WGU D487 OA – OPERATING SYSTEMS ACTUAL
EXAM 150 Most Tested Questions & Answers with
Rationales Western Governors University (WGU) –
Computer Science / IT
Question 1
Which of the following is the primary function of an operating system?
A) Manage hardware resources and provide an interface between user and hardware
B) Compile source code into machine code
C) Store data permanently
D) Design user interfaces
Correct Answer: A
Rationale: The OS acts as an intermediary between the user/applications and the computer
hardware, managing CPU, memory, I/O devices, and storage.
Question 2
In a multitasking operating system, what is a process?
A) A program in execution, including program counter, registers, and stack
B) A static set of instructions
C) A file stored on disk
D) A scheduling algorithm
Correct Answer: A
Rationale: A process is an active entity – a program in execution with its own address space,
program counter, registers, and stack. A program is passive.
Question 3
Which scheduling algorithm is non-preemptive?
A) Round Robin (RR)
,B) Shortest Job First (SJF) non-preemptive
C) Preemptive Priority
D) Multilevel Feedback Queue
Correct Answer: B
Rationale: Non-preemptive SJF allows a process to run to completion once it is selected. RR
and preemptive priority are preemptive.
Question 4
What is a "context switch"?
A) The process of saving the state of one process and loading the state of another
B) Switching between user mode and kernel mode
C) Changing the priority of a process
D) Moving data between memory and disk
Correct Answer: A
Rationale: A context switch occurs when the CPU switches from one process to another, saving
the current process's state (registers, PC) and restoring the next process's state.
Question 5
In paging memory management, what is a "page fault"?
A) An attempt to access a page that is not currently in physical memory
B) A hardware error in memory
C) A protection violation
D) A segmentation fault
Correct Answer: A
Rationale: A page fault occurs when a process tries to access a virtual memory page that is not
loaded into physical RAM, requiring the OS to load it from disk.
Question 6
Which of the following is a necessary condition for deadlock?
A) Mutual exclusion
B) Hold and wait
C) No preemption
D) Circular wait
Correct Answer: D (all four are necessary, but most tested is circular wait)
,Rationale: The four necessary conditions for deadlock are: mutual exclusion, hold and wait, no
preemption, and circular wait. All four must be present.
Question 7
Which scheduling algorithm aims to minimize average waiting time?
A) First Come First Serve (FCFS)
B) Shortest Job First (SJF)
C) Round Robin (RR)
D) Priority Scheduling
Correct Answer: B
Rationale: SJF is optimal in terms of minimizing average waiting time, but it may cause
starvation of longer processes.
Question 8
What is the purpose of the Translation Lookaside Buffer (TLB)?
A) Cache frequently used page table entries to speed up address translation
B) Store the entire page table
C) Manage disk I/O
D) Schedule processes
Correct Answer: A
Rationale: The TLB is a hardware cache that stores recent virtual-to-physical address
translations, reducing the need to access the page table in memory.
Question 9
Which of the following is a disadvantage of contiguous memory allocation?
A) Internal fragmentation
B) External fragmentation
C) High overhead
D) Complexity
Correct Answer: B
Rationale: Contiguous allocation leads to external fragmentation – free memory becomes
scattered in small holes that cannot accommodate large processes.
, Question 10
What is a "race condition" in concurrent programming?
A) Two or more processes accessing shared data concurrently, with the final outcome
dependent on timing
B) A deadlock situation
C) A process waiting indefinitely
D) A priority inversion
Correct Answer: A
Rationale: A race condition occurs when multiple processes or threads access shared data
simultaneously, and the result depends on the unpredictable order of execution.
Question 11
Which synchronization primitive allows only one thread to access a shared resource at a time?
A) Semaphore (binary)
B) Mutex
C) Spinlock
D) All of the above
Correct Answer: D
Rationale: Binary semaphores, mutexes, and spinlocks all provide mutual exclusion; mutex is
most commonly used for this purpose.
Question 12
What is "thrashing" in virtual memory?
A) Excessive paging due to insufficient physical memory, causing low CPU utilization
B) A process exceeding its time quantum
C) A page fault that cannot be resolved
D) A deadlock situation
Correct Answer: A
Rationale: Thrashing occurs when the system spends most of its time paging (moving pages
between memory and disk) rather than executing processes.
Question 13
Which file allocation method is most susceptible to external fragmentation?
