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OSG 101-200 - abc

Operating System (Trường Đại học FPT)

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 1. The basic idea behind the microkernel design is:
Only one module runs in kernel mode
To achive high reliability by splitting operating system up into small, well-defined modules
All other modules run as relatively powerless ordinary user processes
All of the other choices

2. OS Win32 use system call , while OS Unix use system call to create a new
process
fork, CreateProcess
CreateProcess; fork
copy, CreateProcess
CreateProcess; copy

3. Which statement about disabling interrupts to resolve race conditions is wrong?

Disabling/enabling interrupts may negatively affect the I/O system
User-mode programs are the best place to invoke disableInterrupt()
In theory, a program can disable interrupts when it enters a critical section, and re-enable
interrupts
when finished with a critical section, to eliminate race conditions
Programs with infinite loops in their critical sections are a significant problem with the interrupt-
based
approach

4. Which of the events that causes the processes to be created, when an operation
system is
booted?
System initialization
Execution of a process creation system call
User request to create a new process
Initiation of a batch job

5. Which of the following process state transitions is legal?

Blocked (waiting) -> runnig
Ready -> Blocked (waiting)
None of the other choices
Running -> ready

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

7. Which of the following process state transitions is correct, when the operating system
discovers that process can not continue right now because of is not enough resource?

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Running -> ready
Blocked (waiting) -> ready
Ready -> running
Running -> Blocked (waiting)

8. Which of the following statements about semaphores is true?

If several processes attempt a P(S) operation simultaneously, only one process should be allowed
to
proceed
A semaphore implementation should guarantee that processes do not suffer indefinite
postponement
All of the other choices
P and V (Down and Up) operations should be indivisible operations

9. Which of the following conditions must be held to provide good solution for mutual
exclusion?
No process running outside its critical region may block another process
No process must wait forever to enter its critical region
No two processes simultaneously in critical region
All of the other choices

10. In terms of disk storage efficiency, the method of "Backing up pages dynamically" in
comparison with the method of "Paging to a static swap area" is
Nearly equal
Better
Equal
Worse

11. A well-known operating system for Handheld Computer is:

e-COS
TinyOS
Symbian OS and Palm OS
MS-DOS

12. Critical Region (Section) concept used in interprocess communication is:

None of the other choices
A part of shared data
A part of shared memory
A part of the program where the shared memory is accessed

13. When there is an excessive amount of page swapping between main memory and
secondary
storage, the operation becomes inefficient, which is called .
excessive demand paging
over swapping

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hot swapping
thrashing

14. Suppose a virtual address space of 2^24 words and the page size is 2^12 words. If the
virtual
address is 123456 in Hexadecimal, what would be the page number in Hexadecimal?
12345
1234
123456
123

15. 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?
4 MB
8 MB
2 MB
1 MB

16. Which of these statements about the Inverted Page Table are true?
An entry contains the pair (process, offset) mapped into the corresponding page frame
An entry contains the pair (segment, virtual page) mapped into the corresponding page frame
An entry contains the pair (process, virtual page) mapped into the corresponding page frame
An entry contains the pair (segment, offset) mapped into the corresponding page frame

17. In terms of speed the best method of Dynamic Storage-Allocation is:

Worst fit
Best fit
Next fit
First fit

18. A process where no concurrency inside process; everything happens sequentially is called :
None of the other choices
Sequential access process
Sequential process
Random access process

19. What is not a field in the process table that relates process management?
CPU time used
PC, PSW, SP
User ID, Group ID
Process ID

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

21. Which is the maximum partition size, if the FAT type is FAT-32 and the block size is 4
KB?
256 MB
1 TB
512 MB
128 MB

22. Where should be put the page replacement algorithm In Mach model of Page fault
handling
with an external pager?
In the page fault handler that is part of the kernel
In the external pager running in user space
All of the other choices
In the low-level MMU handler

23. 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)?
4 msec, 40 msec, 20 sec
1 msec, 10 msec, 5 sec
2 msec, 20 msec, 10 sec
1 msec, 10 msec, 10 sec

