and the transceiver. If a person walks within the line-of-sight while there is a transmission, the information would need to be sent again. This kind of obstruction can slow down the wireless network. Scattered infrared communication is a broadcast of infrared transmissions sent out in multiple directions that bounces off walls and ceilings until it eventually hits the receiver. Networking communications with laser are virtually the same as line-of-sight infrared networks.
Wireless LANs have several disadvantages. They are very expensive, provide poor security, and are susceptible to interference from lights and electronic devices. They are also slower than LANs using cabling.
3.7 NETWORK TOPOLOGY
The arrangement of computer resources, remote devices, communication facilities is known as network topology.
The different types of topologies are
Bus topology
Ring topology
Star topology
Mesh topology
Hierarchical topology
3.7.1 BUS TOPOLOGY
In bus topology, each computer is connected to a single communication cable via an interface and every computer can directly communicate with every other computer or device in the network. This topology is commonly used along with the local area networks.
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Advantages of Bus topology
The advantages of bus topology are
Short cable length and simple wiring layout: Because there is a single common data path connecting all nodes, the bus topology allows a very short cable length to be used. This decreased the installation cost, and also leads to a simple, easy to maintain, wiring layout.
Easy to extend: Additional nodes can be connected to an existing bus network at any point along its length. More extensive additions can be achieved by adding extra segments such as amplifiers, hubs, repeaters.
Simple architecture: It is simple, reliable in very small networks, easy to use and easy to understand. It requires the least amount of cable to connect the computers together. There is a single cable through which all data passes and to which all nodes are connected.
3.7.2 RING TOPOLOGY
This layout is similar to the linear bus, except that the nodes are connected in a circle using cable segments. In this layout, each node is physically connected to only two others. Each node passes information along to the next, until it arrives at its intended destination. Since each computer re-transmits what it receives, a ring is an active network and is not subject to the signal loss problems which a bus topology experiences. termination because there is no end to the ring.
There is no
Performance is faster on this system
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Advantages of the Ring Topology
Short cable length : The amount of cabling involved in a ring topology is comparable to that of a bus and is small relative to that of a star. This means that less connections will be needed, which will in turn increase network reliability.
Suitable for optical fibers : Optical fibres offer the possibility of very high speed transmission. Because trffic on a ring travels in one direction. It is easy to use optical fibres as a medium fo transmission.
Disadvantages of the Ring topology
Node failure causes network failure
Difficult to diagnose faults
3.7.3 STAR TOPOLOGY
Each computer on a star network communicates with a central hub that re-sends the message either to all the computers or only to the destination computer. The star topology can be classified in to two types such as: -
Broadcast star network
-
Switched star network
The hub in a broadcast star network can be active or passive. An active hub regenerates the electrical signal and sends it to all the computers connected to it. This type of hub is often called a multi port repeater. Active hubs and switches require electrical power to run. A passive hub merely acts as a connector point and does not amplify or regenerate the signal. Passive hubs do not require electrical power to run.
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Advantages of Star Topology
Ease of service
Centralised control/problem diagnosis
One device per connection
Simple access protocols
Disadvantages of the Star Topology
Long cable length
Difficult to expand
Central node dependency
3.7.4 HIERARCHICAL TOPOLOGY
Several computers or devices are linked in a hierarchical fashion. The hierarchical topology is also called Tree topology. This type of distribution system is commonly used in the organization where headquarters communicate with regional offices and regional offices communicate with district offices and so on.
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INFORMATION TECHNOLOGY
Advantages of Hierarchical Topology
Easy to extend
Fault isolation
Disadvantages of the Hierarchical Topology
Dependent on the root
3.7.5 MESH TOPOLOGY
A mesh topology has point-to-point connections between every device in the network. Each device requires an interface for every other device on the network. Necessity for this type of topology arises only when each station sends messages frequently to all other stations.
Advantages of Mesh topology
Ease of installation
Ease of troubleshooting
Disadvantages of Mesh topology
Units affected by media failure.
3.8 BASIC ELEMENTS IN NETWORKING
All networks require the following three elements:
1. Network Services : At least two individuals who have something to share 2. Transmission Media : A method or pathway for contacting each other 3. Protocols: Rules so that two or more individual can communicate
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INFORMATION TECHNOLOGY 1. Network Services
Network services are provided by numerous combinations of computer hardware and software. Depending upon the task, network services require data, input/output resources and processing power to accomplish their goals.
The three types of service providers and requestors are as follows:
Servers : Servers are only allowed to provide services
Clients : Clients are only allowed to request services from others.
Peers
: Peers may do both concurrently.
Computer networks are often classified as one of the following types
Peer-to-Pee network
Server-Centric network
Peer-to-peer networks allow any entry to both request and provide network services. Peer-to-peer network software is designed so that peers perform the same or similar functions for each other.
A server-Centric network involves strictly defined roles. A Server-Centric network places restrictions upon which entity may make requests or service them. In the current trend, the most popular personal computer networks are Server-Centric networks
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3.9 Network Cabling
Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Understanding the characteristics of different types of cable and how they relate to other aspects of a network is necessary for the development of a successful network. The following sections discuss the types of cables used in networks and other related topics.
Unshielded Twisted Pair (UTP) Cable
Shielded Twisted Pair (STP) Cable
Coaxial Cable
Fiber Optic Cable
Wireless LANs
Cable Installation Guides
3.9.1 Unshielded Twisted Pair (UTP) Cable
Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks (See fig. 3.9.1).
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Fig.3.9.1. Unshielded twisted pair The quality of UTP may vary from telephone-grade wire to extremely highspeed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated five categories of wire.
Categories of Unshielded Twisted Pair Specification
Cable Type
Maximum length
10BaseT
Unshielded Twisted Pair
100 meters
10Base2
Thin Coaxial
185 meters
10Base5
Thick Coaxial
500 meters
10BaseF
Fiber Optic
2000 meters
100BaseT
Unshielded Twisted Pair
100 meters
100BaseTX
Unshielded Twisted Pair
220 meters
Buy the best cable you can afford; most schools purchase Category 3 or Category 5. If you are designing a 10 Mbps Ethernet network and are considering the cost savings of buying Category 3 wire instead of Category 5, remember that the Category 5 cable will provide more "room to grow" as transmission technologies increase. Both Category 3 and Category 5 UTP have a maximum segment length of 100 meters. In Florida, Category 5 cable is required for retrofit grants. 10BaseT refers
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3.9.1.2 Unshielded Twisted Pair Connector
The standard connector for unshielded twisted pair cabling is an RJ-45 connector. This is a plastic connector that looks like a large telephone-style connector (See fig. 2). A slot allows the RJ-45 to be inserted only one way. RJ stands for Registered Jack, implying that the connector follows a standard borrowed from the telephone industry. This standard designates which wire goes with each pin inside the connector.
Fig. 3.9.2. RJ-45 connector
3.9.2 Shielded Twisted Pair (STP) Cable
A disadvantage of UTP is that it may be susceptible to radio and electrical frequency interference. Shielded twisted pair (STP) is suitable for environments with electrical interference; however, the extra shielding can make the cables quite bulky. Shielded twisted pair is often used on networks using Token Ring topology.
3.9.3 Coaxial Cable
Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield (See fig. 3.9.3). The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.
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Fig. 3.9.3. Coaxial cable Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial cabling are thick coaxial and thin coaxial. Thin coaxial cable is also referred to as thinnet. 10Base2 refers to the specifications for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment length being 200 meters. In actual fact the maximum segment length is 185 meters. Thin coaxial cable is popular in school networks, especially linear bus networks. Thick coaxial cable is also referred to as thicknet. 10Base5 refers to the specifications for thick coaxial cable carrying Ethernet signals. The 5 refers to the maximum segment length being 500 meters. Thick coaxial cable has an extra protective plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a great choice when running longer lengths in a linear bus network. One disadvantage of thick coaxial is that it does not bend easily and is difficult to install.
3.9.3.1 Coaxial Cable Connectors
The most common type of connector used with coaxial cables is the BayoneNeill-Concelman (BNC) connector (See fig. 3.9.4). Different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator. Connectors on the cable are the weakest points in any network. To help avoid problems with your network, always use the BNC connectors that crimp, rather than screw, onto the cable.
Fig. 3.9.4. BNC connector
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i.
Fiber Optic Cable Fiber optic cabling consists of a center glass core surrounded by several
layers of protective materials (See fig. 3.9.5). It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting. Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of fiber optic cabling is comparable to copper cabling; however, it is more difficult to install and modify. 10BaseF refers to the specifications for fiber optic cable carrying Ethernet signals.
Fig.3.9.5. Fiber optic cable
Facts about fiber optic cables:
Outer insulating jacket is made of Teflon or PVC.
Kevlar fiber helps to strengthen the cable and prevent breakage.
A plastic coating is used to cushion the fiber center.
Center (core) is made of glass or plastic fibers.
3.9.4.1 Fiber Optic Connector
The most common connector used with fiber optic cable is an ST connector. It is barrel shaped, similar to a BNC connector. A newer connector, the SC, is becoming more popular. It has a squared face and is easier to connect in a confined space.
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3.10 Network Operating System
Unlike operating systems, such as DOS and Windows95, that are designed for single users to control one computer, network operating systems (NOS) coordinate the activities of multiple computers across a network. The network operating system acts as a director to keep the network running smoothly.
3.10.1 Examples of network operating systems
The following list includes some of the more popular peer-to-peer and client/server network operating systems.
AppleShare
LANtastic
Microsoft Windows for Workgroups
Microsoft Windows NT Server
Novell Netware
UNIT QUESTIONS 9. 10. 11. 12. 13.
What is Network? Discuss the purpose of Networking. Give the different types of networking topologies Briefly Discuss on Bus, Ring and Star Topologies with their merits and demerits Give the basic elements in Networking and explain the use of it.
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UNIT IV NETWORK TECHNOLOGY 4.1
Objectives
4.2
Network Protocol
4.3
Hyper Text
4.4
Hyper Media
4.5
Multi Media
4.6
ISDN
4.7
OSI
4.8
Network Accessories
4.9
References
4.1 OBJECTIVES After studying this lesson, you should be able to
Describe the Network Protocol
Differentiate different types of protocol
Define Hyper Text, Hyper Media and Multimedia
Different types of types of Network Accessories
4.2 NETWORK PROTOCOL
Networking evolved from the basic principle of moving data from one computer to another. The first method involved coping data to a storage media such as a floppy disk and then taking that storage media to another computer and copying the data.
This was
charmingly referred to as sneaker-net. As more efficient means were discovered – namely, electricity on a copper wire – networking became more popular. However, there were no standards in place.
This meant that one network manufacturer implemented a different
means of data transfer than another. If one had an IBM network, then they must have only IBM network device. In order to have a uniform pattern among computer network there evolved a protocol.
