operating system basics including mac os

operating systems basic

1. Department of
Computer Science and Engineering
OPERATING SYSTEMS
School of Computing
Vel Tech Rangarajan Dr. SagunthalaR&D Institute of
Science and Technology
Faculty Name : P.GIRIJA
UNIT -1

2. Department of Computer Science and Engineering
Course Content
2
UNIT I OPERATING SYSTEMS OVERVIEW 9
Operating system overview: Objectives
Functions
Computer System Organization
Operating System Structure
Operating System Operations
System Calls
System Programs

3. Department of Computer Science and Engineering
Learning Resources
3
and Project
Management
(SEPM)
Text Books
1.AbrahamSilberschatz,PeterBaerGalvinandGregGagne,“OperatingSystemConcepts”,9th
Edition,JohnWileyandSonsInc.,2012.
2.RichardPetersen,“Linux:TheCompleteReference”,6thEdition,TataMcGraw-Hill,2008.
Reference Books
1.AndrewS.Tanenbaum,“ModernOperatingSystems”,4thEdition,PrenticeHall,Wesley,
2014.
2.WilliamStallings,“OperatingSystems–InternalsandDesignPrinciples”,7thEdition,
PrenticeHall,2011.
3.HarveyM.Deitel,“OperatingSystems”,7thEdition,PrenticeHall,2003.
4.DMDhamdhere,“OperatingSystems:AConcept-BasedApproach”,2ndEdition,Tata
McGraw-HillEducation,2007.
5.CharlesCrowley,“OperatingSystems:ADesign-OrientedApproach”,TataMcGrawHill
Education”,1996.
Digital Resources
1.http://www.tutorialspoint.com/operating_system/
2.http://www.mu.ac.in/myweb_test/MCA%20study%20material/OS%20-%20PDF.pdf
3.http://codex.cs.yale.edu/avi/os-book/OS8/os8c/slide-dir/PDF-dir/ch2.pdf
4.http://www.freebookcentre.net/CompuScience/Free-Operating-Systems-Books-download.html
/

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Why you need to learn os?
4
and Project
Management
(SEPM)
OSisakeypartofacomputersystem
Itisthemostimportantsoftwarethatrunsonacomputer.It
managesthecomputer’s
Memory
Processes
Software
Hardware.
Italsoallowsyoutocommunicatewiththecomputer.

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•AnOperatingSystem(OS)isaninterfacebetweenacomputer
userandcomputerhardware.
•Anoperatingsystem(OS)issystemsoftwarethatmanages
computerhardwareandsoftwareresources,andprovidescommon
servicesforcomputerprograms.
•Anoperatingsystemisaprogramthatactsasaninterfacebetweentheuserand
thecomputerhardwareandcontrolstheexecutionofallkindsofprograms.
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OPERATING SYSTEMS -Definition

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7. Department of Computer Science and Engineering

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Memory Management
Processor Management
Device Management
File Management
Security
Control over system performance
Job accounting
Error detecting codes
Coordination between other software and users

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•ExecuteuserProgram&makesolvinguserproblemseasier.
•MakethecomputerSystemconvenienttouse.
•Usethecomputerhardwareinanefficientmanner.
Goals of an operating System

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•Hardware
•Operating system
•Application programs
•Users
Four main components of Computer

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•Hardware–providesbasiccomputingresources
•CPU,memory,I/Odevices
•Operatingsystem
•Controlsandcoordinatesuseofhardwareamongvariousapplicationsandusers
•Applicationprograms
•Definethewaysinwhichthesystemresourcesareusedtosolvethecomputing
problemsoftheusers
•Wordprocessors,compilers,webbrowsers,databasesystems,videogames
•Users
•People,machines,othercomputers
Computer system can be divided into four components:

12. Department of Computer Science and Engineering
Views of Operating Systems

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•Bootstrapprogramisloadedatpower-uporreboot
•TypicallystoredinROMorEPROM,generallyknownas
firmware
•Initializesallaspectsofsystem
•Loadsoperatingsystemkernelandstartsexecution
Computer Start up

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Computer System Organization

