Introduction to Library & Information Sciences
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Transcript of Introduction to Library & Information Sciences
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Introduction to Library & Information Sciences
Course Code: 5501
Computer Hardware, Software, LAN&WAN
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Historical Background: LANsIn 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.
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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.
Chain Point to Point Star
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Component of LANCommunication 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
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Component of LANDistributed Control
control not limited to one use/computer but distributed among members of the network as democracyFacilities
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
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Transmission Media & TechniquesTerminal to Host TrafficApplications 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.
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Transmission Media & TechniquesBaseband TransmissionModulated TransmissionBroadband Transmission
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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.
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Historical Background: WANsIn 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.
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WAN ConceptsBasics
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)
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WAN ConceptsBasics
Packet Switching:http://www.google.com.pk/imgres?q=packet+switching&um=1&hl=en&biw=1280&bih=816&tbm=isch&tbnid=kCRNwPO2HxcwRM:&imgrefurl=http://www.boerner.net/jboerner/%3Fp%3D7540&docid=uxZ2NrsPsNfH-M&imgurl=http://www.boerner.net/jboerner/wp-content/uploads/2010/01/packet.switching.gif&w=545&h=239&ei=j9YeUqT9JKmU0AW-j4GAAw&zoom=1&ved=1t:3588,r:2,s:0,i:90&iact=rc&page=1&tbnh=148&tbnw=339&start=0&ndsp=13&tx=141&ty=77
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WAN ConceptsBasics
X.25: It is CCITT (Comite Consultatif 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)
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ModemAn 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.
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TerminologyHost (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)
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Logical Structure of a PC
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Input Unit
Keyboard Mouse
Graphic Tablet
Light Pen
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Input Unit
Joystick Graphic Scanners
Microphone
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Mass Storage DevicesDisk Drives
Floppy Diskette Drive
Hard Disk
Floptical Disk Drive
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Mass Storage DevicesCassette Tape & Tape Backup Unit
CD-ROM
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Central Processing Unit (CPU)
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Memory or Primary Storage UnitRead 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)
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Memory or Primary Storage UnitRandom Access Memory (RAM) (Temporary
Storage)System RAMShadow RAMCache RAMVideo RAM (VRAM)
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Output Unit
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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.)
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Information Storage
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Information Storage & RetrievalFunctions in Storage and Retrieval
Data Acquisition (Must be selective)Vocabulary of Terms (must words from
respective document )Description Record Format File Indexes Linkage among recordsRequestsRecord SearchRetrieval and Representation
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Type of SystemDatabase System
A database is an organized collection of dataReference Retrieval System
Reference-retrieval systems store references to documents rather than the documents themselves
DocumentCombine a reference database system with the
ability to retrieve desired document pages, text or image and print or display them
TextFull Text Retrieval
ImageStore and retrieve image
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Storing the DataTopic 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 listsIndexed sequential
too long to find the item
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Storing the DataThree 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
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Qualities in Selection File StructureActivity
How many of the records in a file are accessed whenever the file is processed
VolatilityNumber of records deleted and added to a file.
The records added called insertions, and deleted called deletions
Frequency of AccessHow often we query (access) the file
Volume or SizeNumber of records or number of characters
Response Time Required