Input/Output Organization MCQs

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1. : What is a cache miss?
(A) When the requested data is not found in the cache and must be fetched from main memory
(B) When the requested data is found in the cache and is immediately used
(C) When data is incorrectly stored in the cache
(D) When the cache size is exceeded

2. : What occurs during a cache hit?
(A) The requested data is found in the cache and can be accessed quickly
(B) The cache must fetch the data from main memory
(C) The data is written to the cache
(D) The cache size is increased

3. : Which of the following can lead to a higher cache miss rate?
(A) Larger cache size
(B) Frequent access to data not present in the cache
(C) Improved cache associativity
(D) Larger cache line size

4. : How does increasing the cache size generally affect the cache miss rate?
(A) It typically reduces the cache miss rate
(B) It increases the cache miss rate
(C) It has no effect on the cache miss rate
(D) It increases the frequency of cache hits

5. : What is the impact of a cache hit on system performance?
(A) It improves performance by reducing the time needed to access data
(B) It degrades performance due to increased cache management overhead
(C) It has no impact on performance
(D) It causes a delay in data retrieval

6. : What typically happens when a cache miss occurs?
(A) The system must fetch the data from main memory or another lower-level cache
(B) The system writes data to the cache
(C) The system increases the cache size
(D) The cache is cleared

7. : Which factor does not influence the cache miss rate?
(A) Cache size
(B) Cache associativity
(C) Cache replacement policy
(D) CPU clock speed

8. : What is the effect of a higher cache associativity on cache performance?
(A) It generally reduces the cache miss rate
(B) It increases the cache miss rate
(C) It has no effect on cache miss rate
(D) It speeds up the CPU clock

9. : What is the primary goal of a cache replacement policy?
(A) To decide which cache line to replace when a cache miss occurs
(B) To increase the size of the cache
(C) To improve the speed of the CPU
(D) To reduce the power consumption of the cache

10. : Which of the following is a common cache replacement policy?
(A) Least Recently Used (LRU)
(B) Write-through
(C) Write-back
(D) Direct-mapped

11. : What does a high cache miss rate indicate about a system?
(A) The system may have inadequate cache size or poor cache utilization
(B) The system has optimal cache performance
(C) The cache size is too large
(D) The cache replacement policy is perfect

12. : Which cache mapping technique typically results in a higher cache miss rate?
(A) Direct-mapped
(B) Set-associative
(C) Fully associative
(D) Random

13. : What is the effect of increasing the cache line size?
(A) It can reduce the cache miss rate by fetching more contiguous data
(B) It increases the number of cache misses
(C) It has no impact on cache performance
(D) It decreases the hit rate

14. : Which of the following strategies is likely to decrease the number of cache misses?
(A) Increasing cache associativity
(B) Reducing cache size
(C) Using a direct-mapped cache
(D) Implementing a more aggressive replacement policy

15. : What is a consequence of a cache miss in a system with multiple cache levels?
(A) The system may need to fetch data from a lower-level cache or main memory
(B) The system immediately retrieves data from the cache
(C) The system increases the cache size
(D) The cache is reset

16. : Which of the following is a characteristic of a direct-mapped cache?
(A) Each block of memory maps to exactly one cache line
(B) Each block of memory can map to multiple cache lines
(C) Cache lines are chosen randomly
(D) There is no mapping between memory blocks and cache lines

17. : In which cache configuration is the likelihood of a cache miss generally the highest?
(A) Direct-mapped cache
(B) Fully associative cache
(C) Set-associative cache
(D) Multi-level cache

18. : What is the advantage of a set-associative cache over a direct-mapped cache?
(A) It reduces the likelihood of cache collisions and thus reduces the miss rate
(B) It increases the cache size
(C) It simplifies cache management
(D) It speeds up data retrieval from main memory

19. : What is a cache miss rate?
(A) The fraction of memory accesses that result in a cache miss
(B) The fraction of cache accesses that result in a hit
(C) The total number of cache lines
(D) The speed of the cache

20. : How does the cache size typically influence the cache hit rate?
(A) A larger cache size generally increases the cache hit rate
(B) A larger cache size decreases the cache hit rate
(C) Cache size does not affect the cache hit rate
(D) Cache size affects only the cache miss rate

21. : What is the primary benefit of reducing the cache miss rate?
(A) It improves overall system performance by reducing the time spent fetching data from main memory
(B) It increases the complexity of the cache design
(C) It reduces the cache size
(D) It increases the cache line size

