Operating Systems — 100 Important MCQs

Chapter 1: Introduction to Operating Systems

1. Which interface allows a user program to request services directly from the operating system?

A. Compiler
B. Device driver
C. System call
D. Linker

Correct Answer: C. System call

Explanation: A system call provides the interface through which a program requests services such as file access or process creation from the OS.

2. Which of the following is the primary purpose of an operating system?

A. Managing hardware and providing services to applications
B. Designing computer networks
C. Creating source code automatically
D. Manufacturing computer components

Correct Answer: A. Managing hardware and providing services to applications

Explanation: An OS manages CPU, memory, storage, I/O devices, and provides an execution environment for applications.

3. Which component is considered the core of an operating system?

A. Shell
B. Kernel
C. Compiler
D. File manager

Correct Answer: B. Kernel

Explanation: The kernel is the central OS component responsible for core resource and hardware management.

4. Which operating system capability allows several programs to remain in memory and make progress during execution?

A. Spooling
B. Multiprogramming
C. Formatting
D. Encryption

Correct Answer: B. Multiprogramming

Explanation: Multiprogramming keeps multiple programs in memory so the CPU can switch to another when one is waiting.

5. Which operating system is specifically designed to respond to events within strict timing constraints?

A. Batch OS
B. Distributed OS
C. Real-time OS
D. Desktop OS

Correct Answer: C. Real-time OS

Explanation: A real-time operating system is designed to provide responses within specified timing requirements.

6. Which type of operating system processes jobs in batches with little or no user interaction during execution?

A. Batch operating system
B. Real-time operating system
C. Interactive operating system
D. Distributed operating system

Correct Answer: A. Batch operating system

Explanation: Batch systems collect jobs and execute them as groups without requiring continuous user interaction.

7. Which OS component provides a command-based interface between the user and the operating system?

A. Scheduler
B. Shell
C. Kernel module
D. Memory manager

Correct Answer: B. Shell

Explanation: A shell interprets user commands and requests the corresponding operating-system operations.

8. What is the main purpose of an operating-system interrupt mechanism?

A. To increase disk capacity
B. To notify the CPU that an event requires attention
C. To permanently stop a process
D. To convert virtual addresses into physical addresses

Correct Answer: B. To notify the CPU that an event requires attention

Explanation: Interrupts allow hardware or software to signal the CPU when an event needs immediate processing.

9. Which of the following is an example of an open-source operating system?

A. Linux
B. Microsoft Windows
C. iOS
D. MS-DOS

Correct Answer: A. Linux

Explanation: Linux is an open-source operating-system kernel used by many Linux distributions.

10. Which operating-system activity is directly related to memory management?

A. Selecting a printer
B. Allocating memory to processes
C. Renaming a file
D. Changing a keyboard layout

Correct Answer: B. Allocating memory to processes

Explanation: Memory management tracks, allocates, and releases main-memory space for processes.

Chapter 2: Processes and Threads

11. Which statement best defines a process?

A. A program permanently stored on disk
B. A program in execution together with its execution state
C. A CPU instruction
D. A memory address

Correct Answer: B. A program in execution together with its execution state

Explanation: A process includes the executing program, CPU state, memory, and other resources associated with execution.

12. Which process state indicates that a process is waiting for CPU allocation?

A. New
B. Waiting
C. Ready
D. Terminated

Correct Answer: C. Ready

Explanation: A ready process has everything needed to execute but is waiting for the CPU.

13. A running process normally enters the waiting state when it:

A. Requests an I/O operation
B. Is selected by the scheduler
C. Finishes execution
D. Is placed in the ready queue

Correct Answer: A. Requests an I/O operation

Explanation: A process usually waits when it cannot continue until an I/O operation or another event completes.

14. Which data structure contains information needed by the operating system to manage a process?

A. Page table
B. Process Control Block
C. File allocation table
D. Interrupt vector

Correct Answer: B. Process Control Block

Explanation: The PCB stores information such as process state, program counter, CPU registers, and scheduling information.

