EduConceptHub

Start MCQs

Operating Systems

Operating Systems

Introduction

Study how operating systems manage processes, threads, memory, storage and access to computer resources.

Topic-Wise Overview

Operating System Basics

System calls, OS structures and processes

Scheduling and Concurrency

Process and thread scheduling, inter-process communication and synchronization

Deadlocks

Deadlock prevention, detection and recovery

Memory Management

Paging, segmentation, virtual memory and thrashing

Storage and Protection

File systems, disk scheduling, security and virtual machines

Study Guidance

Explore the complete collection of 200 Operating Systems MCQs with four answer options and a clear explanation for every question. The questions below are organized into five numbered sets covering processes, CPU scheduling, synchronization, deadlocks, memory, storage, I/O, protection and virtualization. Additional short questions and worked solutions will be developed progressively.

Explore Other Subjects

Browse Computer Science subjects

Operating Systems MCQs: Set 1 (Questions 1–30)

Explore OS foundations, processes, scheduling, synchronization, deadlocks and memory management. Select an answer and open the explanation.

Question 1. What is a primary function of an operating system?

  1. To manage hardware resources and provide services to programs
  2. To replace the CPU’s instruction set
  3. To compile every application automatically
  4. To provide only internet connectivity
Show correct answer and explanation

Correct answer: A. To manage hardware resources and provide services to programs

An OS coordinates hardware resources and offers abstractions and services to applications.

Question 2. Which component is the core of an operating system?

  1. Web browser
  2. Kernel
  3. Text editor
  4. Spreadsheet
Show correct answer and explanation

Correct answer: B. Kernel

The kernel manages essential system resources and mediates access to hardware.

Question 3. A system call provides:

  1. A new physical processor
  2. A keyboard shortcut
  3. An interface for a program to request OS services
  4. A substitute for all device drivers
Show correct answer and explanation

Correct answer: C. An interface for a program to request OS services

System calls let user programs request protected operating-system operations.

Question 4. Which execution mode normally has privileged access to hardware?

  1. Browser mode
  2. Guest application mode
  3. User mode
  4. Kernel mode
Show correct answer and explanation

Correct answer: D. Kernel mode

Kernel mode permits privileged instructions needed for operating-system functions.

Question 5. A process is best described as:

  1. A program in execution with its associated state and resources
  2. Only a source-code file
  3. A physical memory chip
  4. A directory on disk
Show correct answer and explanation

Correct answer: A. A program in execution with its associated state and resources

A process represents an executing program and includes execution context and resources.

Question 6. Which process state means waiting for a particular event or I/O completion?

  1. Running
  2. Blocked or waiting
  3. Ready
  4. Terminated
Show correct answer and explanation

Correct answer: B. Blocked or waiting

A waiting process cannot proceed until an expected event occurs.

Question 7. Which data structure typically stores a process’s scheduling and state information?

  1. File allocation table
  2. Translation lookaside buffer
  3. Process control block
  4. Disk partition table
Show correct answer and explanation

Correct answer: C. Process control block

A PCB holds process identifiers, state and context information used by the OS.

Question 8. A context switch generally involves:

  1. Increasing disk capacity
  2. Compiling user code
  3. Erasing process memory
  4. Saving one execution context and restoring another
Show correct answer and explanation

Correct answer: D. Saving one execution context and restoring another

The OS saves relevant processor state and restores another process or thread’s context.

Question 9. Threads within the same process usually share:

  1. The process address space
  2. Distinct physical computers
  3. Separate executable files by definition
  4. All CPU registers at every instant
Show correct answer and explanation

Correct answer: A. The process address space

Threads in one process typically share memory and other process resources while having individual execution contexts.

Question 10. What is the purpose of CPU scheduling?

  1. To format hard drives
  2. To select which ready task runs on a processor
  3. To disable interrupts permanently
  4. To translate every file name
Show correct answer and explanation

Correct answer: B. To select which ready task runs on a processor

The scheduler allocates CPU time among runnable tasks.

Question 11. In first-come, first-served scheduling, jobs are served according to:

  1. Shortest predicted burst first
  2. Highest memory address
  3. Arrival order
  4. Largest process identifier
Show correct answer and explanation

Correct answer: C. Arrival order

FCFS normally runs ready jobs in the order they enter the scheduling queue.

Question 12. Round-robin scheduling is characterized by:

  1. No time sharing
  2. Always choosing the longest job
  3. Disabling preemption
  4. A fixed time quantum for each turn
Show correct answer and explanation

Correct answer: D. A fixed time quantum for each turn

Round robin cycles through runnable tasks with bounded time slices.

Question 13. A time quantum that is extremely small can cause:

  1. Excessive context-switch overhead
  2. Zero context switches
  3. Guaranteed maximum throughput
  4. Elimination of waiting time
Show correct answer and explanation

Correct answer: A. Excessive context-switch overhead

Very frequent preemption can spend significant time switching contexts.

Question 14. Shortest-job-first scheduling prioritizes:

  1. Tasks with the largest memory footprint
  2. The process with the shortest estimated CPU burst
  3. Tasks in reverse arrival order
  4. Only I/O-bound processes
Show correct answer and explanation

Correct answer: B. The process with the shortest estimated CPU burst

SJF chooses the smallest next CPU burst, assuming estimates are available.

Question 15. What is starvation in process scheduling?

  1. A disk having no free space
  2. A CPU overheating
  3. A task waiting indefinitely because it is repeatedly denied resources or CPU time
  4. A process completing early
Show correct answer and explanation

Correct answer: C. A task waiting indefinitely because it is repeatedly denied resources or CPU time

Starvation occurs when scheduling or resource allocation can postpone a task without bound.

Question 16. Aging in priority scheduling helps:

  1. Increase every process’s memory size
  2. Reduce file fragmentation
  3. Stop all interrupts
  4. Reduce starvation by raising the priority of long-waiting tasks
Show correct answer and explanation

Correct answer: D. Reduce starvation by raising the priority of long-waiting tasks

Aging adjusts priorities over time so long-waiting tasks can eventually run.

Question 17. A race condition occurs when:

  1. An outcome depends on the timing or interleaving of concurrent operations
  2. Two files have the same extension
  3. The computer has multiple cores
  4. All processes run serially
Show correct answer and explanation

Correct answer: A. An outcome depends on the timing or interleaving of concurrent operations

Unsynchronized concurrent access can make results depend on operation order.

Question 18. A critical section is code that:

  1. Cannot contain a function call
  2. Accesses shared state requiring controlled concurrent access
  3. Must run in user mode only
  4. Always performs disk I/O
Show correct answer and explanation

Correct answer: B. Accesses shared state requiring controlled concurrent access

Critical sections protect operations on shared resources from unsafe interleavings.

Question 19. The mutual exclusion requirement means:

  1. Every thread enters simultaneously
  2. Only one process can exist
  3. At most one participant is in a protected critical section at a time
  4. Only one CPU may be installed
Show correct answer and explanation

Correct answer: C. At most one participant is in a protected critical section at a time

Mutual exclusion prevents concurrent entry into a shared critical section.

Question 20. Which synchronization primitive has atomic wait and signal operations?

  1. Page table
  2. Cache line
  3. File descriptor
  4. Semaphore
Show correct answer and explanation

Correct answer: D. Semaphore

A semaphore supports atomic decrement/wait and increment/signal semantics.

Question 21. A binary semaphore can be used to:

  1. Control access to a shared resource with two logical states
  2. Encode an entire filesystem
  3. Schedule disks only
  4. Measure CPU temperature
Show correct answer and explanation

Correct answer: A. Control access to a shared resource with two logical states

A binary semaphore has a value effectively restricted to zero or one and can coordinate exclusive access.

Question 22. A mutex is primarily intended to:

  1. Compress memory
  2. Provide mutually exclusive access to a critical section
  3. Allocate disk sectors
  4. Start a bootloader
Show correct answer and explanation

Correct answer: B. Provide mutually exclusive access to a critical section

A mutex coordinates access so only its owner holds the protected lock at a time.