4.2.1 WHAT IS PROTOCOLS
It is asset of rules for sending information over a network. Protocols can include rules concerning any or all of the following functions.
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Data transmission mechanisms
Communication session initialization and termination
Addressing and routing
Authentication and verification
Encryption and compression
Error correction
Protocols are usually classified according to the layer they correspond to in the Open Systems Interconnection (OSI) reference model for networking. The seven layers of the protocol are as follows:
Layer 7
Application
Layer 6
Presentation
Layer 5
Session
Layer 4
Transport
Layer 3
Network
Layer 2
Data Link
Layer 1
Physical
Types of protocols include the following:
Data-link protocols: Govern the framing of data, physical addressing of network nodes, and media access control methods.
For local area networks (LANs), these primarily include Ethernet, Token Ring, and Fiber distributed Data Interface (FDDI).
For wide area networks (WANs), they include Point-to- Point Protocol (PPP), High-level Data Link Control (HDLC), frame relay, Asynchronous Transfer Mode (ATM), and X.25.
Network protocols: Handle link services and are responsible for addressing, routing, and error checking.
Eg: NetBEUI, Internet work Packet Exchange (IPX), NW Link, and Internet Protocol (IP).
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Transport protocols: Enable the establishment of sessions and ensure reliable flow of data.
Eg: NetBEUI, Sequenced Packed Exchange (SPX), NWlink, and Transmission Control Protocol (TCP)
Application layer protocols: Enable applications to access network services. Eg.: Hypertext Transfer Protocol (HTTP) File Transfer Protocol (FTP) Telnet, Simple Mail Transfer Protocol (SMTP) Simple Network Management Protocol (SNMP) Network News Transfer Protocol (NNTP) X.400, X.500 Server Message Block (SMB) Network File System (NFS)
Some protocols have been developed by specific vendors and then accepted as de facto standards by the industry, while others initially formulated by independent standards bodies and then accepted and implemented by vendors. The most widely implemented protocols are those relating to TCP/IP and the Internet.
4.2.1.1 Hyper Text Transfer Protocol (HTTP) The Hypertext Transfer Protocol (HTTP) is an application –level protocol with the lightness and speed necessary for distributed, collaborative, hypermedia information systems. HTTP has been in use by the World Wide Web global information initiative since 1990.
Practical information systems require more functionality than simple retrieval, including search, front-end update and annotation.
HTTP allows an open-ended set of
methods to be used to indicate the purpose of a request.
It builds on the discipline of
reference provided by the Uniform Resource Identifier (URI), as a location (URL) or name (URN) for indicating the resource on which a method is to be applied. Messages are passed in a format similar to that used by Internet Mail and the Multipurpose Internet Mail Extensions (MIME).
HTTP is also used as a generic protocol for communication between user agents and proxies/gateways to other Internet protocols, such as SMTP, NNTP, FTP, Gopher and
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WAIS, allowing basic hypermedia access to resources available from diverse applications and simplifying the implementation of user agents.
4.2.1.2 TCP/IP
TCP/IP stands for Transmission Control Protocol/Internet Protocol.
The TCP/IP
reference model is a set of protocols that allow communication across multiple diverse networks.
TCP/IP is normally considered to a four layer system.
Layers of TCP/IP
Application layer, Transport layer, Internet layer, Host to network layer. Host to network layer is also called physical and data link layer. The application layer in TCP/IP can be equated with the combination of session, presentation, application layer of the OSI reference model. TCP/IP defines two protocol at transport layer: TCP and UDP (User Datagram Protocol)
4.3
HYPER TEXT
Hyper Text is used for branching and responding text, but the corresponding word "hypermedia," meaning complexes of branching and responding graphics, movies and sound - as well as text - is much less used. Instead they use the strange term "interactive multimedia" - four syllables longer, and not expressing the idea that it extends hypertext. Nelson, Literary Machines 1992
4.3.1 Types and uses of hypertext Hypertext documents can either be static (prepared and stored in advance) or dynamic (continually changing in response to user input). Static hypertext can be used to cross-reference collections of data in documents, software applications, or books on CDs. A well-constructed system can also incorporate other user-interface conventions, such as menus and command lines. Hypertext can develop very complex and dynamic systems of linking and cross-referencing. The most famous implementation of hypertext is the World Wide Web.
4.3.2 History of hypertext
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INFORMATION TECHNOLOGY 4.3.2.1 Early precursors to hypertext Recorders of information have long looked for ways to categorize and compile it. Early on, experiments existed with various methods for arranging layers of annotations around a document. The most famous example of this is the Talmud. Various other reference works (for example dictionaries, encyclopedias, etc.) also developed a precursor to hypertext, consisting of setting certain words in small capital letters, indicating that an entry existed for that term within the same reference work. Sometimes the term would be preceded by a pointing hand dingbat.
Later, several scholars entered the scene who believed that humanity was drowning in information, causing foolish decisions and duplicating efforts among scientists. These scholars proposed or developed proto-hypertext systems predating electronic computer technology. For example, in the early 20th century, two visionaries attacked the crossreferencing problem through proposals based on labor-intensive, brute force methods. Paul Otlet proposed a proto-hypertext concept based on his monographic principle, in which all documents would be decomposed down to unique phrases stored on index cards. In the 1930s, H.G. Wells proposed the creation of a World Brain. Michael Buckland summarized the very advanced pre-World War II development of microfilm based on rapid retrieval devices, specifically the microfilm based workstation proposed by Leonard Townsend in 1938 and the microfilm and photoelectronic based selector, patented by Emmanuel Goldberg in 1931. Buckland concluded: "The pre-war information retrieval specialists of continental Europe, the 'documentalists,' largely disregarded by post-war information retrieval specialists, had ideas that were considerably more advanced than is now generally realized." But, like the manual index card model, these microfilm devices provided rapid retrieval based on pre-coded indices and classification schemes published as part of the microfilm record without including the link model which distinguishes the modern concept of hypertext from content or category based information retrieval.
4.3.2.2 The Memex
All major histories of what we now call hypertext start in 1945, when Vannevar Bush wrote an article in The Atlantic Monthly called "As We May Think," about a futuristic device he
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INFORMATION TECHNOLOGY called a Memex. He described the device as a mechanical desk linked to an extensive archive of microfilms, able to display books, writings, or any document from a library. The Memex would also be able to create 'trails' of linked and branching sets of pages, combining pages from the published microfilm library with personal annotations or additions captured on a microfilm recorder. Bush's vision was based on extensions of 1945 technology - microfilm recording and retrieval in this case. However, the modern story of hypertext starts with the Memex because "As We May Think" directly influenced and inspired the two American men generally credited with the invention of hypertext, Ted Nelson and Douglas Engelbart.
4.3.2.3 The invention of hypertext
Ted Nelson coined the words "hypertext" and "hypermedia" in 1965 and worked with Andries van Dam to develop the Hypertext Editing System in 1968 at Brown University. Engelbart had begun working on his NLS system in 1962 at Stanford Research Institute, although delays in obtaining funding, personnel, and equipment meant that its key features were not completed until 1968. In December of that year, Engelbart demonstrated a hypertext interface to the public for the first time, in what has come to be known as "The Mother of All Demos".
Funding for NLS slowed after 1974. Influential work in the following decade included NoteCards at Xerox PARC and ZOG at Carnegie Mellon. ZOG started in 1972 as an artificial intelligence research project under the supervision of Allen Newell, and pioneered the "frame" or "card" model of hypertext. ZOG was deployed in 1982 on the U.S.S. Carl Vinson and later commercialized as Knowledge Management System. Two other influential hypertext projects from the early 1980s were Ben Shneiderman's The Interactive Encyclopedia System (TIES) at the University of Maryland (1983) and Intermedia at Brown University (1984).
4.3.2.4 Applications
The first hypermedia application was the Aspen Movie Map in 1977. In 1980, Tim Berners-Lee created ENQUIRE, an early hypertext database system somewhat like a wiki. The early 1980s also saw a number of experimental hypertext and hypermedia programs,
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INFORMATION TECHNOLOGY many of whose features and terminology were later integrated into the Web. Guide was the first hypertext system for personal computers.
In August 1987, Apple Computer released HyperCard for the Macintosh line at the MacWorld convention. Its impact, combined with interest in Peter J. Brown's GUIDE (marketed by OWL and released earlier that year) and Brown University's Intermedia, led to broad interest in and enthusiasm for hypertext and new media. The first ACM Hypertext academic conference took place in November 1987, in Chapel Hill NC. Meanwhile Nelson, who had been working on and advocating his Xanadu system for over two decades, along with the commercial success of HyperCard, stirred Autodesk to invest in Nelson's revolutionary ideas. The project continued at Autodesk for four years, but no product was released.
4.3.2.5 Hypertext and the World Wide Web
In the late 1980s, Berners-Lee, then a scientist at CERN, invented the World Wide Web to meet the demand for automatic information-sharing among scientists working in different universities and institutes all over the world. In 1992, Lynx was born as an early Internet web browser. Its ability to provide hypertext links within documents that could reach into documents anywhere on the Internet began the creation of the web on the Internet. Early in 1993, the National Center for Supercomputing Applications (NCSA) at the University of Illinois released the first version of their Mosaic web browser to supplement the two existing web browsers: one that ran only on NeXTSTEP and one that was only minimally user-friendly. Because it could display and link graphics as well as text, Mosaic quickly became the replacement for Lynx. Mosaic ran in the X Window System environment, which was then popular in the research community, and offered usable window-based interactions. It allowed images
[2]
as well as text to anchor hypertext links. It also incorporated other
protocols intended to coordinate information across the Internet, such as Gopher. After the release of web browsers for both the PC and Macintosh environments, traffic on the World Wide Web quickly exploded from only 500 known web servers in 1993 to over 10,000 in 1994. Thus, all earlier hypertext systems were overshadowed by the success of the web,
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INFORMATION TECHNOLOGY even though it originally lacked many features of those earlier systems, such as an easy way to edit what you were reading, typed links, backlinks, transclusion, and source tracking.
In 1995, Ward Cunningham made the first wiki available, which built on the web by adding easy editing, and (within a single wiki) backlinks and limited source tracking. Wikis continue to be a medium where features are implemented, which were developed or imagined in the early explorations of hypertext.
4.3.2.6 Hyper text Implementations
Besides the already mentioned Project Xanadu, Hypertext Editing System, NLS, HyperCard, and World Wide Web, there are other noteworthy early implementations of hypertext, with different feature sets:
FRESS — A 1970s multi-user successor to the Hypertext Editing System.
Electronic Document System — An early 1980s text and graphic editor for interactive hypertexts such as equipment repair manuals and computer-aided instruction.
Information Presentation Facility — Used to display online help in IBM operating systems.
Intermedia — A mid-1980s program for group web-authoring and information sharing.
Storyspace — A mid-1980s program for hypertext narrative.
Texinfo — The GNU help system.