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Computer System Organization
•Computer-systemoperation
•OneormoreCPUs,devicecontrollersconnectthroughcommon
busprovidingaccesstosharedmemory
•I/OdevicesandtheCPUcanexecuteconcurrently
•Eachdevicecontrollerisinchargeofaparticulardevicetype
•Eachdevicecontrollerhasalocalbuffer
•CPUmovesdatafrom/tomainmemoryto/fromlocalbuffers
•I/Oisfromthedevicetolocalbufferofcontroller

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•DevicecontrollerinformsCPUthatithasfinisheditsoperationby
causinganinterrupt
•Interrupttransferscontroltotheinterruptserviceroutinegenerally,
throughtheinterruptvector,whichcontainstheaddressesofallthe
serviceroutines
•Interruptarchitecturemustsavetheaddressoftheinterrupted
instruction
•Atraporexceptionisasoftware-generatedinterruptcausedeitherby
anerrororauserrequest
•Anoperatingsystemisinterruptdriven
INTERRUPTS

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INTERRUPTS

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•The OS preserves the state of the CPU by storing registers and the
program counter
•Determines which type of interrupt has occurred:
polling
•The interrupt controller polls (send a signal out to) each device to
determine which one made the request
vectored -interrupt system
•Separate segments of code determine what action should be taken
for each type of interrupt
INTERRUPT HANDLING

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INTERRUPT TIMELINE

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STORAGE HIERARCHY

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•StorageistheonlyoneofmanytypesofI/Odeviceswithinacomputer.
•AlargeportionofOScodeisdedicatedtomanagingI/O
•Becauseofitsimportanceofreliability&performance.
•ComputersystemconsistsofCPU&multipledevicescontrollersthrough
commonbus.
•Eachdevicecontrollerisinchargeofaspecifictypesofdevices.
I/O STRUCTURE

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DEVICECONTROLLER
•Maintainslocalbufferstorage&setofSpecialpurposeregisters.
DEVICEDRIVER
•OShaveadevicedriverforeachdevicecontroller.
•Devicedriverunderstandsthedevicecontroller&givesuniforminterface
totherestoftheOS.
•Devicecontrollertransfersblocksofdatafrombufferstoragedirectlyto
mainmemorywithoutCPUintervention
•Onlyoneinterruptisgeneratedperblock,ratherthantheoneinterruptper
byte.
I/O STRUCTURE

23. Department of Computer Science and Engineering
DEVICECONTROLLER
CPU
ADDRESS BUS
DATA BUS
Registers Registers
LOCAL BUFFERS
MAIN MEMORY

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•TostartanIOoperations,devicedriverloadstheappropriateregisterswithin
thedevicecontroller.
•Devicecontrollerinturnsexaminesthecontentoftheseregistersto
determinewhatactiontotake.
•Thecontrollerstartsthetransferofdatafromthedevicetoitslocalbuffer.
•Oncethetransferofdataiscomplete,thedevicecontrollerinformsthedevice
driverviaaninterruptthatithasfinisheditsoperations.
•DevicedriverthenreturnthecontroltoOS.
Issue:
•ThisformofinterruptdrivenIOisfineformovingsmallamountsofdata.
•Butcanproducehighoverheadwhenusedforbulkdatamovement.
Working of I/O operations

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DMA(DIRECT MEMORY ACCESS)
•Tosolvetheaboveproblem,DMAisused.
•Aftersettingupbuffers,pointers&countersforIOdevices,the
devicecontrollertransfersanentireblockofdatadirectlytoorfrom
itsownbufferstoragetomemorywithoutinterventionofCPU.
•Onlyoneinterruptisgeneratedperblock,totellthedevicedriver
thattheoperationhascompleted.
•Whilethedevicecontrollerisperformingtheseoperations,CPUis
availabletoaccomplishotherworks.
Working of I/O operations

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How a Modern Computer Works

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OPERATING SYSTEM STRUCTURE
COMMONALITIES
MULTIPROGRAMMING
MULTI TASKING
(TIME SHARING)

