GATE CS Operating System questions

Consider the following four processes with arrival times (in milliseconds) and their length of CPU bursts (in milliseconds) as shown below: …

The index node (inode) of a Unix -like file system has $12$ direct, one single-indirect and one double-indirect pointers. The disk block size is $4$ kB, and the disk block address is $32$-bits long. The maximum possible file size is (rounded off to $1$ decimal place) ____ GB

Consider a storage disk with $4$ platters (numbered as $0, 1, 2$ and $3$), $200$ cylinders (numbered as $0, 1, … , 199$), and $256$ sectors per track (numbered as $0, 1, … 255$). The following $6$ disk requests of the form [sector number, cylinder number, platter number] are received by the disk controller at the same time: …

In a system, there are three types of resources: $E, F$ and $G$. Four processes $P_0$, $P_1$, $P_2$ and $P_3$ execute concurrently. At the outset, the processes have declared their maximum resource requirements using a matrix named Max as given below. For example, Max[$P_2, F$] is the maximum number of instances of $F$ that $P_2$ would …

Consider the following solution to the producer-consumer synchronization problem. The shared buffer size is $N$. Three semaphores $empty$, $full$ and $mutex$ are defined with respective initial values of $0, N$ and $1$. Semaphore $empty$ denotes the number of available slots in the buffer, for the consumer to read from. Semaphore $full$ …

Consider a system with $3$ processes that share $4$ instances of the same resource type. Each process can request a maximum of $K$ instances. Resources can be requested and releases only one at a time. The largest value of $K$ that will always avoid deadlock is ___

Consider a process executing on an operating system that uses demand paging. The average time for a memory access in the system is $M$ units if the corresponding memory page is available in memory, and $D$ units if the memory access causes a page fault. It has been experimentally measured that the average time taken for a memory access in the process is …

The following are some events that occur after a device controller issues an interrupt while process $L$ is under execution. P. The processor pushes the process status of $L$ onto the control stack Q. The processor finishes the execution of the current instruction R. The processor executes the interrupt service routine S. The processor pops the process …

Recall that Belady's anomaly is that the page-fault rate may increase as the number of allocated frames increases. Now, consider the following statements: $S_1$: Random page replacement algorithm (where a page chosen at random is replaced) suffers from Belady's anomaly. $S_2$: LRU page replacement algorithm suffers from Belady's anomaly. Which of the …

A multithreaded program $P$ executes with $x$ number of threads and uses $y$ number of locks for ensuring mutual exclusion while operating on shared memory locations. All locks in the program are non-reentrant, i.e., if a thread holds a lock $l$, then it cannot re-acquire lock $l$ without releasing it. If a thread is unable to acquire a lock, it …

Consider the following CPU processes with arrival times (in milliseconds) and length of CPU bursts (in milliseconds) as given below: …

Threads of a process share

Consider the set of process with arrival time (in milliseonds), CPU burst time (in millisecods) and priority ($0$ is the highest priority) shown below. None of the process have I/O burst time …

In a file allocation system, which of the following allocation scheme(s) can be used if no external fragmentation is allowed? Contiguous Linked Indexed

A system shares $9$ tape drives. The current allocation and maximum requirement of tape drives for that processes are shown below: …

Which of the following is/are shared by all the threads in a process? Program counter Stack Address space Registers

Consider the following proposed solution for the critical section problem. There are $n$ processes : $P_0....P_{n-1}$. In the code, function $\text{pmax}$ returns an integer not smaller than any of its arguments .For all $i,t[i]$ is initialized to zero. Code for $P_i$; do { c[i]=1; t[i]= pmax (t[0],....,t[n-1])+1; c[i]=0; for every j != i in …

Cylinder a disk queue with requests for $I/O$ to blocks on cylinders $47, 38, 121, 191, 87, 11, 92, 10.$ The C-LOOK scheduling algorithm is used. The head is initially at cylinder number $63$, moving towards larger cylinder numbers on its servicing pass. The cylinders are numbered from $0$ to $199$. The total head movement (in number of cylinders) …

Consider a computer system with ten physical page frames. The system is provided with an access sequence $(a_{1}, a_{2},....,a_{20}, a_{1}, a_{2},...a_{20})$, where each $a_{i}$ is a distinct virtual page number. The difference in the number of page faults between the last-in-first-out page replacement policy and the optimal page replacement policy …

Consider a computer system with $40$-bit virtual addressing and page size of sixteen kilobytes. If the computer system has a one-level page table per process and each page table entry requires $48$ bits, then the size of the per-process page table is __________ megabytes.