A) Contiguous allocation
B) Linked allocation
EXAM 150 Most Tested Questions & Answers with
Rationales Western Governors University (WGU) –
Computer Science / IT
Question 1
Which of the following is the primary function of an operating system?
A) Manage hardware resources and provide an interface between user and hardware
B) Compile source code into machine code
C) Store data permanently
D) Design user interfaces
Correct Answer: A
Rationale: The OS acts as an intermediary between the user/applications and the computer
hardware, managing CPU, memory, I/O devices, and storage.
Question 2
In a multitasking operating system, what is a process?
A) A program in execution, including program counter, registers, and stack
B) A static set of instructions
C) A file stored on disk
D) A scheduling algorithm
Correct Answer: A
Rationale: A process is an active entity – a program in execution with its own address space,
program counter, registers, and stack. A program is passive.
Question 3
Which scheduling algorithm is non-preemptive?
A) Round Robin (RR)
,B) Shortest Job First (SJF) non-preemptive
C) Preemptive Priority
D) Multilevel Feedback Queue
Correct Answer: B
Rationale: Non-preemptive SJF allows a process to run to completion once it is selected. RR
and preemptive priority are preemptive.
Question 4
What is a "context switch"?
A) The process of saving the state of one process and loading the state of another
B) Switching between user mode and kernel mode
C) Changing the priority of a process
D) Moving data between memory and disk
Correct Answer: A
Rationale: A context switch occurs when the CPU switches from one process to another, saving
the current process's state (registers, PC) and restoring the next process's state.
Question 5
In paging memory management, what is a "page fault"?
A) An attempt to access a page that is not currently in physical memory
B) A hardware error in memory
C) A protection violation
D) A segmentation fault
Correct Answer: A
Rationale: A page fault occurs when a process tries to access a virtual memory page that is not
loaded into physical RAM, requiring the OS to load it from disk.
Question 6
Which of the following is a necessary condition for deadlock?
A) Mutual exclusion
B) Hold and wait
C) No preemption
D) Circular wait
Correct Answer: D (all four are necessary, but most tested is circular wait)
,Rationale: The four necessary conditions for deadlock are: mutual exclusion, hold and wait, no
preemption, and circular wait. All four must be present.
Question 7
Which scheduling algorithm aims to minimize average waiting time?
A) First Come First Serve (FCFS)
B) Shortest Job First (SJF)
C) Round Robin (RR)
D) Priority Scheduling
Correct Answer: B
Rationale: SJF is optimal in terms of minimizing average waiting time, but it may cause
starvation of longer processes.
Question 8
What is the purpose of the Translation Lookaside Buffer (TLB)?
A) Cache frequently used page table entries to speed up address translation
B) Store the entire page table
C) Manage disk I/O
D) Schedule processes
Correct Answer: A
Rationale: The TLB is a hardware cache that stores recent virtual-to-physical address
translations, reducing the need to access the page table in memory.
Question 9
Which of the following is a disadvantage of contiguous memory allocation?
A) Internal fragmentation
B) External fragmentation
C) High overhead
D) Complexity
Correct Answer: B
Rationale: Contiguous allocation leads to external fragmentation – free memory becomes
scattered in small holes that cannot accommodate large processes.
, Question 10
What is a "race condition" in concurrent programming?
A) Two or more processes accessing shared data concurrently, with the final outcome
dependent on timing
B) A deadlock situation
C) A process waiting indefinitely
D) A priority inversion
Correct Answer: A
Rationale: A race condition occurs when multiple processes or threads access shared data
simultaneously, and the result depends on the unpredictable order of execution.
Question 11
Which synchronization primitive allows only one thread to access a shared resource at a time?
A) Semaphore (binary)
B) Mutex
C) Spinlock
D) All of the above
Correct Answer: D
Rationale: Binary semaphores, mutexes, and spinlocks all provide mutual exclusion; mutex is
most commonly used for this purpose.
Question 12
What is "thrashing" in virtual memory?
A) Excessive paging due to insufficient physical memory, causing low CPU utilization
B) A process exceeding its time quantum
C) A page fault that cannot be resolved
D) A deadlock situation
Correct Answer: A
Rationale: Thrashing occurs when the system spends most of its time paging (moving pages
between memory and disk) rather than executing processes.
Question 13
Which file allocation method is most susceptible to external fragmentation?
A) Contiguous allocation
B) Linked allocation
