Operating System MCQ IT Officer(PSC)

 

MCQs from PAGE1

1. Out of the following, which is not an essential element of a communication system?
a. Transmitter
b. Transducer
c. Receiver
d. Communication channel
Correct Answer: b
Explanation: A communication system requires a transmitter (to send the signal), a receiver (to receive the signal), and a communication channel (to transmit the signal). A transducer converts energy from one form to another (e.g., electrical to sound), but it is not an essential element of the core communication system itself—it is often part of the transmitter or receiver. The correct answer is "b".

2. A device which provides output in electrical form or it has input in electrical form is called a?
a. Transmitter
b. Receiver
c. Repeater
d. Transducer
Correct Answer: d
Explanation: A transducer is a device that converts one form of energy to another, typically providing output in electrical form (e.g., a microphone converting sound to electrical signals) or accepting electrical input (e.g., a speaker). The correct answer is "d".

3. Decrease in signal strength due to energy losses is called?
a. Distortion
b. Interference
c. Attenuation
d. Noise
Correct Answer: c
Explanation: Attenuation refers to the reduction in signal strength as it travels through a medium due to energy losses. Distortion alters the signal shape, interference adds unwanted signals, and noise is random disturbance. The correct answer is "c".

4. The disturbance or distortion in the transmission and processing of message signals is called?
a. Noise
b. Attenuation
c. Interference
d. None of these
Correct Answer: a
Explanation: Noise is the unwanted random disturbance or distortion that affects the transmission and processing of message signals. Attenuation is signal loss, and interference is a specific type of external signal disruption. The correct answer is "a".

5. A repeater is a combination of?
a. Receiver
b. Amplifier
c. Transmitter
d. All of these
Correct Answer: d
Explanation: A repeater is a device that receives a signal (receiver), amplifies it (amplifier), and retransmits it (transmitter) to extend the range of a communication system. Thus, it combines all these components. The correct answer is "d".

6. In the case of the index allocation scheme of various blocks to a file, the maximum size (possible) of the file would depend on :
a. The total number of blocks that have been used for the index, size of all the blocks
b. The actual size of all blocks, the size of the blocks' address
c. The of the blocks' size, the blocks' address size; and the total number of blocks that have been used for the index
d. None of the above
Correct Answer: c
Explanation: In an indexed allocation scheme, the maximum file size depends on the block size (data storage capacity), the size of the block address (how many blocks can be indexed), and the total number of index blocks (limiting the number of pointers). Option c correctly encompasses these factors. The correct answer is "c".

7. The swap space in a disk is primarily used to:
a. Save process data
b. Save temporary HTML pages
c. Store the device drivers
d. Store the super-block
Correct Answer: a
Explanation: Swap space on a disk is used to temporarily hold process data when RAM is full, allowing virtual memory to function by swapping pages in and out. The correct answer is "a".

8. Out of these page replacement algorithms, which one suffers from Belady's anomaly?
a. LRU
b. FIFO
c. Both LRU and FIFO
d. Optimal Page Replacement
Correct Answer: b
Explanation: Belady's anomaly occurs when increasing the number of page frames results in more page faults, and this is characteristic of the First-In-First-Out (FIFO) page replacement algorithm. LRU and Optimal do not exhibit this anomaly. The correct answer is "b".

9. An increase in a computer's RAM leads to a typical improvement in performance because:
a. Fewer page faults occur
b. Virtual memory increases
c. Fewer segmentation faults occur
d. A larger RAM is faster
Correct Answer: a
Explanation: Increasing RAM reduces the need to use swap space, leading to fewer page faults (situations where a required page is not in memory). This improves performance. The correct answer is "a".

10. The Virtual memory is:
a. An illusion of a large main memory
b. A large main memory
c. A large secondary memory
d. None of the above
Correct Answer: a
Explanation: Virtual memory creates the illusion of a larger main memory by using disk space to extend RAM, allowing processes to use more memory than physically available. The correct answer is "a".

11. Thrashing occurs in a system when:
a. The processes on the system access pages and not memory frequently
b. A page fault pops up
c. The processes on the system are in running state
d. The processes on the system are in the waiting state
Correct Answer: a
Explanation: Thrashing occurs when the system spends excessive time swapping pages in and out due to frequent page faults, often because processes access pages excessively instead of utilizing memory efficiently. The correct answer is "a".

