Which of the following scheduling algorithms are suitable for Time-Sharing / Interactive Systems?
Interactive systems require good response time and preemption, provided by Round Robin and MLFQ. FCFS and non-preemptive SJF can cause high response times.
Consider 3 processes P1, P2, P3 arriving at $t=0$ with CPU burst times 10 ms, 5 ms, and 8 ms respectively. Calculate the average waiting time (in ms) using Non-preemptive SJF scheduling.
SJF execution order: P2 (0-5), P3 (5-13), P1 (13-23).
Waiting times: P2 = 0, P3 = 5, P1 = 13.
Average Waiting Time = (0 + 5 + 13) / 3 = 18 / 3 = 6 ms.
Four processes P1, P2, P3, P4 arrive at time $t = 0$ with burst times 6, 8, 4, 2 ms. If Round Robin scheduling with quantum $Q = 2 ms$ is used, enter the completion time (in ms) of process P4.
Queue: P1, P2, P3, P4.
t=0-2: P1 (rem 4)
t=2-4: P2 (rem 6)
t=4-6: P3 (rem 2)
t=6-8: P4 (rem 0, finishes at $t=8$).
Completion time of P4 = 8 ms.
A counting semaphore S is initialized to 12. A total of 18 wait(S) operations and 9 signal(S) operations are performed on S. Enter the final value of S.
$Initial S = 12.
Net change = -18 + 9 = -9.
Final value = 12 - 9 = 3.$
A system has 5 processes, each requiring 4 units of a resource. What is the MINIMUM number of units of this resource required to ensure that deadlock NEVER occurs?
$Formula: R >= N * (Max - 1) + 1.
N = 5, Max = 4.
R = 5 * (4 - 1) + 1 = 5 * 3 + 1 = 16.$