WGU D686 OPERATING SYSTEMS OA EXAM 2026 – COMPLETE
ACTUAL TEST BANK WITH CORRECT ANSWERS & RATIONALES
Question 1. What is the primary function of an operating system?
A. To provide a user interface for application software
B. To manage hardware resources and provide services for application programs
C. To compile source code into executable programs
D. To connect the computer to the internet
Correct Answer: B
Rationale:
The primary function of an operating system (OS) is to manage hardware resources
(CPU, memory, I/O devices) and provide an environment in which application programs
can execute. It acts as an intermediary between the user and the hardware. While
providing a user interface (A) is a function of some operating systems, it is not the
primary function. Compiling source code (C) is the job of a compiler. Connecting to the
internet (D) is a function of network software, not the OS itself.
Question 2. Which of the following is NOT a major function of an operating
system?
A. Process management
B. Memory management
C. File system management
D. Web browsing
Correct Answer: D
Rationale:
Web browsing is an application-level function, not a core function of the operating
system. The OS provides the platform on which a web browser runs. Process
management (A), memory management (B), and file system management (C) are all
fundamental responsibilities of an operating system.
Question 3. In operating system terminology, what is a "process"?
A. A program stored on disk
B. A program in execution
C. A thread of execution
D. A system call
,Correct Answer: B
Rationale:
A process is a program in execution. It includes the program code, current activity
(program counter, registers), and associated resources (memory, files). A program stored
on disk (A) is a passive entity. A thread (C) is a smaller unit of execution within a process.
A system call (D) is a request for OS services.
Question 4. What is the difference between a process and a thread?
A. A process is a program in execution; a thread is a lightweight process within a process
B. A thread is a program in execution; a process is a lightweight thread
C. They are the same thing
D. A process is stored on disk; a thread is stored in memory
Correct Answer: A
Rationale:
A process is a program in execution with its own address space and resources. A thread
is a smaller unit of execution within a process. Multiple threads within the same process
share the same address space and resources, making them "lightweight." Option B
reverses the definitions. Option C is incorrect. Option D is incorrect; both processes and
threads exist in memory during execution.
Question 5. What is a "context switch" in operating systems?
A. Switching from one user to another
B. Saving the state of a process and loading the state of another process
C. Switching from kernel mode to user mode
D. Switching from one CPU to another
Correct Answer: B
Rationale:
A context switch is the process of saving the state (context) of a currently running
process so that it can be resumed later, and loading the saved state of another process
to run. This allows the CPU to be shared among multiple processes. It is not about
switching users (A), switching modes (C), or switching CPUs (D).
Question 6. Which of the following is a valid process state in the classic five-state
process model?
,A. Running
B. Ready
C. Waiting
D. All of the above
Correct Answer: D
Rationale:
The classic five-state process model includes: New, Ready, Running, Waiting (or
Blocked), and Terminated. Running (A), Ready (B), and Waiting (C) are all valid states in
this model. Therefore, all of the above are correct.
Question 7. What does the "ready" state mean for a process?
A. The process is currently executing on the CPU
B. The process is waiting for an I/O operation to complete
C. The process is ready to execute but is waiting for CPU time
D. The process has finished execution
Correct Answer: C
Rationale:
A process in the ready state is ready to execute but is waiting in a queue for the CPU to
become available. It is not currently executing (A, that's the running state). It is not
waiting for I/O (B, that's the waiting/blocked state). It has not finished (D, that's the
terminated state).
Question 8. What is a "Process Control Block" (PCB)?
A. A data structure used by the OS to store information about a process
B. A hardware component that controls processes
C. A program that creates processes
D. A file that contains process code
Correct Answer: A
Rationale:
A Process Control Block (PCB) is a data structure in the operating system kernel that
contains information about a specific process. This includes the process ID, program
counter, CPU registers, memory limits, and open files. It is not a hardware component
(B), a program (C), or a file containing code (D).
Question 9. Which scheduling algorithm is non-preemptive?
, A. Round Robin
B. First-Come, First-Served (FCFS)
C. Shortest Remaining Time First (SRTF)
D. Priority (preemptive)
Correct Answer: B
Rationale:
First-Come, First-Served (FCFS) is a non-preemptive scheduling algorithm. Once a
process gets the CPU, it runs to completion or until it blocks. Round Robin (A), SRTF (C),
and preemptive Priority (D) are all preemptive algorithms, meaning the OS can interrupt
a running process.
Question 10. Which scheduling algorithm is designed to minimize average waiting
time?
A. First-Come, First-Served (FCFS)
B. Shortest Job First (SJF)
C. Round Robin
D. Priority
Correct Answer: B
Rationale:
Shortest Job First (SJF) is provably optimal for minimizing average waiting time. By
scheduling the shortest jobs first, it reduces the waiting time for all subsequent jobs.
FCFS (A) can lead to the convoy effect. Round Robin (C) is good for time-sharing but
does not minimize average waiting time. Priority (D) depends on the priority
assignments.
Question 11. In Round Robin scheduling, what is a "time quantum"?
A. The total time a process needs to complete
B. The maximum time a process can run before being preempted
C. The time it takes to switch between processes
D. The time a process spends waiting in the ready queue
Correct Answer: B
Rationale:
In Round Robin scheduling, a time quantum (or time slice) is the maximum amount of
time a process can run on the CPU before it is preempted and moved to the back of the
ACTUAL TEST BANK WITH CORRECT ANSWERS & RATIONALES
Question 1. What is the primary function of an operating system?
