OPERATING SYSTEMS - INTRODUCTION

This material will be useful for students who are taking operating system course.

1. OPERATING SYSTEMS
Prepared by,
Ms. S. Shanmuga Priya
Senior Assistant Professor,
Department of Computer Science and Engineering
New Horizon College of Engineering
Bangalore
Karnataka

2. •TEXTBOOK:
1.AbrahamSilberschatz,PeterBaerGalvinandGregGagne,
OperatingSystemConcepts,JohnWiley&Sons,Inc.,9th
Edition,2012,ISBN9781118063330.
•REFERENCEBOOK:
1.WilliamStallings,“OperatingSystems:InternalsandDesign
Principles”,EighthEdition,PrenticeHall,2015.
S. Shanmuga Priya, NHCE

3. MODULE 1
INTRODUCTION AND OPERATING
SYSTEM SERVICES
S. Shanmuga Priya, NHCE

4. INTRODUCTION
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5. What is an OperatingSystem?
■Operatingsystemgoals:
•Executeuserprogramsandmakesolvinguserproblemseasier
•Makethecomputersystemconvenienttouse
•Usethecomputerhardwareinanefficientmanner
■OS is a resource allocator
•Manages all resources
•Decides between conflicting requests for efficient and fair resource use
■OS is a control program
•Controls execution of programs to prevent errors and improper use of the
computer
S. Shanmuga Priya, NHCE

6. What is an OperatingSystem?Cont…
■Nouniversallyaccepteddefinition
■Aprogramthatactsasanintermediarybetweenauserofacomputerand
thecomputerhardware
■“Everythingavendorshipswhenyouorderanoperatingsystem”isgood
approximation
•Butvarieswildly
■“Theoneprogramrunningatalltimesonthecomputer”isthekernel.
Everythingelseiseitherasystemprogram(shipswiththeoperatingsystem)or
anapplicationprogram
S. Shanmuga Priya, NHCE

7. ■Computersystemcanbedividedintofourcomponents
•Hardware–providesbasiccomputingresources
CPU,memory,I/Odevices
•Operatingsystem
Controlsandcoordinatesuseofhardwareamongvariousapplicationsandusers
•Applicationprograms–definethewaysinwhichthesystemresourcesare
usedtosolvethecomputingproblemsoftheusers
Wordprocessors,compilers,webbrowsers,databasesystems,videogames
•Users
People,machines,othercomputers
Computer SystemStructure
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8. Four Components of a ComputerSystem
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9. •WhatistheProgram?
•Aprogramcontainsasetofinstructionsandasetofinstructionperform
somespecifictaskfortheuser.
•Aprogramisstoredonsecondarystorage.Forexample,aprogramisstored
onaharddiskinthecomputer.
•Whenweexecutetheprogram,theprogramconvertsintotheprocess.
•Whatistheprocess?
•Theprocessistheprograminexecution.
•Howisaprogramconvertedintotheprocess?
•Theprogramcanbeconvertedintotheprocessbyfollowingthreeactions;
–Compiler
–Linker
–Loader
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10. ComputerStartup
■Bootstrapprogramisloadedatpower-uporreboot
•TypicallystoredinROMorEPROM,generallyknownasfirmware
•Initializesallaspectsofsystem
•Loadsoperatingsystemkernelandstartsexecution
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11. Computer SystemOrganization
■Computer-system operation
•One or more CPUs, device controllers connect through common bus
providing access to shared memory
•Concurrent execution of CPUs and devices competing for memory cycles
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12. S. Shanmuga Priya, NHCE