Question 23. Which is one necessary condition for a classical resource deadlock?

  1. Preemption of every resource
  2. Unlimited resources
  3. Circular wait
  4. Immediate task termination
Show correct answer and explanation

Correct answer: C. Circular wait

Circular wait is one of the four Coffman necessary conditions for deadlock.

Question 24. Which choice lists all four Coffman deadlock conditions?

  1. Mutual exclusion, paging, caching, preemption
  2. Circular wait, interrupts, scheduling, segmentation
  3. Hold and wait, aging, swapping, paging
  4. Mutual exclusion, hold and wait, no preemption, circular wait
Show correct answer and explanation

Correct answer: D. Mutual exclusion, hold and wait, no preemption, circular wait

A deadlock requires all four conditions to hold in the classical model.

Question 25. Banker’s algorithm is associated with:

  1. Deadlock avoidance
  2. Directory indexing
  3. Page compression
  4. Network routing
Show correct answer and explanation

Correct answer: A. Deadlock avoidance

Banker’s algorithm checks whether allocations preserve a safe resource-allocation state.

Question 26. A safe state in deadlock avoidance means:

  1. No process is currently running
  2. There exists an order in which all processes can finish using available and releasable resources
  3. Every resource is permanently allocated
  4. No thread uses a lock
Show correct answer and explanation

Correct answer: B. There exists an order in which all processes can finish using available and releasable resources

Safety requires an available completion sequence even if all processes request their remaining declared needs.

Question 27. What is virtual memory?

  1. Only the installed physical RAM
  2. A faster mechanical disk
  3. An address-space abstraction that can be backed by RAM and secondary storage
  4. A CPU instruction cache
Show correct answer and explanation

Correct answer: C. An address-space abstraction that can be backed by RAM and secondary storage

Virtual memory separates logical address spaces from available physical memory and may use disk backing.

Question 28. Paging divides a virtual address space into:

  1. Directories
  2. Variable-length processes
  3. Only contiguous files
  4. Fixed-size pages
Show correct answer and explanation

Correct answer: D. Fixed-size pages

Paging maps fixed-size virtual pages to physical memory frames.

Question 29. A page fault occurs when:

  1. A referenced virtual page is not currently mapped as accessible in the required way
  2. A CPU uses any register
  3. A file name is too long
  4. A process finishes normally
Show correct answer and explanation

Correct answer: A. A referenced virtual page is not currently mapped as accessible in the required way

The processor traps to the OS when a page access cannot be satisfied by the current mapping; the OS may load the page or raise an error.

Question 30. What is the role of a translation lookaside buffer (TLB)?

  1. Permanently storing user files
  2. Caching recent virtual-to-physical address translations
  3. Selecting the next disk request
  4. Tracking semaphore values
Show correct answer and explanation

Correct answer: B. Caching recent virtual-to-physical address translations

A TLB accelerates address translation by caching translation entries.

Operating Systems MCQs: Set 2 (Questions 31–65)

Choose an answer and reveal the correct option with its explanation.

Question 31. Demand paging loads a page?

  1. Only at boot
  2. Only at process exit
  3. When it is needed
  4. After every instruction
Show correct answer and explanation

Correct answer: C. When it is needed

It brings required pages into memory on demand.

Question 32. A page frame is?

  1. A process state
  2. A file extension
  3. A CPU register
  4. A fixed-size physical memory block
Show correct answer and explanation

Correct answer: D. A fixed-size physical memory block

Frames hold virtual pages in physical memory.

Question 33. Internal fragmentation is?

  1. Unused space within allocated units
  2. Free gaps between allocations
  3. A missing file
  4. A deadlock
Show correct answer and explanation

Correct answer: A. Unused space within allocated units

Fixed-size allocations may contain unused portions.

Question 34. External fragmentation is?

  1. Unused space inside one page
  2. Scattered free-space gaps
  3. A page hit
  4. A context switch
Show correct answer and explanation

Correct answer: B. Scattered free-space gaps

Variable-sized allocations may leave separated holes.

Question 35. A page table primarily maps?

  1. Files to directories
  2. Threads to CPUs
  3. Virtual pages to physical frames
  4. Ports to processes
Show correct answer and explanation

Correct answer: C. Virtual pages to physical frames

Page tables contain address translation information.

Question 36. LRU evicts the page?

  1. Loaded first regardless of use
  2. Used most recently
  3. Having largest size
  4. Not used for the longest time
Show correct answer and explanation

Correct answer: D. Not used for the longest time

LRU uses recency of access.

Question 37. FIFO page replacement evicts the page?

  1. Resident for the longest time
  2. Used least recently
  3. Used most frequently
  4. Having smallest size
Show correct answer and explanation

Correct answer: A. Resident for the longest time

FIFO follows order of arrival into memory.

Question 38. Belady’s anomaly can occur under?

  1. Optimal replacement
  2. FIFO replacement
  3. LRU replacement
  4. Stack algorithms generally
Show correct answer and explanation

Correct answer: B. FIFO replacement

FIFO can incur more faults with additional frames.

Question 39. Optimal page replacement evicts?

  1. The smallest page
  2. The most recent page
  3. The page whose next use is farthest away
  4. The earliest disk sector
Show correct answer and explanation

Correct answer: C. The page whose next use is farthest away

OPT assumes knowledge of future references.

Question 40. Thrashing means?

  1. Normal CPU scheduling
  2. Fast disk formatting
  3. Normal boot
  4. Excessive paging that limits useful progress
Show correct answer and explanation

Correct answer: D. Excessive paging that limits useful progress

Heavy paging can overwhelm useful execution.

Question 41. A working set approximates?

  1. Recently active pages
  2. All possible virtual addresses
  3. Only kernel files
  4. Every open socket
Show correct answer and explanation

Correct answer: A. Recently active pages

It estimates memory locality over a reference window.

Question 42. Temporal locality means?

  1. Nearby addresses are always unused
  2. Recently accessed data may be reused soon
  3. All disk reads are random
  4. All processes have equal priority
Show correct answer and explanation

Correct answer: B. Recently accessed data may be reused soon

Temporal locality is reuse over time.

Question 43. Spatial locality means?

  1. Only the same address is reused
  2. Every page is on disk
  3. Nearby addresses may be accessed soon
  4. Memory must be contiguous
Show correct answer and explanation

Correct answer: C. Nearby addresses may be accessed soon

Spatial locality is proximity in address space.

Question 44. Segmentation uses?

  1. Only fixed-size physical frames
  2. Only cache lines
  3. Only CPU registers
  4. Variable-size logical memory regions
Show correct answer and explanation

Correct answer: D. Variable-size logical memory regions

Segments can correspond to code, data, or stacks.

Question 45. Copy-on-write delays copying until?

  1. A shared page is modified
  2. A process merely reads
  3. The OS boots
  4. Every timer interrupt
Show correct answer and explanation

Correct answer: A. A shared page is modified

A private copy is made on a modifying access.

Question 46. A memory-mapped file permits?

  1. Converting files to processes
  2. Accessing file data via virtual addresses
  3. Disabling virtual memory
  4. Replacing the kernel
Show correct answer and explanation

Correct answer: B. Accessing file data via virtual addresses

Mapped files appear in a process address space.

Question 47. An inode typically stores?

  1. Only a directory name
  2. An active CPU register
  3. Filesystem object metadata and block references
  4. The scheduler queue
Show correct answer and explanation

Correct answer: C. Filesystem object metadata and block references

Unix-like inodes identify files and retain metadata.

Question 48. A directory is used to?

  1. Allocate CPU time
  2. Replace page tables
  3. Count page faults
  4. Associate names with filesystem objects
Show correct answer and explanation

Correct answer: D. Associate names with filesystem objects

Directories support file-name lookup.

Question 49. A hard link creates?