XML with the XLink extension — A newer hypertext markup language that extends and expands capabilities introduced by HTML.
MediaWiki, the system that powers Wikipedia, and other wiki implementations — Relatively recent programs aiming to compensate for the lack of integrated editors in most Web browsers.
Adobe's Portable Document Format — A widely used publication format for electronic documents including links.
Windows Help
PaperKiller - A document editor specifically designed for hypertext. Started in 1996 as IPer (educational project for ED-Media 1997).
Amigaguide - released on Amiga Workbench 1990.
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INFORMATION TECHNOLOGY 4.4
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HYPER MEDIA
[1]
Hypermedia is a term first used in a 1965 article by Ted Nelson.
It is used as a
logical extension of the term hypertext in which graphics, audio, video, plain text and hyperlinks intertwine to create a generally non-linear medium of information. This contrasts with the broader term multimedia, which may be used to describe non-interactive linear presentations as well as hypermedia. Hypermedia should not be confused with hypergraphics or super-writing which is not a related subject. It is also related to the field of Electronic literature. The World Wide Web is a classic example of hypermedia, whereas a non-interactive cinema presentation is an example of standard multimedia due to the absence of hyperlinks. The first hypermedia work was, arguably, the Aspen Movie Map. Atkinson's Hypercard popularized hypermedia writing, while a variety of literary hypertext and hypertext works, fiction and nonfiction, demonstrated the promise of links. . Most modern hypermedia is delivered via electronic pages from a variety of systems including Media players, web browsers, and stand-alone applications. Audio hypermedia is emerging with voice command devices and voice browsing. 4.4.1 Hypermedia development tools Hypermedia may be developed a number of ways. Any programming tool can be used to write programs that link data from internal variables and nodes for external data files. Multimedia development software such as Adobe Flash, Director, Authorware, and MatchWare Mediator may be used to create stand-alone hypermedia applications, with emphasis on entertainment content. Some database software such as Visual FoxPro and FileMaker Developer may be used to develop stand-alone hypermedia applications, with emphasis on educational and business content management. Hypermedia applications may be developed on embedded devices for the mobile and the Digital signage industries using the Scalable Vector Graphics (SVG) specification from W3C (World Wide Web Consortium). Software applications such as Ikivo Animator and Inkscape simplify the development of Hypermedia content based on SVG. Embedded devices such as iPhone natively support SVG specifications and may be used to create mobile and distributed Hypermedia applications.
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INFORMATION TECHNOLOGY Hyperlinks may also be added to data files using most business software via the limited scripting and hyperlinking features built in. Documentation software such as the Microsoft Office Suite allows for hypertext links to other content within the same file, other external files, and URL links to files on external file servers. For more emphasis on graphics and page layout, hyperlinks may be added using most modern desktop publishing tools. This includes presentation programs, such as Microsoft Powerpoint, add-ons to print layout programs such as Quark Immedia, and tools to include hyperlinks in PDF documents such as Adobe InDesign for creating and Adobe Acrobat for editing. Hyper Publish is a tool specifically designed and optimized for hypermedia and hypertext management. Any HTML Editor may be used to build HTML files, accessible by any web browser. CD/DVD authoring tools such as DVD Studio Pro may be used to hyperlink the content of DVDs for DVD players or web links when the disc is played on a personal computer connected to the internet.
4.5
MULTI MEDIA
Multimedia in computer systems means, from the user point of view, using many input media (i.e. text, speech, gestures, direct manipulation) and output media (text, sound, graphics, video) in the same application.
Multimedia has grown out of a variety of media disciplines. For example, if one has the choice of picking up film clips frame-wise from video tapes, sound sequences from CDROM disks, adding a touch of animation and throwing in data or statistics scanned from OHP slides and all these controlled by personal computer is called multimedia. Multimedia is immensely useful as publishing and information distribution system.
Multimedia is media that utilizes a combination of different content forms. The term can be used as a noun (a medium with multiple content forms) or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which only utilize traditional forms of printed or hand-produced text and still graphics. In general, multimedia includes a combination of text, audio, still images, animation, video, and interactivity content forms.
Multimedia is usually recorded and played, displayed or accessed by information content processing devices, such as computerized and electronic devices, but can also be
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part of a live performance. Multimedia (as an adjective) also describes electronic media devices used to store and experience multimedia content. Multimedia is similar to traditional mixed media in fine art, but with a broader scope. The term "rich media" is synonymous for interactive multimedia. Hypermedia can be considered one particular multimedia application.
Multimedia contains a combination of content forms:
Text
Audio
Still Images
Animation
Video
Interactivity
Multimedia is the combination of two or more media.
The medias can be text,
graphics, audio and video. The medias are to be played during some well defined time interval with user interaction. Normally two medias are audio and video. i.e. sound and moving pictures. Multimedia is the integration of several media for presentation or distribution over Internet.
Multimedia Publishing includes ordering, correlating representations,
organizing (layout, order) hypermedia linking, adding interactive scripts. It uses the computer to integrate and control diverse electronic media such as computer screens, video displays, CD ROM and speech and audio synthesizer.
Further information distribution and using
includes network distribution, optical publishing, on-line use, hypermedia enhancement by users.
Before transmission of multimedia signals it is compressed then at destination the signal is recovered. While compressing the data it is necessary that no data should be lost. Many compression techniques and algorithms make multimedia transmission feasible.
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4.5.1 CATEGORIZATION OF MULTIMEDIA Multimedia may be broadly divided into linear and nonlinear categories. Linear active content progresses without any navigation control for the viewer such as a cinema presentation. Non-linear content offers user interactivity to control progress as Linear
used with a computer game or used in self-paced computer
Non-linear
based training. Non-linear content is also known as hypermedia Presentation Interactive content. Multimedia presentations can be live or recorded. A recorded presentation may allow interactivity via a navigation system. A live multimedia presentation may allow interactivity via an interaction with the presenter or performer.
4.5.2 MAJOR CHARACTERISTICS OF MULTIMEDIA Multimedia presentations may be viewed in person on stage, projected, transmitted, or played locally with a media player. A broadcast may be a live or recorded multimedia presentation. Broadcasts and recordings can be either analog or digital electronic media technology. Digital online multimedia may
Local
Online
be downloaded or streamed. Streaming multimedia may be live
Recorded
Streaming
or on-demand.
4.5.3 HISTORY OF THE TERM MULTIMEDIA
In 1965 the term Multi-media was used to describe the Exploding Plastic Inevitable, a performance that combined live rock music, cinema, experimental lighting and performance art.
In the intervening forty years the word has taken on different meanings. In the late 1970s the term was used to describe presentations consisting of multi-projector slide shows timed to an audio track. In the 1990s it took on its current meaning. In common usage the term multimedia refers to an electronically delivered combination of media including video,
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INFORMATION TECHNOLOGY still images, audio, text in such a way that can be accessed interactively.
67 [1]
Much of the
content on the web today falls within this definition as understood by millions.
Some computers which were marketed in the 1990s were called "multimedia" computers because they incorporated a CD-ROM drive, which allowed for the delivery of several hundred megabytes of video, picture, and audio data.
4.5.4 Word usage and context
Since media is the plural of medium, the term "multimedia" is a pleonasm if "multi" is used to describe multiple occurrences of only one form of media such as a collection of audio CDs. This is why it's important that the word "multimedia" is used exclusively to describe multiple forms of media.
The term "multimedia" is also ambiguous. Static content (such as a paper book) may be considered multimedia if it contains both pictures and text or may be considered interactive if the user interacts by turning pages at will. Books may also be considered nonlinear if the pages are accessed non-sequentially. The term "video", if not used exclusively to describe motion photography, is ambiguous in multimedia terminology. Video is often used to describe the file format, delivery format, or presentation format instead of "footage" which is used to distinguish motion photography from "animation", motion illustrations. Multiple forms of information content are often not considered multimedia if they don't contain modern forms of presentation such as audio or video. Likewise, single forms of information content with single methods of information processing (e.g. non-interactive audio) are often called multimedia, perhaps to distinguish static media from active media.
4.5.5 Creative industries
Creative industries use multimedia for a variety of purposes ranging from fine arts, to entertainment, to commercial art, to journalism, to media and software services provided for any of the industries listed below. An individual multimedia designer may cover the spectrum throughout their career. Request for their skills range from technical, to analytical, to creative.
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Commercial
Much of the electronic old and new media utilized by commercial artists is multimedia. Exciting presentations are used to grab and keep attention in advertising. Industrial, business to business, and interoffice communications are often developed by creative services firms for advanced multimedia presentations beyond simple slide shows to sell ideas or liven-up training. Commercial multimedia developers may be hired to design for governmental services and nonprofit services applications as well. Entertainment and fine arts
In addition, multimedia is heavily used in the entertainment industry, especially to develop special effects in movies and animations. Multimedia games are a popular pastime and are software programs available either as CD-ROMs or online. Some video games also use multimedia features. Multimedia applications that allow users to actively participate instead of just sitting by as passive recipients of information are called Interactive Multimedia. In the Arts there are multimedia artists, whose minds are able to blend techniques using different media that in some way incorporates interaction with the viewer. One of the most relevant could be Peter Greenaway who is melding Cinema with Opera and all sorts of digital media. Another approach entails the creation of multimedia that can be displayed in a traditional fine arts arena, such as an art gallery. Although multimedia display material may be volatile, the survivability of the content is as strong as any traditional media. Digital recording material may be just as durable and infinitely reproducible with perfect copies every time.
Education
In Education, multimedia is used to produce computer-based training courses (popularly called CBTs) and reference books like encyclopedia and almanacs. A CBT lets the user go through a series of presentations, text about a particular topic, and associated illustrations in various information formats. Edutainment is an informal term used to describe combining education with entertainment, especially multimedia entertainment.
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Learning theory in the past decade has expanded dramatically because of the introduction of multimedia. Several lines of research have evolved (e.g. Cognitive load, Multimedia learning, and the list goes on). The possibilities for learning and instruction are nearly endless.
Engineering
Software engineers may use multimedia in Computer Simulations for anything from entertainment to training such as military or industrial training. Multimedia for software interfaces are often done as a collaboration between creative professionals and software engineers.
Industry
In the Industrial sector, multimedia is used as a way to help present information to shareholders, superiors and coworkers. Multimedia is also helpful for providing employee training, advertising and selling products all over the world via virtually unlimited web-based technologies.
Mathematical and Scientific Research
In Mathematical and Scientific Research, multimedia are mainly used for modelling and simulation. For example, a scientist can look at a molecular model of a particular substance and manipulate it to arrive at a new substance. Representative research can be found in journals such as the Journal of Multimedia. Medicine
In Medicine, doctors can get trained by looking at a virtual surgery or they can simulate how the human body is affected by diseases spread by viruses and bacteria and then develop techniques to prevent it.
