B CompE Bachelor of Computer Engineering Bachelor of Computer Engineering Operating System 4 — Questions and Answers
Question 1: Which synchronization construct guarantees that only one thread executes a protected block at a time and automatically releases on exit, including via exceptions?
- Counting semaphore
- Spinlock
- Monitor (Correct answer)
- Barrier
Correct answer: Monitor
A monitor encapsulates shared data with mutual exclusion and condition variables, automatically releasing the lock when the thread exits the protected procedure.
Question 2: In the Banker's Algorithm for deadlock avoidance, what does the 'safe state' guarantee?
- No process is currently waiting
- There exists a sequence in which every process can obtain its maximum resources and finish (Correct answer)
- All resources are allocated optimally
- No circular wait can form
Correct answer: There exists a sequence in which every process can obtain its maximum resources and finish
A safe state means the OS can find an ordering (safe sequence) of processes such that each can run to completion using currently available and released resources.
Question 3: What is the role of the 'inode' in Unix/Linux file systems?
- Store the file's actual data blocks
- Hold metadata (permissions, size, block pointers) about a file (Correct answer)
- Map file names to directory entries
- Cache recently accessed file content
Correct answer: Hold metadata (permissions, size, block pointers) about a file
An inode stores file metadata including owner, permissions, timestamps, size, and pointers to data blocks, but not the file name itself.
Question 4: Which CPU scheduling algorithm can lead to indefinite postponement (starvation) of long jobs in favor of shorter ones?
- Round Robin
- FCFS
- SJF (non-preemptive)
- Priority Scheduling (Correct answer)
Correct answer: Priority Scheduling
Priority Scheduling may indefinitely delay low-priority processes if higher-priority processes keep arriving; aging is the standard mitigation.
Question 5: What distinguishes a 'thread' from a 'process' in modern operating systems?
- Threads have separate address spaces; processes share one
- Threads share the address space of their process; processes have independent address spaces (Correct answer)
- Threads cannot communicate; processes use pipes
- Threads require separate page tables
Correct answer: Threads share the address space of their process; processes have independent address spaces
Threads within the same process share code, data, and open file descriptors but have individual stacks and register sets, making context switching cheaper.
Question 6: In memory management, what is 'internal fragmentation'?
- Unused memory between allocated segments
- Wasted space within an allocated block due to fixed partition size (Correct answer)
- Memory lost to page table overhead
- Fragmentation caused by disk seeks
Correct answer: Wasted space within an allocated block due to fixed partition size
Internal fragmentation occurs when a process is allocated more memory than it requested (e.g., due to fixed partition or page size), leaving unused bytes inside the allocated region.
Question 7: Which system call in Linux changes the priority (nice value) of a running process?
- setpriority()
- renice()
- nice() (Correct answer)
- sched_setparam()
Correct answer: nice()
nice() adjusts the scheduling priority of the calling process by adding an increment to its current nice value, affecting how much CPU time it receives.
B CompE Bachelor of Computer Engineering Bachelor of Computer Engineering Operating System 4
Which synchronization construct guarantees that only one thread executes a protected block at a time and automatically releases on exit, including via exceptions?