  1. Another name for the same inode
  2. A full duplicate independent file
  3. A network connection
  4. A copied bootloader
Show correct answer and explanation

Correct answer: A. Another name for the same inode

Hard links share an inode in supported filesystems.

Question 50. A symbolic link generally holds?

  1. A duplicate file payload
  2. A target pathname
  3. A new CPU process
  4. A hardwired disk address
Show correct answer and explanation

Correct answer: B. A target pathname

Symlinks can reference other paths.

Question 51. Filesystem journaling helps?

  1. Guarantee no data loss ever
  2. Make CPU instructions faster
  3. Recover filesystem consistency after crashes
  4. Prevent all malware
Show correct answer and explanation

Correct answer: C. Recover filesystem consistency after crashes

Logging updates helps recovery from interruptions.

Question 52. A mount point is?

  1. A process exit code
  2. A register
  3. A timer quantum
  4. A path where a filesystem is attached
Show correct answer and explanation

Correct answer: D. A path where a filesystem is attached

Mounting integrates a filesystem into the namespace.

Question 53. SSTF disk scheduling chooses?

  1. The closest pending track request
  2. The oldest request
  3. The largest file
  4. The highest process ID
Show correct answer and explanation

Correct answer: A. The closest pending track request

Shortest seek time first minimizes the next seek distance.

Question 54. SCAN disk scheduling?

  1. Always picks at random
  2. Sweeps requests in one direction then reverses
  3. Avoids moving the head
  4. Uses shortest CPU burst
Show correct answer and explanation

Correct answer: B. Sweeps requests in one direction then reverses

SCAN is sometimes called elevator scheduling.

Question 55. RAID 1 commonly provides?

  1. Striping with no redundancy
  2. Only software compression
  3. Data mirroring
  4. A CPU cache
Show correct answer and explanation

Correct answer: C. Data mirroring

RAID 1 keeps replicated data on multiple drives.

Question 56. RAID 0 lacks?

  1. Striping
  2. Multiple drives
  3. Parallel access possibilities
  4. Data redundancy
Show correct answer and explanation

Correct answer: D. Data redundancy

Failure of one striped drive can affect the whole array.

Question 57. A page cache is used to?

  1. Keep frequently accessed storage data in RAM
  2. Erase all disk data
  3. Store only passwords
  4. Disable buffering
Show correct answer and explanation

Correct answer: A. Keep frequently accessed storage data in RAM

Caching reduces repeated slow storage operations.

Question 58. DMA stands for?

  1. Dynamic memory algorithm
  2. Direct memory access
  3. Disk management architecture
  4. Dual memory address
Show correct answer and explanation

Correct answer: B. Direct memory access

DMA hardware transfers data with reduced CPU intervention.

Question 59. An interrupt generally?

  1. Always shuts down the system
  2. Deletes user files
  3. Transfers control to a handler for an event
  4. Replaces all registers permanently
Show correct answer and explanation

Correct answer: C. Transfers control to a handler for an event

Interrupts signal events requiring processor attention.

Question 60. Polling means?

  1. Waiting only for interrupts
  2. Rebooting after every I/O
  3. Using a filesystem journal
  4. Repeatedly checking a device or condition
Show correct answer and explanation

Correct answer: D. Repeatedly checking a device or condition

Polling explicitly tests status repeatedly.

Question 61. A device driver?

  1. Interfaces OS software with a device
  2. Creates an additional processor
  3. Always allocates swap
  4. Is a user document
Show correct answer and explanation

Correct answer: A. Interfaces OS software with a device

Drivers operate or coordinate hardware devices.

Question 62. A bootloader?

  1. Runs user spreadsheets
  2. Loads or launches OS startup code
  3. Replaces RAM
  4. Performs round robin scheduling
Show correct answer and explanation

Correct answer: B. Loads or launches OS startup code

It transfers control to the OS startup sequence.

Question 63. A daemon is commonly?

  1. A failed CPU core
  2. An unused disk sector
  3. A background service process
  4. A page table entry
Show correct answer and explanation

Correct answer: C. A background service process

Daemons provide background system services.

Question 64. A zombie process has?

  1. No process identifier
  2. Run forever at full CPU
  3. Never been created
  4. Exited but not yet been reaped
Show correct answer and explanation

Correct answer: D. Exited but not yet been reaped

Its parent has not collected its termination status.

Question 65. An orphan process is one whose?

  1. Parent terminated while it continued
  2. Child is blocked
  3. Priority is zero
  4. Page table is empty
Show correct answer and explanation

Correct answer: A. Parent terminated while it continued

A system process or subreaper adopts such children.

Operating Systems MCQs: Set 3 (Questions 66–100)

Choose an answer and reveal the correct option with its explanation.

Question 66. fork() generally?

  1. Always loads a new executable
  2. Creates a child process
  3. Destroys the kernel
  4. Flushes all pages
Show correct answer and explanation

Correct answer: B. Creates a child process

Unix-like fork duplicates a process context.

Question 67. exec() generally?

  1. Always creates a new process
  2. Terminates all children
  3. Replaces the current process program image
  4. Deletes the file system
Show correct answer and explanation

Correct answer: C. Replaces the current process program image

The process continues with a new program image.

Question 68. wait() allows a parent to?

  1. Reset the device
  2. Raise memory frequency
  3. Choose a page frame
  4. Collect a terminated child’s status
Show correct answer and explanation

Correct answer: D. Collect a terminated child’s status

Wait-family calls reap child exit status.

Question 69. A pipe provides?

  1. A byte-stream IPC channel
  2. An address translation table
  3. A page replacement algorithm
  4. A CPU instruction set
Show correct answer and explanation

Correct answer: A. A byte-stream IPC channel

Pipes transmit data between communicating processes.

Question 70. Shared-memory IPC permits?

  1. Only disk communication
  2. Processes to access a common memory region
  3. Automatic race prevention
  4. Separate memory for each process only
Show correct answer and explanation

Correct answer: B. Processes to access a common memory region

Shared memory is efficient but often needs synchronization.

Question 71. A message queue supports?

  1. Only page mapping
  2. Disk head scheduling
  3. Sending and receiving discrete messages
  4. CPU voltage regulation
Show correct answer and explanation

Correct answer: C. Sending and receiving discrete messages

It provides message-oriented IPC.

Question 72. A socket is?

  1. A page frame
  2. A physical memory chip
  3. An interrupt handler only
  4. A communication endpoint
Show correct answer and explanation

Correct answer: D. A communication endpoint

Sockets support local and network communication.

Question 73. A thread pool contains?

  1. Reusable workers for incoming tasks
  2. Only terminated processes
  3. One disk controller
  4. Cache blocks
Show correct answer and explanation

Correct answer: A. Reusable workers for incoming tasks

Reusing workers can reduce thread creation overhead.

Question 74. Priority inversion occurs when?

  1. Every thread has equal priority
  2. A higher-priority task waits for a lower-priority resource holder
  3. The CPU swaps priorities randomly
  4. All interrupts are masked forever
Show correct answer and explanation

Correct answer: B. A higher-priority task waits for a lower-priority resource holder

A lower-priority lock holder can delay a higher-priority task.

Question 75. Priority inheritance helps by?

  1. Preventing all process creation
  2. Changing page size
  3. Temporarily boosting a blocking lock holder
  4. Destroying locks
Show correct answer and explanation

Correct answer: C. Temporarily boosting a blocking lock holder

It mitigates certain forms of priority inversion.

Question 76. A spinlock waits by?

  1. Always sleeping in the kernel
  2. Sending disk messages
  3. Terminating the thread
  4. Repeatedly testing lock availability
Show correct answer and explanation

Correct answer: D. Repeatedly testing lock availability

Busy waiting can be suitable for brief waits.

Question 77. A condition variable helps threads?

  1. Wait for a shared-state condition to change
  2. Manage physical sectors
  3. Translate virtual addresses
  4. Execute privileged instructions
Show correct answer and explanation

Correct answer: A. Wait for a shared-state condition to change

Threads wait and recheck a predicate after notification.