12. The page fault occurs whenever:
a. The requested page isn't in the memory
b. The requested page is in the memory
c. An exception is thrown
d. The page is corrupted
Correct Answer: a
Explanation: A page fault occurs when a process requests a page that is not currently in physical memory, requiring it to be fetched from disk. The correct answer is "a".

13. A system that has 32-bit virtual addresses & 1 KB page size, it is not practical to use one-level page tables for translating virtual to a physical address, due to:
a. a large amount of external fragmentation
b. a large amount of internal fragmentation
c. a large computation overhead in the process of translation
d. a large memory overhead when maintaining the page tables
Correct Answer: d
Explanation: With 32-bit virtual addresses (2³² bytes = 4 GB) and a 1 KB (2¹⁰ bytes) page size, a one-level page table would require 2²² entries (4 GB / 1 KB), each potentially 4 bytes, leading to a 16 MB table. This large memory overhead makes it impractical, favoring multi-level page tables. The correct answer is "d".

14. Which of these isn't an advantage of using dynamically linked, shared libraries, as compared to statically linked libraries?
a. Faster program startup
b. The existing programs do not need to be relinked so as to take advantage of the newer library versions
c. Lesser page fault rate in a system
d. Smaller sizes of executable files
Correct Answer: a
Explanation: Dynamically linked libraries typically result in slower program startup due to runtime linking, while offering advantages like no relinking for updates, fewer page faults (shared memory), and smaller executables. The correct answer is "a".

15. Out of all the following, which one isn't a form of memory?
a. Translation lookaside buffer
b. Instruction opcode
c. Instruction register
d. Instruction cache
Correct Answer: b
Explanation: The translation lookaside buffer (TLB), instruction register, and instruction cache are all memory-related components (cache, register, or buffer). An instruction opcode is part of an instruction set, not a form of memory. The correct answer is "b".

16. The process of dynamic linking can generate security concerns because:
a. Linking is insecure
b. The cryptographic procedures aren't available for the process of dynamic linking
c. Security is dynamic
d. The path of the searching dynamic libraries isn't known until the runtime
Correct Answer: d
Explanation: Dynamic linking poses security risks because the library paths are resolved at runtime, potentially allowing attackers to substitute malicious libraries if the search path is manipulated. The correct answer is "d".

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MCQs from PAGE2

17. ______ is the process in which load addresses are assigned to a program's various parts, and the code and date are adjusted in the program for the reflection of the assigned addresses.
a. Symbol resolution
b. Assembly
c. Parsing
d. Relocation
Correct Answer: d
Explanation: Relocation is the process of assigning load addresses to a program's parts and adjusting the code and data to reflect these addresses during loading or linking. The correct answer is "d".

18. Which one of these is NOT shared by the same process's threads?
a. Address Space
b. Stack
c. Message Queue
d. File Descriptor Table
Correct Answer: b
Explanation: Threads within the same process share the address space, file descriptor table, and message queue, but each thread has its own stack for local variables and function calls. The correct answer is "b".

19. Which of these disk scheduling policies results in minimum head movement?
a. Circular scan
b. Elevator
c. FCS
d. None of the above
Correct Answer: b
Explanation: The Elevator (or SCAN) disk scheduling policy moves the disk head in one direction, servicing requests, and then reverses, minimizing head movement by avoiding unnecessary back-and-forth motion. Circular SCAN is similar but continuous; FCS is not a standard term. The correct answer is "b".

20. In a magnetic disk that consists of concentric circular tracks, its seek latency isn't proportional linearly to the seek distance, because of:
a. The use of arm scheduling policies that are unfair
b. A higher track capacity on the platter's periphery
c. A starting and stopping inertia for arms
d. A non-uniform distribution of all the requests
Correct Answer: c
Explanation: Seek latency is not linear due to the inertia of the disk arm, which requires time to start, move, and stop, especially over longer distances. The correct answer is "c".

21. The usage of some larger block size in a file system of a fixed block size leads to:
a. A better disk space utilisation but poorer disk throughput
b. A poorer disk space utilisation and poorer disk throughput
c. A poorer disk space utilisation but better disk throughput
d. A better disk space utilisation and better disk throughput
Correct Answer: c
Explanation: Larger block sizes reduce the number of blocks, improving disk throughput (fewer seeks), but lead to poorer space utilization due to internal fragmentation (unused space within blocks). The correct answer is "c".

