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Operating System Overview Presentation Transcript: 1.Operating System Overview - 2
2.Operating SystemA program that controls the execution of application programsAn interface between applications and hardware
3.ConvenienceMakes the computer more convenient to useEfficiencyAllows computer system resources to be used in an efficient mannerAbility to evolvePermit effective development, testing, and introduction of new system functions without interfering with service
4.Layers of Computer System
5.KernelPortion of operating system that is in main memoryContains most frequently used functionsAlso called the nucleus
6.Evolution of an Operating SystemHardware upgrades plus new types of hardwareNew servicesFixes
7.Evolution of Operating SystemsSerial ProcessingNo operating systemMachines run from a console with display lights, toggle switches, input device, and printerSchedule timeSetup included loading the compiler, source program, saving compiled program, and loading and linking
8.Simple Batch SystemsMonitorsSoftware that controls the sequence of eventsBatch jobs togetherProgram branches back to monitor when finished
9.Special type of programming languageProvides instruction to the monitorWhat compiler to useWhat data to use
10.Hardware FeaturesMemory protectionDo not allow the memory area containing the monitor to be alteredTimerPrevents a job from monopolizing the system
11.Privileged instructionsCertain machine level instructions can only be executed by the monitorInterruptsEarly computer models did not have this capability
12.Memory ProtectionUser program executes in user modeCertain instructions may not be executedMonitor executes in system modeKernel modePrivileged instructions are executedProtected areas of memory may be accessed
13.UniprogrammingProcessor must wait for I/O instruction to complete before preceding
14.MultiprogrammingWhen one job needs to wait for I/O, the processor can switch to the other job
15.Time SharingUsing multiprogramming to handle multiple interactive jobsProcessor’s time is shared among multiple usersMultiple users simultaneously access the system through terminals
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Types of Operating System Presentation Transcript: 1.Types of Operating System
2.Types of Operating SystemOperating systems are there from the very first computer generation. Operating systems keep evolving over the period of time. Following are few of the important types of operating system which are most commonly used.
3.Batch operating systemThe users of batch operating system do not interact with the computer directly. Each user prepares his job on an off-line device like punch cards and submits it to the computer operator. To speed up processing, jobs with similar needs are batched together and run as a group. Thus, the programmers left their programs with the operator. The operator then sorts programs into batches with similar requirements.
4.The problems with Batch Systems are following.Lack of interaction between the user and job.CPU is often idle, because the speeds of the mechanical I/O devices is slower than CPU.Difficult to provide the desired priority.
5.Time-sharing operating systemsTime sharing is a technique which enables many people, located at various terminals, to use a particular computer system at the same time. Time-sharing or multitasking is a logical extension of multiprogramming. Processor's time which is shared among multiple users simultaneously is termed as time-sharing. The main difference between Multiprogrammed Batch Systems
6.Multiple jobs are executed by the CPU by switching between them, but the switches occur so frequently. Thus, the user can receives an immediate response. For example, in a transaction processing, processor execute each user program in a short burst or quantum of computation. That is if n users are present, each user can get time quantum. When the user submits the command, the response time is in few seconds at most.
7.and Time-Sharing Systems is that in case of Multiprogrammed batch systems, objective is to maximize processor use, whereas in Time-Sharing Systems objective is to minimize response time.
Operating system uses CPU scheduling and multiprogramming to provide each user with a small portion of a time. Computer systems that were designed primarily as batch systems have been modified to time-sharing systems.
8.Advantages of Timesharing operating systems are followingProvide advantage of quick response.Avoids duplication of software.Reduces CPU idle time.
9.Disadvantages of Timesharing operating systems are following.Problem of reliability.Question of security and integrity of user programs and data.Problem of data communication.
10.Distributed operating SystemDistributed systems use multiple central processors to serve multiple real time application and multiple users. Data processing jobs are distributed among the processors accordingly to which one can perform each job most efficiently.The processors communicate with one another through various communication lines (such as high-speed buses or telephone lines). These are referred as loosely coupled systems or distributed systems. Processors in a distributed system may vary in size and function. These processors are referred as sites, nodes, computers and so on.
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