Question 78. A barrier requires participating threads to?

  1. Terminate immediately
  2. Wait until all have arrived
  3. Share a PID
  4. Hold all locks indefinitely
Show correct answer and explanation

Correct answer: B. Wait until all have arrived

Barriers coordinate phases of parallel work.

Question 79. Livelock means processes?

  1. All sleep permanently
  2. Finish normally
  3. Remain active without making progress
  4. Have no memory
Show correct answer and explanation

Correct answer: C. Remain active without making progress

Continual reaction can prevent useful progress.

Question 80. An atomic operation?

  1. Always requires one CPU cycle
  2. Cannot involve memory
  3. Must be executed by one process total
  4. Appears indivisible to competing observers
Show correct answer and explanation

Correct answer: D. Appears indivisible to competing observers

Atomicity hides intermediate states.

Question 81. An access control list defines?

  1. Object permissions for users or groups
  2. CPU speed
  3. Page size
  4. Disk cylinder location
Show correct answer and explanation

Correct answer: A. Object permissions for users or groups

ACL entries specify access rights.

Question 82. Least privilege recommends?

  1. Full administrator rights for everyone
  2. Only permissions needed for a task
  3. No authentication
  4. Unlimited data retention
Show correct answer and explanation

Correct answer: B. Only permissions needed for a task

Restricting permissions limits possible damage.

Question 83. Authentication checks?

  1. Which actions are allowed
  2. How much memory is free
  3. An identity claim
  4. CPU scheduling policy
Show correct answer and explanation

Correct answer: C. An identity claim

Authentication verifies who a subject is.

Question 84. Authorization controls?

  1. Identity verification only
  2. File compression
  3. Clock speed
  4. Permitted actions on resources
Show correct answer and explanation

Correct answer: D. Permitted actions on resources

Authorization decides what access is allowed.

Question 85. A capability is typically?

  1. An unforgeable reference conveying authority
  2. A disk cylinder
  3. A CPU burst
  4. A process state
Show correct answer and explanation

Correct answer: A. An unforgeable reference conveying authority

Capabilities designate resources and associated permissions.

Question 86. Sandboxing aims to?

  1. Give all processes root privileges
  2. Restrict a program’s accessible resources and effects
  3. Eliminate testing
  4. Disable all input
Show correct answer and explanation

Correct answer: B. Restrict a program’s accessible resources and effects

Isolation limits the impact of untrusted code.

Question 87. A hypervisor manages?

  1. Only shell commands
  2. Directory names
  3. Virtual machines
  4. Memory pages only
Show correct answer and explanation

Correct answer: C. Virtual machines

Hypervisors provide and coordinate virtual hardware.

Question 88. Full virtualization lets a guest OS?

  1. Always use the host kernel as its own
  2. Avoid all CPU scheduling
  3. Operate without memory
  4. Run against virtualized hardware
Show correct answer and explanation

Correct answer: D. Run against virtualized hardware

Guest systems see a virtual hardware interface.

Question 89. Containers generally?

  1. Share the host OS kernel
  2. Require a separate physical host each
  3. Emulate every hardware component
  4. Cannot isolate processes
Show correct answer and explanation

Correct answer: A. Share the host OS kernel

OS-level containers isolate workloads with a common kernel.

Question 90. Linux namespaces offer?

  1. Physical disk mirroring
  2. Scoped views of system resources
  3. Password hashing only
  4. Hard-real-time scheduling guarantees
Show correct answer and explanation

Correct answer: B. Scoped views of system resources

Namespaces isolate resources such as process IDs and networking.

Question 91. Linux cgroups support?

  1. Filesystem journaling only
  2. Translation of source code
  3. Process-group resource limits and accounting
  4. Sector-level formatting
Show correct answer and explanation

Correct answer: C. Process-group resource limits and accounting

Control groups track and constrain CPU, memory and other resource use.

Question 92. A real-time OS emphasizes?

  1. Only maximum graphical quality
  2. Only batch jobs
  3. No interrupt processing
  4. Predictable timing and deadline behavior
Show correct answer and explanation

Correct answer: D. Predictable timing and deadline behavior

Real-time systems prioritize timely task completion.

Question 93. Missing a hard real-time deadline?

  1. Can constitute system failure
  2. Is always harmless
  3. Always improves throughput
  4. Means the processor lacks a cache
Show correct answer and explanation

Correct answer: A. Can constitute system failure

Hard real-time correctness includes meeting specified deadlines.

Question 94. Response time in scheduling commonly measures?

  1. Only time spent executing instructions
  2. Delay until the first service or response
  3. Time spent solely on disk
  4. Number of interrupts
Show correct answer and explanation

Correct answer: B. Delay until the first service or response

Scheduling response time is commonly first CPU service minus arrival time.

Question 95. Turnaround time is?

  1. CPU burst minus waiting time
  2. Only I/O wait time
  3. Completion time minus arrival time
  4. Number of times scheduled
Show correct answer and explanation

Correct answer: C. Completion time minus arrival time

Turnaround is total elapsed time from arrival to completion.

Question 96. Waiting time in CPU scheduling is?

  1. Execution time only
  2. Overall turnaround time
  3. Time spent in terminated state
  4. Total time spent in the ready queue
Show correct answer and explanation

Correct answer: D. Total time spent in the ready queue

Waiting time counts intervals ready but not executing.

Question 97. Throughput means?

  1. Completed tasks per unit time
  2. Percent disk capacity
  3. Mean process identifier
  4. Total available memory
Show correct answer and explanation

Correct answer: A. Completed tasks per unit time

Throughput is the completion rate.

Question 98. CPU utilization is?

  1. The number of processors
  2. The proportion of measured CPU time spent busy
  3. The number of loaded files
  4. RAM allocated to the kernel
Show correct answer and explanation

Correct answer: B. The proportion of measured CPU time spent busy

Utilization compares busy time with available processor time.

Question 99. Multiprogramming helps CPU utilization by?

  1. Disabling all I/O
  2. Preventing context switches
  3. Running another task while one waits for I/O
  4. Requiring one process only
Show correct answer and explanation

Correct answer: C. Running another task while one waits for I/O

Other runnable tasks can occupy the CPU during I/O waits.

Question 100. Which technique helps reduce busy waiting for long resource waits?

  1. Using an endless spin loop
  2. Disabling the scheduler
  3. Continuously polling at maximum speed
  4. Blocking a thread until notification
Show correct answer and explanation

Correct answer: D. Blocking a thread until notification

Blocking lets other runnable work use the CPU instead of wasting cycles.

Operating Systems MCQs: Set 4 (Questions 101–150)

Answer each question and reveal the explanation.

Question 101. A CPU burst is?

  1. An interval when a task executes on the CPU
  2. Time spent waiting for disk I/O
  3. A memory allocation unit
  4. A directory operation
Show correct answer and explanation

Correct answer: A. An interval when a task executes on the CPU

A CPU burst is continuous CPU execution between waits or preemptions.

Question 102. For nonpreemptive FCFS, tasks A(4 ms) then B(3 ms) both arriving at time zero yield B waiting time of?

  1. 0 ms
  2. 4 ms
  3. 3 ms
  4. 7 ms
Show correct answer and explanation

Correct answer: B. 4 ms

B waits for A’s four-millisecond burst.

Question 103. For a process arriving at time 2 and completing at time 11, turnaround time is?

  1. 11 time units
  2. 13 time units
  3. 9 time units
  4. 2 time units
Show correct answer and explanation

Correct answer: C. 9 time units

Turnaround equals 11 minus 2, or 9.

Question 104. If a task’s turnaround is 12 ms and its CPU burst is 5 ms with no I/O, its waiting time is?

  1. 5 ms
  2. 12 ms
  3. 17 ms
  4. 7 ms
Show correct answer and explanation

Correct answer: D. 7 ms

For this simple model, waiting equals turnaround minus burst, or 7.