15. Which information is normally stored in a Process Control Block?

A. Process state
B. Program counter
C. CPU register information
D. All of these

Correct Answer: D. All of these

Explanation: The PCB contains the execution and management information required to suspend and resume a process.

16. What happens during a context switch?

A. A file is moved to another directory
B. The CPU changes from one process or thread to another
C. Physical memory is permanently erased
D. The operating system is reinstalled

Correct Answer: B. The CPU changes from one process or thread to another

Explanation: The current execution context is saved and the saved context of another process or thread is restored.

17. A process created by another process is known as a:

A. Parent process
B. System process
C. Child process
D. Kernel process

Correct Answer: C. Child process

Explanation: The process that creates another process is the parent, while the newly created process is its child.

18. Which UNIX/Linux system call is commonly used to create a new process?

A. fork()
B. wait()
C. exit()
D. getpid()

Correct Answer: A. fork()

Explanation: The fork() system call creates a new child process by duplicating the calling process.

19. Which system call is commonly used by a parent process to wait for termination of a child?

A. exec()
B. fork()
C. wait()
D. open()

Correct Answer: C. wait()

Explanation: wait() allows the parent to wait for a child process to terminate and obtain its termination status.

20. Which statement about threads within the same process is generally correct?

A. They have completely separate address spaces
B. They share the process address space
C. They cannot execute concurrently
D. They must use different operating systems

Correct Answer: B. They share the process address space

Explanation: Threads of a process normally share code, data, and other process resources but have separate stacks and execution states.

21. Which resource is normally private to each thread?

A. Process address space
B. Code section
C. Thread stack
D. Shared data

Correct Answer: C. Thread stack

Explanation: Each thread normally maintains its own stack for function calls, local variables, and execution information.

22. A zombie process is a process that:

A. Is using all available CPU time
B. Has terminated but still has an entry in the process table
C. Has never started execution
D. Is permanently blocked on I/O

Correct Answer: B. Has terminated but still has an entry in the process table

Explanation: A terminated child can remain as a zombie until its parent collects its termination status.

23. Which process state normally represents a process that has completed execution?

A. Ready
B. Running
C. Waiting
D. Terminated

Correct Answer: D. Terminated

Explanation: A process enters the terminated state after it finishes execution or is explicitly terminated.

24. What is the main advantage of multithreading?

A. It eliminates the need for memory
B. It can improve responsiveness and allow concurrent execution within a process
C. It removes all synchronization requirements
D. It prevents context switching

Correct Answer: B. It can improve responsiveness and allow concurrent execution within a process

Explanation: Multiple threads can perform different activities concurrently while sharing process resources.

Chapter 3: CPU Scheduling

25. Which scheduling algorithm executes processes according to their arrival order?

A. FCFS
B. SJF
C. Priority
D. Round Robin

Correct Answer: A. FCFS

Explanation: First-Come, First-Served assigns the CPU according to the order in which processes enter the ready queue.

26. Which scheduling algorithm selects the process with the shortest estimated CPU burst?

A. Round Robin
B. SJF
C. FCFS
D. Priority

Correct Answer: B. SJF

Explanation: Shortest Job First selects the process with the smallest expected CPU burst.

27. Which scheduling algorithm uses a time quantum?

A. FCFS
B. SJF
C. Round Robin
D. Non-preemptive Priority

Correct Answer: C. Round Robin

Explanation: Round Robin gives each ready process a fixed time quantum before moving to the next process.

28. If the Round Robin time quantum becomes extremely large, the algorithm approaches:

A. SJF
B. Priority scheduling
C. FCFS
D. Multilevel feedback queue

Correct Answer: C. FCFS

Explanation: With a very large quantum, each process can usually finish before the CPU moves to another process, producing FCFS-like behavior.

29. Which scheduling algorithm is particularly susceptible to starvation of low-priority processes?

A. Priority scheduling
B. FCFS
C. Round Robin
D. FIFO

Correct Answer: A. Priority scheduling

Explanation: A continuously arriving stream of high-priority processes can indefinitely delay low-priority processes.

30. Which technique can reduce starvation in priority scheduling?

A. Paging
B. Aging
C. Spooling
D. Compaction

Correct Answer: B. Aging

Explanation: Aging gradually increases the priority of a process that has waited for a long time.