22. Out of the following, which one needs a device driver?
a. Main memory
b. Disk
c. Register
d. Cache
Correct Answer: b
Explanation: A device driver is required for hardware devices like disks to manage communication between the OS and the hardware. Main memory, registers, and cache are managed directly by the CPU or OS. The correct answer is "b".

23. The onboard memory of a graphics card is about 1 MB. Out of the modes mentioned below, which one does the card not support?
a. A resolution of 1600 × 400 and a 17-inch monitor with 256 colours
b. A resolution of 1600 × 400 and a 14-inch monitor with 16 million colours
c. A resolution of 800 × 400 and a 17-inch monitor with 16 million colours
d. A resolution of 800 × 800 and a 14-inch monitor with 256 colours
Correct Answer: b
Explanation: Memory requirement = resolution × colour depth. For 1 MB (2²⁰ bytes ≈ 1,048,576 bytes):

• a) 1600 × 400 × 8 bits (256 colours) = 640,000 bytes < 1 MB
• b) 1600 × 400 × 24 bits (16 million colours) = 1,920,000 bytes > 1 MB
• c) 800 × 400 × 24 bits = 960,000 bytes < 1 MB
• d) 800 × 800 × 8 bits = 640,000 bytes < 1 MB
  Option b exceeds the 1 MB limit. The correct answer is "b".

24. Out of the following interrupt handling mechanisms and DMA transfer modes, which one enables the highest bandwidth for I/O:
a. Polling interrupts and Transparent DMA
b. Vectored interrupts and Cycle-stealing
c. Vectored interrupts and Block transfer
d. Polling interrupts and Block transfer
Correct Answer: c
Explanation: Vectored interrupts allow efficient interrupt handling, and Block transfer DMA moves large data chunks without CPU intervention, maximizing I/O bandwidth. The correct answer is "c".

25. In a computer system that consists of n number of CPUs, the maximum processes that can exist in the Ready State would be:
a. Independent of n
b. 2n
c. n + 2
d. n
Correct Answer: a
Explanation: The number of processes in the Ready State depends on the OS scheduler and available resources, not directly on the number of CPUs (n), though it may be limited by memory or scheduling policy. The correct answer is "a".

26. Which of these doesn't interrupt a running process?
a. Power failure
b. Scheduler process
c. Timer
d. A device
Correct Answer: b
Explanation: Power failure, timer, and device interrupts can halt a running process, but the scheduler process manages process switching without interrupting the current process—it decides when to switch. The correct answer is "b".

27. Which of these need not be saved necessarily during context switching between various processes?
a. Translation look-aside buffer
b. General-purpose registers
c. Program counter
d. None of the above
Correct Answer: a
Explanation: During context switching, general-purpose registers and the program counter must be saved to restore the process state. The TLB (Translation Lookaside Buffer) is often flushed or not saved, as it is managed by hardware and reloaded on demand. The correct answer is "a".

28. An OS implements a policy that needs a process to release all of the resources before it makes any requests for another resource. Out of all the statements below, select the one that is TRUE:
a. Both deadlock and starvation can occur
b. Deadlock cannot occur, but starvation can occur
c. Deadlock can occur, but starvation can not occur
d. Neither deadlock nor starvation can occur
Correct Answer: b
Explanation: This policy prevents deadlock (a circular wait is impossible if resources are released first), but starvation can occur if a process is repeatedly denied resources due to other processes' demands. The correct answer is "b".

29. Multiple words are put in a single cache block for:
a. Reducing the miss penalty
b. Exploiting the reference's temporal locality in a program
c. Exploiting the reference's spatial locality in a program
d. None of the above
Correct Answer: c
Explanation: Placing multiple words in a cache block exploits spatial locality, where consecutive memory accesses are likely, reducing cache misses. The correct answer is "c".

30. The lowest number of page frames that are bound to be allocated in an environment of virtual memory to a running process is determined by:
a. The page size
b. The instruction set architecture
c. The total number of processes in memory
d. The size of the physical memory
Correct Answer: b
Explanation: The minimum number of page frames depends on the instruction set architecture (e.g., the number of registers or instructions needing memory), which dictates the process's working set. The correct answer is "b".