Question 105. A preemptive scheduler can?

  1. Interrupt a running process to run another
  2. Switch tasks only on termination
  3. Never use interrupts
  4. Run only one application in the system
Show correct answer and explanation

Correct answer: A. Interrupt a running process to run another

Preemption allows the OS to suspend a currently executing task.

Question 106. Which scheduler normally chooses from the ready queue for the next CPU allocation?

  1. Long-term scheduler only
  2. Short-term scheduler
  3. File-system allocator
  4. Disk controller
Show correct answer and explanation

Correct answer: B. Short-term scheduler

The short-term scheduler dispatches ready tasks.

Question 107. The long-term scheduler primarily controls?

  1. Memory address translation
  2. Filesystem permissions
  3. Admission of jobs and degree of multiprogramming
  4. Interrupt vector entries
Show correct answer and explanation

Correct answer: C. Admission of jobs and degree of multiprogramming

Job admission regulates how many processes enter the active system.

Question 108. An I/O-bound task generally has?

  1. Only very long CPU bursts
  2. No blocked states
  3. No process control block
  4. Frequent I/O waits with relatively short CPU bursts
Show correct answer and explanation

Correct answer: D. Frequent I/O waits with relatively short CPU bursts

I/O-bound work often alternates small CPU bursts and device waits.

Question 109. The convoy effect under FCFS refers to?

  1. Short jobs waiting behind a long-running job
  2. Tasks receiving equal CPU time
  3. A virtual memory mapping error
  4. Several disks being mirrored
Show correct answer and explanation

Correct answer: A. Short jobs waiting behind a long-running job

One long CPU-bound job can delay shorter jobs.

Question 110. A multilevel feedback queue scheduler may?

  1. Require all tasks to have equal fixed priority forever
  2. Move tasks between queues based on observed behavior
  3. Eliminate all starvation automatically
  4. Use no time quantum
Show correct answer and explanation

Correct answer: B. Move tasks between queues based on observed behavior

Feedback queues dynamically adjust scheduling priorities or classes.

Question 111. The dispatcher is responsible for?

  1. Assigning filenames to inodes
  2. Encrypting all files
  3. Transferring CPU control to the selected task
  4. Changing physical RAM capacity
Show correct answer and explanation

Correct answer: C. Transferring CPU control to the selected task

Dispatching involves context switching and transfer to the chosen execution context.

Question 112. Dispatch latency measures?

  1. Total time for a hard drive to boot
  2. A page’s virtual address
  3. Average file size
  4. Time needed to stop one task and start another
Show correct answer and explanation

Correct answer: D. Time needed to stop one task and start another

Dispatcher overhead adds latency to scheduling transitions.

Question 113. A thread’s own execution state typically includes?

  1. Program counter, registers and stack
  2. Only a shared process heap
  3. Only filesystem inode
  4. All other threads’ registers
Show correct answer and explanation

Correct answer: A. Program counter, registers and stack

Threads maintain individual control and stack state.

Question 114. User-level threading can have a limitation when the kernel sees only one schedulable entity?

  1. Each user thread must own a disk
  2. A blocking system call may block all its user threads
  3. Processes cannot share memory
  4. CPU instructions become privileged
Show correct answer and explanation

Correct answer: B. A blocking system call may block all its user threads

Some many-to-one threading implementations block an entire process on a blocking syscall.

Question 115. The many-to-one thread mapping model maps?

  1. One user thread onto many kernels
  2. Each thread to a different disk
  3. Many user threads onto one kernel thread
  4. One process to one filesystem
Show correct answer and explanation

Correct answer: C. Many user threads onto one kernel thread

Many-to-one user threads share a kernel scheduling entity.

Question 116. A multicore processor can allow?

  1. Only serial execution under all conditions
  2. No context switches
  3. No thread communication
  4. Actual parallel execution of different threads on different cores
Show correct answer and explanation

Correct answer: D. Actual parallel execution of different threads on different cores

Distinct CPU cores can execute tasks at the same time.

Question 117. Concurrency differs from parallelism because concurrency?

  1. Concerns overlapping progress, not necessarily simultaneous execution
  2. Always requires multiple physical CPUs
  3. Never involves shared state
  4. Means running exactly four threads
Show correct answer and explanation

Correct answer: A. Concerns overlapping progress, not necessarily simultaneous execution

A single core can interleave concurrent activities without true simultaneous execution.

Question 118. Amdahl’s law implies that?

  1. More cores always give unlimited speedup
  2. A serial portion limits speedup from parallelization
  3. A parallel program never has overhead
  4. Scheduling never affects performance
Show correct answer and explanation

Correct answer: B. A serial portion limits speedup from parallelization

Unparallelizable work limits theoretical overall speedup.

Question 119. If half a workload is strictly serial, maximum speedup as processor count approaches infinity is?

  1. 4
  2. 8
  3. 2
  4. Unlimited
Show correct answer and explanation

Correct answer: C. 2

Amdahl’s bound is 1 / 0.5 = 2.

Question 120. Which property requires a critical-section algorithm to eventually let waiting participants make progress under suitable conditions?

  1. Disk mirroring
  2. File locking alone
  3. Memory compaction
  4. Bounded waiting
Show correct answer and explanation

Correct answer: D. Bounded waiting

Bounded waiting limits overtaking before a waiting participant can enter.

Question 121. A counting semaphore initialized to 3 can represent?

  1. Three simultaneously available resource units
  2. Exactly one CPU
  3. Three processes that must terminate
  4. Three page faults
Show correct answer and explanation

Correct answer: A. Three simultaneously available resource units

The count can track multiple interchangeable resource instances.

Question 122. The producer–consumer problem illustrates?

  1. Only address translation
  2. Synchronization over a shared bounded buffer
  3. Filesystem indexing
  4. Disk partitioning
Show correct answer and explanation

Correct answer: B. Synchronization over a shared bounded buffer

Producers and consumers coordinate access and available slots.

Question 123. A lost wakeup is a synchronization problem in which?

  1. A process loses its filename
  2. The CPU discards the next instruction
  3. A notification can be missed because waiting is not coordinated correctly
  4. A disk loses power
Show correct answer and explanation

Correct answer: C. A notification can be missed because waiting is not coordinated correctly

Correct synchronization must prevent races between checking predicates and sleeping.

Question 124. Why must condition-variable waits usually recheck a predicate in a loop?

  1. The lock is never released
  2. The CPU never interrupts threads
  3. All conditions are permanent
  4. Wakeups may occur without the desired condition being true
Show correct answer and explanation

Correct answer: D. Wakeups may occur without the desired condition being true

Spurious wakeups or competing threads can invalidate the predicate.

Question 125. Deadlock detection differs from deadlock prevention because it?

  1. Allows deadlocks to arise and subsequently identifies them
  2. Removes all circular wait by design
  3. Always preallocates every resource
  4. Requires only one process
Show correct answer and explanation

Correct answer: A. Allows deadlocks to arise and subsequently identifies them

Detection finds problematic resource cycles or allocation states after they occur.

Question 126. Resource allocation graphs with one instance per resource type can indicate deadlock when?

  1. No edges exist
  2. A directed cycle exists
  3. Every process is ready
  4. All resources are free
Show correct answer and explanation

Correct answer: B. A directed cycle exists

With single-instance resource types, a cycle implies deadlock.

Question 127. Deadlock recovery can involve?

  1. Only disabling authentication
  2. Always increasing CPU clock speed
  3. Terminating processes or preempting recoverable resources
  4. Formatting the system partition
Show correct answer and explanation

Correct answer: C. Terminating processes or preempting recoverable resources

Recovery may break a cycle by rollback, termination or resource intervention.

Question 128. A wait-for graph represents?

  1. Filesystem hierarchy only
  2. Page replacement order
  3. Routing information only
  4. Dependencies among processes waiting for resources held by others
Show correct answer and explanation

Correct answer: D. Dependencies among processes waiting for resources held by others

Wait-for edges indicate process-to-process waiting dependencies.