31. Turnaround time is the time between:

A. Process arrival and process completion
B. First CPU allocation and completion
C. Process creation and first CPU allocation
D. CPU allocation and I/O completion

Correct Answer: A. Process arrival and process completion

Explanation: Turnaround time represents the total elapsed time from submission or arrival until completion.

32. Waiting time for a process primarily represents the time spent:

A. Performing I/O
B. Executing on the CPU
C. In the ready queue waiting for CPU
D. After process termination

Correct Answer: C. In the ready queue waiting for CPU

Explanation: CPU scheduling waiting time measures how long a process waits in the ready queue.

33. Which scheduling approach can interrupt a currently running process?

A. Non-preemptive scheduling
B. Preemptive scheduling
C. Batch scheduling only
D. FIFO file scheduling

Correct Answer: B. Preemptive scheduling

Explanation: In preemptive scheduling, the OS can take the CPU away from a running process.

34. Which scheduling algorithm generally provides good response time for interactive systems?

A. FCFS
B. Round Robin
C. Non-preemptive SJF
D. Static FIFO

Correct Answer: B. Round Robin

Explanation: Round Robin regularly gives CPU time to each ready process, making it suitable for interactive workloads.

35. What is the main objective of load balancing in multiprocessor systems?

A. Distribute work among processors
B. Increase disk capacity
C. Reduce page size
D. Increase file permissions

Correct Answer: A. Distribute work among processors

Explanation: Load balancing attempts to prevent some processors from being overloaded while others remain idle.

Chapter 4: Synchronization and Interprocess Communication

36. A race condition occurs when:

A. A process uses too much disk space
B. The result depends on the timing of concurrent operations
C. A process enters the terminated state
D. A CPU has multiple cores

Correct Answer: B. The result depends on the timing of concurrent operations

Explanation: Concurrent processes or threads accessing shared data can produce different results depending on execution timing.

37. The part of a program where shared data is accessed is called the:

A. Critical section
B. Ready queue
C. Page table
D. Stack frame

Correct Answer: A. Critical section

Explanation: A critical section is code that accesses shared resources and therefore requires appropriate synchronization.

38. Which synchronization mechanism is commonly used to control access to a critical section?

A. Semaphore
B. Page table
C. File descriptor
D. Disk scheduler

Correct Answer: A. Semaphore

Explanation: A semaphore provides synchronization and can control how processes or threads access shared resources.

39. A mutex is primarily used to provide:

A. Virtual memory
B. Mutual exclusion
C. File allocation
D. CPU scheduling

Correct Answer: B. Mutual exclusion

Explanation: A mutex ensures that only one thread at a time can enter a protected critical section.

40. Which synchronization construct combines shared data with procedures that operate on that data?

A. Pipe
B. Monitor
C. File descriptor
D. Page table

Correct Answer: B. Monitor

Explanation: A monitor encapsulates shared data and synchronization operations in a structured mechanism.

41. Which IPC mechanism allows two processes to communicate through a kernel-managed data channel?

A. Pipe
B. Cache
C. Register
D. Page table

Correct Answer: A. Pipe

Explanation: A pipe provides a communication channel through which processes can send and receive data.

42. Why can shared-memory IPC be faster than message passing?

A. It always eliminates synchronization
B. Processes can directly access a shared memory region
C. It does not use RAM
D. It requires no operating system

Correct Answer: B. Processes can directly access a shared memory region

Explanation: Shared memory can reduce data copying through the kernel, although synchronization is still necessary.

43. Which IPC model communicates by sending messages rather than directly sharing a memory region?

A. Message passing
B. Paging
C. Segmentation
D. Spooling

Correct Answer: A. Message passing

Explanation: Message passing allows processes to communicate by explicitly sending and receiving messages.

44. What is the primary purpose of synchronization in concurrent systems?

A. To increase hard-disk capacity
B. To coordinate access to shared resources
C. To eliminate all processes
D. To replace the CPU scheduler

Correct Answer: B. To coordinate access to shared resources

Explanation: Synchronization prevents incorrect results caused by uncontrolled concurrent access to shared resources.