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•Multiprogramming(Batchsystem)neededforefficiency
•CapabilityofrunningmultipleprogramsbytheCPU.
•ItincreasesCPUutilizationbyorganizingjobs(codeanddata)soCPU
alwayshasonetoexecute.
•Singleprogram(user)cannotkeepCPUandI/Odevicesbusyatalltimes
•Asubsetoftotaljobsinsystemiskeptinmemory
•Onejobselectedandrunviajobscheduling
•Whenithastowait(forI/Oforexample),OSswitchestoanotherjob
OPERATING SYSTEM STRUCTURE
JOB
1
J
JOB
3
JOB
2
JOB
4
JOB POOL

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•Timesharing(multitasking)islogicalextensioninwhichCPU
•switchesoccurssofrequentlythatuserscaninteractwitheachjobwhileit
isrunning,creatinginteractivecomputing
•Responsetimeshouldbe<1second
•Eachuserhasatleastoneprogramexecutinginmemoryprocess
•IfseveraljobsreadytorunatthesametimeCPUscheduling
•Ifprocessesdon’tfitinmemory,swappingmovestheminandoutto
run
•Virtualmemoryallowsexecutionofprocessesnotcompletelyin
memory
OPERATING SYSTEM STRUCTURE

30. Department of Computer Science and Engineering
•UNIXisapowerfulOperating
Systeminitiallydevelopedby
KenThompson,Dennis
RitchieatAT&T Bell
laboratoriesin1970.

31. Department of Computer Science and Engineering
•Features of UNIX Operating System

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•Multitasking:AUNIXoperatingsystemisamultitaskingoperatingsystemthatallowsyou
toinitiatemorethanonetaskfromthesameterminalsothatonetaskisperformedasa
foregroundandtheothertaskasabackgroundprocess.
•Multi-user:UNIXoperatingsystemsupportsmorethanoneusertoaccesscomputer
resourceslikemainmemory,harddisk,tapedrives,etc
•Portability:ThisfeaturemakestheUNIXworkondifferentmachinesandplatformswith
theeasytransferofcodetoanycomputersystem.
•FileSecurityandProtection:Beingamulti-usersystem,UNIXmakesspecialconsideration
forfileandsystemsecurity.
•Communication:InUNIX,communicationisanexcellentfeaturethatenablestheuserto
communicateworldwide.Itsupportsvariouscommunicationfacilitiesprovidedusingthe
writecommand,mailcommand,talkcommand,etc.
•OpenSource:UNIXoperatingsystemisopensourceitmeansitisfreelyavailabletoall
andisacommunity-baseddevelopmentproject.
•Accounting:UNIXkeepsanaccountofjobscreatedbytheuser.
•UNIXToolsandUtilities:likecompiler,interpreter...etcforunixgrep,sed,awketc...

33. Department of Computer Science and Engineering
•The structure of Unix OS Layers are as follows:

34. Department of Computer Science and Engineering
•Interruptdriven(hardwareandsoftware)
•Hardwareinterruptbyoneofthedevices
•Softwareinterrupt(exceptionortrap):
•Softwareerror(e.g.,divisionbyzeroorinvalidmemoryaccess)
•Requestforoperatingsystemservice
•ForeachtypeofinterruptseparatesegmentofcodeintheOS
determinewhatactionshouldbetaken.
•ISR[InterruptServiceRoutine]providedtodealwithinterrupt.
•AproperlydesignedOSensurethatanincorrectormaliciousprogramcannot
causeotherprogramstoexecuteincorrectly.
Operating-System Operations

35. Department of Computer Science and Engineering
•Dual-modeoperationallowsOStoprotectitselfandothersystemcomponents
2 MODES OF OPERATIONS
DUAL MODE & MULTI MODE OPERATIONS
User mode
kernelmodeorSupervised
modeorprivilegedmode.

