When a running process makes a system call, what controlled transition usually occurs in CPU privilege level
A Kernel to user
B Disk to RAM
C User to kernel
D Cache to disk
Note: A system call switches the CPU from user mode to kernel mode so the OS can perform protected operations safely. After the service completes, control returns to user mode for the program.
Which CPU protection feature ensures user programs cannot directly execute privileged hardware instructions
A Single task mode
B Dual mode operation
C Fast boot mode
D Safe mode boot
Note: Dual mode operation separates user mode and kernel mode. Privileged instructions run only in kernel mode, protecting hardware and critical memory from direct access by user applications.
In a paged memory system, what does the MMU primarily use to translate virtual addresses
A Page tables
B Boot records
C File indexes
D Screen buffers
Note: The MMU uses page tables to map virtual pages to physical frames. This translation supports memory isolation, virtual memory, and controlled access, preventing processes from reading or writing others’ memory.
If the TLB does not contain a needed translation, what event occurs first before checking full page tables
A Page fault
B Disk crash
C TLB miss
D Kernel panic
Note: A TLB miss means the fast translation cache lacks the mapping. The system then checks the page table. Only if the page is not in RAM does a page fault occur.
In virtual memory, what is the best description of a “working set” for a process
A Total disk capacity
B CPU cache size
C Full program size
D Actively used pages
Note: The working set is the set of memory pages a process is currently using frequently. If RAM cannot hold the working set, page faults increase and performance may drop sharply.
Why does thrashing severely reduce system performance in a multiprogramming environment
A Excessive paging activity
B More CPU registers
C Larger disk sectors
D Faster GUI rendering
Note: During thrashing, the OS spends most time swapping pages between RAM and disk instead of executing instructions. CPU utilization falls and response time becomes very slow for all processes.
In a preemptive OS, which event can force a running process to stop before it finishes its CPU burst
A Disk formatting
B File copying
C Timer interrupt
D GUI resizing
Note: A timer interrupt can preempt a running process when its time slice ends. The OS saves its state and schedules another process, improving fairness and responsiveness in multitasking systems.
Which scheduling method may cause starvation if priorities are fixed and no aging is applied
A Priority scheduling
B Round robin
C FCFS scheduling
D Shortest job
Note: With fixed priorities, high-priority jobs can keep running while low-priority jobs wait indefinitely. Aging is used to raise waiting processes’ priority over time to prevent starvation.
In CPU scheduling, what is the main goal of the “shortest remaining time” strategy
A Maximize disk space
B Reduce boot time
C Increase screen clarity
D Minimize average waiting
Note: Shortest Remaining Time First selects the process with the least remaining CPU time. It often lowers average waiting and turnaround time, but it requires predicting burst times and can starve long jobs.
Which OS mechanism prevents two threads from entering a critical section at the same time
A Disk defragment
B File compression
C Mutual exclusion
D Window snapping
Note: Mutual exclusion ensures only one thread accesses shared critical data at a time. It prevents race conditions and corruption, typically using locks, mutexes, semaphores, or monitors.
A deadlock requires several conditions; which is one essential condition that must be present
A Circular wait
B High disk speed
C Fast boot mode
D GUI acceleration
Note: Deadlock occurs when processes wait forever for resources held by each other. Circular wait is one required condition, where a closed chain of processes each waits for a resource held by the next.
Which method avoids deadlock by ensuring a safe resource allocation state before granting requests
A FIFO paging
B Disk caching
C Fast startup
D Banker’s algorithm
Note: Banker’s algorithm checks whether granting a resource request keeps the system in a safe state. If not, the request is delayed, preventing deadlock situations in resource allocation.
In memory protection, what does a base register and limit register pair mainly enforce
A Faster disk writing
B Valid address range
C More CPU cores
D Stronger Wi-Fi signal
Note: Base and limit registers restrict a process to a specific memory range. Any access outside the allowed range triggers protection, preventing a process from accessing memory belonging to the OS or other processes.
In segmentation, what is a key difference compared to paging
A Fixed-sized blocks
B No address translation
C Variable-sized blocks
D No memory protection
Note: Segmentation divides memory into variable-sized logical segments like code and data, matching program structure. Paging uses fixed-size pages. Segmentation can cause external fragmentation while paging reduces it.
Which file system concept is most directly improved by journaling after sudden power loss
A Metadata consistency
B Screen refresh rate
C CPU clock speed
D Keyboard response
Note: Journaling records intended file system changes before final commit. After a crash, the OS replays or rolls back logged operations, helping restore consistent metadata and reducing corruption risk.
In Unix-like systems, which permission combination generally allows listing filenames inside a directory
A Write only
B Execute only
C Read with execute
D Read only
Note: Read permission allows listing directory entries, and execute allows entering and accessing items. Typically both are needed to list names and then access files reliably, depending on the exact operation.
Which principle reduces security risk by giving users only the minimum access needed to do their work
A Least privilege
B Full access policy
C Default admin use
D Open permissions
Note: Least privilege limits user and program permissions to what is necessary. This reduces damage from mistakes or malware by preventing unauthorized changes to system settings and sensitive files.
