What is the bit rate of a video terminal unit with 80 characters/line, 8 bits/character and horizontal sweep time of lOOµs (including 20 µs of retrace time)?

Which one of the following is NOT shared by the threads of the same process?

Which of the following commands or sequences of commands will rename a file x to file y in a unix system?

I. mv y,x
II. mv x,y
III. cp y, x(rm x)
IV. cp x, y (rm x) 

Consider a pipeline processor with 4 stages S1 to S4. We want to execute the following loop:
For(i=1:i<=1000; i++)
{I1,I2,I3,I4}
where the time taken (in ns) by instructions I1 to I4 for stages S1 to S4 are given below:

       S1   S2   S3   S4
I1:    1    2    1    2
I2:    2    1    2    1
I3:    1    1    2    1
I4:    2    1    2    1 

Consider a fully associative cache with 8 cache blocks (numbered 0-7) and the following sequence of memory block requests:
4, 3, 25, 8, 19, 6, 25, 8, 16, 35, 45, 22, 8, 3, 16, 25, 7
If LRU replacement policy is used, which cache block will have memory block 7?

A CPU has only three instructions I1, I2 and I3, which use the following signals in time steps T1-T5:

I1 : 
T1 : Ain, Bout, Cin 
T2 : PCout, Bin 
T3 : Zout, Ain 
T4 : Bin, Cout 
T5 : End 
I2 : 
T1 : Cin, Bout, Din 
T2 : Aout, Bin 
T3 : Zout, Ain 
T4 : Bin, Cout 
T5 : End 
I3 : 
T1 : Din, Aout 
T2 : Ain, Bout 
T3 : Zout, Ain 
T4 : Dout, Ain 
T5 : End  

In an enhancement of a design of a CPU, the speed of a floating point unit has been increased by 20% and the speed of a fixed point unit has been increased by 10%. What is the overall speedup achieved if the ratio of the number of floating point operations to the number of fixed point operations is 2:3 and the floating point operation used to take twice the time taken by the fixed point operation in the original design?

The storage area of a disk has innermost diameter of 10 cm and outermost diameter of 20 cm. The maximum storage density of the disk is 1400 bits/cm. The disk rotates at a speed of 4200 RPM. The main memory of a computer has 64-bit word length and 1µs cycle time. If cycle stealing is used for data transfer from the disk, the percentage of memory cycles stolen for transferring one word is

A disk has 200 tracks (numbered 0 through 199). At a given time, it was servicing the request of reading data from track 120, and at the previous request, service was for track 90. The pending requests (in order of their arrival) are for track numbers

 30 70 115 130 110 80 20 25 

In a certain operating system, deadlock prevention is attempted using the following scheme. Each process is assigned a unique timestamp, and is restarted with the same timestamp if killed. Let Ph be the process holding a resource R, Pr be a process requesting for the same resource R, and T(Ph) and T(Pr) be their timestamps respectively. The decision to wait or preempt one of the processes is based on the following algorithm.

if T(Pr) < T(Ph) then 
      kill Pr
else 
      wait

A process executes the following segment of code:

for(i = 1; i < = n; i++)
   fork();

The semaphore variables full, empty and mutex are initialized to 0, n and 1, respectively. Process P1 repeatedly adds one item at a time to a buffer of size n, and process P2 repeatedly removes one item at a time from the same buffer using the programs given below. In the programs, K, L, M and N are unspecified statements.

P1:  while (1) {     
                 K; P(mutex); 
                 Add an item to the buffer; 
                 V(mutex); L; 
     } 
P2:  while (1) {    
                 M; P(mutex); 
                 Remove an item from the buffer; 
                 V(mutex); N; 
     }  

In a virtual memory system, size of virtual address is 32-bit, size of physical address is 30-bit, page size is 4 Kbyte and size of each page table entry is 32-bit. The main memory is byte addressable. Which one of the following is the maximum number of bits that can be used for storing protection and other information in each page table entry?

Consider the following schedule S of transactions T1 and T2:

   T1	         T2
Read(A)
A = A - 10	
               Read (A)
               Temp = 0.2*A 
               Write(A) 
               Read(B)
Write(A)
Read(B) 
B = B + 10 
Write(B)	
               B = B + Temp
               Write(B) 

Consider allocation of memory to a new process. Assume that none of the existing holes in the memory will exactly fit the process’s memory requirement. Hence, a new hole of smaller size will be created if allocation is made in any of the existing holes. Which one of the following statements is TRUE?

Consider the following statements about process state transitions for a system using preemptive scheduling.

I. A running process can move to ready state.
II. A ready process can move to running state.
III. A blocked process can move to running state.
IV. A blocked process can move to ready state.

Which of the above statements are TRUE?

Consider the following set of processes, assumed to have arrived at time 0. Consider the CPU scheduling algorithms Shortest Job First (SJF) and Round Robin (RR). For RR, assume that the processes are scheduled in the order P₁,P₂,P₃,P₄.

If the time quantum for RR is 4 ms, then the absolute value of the difference between the average turnaround times (in ms) of SJF and RR (round off to 2 decimal places) is _____.

