OS Concepts — Practice MCQs for CCAT

Correct Answer: C — Priority Scheduling

Priority Scheduling can cause starvation - solved using aging.

Correct Answer: C — LRU

LRU (Least Recently Used) is a page replacement algorithm, not CPU scheduling.

Correct Answer: B — All four conditions hold simultaneously

Deadlock needs: Mutual Exclusion, Hold & Wait, No Preemption, Circular Wait.

Correct Answer: B — Deadlock avoidance

Banker's algorithm avoids deadlock by checking safe states.

Correct Answer: B — Process synchronization

Semaphores synchronize concurrent processes to avoid race conditions.

Correct Answer: B — Page is not in memory

Page fault occurs when a required page is not in main memory.

Correct Answer: B — Excessive paging activity

Thrashing: system spends more time paging than executing.

Correct Answer: B — Disk as extension of RAM

Virtual memory uses disk space to extend available memory.

Correct Answer: B — Saving and loading process states

Context switch saves current process state and loads another.

Correct Answer: B — I/O or event

Blocked process waits for I/O completion or an event.

Correct Answer: B — Mutex is binary, Semaphore can have count

Mutex is binary (locked/unlocked), Semaphore can have count > 1 for multiple resources.

Correct Answer: B — Replaces oldest page

FIFO replaces the oldest page in memory (first in, first out).

Correct Answer: B — Least recently used page

LRU replaces the page that has not been used for the longest time.

Correct Answer: A — Paging

Internal fragmentation occurs in paging when allocated memory is larger than needed.

Correct Answer: B — Variable/dynamic partitioning

External fragmentation occurs in variable partitioning when free memory is scattered.

Correct Answer: C — FIFO

Belady's anomaly: FIFO may have more page faults with more frames.

Correct Answer: B — Kernel has full access, User restricted

Kernel mode has full hardware access; User mode is restricted for protection.

Correct Answer: B — Request OS services

System calls are the interface between user programs and operating system services.

Correct Answer: B — Semaphores for synchronization

Producer-Consumer uses semaphores (empty, full, mutex) for proper synchronization.

Correct Answer: B — Response time and context switches

Smaller quantum = better response time but more context switches; larger = opposite.