Operating Systems Final Exam Questions

Front 1

A deadlock-free solution of synchronization problem eliminates the possibility of starvation.

Back 1

False

Front 2

A page fault must be preceded by a TLB miss.

Back 2

True

Front 3

A relocation register is used to check for invalid memory addresses generated by a CPU.

Back 3

False

Front 4

A system in an unsafe state will ultimately deadlock.

Back 4

False

Front 5

Fragmentation does not occur in a paging system.

Back 5

False

Front 6

Hashed page tables are particularly useful for processes with sparse address spaces.

Back 6

True

Front 7

If a resource-allocation graph has a cycle, the system must be in a deadlocked state.

Back 7

False

Front 8

If the page-fault rate is too high, the process may have too many frames.

Back 8

False

Front 9

In general, virtual memory decreases the degree of multiprogramming in a system.

Back 9

False

Front 10

Indexed allocation of disk blocks may require substantial overhead for its index block.

Back 10

True

Front 11

Inverted page tables require each process to have its own page table.

Back 11

True

Front 12

Linked allocation of disk blocks suffers from external fragmentation.

Back 12

False

Front 13

Mutex locks and binary semaphores are essentially the same thing.

Back 13

True

Front 14

Metadata includes all of the file-system structure, including the actual data (or contents of the file).

Back 14

False

Front 15

Monitors are a theoretical concept and are not practiced in modern programming languages

Back 15

False

Front 16

Mutex locks and counting semaphores are essentially the same thing.

Back 16

False

Front 17

On a system with demand-paging, a process will experience a high page fault rate when the process begins execution.

Back 17

True

Front 18

Protocols to prevent hold-and-wait conditions typically also prevent starvation.

Back 18

False

Front 19

Race conditions are prevented by requiring that critical regions be protected by locks.

Back 19

True

Front 20

Spinlocks are useful for multiprocessor systems where a thread can run in a busy-loop.

Back 20

True

Front 21

The exec() system call creates a new process.

Back 21

False

Front 22

The most common approach to file protection is to make access dependent upon the identity of the user.

Back 22

True

Front 23

The value of a counting semaphore can range only between 0 and 1.

Back 23

False

Front 24

The wait-for graph scheme is not applicable to a resource allocation system with multiple instances of each resource type.

Back 24

True

Front 25

The x86-64 bit architecture only uses 48 of the 64 possible bits for representing virtual address space.

Back 25

True

Front 26

There is a 1:1 correspondence between the number of entries in the TLB and the number of entries in the page table.

Back 26

False

Front 27

_____ can be used to prevent busy waiting when implementing a semaphore.

A. Spinlocks

B. Mutex lock

C. Allowing the wait() operation to succeed

D. Waiting queues

Back 27

D. Waiting Queues

Front 28

_____ is the dynamic storage-allocation algorithm which results in the smallest leftover hole

in memory.

A. First fit

B. Best fit

C. Worst fit

D. None of the above

Back 28

B. Best Fit

Front 29

_____ is the method of binding instructions and data to memory performed by most

general-purpose operating systems.

A. Interrupt binding

B. Execution time binding

C. Load-time binding

D. Compile time binding

Back 29

B. Execution time Binding

Front 30

_____ is the page replacement algorithm implemented on most systems.

A. LRU

B. FIFO

C. Least frequently used

D. Most frequently used

Back 30

A. LRU

Front 31

____________ occurs when a higher-priority process needs to access a data structure that

is currently being accessed by a lower-priority process.

A. Priority inversion

B. Deadlock

C. A critical section

D. A race condition

Back 31

A. Priority Inversion

Front 32

A _____ could be preempted from a process.

A. mutex lock

B. file lock

C. semaphore

D. CPU

Back 32

D. CPU

Front 33

A cycle in a resource-allocation graph is ____.

A. a sufficient condition for a deadlock in the case that each resource has more than once

instance

B. a necessary and sufficient condition for deadlock in the case that each resource has

more than one instance

C. a necessary and sufficient condition for a deadlock in the case that each resource has

exactly one instance

D. is neither necessary nor sufficient for indicating deadlock in the case that each resource

has exactly one instance

Back 33

C. a necessary and sufficient condition for a deadlock in the case that each resource has

exactly one instance

Front 34

A deadlocked state occurs whenever ____.