During boot on BIOS-based systems, which structure contains boot code and partition information at disk start
A Page table
B Swap partition
C Event log
D Master Boot Record
Note: The MBR is located in the first sector of a boot disk and contains boot code plus a partition table. If damaged, the system may fail to locate or start the OS.
In UEFI systems, which feature helps block boot-time malware by allowing only trusted boot loaders
A Disk cleanup
B File indexing
C Secure Boot
D Window snapping
Note: Secure Boot checks digital signatures of boot components. It prevents unsigned or tampered boot loaders from running, reducing risk of rootkits that load before the operating system starts.
In OS troubleshooting, why is Safe Mode often effective for fixing driver-related boot failures
A Installs new drivers
B Loads minimal drivers
C Formats system disk
D Disables file system
Note: Safe Mode starts the OS with essential drivers and services only. If a faulty driver causes boot failure, Safe Mode may bypass it, letting the user uninstall or roll back the problem driver.
Which tool is best suited to analyze long-term CPU, disk, and memory counters for bottleneck investigation
A Performance Monitor
B Disk Cleanup
C File Explorer
D Paint app
Note: Performance Monitor records detailed counters over time, such as CPU usage, disk queue length, and memory faults. It helps identify bottlenecks and trends that are not visible in quick snapshots.
Which OS log source is typically most helpful for diagnosing repeated service crashes on startup
A Desktop shortcuts
B Browser history
C Event Viewer logs
D Clipboard entries
Note: Event Viewer contains time-stamped system and application logs. Service crashes, driver failures, and boot errors appear here with codes and details, helping pinpoint the failing component.
Which Windows feature limits unknown apps from making system-wide changes without user consent
A Screen magnifier
B Disk defragment
C File attributes
D User Account Control
Note: UAC prompts when a task needs elevated privileges. It reduces silent installs and unauthorized changes by requiring confirmation or admin credentials, improving security in everyday system use.
Which OS concept allows a single physical machine to host isolated guest OS environments
A Virtualization
B Defragmentation
C File compression
D Spooling
Note: Virtualization uses a hypervisor to create virtual machines. Each VM runs its own OS in isolation, useful for testing, consolidation, and running multiple environments on one hardware platform.
Why is a Type 1 hypervisor generally preferred for enterprise servers
A Needs host OS
B Only GUI based
C Runs on bare metal
D Works offline only
Note: Type 1 hypervisors run directly on hardware, reducing overhead and improving performance and isolation. This makes them suitable for servers where reliability, efficiency, and security are important.
Which OS tool is most appropriate to manage service startup types like Automatic or Disabled
A Services console
B Disk Management
C Taskbar settings
D Photo viewer
Note: The Services console allows starting, stopping, and configuring services. Changing startup type controls whether a service begins at boot, on demand, or never, affecting performance and system features.
In multiuser systems, what does authentication confirm before granting access
A File size limit
B User identity
C Screen resolution
D CPU frequency
Note: Authentication verifies who the user is using passwords, keys, or biometrics. After identity is confirmed, authorization rules decide what resources and actions are permitted for that account.
After authentication, what does authorization mainly determine in the OS
A Boot loader type
B Disk sector size
C Monitor brightness
D Allowed permissions
Note: Authorization checks what the authenticated user is allowed to do. It enforces access control for files, folders, devices, and administrative tasks based on roles and permission settings.
Which access control model assigns permissions based on a user’s job role, like “admin” or “operator”
A Random access model
B Open access model
C Role-based access
D Single-user model
Note: Role-based access control assigns permissions to roles rather than individuals. Users inherit permissions by being assigned roles, simplifying management and improving consistency in larger organizations.
In a CLI, which feature makes repeated administration tasks efficient across many machines
A Scripting automation
B Window snapping
C Icon sorting
D Touch gestures
Note: CLI commands can be scripted and reused, allowing consistent actions like backups, user creation, and updates. Automation reduces manual errors and speeds management, especially in networked environments.
Which OS concept allows a file to be accessible through a single global namespace across a distributed system
A Local text editor
B GUI theme engine
C Screen reader
D Distributed file system
Note: Distributed file systems provide shared storage accessible from multiple machines with a unified namespace. They manage location transparency, replication, and access control so users see files as one system.
Which OS approach improves reliability by keeping copies of important data on multiple machines
A Fragmentation
B Time slicing
C Replication
D Polling
Note: Replication stores multiple copies of data across nodes. If one machine fails, another copy remains available, improving fault tolerance and availability in distributed and networked environments.
In file system design, what does “mount point” specifically represent
A Directory attachment location
B Disk sector type
C CPU scheduling rule
D User account role
Note: A mount point is a directory where a file system is attached into the directory tree. After mounting, the device’s files appear under that directory, enabling access like normal folders.
