QN=1 A CPU may have two or more complete processors, so that can carry out

multiple threads in the same time is called:

a. Pipeline
b. Superscalar
c.. Multicore
d. None of the other choices

QN=2 Examples of general purpose stored program computers include the

following except
a. Personal computers
b. Network servers
c. Workstations
d.. MP3 player

QN=3 Which of the following instructions should be allowed in user mode?

a. Disable all interrupts
b.. Read the time-of-day clock
c. Set the time-of-day clock
d. Change the memory map

QN=4 As one proceeds down the memory hierarchy (from inboard memory to
offline storage), which of the following conditions is correct?
a.. Decreasing cost per bit
b. Decreasing capacity
c. Decreasing access time
d. None of the other choices

1
QN=5 Which of the following actions generates an external interrupt?
a.. An input/output operation is completed.
b. A page that does not exist in the main memory is accessed by the virtual
storage management.
c. A system call instruction is executed.
d. Division by zero occurs.

QN=6 What is not a main function of an operating system?

a. Provide the users with an extended (virtual) machine
b. Manage the I/O devices
c.. Provide user interfaces
d. Support virtual memory

QN=7 What is the main characteristic of real-time operating system?

a. Multiple CPU
b. Time-sharing
c.. Time is key parameter
d. Many I/O devices

QN=8 What is correct about trap instructions and interrupts?

a. Trap instruction switches the execution mode of a CPU from the user
mode to the kernel mode.
b. A trap instruction is caused by a user program to invoke functions in the
OS kernel
c. An interrupt is caused by an external event
d.. All of the other choices

2
QN=9 A simple structuring model for monolithic system includes:
a. A main program that invokes the requested service procedure
b. A set of service procedures that carry out the system calls
c. A set of utility procedures that help the service procedures
d.. All of the other choices

QN=10 A process where no concurrency inside process; everything happens

sequentially is called :
a. Random access process
b.. Sequential process
c. Sequential access process
d. None of the other choices

QN=11 Which of the following process state transitions is correct, when the
external event for which a process was waiting happens?
a. Running -> Blocked (waiting)
b. Running -> ready
c.. Blocked (waiting) -> ready
d. Ready -> running

QN=12 How many percent of the CPU time is wasted, when a computer system
has enough room to hold two program and these programs are idle
waiting for I/O half the time?
a. 50%
b.. 25%
c. 75%
d. None of the other choices

3
QN=13 How many ways is Thread implemented?
a. 1
b. 2
c.. 3
d. None of the other choices

QN=14 Critical Region (Section) concept used in interprocess communication is:

a.. A part of the program where the shared memory is accessed
b. A part of shared data
c. A part of shared memory
d. None of the other choices

QN=15 Which of the following statements is a hardware solution to the critical

region problem?
a.. TSL
b. Shared memory
c. Semaphore
d. None of the other choices

QN=16 Which of the following is true about Atomic action on semaphores?

a. Checking the value
b. Changing the value
c. Possibly going to sleep
d.. All of the other choices

4
QN=17 What is Higher-level proposal in the solution of Mutual exclusion and
Synchronization?
a. Message passing
b.. Monitors
c. Peterson's Solution
d. Disable Interrupts

QN=18 How many level of scheduling are used in computer

a. 1
b. 2
c.. 3
d. 4

QN=19 Which of the following is a preemptive scheduling algorithm

a. FCFS
b. Shortest Job First
c.. Round Robin
d. None of the other choices

QN=20 Five batch jobs A through E, arrive at a computer center at almost the
same time. They have estimated running times of 8, 6, 2, 10, and 4
minutes. Their (externally determined) priorities are 3, 5, 2, 1, and 4,
respectively, with 5 being the highest priority. Determine the average
waiting time for Priority scheduling. Ignore process switching overhead.
a.. 10,8 minutes
b. 12,8 minutes
c. 16,8 minutes
d. 54 minutes

5
QN=21 Assume jobs A-D arrive in quick succession in the READY queue. Using
round robin scheduling (quantum=4), the turnaround time for job B is
____.
Arrival time: 0 1 2 3
Job: ABCD
CPU cycle: 8 4 9 5
a.. 7
b. 20
c. 22
d. 24

QN=22 Which of following statements about the memory hierarchy is false?

a. Small amount of fast expensive memory – cache
b. Some medium-speed medium price main memory
c. Gigabytes of slow cheap disk storage
d.. None of the other choices