A. a process is unable to release its request for a resource after use

B. every process in a set is waiting for an event that can only be caused by another process in the set

C. the system has no available free resources

D. a process is waiting for I/O to a device that does not exist

Back 34

B. every process in a set is waiting for an event that can only be caused by another process in the set

Front 35

A race condition ____.

A. results when several threads try to access the same data concurrently

B. results when several threads try to access and modify the same data concurrently

C. will result only if the outcome of execution does not depend on the order in which

instructions are executed

D. None of the above

Back 35

B) results when several threads try to access and modify the same data concurrently

Front 36

A solution to the critical section problem does not have to satisfy which of the following

requirements?

A. mutual exclusion

B. bounded waiting

C. progress

D. atomicity

Back 36

C) atomicity

Front 37

A(n) ____ page table has one page entry for each real page (or frame) of memory.

A. virtual

B. inverted

C. clustered

D. forward-mapped

Back 37

B. inverted

Front 38

A(n) _______ refers to where a process is accessing/updating shared data.

A. entry section

B. critical section

C. mutex

D. test-and-set

Back 38

B. Critical Section

Front 39

An acyclic-graph directory structure ____.

A. is less complicated than a simple tree-structured directory structure.

B. allows the sharing of files.

C. does not allow the sharing of files.

D. is less flexible than a simple tree-structured directory structure.

Back 39

B. allows the sharing of files.

Front 40

An address generated by a CPU is referred to as a ____.

A. Memory-Management Unit (MMU) generated address

B. physical address

C. logical address

D. post relocation register address

Back 40

C. Logical Address

Front 41

An instruction that executes atomically ____.

A. must consist of only one machine instruction

B. executes as a single, uninterruptible unit

C. cannot be used to solve the critical section problem

D. All of the above

Back 41

B. executes as a single, uninterruptible unit

Front 42

Assume a system has a TLB hit ratio of 90%. It requires 15 nanoseconds to access the

TLB, and 85 nanoseconds to access main memory. What is the effective memory access

time in nanoseconds for this system?

A. 22

B. 176.5

C. 108.5

D. 100

Back 42

C. 108.5

Front 43

Consider a logical address uses 18 bits page number to represent an entry in a

conventional page table. How many entries are in the conventional page table?

A. 1024

B. 18

C. 262144

D. 1048576

Back 43

C. 262144

Front 44

Consider a logical address with a page size of 8 KB. How many bits must be used to

represent the page offset in the logical address?

A. 13

B. 10

C. 12

D. 8

Back 44

A. 13

Front 45

Given the logical address 0xAEF9 (in hexadecimal) with a page size of 256 bytes, what is

the page number?

A. 0xA

B. 0xF9

C. 0xAE

D. 0x00F9

Back 45

C. 0xAE

Front 46

Consider a 32-bit address for a two-level paging system with an 8 KB page size. The outer

page table has 1024 entries. How many bits are used to represent the second-level (inner)

page table?

A. 9

B. 12

C. 10

D. 8

Back 46

A. 9

Front 47

In an environment where several processes may open the same file at the same time,

____.

A. the operating system typically uses only one internal table to keep track of open files

B. the operating system typically uses two internal tables called the system-wide and per-
disk tables to keep track of open files

C. the operating system typically uses three internal tables called the system-wide, per-
disk, and per-partition tables to keep track of open files

D. the operating system typically uses two internal tables called the system-wide and per-
process tables to keep track of open files

Back 47

D. the operating system typically uses two internal tables called the system-wide and per-
process tables to keep track of open files

Front 48

In Peterson's solution, the ____ variable indicates if a process is ready to enter its critical

section.

A. lock

B. turn

C. turn[i]

D. flag[i]

Back 48

D. flag[i]

Front 49

Suppose a program is operating with execution-time binding and the physical address

generated is 300. The relocation register is set to 100. What is the corresponding logical

address?

A. 100

B. 200

C. 400

D. 300

Back 49

B. 200

Front 50

Suppose that the operating system uses two internal tables to keep track of open files.

Process A has two files open and process B has three files open. Two files are shared

between the two processes. How many entries are in the per-process table of process A,

the per-process table of process B, and the system-wide tables, respectively?

