Kernel .edu



Operating system and system softwareOperating SystemsSystem commandsCarry out services such as translate a program, load a program, run a programTypes of system commandsLines of text typed at a terminalMenu items displayed on a screen and selected with a mouse and a button: Point-and-clickFunctions of an Operating Systemimportant responsibilities of the operating systemUser interface managementProgram scheduling and activationSchedule programs for executionControl of access to system and filesStore and retrieve filesEfficient resource allocationDeadlock detection and error detectionOversee operation of computerCoordinate the execution of programsOperating System ComponentsKernelPerforms basic required functionsThe user interface act as an intermediary between users and the operating system kernelThe KernalFile managerDirectory (or Folder): A user-created bundle of files and other directories (subdirectories)Directory Path: A sequence of directories within directoriesDevice driversMemory managerAllocates space in main memoryMay create the illusion that the machine has more memory than it actually does (virtual memory) by playing a “shell game” in which blocks of data (pages) are shifted back and forth between main memory and mass storageScheduler and dispatcherEvolution of Shared ComputingBatch processinghas been associated with mainframe computers since the earliest days of electronic computing in the 1950sOLD SCHOOLqueue a project/program into the computer’s job queue, gives the results when donebut still used in billing, payroll, any administration processingInteractive processingRequires real-time processingExample an insurance company can make changes to a customer's household insurance, e.g. while the customer is on the phone. The insurance clerk simply calls up details of the customer's policy on the screen, and types in any required changes which immediately update the customer's records. A report of the change would be automatically generated and a copy sent to the customer.Interactive processingTime-sharing/MultitaskingImplemented by MultiprogrammingMultiprocessor machinesRole and Types of System SoftwareTypes of SoftwareApplication softwarePerforms specific tasks for usersSystem softwareProvides infrastructure for application softwareConsists of operating system and utility softwareTypes of System SoftwareThe Role of System SoftwareSystem software is a collection of many different programsOperating systemControls the overall operation of the computerCommunicates with the userDetermines what the user wantsActivates system programs, applications packages, or user programs to carry out user requestsUser interfaceGraphical user interface (GUI) provides graphical control of the capabilities and services of the computerLanguage servicesAssemblers, compilers, and interpretersAllow you to write programs in a high-level, user-oriented language, and then execute themMemory managersAllocate and retrieve memory spaceInformation managersHandle the organization, storage, and retrieval of information on mass storage devicesI/O systemsAllow the use of different types of input and output devicesSchedulerKeeps a list of programs ready to run and selects the one that will execute nextUtilitiesCollections of library routines that provide services either to user or other system routinesThe User InterfaceOperating systemWaits for a user commandIf command is legal, activates and schedules the appropriate software packageUser interfacesText-orientedGraphicalUser Interface Responsibility of the Operating SystemThe Overall Booting ProcessBoot loader: Program in ROM (example of firmware)Run by the CPU when power is turned onTransfers operating system from mass storage to main memoryExecutes jump to operating systemBoot SequenceProcess (Application) ManagementProcess: The activity of executing a programProcess State: Current status of the activityProgram counterGeneral purpose registersRelated portion of main memoryScheduler: Adds new processes to the process table and removes completed processes from the process tableDispatcher: Controls the allocation of time slices to the processes in the process tableThe end of a time slice is signaled by an interrupt.Time-sharing between process A and process BEfficient Allocation Of ResourcesThe operating system ensures thatMultiple tasks of the computer can be underway at one timeProcessor is constantly busyKeeps a queue of programs that are ready to runWhenever processor is idle, picks a job from the queue and assigns it to the processorSemaphore: A “control flag”Critical Region: A group of instructions that should be executed by only one process at a timeMutual exclusion: Requirement for proper implementation of a critical regionThe Safe Use Of ResourcesDeadlockTwo processes are each holding a resource the other needsNeither process will ever progressThe operating system must handle deadlocksDeadlock preventionDeadlock recoveryDeadLockSystem Security And ProtectionThe operating system must preventNon-authorized people from using the computerUser names and passwordsLegitimate users from accessing data or programs they are not authorized to accessAuthorization lists Attacks from outsideProblemsInsecure passwordsSniffing softwareCounter measuresAuditing softwareAttacks from withinProblemUnruly processesCounter measuresControl process activities via privileged modes and privileged instructionsHistorical Overview of Operating Systems DevelopmentFirst generation of system software (roughly 1945-1955)No operating systemsAssemblers and loaders were almost the only system software providedSecond generation of system software (1955-1965)Batch operating systemsRan collections of input programs one after the otherIncluded a command languageOperation of a Batch Computer SystemThird-generation operating systems (1965-1985)Multiprogrammed operating systemsPermitted multiple user programs to run at onceFourth-generation operating systems (1985-present)Network operating systemsVirtual environment treats resources physically residing on the computer in the same way as resources available through the computer’s networkThe Virtual Environment Created by a Network Operating SystemThe FutureOperating systems will continue to evolvePossible characteristics of fifth-generation systemsMultimedia user interfacesParallel processing systemsCompletely distributed computing environmentsStructure of a Distributed SystemSources:Computer Science Overview – BrookshearFYI Section IntroductionVon Neumann computer“Naked machine”Hardware without any helpful user-oriented featuresExtremely difficult for a human to work with An interface between the user and the hardware is needed to make a Von Neumann computer usableTasks of the interfaceHide details of the underlying hardware from the userPresent information in a way that does not require in-depth knowledge of the internal structure of the systemAllow easy user access to the available resourcesPrevent accidental or intentional damage to hardware, programs, and dataSystem Software: The Virtual MachineSystem softwareActs as an intermediary between users and hardwareCreates a virtual environment for the user that hides the actual computer architectureVirtual machine (or virtual environment)Set of services and resources created by the system software and seen by the user Sources:Batch processing ................
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