Question

What are the advantages and disadvantages of a time-sharing system? Explain. (b) Is multi-programming more effective in a batch OS or in a time-sharing OS? Explain. (c) How is the effectiveness of scheduling measured? Explain.

Answer 1

Answer:

a) Advantages of time-sharing system:

• It provides the advantage of quick response.
• This type of operating system avoids duplication of software.
• It reduces CPU idle time

Disadvantages of time-sharing system:

• Time sharing has problem of reliability.
• Question of security and integrity of user programs and data can be raised.
• Problem of data communication occurs.

b) Multiprogramming is more effective in time sharing operating system.

Time sharing is a logical extension of multiprogramming. The CPU performs many tasks by switches are so frequent that the user can interact with each program while it is running. A time shared operating system allows multiple users to share computers simultaneously. Multiprogramming allows multiple processes to be active at once. Timesharing allows the multiple processes to be interactive ones.

c) Various criteria or characteristics are used to measure effectiveness of scheduling:

• CPU Utilization − A scheduling algorithm should be designed so that CPU remains busy as possible. It should make efficient use of CPU.

• Throughput − Throughput is the amount of work completed in a unit of time. In other words throughput is the processes executed to number of jobs completed in a unit of time. The scheduling algorithm must look to maximize the number of jobs processed per time unit.

• Response time − Response time is the time taken to start responding to the request. A scheduler must aim to minimize response time for interactive users.

• Turnaround time − Turnaround time refers to the time between the moment of submission of a job/ process and the time of its completion. Thus how long it takes to execute a process is also an important factor.

• Waiting time − It is the time a job waits for resource allocation when several jobs are competing in multiprogramming system. The aim is to minimize the waiting time.

• Fairness − A good scheduler should make sure that each process gets its fair share of the CPU.

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