Question 129. A reentrant lock permits?

  1. Its owning thread to acquire it recursively under defined semantics
  2. Every thread to enter simultaneously
  3. No thread to release it
  4. Only processes to use it
Show correct answer and explanation

Correct answer: A. Its owning thread to acquire it recursively under defined semantics

A reentrant mutex tracks recursive ownership by the same thread.

Question 130. Readers–writers locks typically allow?

  1. Unlimited simultaneous writers
  2. Multiple simultaneous readers or one exclusive writer
  3. Exactly one reader under all conditions
  4. No lock acquisition by readers
Show correct answer and explanation

Correct answer: B. Multiple simultaneous readers or one exclusive writer

The design separates shared read access from exclusive write access.

Question 131. A memory address generated by a program before translation is commonly called?

  1. Physical sector number
  2. Device IRQ
  3. Virtual or logical address
  4. Disk cylinder
Show correct answer and explanation

Correct answer: C. Virtual or logical address

A process operates in virtual address space before translation.

Question 132. A physical address identifies?

  1. A filename
  2. A process exit status
  3. A page replacement priority
  4. A location in hardware-addressable memory
Show correct answer and explanation

Correct answer: D. A location in hardware-addressable memory

MMU translation yields a physical memory address.

Question 133. For a page size of 4 KiB, a 12-bit page offset can address?

  1. 4096 byte positions
  2. 1024 byte positions
  3. 512 byte positions
  4. 8192 byte positions
Show correct answer and explanation

Correct answer: A. 4096 byte positions

2^12 = 4096 bytes.

Question 134. A virtual address of 8200 with page size 4096 has page number?

  1. 1
  2. 2
  3. 3
  4. 8
Show correct answer and explanation

Correct answer: B. 2

Integer division 8200 // 4096 yields virtual page 2.

Question 135. The offset for virtual address 8200 and page size 4096 is?

  1. 0
  2. 16
  3. 8
  4. 4096
Show correct answer and explanation

Correct answer: C. 8

8200 – 2×4096 = 8.

Question 136. An inverted page table usually has entries indexed mainly by?

  1. Directory names
  2. CPU thread priorities
  3. File extensions
  4. Physical frames rather than every virtual page of every process
Show correct answer and explanation

Correct answer: D. Physical frames rather than every virtual page of every process

An inverted structure records mappings for physical frames, reducing certain table overheads.

Question 137. A multilevel page table helps by?

  1. Allocating translation structures on demand for used address ranges
  2. Making all page faults impossible
  3. Eliminating virtual addresses
  4. Guaranteeing a TLB hit
Show correct answer and explanation

Correct answer: A. Allocating translation structures on demand for used address ranges

Hierarchical tables need not allocate entries for entirely unused ranges.

Question 138. A TLB miss necessarily means?

  1. The entire process must terminate
  2. A cached translation was not found, but the page may still be resident
  3. The disk must be faulty
  4. A page fault always occurred
Show correct answer and explanation

Correct answer: B. A cached translation was not found, but the page may still be resident

A TLB miss can be resolved by consulting page tables without a disk access.

Question 139. A valid or present page-table bit often indicates?

  1. Whether the filename has been saved
  2. Whether the CPU has two cores
  3. Whether a mapping is valid or resident according to the architecture
  4. Whether a process owns a lock
Show correct answer and explanation

Correct answer: C. Whether a mapping is valid or resident according to the architecture

Architectures use presence/validity bits to determine accessible mappings.

Question 140. A dirty page is a page that?

  1. Has never been accessed
  2. Cannot be mapped
  3. Is always shared read-only
  4. Has been modified since it was loaded or last written back
Show correct answer and explanation

Correct answer: D. Has been modified since it was loaded or last written back

Dirty state indicates the backing copy may require updating.

Question 141. The reference bit in a page-table entry can assist?

  1. Approximate recency-based page replacement
  2. CPU power supply control
  3. Disk partition formatting
  4. File naming
Show correct answer and explanation

Correct answer: A. Approximate recency-based page replacement

Reference information can guide clock and related algorithms.

Question 142. Clock page replacement uses?

  1. Full future reference knowledge
  2. A circular scan and reference bits to approximate LRU
  3. Only process identifiers
  4. Disk sector numbers
Show correct answer and explanation

Correct answer: B. A circular scan and reference bits to approximate LRU

The clock algorithm gives referenced pages another chance.

Question 143. A page-replacement algorithm with the stack property has?

  1. Guaranteed constant fault rate
  2. No memory references
  3. Nonincreasing fault count as allocated frame count grows
  4. An identical result to FIFO on every trace
Show correct answer and explanation

Correct answer: C. Nonincreasing fault count as allocated frame count grows

Stack algorithms retain the smaller-frame pages within larger-frame resident sets.

Question 144. A page table’s execute-disable permission is meant to?

  1. Prevent page reads
  2. Always disable write access
  3. Make pages physically contiguous
  4. Prevent instruction execution from protected pages
Show correct answer and explanation

Correct answer: D. Prevent instruction execution from protected pages

NX or execute-disable bits restrict code execution in designated regions.

Question 145. Address space layout randomization (ASLR) aims to?

  1. Make key process memory locations harder to predict
  2. Eliminate page tables
  3. Encrypt every CPU register
  4. Prevent all programming errors
Show correct answer and explanation

Correct answer: A. Make key process memory locations harder to predict

ASLR randomizes selected address locations to hinder certain exploits.

Question 146. Memory protection between processes helps?

  1. Force all processes to share one stack
  2. Prevent unauthorized reading or writing across address spaces
  3. Guarantee process completion
  4. Avoid all disk I/O
Show correct answer and explanation

Correct answer: B. Prevent unauthorized reading or writing across address spaces

Per-process mappings and access rights enforce isolation.

Question 147. The heap in a conventional process layout is commonly used for?

  1. Storing only CPU flags
  2. The bootloader
  3. Dynamic memory allocation
  4. Physical disk sectors
Show correct answer and explanation

Correct answer: C. Dynamic memory allocation

Many programs allocate variable-lifetime objects from the heap.

Question 148. A stack is commonly used for?

  1. Permanent file storage
  2. Disk device registers only
  3. Process scheduling priorities
  4. Function call frames and automatic local variables
Show correct answer and explanation

Correct answer: D. Function call frames and automatic local variables

The call stack tracks nested calls, return addresses and local state.

Question 149. A guard page near a stack can help?

  1. Detect some stack overflows through access faults
  2. Automatically increase CPU performance
  3. Prevent all deadlocks
  4. Guarantee no segmentation fault
Show correct answer and explanation

Correct answer: A. Detect some stack overflows through access faults

An inaccessible guard region can expose out-of-bounds stack growth.

Question 150. Which mechanism permits memory allocation without moving every existing process segment?

  1. Only contiguous partitions
  2. Paging
  3. Only compaction
  4. Only fixed single-task memory
Show correct answer and explanation

Correct answer: B. Paging

Paging maps noncontiguous physical frames to a contiguous virtual view.

Operating Systems MCQs: Set 5 (Questions 151–200)

Read each question and check the answer with its explanation.

Question 151. A filesystem block allocation bitmap records?

  1. Which CPU task runs next
  2. Which keyboard key was pressed
  3. Which disk blocks are free or allocated
  4. How many threads exist
Show correct answer and explanation

Correct answer: C. Which disk blocks are free or allocated

A bitmap tracks allocation status for storage blocks.

Question 152. Contiguous file allocation can suffer from?

  1. An inability to read sequentially
  2. An absence of any metadata
  3. Only process deadlocks
  4. External fragmentation and difficulty growing files
Show correct answer and explanation

Correct answer: D. External fragmentation and difficulty growing files

Contiguous extents can be hard to grow when nearby space is occupied.

Question 153. Indexed file allocation uses?