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•Modebit
•Addedtohardwareofthecomputer.
•Toindicatethecurrentmode
•Kernel(0)
•User(1)
•Systemexecutingauserapplication–Usermode.
•UserApplicationrequestaservicefromOS(viaSystemcall).
•Systemmusttranslatefromusermodetokernelmodetofulfillthe
request.
DUAL MODE & MULTI MODE OPERATIONS

37. Department of Computer Science and Engineering
DUAL MODE & MULTI MODE OPERATIONS

38. Department of Computer Science and Engineering
•Hardwarestartsinkernelmode.
•OSisthenloaded&startsuserapplicationinusermode.
•Whenevertraporinterruptoccurs,thehardwareswitches
fromusermodetokernelmode.
•OSgainsthecontrolofcomputerinkernelmode.
•Thesystemalwaysswitchestousermodebeforepassing
controltoauserprogram.
System Boot

39. Department of Computer Science and Engineering
•Thehardwareallowstheseinstructionstobeexecutedonly
inkernelmode.
•Example:
•Theinstructionstoswitchtokernelmode.
•I/Ocontrol
•Timermanagement
•Interruptmanagement
Privileged Instructions(System Calls)

40. Department of Computer Science and Engineering
•CPUusesmorethanonebittoset&testthemode.
•CPUsupportsvirtualizationfrequentlyhaveaseparatemodeto
indicatewhentheVirtualMachineManager(VMM)&the
virtualizationmanagementsoftwareVMsisincontrolofthe
system.
•VMMhasmoreprivilegesthanuserprocessesbutfewerthanthe
kernel.
•Example
•Intel64familyofCPUsupports4privilegedlevels&virtualization
butdoesnothaveseparatemodeforvirtualization.
Beyond two modes[multi mode operations]

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•Providestheuserprogramtoasktheoperatingsystemtoperformtasks
reservedfortheOS.
•Itisinvokedinvarietyofways.
•Usuallyittakestheformofatraptoaspecificlocationintheinterruptvector.
•Trapexecutedbyagenerictrapinstruction,syscallinstructiontoinvokea
systemcall.
•Whensystemcallisexecuted,hardwaretreateditassoftwareinterrupt.
•Controlpassesthroughinterruptvectortoaserviceroutine&modebitisset
tokernelmode.
•Thekernelexaminestheinterruptinginstructiontodeterminewhatsystem
callhasoccurred.
SYSTEM CALL

42. Department of Computer Science and Engineering
•Aparameterindicateswhattypeofservicetheuserprogramis
requesting.
•Additionalinformationpassedinregisters,onthestackorinmemory.
•Kernelverifiesthatparametersarecorrect&legal,executetherequest
&returnscontroltotheinstructionfollowingthesystemcall.
Nobitmode
•Lackofhardwaresupportedwithdualmodecauseseriousshort
comings.
Example
•MSDOS–IntelArchitecturehasnomodebit&nodualmode.
ExampleforDualmode
•Windows10,UNIX,Linux
SYSTEM CALL

43. Department of Computer Science and Engineering
•ProgramminginterfacetotheservicesprovidedbytheOS.
•Typicallywritteninahigh-levellanguage(CorC++)
SYSTEM CALLS
User Mode
Kernel
Mode

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Examples -SYSTEM CALLS
•Systemcallsequencetocopythecontentsofonefiletoanotherfile

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•Acquire input File name:
•To enter the file name
•2 ways are there
•Through keyboard
•Mouse
•Frequently system execute thousands of system calls per second.
Examples -SYSTEM CALLS

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•Specifiessetoffunctionsthatareavailabletoanapplicationprogrammer,
includingparameterspassedtoeachfunctions&returnvaluesthe
programmercanexpect.
•Mostlyaccessedbyprogramsviaahigh-levelApplication
ProgrammingInterface(API)ratherthandirectsystemcall.
•
SYSTEM CALLS -APIs

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Examples of Standard APIs

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•WhyapplicationprogrammerpreferprogrammingaccordingtoAPIthan
invokingsystemcalls?
•Programportability
•ApplicationprogrammerdesignaprogramusinganAPIcanexpecther
programtocompile&runonanysystemthatsupportsthesameAPI.
SYSTEM CALLS -APIs