13. Single vs Multi Processor
System
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14. MULTI PROCESSOR –BLADE
SERVER
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15. DUAL CORE
DUAL CORE DESIGN
Ithascombinedtwoprocessorsandtheir
cachesandcachecontrollersontoasingle
integratedcircuit(siliconchip).
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16. QUICK QUIZ
What is operating system?
a) collection of programs that manages hardware resources
b) system service provider to the application programs
c) link to interface the hardware and application programs
d) all of the mentioned
ANS: d
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17. OPERATING SYSTEM STRUCTURES
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18. SAMPLE QUESITON
Explainmultiprogrammingandtimesharing
operating systems. (8 Marks)
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19. ■Multiprogrammingneededforefficiency
•SingleusercannotkeepCPUandI/Odevicesbusyatalltimes
•Multiprogrammingorganizesjobs(codeanddata)soCPUalwayshasoneto
execute
•Asubsetoftotaljobsinsystemiskeptinmemory
•Onejobselectedandrunviajobscheduling
•Whenithastowait(forI/Oforexample),OSswitchestoanotherjob
■Timesharing(multitasking)islogicalextensioninwhichCPUswitchesjobsso
frequentlythatuserscaninteractwitheachjobwhileitisrunning,creating
interactivecomputing
•Responsetimeshouldbe<1second
•Eachuserhasatleastoneprogramexecutinginmemoryprocess
•IfseveraljobsreadytorunatthesametimeCPUscheduling
•Ifprocessesdon’tfitinmemory,swappingmovestheminandouttorun
•Virtualmemoryallowsexecutionofprocessesnotcompletelyinmemory
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20. Memory Layout for MultiprogrammedSystem
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21. MULTI TASKING
Multiprocessingistheabilityof
anoperatingsystemtoexecute
more than one process
simultaneouslyonamulti
processormachine.
Multitaskingistheabilityofan
operatingsystemtoexecute
more than one task
simultaneouslyonasingle
processormachine.
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22. OPERATING SYSTEM OPERATIONS
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23. SAMPLE QUESTIONS
•Whyisdualmodeoperationsystemrequired?
Explain.(4Marks)
•Defineanoperatingsystem?Whatissystem’s
viewpointofanoperatingsystem?Explainthedual
modeoperationofanoperatingsystem.(10Marks)
•Explaintheoperatingsystemoperationswithsuitable
examples.(10Marks)
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24. •Writeaboutthedualmodeandmulti-mode
operationsinoperatingsystem.(6Marks,
MakeupExam,Jan2018)
SAMPLE QUESTIONS
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25. KERNEL
•DifferenceBetweenKernelandOperatingSystem
•Operatingsystemissystemprogramthatrunsonthecomputertoprovide
aninterfacetothecomputerusersothattheycaneasilyoperateonthe
computer.
•Kernelisalsoasystemprogramthatcontrolsallprogramsrunningonthe
computer.
•Kernelisbasicallyabridgebetweensoftwareandhardwareofthesystem.
•Thebasicdifferencethatdistinguisheskernelandoperatingsystemisthat:
OSisthepackageofdataandsoftwarethatmanagestheresourcesof
thesystem,andthekernelistheimportantprogramintheoperating
system.
Note:Shellistheinterfacethatallowsthe
userstocommunicatewiththekernel.
S. Shanmuga Priya, NHCE

26. ModernOSareInterruptDriven.
OSistriggeredintwoways:
i)SoftwareInterrupts(akaexceptions/traps)
-Causedbyexecutinganinstruction
-Ex:DividebyZeroerror
ii)HardwareInterrupts
-Triggerfromsomehardwaredevice
-Ex:whenadiskblockhasbeenreadorwritten
Aninterruptserviceroutineisprovidedthatisresponsiblefordealingwiththe
interrupt.
Softwareerrororrequestcreatesexceptionortrap
•TRAPisasoftwaregeneratedinterruptcausedeitherbyanerrororbyaspecific
requestfromuserprogramtoanOSservicetobeperformed
Ex:Divisionbyzero
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27. TYPES OF INSTRUCTIONS
NORMAL INSTRUCTIONS PRIVILEGED INSTRUCTIONS
Example
ADD
SUB
Example
Initiate I/O
Switch state or contexts
Load/Save from protected memory
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28. PROBLEMS IN
MULTIPROGRAMMING SYSTEM
•Oneerroneousprogrammightmodifyanother
program,dataofanotherprogram,oreventheOS
itself.
•NeedtoensureproperexecutionofOS
•MustdistinguishbetweenOSCodeandUser-
definedCode
•Withoutprotectionagainstthesesortsoferrors,
eitherthecomputermustexecuteonlyoneprocess
atatimeoralloutputmustbesuspected
•A properlydesigned
operatingsystemmust
ensurethatanincorrect(or
malicious)programcannot
causeotherprogramsto
executeincorrectly.
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29. SOLUTION????
Introduce different modes while
executing instructions
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30. MODES
USER MODE KERNEL MODE
Processorexecutes“normal
instructions”intheuser’s
program
Processorexecutesboth“normal
andprivilegedinstructions”
Processorswitchestokernel
mode,andtheOSperformsa
service
Under user mode
Encountering Privileged Instruction
User-to-kernelswitchsavesthe
informationnecessarytocontinue
theexecutionoftheuserprocess
NOTE:
OperatingSystemisaprocessthatrunsin
kernelmode
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31. HOW/WHEN USER PROCESS
CAN ENTER TO KERNEL
MODE (invoke OS)?
WHEN?? HOW!!!
SYSTEMCALLS
-SoftwareInterrupts
-SetoffunctionswhichtheOSsupportsandauserprocesscouldinvokeany
ofthesystemcallstogetinformationortoaccesshardwarethatarewithinthekernel
space.
-Direct“call”fromauserprogram
-Ex:open()toopenafile,exec()torunanewprogram
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32. QUICK QUIZ
•To access the services of operating system, the
interface is provided by the:
•A.system calls
•B.API
•C.library
•D.assembly instructions
ANS: A
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33. Approach used to differentiate among various modes
of execution
DUAL-MODE OPERATION
-Used in modern OS
-Dual Mode: Helps in protecting the OS from errant
user and from one another
-Implementation : Hardware-based
Dual-Mode Operation Multi-Mode Operation
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34. QUICK QUIZ
•Which one of the following error will be
handle by the operating system?
•A.power failure
•B.lack of paper in printer
•C.connection failure in the network
•D.all of the mentioned
ANS: D
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35. Transition from User to KernelMode
ModeBitBitattachedtothehardwareofthe
computertoindicatethecurrentmode
0Kernel
1User
NeedforbitHelpstodistinguishbetweenUser
TaskorOSTask
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36. How transition takes place?
System Boot Time Kernel Mode (Bit = 0)
OS is loaded and starts user application User Mode (Bit = 1)
On occurrence of trap or interrupt Hardware switches
from user mode to kernel mode
USER PROGRAM

37. App
Operating System
system call
(write to STDOUT)
device
driver
USER PROGRAM
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38. SUMMARY OF DUAL MODE OPERATION
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39. MULTI-MODE OPERATION
•Conceptofmodescanbeextendedbeyondtwo,
requiringmorethanasinglemodebit.
•CPUsthatsupportvirtualizationuseoneofthese
extrabitstoindicatewhentheVirtualMachine
Manager,VMM,isincontrolofthesystem.
•TheVMMhasmoreprivilegesthanordinaryuser
programs,butnotsomanyasthefullkernel.
S. Shanmuga Priya, NHCE

40. How to prevent User Process
taking too much of Kernel Time?
Implement a Timer
Need: Used to prevent user
program from running too
long
PROBLEM???
User Process taking too much of Kernel Time
OS must maintain control over the CPU
S. Shanmuga Priya, NHCE

41. TIMER
IMPLEMENTATION
•Userprogrammustnotstruckinaninfinitelooporfailtocallsystem
servicesandneverreturncontroltotheOS
•Beforethekernelbeginsexecutingusercode,atimerissettogeneratean
interrupt
•Timercanbesettointerruptthecomputerafteraspecifiedperiodoftimeeither
fixed(ex:1/60sec)orvariable(from1msecto1sec)
•Variabletimerisgenerallyimplementedbyafixed-rateclockandacounter
•OSsetsthecounter
•Everytimetheclockticks,thecounterisdecremented
•Whenthecounterreaches0,aninterruptoccurs
•Beforeturningthecontroltotheuser,theOSensuresthatthetimerissetto
interrupt
•Ifthetimerinterrupts,controltransfersautomaticallytotheOS,
treatingtheinterruptasfatal
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42. KERNEL DATA STRUCTURES
OBJECTIVE: To learn about the Operating System
Implementation
-the way the data are structured
in the system
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43. SAMPLE QUESTION(S)
Listoutthevariousdatastructuresthatareused
intheimplementationofanoperatingsystem.
Explainthesamewithanexampleforeach.
Withdescriptionlistoutthekerneldata
structures.(6Marks)(MakeupExam–Jan
2018)
S. Shanmuga Priya, NHCE