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Miscellaneous
In Europe, the reference organization for Multimedia industry is the European Multimedia Associations Convention (EMMAC). An observatory for jobs in the multimedia industry provides surveys and analysis about multimedia and ITC jobs. Structuring information in a multimedia form
Multimedia represents the convergence of text, pictures, video and sound into a single form. The power of multimedia and the Internet lies in the way in which information is linked. Multimedia and the Internet require a completely new approach to writing. The style of writing that is appropriate for the 'on-line world' is highly optimized and designed to be able to be quickly scanned by readers. A good site must be made with a specific purpose in mind and a site with good interactivity and new technology can also be useful for attracting visitors. The site must be attractive and innovative in its design, function in terms of its purpose, easy to navigate, frequently updated and fast to download. When users view a page, they can only view one page at a time. As a result, multimedia users must create a â&#x20AC;&#x2DC;mental model of information structureâ&#x20AC;&#x2122;.
Patrick Lynch, author of the Yale University Web Style Manual, states that users need predictability and structure, with clear functional and graphical continuity between the various components and subsections of the multimedia production. In this way, the home page of any multimedia production should always be a landmark, able to be accessed from anywhere within a multimedia piece.
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INFORMATION TECHNOLOGY 4.6
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ISDN (Integrated Services Digital Network)
The telephone service has been the major telecommunications service.
The
telephone system, an analog voice transmission system, is not adequate for various other types of modern communication services like data transmission, facsimile, video transmission etc.
The necessity of a new digital system to cater to these requirements led to the
evaluation of Integrated Services Digital Network (ISDN). The main aim of ISDN is to integrate voice and other telecommunications services over a digital system.
The first type of ISDN service will be voice transmission with several added features. Some of these features are instant call setup locally or worldwide, display of caller’s telephone number, name of address, call transfer worldwide, conferencing world wide etc. The ISDN data communication services included facilities for connecting user’s ISDN terminal to that of any other user anywhere in the world, simultaneous connections to many terminals, establishing closed groups of users with the group members communicating among themselves only etc.
A recent service being offered is called videotext, an interactive access service to remote data base like on-line telephone directory, on-line yellow pages on so on. Using this service, teleshopping, reservations in trains, airlines and hotels and a host of other applications may become possible. Another recent service being offered by ISDN is called teletex. It is a mailing system for domestic and commercial purposes. It can be used on simple computer terminals for text and simple graphics transmission. Facsimile or Fax is another ISDN service in which an image is scanned digitized transmitted as a bit stream, received by the receiving terminal and the original image reproduced.
Other types of services included telemetry or alarm services. For example, electricity meters or water consumption meters may be made on-line and read directly by the electricity or water distribution companies.
Smoke or fire detectors in residential apartments or
business organizations may automatically call fire services when necessary, using alarm services. Few of these services are available in elementary form. ISDN is still evolving to integrate the proposed services and make them suitable for widespread usage.
The user has access to ISDN by means of user ISDN interface. The user interface connects telephones, computers, telephone exchanges, computer networks and so on to the digital pipe of the ISDN. The digital pipe is the channel used for connecting various users’ interfaces to the ISDN exchange. Digital pipes of different sizes, or capacities are used for
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INFORMATION TECHNOLOGY different needs. A non-commercial user may require only telephone and videotext services with a smaller capacity pipe. A business organization may wish to connect its private branch exchanges or local area networks to ISDN with a larger capacity pipe. The pipe to the customer’s premises has got a fixed capacity. The load on the pipe i.e. traffic on it may be any mix upto the maximum capacity. A user may use smaller capacity than the maximum capacity of the digital pipe. The user will be charged according to the capacity usage.
The subscriber loop or local loop is the connection between the user interface and the ISDN exchange. In other words it is a part of digital pipe. The ISDN exchange provides access to various types of networks, databases and so on. The digital pipe between the exchange and the user carries a number of communications channels. The pipe capacity and the number of channels carried will differ from user to user.
4.6.1 ISDN Channels
ISDN channels are classified as
B Channel (64 kbps)
D Channel (16 or 64 kbps)
H Channel (384 or 1536 or 1920 kbps)
In addition, A channel consists of 4 kHZ analog telephone channel and C channel consists of 8 or 16 kbps digital channel.
B Channel is the basic channel used to carry digital data, digitized voice or any mixture of data and voice. If the traffic is a mixture, then it must be transmitted to the same destination. Using this B channel, four types of connections may be setup.
1. Circuit Switched Network 2. Packet Switched Network 3. Frame Mode Connection 4. Establishing connection through a leased line.
The D channel is used to carry control signals for the associated B channel. It is also used for low speed data transfer like videotext, teletex, telemetry and alarm service.
H channels are used for high speed applications like fast facsimile, video, high speed data or multiple transmissions at lower rates.
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These channels are grouped into various access schemes for differing user needs. They are
Basic Access Scheme : 2 B channel + 1 D channel
Primary Access Scheme : 23 B Channel + 1 D channel ( in the USA and Japan) or 30B + 1 D channel (in Europe)
The major uses of ISDN are (i) Video Conferencing and (ii) Graphic World Wide Web.
4.6.2 PRINCIPLES OF ISDN
Principles of ISDN are
1. The main feature of the ISDN concept is the support of a wide range of voice and non-voice applications in the same network. 2. ISDN support a variety of applications including both switched and nonswitched connections. Switched connection in an ISDN include both circuit switched and packet switched connections and their concatenations. 3. An ISDN will contain intelligence for the purpose of providing service features maintenance and network management functions. 4. A layered protocol structure should be used for the specification of the access to an ISDN. 5. It is recognized that ISDN may be implemented in a variety of configuration according to specific national situations. 6. New services introduced into an ISDN should be arranged to be compatible with 64k bit/s switched digital connections.
4.7
OSI MODEL
In 1984, a group known as the International Organisation for Standardization (ISO) created a model called the Open Systems Interconnect (OSI). This model defined guidelines for interoperability between network manufacturers. This ISO 7498 – OSI Protocol is also termed as Open System Interconnection Reference Model. OSI model is the most widely used model for networking. A company could now mix and match network devices and protocols from various manufacturers in its own network without being locked into using a single vendor.
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Although the OSI model defined a set of standards, it is important to note that it is merely a model. Many other models exist in the networking industry; however, understanding a single model gives us the capability of understanding other models in the future. The OSI model is the most widely taught as the foundation for this knowledge.
The OSI model does not specify the communication standard or protocols to be used to perform networking tasks. OSI model provides following services.
1. Provide peer to peer logical services with layer physical implementation 2. Provide standards for communication between system. 3. Define point of interconnection for the exchange of information between systems. 4. Each layer should perform a well defined function. 5. Narrow the options in order to increase the ability to communicate without expansive conversions and translations between products.
The OSI model is divided into seven layers. The following table lists the name and order of each layer.
Application
Layer 7
Presentation
Layer 6
Session
Layer 5
Transport
Layer 4
Network
Layer 3
Data Link
Layer 2
Physical
Layer 1
The bottom layer is identified as the first layer. It is important to remember the order of the layers in the OSI model.
Each layer is separated, or encapsulated, from each other
layer. This means that each layer can function on its own. Each layer thinks it is talking directly to the same layer on there mote computer through a virtual link. Further more, each layer can only communicate with the layers above and below it. In fact, the layer doesn’t know that any other layers even exist.
These seven layers can be grouped as follows:
Reliable Transmission of Information – Layers 1 to 4
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Meaningful exchange of information – Layers 5 to 6
Layers and Their Functions
LAYER
FUNCTIONS
7. Application
Can exchange meaningful information to other open system Eg. Bibliographic information system – ISO 2709, UNIMARC Electronic ordering – BISAC – Book Industry System Advisory Committee; SISAC – Serial Industry System
Advisory
Committee. 6. Presentation
Transformation of data from the format of one application to the format acceptable to another open system applications. Eg .ASCII bit to EBCDIC bit
5. Session
User’s interface to network user negotiates with this layer to establish connection with a process on another machine. Once connection is established session layer can handle the dialog in an orderly manner. Session layer is used to allow a user to remotely login to a time sharing system or to transfer a file between two computers.
4. Transport
Accepts data from session layer, splits up into smaller units, if required and pass them to the network layer. It may either create multiple network connections if high throughput is required or may multiplex several transport connections into a simple network. This also decides type of network service to be provided – point-to-point, sequential delivery of messages or data-gram service or broadcast service etc.
3. Network
Controls the operations
2. Data link
Accepts input data for network layer, breaks it layer into data frames transmits the frames sequentially and processes acknowledgement frames sent by receiver.
1. Physical
4.8
Transmits the raw bits over the communication layer.
NETWORK ACCESSORIES Networking Accessories includes all computers, peripherals, interface cards and
other equipment needed to perform data-processing and communications within the network.
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INFORMATION TECHNOLOGY The different network accessories, besides conventional wires, cables, cards, are
File Servers
Workstations
Network Interface Cards
Concentrators/Hubs
Repeaters
Routers
Bridges
4.8.1 FILE SERVERS
A file server stands at the heart of most networks. It is a very fast computer with a large amount of RAM and storage space, along with a fast network interface card. The network operating system software resides on this computer, along with any software applications and data files that need to be shared. The file server controls the communication of information between the nodes on a network. For example, it may be asked to send a word processor program to one workstation, receive a database file from another workstation, and store an e-mail message during the same time period. This requires a computer that can store a lot of information and share it very quickly. File servers should have at least the following characteristics:
166 megahertz or faster microprocessor (Pentium, PowerPC)
A fast hard drive with at least nine gigabytes of storage
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A RAID (Redundant Array of Inexpensive Disks) to preserve data after a disk casualty
A tape back-up unit (i.e. DAT, JAZ, Zip, or CD-RW drive)
Numerous expansion slots
Fast network interface card
At least of 32 MB of RAM 4.8.2 WORKSTATIONS
All of the computers connected to the file server on a network are called workstations. A typical workstation is a computer that is configured with a network interface card, networking software, and the appropriate cables. Workstations do not necessarily need floppy disk drives or hard drives because files can be saved on the file server. Almost any computer can serve as a network workstation.
4.8.3 NETWORK INTERFACE CARDS The network interface card (NIC) provides the physical connection between the network and the computer workstation. Most NICs are internal, with the card fitting into an expansion slot inside the computer. Some computers, such as Mac Classics, use external boxes which are attached to a serial port or a SCSI port. Laptop computers can now be purchased with a network interface card built-in or with network cards that slip into a PCMCIA slot. Network interface cards are a major factor in determining the speed and performance of a network. It is a good idea to use the fastest network card available for the type of workstation you are using. The three most common network interface connections are Ethernet cards, LocalTalk connectors, and Token Ring cards. According to a International Data Corporation study, Ethernet is the most popular, followed by Token Ring and LocalTalk (Sant'Angelo, R. (1995). NetWare Unleashed, Indianapolis, IN: Sams Publishing).