Each of a set of n processes executes the following code using two semaphores a and b initialized to 1 and 0, respectively. Assume that count is a shared variable initialized to 0 and not used in CODE SECTION P.

wait (a); count = count+1;
if (count==n) signal (b);
signal (a); wait (b); signal (b);

What does the code achieve?

Consider the following five disk access requests of the form (request id, cylinder number) that are present in the disk scheduler queue at a given time.

         (P, 155), (Q, 85), (R, 110), (S, 30), (T, 115) 

Assume the head is positioned at cylinder 100. The scheduler follows Shortest Seek Time First scheduling to service the requests.

Which one of the following statements is FALSE?

Consider a paging system that uses a 1-level page table residing in main memory and a TLB for address translation. Each main memory access takes 100 ns and TLB lookup takes 20 ns. Each page transfer to/from the disk takes 5000 ns. Assume that the TLB hit ratio is 95%, page fault rate is 10%. Assume that for 20% of the total page faults, a dirty page has to be written back to disk before the required page is read in from disk. TLB update time is negligible. The average memory access time in ns (round off to 1 decimal places) is ______.

The process state transition diagram in below figure is representative of

A critical section is a program segment

Which of the following is an example of spooled device?

The correct matching for the following pairs is

         A. Activation record	   1. Linking loader
         B. Location counter	   2. Garbage collection
         C. Reference counts	   3. Subroutine call
         D. Address relocation	   4. Assembler 

A 1000 Kbyte memory is managed using variable partitions but to compaction. It currently has two partitions of sizes 200 Kbytes and 260 Kbytes respectively. The smallest allocation request in Kbytes that could be denied is for

A solution to the Dining Philosophers Problem which avoids deadlock is

Four jobs to be executed on a single processor system arrive at time 0⁺ in the order A, B, C, D. their burst CPU time requirements are 4, 1, 8, 1 time units respectively. The completion time of A under round robin scheduling with time slice of one time unit is

A demand paged virtual memory system uses 16 bit virtual address, page size of 256 bytes, and has 1 Kbyte of main memory. LRU page replacement is implemented using a list whose current status (page number in decimal) is

For each hexadecimal address in the address sequence given below

 00FF, 010D, 10FF, 11B0

indicate
(i) the new status of the list
(ii) page faults, if any, and
(iii) page replacements, if any

The concurrent programming constructs fork and join are as below:
fork which creates a new process executing from the specified label
join which decrements the specified synchronization variable (by 1) and terminates the process if the new value is not 0.
Show the precedence graph for S1, S2, S3, S4, and S5 of the concurrent program below.

   N = 2
   M = 2
   fork L3
   fork L4
   S1
L1:join N
   S3
L2:join M
   S5
L3:S2
   goto L1
L4:S4
   goto L2
next: 

A computer system uses the Banker’s Algorithm to deal with deadlocks. Its current state is shown in the table below, where P0, P1, P2 are processes, and R0, R1, R2 are resources types.

(a) Show that the system can be in this state.
(b) What will the system do on a request by process P0 for one unit of resource type R1?

A file system with a one-level directory structure is implemented on a disk with disk block size of 4K bytes. The disk is used as follows:

 Disk-block 0: File Allocation Table, consisting of one 8-bit entry per date block, 
               representing the data block address of the next date block in the file
 Disk block 1: Directory, with one 32 bit entry per file:
 Disk block 2: Data block 1;
 Disk block 3: Data block 2; etc. 

(a) What is the maximum possible number of files?
(b) What is the maximum possible file size in blocks?

Locality of reference implies that the page reference being made by a process

The correct matching for the following pairs is

(A) Disk Scheduling        (1) Round robin
(B) Batch Processing       (2) SCAN
(C) Time sharing           (3) LIFO
(D) Interrupt processing   (4) FIFO  

I/O redirection

Thrashing

Dirty bit for a page in a page table

An operating system contains 3 user processes each requiring 2 units of resource R. The minimum number of units of r such that no deadlocks will ever arise is

Each Process P_i, i = 1…….9 is coded as follows

    repeat 
           P(mutex)
           {Critical section}
           V(mutex)
    forever   

The code for P₁₀ is identical except it uses V(mutex) in place of P(mutex). What is the largest number of processes that can be inside the critical section at any moment?

A linker reads four modules whose lengths are 200, 800, 600 and 500 words, respectively. If they are loaded in that order, what are the relocation constants?

Which of the following is an example of a spooled device?

When  the  result  of  a  computation  depends  on  the  speed  of  the  processes involved there is said to be

A counting semaphore was initialized to 10. Then 6P (wait) operations and 4V (signal) operations were completed on this semaphore. The resulting value of the semaphore is

A  computer  has  six  tape  drives,  with  n  processes  competing  for  them.  Each process may need two drives. What is the maximum value of n for the system to be deadlock free?

The overlay tree for a program is as shown below:

What will be the size of the partition (in physical memory) required to load (and run) this program?

Consider n processes sharing the CPU in a round-robin fashion. Assuming that each process switch takes s seconds, what must be the quantum size q such that the overhead resulting from process switching is minimized but at the same time each process is guaranteed to get its turn at the CPU at least every t seconds?