Chapter 5: Deadlocks

45. Which of the following is one of the four necessary conditions for deadlock?

A. Mutual exclusion
B. CPU overheating
C. High memory capacity
D. File compression

Correct Answer: A. Mutual exclusion

Explanation: Mutual exclusion is one of the four Coffman conditions required for deadlock.

46. Which condition means a process holds at least one resource while waiting for another?

A. Circular wait
B. Hold and wait
C. No preemption
D. Mutual exclusion

Correct Answer: B. Hold and wait

Explanation: In hold and wait, a process retains allocated resources while requesting additional resources.

47. Which of the following is NOT a Coffman deadlock condition?

A. Circular wait
B. Hold and wait
C. Mutual exclusion
D. Resource utilization

Correct Answer: D. Resource utilization

Explanation: The four conditions are mutual exclusion, hold and wait, no preemption, and circular wait.

48. Which algorithm is primarily associated with deadlock avoidance?

A. Banker’s Algorithm
B. FCFS
C. FIFO
D. Round Robin

Correct Answer: A. Banker’s Algorithm

Explanation: The Banker’s Algorithm checks whether granting resources keeps the system in a safe state.

49. A system is considered to be in a safe state if:

A. All processes are terminated
B. All resources are currently unused
C. There exists a sequence in which all processes can finish
D. No process is waiting

Correct Answer: C. There exists a sequence in which all processes can finish

Explanation: A safe state has at least one safe sequence that allows every process to obtain needed resources and complete.

50. In a resource-allocation graph, a process is usually represented by a:

A. Rectangle
B. Circle
C. Triangle
D. Line

Correct Answer: B. Circle

Explanation: Processes are represented by circles, while resource types are generally represented by rectangles.

51. Deadlock prevention attempts to:

A. Eliminate at least one necessary deadlock condition
B. Increase CPU clock speed
C. Increase the number of files
D. Remove virtual memory

Correct Answer: A. Eliminate at least one necessary deadlock condition

Explanation: Deadlock prevention guarantees that at least one Coffman condition cannot hold.

52. Which approach detects a deadlock after it has occurred?

A. Deadlock detection
B. Deadlock prevention
C. Aging
D. Paging

Correct Answer: A. Deadlock detection

Explanation: Detection algorithms examine the system to determine whether processes and resources are already deadlocked.

Chapter 6: Memory Management

53. Which memory is generally faster and closer to the CPU than main memory?

A. Magnetic disk
B. Optical disk
C. Cache memory
D. USB storage

Correct Answer: C. Cache memory

Explanation: Cache provides faster access to frequently needed data and instructions than main memory.

54. Which technique divides logical memory into fixed-size pages?

A. Segmentation
B. Paging
C. Compaction
D. Swapping

Correct Answer: B. Paging

Explanation: Paging divides logical memory into fixed-size pages and physical memory into fixed-size frames.

55. Physical memory is divided into fixed-size units called:

A. Segments
B. Pages
C. Frames
D. Blocks

Correct Answer: C. Frames

Explanation: In a paging system, physical memory is divided into frames that hold pages.

56. A logical address in a paging system is generally divided into:

A. Page number and offset
B. Segment and cylinder
C. Frame number and sector
D. Block number and track

Correct Answer: A. Page number and offset

Explanation: The page number identifies the page, while the offset identifies a location within that page.

57. A page fault occurs when:

A. A page is larger than a frame
B. The required page is not currently in physical memory
C. The page table contains no entries
D. The CPU has no registers

Correct Answer: B. The required page is not currently in physical memory

Explanation: The OS must bring the required page from secondary storage into physical memory after a page fault.

58. Which page replacement algorithm replaces the page that has not been used for the longest time?

A. FIFO
B. Optimal
C. LRU
D. Random

Correct Answer: C. LRU

Explanation: LRU replaces the page whose most recent reference occurred farthest in the past.

