SA1 Operating Systems Lecture Ultimate Exam
**Question 1. Which of the following best describes a monolithic kernel architecture?**
A) The kernel provides only minimal services and runs most services in user space.
B) All operating-system services run in kernel mode as a single large program.
C) The kernel is divided into separate modules that can be loaded and unloaded at runtime.
D) The kernel uses a microkernel for inter-process communication.
Answer: B
Explanation: In a monolithic kernel, all core services (file system, device drivers, networking, etc.)
execute in kernel mode within one large address space, unlike microkernels that keep most services in
user space.
**Question 2. What is the primary advantage of a microkernel compared to a monolithic kernel?**
A) Faster context switches.
B) Simpler device driver development.
C) Improved fault isolation because most services run in user mode.
D) Reduced memory usage due to a single address space.
Answer: C
Explanation: Microkernels keep only essential functions in kernel mode; other services run in user mode,
so a failure in a driver does not crash the entire system.
**Question 3. In a layered operating-system architecture, which layer typically interacts directly with
hardware?**
A) Application layer.
B) System-call interface layer.
C) Hardware abstraction layer.
D) User-level library layer.
Answer: C
Explanation: The hardware abstraction layer (HAL) provides a uniform interface to the underlying
hardware and is the lowest layer that directly accesses devices.
**Question 4. Which system-call interface is standard for Unix-like operating systems?**
, SA1 Operating Systems Lecture Ultimate Exam
A) Win32 API.
B) POSIX.
C) Java Native Interface.
D) DirectX.
Answer: B
Explanation: POSIX (Portable Operating System Interface) defines a set of standard system calls and
utilities for Unix-like systems.
**Question 5. What is the purpose of the “dual-mode” operation in modern operating systems?**
A) To allow two CPUs to execute the same instruction simultaneously.
B) To separate user-level code from privileged kernel code for protection.
C) To enable two different scheduling algorithms at once.
D) To provide both 32-bit and 64-bit execution modes.
Answer: B
Explanation: Dual-mode operation enforces protection by running user applications in a restricted mode
and kernel code in a privileged mode.
**Question 6. Which of the following events typically triggers a context switch?**
A) Completion of a disk read operation.
B) A timer interrupt expiring.
C) A user pressing the power button.
D) The BIOS POST routine.
Answer: B
Explanation: A timer interrupt signals the scheduler that the current process has exhausted its time
quantum, prompting a context switch.
**Question 7. In process management, the Process Control Block (PCB) does NOT contain which of the
following?**
A) Process state.
B) CPU register contents.
, SA1 Operating Systems Lecture Ultimate Exam
C) The source code of the process.
D) Memory management information.
Answer: C
Explanation: The PCB stores runtime information such as state, registers, and memory data, but not the
process’s source code.
**Question 8. Which state transition occurs when a process moves from “Running” to “Waiting”?**
A) It is preempted by the scheduler.
B) It voluntarily yields the CPU for I/O.
C) It terminates normally.
D) It becomes ready for execution.
Answer: B
Explanation: A running process enters the waiting state when it requests an I/O operation or other event
that cannot be completed immediately.
**Question 9. The UNIX system call `fork()` creates:**
A) A new thread within the same process.
B) A duplicate of the calling process, including its address space.
C) A new process that shares the same memory pages as the parent.
D) A child process that immediately replaces its image with a new program.
Answer: B
Explanation: `fork()` creates a child process that is a copy of the parent’s address space; later `exec()` can
replace that image.
**Question 10. After a `fork()` call, which of the following is true about the return values?**
A) Both parent and child receive 0.
B) Parent receives child’s PID; child receives 0.
C) Parent receives 0; child receives parent’s PID.
D) Both receive the child’s PID.
Answer: B
, SA1 Operating Systems Lecture Ultimate Exam
Explanation: In UNIX, `fork()` returns the child’s PID to the parent and 0 to the child.
**Question cascading termination **
**Question 11. Which mechanism ensures that when a parent process terminates, all of its child
processes are also terminated?**
A) Signal handling.
B) Cascading termination.
C) Process reaping.
D) Resource inheritance.
Answer: B
Explanation: Cascading termination forces the operating system to kill all descendant processes when a
parent exits, preventing orphan processes.
**Question 12. Which IPC method provides the highest data transfer rate on a single machine?**
A) Message passing via sockets.
B) Named pipes.
C) Shared memory.
D) Signals.
Answer: C
Explanation: Shared memory allows multiple processes to access the same physical memory region,
avoiding copy overhead and thus achieving the highest throughput.
**Question 13. In the message-passing model, what is the purpose of a “mailbox”?**
A) To store messages temporarily until the receiver reads them.
B) To allocate shared memory pages.
C) To synchronize access to a critical section.
D) To translate virtual addresses.
Answer: A
Explanation: A mailbox is a kernel data structure that queues messages for a receiving process, enabling
asynchronous communication.