  1. An index of block addresses for a file
  2. A separate CPU for each block
  3. Only adjacent blocks
  4. A semaphore counter
Show correct answer and explanation

Correct answer: A. An index of block addresses for a file

An index structure points to storage blocks belonging to a file.

Question 154. A file descriptor in a Unix-like process is?

  1. The entire file’s content
  2. A small integer handle referring to an open file description
  3. A disk cylinder number
  4. The process priority
Show correct answer and explanation

Correct answer: B. A small integer handle referring to an open file description

The process descriptor table maps integers to opened resources.

Question 155. What does an open() system call typically return on success in Unix-like systems?

  1. A physical disk address
  2. The entire file
  3. A nonnegative file descriptor
  4. A memory page number
Show correct answer and explanation

Correct answer: C. A nonnegative file descriptor

The returned descriptor is used in later operations such as read and write.

Question 156. The read() operation on a regular file generally?

  1. Always deletes the file
  2. Increases process priority
  3. Changes the inode type
  4. Transfers bytes from the file to a user-provided buffer
Show correct answer and explanation

Correct answer: D. Transfers bytes from the file to a user-provided buffer

A read obtains file content and may advance the file offset.

Question 157. The seek operation on a seekable open file changes?

  1. The current file offset
  2. The CPU register count
  3. The size of physical RAM
  4. The user’s group ID
Show correct answer and explanation

Correct answer: A. The current file offset

File-position operations set where subsequent reads or writes occur.

Question 158. What is a file’s access time metadata often intended to record?

  1. The file’s source code language
  2. The last access time under applicable filesystem policy
  3. The last CPU dispatch time
  4. The owner’s password
Show correct answer and explanation

Correct answer: B. The last access time under applicable filesystem policy

Access-time metadata can be updated on reads depending on mount and filesystem settings.

Question 159. A filesystem crash-consistency guarantee concerns?

  1. Faster CPU vector instructions
  2. Network routing efficiency
  3. Valid on-disk structures after interrupted updates
  4. Password complexity
Show correct answer and explanation

Correct answer: C. Valid on-disk structures after interrupted updates

Crash consistency addresses partially completed persistent operations.

Question 160. What does fsync() aim to do for a file descriptor?

  1. Schedule a process on a CPU
  2. Replace a filename with another process
  3. Immediately reboot the system
  4. Request synchronization of modified file data and associated metadata to stable storage
Show correct answer and explanation

Correct answer: D. Request synchronization of modified file data and associated metadata to stable storage

fsync requests that relevant buffered updates be persisted according to system guarantees.

Question 161. Write-back caching differs from write-through because it?

  1. Can defer propagation of writes to lower storage levels
  2. Always writes every change synchronously
  3. Cannot hold dirty data
  4. Eliminates consistency concerns
Show correct answer and explanation

Correct answer: A. Can defer propagation of writes to lower storage levels

Write-back caches may temporarily retain modified data.

Question 162. Sequential disk access is often faster than random access on hard disks because?

  1. Every request skips the controller
  2. It reduces repeated seek and rotational overhead
  3. It avoids all copying
  4. It disables caching
Show correct answer and explanation

Correct answer: B. It reduces repeated seek and rotational overhead

Mechanical head movement makes scattered accesses costly.

Question 163. Solid-state drives generally have lower random access latency than magnetic disks because?

  1. They require a moving disk head
  2. They have no controller
  3. They lack mechanical seek and rotation
  4. They cannot perform block reads
Show correct answer and explanation

Correct answer: C. They lack mechanical seek and rotation

Flash storage does not require moving mechanical heads.

Question 164. Wear leveling in flash storage aims to?

  1. Make every file size equal
  2. Prevent all read operations
  3. Increase CPU context switches
  4. Distribute erase cycles across flash cells
Show correct answer and explanation

Correct answer: D. Distribute erase cycles across flash cells

Flash cells have finite program/erase endurance.

Question 165. TRIM on supported SSD storage informs the device?

  1. Which logical blocks are no longer needed
  2. Which process should run next
  3. Which network address was allocated
  4. How many threads are blocked
Show correct answer and explanation

Correct answer: A. Which logical blocks are no longer needed

Discard hints can help SSD firmware manage invalidated storage blocks.

Question 166. Disk partitioning divides a device into?

  1. Separate CPU cores
  2. Logical regions that can be managed separately
  3. Multiple running programs
  4. Virtual CPU instructions
Show correct answer and explanation

Correct answer: B. Logical regions that can be managed separately

Partitions define addressable storage regions.

Question 167. A block device interface commonly transfers data in?

  1. Only individual characters
  2. Only network packets
  3. Addressable blocks or sectors
  4. Only CPU instructions
Show correct answer and explanation

Correct answer: C. Addressable blocks or sectors

Block devices offer random-addressed block access abstractions.

Question 168. A character device is commonly modeled as?

  1. A fixed-address disk
  2. A page table
  3. An instruction cache
  4. A stream-oriented I/O device
Show correct answer and explanation

Correct answer: D. A stream-oriented I/O device

Character device interfaces often expose streams rather than random-access blocks.

Question 169. A hardware interrupt vector or table helps?

  1. Locate the handler for a particular interrupt or exception
  2. Select a user’s home directory
  3. Determine a process’s file offset
  4. Compress application data
Show correct answer and explanation

Correct answer: A. Locate the handler for a particular interrupt or exception

The processor uses configured interrupt/exception entries to dispatch handlers.

Question 170. An exception differs from an ordinary asynchronous device interrupt because it?

  1. Can never enter kernel mode
  2. Is typically associated with execution of the current instruction
  3. Must be caused by a network card
  4. Always means hardware failure
Show correct answer and explanation

Correct answer: B. Is typically associated with execution of the current instruction

Synchronous exceptions arise from instruction execution, such as faults or traps.

Question 171. A trap is often used for?

  1. File defragmentation only
  2. Choosing the largest process
  3. Intentional transfer into a privileged handler, including system calls
  4. Mirroring disks
Show correct answer and explanation

Correct answer: C. Intentional transfer into a privileged handler, including system calls

Architectures use traps or related exception mechanisms for controlled OS entry.

Question 172. What does a timer interrupt enable?

  1. Removal of all thread states
  2. Disk mirroring without a controller
  3. Elimination of system calls
  4. Periodic opportunities for the OS to regain control and preempt work
Show correct answer and explanation

Correct answer: D. Periodic opportunities for the OS to regain control and preempt work

Timers support preemptive scheduling and time accounting.

Question 173. An interrupt service routine should often be kept short because?

  1. Lengthy handlers increase interrupt latency and disrupt other work
  2. It must never access memory
  3. It cannot communicate with drivers
  4. It always runs in user mode
Show correct answer and explanation

Correct answer: A. Lengthy handlers increase interrupt latency and disrupt other work

Extended interrupt handling delays other system activity.

Question 174. Kernel space and user space separation primarily supports?

  1. Doubling physical memory
  2. Protection and controlled privileged operations
  3. Eliminating all hardware faults
  4. Replacing device drivers
Show correct answer and explanation

Correct answer: B. Protection and controlled privileged operations

Privilege boundaries prevent ordinary applications from arbitrarily accessing kernel resources.

Question 175. A microkernel architecture tends to move?

  1. Every application into hardware firmware
  2. All system calls into disk sectors
  3. Many services into user-space processes
  4. The CPU scheduler into source files
Show correct answer and explanation

Correct answer: C. Many services into user-space processes

Microkernels keep a small trusted core while moving services outside it.

Question 176. A monolithic kernel commonly includes?

  1. Only a command-line shell
  2. No scheduling logic
  3. One user application per kernel
  4. Many OS services and drivers within kernel address space
Show correct answer and explanation

Correct answer: D. Many OS services and drivers within kernel address space

Monolithic kernels implement a broad set of services in privileged code.

Question 177. A hybrid kernel design generally?

