Operating System (GATE)
| Description: The test contains the numerical questions of operating system. | |
| Number of Questions: 15 | |
| Created by: Sanjiv Memon | |
| Tags: Deadlock ; scheduling; page replacement Architecture Response Time Management |
An operating system has 11 tape drives. There are three processes P1, P2 and P3 with maximum tape drive requirements of 10, 4 and 7, respectively. Currently tape drives allocated to processes P1, P2 and P3 are 4, 2 and 2, respectively. Which of the following sequences represents a safe state?
An imaginary disk has 50 cylinders. If disk head on a cylinder is 15. Find the number of disk moves using shortest seek time first algorithm. The new requests are as follow: 5, 45, 10, 30, 21, 42, 35.
In a uniprocessor system a new process arrives at an average of four processes per minute and each such process requires an average of 5 seconds of service time. Calculate CPU utilisation?
An imaginary disk has 55 cylinders. If disk head on a cylinder is 25, find the number of disk moves using first come first serve [FCFS] algorithm. The new requests are as follows: 5, 45, 10, 30, 21, 42, 35
Find the total waiting time using SJF without pre-emption scheduling.
| Process | Arrival time | CPU burst time |
| p1 | 0 | 5 |
| p2 | 2 | 4 |
| p3 | 1 | 6 |
| p4 | 3 | 3 |
Hit ratio to a TLB is 75%. It takes 25 nanoseconds to search TLB and 200 nanoseconds to access the main memory. What is the effective memory access time?
A job has 3 pages A, B, C and the main memory has two page frames only. The job needs to process its pages in following order : A B A B C B A C B A. The number of pages that interrupt in LRU page replacement algorithm are
An OS uses elevator algorithm to schedule the disk-arm. I/O requests are currently pending for blocks on tracks 1, 15, 20, 35, 40, and 45. The disk arm is currently at track 19 and moving upwards. In what order will these requests be handled?
WT = waiting time, AWT = average waiting time, AT = arrival time
Consider the following set of processes, the length of the CPU burst time and arrival time given in milliseconds are as follow:
| Process | Arrival time | CPU time |
| P1 | 0 | 5 |
| P2 | 2 | 4 |
| P3 | 1 | 6 |
| P4 | 3 | 3 |
Find out average waiting time using FCFS scheduling.
How many context switches are required for SRJF scheduling for the given processes?
| Process | Arrival time | CPu burst time |
| p1 | 0 | 5 |
| p2 | 2 | 4 |
| p3 | 1 | 6 |
| p4 | 3 | 3 |
A job has 3 pages A, B, C and the main memory has 2 page frames only. The job needs to process its pages in following order : A B A B C B A C B A. The number of page faults using FIFO page replacement algorithm is
Turnaround time = completion time – arrival time. Average turnaround time = Total turnaround time/total processes
| Process | Arrival Time | CPU burst time |
| p1 | 0 | 4 |
| p2 | 1 | 10 |
| p3 | 2 | 15 |
What is the average turnaround time for these processes with the preemptive shortest remaining processing time first (SROT) algorithm?
In a system the fraction of time CPU is busy in a system with a single processor is 70%. Each process requires an average of 7 seconds of service time. Find out the processors that arrive per minute.
An operating system has 11 devices and has three processes P1, P2 and P3 with maximum resource requirements of 6, 4 and 9, respectively. There are two states of allocation of devices, as follows: State 1 - Processes P1, P2, P3 have devices allocated 3, 3, 4, respectively. State 2 - Processes P1, P2, P3 have devices allocated 2, 2, 6, respectively.
Which of the following is correct?
Consider a situation in which the disk read/write head is currently located at track 15 (of tracks 0-50) and moving in the positive direction. Assume that the following track requests have been made in this order: 5, 45, 30, 10, 25, 35, 42, 21. What is the order in which optimised C-SCAN would service these requests and what is the total seek distance?