**Question 1. Which of the following best describes a monolithic kernel architecture?**
A) The kernel provides only minimal services and runs most services in user space.
B) All operating-system services run in kernel mode as a single large program.
C) The kernel is divided into separate modules that can be loaded and unloaded at runtime.
D) The kernel uses a microkernel for inter-process communication.
Answer: B
Explanation: In a monolithic kernel, all core services (file system, device drivers, networking, etc.)
execute in kernel mode within one large address space, unlike microkernels that keep most services in
user space.
**Question 2. What is the primary advantage of a microkernel compared to a monolithic kernel?**
A) Faster context switches.
B) Simpler device driver development.
C) Improved fault isolation because most services run in user mode.
D) Reduced memory usage due to a single address space.
Answer: C
Explanation: Microkernels keep only essential functions in kernel mode; other services run in user mode,
so a failure in a driver does not crash the entire system.
**Question 3. In a layered operating-system architecture, which layer typically interacts directly with
hardware?**
A) Application layer.
B) System-call interface layer.
C) Hardware abstraction layer.
D) User-level library layer.
Answer: C
Explanation: The hardware abstraction layer (HAL) provides a uniform interface to the underlying
hardware and is the lowest layer that directly accesses devices.
**Question 4. Which system-call interface is standard for Unix-like operating systems?**
, SA1 Operating Systems Lecture Ultimate Exam
A) Win32 API.
B) POSIX.
C) Java Native Interface.
D) DirectX.
Answer: B
Explanation: POSIX (Portable Operating System Interface) defines a set of standard system calls and
utilities for Unix-like systems.
**Question 5. What is the purpose of the “dual-mode” operation in modern operating systems?**
A) To allow two CPUs to execute the same instruction simultaneously.
B) To separate user-level code from privileged kernel code for protection.
C) To enable two different scheduling algorithms at once.
D) To provide both 32-bit and 64-bit execution modes.
Answer: B
Explanation: Dual-mode operation enforces protection by running user applications in a restricted mode
and kernel code in a privileged mode.
**Question 6. Which of the following events typically triggers a context switch?**
A) Completion of a disk read operation.
B) A timer interrupt expiring.
C) A user pressing the power button.
D) The BIOS POST routine.
Answer: B
Explanation: A timer interrupt signals the scheduler that the current process has exhausted its time
quantum, prompting a context switch.
**Question 7. In process management, the Process Control Block (PCB) does NOT contain which of the
following?**
A) Process state.
B) CPU register contents.
, SA1 Operating Systems Lecture Ultimate Exam
C) The source code of the process.
D) Memory management information.
Answer: C
Explanation: The PCB stores runtime information such as state, registers, and memory data, but not the
process’s source code.
**Question 8. Which state transition occurs when a process moves from “Running” to “Waiting”?**
A) It is preempted by the scheduler.
B) It voluntarily yields the CPU for I/O.
C) It terminates normally.
D) It becomes ready for execution.
Answer: B
Explanation: A running process enters the waiting state when it requests an I/O operation or other event
that cannot be completed immediately.
**Question 9. The UNIX system call `fork()` creates:**
A) A new thread within the same process.
B) A duplicate of the calling process, including its address space.
C) A new process that shares the same memory pages as the parent.
D) A child process that immediately replaces its image with a new program.
Answer: B
Explanation: `fork()` creates a child process that is a copy of the parent’s address space; later `exec()` can
replace that image.
**Question 10. After a `fork()` call, which of the following is true about the return values?**
A) Both parent and child receive 0.
B) Parent receives child’s PID; child receives 0.
C) Parent receives 0; child receives parent’s PID.
D) Both receive the child’s PID.
Answer: B
, SA1 Operating Systems Lecture Ultimate Exam
Explanation: In UNIX, `fork()` returns the child’s PID to the parent and 0 to the child.
**Question cascading termination **
**Question 11. Which mechanism ensures that when a parent process terminates, all of its child
processes are also terminated?**
A) Signal handling.
B) Cascading termination.
C) Process reaping.
D) Resource inheritance.
Answer: B
Explanation: Cascading termination forces the operating system to kill all descendant processes when a
parent exits, preventing orphan processes.
**Question 12. Which IPC method provides the highest data transfer rate on a single machine?**
A) Message passing via sockets.
B) Named pipes.
C) Shared memory.
D) Signals.
Answer: C
Explanation: Shared memory allows multiple processes to access the same physical memory region,
avoiding copy overhead and thus achieving the highest throughput.
**Question 13. In the message-passing model, what is the purpose of a “mailbox”?**
A) To store messages temporarily until the receiver reads them.
B) To allocate shared memory pages.
C) To synchronize access to a critical section.
D) To translate virtual addresses.
Answer: A
Explanation: A mailbox is a kernel data structure that queues messages for a receiving process, enabling
asynchronous communication.