  1. Combines characteristics of different kernel architectural approaches
  2. Disables all drivers
  3. Runs without a kernel mode
  4. Always requires two physical processors
Show correct answer and explanation

Correct answer: A. Combines characteristics of different kernel architectural approaches

Hybrid designs blend monolithic and microkernel features.

Question 178. Kernel modules are commonly used to?

  1. Edit user documents
  2. Load or unload selected kernel functionality dynamically
  3. Replace file permissions automatically
  4. Remove virtual memory
Show correct answer and explanation

Correct answer: B. Load or unload selected kernel functionality dynamically

Modular kernels can extend capabilities with loadable components.

Question 179. A shell is primarily?

  1. A page replacement algorithm
  2. A physical CPU package
  3. A command interpreter or interface for interacting with the OS
  4. A disk sector map
Show correct answer and explanation

Correct answer: C. A command interpreter or interface for interacting with the OS

Shells parse commands and initiate programs or shell built-ins.

Question 180. An environment variable is?

  1. A physical RAM frame
  2. An immutable disk sector
  3. A privilege mode
  4. A named value provided in a process environment
Show correct answer and explanation

Correct answer: D. A named value provided in a process environment

Programs can read named environment entries such as PATH.

Question 181. PATH on many Unix-like systems is used to?

  1. List directories searched for executable commands
  2. Store all physical addresses
  3. Define the number of CPU cores
  4. Set every file’s owner
Show correct answer and explanation

Correct answer: A. List directories searched for executable commands

Command lookup searches directories named in PATH.

Question 182. A signal in Unix-like operating systems is?

  1. A dedicated disk partition
  2. An asynchronous software notification to a process or thread
  3. A page table level
  4. A file allocation method
Show correct answer and explanation

Correct answer: B. An asynchronous software notification to a process or thread

Signals notify execution contexts about events such as termination requests.

Question 183. SIGKILL on Unix-like systems typically?

  1. Requests a graceful handler that must run
  2. Always suspends the process for exactly one second
  3. Terminates a process and cannot be caught or ignored
  4. Flushes all filesystem caches
Show correct answer and explanation

Correct answer: C. Terminates a process and cannot be caught or ignored

SIGKILL forces termination through the kernel’s signal machinery.

Question 184. SIGTERM is typically used to?

  1. Guarantee uncatchable termination
  2. Reformat a disk
  3. Increase process priority
  4. Request a process to terminate, allowing it to handle the request
Show correct answer and explanation

Correct answer: D. Request a process to terminate, allowing it to handle the request

SIGTERM can be caught to perform cleanup.

Question 185. A file permission mode such as rw-r–r– means?

  1. Owner can read/write; group and others can read
  2. Every user can execute
  3. Only the owner can read
  4. The file is encrypted
Show correct answer and explanation

Correct answer: A. Owner can read/write; group and others can read

The three permission triplets describe owner, group and other access.

Question 186. The execute permission on a directory in Unix-like systems mainly enables?

  1. Running the directory as a program
  2. Traversing or searching through that directory
  3. Compressing its contents
  4. Deleting every file automatically
Show correct answer and explanation

Correct answer: B. Traversing or searching through that directory

Directory execute permission controls traversal and pathname resolution.

Question 187. The setuid bit on an executable may cause it to?

  1. Always disable authentication
  2. Run only as its invoking user in all cases
  3. Run with the file owner’s effective user ID under applicable rules
  4. Increase CPU utilization
Show correct answer and explanation

Correct answer: C. Run with the file owner’s effective user ID under applicable rules

Setuid can change effective credentials when permitted and not suppressed.

Question 188. A user ID (UID) is used to?

  1. Locate a virtual page
  2. Number disk tracks
  3. Choose timer frequency
  4. Identify a user for access-control decisions
Show correct answer and explanation

Correct answer: D. Identify a user for access-control decisions

UIDs are operating-system identity attributes.

Question 189. Audit logging helps security by?

  1. Recording relevant system events for investigation and accountability
  2. Preventing every exploit automatically
  3. Replacing backups
  4. Removing all access controls
Show correct answer and explanation

Correct answer: A. Recording relevant system events for investigation and accountability

Audit logs provide evidence about security-relevant activity.

Question 190. A race involving a time-of-check-to-time-of-use (TOCTOU) vulnerability occurs when?

  1. A file is always read atomically
  2. A checked condition can change before an operation relies on it
  3. The CPU runs with one core
  4. The operating system never preempts
Show correct answer and explanation

Correct answer: B. A checked condition can change before an operation relies on it

Attackers can exploit a gap between checking state and using it.

Question 191. A reference monitor is intended to?

  1. Replace every driver
  2. Optimize disk seeks
  3. Mediate security-sensitive access according to policy
  4. Compile shell scripts
Show correct answer and explanation

Correct answer: C. Mediate security-sensitive access according to policy

The reference-monitor idea emphasizes complete mediation and tamper resistance.

Question 192. A kernel panic generally indicates?

  1. Successful process completion
  2. A user-space warning only
  3. A normal disk scheduling event
  4. A severe kernel error from which normal operation cannot safely continue
Show correct answer and explanation

Correct answer: D. A severe kernel error from which normal operation cannot safely continue

The kernel may halt or reboot after an unrecoverable fault.

Question 193. System uptime measures?

  1. Elapsed time since the system last booted
  2. Total time spent in user mode only
  3. The disk’s age
  4. Average application run time
Show correct answer and explanation

Correct answer: A. Elapsed time since the system last booted

Uptime records duration of continuous system operation since startup.

Question 194. A watchdog timer can be used to?

  1. Allocate virtual memory pages
  2. Detect missing progress and trigger recovery actions
  3. Perform cryptographic hashing
  4. Replace filesystem permissions
Show correct answer and explanation

Correct answer: B. Detect missing progress and trigger recovery actions

Software or hardware must periodically service a watchdog to avoid its timeout.

Question 195. Checkpointing supports fault tolerance by?

  1. Ensuring programs never crash
  2. Removing all disk writes
  3. Saving recoverable execution state periodically
  4. Forcing all tasks to be real time
Show correct answer and explanation

Correct answer: C. Saving recoverable execution state periodically

A checkpoint may help restart work from a recent state.

Question 196. A snapshot in a storage system commonly represents?

  1. A CPU scheduling queue
  2. An interrupt vector
  3. A thread stack
  4. A preserved point-in-time view of data
Show correct answer and explanation

Correct answer: D. A preserved point-in-time view of data

Snapshots capture a storage state, often using copy-on-write mechanisms.

Question 197. What does a backup provide that RAID redundancy alone may not?

  1. Recovery from accidental deletion or logical corruption
  2. A higher CPU clock
  3. More available registers
  4. Automatic process prioritization
Show correct answer and explanation

Correct answer: A. Recovery from accidental deletion or logical corruption

Drive redundancy does not replace independently recoverable copies.

Question 198. A distributed filesystem commonly aims to?

  1. Eliminate all network communication
  2. Provide file access across multiple networked machines
  3. Require all files on one local disk
  4. Replace user accounts with PIDs
Show correct answer and explanation

Correct answer: B. Provide file access across multiple networked machines

Distributed filesystems expose shared data across systems.

Question 199. File locking is used to?

  1. Convert files to hard links
  2. Compress every write
  3. Coordinate access to shared files or file regions
  4. Allocate memory frames
Show correct answer and explanation

Correct answer: C. Coordinate access to shared files or file regions

Locks help applications coordinate concurrent access.

Question 200. Which is a sensible approach to OS performance measurement?

  1. Evaluate only a single unexplained number
  2. Assume all hardware behaves identically
  3. Avoid recording configurations
  4. Measure defined workloads with relevant latency, throughput and utilization metrics
Show correct answer and explanation

Correct answer: D. Measure defined workloads with relevant latency, throughput and utilization metrics

Meaningful performance comparisons require workloads and reproducible metrics.

Privacy Policy
Powered by CookieAdmin