1) The service and functions provided by an operating system can be divided into
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Question
1) The service and functions provided by an operating system can be divided into two main categories. Briefly describes the two categories and discuss how they differ.
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2) Explain the concept of a process.
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3) What is process scheduling? Explain various type of process schedulings.
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4) We consider 4 processes, A, B, C, D. We assume that the execution of
process requires:
For A: 7 CPU time units, 3 (I / O) time units and 5 CPU time units.
For B: 6 CPU time units, 4 (I / O) time units, 4 CPU time units.
For C: 5 CPU time units.
For D: 1 CPU time unit, 4 (I / O) time units and 2 CPU time units.
We suppose that
A is presented first, at time 0,
B occurs at time 1,
C is present at time 9,
D is present at time 12.
Show how the 4 processes will use the processor in each of the following cases:
1) Each process has its own (I / O) device and the scheduler works according to First In First Out "FIFO" (without pre-emption).
2) Each process has its own (I / O) device and the scheduler uses the turnaround algorithm, with a quantum of 5. The switching time is equal to 0. In this case, residence time of processes A, B, C and D.
3) The three processes use the same (I / O) device whose queue
waiting is handled FIFO. The scheduler of the processor uses the turnaround algorithm, with a quantum of 5. The switching time is assumed to be 0.
Explanation / Answer
1)
The Answer for your question is given below clearly step by step;
1. One class of services provided by an operating system is to enforce protection between different processes running concurrently in the system. Processes are allowed to access only those memory locations that are associated with their address spaces.
2. THe processes are not allowed to corrupt files associated with other users.
3. A process is also not allowed to access devices directly without operating system intervention. The second class of services provided by an operating system is to provide new functionality that is not supported directly by the underlying hardware. Virtual memory and file systems are two such examples of new services provided by an operating system.
2)
Now I am going to explain about the concept of process step by step:
1. Generally A process is nothing but it is an instance of a program that is running in a computer and also it is a term used in some operating systems.
2. In UNIX and some other operating systems a process is started when a program is initiated either by a user entering a shell command or by another program.similar to a task.
3. And a process is nothing but it is a running program with which a particular set of data is associated so that the process can be kept track of and An application that is being shared by multiple users will generally have one process at some stage of execution for each user.
4. A process can initiate a subprocess which is a called a child process and a child process is a replica of the parent process and shares some of its resources but it cannot exist if the parent is terminated.
5. The Main point about Processes is that the Processes can exchange information or synchronize their operation through several methods of interprocess communication.
6. THis is about the concept of a process.
3)
Now I am going to explain about the process scheduling step by step:
1. Generally The process scheduling is nothing but it is a activity of the process manager that handles the removal of the running process from the CPU and the selection of another process on the basis of a particular strategy.
2. And Process scheduling is an essential part of a Multiprogramming operating systems. Such operating systems allow more than one process to be loaded into the executable memory at a time and the loaded process shares the CPU using time multiplexing.
3. THe various type of process schedulings are.
a. Long-Term Scheduler
b. Short-Term Scheduler
c. Medium-Term Scheduler
a) Long Term Scheduler:
This is also called as job scheduler and 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.
b)Short-Term Scheduler:
This is also called as CPU scheduler and 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.
c)Medium-Term Scheduler:
This Medium-term scheduling is a part of swapping and It removes the processes from the memory. It reduces the degree of multiprogramming. The medium-term scheduler is in-charge of handling the swapped out-processes.
so this is about process scheduling and various types of process scheduling
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