A. 2, 3, 1

B. 2, 3, 5

C. 2, 3, 3

D. 5, 5, 5

Back 50

C. 2, 3, 3

Front 51

Suppose that there are ten resources available to three processes. At time 0, the following

data is collected. The table indicates the process, the maximum number of resources

needed by the process, and the number of resources currently owned by each process.

Which of the following correctly characterizes this state?

Process Maximum Needs Currently Owned

P0 10 4

P1 3 1

P2 6 4
A. The state cannot be determined.

B. It is not safe.

C. It is safe.

D. It is an impossible state.

Back 51

B. It is not safe.

Front 52

Suppose we have the following page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and that there

are three frames within our system. Using the LRU replacement algorithm, what is the

number of page faults for the given reference string?

A. 9

B. 8

C. 13

D. 10

Back 52

B. 8

Front 53

Given the reference string of page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and a system with three page frames, what is the final configuration of the three frames after the LRU algorithm is applied?
A. 1, 2, 3
B. 3, 1, 4
C. 1, 3, 4
D. 4, 1, 2

Back 53

B. 3, 1, 4

Front 54

Suppose we have the following page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and that there are three frames within our system. Using the optimal replacement algorithm, what is the number of page faults for the given reference string?
A. 6
B. 7
C. 8
D. 5

Back 54

A. 6

Front 55

The first readers-writers problem ____.
A. requires that no reader will be kept waiting unless a reader has already obtained permission to use the shared database.
B. is not used to test synchronization primitives.
C. requires that no reader will be kept waiting unless a writer has already obtained permission to use the shared database.
D. requires that, once a writer is ready, that writer performs its write as soon as possible.

Back 55

C. requires that no reader will be kept waiting unless a writer has already obtained permission to use the shared database.

Front 56

What is the correct order of operations for protecting a critical section using mutex locks?
A. release() followed by acquire()
B. acquire() followed by release()
C. wait() followed by signal()
D. signal() followed by wait()

Back 56

B. acquire() followed by release()

Front 57

What is the purpose of the mutex semaphore in the implementation of the bounded-buffer problem using semaphores?
A. It indicates the number of empty slots in the buffer.
B. It indicates the number of occupied slots in the buffer.
C. It controls access to the shared buffer.
D. It ensures mutual exclusion.

Back 57

D. It ensures mutual exclusion.

Front 58

When using semaphores, a process invokes the wait() operation before accessing its critical section, followed by the signal() operation upon completion of its critical section. Consider reversing the order of these two operations—first calling signal(), then calling wait(). What would be a possible outcome of this?
A. Starvation is possible.
B. Deadlock is possible.
C. Several processes could be active in their critical sections at the same time.
D. Mutual exclusion is still assured.

Back 58

C. Several processes could be active in their critical sections at the same time.

Front 59

Which of the following allocation methods ensures that only one access is needed to get a disk block using direct access for a file?
A. indexed allocation
B. contiguous allocation
C. linked allocation
D. hashed allocation

Back 59

B. contiguous allocation

Front 60

Which of the following is a benefit of allowing a program that is only partially in memory to execute?
A. Programs can be written to use more memory than is available in physical memory.
B. CPU utilization and throughput is increased.
C. Less I/O is needed to load or swap each user program into memory.
D. All of the above

Back 60

D. all of the above

Front 61

Which of the following is not a reason explaining why mobile devices generally do not support swapping?
A. Limited space constraints of flash memory.
B. Limited number of writes of flash memory.
C. Poor throughput between main memory and flash memory.
D. Small size of mobile applications do not require use of swap space.

Back 61

D. Small size of mobile applications do not require use of swap space.

Front 62

Which of the following statements is true?
A. An unsafe state is necessarily, and by definition, always a deadlocked state.
B. An unsafe state may lead to a deadlocked state.
C. A safe state is a deadlocked state.
D. A safe state may lead to a deadlocked state.

Back 62

B. An unsafe state may lead to a deadlocked state.

Front 63

With segmentation, a logical address consists of _____.
A. segment name and offset
B. segment number and page number
C. segment number and offset
D. segment table and segment number

Back 63

C. segment number and offset