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4.8.3.1 Ethernet Cards Ethernet cards are usually purchased separately from a computer, although many computers (such as the Macintosh) now include an option for a pre-installed Ethernet card. Ethernet cards contain connections for either coaxial or twisted pair cables (or both) (See fig. 1). If it is designed for coaxial cable, the connection will be BNC. If it is designed for twisted pair, it will have a RJ-45 connection. Some Ethernet cards also contain an AUI connector. This can be used to attach coaxial, twisted pair, or fiber optics cable to an Ethernet card. When this method is used there is always an external transceiver attached to the workstation. (See the Cabling section for more information on connectors.)
Fig. 1. Ethernet card. From top to bottom: RJ-45, AUI, and BNC connectors 4.8.3.2 LocalTalk Connectors
LocalTalk is Apple's built-in solution for networking Macintosh computers. It utilizes a special adapter box and a cable that plugs into the printer port of a Macintosh (See fig. 2). A major disadvantage of LocalTalk is that it is slow in comparison to Ethernet. Most Ethernet connections operate at 10 Mbps (Megabits per second). In contrast, LocalTalk operates at only 230 Kbps (or .23 Mbps).
Ethernet Cards vs. LocalTalk Connections Ethernet
LocalTalk
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Fast data transfer (10 to 100 Mbps)
Slow data transfer (.23 Mbps)
Expensive - purchased separately
Built into Macintosh computers
Requires computer slot
No computer slot necessary
Available for most computers
Works only on Macintosh computers
4.8.3.3 TOKEN RING CARDS Token Ring network cards look similar to Ethernet cards. One visible difference is the type of connector on the back end of the card. Token Ring cards generally have a nine pin DIN type connector to attach the card to the network cable.
4.8.4 Concentrators/Hubs
A concentrator is a device that provides a central connection point for cables from workstations, servers, and peripherals. In a star topology, twisted-pair wire is run from each workstation to a central concentrator. Hubs are multislot concentrators into which can be plugged a number of multi-port cards to provide additional access as the network grows in size. Some concentrators are passive, that is they allow the signal to pass from one computer to another without any change. Most concentrators are active, that is they electrically amplify the signal as it moves from one device to another. Active concentrators are used like repeaters to extend the length of a network. Concentrators are: • Usually configured with 8, 12, or 24 RJ-45 ports • Often used in a star or star-wired ring topology • Sold with specialized software for port management • Also called hubs • Usually installed in a standardized metal rack that also may store netmodems, bridges, or routers
4.8.5 Repeaters
Since a signal loses strength as it passes along a cable, it is often necessary to boost the signal with a device called a repeater. The repeater electrically amplifies the signal it receives and rebroadcasts it. Repeaters can be separate devices or they can be incorporated
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A good example of the use of repeaters would be in a local area network using a star topology with unshielded twisted-pair cabling. The length limit for unshielded twisted-pair cable is 100 meters. The most common configuration is for each workstation to be connected by twisted-pair cable to a multi-port active concentrator. The concentrator amplifies all the signals that pass through it allowing for the total length of cable on the network to exceed the 100 meter limit.
4.8.6 Bridges
A bridge is a device that allows you to segment a large network into two smaller, more efficient networks. If you are adding to an older wiring scheme and want the new network to be up-to-date, a bridge can connect the two. A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location. Most bridges can "listen" to the network and automatically figure out the address of each computer on both sides of the bridge. The bridge can inspect each message and, if necessary, broadcast it on the other side of the network.
The bridge manages the traffic to maintain optimum performance on both sides of the network. You might say that the bridge is like a traffic cop at a busy intersection during rush hour. It keeps information flowing on both sides of the network, but it does not allow unnecessary traffic through. Bridges can be used to connect different types of cabling, or physical topologies. They must, however, be used between networks with the same protocol.
4.8.7 Routers
A router translates information from one network to another; it is similar to a super intelligent bridge. Routers select the best path to route a message, based on the destination address and origin. The router can direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along back roads and shortcuts. While bridges know the addresses of all computers on each side of the network, routers know the addresses of computers, bridges, and other routers on the network. Routers can even "listen" to the entire network to determine which sections are busiest -- they can then redirect data around those sections until they clear up.
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INFORMATION TECHNOLOGY If you have a LAN that you want to connect to the Internet, you will need to purchase a router. In this case, the router serves as the translator between the information on your LAN and the Internet. It also the best route to send the data over the Internet. Routers can: • Direct signal traffic efficiently • Route messages between any two protocols • Route messages between linear bus, star, and star-wired ring topologies • Route messages across fiber optic, coaxial, and twisted-pair cabling
4.9
CONCLUSION
The frequent technological development and new innovations have a greater impact in network architecture. It is essential to upgrade knowledge on these concepts frequently becomes mandatory.
UNIT QUESTIONS
1. What is network protocol 2. Discuss briefly about Hyper Text 3. Distinguish between Hyper Text and Hyper Media 4. Write notes on Multi media 5. Explain the concept ISDN 6. Write elaborately on OSI Protocol 7. Discuss different types of Network Accessories.
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UNIT V INTERNET TECHNOLOGY 5.1
Objectives
5.2
INTERNET – introductory concept
5.3
Historical Development
5.4
Type of Connections
5.5
Web Resources
5.6
Web Portal
5.7
Browsers
5.8
Search Engines
5.9
Internet Tools
5.10
References
5.1 OBJECTIVES
After studying this lesson, you should be able to
Understanding the overview of internet technology
Different types of internet connectivity
Describe various types of Web resources
Different types Browsers, search engines
Identify the different types of Internet Tools
5.2 INTERNET Infusion of technologies into creative process leads to new technology, which enters into creative spheres at varying speed over different routes. To day it seems that each new advance in technology centres around new ways to store, retrieve and transmit information. The PC can now deliver all types of information i.e. text, still images, graphics, audio etc.. More importantly the Personal computers has the ability to present all type of information in two different ways i.e. in an integrated way and in an interactive way. It is quite clear that qualitative change in the nature of information storage and retrieval has taken place. Internet has come up in a big way for retrieval of enormous output of information combining the concepts of time, space and precision.
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5.2.1 WHAT IS INTERNET? The Internet is a system that lets computers all over the world to communicate with each other. The internet is a network of networks that connects computers all over the world
Internet is the largest worldwide network linking 140 countries with 3 million host computers and an estimated 40 million users. The Internet grows at the rate of 2,00,000 users per month. a) It’s a Network The computers on the Internet can talk to one another because they are networked; they are connected in some way so that they can exchange information with one another electronically. On the Internet, the connections take many different forms. Some computers are directly connected to others with wire or fiber-optic cables. Some are connected through local
and
long-distance
telephone
lines,
and
some
even
use
wireless
satellite
communications. b) It’s a loose organization
Although most people think or talk about the Internet as if it were some giant company or club, it really isn’t. No single entity or organization controls it. The computers on it are controlled by their owners. Nobody controls the Internet. People simply join up and participate. It’s like a neighborhood where rules, and leaders. Just as each computer on the Internet is under its owner’s control, some networks that make up a large part of the Internet are controlled by their owners. c) It’s a relaxing place
Internet resources enable users to exchange information in an open, public way. These resources provide a forum where users can write and post messages for other users and where they can read messages posted by others. These resources play the open-airexchange-site role played by public meeting place.
There are thousands of resources, but the following list may give you a feel for the range of topics like Ceramics, Computers, Disabilities, Film and TV, Holistic Medicine, Nutrition, Law, Mystery Fiction, Astrology, Politics, Employment, Religion, Games, Mail.
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d) It’s a Business Tool
The increasingly global business climate and the great extent to which big companies relay on computers, the Internet looks like a great vehicle for national and international business communication. It is certainly cheaper and more flexible than building a private, global computer networks from scratch. Now a days, several organizations are running their business through Internet for various purposes like document exchange, Internet banking, Payment etc. e) It’s a Mailbox
The most-used Internet facility is electronic mail, also known as e-mail. Everyone who lives in the Internet world has a unique Internet name, - email id. To send a message to an Internet user, anywhere in the world all the sender has to know the address of the recipient. The sender types up a message in his or her favourite word processing or e-mail software program, hooks on to the internet, types in the address and sends the message on its way. f) It’s an Information Pool
Internet is a pool of information. Whatever the information the users in need, it can be easily located and utilized from the Internet. Today Internet is the best utility that is available to all the users at cheaper prices to know about things. It’s an information pool that satisfies varied level of users from kids to old age, from students to business professions, from small and mid size organizations to Multi National companies, researchers and Government organizations. g) It’s a living thing
The Internet is a living thing, growing its own way, at its own pace, perhaps according to a divine design, but not according to any plan.
In the coming years, one can hear
increasing concern over the global economic, political, and cultural implications of the Internet.
5.3 HISTORICAL DEVELOPMENT OF INTERNET
The roots of internet, as in many cases, found in the military. computer scientists, in the year 1969, thought
A group of
of building a computer network that
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enable
researchers
around
85 the
USA to share ideas.
This becomes the
foundation of the Internet. The initial plan was to link four sites, the University of California (UCLA), Santa Barbara, the Standford Research Institute and the University of Utah. This project was called ARPANET, Advanced Research Project Agency
NETwork, after the
agency that initiated it.
The first official demonstration was held during 1969 by means of hooked up of computers between UCLA and Standford Research University which was separated by hundreds of kilometers away. In the year 1971 nearly 24 sites were connected. By the year 1981 there were more than 200 connections.
Scientists, Research Institutions and
Educational Organizations shown keen interest on connecting to the network, though their computers, could be of different size and speed.
As more and more computer connected, the ARPANET was replaced by the NSFNET, which was run by National Science Foundation. In late 1980’s the barrier of NSFNET for using Military and Research people has been broken away. By that it has reached public to use it. In 1989, the WWW has emerged for information services and 1990’s the combination of email, the web and online chat boosted the use of Internet Service across National and International prominence.
HARDWARE REQUIREMENTS FOR INTERNET BROWSING
The hardware requirements for having Internet facilities are - computer (reasonably fast – 386 and above) - Telephone Line - High speed Modem 14,400 bps ( rganizati 28,800 bps) - Simple communication software - An Internet account
5.4
TYPE OF CONNECTIONS
Type of connections can be categorized as follows
Dial-up connection
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Leased Line connection
Dedicated connection
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WEB RESOURCES Web resources are identified with a special name called “Uniform Resource
Identifiers (URIS)”. These identify objects that may be accessed on the web. These identify objects that may be accessed on the Web. Web pages are identified through its “Uniform Resource Locators (URLs).URLs are simply, address for documents on the Web.
The
different parts of the URL are:
Protocol (Eg. http – Hyper Text Transfer Protocol)
Hostname
Filename.