59. Which page replacement algorithm removes the page that has been in memory the longest?

A. FIFO
B. LRU
C. Optimal
D. LFU

Correct Answer: A. FIFO

Explanation: FIFO replaces the page that entered memory first.

60. The Optimal page replacement algorithm replaces the page:

A. Used most recently
B. Loaded first
C. Whose next use is farthest in the future
D. Used most frequently

Correct Answer: C. Whose next use is farthest in the future

Explanation: Optimal replacement selects the page that will not be needed for the longest future period.

61. Which page replacement algorithm is mainly theoretical because it requires knowledge of future references?

A. FIFO
B. Optimal
C. LRU
D. Clock

Correct Answer: B. Optimal

Explanation: The exact future memory-reference sequence is normally unknown, so Optimal is mainly used as a benchmark.

62. Excessive paging activity that leaves little time for actual process execution is called:

A. Compaction
B. Thrashing
C. Segmentation
D. Fragmentation

Correct Answer: B. Thrashing

Explanation: Thrashing occurs when excessive page faults cause the system to spend most of its time moving pages between memory and storage.

63. Segmentation divides a program according to:

A. Fixed-size physical frames
B. Logical program units
C. Disk sectors
D. CPU clock cycles

Correct Answer: B. Logical program units

Explanation: Segmentation represents logical units such as code, data, and stack as separate variable-sized segments.

64. Which memory-management technique commonly eliminates external fragmentation?

A. Paging
B. Segmentation
C. Variable partitioning
D. Contiguous allocation

Correct Answer: A. Paging

Explanation: Fixed-size frames allow pages to be placed in non-contiguous locations, avoiding external fragmentation.

65. Internal fragmentation refers to:

A. Unused space inside an allocated memory block
B. Free memory scattered outside allocated blocks
C. A missing page in memory
D. A disk scheduling problem

Correct Answer: A. Unused space inside an allocated memory block

Explanation: Internal fragmentation occurs when the allocated unit is larger than the requested space.

Chapter 7: File Systems

66. Which file access method processes records in a predefined order?

A. Direct access
B. Sequential access
C. Indexed access
D. Hashed access

Correct Answer: B. Sequential access

Explanation: Sequential access reads file data in order from one record or block to the next.

67. Which directory structure allows directories to contain subdirectories?

A. Single-level directory
B. Two-level directory
C. Tree-structured directory
D. Flat directory

Correct Answer: C. Tree-structured directory

Explanation: A tree structure organizes files and directories hierarchically.

68. Which file allocation method stores the blocks of a file consecutively?

A. Linked allocation
B. Indexed allocation
C. Contiguous allocation
D. Hashed allocation

Correct Answer: C. Contiguous allocation

Explanation: Contiguous allocation stores a file in consecutive disk blocks.

69. A major disadvantage of contiguous file allocation is:

A. External fragmentation
B. No sequential access
C. No direct access
D. Inability to read files

Correct Answer: A. External fragmentation

Explanation: Free disk space can become fragmented, making it difficult to allocate large contiguous areas.

70. Which file allocation method uses an index block containing pointers to the file’s data blocks?

A. Contiguous allocation
B. Indexed allocation
C. Sequential allocation
D. Stack allocation

Correct Answer: B. Indexed allocation

Explanation: Indexed allocation stores addresses of the file’s data blocks in a separate index block.

71. Which allocation method links each file block to the next block?

A. Contiguous allocation
B. Indexed allocation
C. Linked allocation
D. Static allocation

Correct Answer: C. Linked allocation

Explanation: In linked allocation, each disk block contains a pointer to the next block belonging to the file.

72. Which directory structure gives each user a separate directory while maintaining a common master directory?

A. Single-level
B. Two-level
C. Tree-structured
D. Graph-structured

Correct Answer: B. Two-level

Explanation: A two-level directory structure provides a separate user file directory under a master directory.

73. Which file operation is used to retrieve data from an existing file?

A. Read
B. Create
C. Rename
D. Delete

Correct Answer: A. Read

Explanation: The read operation transfers file data from storage into memory for use by a process.