24. What is correct about trap instructions and interrupts?

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

25. Which of the following operating system has the concept of a process hierarchy?
Win32
CP/M
Unix
MS-DOS

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 26. As one proceeds down the memory hierarchy (from inboard memory to offline storage),
which of the following conditions is correct?
Decreasing access time
Increasing capacity
Increasing cost per bit
None of the other choices

27. Assume that the Page Table below is in effect: Page Number: 0 1 2 3; Page Frame
Number: 8 10 5 11. The number of lines per page is 400. The actual memory location
for line 1634 is
.
None of the other choices
1634
3
4434

28. 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?
25%
75%
None of the other choices
50%

29. Working set model is used for:

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

30. An arrival message causes the system to create a new thread to handle this message. This
new
thread is call
Activator
Upcall
Pop-up
Distributed

31. What is Higher-level proposal in the solution of Mutual exclusion and Synchronization?
Monitors
Message Disable
Interrupts passing
Peterson's Solution

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 32. What is the characteristic of the second generation of operating system?
ICs and multiprogramming
Transistors, batch systems
Vacuum tubes, plug boards
Personal computers, single user, multitasking

33. What is the main characteristic of real-time operating system?

Multiple CPU
Time-sharing
Time is key parameter
Many I/O devices

34. LRU replaces the page that has spent the

longest time in memory
shortest time in memory
longest time in memory without being referenced
shortest time in memory without being referenced

35. Which of the following is not correct about user-level threads?

User-level threads are more efficient than kernel threads, in the sense that they do not need
kernel
calls to switch among threads
With user-level threads, customized scheduling algorithms cannot be implemented
User-level threads cannot be preempted by clock interrupts unless the whole process'
quantum has
been used up
If one user-level thread makes a blocking system call, the system will block the entire process
(which
contains that user-level thread)

36. 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).
Which page will NRU
replace?
Captionless Image
0
1
2
3

37. A computer with a 32-bit address uses a two-level page table. Virtual addresses are split
into a 9-bit top-level page table field, an 11-bit second-level page table field, and an
offset. How
many pages are there in the address space?
2^23 pages
2^20 pages
2^22 pages
2^21 pages

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 38. Which is not true about "Backing up pages dynamically"?
Requires a disk map in memory
Pages do not have fixed swap area on the disk
When a page is swapped out, an empty disk page is chosen on the fly and disk map is
updated
accordingly
Needs less main memory than the method "Paging to a static swap area"

39. What is not the technique of implementation for Virtual Memory?

Partition
Segmentation
Paging
All of the other choices

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

41. Which of the following actions generates an external interrupt?

A page that does not exist in the main memory is accessed by the virtual storage
management.
A system call instruction is executed.
Division by zero occurs
An input/output operation is completed

42. Which is not true about the method of backing store: "Paging to a static swap area"?
The swap area on the disk is as large as the process virtual address space
Calculating the address in swap area requires knowing only where the process' paging area
begins
A page that is in memory always have shadow copy on disk
Requires a disk map in memory

43. The page size that is too small will generate

More difficult to calculate actual position
Very long Page tables
Excessive internal fragmentation
Excessive external fragmentation

44. 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: A B C D;
CPU cycle: 8 4 9 5

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24
20
22
7

45. Which of the following is true about Atomic action on semaphores?

Changing the value
Possibly going to sleep
Checking the value
All of the other choices

46. Which of the following statements is a hardware solution to the critical region problem?
None of the other choices
Semaphore
Shared memory
TSL

47. 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.
12,8 minutes
10,8 minutes
54 minutes
16,8 minutes

48. If there are 128 pages and the page size is 32 K words, what is the length of logical
address?
24 bits
26 bits
30 bits
22 bits

49. Which of the following information bits in the entry of page table is used to indicate
locked
page?
Modified bit
Caching disabled
Present/absent bit
Referenced bit

50. The modified/dirty bit is used for the purpose of:

Dynamic allocation of memory used by one process to another
Reduce the average time required to service page faults

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None of the other choices
Implementing FIFO page replacement algorithm

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