Lecture 1.pptx - DISTRIBUTED SYSTEMS Dr. Saddaf Rubab...

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DISTRIBUTED SYSTEMSDr. Saddaf RubabNATIONAL UNIVERSITY OF SCIENCES AND TECHNOLOGY, PAKISTANSPRING, 2020[email protected]
DISTRIBUTED SYSTEMDefinitions1.“A distributed system is a collection of independent computers thatappear to the users of the system as a single computer.”[Tanenbaum]2.“A distributed system is a collection of autonomous computerslinked by a network with software designed to produce anintegrated computing facility.”3.“A system in which hardware or software components located atnetworked computers communicate and coordinate their actionsonly by message passing.” [Coulouris]4.“A system that consists of a collection of two or more independentcomputers which coordinate their processing through the exchangeof synchronous or asynchronous message passing.”
ADVANTAGES OF DISTRIBUTED SYSTEMS OVERINDEPENDENT PCSItemDescriptionData sharingAllow many users access to a common data baseDevice sharingAllow many users to share expensive devicesCommunicationMake human-to-human communication easierFlexibilitySpread the workload over available machines inthe most cost effective way
DISTRIBUTED SYSTEM VS.COMPUTER NETWORKSComputer Network:Computers are connected generally in the same physical location, usingdifferent styles e.g. Token ring, Star, Serial connection, etc. Also called as LAN, Local AreaNetwork.We ll find it in a library, small offices, in the same building, computer labs, cyber cafe's etc,etc. or computer network can be set up in your homeAlso the autonomous computers are explicitly visible (have to be explicitly addressed)Distributed System:Also can be considered as a type of computer network but in a much largescale. Generally called as WAN,Different computers are connected at different physical locations across cities, states, etc.Using distributed systems, various computer programs can be run or executed remotelyirrespective of physical locations, so as to use the more memory and processing power of othercomputers.Existence of multiple autonomous computers is Transparent
DISTRIBUTED SYSTEMS VS. PARALLELCOMPUTINGParallel computingis related to tightly-coupled applications,and is used to achieve one of the following goals:Solve compute-intensive problems faster;Solve larger problems in the same amount of time;Solve same size problems with higher accuracy in thesame amount of time.Distributed computingis related to loosely-coupledapplications, in which the goal (for distributedsupercomputing) is to solve problems otherwise too large orwhose execution may be divided on different components thatcould benefit from execution on different architectures.client-server,peer-to-peer etc.
EXAMPLE 1Automatic banking (teller machine) systemEach ATM has the ability to talk to all other networkedbanksTransactions can be done without regard to where a customeror account isPrimary requirements: security and reliability.

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Term
Fall
Professor
NoProfessor
Tags
Ubiquitous Computing, Computer network, Personal computer, Existence of multiple autonomous computers

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