Chapter 8: I/O Systems and Disk Scheduling

74. Which software component allows an operating system to communicate with a specific hardware device?

A. Compiler
B. Device driver
C. Linker
D. Loader

Correct Answer: B. Device driver

Explanation: A device driver provides the OS with the instructions needed to control a particular hardware device.

75. What is the primary purpose of buffering?

A. To match differences between data-transfer speeds
B. To increase CPU frequency
C. To replace the kernel
D. To prevent file creation

Correct Answer: A. To match differences between data-transfer speeds

Explanation: Buffers temporarily store data when the producer and consumer operate at different speeds.

76. Which I/O technique allows a device to notify the CPU when service is required?

A. Polling
B. Interrupt-driven I/O
C. Spooling
D. Caching

Correct Answer: B. Interrupt-driven I/O

Explanation: The device generates an interrupt to notify the CPU that an I/O event requires attention.

77. In programmed I/O, the CPU typically:

A. Continuously checks the device status
B. Never communicates with the device
C. Transfers data only through cache
D. Uses another CPU for every transfer

Correct Answer: A. Continuously checks the device status

Explanation: In programmed I/O, the CPU actively polls or checks the device and manages the transfer.

78. DMA is primarily used to:

A. Schedule processes
B. Transfer data between I/O devices and memory with limited CPU involvement
C. Translate virtual addresses
D. Create user accounts

Correct Answer: B. Transfer data between I/O devices and memory with limited CPU involvement

Explanation: Direct Memory Access allows hardware to transfer blocks of data directly between a device and main memory.

79. Which disk scheduling algorithm serves requests in their arrival order?

A. SSTF
B. SCAN
C. FCFS
D. C-SCAN

Correct Answer: C. FCFS

Explanation: FCFS services disk requests in the order they are received.

80. SSTF selects the disk request with the:

A. Highest priority
B. Shortest seek distance from the current head position
C. Longest waiting time
D. Largest file size

Correct Answer: B. Shortest seek distance from the current head position

Explanation: Shortest Seek Time First chooses the pending request closest to the current disk-head position.

81. SCAN disk scheduling is commonly called the:

A. Elevator algorithm
B. Banker algorithm
C. Clock algorithm
D. Aging algorithm

Correct Answer: A. Elevator algorithm

Explanation: SCAN moves the disk head in one direction while servicing requests and then reverses direction.

82. C-SCAN differs from SCAN because C-SCAN:

A. Services requests in both directions
B. Services requests in one direction and then returns to the beginning
C. Always selects the closest request
D. Uses process priorities

Correct Answer: B. Services requests in one direction and then returns to the beginning

Explanation: Circular SCAN services requests in one direction and returns to the starting end without servicing requests on the return movement.

83. Which factor directly affects disk scheduling performance?

A. Seek time
B. Source-code length
C. Monitor resolution
D. Keyboard layout

Correct Answer: A. Seek time

Explanation: Seek time is the time required for the disk head to move to the required track.

Chapter 9: Protection and Security

84. Authentication primarily answers which question?

A. What is the user allowed to do?
B. Who is the user?
C. Which process should run first?
D. Where is the file stored?

Correct Answer: B. Who is the user?

Explanation: Authentication verifies the identity of a user or system entity.

85. Authorization primarily determines:

A. The identity of a user
B. Which resources and operations a user is permitted to access
C. Whether data is encrypted
D. Whether the CPU is available

Correct Answer: B. Which resources and operations a user is permitted to access

Explanation: Authorization defines the permissions granted to an authenticated user or process.

86. Encryption transforms:

A. Ciphertext into plaintext
B. Plaintext into ciphertext
C. Files into processes
D. Passwords into usernames

Correct Answer: B. Plaintext into ciphertext

Explanation: Encryption converts readable data into protected ciphertext using an encryption algorithm and key.

87. Which security principle gives users only the permissions necessary to perform their tasks?

A. Least privilege
B. Round Robin
C. First-come first-served
D. Memory compaction

Correct Answer: A. Least privilege

Explanation: Least privilege limits users and processes to only the permissions they actually require.

