GATE CS Operating System questions

In the following process state transition diagram for a uniprocessor system, assume that there are always some processes in the ready state: Now consider the following statements: If a process makes a transition $D$, it would result in another process making transition $A$ immediately. A process $P_2$ in blocked state can make transition E while …

Consider a disk system with $100$ cylinders. The requests to access the cylinders occur in following sequence: $4, 34, 10, 7, 19, 73, 2, 15, 6, 20$ Assuming that the head is currently at cylinder $50$, what is the time taken to satisfy all requests if it takes $1\;\text{ms}$ to move from one cylinder to adjacent one and shortest seek time first …

Consider a system with $4$ types of resources $R1$ ($3$ units), $R2$ ($2$ units), $R3$ ($3$ units), $R4$ ($2$ units). A non-preemptive resource allocation policy is used. At any given instance, a request is not entertained if it cannot be completely satisfied. Three processes $P1$, $P2$, $P3$ request the resources as follows if …

The essential content(s) in each entry of a page table is / are

In which one of the following page replacement policies, Belady's anomaly may occur?

A processor uses $36$ bit physical address and $32$ bit virtual addresses, with a page frame size of $4$ Kbytes. Each page table entry is of size $4$ bytes. A three level page table is used for virtual to physical address translation, where the virtual address is used as follows: Bits $30-31$ are used to index into the first level page table. Bits …

A process executes the following code for(i=0; i<n; i++) fork(); The total number of child processes created is

Which of the following is NOT true of deadlock prevention and deadlock avoidance schemes?

The $P$ and $V$ operations on counting semaphores, where s is a counting semaphore, are defined as follows: $P(s):$ $s=s-1;$ If $s < 0$ then wait; $V(s):$ $s=s+1;$ If $s \leq0$ then wake up process waiting on s; Assume that $P_b$ and $V_b$ the wait and signal operations on binary semaphores are provided. Two binary semaphores $x_b$ …

For a magnetic disk with concentric circular tracks, the seek latency is not linearly proportional to the seek distance due to

The data blocks of a very large file in the Unix file system are allocated using

A process, has been allocated $3$ page frames. Assume that none of the pages of the process are available in the memory initially. The process makes the following sequence of page references (reference string): $1, 2, 1, 3, 7, 4, 5, 6, 3, 1$ Least Recently Used (LRU) page replacement policy is a practical approximation to optimal page replacement. For …

A process has been allocated $3$ page frames. Assume that none of the pages of the process are available in the memory initially. The process makes the following sequence of page references (reference string): $\mathbf{1, 2, 1, 3, 7, 4, 5, 6, 3, 1}$ If optimal page replacement policy is used, how many page faults occur for the above reference string?

Two processes, $P1$ and $P2$, need to access a critical section of code. Consider the following synchronization construct used by the processes: /* P1 */ while (true) { wants1 = true; while (wants2 == true); /* Critical Section */ wants1 = false; } /* Remainder section */ /* P2 */ while (true) { wants2 = true; while (wants1 == true); /* Critical Section …

A single processor system has three resource types $X, Y$ and $Z$, which are shared by three processes. There are $5$ units of each resource type. Consider the following scenario, where the column alloc denotes the number of units of each resource type allocated to each process, and the column request denotes the number of units of each resource type …

A virtual memory system uses First In First Out (FIFO) page replacement policy and allocates a fixed number of frames to a process. Consider the following statements: P: Increasing the number of page frames allocated to a process sometimes increases the page fault rate. Q: Some programs do not exhibit locality of reference. Which one of the following is …

An operating system used Shortest Remaining System Time first (SRT) process scheduling algorithm. Consider the arrival times and execution times for the following processes: …

Consider the following statements about user level threads and kernel level threads. Which one of the following statements is FALSE?

Group 1 contains some CPU scheduling algorithms and Group 2 contains some applications. Match entries in Group 1 to entries in Group 2. …

Consider a disk pack with $16$ surfaces, $128$ tracks per surface and $256$ sectors per track. $512$ bytes of data are stored in a bit serial manner in a sector. The capacity of the disk pack and the number of bits required to specify a particular sector in the disk are respectively: