Processes 𝑃1, 𝑃2, 𝑃3, 𝑃4 arrive in that order at times 0, 1, 2, and 8…

Turnaround Time (TAT) Calculation

Key idea: With Shortest Remaining Time First (SRTF), the CPU always runs the process with the smallest remaining burst; processes can be preempted when a shorter job arrives.

Scheduling timeline (by time intervals):

• 0–2 ms: Process P1 starts at 0; it runs until P3 arrives at 2 (P1 has 8 ms remaining at time 2).

• 2–8 ms: Process P3 (burst 6) has the shortest remaining time and runs to completion at 8 ms.

• 8–16 ms: At time 8 ms P4 arrives. Among remaining processes, P1 has 8 ms, P4 has 9 ms, P2 has 13 ms; P1 is shortest and runs from 8 to 16 ms, finishing at 16 ms.

• 16–25 ms: Next shortest is P4 (9 ms); it runs from 16 to 25 ms and finishes at 25 ms.

• 25–38 ms: Finally P2 runs for its remaining 13 ms and finishes at 38 ms.

Completion times and turnaround times:

• P1: arrival 0 ms, completion 16 ms ⇒ turnaround = 16 − 0 = 16 ms

• P2: arrival 1 ms, completion 38 ms ⇒ turnaround = 38 − 1 = 37 ms

• P3: arrival 2 ms, completion 8 ms ⇒ turnaround = 8 − 2 = 6 ms

• P4: arrival 8 ms, completion 25 ms ⇒ turnaround = 25 − 8 = 17 ms

Average turnaround time:

Average TAT = (16 + 37 + 6 + 17) / 4 = 76 / 4 = 19 ms

Therefore the average turnaround time of the four processes is 19 milliseconds.