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What is an operating system? Explain how throughput, turnaround time and response time areused to measure the overall performance of a computer system?

Operating system is an integrated set of programs that
 a. Controls the resources of a computer system.
 b. Provides its user an interface that is easier to use as compared to a bare machine.
 There are several possible purposes of an operating system: To provide an environment for
 a computer user to execute programs on computer hardware in a convenient and efficient
 manner. To allocate the separate resources of the computer as needed to solve the problem
 given. The allocation process should be as fair and efficient as possible.
 Throughput means number of processes completed / time unit.
 Turnaround Time is the average time elapsed from when process is submitted to when it
 has completed.
 Response Time - Average time elapsed from when process is submitted until useful output
 is obtained.

Typically, Utilization and Throughput are traded off for better Response Time. Response
 time is important for OS's that aim to be user-friendly. In general, we would like to
 optimize the average measure. In some cases, minimum and maximum values are
 optimized, e.g. it might be a good idea to minimize the maximum response time.