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Long Term Scheduler
It is also called a job scheduler. A long-term scheduler determines which programs are admitted to the system for processing. It selects processes from the queue and loads them into memory for execution. Process loads into the memory for CPU scheduling.
The primary objective of the job scheduler is to provide a balanced mix of jobs, such as I/O bound and processor bound. It also controls the degree of multiprogramming. If the degree of multiprogramming is stable, then the average rate of process creation must be equal to the average departure rate of processes leaving the system.
On some systems, the long-term scheduler may not be available or minimal. Time-sharing operating systems have no long term scheduler. When a process changes the state from new to ready, then there is use of long-term scheduler.
Short Term Scheduler
It is also called as CPU scheduler. Its main objective is to increase system performance in accordance with the chosen set of criteria. It is the change of ready state to running state of the process. CPU scheduler selects a process among the processes that are ready to execute and allocates CPU to one of them.
Short-term schedulers, also known as dispatchers, make the decision of which process to execute next. Short-term schedulers are faster than long-term schedulers.
chegedict answered the question on March 30, 2020 at 07:45
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Date posted: March 30, 2020. Answers (1)
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Provides the user an interface to interact with the system.
Manages input devices to take inputs from the user. For example, keyboard.
Manages output devices to show outputs to the user. For example, Monitor.
Date posted: March 24, 2020. Answers (1)
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Advantages
High and efficient CPU utilization.
User feels that many programs are allotted CPU almost simultaneously.
Disadvantages
CPU scheduling is required.
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Date posted: March 24, 2020. Answers (1)
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The advantages of distributed systems are as follows -
With resource sharing facility, a user at one site may be able to use the resources available at another.
Speedup the exchange of data with one another via electronic mail.
If one site fails in a distributed system, the remaining sites can potentially continue operating.
Better service to the customers.
Reduction of the load on the host computer.
Reduction of delays in data processing.
Date posted: March 21, 2020. Answers (1)
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Distributed systems use multiple central processors to serve multiple real-time applications and multiple users. Data processing jobs are distributed among the processors accordingly.
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.
The advantages of distributed systems are as follows -
With resource sharing facility, a user at one site may be able to use the resources available at another.
Speedup the exchange of data with one another via electronic mail.
If one site fails in a distributed system, the remaining sites can potentially continue operating.
Better service to the customers.
Reduction of the load on the host computer.
Reduction of delays in data processing.
Date posted: March 21, 2020. Answers (1)
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Time-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 and Time-Sharing Systems is that in case of Multiprogrammed batch systems, the objective is to maximize processor use, whereas in Time-Sharing Systems, the objective is to minimize response time.
Disadvantages of Time-sharing operating systems are as follows -
Problem of reliability.
Question of security and integrity of user programs and data.
Problem of data communication.
Date posted: March 21, 2020. Answers (1)
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Date posted: March 21, 2020. Answers (1)
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The problems with Batch Systems are as follows -
Lack of interaction between the user and the job.
CPU is often idle, because the speed of the mechanical I/O devices is slower than the CPU.
Difficult to provide the desired priority
Date posted: March 21, 2020. Answers (1)
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