A. To provide a user interface for application software
B. To manage hardware resources and provide services for application programs
C. To compile source code into executable programs
D. To connect the computer to the internet
Correct Answer: B
Rationale:
The primary function of an operating system (OS) is to manage hardware resources
(CPU, memory, I/O devices) and provide an environment in which application programs
can execute. It acts as an intermediary between the user and the hardware. While
providing a user interface (A) is a function of some operating systems, it is not the
primary function. Compiling source code (C) is the job of a compiler. Connecting to the
internet (D) is a function of network software, not the OS itself.
Question 2. Which of the following is NOT a major function of an operating
system?
A. Process management
B. Memory management
C. File system management
D. Web browsing
Correct Answer: D
Rationale:
Web browsing is an application-level function, not a core function of the operating
system. The OS provides the platform on which a web browser runs. Process
management (A), memory management (B), and file system management (C) are all
fundamental responsibilities of an operating system.
Question 3. In operating system terminology, what is a "process"?
A. A program stored on disk
B. A program in execution
C. A thread of execution
D. A system call
,Correct Answer: B
Rationale:
A process is a program in execution. It includes the program code, current activity
(program counter, registers), and associated resources (memory, files). A program stored
on disk (A) is a passive entity. A thread (C) is a smaller unit of execution within a process.
A system call (D) is a request for OS services.
Question 4. What is the difference between a process and a thread?
A. A process is a program in execution; a thread is a lightweight process within a process
B. A thread is a program in execution; a process is a lightweight thread
C. They are the same thing
D. A process is stored on disk; a thread is stored in memory
Correct Answer: A
Rationale:
A process is a program in execution with its own address space and resources. A thread
is a smaller unit of execution within a process. Multiple threads within the same process
share the same address space and resources, making them "lightweight." Option B
reverses the definitions. Option C is incorrect. Option D is incorrect; both processes and
threads exist in memory during execution.
Question 5. What is a "context switch" in operating systems?
A. Switching from one user to another
B. Saving the state of a process and loading the state of another process
C. Switching from kernel mode to user mode
D. Switching from one CPU to another
Correct Answer: B
Rationale:
A context switch is the process of saving the state (context) of a currently running
process so that it can be resumed later, and loading the saved state of another process
to run. This allows the CPU to be shared among multiple processes. It is not about
switching users (A), switching modes (C), or switching CPUs (D).
Question 6. Which of the following is a valid process state in the classic five-state
process model?
,A. Running
B. Ready
C. Waiting
D. All of the above
Correct Answer: D
Rationale:
The classic five-state process model includes: New, Ready, Running, Waiting (or
Blocked), and Terminated. Running (A), Ready (B), and Waiting (C) are all valid states in
this model. Therefore, all of the above are correct.
Question 7. What does the "ready" state mean for a process?
A. The process is currently executing on the CPU
B. The process is waiting for an I/O operation to complete
C. The process is ready to execute but is waiting for CPU time
D. The process has finished execution
Correct Answer: C
Rationale:
A process in the ready state is ready to execute but is waiting in a queue for the CPU to
become available. It is not currently executing (A, that's the running state). It is not
waiting for I/O (B, that's the waiting/blocked state). It has not finished (D, that's the
terminated state).
Question 8. What is a "Process Control Block" (PCB)?
A. A data structure used by the OS to store information about a process
B. A hardware component that controls processes
C. A program that creates processes
D. A file that contains process code
Correct Answer: A
Rationale:
A Process Control Block (PCB) is a data structure in the operating system kernel that
contains information about a specific process. This includes the process ID, program
counter, CPU registers, memory limits, and open files. It is not a hardware component
(B), a program (C), or a file containing code (D).
Question 9. Which scheduling algorithm is non-preemptive?
, A. Round Robin
B. First-Come, First-Served (FCFS)
C. Shortest Remaining Time First (SRTF)
D. Priority (preemptive)
Correct Answer: B
Rationale:
First-Come, First-Served (FCFS) is a non-preemptive scheduling algorithm. Once a
process gets the CPU, it runs to completion or until it blocks. Round Robin (A), SRTF (C),
and preemptive Priority (D) are all preemptive algorithms, meaning the OS can interrupt
a running process.
Question 10. Which scheduling algorithm is designed to minimize average waiting
time?
A. First-Come, First-Served (FCFS)
B. Shortest Job First (SJF)
C. Round Robin
D. Priority
Correct Answer: B
Rationale:
Shortest Job First (SJF) is provably optimal for minimizing average waiting time. By
scheduling the shortest jobs first, it reduces the waiting time for all subsequent jobs.
FCFS (A) can lead to the convoy effect. Round Robin (C) is good for time-sharing but
does not minimize average waiting time. Priority (D) depends on the priority
assignments.
Question 11. In Round Robin scheduling, what is a "time quantum"?
A. The total time a process needs to complete
B. The maximum time a process can run before being preempted
C. The time it takes to switch between processes
D. The time a process spends waiting in the ready queue
Correct Answer: B
Rationale:
In Round Robin scheduling, a time quantum (or time slice) is the maximum amount of
time a process can run on the CPU before it is preempted and moved to the back of the
