Which of the following statement(s) is/are correct in the context of CPU scheduling?

Let us analyze the statements:

• (A) Turnaround time includes waiting time:Correct. Turnaround time is the total time taken from process submission to its completion. It is calculated as:

  $$\text{Turnaround Time} = \text{Burst Time (CPU + I/O)} + \text{Waiting Time}$$

• (B) The goal is to only maximize CPU utilization and minimize throughput:Incorrect. The goal of CPU scheduling is to maximize CPU utilization and maximize throughput (number of processes completed per unit time), while minimizing turnaround time, waiting time, and response time.

• (C) Round-robin policy can be used even when the CPU time required by each of the processes is not known apriori:Correct. Round-robin (RR) is a preemptive scheduling algorithm that allocates a fixed time slice (quantum) to each process in turn. It does not require prior knowledge of the burst times of processes (unlike SJF or SRTF).

• (D) Implementing preemptive scheduling needs hardware support:Correct. Preemptive scheduling requires an interrupting mechanism (specifically, a hardware timer interrupt) to return control from the running user process back to the operating system/scheduler when a time slice expires or a higher-priority event occurs.

Hence, statements (A), (C), and (D) are correct.