Introduction of os and types

Understanding Basic Concept of Operating System

1. Introduction of OS
BY
Dr. V. S. PRAKASH
Assistant Professor
Department of Computer Science (UG)
KristuJayantiCollege

2. What is an Operating System?
•Aprogramthatactsasanintermediarybetweenauserofa
computerandthecomputerhardware.
•It’saprogramthatcontroltheexecutionofapplicationprogram
•Actsasaninterfacebetweenapplicationandhardware
•MainObjectivesofOS:
–Convenience,Efficiency,Abilitytosolve
•Operatingsystemgoals:
–Executeuserprogramsandmakesolvinguserproblems
easier.
–Makethecomputersystemconvenienttouse.
•Usethecomputerhardwareinanefficientmanner.

3. Advantages of using Operating System
•Allowsyoutohidedetailsofhardware bycreatingan
EasytousewithaGUI
•Offersanenvironmentinwhichausermayexecuteprograms/applications
•Theoperatingsystemmustmakesurethatthecomputersystemconvenienttouse
•OperatingSystemactsasanintermediaryamongapplicationsandthehardware
components
•Itprovidesthecomputersystemresourceswitheasytouseformat
•Actsasanintermediatebetweenallhardware'sandsoftware'softhesystem
•DisadvantagesofusingOperatingSystem
•IfanyissueoccursinOS,youmayloseallthecontentswhichhavebeenstoredin
yoursystem
•Operatingsystem'ssoftwareisquiteexpensiveforsmallsizeorganizationwhich
addsburdenonthem.ExampleWindows
•Itisneverentirelysecureasathreatcanoccuratanytime

4. History of OS
•Operatingsystemswerefirstdevelopedinthelate1950s
tomanagetapestorage
•TheGeneralMotorsResearchLabimplementedthefirst
OSintheearly1950sfortheirIBM701
•Inthemid-1960s,operatingsystemsstartedtousedisks
•Inthelate1960s,thefirstversionoftheUnixOSwas
developed
•ThefirstOSbuiltbyMicrosoftwasDOS.Itwasbuiltin
1981bypurchasingthe86-DOSsoftwarefromaSeattle
company
•Thepresent-daypopularOSWindowsfirstcameto
existencein1985whenaGUIwascreatedandpairedwith
MS-DOS.

5. Features of OS
•Protected and supervisor mode
•Allows disk access and file systems Device drivers
Networking Security
•Program Execution
•Memory management Virtual Memory Multitasking
•Handling I/O operations
•Manipulation of the file system
•Error Detection and handling
•Resource allocation
•Information and Resource Protection

6. What is a Kernel?
•Thekernelisthecentralcomponentofacomputer
operatingsystems.Theonlyjobperformedbythekernel
istothemanagethecommunicationbetweenthe
softwareandthehardware.
•AKernelisatthenucleusofacomputer.Itmakesthe
communicationbetweenthehardwareandsoftware
possible.WhiletheKernelistheinnermostpartofan
operatingsystem,ashellistheoutermostone.

7. Difference between the OS and Kernel
KERNEL
•Kernelissystemsoftwarewhich
ispartofoperatingsystem.
•kernelprovidesinterfaceb/w
applicationandhardware.
•Itsmainpurposeismemory
management,diskmanagement,
processmanagementandtask
management.
•Alloperatingsystemneeds
kerneltorun.
•Type ofkernelincludes
MonolithicandMicrokernel.
Operating System Concepts
OPERATING SYSTEM
•OperatingSystemisasystem
software.
•OperatingSystemprovidesinterface
b/wuserandhardware.
•Italsoprovidesprotectionand
security.
•Allsystemneedsoperatingsystemto
run.
•Typeofoperatingsystemincludes
singleand multi-user OS,
multiprocessorOS,real-timeOS,
DistributedOS.
•Itisthefirstprogramtoloadwhen
computerbootsup.

8. Computer System Components
1.Hardware–providesbasiccomputingresources(CPU,memory,
I/Odevices).
2.Operatingsystem–controlsandcoordinatestheuseofthe
hardwareamongthevariousapplicationprogramsforthevarious
users.
3.Applicationsprograms–definethewaysinwhichthesystem
resourcesareusedtosolvethecomputingproblemsoftheusers
(compilers,databasesystems,videogames,business
programs).
4.Users(people,machines,othercomputers).

9. Abstract View of System Components

10. Evaluation Of Operating System
•A Major OS evolve over time for no.
of reasons
–h/w upgrade
–New type of h/w
–New services provided
Operating System Concepts

11. Operating System Concepts
Operating System Definitions
•Resource allocator –manages and allocates resources.
•Control program –controls the execution of user programs and
operations of I/O devices .
•Kernel –the one program running at all times (all else being
application programs).

12. Types of OS

14. Operating System Concepts
Simple Batch Systems
•Set of job with similar needs
–Eg: in our class we classify top level, meddle level and low level students
•In batch processing same type of jobs batch together & execute
at a time
•There is no direct interaction between user and computer.