88. Which operating-system mechanism can restrict one process from directly accessing another process’s memory?

A. Memory protection
B. Disk scheduling
C. Spooling
D. File compression

Correct Answer: A. Memory protection

Explanation: Hardware-supported memory protection prevents processes from accessing unauthorized memory regions.

89. Which type of attack attempts to make a service unavailable by overwhelming it with traffic or requests?

A. Denial-of-Service attack
B. File allocation
C. Paging
D. Context switching

Correct Answer: A. Denial-of-Service attack

Explanation: A DoS attack attempts to consume system or network resources so legitimate users cannot access the service normally.

90. Why are operating-system access permissions important?

A. They control which users or processes can access protected resources
B. They increase CPU clock speed
C. They reduce screen resolution
D. They replace system calls

Correct Answer: A. They control which users or processes can access protected resources

Explanation: Access permissions help protect files, memory, devices, and other system resources from unauthorized use.

Chapter 10: Advanced Operating-System Concepts

91. Which scheduler selects processes from the ready queue and assigns the CPU?

A. Long-term scheduler
B. Short-term scheduler
C. Medium-term scheduler
D. Job scheduler only

Correct Answer: B. Short-term scheduler

Explanation: The short-term scheduler frequently selects a ready process to execute on the CPU.

92. Which scheduler controls the degree of multiprogramming by deciding which jobs enter the system?

A. Long-term scheduler
B. Short-term scheduler
C. I/O scheduler
D. Device scheduler

Correct Answer: A. Long-term scheduler

Explanation: The long-term scheduler determines which new processes are admitted into the system.

93. Which scheduler is associated with temporarily removing processes from memory and later bringing them back?

A. Long-term scheduler
B. Short-term scheduler
C. Medium-term scheduler
D. File scheduler

Correct Answer: C. Medium-term scheduler

Explanation: The medium-term scheduler can suspend and swap processes to control memory usage and multiprogramming.

94. Which scheduler normally executes most frequently?

A. Long-term scheduler
B. Medium-term scheduler
C. Short-term scheduler
D. Batch scheduler

Correct Answer: C. Short-term scheduler

Explanation: The short-term scheduler may execute whenever the CPU needs to select another ready process.

95. What is the main purpose of swapping?

A. To move processes between main memory and secondary storage
B. To increase CPU clock speed
C. To encrypt files
D. To change process priorities permanently

Correct Answer: A. To move processes between main memory and secondary storage

Explanation: Swapping temporarily moves processes between RAM and secondary storage to manage memory availability.

96. What is the main purpose of a virtual machine?

A. To provide an isolated software-based computing environment
B. To physically increase RAM
C. To replace all operating systems
D. To increase monitor resolution

Correct Answer: A. To provide an isolated software-based computing environment

Explanation: Virtualization allows a software environment to emulate or abstract computer hardware so multiple OS instances can run on one physical machine.

97. Which kernel design keeps many operating-system services inside the kernel space?

A. Microkernel
B. Monolithic kernel
C. Exokernel only
D. User-level kernel

Correct Answer: B. Monolithic kernel

Explanation: A monolithic kernel places many core OS services, such as memory and device management, within kernel space.

98. Which kernel design attempts to keep only essential services in kernel space and move other services to user space?

A. Monolithic kernel
B. Hybrid kernel
C. Microkernel
D. Batch kernel

Correct Answer: C. Microkernel

Explanation: A microkernel minimizes kernel-space functionality and moves many services into user-space processes.

99. What does network transparency in a distributed operating system attempt to provide?

A. It makes network failures impossible
B. It makes remote resources appear similar to local resources
C. It removes the need for networking
D. It forces every computer to use identical hardware

Correct Answer: B. It makes remote resources appear similar to local resources

Explanation: Network transparency hides many details of remote resource location and communication from users and applications.

100. Which statement best describes the relationship between an operating system and application programs?

A. Applications directly control all hardware without OS involvement
B. The OS provides controlled services and resource access to applications
C. Applications replace the kernel during execution
D. The OS is used only to store application files

Correct Answer: B. The OS provides controlled services and resource access to applications

Explanation: The operating system provides applications with controlled access to CPU, memory, files, devices, and other system resources.