44. •Lists
–Singly linked list
–Doubly linked list
–Circularly linked list
•Stacks
–Push
–Pop
•Queues
–Enqueue
–Dequeue
•Trees
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45. COMPUTING ENVIRONMENTS
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46. SAMPLE QUESTIONS
1.Whatismeantbycomputingenvironment?Explainthevariouscomputing
environmentswithsuitableexamples.(10Marks)
2.Writeabriefnotesonthefollowing:(10Marks)
a)MobileComputing
b)DistributedSystems
c)Client-ServerComputing
d)CloudComputing
3.WhatisanOperatingSystem?ExplainReal-TimeOperatingSystemwithit
types.Supportyouranswerwithsuitableexamples.(10Marks)
4.Howtheoperating-systemcomponentsareusedinvarietyofcomputing
environment?(10Marks)
5.Summarizehowoperatingsystemsareusedinavarietyofcomputing
environments.(7Marks,MakeupExam,Jan2018)
S. Shanmuga Priya, NHCE

47. •What ismeantbyComputing
Environment?
–ComputingEnvironmentisacollectionof
computerswhichareusedtoprocessandexchange
theinformationtosolvevarioustypesof
computingproblems.
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48. EVOLUTION
•Non-InteractiveComputingEnvironments
•InteractiveComputingEnvironments
•Real-Time,DistributedandEmbedded
Environments
•ModernComputingEnvironments
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49. •Non-InteractiveComputingEnvironments
–UsersubmitsprogramanddatatoOS;userdoes
notinteractwithcomputation
–Computationsinformofjob
–OSfocusesonefficientuseofresources
•InteractiveComputingEnvironments
–Usermayinteractwithcomputation
–OSdealswithexecutionofprograms
–OSfocusesonprovidingquickresponseto
subrequestsmadetoprocesses
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50. •Real-TimeComputingEnvironment
–Areal-timecomputationhasspecifictimeconstraints
–OSinreal-timeenvironmentensurescomputations
completewithintimeconstraints
•DistributedComputingEnvironment
–Enablesacomputationtouseresourceslocatedinseveral
computersystemsthroughanetwork
•EmbeddedComputingEnvironment
–Computersystemisapartofaspecifichardwaresystem
andrunscomputationthatcontrolthesystem.
–OShastomeetthetimeconstraintsarisingfromthe
natureofthesystembeingcontrolled
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51. S. Shanmuga Priya, NHCE

52. Types of Computing Environment
•Mobile Computing
•Distributed Systems
•Client-Server Computing
•Peer-to-Peer (P2P)
•Virtualization
•Cloud Computing
•Real-Time Embedded Systems
S. Shanmuga Priya, NHCE