22. : What is a “compulsory miss”?
(A) A cache miss that occurs when data is accessed for the first time
(B) A cache miss caused by a cache line eviction
(C) A cache miss due to a conflict in the cache
(D) A cache miss caused by a faulty cache line

23. : What is a “conflict miss”?
(A) A cache miss that occurs due to multiple blocks mapping to the same cache line in a direct-mapped cache
(B) A cache miss caused by a cache line eviction
(C) A cache miss due to data being accessed for the first time
(D) A cache miss caused by an invalid cache entry

24. : What is a “capacity miss”?
(A) A cache miss that occurs when the cache cannot hold all the blocks needed for a program’s execution
(B) A cache miss caused by a conflict in the cache
(C) A cache miss due to the data being accessed for the first time
(D) A cache miss caused by a faulty cache line

25. : What strategy can help reduce the impact of compulsory misses?
(A) Implementing a prefetching mechanism to load data into the cache before it is requested
(B) Increasing cache size
(C) Increasing cache associativity
(D) Using a more aggressive replacement policy

26. : Which cache replacement policy would help reduce the number of conflict misses?
(A) Least Recently Used (LRU)
(B) First In, First Out (FIFO)
(C) Random Replacement
(D) Write-back

27. : What is the effect of a larger cache line size on cache misses?
(A) It can reduce the number of compulsory and capacity misses by fetching more contiguous data
(B) It increases the frequency of conflict misses
(C) It has no effect on cache miss rate
(D) It reduces the overall cache size

28. : Which type of cache miss is least affected by increasing cache size?
(A) Conflict miss
(B) Compulsory miss
(C) Capacity miss
(D) All types are equally affected

29. : What is a primary benefit of increasing the cache associativity in terms of cache misses?
(A) It reduces conflict misses by allowing multiple blocks to map to the same cache line
(B) It increases compulsory misses
(C) It has no effect on cache misses
(D) It increases the number of capacity misses

30. : In which scenario is a “write-allocate” policy most useful?
(A) When a cache miss occurs on a write operation and the cache line is loaded from main memory
(B) When data is written directly to the main memory without affecting the cache
(C) When data is only read from the cache
(D) When the cache is being cleared

31. : What is the effect of cache line replacement on cache misses?
(A) It can potentially increase the number of conflict misses if the replaced line is frequently accessed
(B) It decreases the number of cache misses
(C) It has no impact on cache misses
(D) It automatically reduces cache size

32. : How does a larger cache typically impact the time taken to resolve a cache miss?
(A) It can reduce the time taken to resolve a miss by increasing the likelihood of data being present in the cache
(B) It increases the time taken to resolve a miss
(C) It has no effect on the time taken to resolve a miss
(D) It speeds up data retrieval from main memory

33. : What is the impact of cache hit latency on overall system performance?
(A) Lower hit latency improves system performance by reducing the time needed to access data from the cache
(B) Higher hit latency improves system performance
(C) Cache hit latency does not affect system performance
(D) It increases the number of cache misses

34. : How does a cache’s replacement policy affect cache hit rate?
(A) It can influence the likelihood of retaining frequently accessed data, thereby affecting the hit rate
(B) It has no impact on the cache hit rate
(C) It only affects cache miss rate
(D) It reduces cache hit rate by increasing replacement frequency

35. : What is a common cause of a “cold miss” or “compulsory miss”?
(A) Accessing data for the first time that has not been previously loaded into the cache
(B) Accessing data that is not in the cache due to replacement
(C) Accessing data that was recently written to the cache
(D) Accessing data that was evicted due to cache size limitations

36. : What role does prefetching play in cache performance?
(A) It helps reduce cache misses by loading data into the cache before it is requested
(B) It increases the number of cache misses
(C) It clears the cache periodically
(D) It changes the cache replacement policy

37. : How does a “write-around” policy affect cache misses compared to a “write-allocate” policy?
(A) Write-around can increase cache misses on write operations by not loading the data into the cache
(B) Write-allocate policy reduces cache misses on write operations by loading data into the cache
(C) Write-around policy increases cache hits by keeping data out of the cache
(D) Both policies have no impact on cache misses

38. : Which type of cache miss is less frequent in a well-designed caching system?
(A) Capacity miss
(B) Compulsory miss
(C) Conflict miss
(D) All types are equally frequent

39. : What is the primary purpose of a cache?
(A) To speed up data access by storing frequently used data closer to the CPU
(B) To increase the size of the main memory
(C) To reduce the overall power consumption of the system
(D) To replace main memory entirely

40. : How can increasing the number of cache sets in a set-associative cache impact cache performance?
(A) It can reduce the number of conflict misses by allowing more flexibility in data mapping
(B) It increases the likelihood of cache misses
(C) It has no effect on cache performance
(D) It decreases the cache size