The syntax will be Protocol:://hostname/filename
Eg. (i) http://www.drtc.edu (ii) http://www.microsoft.com
The URL describes the protocol used to reach the target server, the host system on which the document resides, the directory path to the document, and the document file name. The uniform naming scheme for resources is makes the World Wide Web such a rich information environment.
5.5.1 INFORMATION SOURCES OVER THE WEB
Electronic Journals
Electronic Discussion Lists/ Forums
Usenet News
Data and Software Archives
E-mail based Information Services
Campus Wide Information Systems
Library Catalogues – Web OPACs
Online Databases
Guides to Information Sources
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Search Engines
Subject Gateways
Web Directories
Online Chatting
Commercial advertisings & Customer Service Information
Organisations’ Directories
Bulletin Board Services
Full text of documents
5.5.2 TYPES OF WEB RESOURCES 1. Open Web – Any thing online that can be found freely with a Search Engine 2. Gated Web- Online Resources accessible by Subscription E.g. OED, CA, LISA, BIOSIS, INSPEC, COMPENDIX etc. 3. Invisible Web – Databases that are not found by Search Engines and can only be accessible through a particular page or front end. E.g. LC’s American Web Site http://memory.loc.org 5.5.3 MEANS OF ACCESS TO WEB RESOURCES
1. Through Search Engines 2. Through Web OPACs 3. Through Specified URLs/ Web sites
5.5.3.1 Through Search Engines
Yahoo http://www.yahoo.com
Altavista http://www.altavista.com
Lycos http://www.lycos.com
Google http://www.google.com
Excite http://www.excite.com
Hotbot http://www.hotbot.com
5.5.3.2 WEB RESOURCES: Vendor wise
IEL Online (http:\\Ieeexplore.lee.org) IEEE/IEE Electronic Library (IEL) provides a single source to almost of the world’s current electrical engineering and computer science literature.
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Grants
unparalleled access to publications from the Institute of Electrical and
Electronics (IEEE) and the Institution of Electrical Engineers (IEE).
Cover more than 780,000 documents from over 12,000 publications, including, journals conference proceedings, and IEEE standards.
Provides access to more than two million full-page PDF images.
Resources 110 Journals, transactions, magazines, conference proceedings, standards.
Back-files1988 onwards
Archival Access on DVD at 5% of prevailing subscription rates
Elsevier’s Science Direct (http://www.sciencedirect.com)
Science Direct is the web-based interface to the full-text database of Elsevier Science journals
One of the world’s largest providers of scientific, technical and medical literature.
Offers a rich electronic environment for research journals, bibliographic databases and reference works.
Offers more than 1500 scientific, technical, medical peer reviewed journals, over 59 million abstracts, over two million full- text scientific journals articles, an expanding suite of bibliographic databases.
Linking to another one million full-text articles via cross reference to other publisher’s platforms.
Resources 1500 Journals published by Elsevier Science and Academic Press
Participants are required to maintain their print Subscription
Back-files1995 onwards
Archival Access offered on the cost of preparing set
Springer Verlag’s Link (http://link.springe.de) Springer Verlag’s Link provides Web-based full-text access to the scientific journals published by the Springer Verlag.
Incorporates full text of more than 450 journals, several thousand books and other serial publications.
Offers full- text access to complete collection of their electronic journals (approximately 400) excluding journals in medical science with restrictions in number of downloads limited to maximum of 2,000.
Well known series of titles like Lecture Notes in Computer Sciences, Physics Mathematics, etc., in the e-book collection.
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Famous series of e-reference books like Advances in Polymer Science, LandoltBornstein Series are available.
Institutions are required to maintain their print subscription.
Deletion of subscribed titles not allowed
Back-files1980 onwards
Archival Access offered on one time fee of Euro 15,000
ACM Digital Library (http://portal.acm.org/portal.cfm)
ACM digital library incorporates digital versions of works published by ACM since its inception.
Nearly half a century of pioneering concepts and fundamental research have been digitized and indexed in a variety of ways in this resource.
Major components of the resources are an enhanced version of the ACM digital library plus an extended bibliographic database consisting initially of more than a quarter- million citations of crore works in computing.
Covers works are of all types (journal, proceedings, books, technical reports, theses, among others), and from all the major publishers in the discipline.
Resources would be accessible through the Web site of ACM digital library.
Resources 30 full-text Journals, conference proceedings and others.
No Print-base.
Web media with CD ROM backup.
Back-files since inception.
Archival Access on CD ROM.
Ei Compendex plus and INSPEC (http://www.engineeringvillage2.org)
Ei compendex provides summaries of technical reports, journals articles, and conference papers and proceedings.
It is the world’s only fully interdisciplinary engineering indexing and abstracting service. It covers over 2,600 international engineering journals, conference proceedings and technical reports.
Each year, 200,000 new abstracts are added with in the broad applied engineering areas of mechanical, civil, environmental, electrical, structural, process, material science, solid state and super conductivity, bioengineering, energy, chemical, optics, air and water pollution, solid waste management, and road transportation.
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Knit-Rider Information Services Inc., (DIALOG) http://www.dialog.com
Serving since 1972
Covers about 400 databases
One stop service for all the information needs.
Areas covered: Agriculture; Food and Nutrition; Chemistry; Biosciences and Technology; Engineering; Business and Information; Company Information and Financial Data; Computers and Software; Physical Sciences; Energy and Environment; Industry Analysis; Government and Public Affairs; Travel; Medicine, Health Care ad Drug Information; Patents, Trademarks and Copyrights; People, Books and Consumer News; Social Sciences and Humanities.
Products: DIALOG Business Connection (DBC); DAILMAIL; DIALOG Alert; DIAL Order; DIALINDEX; One Search; DIALOG on Disc; DIALOG Link.
Silver Platter http://www.silverplater.com
Covers about 180 databases.
Areas covered: Education; Food and Agriculture; Social sciences; Science and Technology; Health Sciences; Business; Humanities; Environment; Ref. Sources.
Provides world wide access to electronic information sources.
Proquest Databases (UMI) URL: http://www.umi.com
1938 – Universal Microfilm International.
Areas covered: Business; scientific; Technical; humanities; General reference.
Products: Abstract and Index databases; Full Text Databases; Full Image Databases.
UMI Document Delivery Services: Supply of articles reprints; Supply of reprints of theses
ADONIS (Advanced Document Over Network Information Services)
Covers about 650 journals from 40 publishers.
Covers Biomedicine,Bioengineering,Biochemistry,Biotechnology.
Supplies weekly new CDRom to the subscribers of this service, which covers all articles in the fields covered.
EEVL - Edinburgh Engineering Virtual Library
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EEVL provides a central access point to networked engineering information for the UK higher education and research community.
It is a free service, created and run by a team of information specialists from HeriotWatt University, with input from many other UK universities.
EEVL covers a Catalogue of selected engineering resources, targeted engineering search engines -
The CORE Project
Chemical Online Retrieval Experiment [CORE] at Cornell university Mannis library.
Started by American Chemical Society with OCLC.
Provide access via electronically to all the journals of ACS.
IEEE/IEE Electronic Library
Joint venture by Institute of Electrical and Electronics Engineers (USA) and Institute of Electrical Engineers (UK).
Covers records from INSPEC database.
Covers IEEE/IEE Journals, Conference Proceedings standards etc.
Adds 25,000 (approx.) records per year.
Fields covered: Electrical Engineering;Electronics;IT;Computer science;applied Physics and related areas.
Subscribers will get monthly updates.
American Chemical Society
First professional association to bring electronic form of its 28 periodicals in full text over Bibliographical Retrieval Service (BRS) in 1983.
By 1993, there were 6998 online ND cd Rom databases
Institute of Scientific Information (ISI)
http://www.isinetcom is the site for the Institute for Scientific Information, Philadelphia that has fully integrated e-information solutions. Following details can be obtained while accessing this site:
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INFORMATION TECHNOLOGY About ISI Company Information Journal Lists News ISI Staff Articles Search Employment Training & Support ISI Links, etc
ISI Chemistry is a web-based source of information on new synthetic methods and novel organic compounds. ISI Chemistry delivers the same content publishing in Index Chemicus (IC) and Current Chemical Reactions (CCR) in an easy to read format with advanced searching capabilities.
CCR contains approximately 6,24,000 reactions abstracted from journal articles since 1985 onwards. CCR is updated by 3,000 reactions each month. IC contains approximately 1.4 million compounds abstracted from journal articles from 1996 onwards. 3,500 compounds update it each week.
J-Gate http://www.informindia.co.in
India’s first global e-journal portal.
J-Gate offers around 3 million articles since 2001
No. of Journals covered is about 10,000
No. of articles indexed is about 28 lakhs
No. of articles added each week is about 20,000
No. of free full text access journals covered is about 1,600
No. of free full text articles indexed and linked is about 4 lakhs
No. of articles with author e-mail address is about 9 lakhs
5.5.3.3 WEB RESOURCES: SUBJECT WISE The few subject wise web resources are discussed below. Engineering Sciences
In the field of Engineering Sciences the following URLs can be accessed for web based resources:
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www.library.ucsb.edu/subj/enqineer.html By this web site databases like Compendex Plus, Computer Article Database, Current Contents, INSPEC, Magazine and Journal Articles, etc are accessibile. Also accessibility to Newsgroups, Organisations are possible..
http://bubl.ac.ukllink/enqineerinqlinks.html By this one can access the BUBL link with other accessibility like Edinburg Engineering Virtual Library, and the Databases on Engineering of different disciplines.
http://www2.widener.eduIW0Ifqram-M...ary/su bject quides/enqineerinq .htm where one can get the selected resources for Engineering Research which is more useful for doing research activity. In the field of Chemical Sciences the following URLs can be accessed for web based resources: -
http://www.cas.orq/ This web site is from Chemical Abstracts Service provider. CAS is the producer of the world's largest and most comprehensive databases of chemical information. This covers Chemical Abstracts and Registry. CAS also produces databases of chemical reactions, commercially available chemicals, listed regulated chemicals and compounds claimed in patents. http://pubs.acs.orq/ This site is from the American Chemical Society (ACS) who is the largest producer of Chemical information in the world. One can see thE3 Jist of journals published by the ACS and can search them. Some are freely available with contents.
Medical Sciences
In the field of Medical Sciences the following URLs can be accessed for web based resources:
http://www.nih.qov/ This site is from the U.S. Department of Health and Human Services. One can get information about publications, fact sheets, clinical trials, grants and funding opportunities, sciertrific resources, etc. by accessing this site. http://www.nlm.nih.gov This site is from the U.S. National Library of Medicine, wherein one can get information related to' MEDLlNE, accessing could download MEDLINEplus, Library Services like catalog, databases, publications, etc. and other information.