15. Operating System Concepts

16. Advantages OF BOS
•Sharingofbatchsystemformultipleusers.
•Theidletimebatchsystemisveryless.
•Youcanassignspecifictimeforthebatchjobssowhenthe
computerisidleitstartsprocessingthebatchjobsi.e.at
nightoranyfreetime.
•Thebatchsystemscanmanagelargerepeatedworkeasily.
Operating System Concepts

17. Disadvantages OF BOS
•Computeroperatorsmustbetrainedforusing
batchsystems.
•Itisdifficulttodebugbatchsystems.
•Batchsystemsaresometimecostly.
•nodirectinteractionbetweenuserandcomputer
•Ifsomejobtakestoomuchtimei.e.iferror
occursinjobthenotherjobswillwaitfor
unknowntime.
•Nomechanismtoprioritizeprocesses.
•CPUisoftenidle,becausethespeedsofthe
mechanicalI/OdevicesisslowerthanCPU.
Operating System Concepts

18. Examples of BOS
1.Payrollsystem
•Batchsystemsareidealformakingpayrolls.Thesalaries
ofemployeescanbeprintedattheendofmonthbythe
batchsystems.Sothestatementscanbemadeeasyby
usingbatchsystems.
2.Bankstatements
•Attheendofmonththebankmakesstatementsforeach
accountholder.Sothesebankstatementscanbemade
easilybybatchsystemsattheendofmonth.
Operating System Concepts

19. Operating System Concepts
Multiprogrammed Batch Systems
Several jobs are kept in main memory at the same time, and the
CPU is multiplexed among them.

20. Multiprogrammed Batch Systems
•Inthistheoperatingsystem,picksand
beginstoexecuteonejobfrommemory.
•Multiprogrammingsystem,CPUwillnever
beidleandkeepsonprocessing.
Operating System Concepts

21. Operating System Concepts

22. •ADVANTAGES
•It increases CPU utilization.
•It maximizes the total job throughput of a
computer.
•Better Reliability-if one processor breakdown
then other takes its workload.
•DISADVANTAGES
•It must keep track of all kinds of jobs.
•Each system requires large chunks of hard drive
space which cannot be allocated to programs
•Poor CPU usage when only one program is
present in memory.
Operating System Concepts

23. Operating System Concepts
OS Features Needed for Multiprogramming
•I/O routine supplied by the system.
•Memory management –the system must allocate the memory to
several jobs.
•CPU scheduling –the system must choose among several jobs
ready to run.
•Allocation of devices.

24. Operating System Concepts

25. Operating System Concepts
Time-Sharing Systems–Interactive Computing
•ItissimilartoMultiprogrammingsystem.
•Itcanbeusedtohandlemultipleinteractivejob.
•Processortimeissharedamongthemultipleusers.
•TheCPUismultiplexedamongseveraljobsthatarekeptin
memoryandondisk(theCPUisallocatedtoajobonlyifthejob
isinmemory).
•Ajobisswappedinandoutofmemorytothedisk.
•On-linecommunicationbetweentheuserandthesystemis
provided;whentheoperatingsystemfinishestheexecutionof
onecommand,itseeksthenext“controlstatement”notfroma
cardreader,butratherfromtheuser’skeyboard.
•On-linesystemmustbeavailableforuserstoaccessdataand
code.

26. Time-sharing systems
User 5 is in active state-has CPU time
User 6 is in the ready queue
User 1,2,3, are in the waiting state (wait
queue)
Advantages:
1.Many users tasks are processed
simultaneously
2.Cpuidle time is minimized
3.Less response time
4.Resources are shared
Disadvantage:
1.Requires memory mgmt
2. CPU scheduling algorithms
3. Disk management and protection
mgmt
4.May stuck in deadlock.

27. Operating System Concepts

28. Operating System Concepts
Personal-Computer Systems
•Personal computers–computer system dedicated to a single
user.
•I/O devices –keyboards, mice, display screens, small printers.
•User convenience and responsiveness.
•Can adopt technology developed for larger operating system’
often individuals have sole use of computer and do not need
advanced CPU utilization of protection features.

29. Operating System Concepts
Migration of Operating-System Concepts and Features

30. Operating System Concepts

31. Operating System Concepts
Parallel Systems
•Multiprocessor systems with more than one CPU in close
communication.
•Tightly coupled system–processors share memory and a clock;
communication usually takes place through the shared memory.
•Advantages of parallel system:
–Increased throughput
–Economical
–Increased reliability

32. Operating System Concepts
Parallel Systems (Cont.)
•Symmetric multiprocessing (SMP)
–Each processor runs an identical copy of the operating
system.
–Many processes can run at once without performance
deterioration.
–Most modern operating systems support SMP
•Asymmetric multiprocessing
–Each processor is assigned a specific task; master
processor schedules and allocates work to slave processors.
–More common in extremely large systems

33. Operating System Concepts
Symmetric Multiprocessing Architecture

34. Operating System Concepts

35. Real-Time Systems
•Oftenusedasacontroldeviceinadedicatedapplicationsuchas
controllingscientificexperiments,medicalimagingsystems,
Trafficsystem,industrialcontrolsystems,andsomedisplay
systems.
•Well-definedfixed-timeconstraints.
•Hardreal-timesystem(purlyDeterministicsystemandtime
constrainsys)).
–Secondarystoragelimitedorabsent,datastoredinshort-
termmemory,orread-onlymemory(ROM)
–Conflictswithtime-sharingsystems,notsupportedby
general-purposeoperatingsystems.
Eg:Satelitesystem
•Softreal-timesystem
–Limitedutilityinindustrialcontrolorrobotics
–Usefulinapplications(multimedia,virtualreality)requiring
advancedoperating-systemfeatures.
–Systemmeetingdeadlineisnotcompulsory
–Eg:Personalcomputer,audio&videosystem

36. Operating System Concepts
Distributed Systems
•Distribute the computation among several physical processors.
•Loosely coupled system–each processor has its own local
memory; processors communicate with one another through
various communications lines, such as high-speed buses or
telephone lines.
•Advantages of distributed systems.
–Resources Sharing
–Computation speed up –load sharing
–Reliability
–Communications

37. Operating System Concepts
Distributed Systems (Cont.)
•Network Operating System
–provides file sharing
–provides communication scheme
–runs independently from other computers on the network
•Distributed Operating System
–less autonomy between computers
–gives the impression there is a single operating system
controlling the network.

38. Operating System Concepts
http://fivedots.coe.psu.ac.th/~cj/os/slides/sli
de-ppt.html