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•Manyprogramminglanguagesprovidesasystemcallinterface.
•Itservesasthelinktosystemcallsmadeavailablebyoperatingsystem.
•ItinterceptsfunctioncallsintheAPI&invokesthenecessarysystemcallwritten
theOS.
•Anumberisassociatedwitheachsystemcall.
•Itmaintainsatableindexedaccordingtothesenumbers.
•ItinvokesintendedsystemcallinOSkernel&returnsstatusofthesystemcalls&
anyreturnvalues.
•Thecallerneedknownothingabouthowthesystemcallisimplemented.
•JustneedonlyobeytheAPI&understandwhatOSwilldoasaresultofsystem
call.
•MostdetailofOSinterfacehiddenfromprogrammerbyAPI.
•Managedbyruntimesupportlibrary(setoffunctionsbuiltintolibrariesincluded
withcompiler)
SYSTEM CALLS interface

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API –System Call –OS Relationship

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Standard C Library Example
•Cprograminvokingprintf()librarycall,whichcallswrite()systemcall

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•Often,moreinformationisrequiredthansimplyidentityofdesired
systemcall
•ExacttypeandamountofinformationvaryaccordingtoOSandcall
•ThreegeneralmethodsusedtopassparameterstotheOS
•Simplest:passtheparametersinregisters
•Insomecases,maybemoreparametersthanregisters
•Parametersstoredinablock,ortable,inmemory,andaddressof
blockpassedasaparameterinaregister
•ThisapproachtakenbyLinuxandSolaris
•Parametersplaced,orpushed,ontothestackbytheprogramand
poppedoffthestackbytheoperatingsystem
•Blockandstackmethodsdonotlimitthenumberorlengthof
parametersbeingpassed
SYSTEM CALLS Parameter passing

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SYSTEM CALLS Parameter passing

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•Process control
•create process, terminate process
•end, abort
•load, execute
•get process attributes, set process attributes
•wait for time
•wait event, signal event
•allocate and free memory
•Dump memory if error
•Debuggerfor determining bugs, single step execution
•Locksfor managing access to shared data between processes
Types of System Calls

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•File management
•create file, delete file
•open, close file
•read, write, reposition
•get and set file attributes
•Device management
•request device, release device
•read, write, reposition
•get device attributes, set device attributes
•logically attach or detach devices
Types of System Calls

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•Information maintenance
•get time or date, set time or date
•get system data, set system data
•get and set process, file, or device attributes
•Communications
•create, delete communication connection
•send, receive messages if message passing model to host nameor
process name
•Fromclient toserver
•Shared-memory model create and gain access to memory regions
•transfer status information
•attach and detach remote devices
Types of System Calls

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Examples of Windows and Unix System Calls

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SYSTEM PROGRAMS

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•Provideaconvenientenvironmentforprogramdevelopmentand
execution.
•Someofthemaresimplyuserinterfacestosystemcalls;
•othersareconsiderablymorecomplex
•Systemprogramsaredividedintofollowingcategories
•File manipulation
•Status information sometimes stored in a File modification
•Programming language support
•Program loading and execution
•Communications
•Background services
•Application programs
SYSTEM PROGRAMS -Definition

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File management
•Create,
•delete,
•copy,
•rename,
•print,
•dump,
•list, and
•generally manipulate files and directories
SYSTEM PROGRAMS -Categories

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Status information
•Ask the system for info
Simple information's
•date,
•time,
•amount of available memory,
•disk space,
•number of users
Complex information's
•Detailed performance,
•logging, and
•debugging information,etc.
SYSTEM PROGRAMS -Categories

62. Department of Computer Science and Engineering
File modification
•SeveralTexteditorsmaybeavailabletocreateandmodifythe
contentoffilesstoredondiskorotherstoragedevices.
•Specialcommandstosearchcontentsoffilesorperform
transformationsofthetext
SYSTEM PROGRAMS -Categories

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Programming-language support
•Compilers,
•assemblers,
•debuggersand
•Interpreters
•Forsomecommonprogramminglanguages(suchasC,C++,JAVA,Visual
Basic&PERL)
•Providedtotheuserwiththeoperatingsystem.
SYSTEM PROGRAMS -Categories

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Program loading and execution
•Once a program is assembled or compiled , it must be loaded into
memory to be executed.
•Absolute loaders,
•Relocatableloaders,
•linkage editors, and
•overlay-loaders,
•Debugging systems for higher-level or machine language are needed.
SYSTEM PROGRAMS -Categories