QN=23 In terms of speed the best method of Dynamic Storage-Allocation is:

a. Next fit
b.. First fit
c. Best fit
d. Worst fit

6
QN=24 Consider a swapping system in which the memory consists of the
following hole sizes: 10K, 4K, 20K, 15K, 9K. Assume best fit algorithm
is used. Which holes are taken for successive segment requests of 8K,
12K, 10K?
a. 20K, 15K, 10K
b. 10K, 15K, 20K
c.. 9K, 15K, 10K
d. 10K, 20K, 15K

QN=25 What is not the technique of implementation for Virtual Memory?

a. Segmentation
b.. Partition
c. Paging
d. All of the other choices

QN=26 Which of these statements about the Inverted Page Table are true?
a.. An entry contains the pair (process, virtual page) mapped into the
corresponding page frame
b. An entry contains the pair (process, offset) mapped into the
corresponding page frame
c. An entry contains the pair (segment, virtual page) mapped into the
corresponding page frame
d. An entry contains the pair (segment, offset) mapped into the
corresponding page frame

7
QN=27 If there are 128 pages and the page size is 32 K words, what is the length
of logical address?
a. 24 bits
b. 26 bits
c. 30 bits
d.. 22 bits

QN=28 A system with 32 bit virtual address. If the page size is 4 KB and each
table entry occupies 4 bytes, what is the size of the page table?
a. 1 MB
b. 2 MB
c.. 4 MB
d. 8 MB

QN=29 Which strategy is a simplest design for speeding up Paging?

a.. Page table is loaded into registers
b. Page table is loaded into main memory
c. Page table is loaded into disk
d. Page table is loaded into TLB

QN=30 Working set model is used for:

a.. Finding the minimum number of frames necessary for a job so that jobs
can be run without “thrashing”
b. Finding the average number of frames a job will need to run smoothly
c. Determining whether page replacement is needed
d. All of the other choices

8
QN=31 Which is not true about the method of backing store: “Paging to a static
swap area”?
a. The swap area on the disk is as large as the process virtual address space
b. Calculating the address in swap area requires knowing only where the
process’ paging area begins
c.. Requires a disk map in memory
d. A page that is in memory always have shadow copy on disk

QN=32 Which kind of tables is used in the segmentation?

a. Global Descriptor Table (GDT)
b. Local Descriptor Table (LDT )
c.. Both Global Descriptor Table (GDT) and Local Descriptor Table (LDT )
d. None of the other choices

QN=33 A computer has four page frames. The time of loading, time of last
access, and the R and M bits for each page are as shown below (the times
are in clock ticks):
Page Loaded Last ref. R M
-------------------------------------------------------------------------------------
0 226 280 0 0
1 160 265 0 1
2 110 270 1 0
3 120 285 1 1

Which page will NRU replace?

a.. 0
b. 1
c. 2
d. 3

9
QN=34 Consider a computer system that has cache memory, main memory
(RAM) and disk, and OS uses virtual memory. It takes 1 nsec to access a
byte from the cache, 10 nsec to access a byte from RAM, and 5 msec to
access a block of 1000 bytes from the disk. If a book has 1000 pages,
each with 25 lines of 80 characters each, How long it will take to
electronically scan the text for the case of the master copy being in each
of the level as one proceeds down the memory hierarchy (from inboard
memory to offline storage)?
a. 4 msec, 40 msec, 20 sec
b.. 2 msec, 20 msec, 10 sec
c. 1 msec, 10 msec, 10 sec
d. 1 msec, 10 msec, 5 sec

QN=35 Which of the following operating system has the concept of a process
hierarchy?
a. Win32
b. MS-DOS
c.. Unix
d. CP/M

QN=36 What is not a field in the process table that relates process management?
a. PC, PSW, SP
b. Process ID
c. CPU time used
d.. User ID, Group ID

10
QN=37 Which of the following is not correct about user-level threads?
a. User-level threads are more efficient than kernel threads, in the sense that
they do not need kernel calls to switch among threads
b. User-level threads cannot be preempted by clock interrupts unless the
whole process’ quantum has been used up
c.. With user-level threads, customized scheduling algorithms cannot be
implemented
d. If one user-level thread makes a blocking system call, the system will
block the entire process (which contains that user-level thread)

QN=38 At which level in Protection Rings on the Pentium the System calls
reside
a. 0
b.. 1
c. 2
d. 3

QN=39 Assume that the Page Table below is in effect. The number of lines per
page is 400. The actual memory location for line 1634 is ____.
Page Number Page Frame Number
0 8
1 10
2 5
3 11
a. 3
b. 1634
c. 4434
d.. None of the other choices

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