Which mechanism helps an OS avoid unnecessary CPU usage by reacting only when devices need attention
A Constant polling
B Interrupt-driven I/O
C Manual scheduling
D Screen buffering
Note: Interrupt-driven I/O allows devices to signal completion or need for service. The CPU can do other work instead of constantly checking device status, improving efficiency and responsiveness.
Which concept temporarily stores I/O data in memory to handle speed differences between CPU and devices
A Paging
B Aging
C Booting
D Buffering
Note: Buffering uses memory areas to hold data during I/O operations. It smooths differences in device speed, reduces waiting, and helps maintain continuous data flow for processes.
Which technique allows a printer to handle jobs one by one while programs continue working
A Spooling
B Paging
C Swapping
D Mirroring
Note: Spooling places print jobs in a queue on disk or memory. The printer processes jobs sequentially, while applications remain free to continue running without waiting for the printer to finish.
In process synchronization, what is a common problem when two threads update shared data without locking
A Page fault
B Cold boot
C Race condition
D Disk cleanup
Note: A race condition occurs when the result depends on timing of thread execution. Without proper locking, shared data can become inconsistent, leading to errors that are hard to reproduce and debug.
Which OS feature helps prevent unauthorized modification of system files by normal users
A File permissions
B Screen icons
C Desktop themes
D Window borders
Note: Permissions restrict who can read, write, or execute system files. By limiting write access to administrators and trusted services, the OS prevents accidental or malicious changes that could break stability.
Which file system behavior most directly helps prevent data loss by writing changes in an ordered, recoverable way
A Icon caching
B Journaling writes
C Theme loading
D Font smoothing
Note: Journaling records changes before final commit, enabling recovery after power loss or crashes. It improves file system reliability by ensuring metadata and sometimes data updates can be restored consistently.
Which OS command-line concept lets a command’s output become input to another command
A GUI shortcut
B Disk mirroring
C Driver rollback
D Piping output
Note: Piping connects commands so the output of one becomes input to another. It is powerful in CLI environments for filtering, searching, and transforming text quickly in administrative tasks.
Which OS security approach logs sensitive actions like failed logins and permission changes for investigation
A Disk caching
B Screen scaling
C Audit logging
D File preview
Note: Audit logs track security-relevant events such as login failures, access attempts, and policy changes. These records help detect attacks, investigate incidents, and meet compliance requirements in secure systems.
What is the main risk of running daily work using an administrator account on a multiuser system
A Higher malware impact
B Lower disk capacity
C Slower mouse speed
D Less screen brightness
Note: Admin accounts can modify system settings and protected files. If malware runs under admin privileges, it can cause much greater damage, so standard accounts are safer for routine tasks.
Which memory issue is most associated with segmentation because segments vary in size over time
A Internal fragmentation
B Page faults only
C TLB misses only
D External fragmentation
Note: Segmentation allocates variable-sized memory blocks. As segments are created and removed, gaps form between free blocks, producing external fragmentation where enough total space exists but not contiguously.
Which OS strategy reduces external fragmentation by compacting memory contents, but is costly
A Time slicing
B Spooling jobs
C Memory compaction
D Disk journaling
Note: Compaction moves processes in memory to combine free space into one large block. It reduces external fragmentation but costs CPU time and requires relocation support, so it is not always practical.
In paging, why does internal fragmentation occur even when external fragmentation is avoided
A Unused page space
B Disk sector gaps
C CPU cache misses
D Screen pixel waste
Note: Internal fragmentation happens because pages are fixed size. If a process does not fill the last page completely, the unused space inside that page is wasted, even though memory is allocated.
Which boot concept loads only essential OS components to recover from serious system issues
A Normal boot mode
B Recovery environment
C Fast startup mode
D Gaming mode
Note: Recovery environments provide tools like startup repair, restore, and command options. They help fix boot problems, restore system state, or recover files when normal boot fails.
Which OS tool is used to schedule maintenance tasks like weekly backups without user interaction
A Task Scheduler
B Device Manager
C Disk Cleanup
D Control Panel
Note: Task Scheduler automates running programs or scripts at specific times or events. It supports regular backups, cleanup, and maintenance, ensuring important tasks occur even when users forget.
Which OS practice best reduces downtime by testing patches before deploying them widely
A Random patching
B Immediate forced patch
C Disable all updates
D Staged patch rollout
Note: Staged rollout tests patches on limited systems first to detect issues early. After validation, updates are deployed to more machines, reducing risk of widespread failures in critical environments.
Which OS-level concept ensures that a program’s crash does not normally crash the entire system
A Disk defragment
B Screen snapping
C Process isolation
D Icon caching
Note: Process isolation separates each process’s memory and resources. If one application crashes, the OS can terminate it without affecting other processes, helping maintain overall system stability.
Which OS feature allows switching between user and kernel space safely using controlled entry points
A System call mechanism
B Desktop shortcut
C Screen magnifier
D File explorer
Note: System calls provide a safe interface for user programs to request OS services. The CPU switches to kernel mode, performs the protected operation, then returns to user mode, maintaining security and stability.