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INFORMATION TECHNOLOGY http://www.ncbi.nlm.nih.gov/ This site is from the National Centre for Biotechnology Information. It acts as a national resource for molecular biology information. Creates databases, conducts research in computational technology, develops software,etc. it related areas. http://www.healthseek.com/ This site is popular for healthcare community and used by hundreds of care giving professionals, medical patients, consumers and ordinary people. Many other web sites can also reached thru' this site, as it has linkages to them. http://avurvedaindia.orq/ This is launched recently by the Capital based NGO Ashtvaidyam Ayurveda Foundation in New Delhi, which explains the fundamental of Ayurveda to the layman in plain and simple language. It is to spread the knowledge of our ancient sciences among the masses.
Mathematical Sciences
In the field of Mathematical Sciences the following URL can be accessed for web based resources: http://www.emis.de/ This is a- site for accessing the European Mathematical Information Service offered by European Mathematical Society. One can access the European countries as well as other countries. http://www.emis.de/journals This is a site for Mathematicians, wherein they get the list of journals in Mathematics. They will be able to see the contents pages of e-journals among them. In the field of Social Sciences the following URLs can be accessed for web based resources: http://www.ssm.com/ This is a site for Social Science Research Network, devoted to the worldwide dissemination of social science research and is composed of a number of specialized research networks in each of the social sciences.
5.6
WEB PORTAL
It is commonly referred to as simply a portal, a Web site or service that offers a broad array of resources and services, such as e-mail, forums, search engines, and on-line repositories. Traditionally, a portal denotes a gate, a door, or entrance. In the context of the World Wide Web, it is the next logical step in the evolution to a digital culture. Web pages are not completely self-referential anymore, but allow for personalization, workflow, notification, knowledge management and groupware, infrastructure functionality, and integration of information and applications. The idea of a portal is to collect information from different
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sources and create a single point of access to information - a library of categorized and personalized content. It is very much the idea of a personalized filter into the web. Portals are often the first page the web browser loads when users get connected to the Web or that users tend to visit as an anchor site. But now most of the traditional search engines and web sites have transformed themselves into Web portals to attract and keep a larger audience. A web
portal
is
a
collection
of
all
pages
under
one
domain.
For
example
www.myuniversity.com, the online portal for collection and dissemination of information resources. So this is our web portal. No matter how small or large your institute is, members can profit enormously from a web portal. The reduced publishing costs alone are worth establishing a web portal for your institute. Imagine your all member institutes resources being collected and organized in such a way that any member can get up to date information from it. It may be documents, pictures, videos, lecture notes, exam results, live class room videos etc. Whenever you offer a new course or organizing program, you simply update your web portal any time of day and it will reach the members as early as possible. A web portal is a special website designed to act as a gateway to give convenient access to users.
5.6.1
WHAT A WEB PORTAL DOES?
Enables universal login
Handles both structured and unstructured data
Facilitates multi-channel consistency
Facilitates messaging and notification
Automated tuning: pervasive content can be tuned based on personalization, location, browser, etc.
5.6.2
Integration to other systems KEY FEATURES OF WEB PORTALS
Security
Access different data
Transactions
Search
Publish Content
Personal Content
5.6.3
WHAT A WEB PORTAL IS NOT?
It is not just a Website (which is usually characterized by static information)
It is not just a personalized intranet
It is not just a personalized extranet
It is not just a personalized front end for business applications
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It is not just groupware
It is not just a personalized knowledge management solution
It is not just a sophisticated search engine Instead, a portal is nothing less than just one personalizable, browser based user
interface to all the components mentioned above. 5.6.4
MAJOR FUNCTIONS OF WEB PORTALS According to the analyst and consulting company Ovum - as described in their study
"Enterprise Portals: New Strategies for Information Delivery", 2000 - the ideal portal is based on eight functionality areas:
Search and navigation
Information integration (content management)
Personalization
Notification (push technology)
Task management and workflow
Collaboration and groupware
Integration of applications and business intelligence
Infrastructure functionality
Although most of the functionality is not new, what is new is the idea that the business value of the whole is considerably more than the sum of its parts. Thus, a successful portal does not only consist of either a good collaboration support or a good integration of the information sources. Rather it consists of - just like a successful cooking recipe - a well-integrated mixture of the basic portal functionalities. The first three important functions are explained below.
5.6.5
SEARCH AND NAVIGATION
This functionality forms the basis for most of the successful public web portals meaning that a successful portal should support its users in an efficient search for contents. A Web portal should
Automatically present its users with the information appropriate to the user’s role.
Suggest additional information to the user, and/or allow the user to voluntarily personalize the information presented by the portal.
Allow the user to search for information that was not previously known to be relevant to the user’s role, but which may be available through the portal.
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BROWSERS Web browser, also called a “browser”, to access content published on a web server.
Web browsers are software programs that allow accessing the graphical portion of the Internet. Browsers allow the users to access various web sites and view the web pages. They provide the option of entering the URL of the site to be visited. Browser software can be divided into the following two categories:
Text based browsers - Lynx
GUI based browsers – NCSA Mosaic, Netscape Navigator, Internet Explore etc.
A browser is an application program that provides a way to look at and interact with all the information on the World Wide Web. The word "browser" seems to have originated prior to the Web as a generic term for user interfaces that let you browse (navigate through and read) text files online. By the time the first Web browser with a graphical user interface was generally available (Mosaic, in 1993), the term seemed to apply to Web content, too. Technically, a Web browser is a client program that uses the Hypertext Transfer Protocol (HTTP) to make requests of Web servers throughout the Internet on behalf of the browser user.
5.7.1 FUNCTIONS OF BROWSERS
While some browsers also support e-mail (indirectly through e-mail Web sites) and the File Transfer Protocol (FTP), a Web browser is not required for those Internet protocols and more specialized client programs are more popular.
Short for Web browser, a software application used to locate and display Web pages. The two most popular browsers are Netscape Navigator and Microsoft Internet Explorer. Both of these are graphical browsers, which means that they can display graphics as well as text. In addition, most modern browsers can present multimedia information, including sound and video, though they require plug-ins for some formats
5.7.2 TYPES OF BROWSERS
A commercial version of the original browser, Mosaic, is in use. Many of the user interface features in Mosaic, however, went into the first widely-used browser, Netscape Navigator. Microsoft followed with its Microsoft Internet Explorer. Today, these two browsers are the only two browsers that the vast majority of Internet users are aware of. Although the
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INFORMATION TECHNOLOGY online services, such as America Online, originally had their own browsers, virtually all now offer the Netscape or Microsoft browser. Lynx is a text-only browser for UNIX shell and VMS users. Another recently offered and well-regarded browser is Opera.
5.7.2.1 NETSCAPE
Netscape, now part of America Online (AOL), is one of the two most popular Web browsers. Currently, almost all Internet users use either Microsoft's Internet Explorer (MSIE) browser or Netscape, and many users use both. Although Netscape was initially the predominant product in terms of usability and number of users, Microsoft's browser is generally considered superior by many users (although many other users see them as roughly equivalent) and has taken a significant lead in usage.
Netscape's browser, called "Navigator," was developed in 1995 by a team led by Marc Andreessen, who created Mosaic, the first Web browser that had a graphical user interface, at the University of Illinois' National Center for Supercomputing Applications (NCSA) in 1993.
The latest version of the Netscape browser can be downloaded from Netscape's Web site at no charge. CD-ROM versions can also be purchased in computer stores and are sometimes distributed freely as promotions
AOL envisions the Netscape Web site, now transformed into a leading Web portal, as a leading source of revenue through advertising and e-commerce.
5.7.2.2 MOSAIC
Mosaic was the first widely-distributed graphical browser or viewer for the World Wide Web. It is usually considered to have been the software that introduced the World Wide Web (and the Internet) to a wide general audience. Once Mosaic was available, the Web virtually exploded in numbers of users and content sites. (Of course, the software depended on the recent invention of the Hypertext Transfer Protocol by Tim Berners-Lee.)
Mosaic arrived in 1993. Marc Andreessen, then in his early 20s, is credited with inventing or leading the development of Mosaic. He developed it at the National Center for Supercomputing Applications (NCSA) at the University of Illinois in Urbana, Illinois. Andreessen and others went on to become part of Netscape Communications, originally
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INFORMATION TECHNOLOGY called Mosaic Communications, that developed one of today's most popular browsers, Netscape (its full name is Netscape Navigator). The original Mosaic, now in a later version, has since been licensed for commercial use and is provided to users by several Internet access providers.
5.7.2.3 NETSCAPE COMMUNICATOR
Officially called Netscape Communications Corporation, Netscape was founded by James H. Clark and Marc Andreessen in 1994 and was acquired by AOL in 1999. It revolutionized the computer software market by giving away for free its popular Navigator Web browser until it had acquired an overwhelming market share for this category of software. This strategy is now used by many other software companies, including Microsoft, which also distributes its Web browser, Internet Explorer, for free. The term Netscape is often used as the name of the company's browser, not the company itself.
5.7.2.4 INTERNET EXPLORER 6
Internet Explorer 6 is a set of core technologies in Microsoft Windows XP Home Edition and Windows XP Professional operating systems that provides enhanced privacy features and a flexible and reliable browsing experience for users of Windows XP, Windows Millennium Edition (Windows Me), Windows 2000, Windows 98, and Windows NT速 4.0 with Service Pack 6a or later. Whether you are a home user browsing content or getting e-mail on the Web, an IT administrator deploying and maintaining a rich set of Windows Internet technologies, or a Web developer creating Web content, Internet Explorer 6 gives you the freedom to experience the best of the Internet.
This overview describes some of the major features and technologies of Internet Explorer, provides information on how to get the latest version, and offers links to more information so you can start getting more from the Web the way you want.
FEATURES AND TECHNOLOGIES OF IE 6
Internet Explorer 6 includes many new and enhanced features that can simplify the daily tasks that you perform, while helping you to maintain the privacy of your personal information on the Web. Here is a quick look at some of the major features of Internet Explorer 6 that help to provide a flexible and reliable browsing experience on the Web.
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Flexibility With new, innovative browser capabilities and features such as Auto Image Resizing, Image Toolbar, Media Bar, and Print Preview, it's easy to manage, save, and print your pictures and other media from Web pages. Features such as Favorites, Auto Complete, History, and the Search Companion help you quickly find what you need online. And the customizable browsing layout makes it easy to change your layout so you can experience the Web the way you want.
Web Privacy Internet Explorer 6 helps you manage your security and privacy preferences while on the Internet with tools that help you safeguard your family's browsing experience. Manage cookies to help control the personal information that Web sites collect about you, set different levels of security for different sites on the Web with Security Zones, and use Content Advisor to help block access to objectionable content. These tools support the Platform for Privacy Preferences (P3P), a technology under development by the World Wide Web Consortium (W3C).
