Tuesday, November 11, 2014

Gate Questions Set-3

Gate Questions Set-3


Which of the following devices should get higher priority in assigning interrupts?

(a) Hard disk (b) Printer
(c) Keyboard (d) Floppy disk

Ans:- Option-C


1. System calls are usually invoked by using

      (a)a software interrupt (b) polling 
      (c) an indirect jump      (d) a privileged instruction

Ans:- Option-A


2.  A multi-user, multi-processing operating system cannot be implemented on      hardware that does not support

    (a)  Address-translation 
    (b)  DMA for disk transfer
    (c)  At least two modes of CPU execution (privileged and non-privileged)
    (d)  Demand paging

Ans: Option A,B,C


3. Which of the following actions is/are typically not performed by the         operating system when switching context from process A to process B? 

(a) Saving current register values and restoring saved register values for process B.    
(b) Changing address translation tables. 
(c) Swapping out the memory image of process A to the disk.    
(d) Invalidating the translation look-aside buffer. 

Ans: Option C,D


When the context switch occur processor save the currently running data into register and then load new data of other process.
Swapping out the memory image of process to the disk occurs only when the process is suspended.


1.  Which of the following need not necessarily be saved on a context switch
between processes?
(a) General purpose registers (b) Translation look-aside buffer
(c) Program counter (d) All of the above

Answer: Option-B


When a context switch occur, running process data stored in PCB, so that, when the scheduler gets back to the execution of the same process again, it can restore this state and continue.

A TLB (Translation look-aside buffer) is a cache memory for CPU it stores the process data which is frequently used by CPU.


2.  Suppose the time to service a page fault is on the average 10 milliseconds, while a memory access takes 1 microsecond. Then a 99.99% hit ratio results in average memory access time of

(a) 1.9999 milliseconds (b) 1 millisecond
(c) 9.999 microseconds (d) 1.9999 microseconds

Ans:- Option-D

Average memory access time=[(% of page miss)*(time to service a page fault) + (% of page hit)*(memory access time)]/100

So, average memory access time in microseconds is.
(99.99*1 + 0.01*10*1000)/100 = (99.99+100)/1000 = 199.99/1000 =1.9999 ┬Ás


1.  Which of the following statements is false?

(a) Virtual memory implements the translation of a program’s address space into physical memory address space
(b) Virtual memory allows each program to exceed the size of the primary memory
(c) Virtual memory increases the degree of multiprogramming
(d) Virtual memory reduces the context switching overhead.

Answer: Option-A


2.  Consider a set of n tasks with known run times r1, r2, ….rn to be run on a
uniprocessor machine. Which of the following processor scheduling algorithms will result in the maximum throughput?
(a) Round-Robin (b) Shortest-Job-First
(c) Highest-Response-Ratio-Next (d) First-Come-First-Served

Ans:- Option-B



Total number of tasks executed per unit time. 
Shortest Job First has maximum throughput because in this scheduling technique shortest jobs are executed first hence maximum number of tasks are completed.


3.  Where does the swap space reside?

(a) RAM (b) Disk
(c) ROM (d) On-chip cache

Answer: Option-B

Swap space is an area on disk that temporarily holds a process memory image. When physical memory demand is sufficiently low, process memory images are brought back into physical memory from the swap area. Having sufficient swap space enables the system to keep some physical memory free at all times.

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1 comment:

  1. Gate 1998:-

    Which of the following devices should get higher priority in assigning interrupts?

    Hard disk
    Floppy disk

    Answer should be A-hard disk.
    plz correct the answer bcoz it confuse others.....Keybord is lowest priority


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