53. TRADITIONAL COMPUTING
Traditional Computing
Early days Computing Current Trend Computing
PCsconnectedtoanetwork,terminals
attachedto mainframe or
minicomputersprovidingbatchand
timesharing
-Nowportalsallowingnetworkedand
remotesystemsaccesstosame
resources
-HomeNetworksUsesingle
system,withmodems,withfirewalls
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54. MOBILE COMPUTING
•Referstocomputingonhandheldsmartphonesandtablet
computers.
•PhysicalFeatures
–PortableandLightweight
–Historically,comparedwithdesktopandlaptop
•UniqueFeatures
–Additionalbuilt-insensors,suchasGPS(GlobalPositioning
System)Chipsusefulfornavigation
•Example,tellinguserswhichwaytowalkordriveorperhapsdirecting
themtonearbyservices,suchasrestaurants.
–Accelerometers
•Allowsamobiledevicetodetectitsorientationwithrespecttothe
groundandtodetectcertainotherforces,suchastiltingandshaking
•Usedingaming
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55. •Comparedwithdesktopandlaptop:
–Limitedin
•StorageCapacity,
•MemoryCapacity,and
•ComputingPower
–GaveupScreenSize
•Generallyuses
–SmallerandSlowerProcessorswithfewerprocessing
cores(thanfoundintraditionalPCs),thatconsumeless
batterypowerandproducelessheat.
MOBILE COMPUTING Cont…
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56. •TypicallyconnecttotheInternetusingwirelessnetworking
(IEEE802.11)orcellulartelephonetechnology
•Today,mobilesystemsareusednotonlyfore-mailandweb
browsingbutalsofor
–playingmusicandvideo,
–readingdigitalbooks,
–takingphotos,and
–recordinghigh-definitionvideo
•Twooperatingsystemscurrentlydominatemobilecomputing:
AppleiOSandGoogleAndroid.
MOBILE COMPUTING Cont…
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57. DISTRIBUTED SYSTEMS
•DistributedSystemsconsistof
–multiple,possiblyheterogeneous,
computersconnectedtogetherviaa
networkandcooperatinginsome
way,form,orfashion.
–Dependsonnetworkingfortheir
functionality
•Mayvaryinprotocolsused,
distancesbetweennodes,transport
•TCP/IPisthecommonnetwork
protocolused
•NETWORK isacommunicationpath
betweentwoormoresystems
•Distributethecomputationamong
severalphysicalprocessors.
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58. Networkischaracterizedbasedonthedistancebetweentheir
nodes
i)LAN–LocalAreaNetwork,connectscomputeswithina
room,afloor,orabuilding
ii)MAN–MetropolitanAreaNetwork,linksbuildings
withinacity
iii)WAN–WideAreaNetwork,linksbuildings,cities,or
countries
iv)PAN-PersonalAreaNetwork,suchastheBluetooth
connectionbetweenyourPC,phone,headset,car,etc.
DISTRIBUTED SYSTEMS Cont…
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59. •NETWORK OPERATING SYSTEM
OSthatprovidesfeaturessuchassharingofresources
–Shared resources may include:
»Files,
»CPU Cycles,
»RAM,
»Printers etc.,
Access to a shared resource increases:
»Computation Speed,
»Functionality,
»Data Availability, and
»Reliability
•DISTRIBUTEDOPERATINGSYSTEM
-DifferentOScommunicatecloselyenoughtoprovidetheillusion
thatonlyasingleOScontrolsthenetwork
DISTRIBUTED SYSTEMS Cont…
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60. •Client/Servercomputingisacomputingmodel
inwhichclientandservercomputers
communicatewitheachotherovera
network.
•Isaformofspecializeddistributedsystem.
CLIENT-SERVER COMPUTING
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61. CLIENT-SERVER COMPUTING Cont…
•ClientAclientisacomputingdevicethat
initiatescontactwithaserverinorderto
makeuseofashareableresource
•ServerAservertakesrequestsfromclient
computersandsharesitsresources,
applicationsand/ordatawithoneormore
clientcomputersonthenetwork
–Example:
•Web-Server
•DatabaseServer
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62. CLIENT-SERVER COMPUTING Cont…
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63. •Serversystemscanbebroadlycategorizedascomputeserversandfile
servers:
•Compute-ServerSystem
–ClientSendarequesttoperformanaction(forexample,readdata).
–ServerExecutestheactionandsendstheresponse(result)tothe
client.
–Example:Serverrunningadatabasethatresponsetotheclientrequests
forthatdata
•File-ServerSystem
–providesafile-systeminterfacewhereclientscan
•Create,
•Update,
•Read,and
•Deletefiles.
–Example:WebServerthatdeliversfilestoclientsrunningweb
browsers.
CLIENT-SERVER COMPUTING Cont…
Problem: Server Bottleneck
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64. FACEBOOK SERVER
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65. S. Shanmuga Priya, NHCE

66. PEER –TO –PEER (P2P) COMPUTING
•Anothermodelofdistributedsystem
•P2Pdoesnotdistinguishclientsandservers
•Insteadallnodesareconsideredpeers,mayeachactasclient,serveror
both
•NodemustjoinP2Pnetwork,toparticipateinP2Psystem
•Howanodecanjoin?
•Registersitsservicewithcentrallookupserviceonnetwork,or
•Broadcastrequestforserviceandrespondtorequestsforservicevia
discoveryprotocol
•ExamplesincludeNapsterandGnutella
•Advantage
–Eliminatesserverbottleneckthatexistsinclient-serversystem
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67. Skypeusesacentralservertolocateadesiredpeer,andthen
furthercommunicationispeertopeer
Skypeusesahybridpeer-to-peerapproach.Itincludesa
centralizedloginserver,butitalsoincorporatesdecentralized
peersandallowstwopeerstocommunicate.
PEER –TO –PEER (P2P) COMPUTING Cont…
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68. VIRTUALIZATION
•TerminologiesUsed:
–Host
–Guest
•Allowsoneormore"guest"operatingsystemstorunonvirtualmachineshostedby
asinglephysicalmachineandthevirtualmachinemanager
•Usefulforcross-platformdevelopmentandsupport
•Forexample,astudentcouldrunUNIXonavirtualmachine,hostedbyaVirtual
MachineManager(VMM)onaWindowsbasedpersonalcomputer
•Example:Thestudentwouldhavefullrootaccesstothevirtualmachine,andifit
crashed,theunderlyingWindowsmachineshouldbeunaffected
•SystemCallshavetobecaughtbytheVMMandtranslatedinto(different)system
callsmadetotherealunderlyingOS
•Disadvantage:CanslowdownprogramthathavetorunthroughtheVMMS. Shanmuga Priya, NHCE