Reliability Internet Explorer 6 helps deliver a more stable and more reliable web browsing experience. New fault collection services help to identify potential problems that need to be fixed in future updates to Windows Internet technologies. Learn more about these and other Internet Explorer featuresâ&#x20AC;&#x201D;including the features that help developers build rich 5.7.2.5 OPERA BROWSER
The Opera browser started out in 1994 as a research project in Norway's telecom company, Telenor. Independent development was continued by Opera Software ASA in 1995. The first public release of the Opera Browser was version 2.12 although earlier demo versions have been found and screenshots of the 1.0 version are available on the web.
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Opera's co-founder Jon von Tetzchner made the first public announcement of Opera on usenet on July 14th 1996. He used the following introduction, which after many years of development still capture the core qualities of Opera
Series 1 Though not publicly released there are screenshots of the then-called MultiTorg Opera. It's fun to recognise the features that are still present in Opera's current form. In weblogs across the web evidence of a Multitorg Opera 1.0b4 can be found.
Series 2 The first public versions of Opera was the 2-series. They are of course extremely outdated but test-driving them you can witness the birth of the legend that is called Opera. The oldest version found is a Norwegian demo version of Opera 2.0 which was included with a PC Magazine. It will only load local pages but you can already see a lot of key features that have made Opera famous!
Series 3 The Opera 3 series saw Opera evolve from a geek's tool to a powerful browsing machine with a climax in features, stability and speed with version 3.62. This version is often taken as a the standard to which future version of Opera are compared. It was far ahead of its time in CSS support and this browser can still view the web in a surprisingly good way, considering its respectable age. . Series 4
Opera 4 was long-awaited the first browser based on a new cross-platform core which facilitated the release of Opera for different Operating Systems and thus speeding up Project Magic. The core supported more standards such as CSS1, CSS2, HTML4, XML and WML and a new integrated e-mail client was included. The O4 browser was meant as the leap towards the larger public. Unfortunately the earlier versions were very unstable and buggy and didn't do Opera's reputation much good, though the later maintenance release 4.02 was very usable.
Series 5: "The fastest browser on earth" The 5 series really made the jump to the large public due to the new ad-sponsored version instead of the 30-day trial period. Furthermore Opera 5 was stable and during
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INFORMATION TECHNOLOGY following releases it gained new features such as the integrated Instant Messaging, the fantastic mouse-gestures, hotlist panels and the integrated search. The 5 series ended with the 5.12 release which is still used by many today.
Series 6: "Simply the best Internet Experience" The Opera 6 series introduced the long-awaited unicode support. Also a new SDI/MDI interface was introduced, facilitating the transition from the SDI-browsers to Opera's unfulpraised MDI-interface. During the later bugfixreleases the kioskmode was enhanced, the integrated searches became editable and a lot of printing problems were solved. The 6 series has become stable and feature rich and now really has become a serious competitor to NN and Internet Explorer.
Series 7: "Hey Presto!" Opera 7 has been released in early 2003. It features a brand new rendering engine under the name Presto, which has enhanced and expanded its support for standards and now includes W3C DOM and the Small Screen Rendering technique for handheld devices. The entire interface was redone, making use of a custom cross-platform skinning system which significantly reduced resource usage, and the entire UI is now configurable: keyboard shortcuts, mouse gestures, menus and toolbars! With the new combined SDI/MDI interface the user has even more power at his command and new innovative features such a FastForward, Notes and Slideshow make the user experience even more enjoyable. Opera 7 is definitely the best browser available today!
An especially noteworthy change in Opera 7 is the new mail and news client, called M2. This e-mail client is based on a powerful filtering system and offers revolutionizing mail organizing abilities, which will change the way you handle your e-mail.
5.8 SEARCH ENGINES
A search engine is a program that searches through the Internet data. The search engines are primarily for locating the information in the web. A search engine is most often used in association with searching through databases of HTML documents. The components of a search engine are:
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a robot
a database
an agent
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5.8.1.1 The Robot
Robots are programs that traverse the WWW looking for the information specified. Robots move from one web document to the other by referring to the hyperlinks that are embedded in the web pages. Robots are also called as “Web wanderers”, “Web Crawlers” or “Spiders”.
5.8.1.2 The Database
The search engine database is that component which records all the indexed information.
It includes web addresses, titles, headers, words, first lines, abstracts and
sometime even full text in its lists.
Databases can store anywhere from a thousand to
millions of web pages. There are some search engines like “Lycos” which have more than one database.
5.8.1.3 The Agent
The agent is the interface between the user and the database. It is that program which represents the user to search database and displays a sorted list of “hits” after a user makes a search request. Generally, the basis of sorting is relevance to the search request.
5.8.2. TYPES OF SEARCH ENGINES
Search Engines can be categorized into three main types viz.
Individual Search engine
Directory type search engine
Meta Search engines.
5.8.2.1 Individual Search Engine
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The individual search engines can be categorized as full test and non-full text. It can also be divided on the basis of the procedure that their robots use to collect information from the database. Automated robots scan a large part of the web while designated robots re programmed to scan only specific sites. Some of the search engines give preference only to top level resources. Depth-oriented robots search deep into a document to pull out individual items and their respective links to other servers. Example for these type of search engines are www.google.com
5.8.2.2 Directory type search engine
Directories are hierarchical indexes.
They focus by subject matter for providing
information that is most commonly used access point by users. For example the Search engines www.yahoo.com and www.infoseek.com provides directories of major topics. The advantages of subject directories are very useful in browsing subject information.
5.8.2.3 Meta-Search Engines
It behaves as search engines for search engines. combination of a number of search engines.
Meta search engines are a
They are also called “Combined” or
“Simultaneous” search engine. Eg. www.vivisimo.com
Further the Search engines can also be classified as follows: Free text search engines – eg. Alta Vista, Lycos, etc.
Index-or directory-based search engines – eg. Yahoo
Multi-or meta-search engines – eg. Search.com, Vivisimo.com
Natural language search engines – eg. Aj.com, ask.co.uk
Resource- or site specific search engines
Another type of search engines classifications are as follows:
Major search engines – Google, Yahoo
News search engines – NewsIndex, InfoGrid
Specialty search engines – Ask Jeeves, Web Help
Kids search engines – AOL Kids only, KidsClick, Yahooligans
Metacrawlers – Dogpile, Metacrawler, Cnet Search
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Multimedia search engines – MP3.com, Audiogalaxy
Regional search engine – Mosaique, Indiainfo.com, Japanese search engines
Search utilities – Copernic, InfoSeek Express, Lexibot.
5.8.3. USES OF SEARCH ENGINES
The display of search engine results comprises of
Number of documents retrieved
Hyperlinked URL
First few lines of the document or a brief summary
Size of the document
Document type such as html, pdf, etc.
Language and Date
Percentage of relevance of each document, etc.
5.8.4. LIMITATIONS OF SEARCH ENGINES
The limitations are
Too many results
Duplicate in nature
Out-dated information
URL not found
Lack of consistency
Search instructions are insufficient
General help menus are not sufficient
5.9 INTERNET TOOLS The Internet offers a number of services to its user. They are
E-Mail – Electronic Mail
FTP – File Transfer Protocol
Usenet News
Telnet – Remote login feature
5.9.1 E_MAIL – ELECTRONIC MAIL
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E_Mail allows sending of information from one computer to another. In other words it allows transmission of text in machine- readable form from one computer to another. The different elements of E_mail are * the address of the both recipient/sender * a subject line and * the message 5.9.1.1 Email addresses: E-mail address contains two parts. They are USERID, DOMAIN. The domain can be classified in two types. They are Organizational domain and Geographic domain. The USERID and DOMAIN is separated by `@â&#x20AC;&#x2122; symbol. For example the E_mail address of MIT and Anna University library are: e.g.: 1. siemit@giasmd01.vsnl.net.in 2. annalib@sirnetm.ernet.in 5.9.2 WHAT IS FTP
FTP, File Transfer Protocol, connects to remote sites and to exchange data between two computers. The FTP allows computer users to download files and store these files on their own hard disk. The files may be any type of data, i.e. programs, text, graphis, photographs. It also allows limited directory-related operations on that site.
5.9.3 TELENET
Telenet connects to remote computer locations as if you are a terminal for that location. Using Telnet one must know the name of the host ie. Either domain name or IP address and login name. For example if any one needs details about INFORMATION ON TECHNOLOGY the domain name and login name is eg. telnet debra.dgbt.doc.ca login name: chat Similarly to connect libraries the domain name and login name is eg. telnet nessie.cc.wwu.edu login name: libs 5.9.4 USENET NEWS
It is the bulletin board service of Internet. It is read and contributed to on a daily basis. Vast amount of communication and interaction can take place over a short period. Mainly it is used for propagation of news.
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There are different News group, organized according to topic. They are
alt.
alternative topics
clair.
Businesses, products
comp.
computer
talk.
Talk and discussion
rec.
recreation
5.9.5 NETWORK NAVIGATION TOOLS:
The different internet navigational tools are
Archie
Gopher
Veronica
Jughead
WWW – World Wide Web –
WAIS – Wide Area Information Server
5.9.5.1 ARCHIE Archie is a program that maintains a list of available files
at FTP sites
around the internet. The contents of information are
- Filename - File size - Type of file - File description
5.9.5.2 GOPHER
It is really guide on the internet. Developed in University of Minnesota. It allows to access databases from all around the internet through menu structure. As name implies it will “go for” the data or topic that is specified. Gopher server can be accessed by typing ID.
Eg. Gopher.msu.edu [Michigan University, USA]
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5.9.5.3 VERONICA Very
Easy
Rodent
Oriented
Netwi6de
Index
to
Computerised Archive
(VERONICA) is used as a tool in conjunction with gopher. The folks at the University of Nevada develop it. It is
basically an extension to gopher (index)
5.9.5.4 JUGHEAD It is another add-on service for gopher. It is very similar to Veronica but narrow your search
5.9.5.5 WORLD WIDE WEB
Wide area hypermedia information retrieval initiative aiming to give universal access to a large universe of documents. The idea was explored in 1960’s, but began to use began in 1989.
The web started as a small hypertext-based network of documents, where the document is distributed over several machines on the internet. At present, the web is truly world wide with web documents literally spanning the globe.
5.9.5.6 INFORMATION SERVICES The other information services that can be used in internet are:
Electronic Discussion Lists and Forums
Electronic journals
Library catalogues
Universities
Computer Wide Information Systems (CWIS)
Database Access on Internet
Data and Software Archives
Companies and
Multiuser Dimensional Games (MUDS)
rganization
CONCLUSION
The use of Internet provides a much-enhanced interface between the user and the information. By use of fixed or moving images, combined with text and voice, information can be provided in forms, which are more easily interpretable, by the recipient. Some of the
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INFORMATION TECHNOLOGY applications listed above may appear frivolous but the impact on may aspects of business and social life will be significant. UNIT QUESTIONS 1. What is Internet 2. Discuss briefly the web resources 3. Explain Web Portal 4. Describe different search engines 5. What are the Internet tools available to-day 6. Write briefly about browsers
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