41. : What is the main benefit of using a fully associative cache compared to a direct-mapped cache?
(A) It reduces the number of conflict misses by allowing any block to be placed in any cache line
(B) It simplifies cache management
(C) It reduces the cache size
(D) It increases the number of compulsory misses

42. : How does a direct-mapped cache handle cache line replacement?
(A) It replaces the cache line corresponding to a specific index when a new block maps to that index
(B) It randomly selects a cache line to replace
(C) It replaces the least recently used cache line
(D) It replaces the cache line with the most recent access

43. : What impact does a high number of cache sets have on cache performance in a set-associative cache?
(A) It generally reduces the number of conflict misses and improves performance
(B) It increases the number of conflict misses
(C) It has no effect on cache performance
(D) It decreases cache size

44. : Which of the following is most likely to improve cache performance for sequential access patterns?
(A) Increasing cache line size
(B) Reducing cache size
(C) Decreasing cache associativity
(D) Using a direct-mapped cache

45. : How does the cache line size impact the handling of spatial locality?
(A) Larger cache lines can better exploit spatial locality by fetching contiguous data in one operation
(B) Smaller cache lines are better for spatial locality
(C) Cache line size does not affect spatial locality
(D) Larger cache lines decrease the effectiveness of spatial locality

46. : What is a “miss rate” in the context of cache performance?
(A) The percentage of memory accesses that result in a cache miss
(B) The percentage of cache accesses that result in a hit
(C) The total number of cache lines
(D) The speed at which data is accessed from the cache

47. : What factor is least likely to affect cache hit rate?
(A) Cache size
(B) Cache associativity
(C) Cache line size
(D) CPU temperature

48. : What is the most effective way to reduce the number of capacity misses?
(A) Increasing the cache size to accommodate more data
(B) Reducing cache line size
(C) Increasing the associativity of the cache
(D) Using a write-back policy

49. : How does the use of prefetching affect cache miss rates?
(A) It can reduce cache miss rates by loading data into the cache before it is accessed
(B) It increases cache miss rates
(C) It has no impact on cache miss rates
(D) It causes data to be discarded from the cache

50. : What type of cache miss occurs when a program accesses data for the first time?
(A) Compulsory miss
(B) Capacity miss
(C) Conflict miss
(D) Coherence miss

51. : Which type of I/O operation involves the CPU being actively involved in the transfer process?
(A) Programmed I/O
(B) Direct Memory Access (DMA)
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

52. : What is Direct Memory Access (DMA) used for in I/O operations?
(A) To allow peripheral devices to access memory directly without CPU intervention
(B) To convert analog signals to digital
(C) To manage CPU cache
(D) To handle arithmetic operations

53. : In the context of I/O operations, what does “polling” refer to?
(A) The CPU repeatedly checks the status of an I/O device to determine if it is ready for data transfer
(B) A method for converting digital data to analog
(C) The process of buffering data
(D) The execution of I/O commands by DMA

54. : Which I/O method allows the CPU to be interrupted when an I/O device needs attention?
(A) Interrupt-driven I/O
(B) Programmed I/O
(C) Direct Memory Access (DMA)
(D) Memory-mapped I/O

55. : What is the main advantage of using Direct Memory Access (DMA) over programmed I/O?
(A) DMA reduces CPU involvement in data transfer, allowing for more efficient processing
(B) DMA requires more CPU cycles for data transfer
(C) DMA increases the number of interrupts required
(D) DMA simplifies the buffer management process

56. : Which of the following describes memory-mapped I/O?
(A) I/O devices are accessed using the same address space as memory
(B) I/O devices are accessed through separate I/O instructions
(C) I/O operations are handled through interrupt signals
(D) I/O devices are directly connected to the CPU’s registers

57. : What is an interrupt vector?
(A) A table used to manage and handle interrupts in a computer system
(B) A type of I/O buffer
(C) A hardware component for converting digital signals
(D) A method for direct memory access

58. : Which I/O technique involves the use of interrupts to signal the CPU that an I/O operation is complete?
(A) Interrupt-driven I/O
(B) Programmed I/O
(C) Direct Memory Access (DMA)
(D) Memory-mapped I/O

59. : What is the function of a device driver in an I/O system?
(A) To provide a software interface between the operating system and hardware devices
(B) To directly access memory locations
(C) To manage CPU registers
(D) To convert analog signals to digital