69. ThatapplicationranoneormoreguestcopiesofWindowsorothernativex86
operatingsystems,eachrunningitsownapplications.
Windowswasthehostoperatingsystem,andtheVMwareapplicationwas
thevirtualmachinemanagerVMM.TheVMMrunstheguestoperating
systems,managestheirresourceuse,andprotectseachguestfromtheothers.
VMware
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70. CLOUD COMPUTING
•Cloudcomputingisatypeofcomputingthatdelivers
–computing,
–storage,and
–evenapplicationsasaserviceacrossanetwork
•Logicalextensionofvirtualization
•Example:Dropbox,Gmail
–AmazonElasticComputeCloud(EC2)facility
•Hasthousandsofservers,
•MillionsofVirtualMachines,and
•Petabytesofstorageavailableforusebyanyoneonthe
Internet.
•Userspaypermonthbasedonhowmuchofthose
resourcestheyuse.
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71. •TypesofCloudComputing
–PublicCloud-Availabletoanyonewillingtopayforthe
service.
–PrivateCloud-Runbyacompanyforinternaluseonly.
–HybridCloud-Acloudwithbothpublicandprivate
components.
–SoftwareasaService(SaaS)-Applicationssuchasword
processorsavailableviatheInternet(Ex:GoogleApps)
–PlatformasaService(PaaS)-Asoftwarestackavailable
forapplicationuse,suchasadatabaseserver
–InfrastructureasaService(IaaS)-Serversorstorage
availableontheInternet,suchasbackupservers,photo
storage,orfilestorage.
–Serviceprovidersmayprovidemorethanonetypeof
service
CLOUD COMPUTING Cont…
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72. Cloudsmaycontain
-Thousandsofphysicalcomputers,
-Millionsofvirtualones,and
-Petabytesoftotalstorage
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73. REAL-TIME EMBEDDED SYSTEM
•Areal-timesystemisusedwhenrigidtime
requirementshavebeenplacedonthe
operationofaprocessorortheflowofdata;
thus,itisoftenusedasacontroldeviceina
dedicatedapplication.
•Theytendtohaveveryspecifictasks.
•Embeddedsystemsalmostalwaysrunreal-
timeoperatingsystems.
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74. Real-Time Embedded System Applications
Medical System
Vehicle System
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75. REAL-TIME EMBEDDED SYSTEM Cont…
•When to use Real-Time System?
-Used when rigid time requirements have been placed on the
operation of a processor or the flow of data;
-It is often used as a control device in a dedicated application.
•Where does data comes from? Data comes from sensors
•What do real-time system do with data? Computer must analyze the
data and possibly adjust controls to modify the sensor inputs.
TYPES
Hard Real-Time System Soft Real-Time System
Followsstricttimeconstraints,elseleads
tocatastrophiccauses,likepermanent
lossofdata
Ex: Air Bag System, Anti-Lock Brake
System
Missing time constraint is acceptable
Ex: Automatic Teller Machine (ATM)
Audio-Video Playback System
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76. •Applicationsandexamplesofreal-timesystems:
-appearingaspartofourcommercial,government,military,medical,
educational,andculturalinfrastructures
•Includedare
VehicleSystems-forautomobiles,subways,aircraft,railways,andships
TrafficControl-forhighways,airspace,railwaytracks,andshipping
lanes
MedicalSystems-forradiationtherapy,patientmonitoring
MilitaryUses-suchasfiringweapons,tracking,andcommandand
control
ManufacturingSystemswithrobots
HouseholdSystems-formonitoringandcontrollingappliances
REAL-TIME EMBEDDED SYSTEM Cont…
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77. SYLLABUS –MODULE 1
•Introduction
BasicsofOperatingSystems:Definition-OperatingSystemstructure;
OperatingSystemoperations–Dual-ModeandMulti-Mode;Kernel
DataStructure–Lists,Stacks,andQueues,Trees;Computing
Environments–MobileComputing,DistributedSystems,Client-Server
Computing,Peer-to-Peer,Virtualization,CloudComputing,Real-Time
EmbeddedSystems.
S. Shanmuga Priya, NHCE