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Introduction to Library & Information Sciences. Course Code: 5501. Computer Hardware, Software, LAN&WAN. Historical Background: LANs.

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Introduction to Library & Information Sciences

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Introduction to library information sciences

Introduction to Library & Information Sciences

Course Code: 5501

Computer Hardware, Software, LAN&WAN

Historical background lans

Historical Background: LANs

  • In 1970s a new trend began in computing i.e., shifting from large centralized mainframes occupying a room, towards physically smaller, yet higher performance minicomputers. The first microprocessor system was introduced around 1971.

  • Microprocessor: An integrated circuit that contains all the functions of a central processing unit of a computer.

Local area network lan

Local Area Network (LAN)

  • LAN opened up the possibility of attaining advantages of workstations, without losing the centralized mainframe systems. Information could flow between individual workstations at speeds which, to a large extent, hid the fact that users were not working on a single system.

    ChainPoint to PointStar

Component of lan

Component of LAN

  • Communication Medium

    Copper wire, optical fiber, radio link etc.

  • Bandwidth

    capacity of a medium to carry data (measured in mega bits per second)

  • Multi-addressing or Broadcasting

    addresses could be of other users such as printer, scanner etc

Component of lan1

Component of LAN

  • Distributed Control

    control not limited to one use/computer but distributed among members of the network as democracy

  • Facilities

    user can enter a job from any computer connected to LAN i.e., exchange files

  • Range

    communication medium limits it to premises within a building or within an area

Transmission media techniques

Transmission Media & Techniques

  • Terminal to Host Traffic

  • Applications for graphic images is Megabits per second

    The medium chosen will have to accommodate current as well as future requirements over the system’s expected life time of 15 years or more.

Transmission media techniques1

Transmission Media & Techniques

  • Baseband Transmission

  • Modulated Transmission

  • Broadband Transmission

Wide area network wans

Wide Area Network (WANs)

  • WANs maybe an extension of a LAN, but involve distances in the range of thousands of miles, requiring media different from LANs and also different hardward/software.

Historical background wans

Historical Background: WANs

  • In 1960s ARPA (now Defense Advanced Research Projects Agency of US Department of Defense – DARPA), began research on subject of computer networks by providing grants to computer science department at many US Universities and few private corporations. This research led to an experimental four node network that went on air in Dec 1969 known as ARPANET.

Wan concepts

WAN Concepts

  • Basics

    • Circuit Switching (Mode of transmitting information between two points)

    • Dial up Line (circuit switched line operable by dialing a number)

    • Leased Line (Radio channel or a satellite link etc)

Wan concepts1

WAN Concepts

  • Basics

    • Packet Switching:,r:2,s:0,i:90&iact=rc&page=1&tbnh=148&tbnw=339&start=0&ndsp=13&tx=141&ty=77

Wan concepts2

WAN Concepts

  • Basics

    • X.25: It is CCITT (ComiteConsultatif International Telegraphique et Telephonique) standard describing how communication devices package data into packets and how these packets are routed.

    • Another X.75 defines how two packet switched networks communicate.

    • PDNs (Public Data Networks): Different communications protocols to talk to each other and transfer bulk data.

      • SVC (Switched Virtual Circuit) (Temporary logical path)

      • PVC (Permanent Virtual Circuit) (Permanent)



  • An electronic device that convert computer’s digital signals into electrical audio signals, such that they can be transmitted over telephone lines.

  • Telephone lines were designed and installed for analog speech communication, however, computer speak digital, therefore, a modem is required.



  • Host (Computer providing network services)

  • Node (Unique identification)

  • Account (name, password)

  • E. mail (Electronic Mail)

  • Mailbox (Special Account)

  • FTP (File Transfer Protocol – Exchange Files b/w 2 computers)

  • TELNET (a user on one computer to log on to another computer that is part of the same network)

  • Remote Login (Login a remote computer)

  • News Group (Electronic forum of discussion)

  • Mailing List (facility to receive messages by email)

Logical structure of a pc

Logical Structure of a PC

Input unit

Input Unit



Light Pen

Graphic Tablet

Input unit1

Input Unit

Graphic Scanners



Mass storage devices

Mass Storage Devices

  • Disk Drives

    • Floppy Diskette Drive

    • Hard Disk

    • Floptical Disk Drive

Mass storage devices1

Mass Storage Devices

  • Cassette Tape & Tape Backup Unit

  • CD-ROM

Central processing unit cpu

Central Processing Unit (CPU)

Memory or primary storage unit

Memory or Primary Storage Unit

  • Read only Memory (ROM) (Permanent Storage)

    • ROM

    • PROM (Programmable ROM)

    • EPROM (Erasable Programmable ROM))

    • EEPROM (Electrically Erasable Programmable ROM)

  • Random Access Memory (RAM) (Temporary Storage)

    • SRAM (Static RAM)

    • DRAM (Dynamic RAM)

    • SIMM (Single In-Line Memory Module)

    • SIP (Single In-Line Package)

Memory or primary storage unit1

Memory or Primary Storage Unit

  • Random Access Memory (RAM) (Temporary Storage)

    • System RAM

    • Shadow RAM

    • Cache RAM

    • Video RAM (VRAM)

Output unit

Output Unit

Computer program software

Computer Program (Software)

  • DISK Operating System (DOS)

  • Utilities (assists in operation of computer but does not perform main work i.e., detect or clean virus)

  • Applications Software (applications software or applications program is the one that performs useful work, not related to computer itself i.e., MS Office, Corel Draw etc.)

Information storage

Information Storage

Information storage retrieval

Information Storage & Retrieval

  • Functions in Storage and Retrieval

    • Data Acquisition (Must be selective)

    • Vocabulary of Terms (must words from respective document )

    • Description

    • Record Format

    • File

    • Indexes

    • Linkage among records

    • Requests

    • Record Search

    • Retrieval and Representation

Type of system

Type of System

  • Database System

    • A database is an organized collection of data

  • Reference Retrieval System

    • Reference-retrieval systems store references to documents rather than the documents themselves

  • Document

    • Combine a reference database system with the ability to retrieve desired document pages, text or image and print or display them

  • Text

    • Full Text Retrieval

  • Image

    • Store and retrieve image

Storing the data

Storing the Data

  • Topic treats the physical organization of data in terms of speed of access, storage requirements, and flexibility of access.

  • Three major types of file organization

    • Sequential

      • can produce easily, but they have a slower access time

    • Random access

      • fast access time, but cannot easily produce sequential lists

    • Indexed sequential

      • too long to find the item

Storing the data1

Storing the Data

  • Three major types of file organization

    • Sequential

      • Data is searched by key

    • Random access

      • Key is used to compute the address of a storage location.

    • Indexed sequential

      • Index is made up of the key and address at which the data bearing that key is stored

Qualities in selection file structure

Qualities in Selection File Structure

  • Activity

    • How many of the records in a file are accessed whenever the file is processed

  • Volatility

    • Number of records deleted and added to a file. The records added called insertions, and deleted called deletions

  • Frequency of Access

    • How often we query (access) the file

  • Volume or Size

    • Number of records or number of characters

  • Response Time Required

  • Login