60. : Which of the following is a characteristic of programmed I/O?
(A) The CPU directly controls data transfer operations and waits for I/O operations to complete
(B) I/O devices access memory directly without CPU intervention
(C) The CPU is interrupted for every I/O operation
(D) Data transfer is managed by DMA controllers

61. : How does an interrupt improve system efficiency during I/O operations?
(A) It allows the CPU to perform other tasks while waiting for I/O operations to complete
(B) It increases the time required for data transfer
(C) It directly accesses memory without the need for CPU intervention
(D) It reduces the need for buffering data

62. : What is the primary purpose of an I/O controller?
(A) To manage communication between the CPU and peripheral devices
(B) To perform arithmetic operations
(C) To handle data storage
(D) To execute software instructions

63. : Which I/O technique is characterized by the CPU issuing commands to the I/O device and waiting for the device to complete the operation?
(A) Programmed I/O
(B) Direct Memory Access (DMA)
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

64. : What role does the system bus play in I/O operations?
(A) It facilitates data transfer between the CPU, memory, and I/O devices
(B) It directly controls the execution of instructions
(C) It manages memory allocation
(D) It converts digital signals to analog

65. : In an interrupt-driven I/O system, what happens when an interrupt occurs?
(A) The CPU stops its current task and executes an interrupt service routine to handle the I/O operation
(B) The I/O device immediately writes data to memory
(C) The CPU continues its current task without interruption
(D) The I/O device requests additional data from the CPU

66. : What is the purpose of an I/O port in a computer system?
(A) To provide a physical or logical interface for connecting I/O devices to the system
(B) To store data temporarily
(C) To execute computational tasks
(D) To convert analog signals to digital

67. : Which I/O method allows devices to be mapped into the address space of the CPU, allowing for direct memory access?
(A) Memory-mapped I/O
(B) Programmed I/O
(C) Interrupt-driven I/O
(D) Direct Memory Access (DMA)

68. : What does a “buffer overflow” error indicate?
(A) Data exceeds the capacity of the buffer, leading to potential data loss or corruption
(B) The buffer is empty and no data is available
(C) The buffer is full and cannot accept additional data
(D) Data is incorrectly formatted for the buffer

69. : What is the primary function of a bus controller in an I/O system?
(A) To manage and control the flow of data on the system bus
(B) To execute data transfer commands from the CPU
(C) To perform arithmetic operations
(D) To convert digital signals

70. : How does an I/O operation affect CPU performance in a programmatic I/O environment?
(A) The CPU must wait for I/O operations to complete, potentially reducing overall performance
(B) I/O operations have no effect on CPU performance
(C) The CPU executes I/O operations concurrently with other tasks
(D) I/O operations speed up CPU performance

71. : What is the purpose of an interrupt service routine (ISR)?
(A) To handle specific tasks related to interrupts and I/O operations
(B) To manage memory allocation
(C) To perform arithmetic calculations
(D) To execute data transfer commands

72. : In which situation is Direct Memory Access (DMA) most beneficial?
(A) When large amounts of data need to be transferred between I/O devices and memory without CPU involvement
(B) When minimal data transfer is required
(C) When the CPU must be directly involved in every data transfer operation
(D) When I/O operations are infrequent

73. : What is a key characteristic of an interrupt-driven I/O system?
(A) The CPU is notified via interrupts when an I/O device needs attention
(B) The CPU must poll the device constantly to check for data readiness
(C) Data is transferred directly to memory without CPU intervention
(D) The I/O device directly accesses CPU registers

74. : Which component is responsible for translating I/O requests into electrical signals that can be understood by the device?
(A) I/O controller
(B) Memory unit
(C) CPU
(D) System bus

75. : What does the term “polling” imply in the context of I/O systems?
(A) The CPU regularly checks the status of an I/O device to determine if it is ready for data transfer
(B) The CPU interrupts the device to request data
(C) The device directly accesses memory
(D) The system automatically buffers incoming data

76. : How does an I/O device use interrupts to signal the CPU?
(A) The device sends an interrupt signal to the CPU, which pauses its current task to handle the I/O operation
(B) The device writes data directly to memory without involving the CPU
(C) The CPU continuously polls the device to check for status changes
(D) The device initiates DMA operations

77. : What is the primary advantage of using DMA over interrupt-driven I/O?
(A) DMA allows for more efficient data transfer without constant CPU intervention
(B) DMA requires more CPU cycles to manage I/O operations
(C) DMA increases the number of interrupts required
(D) DMA simplifies the buffer management process

78. : What is an example of an I/O device that typically uses direct memory access (DMA)?
(A) Disk drives
(B) Keyboards
(C) Mice
(D) Printers

79. : In which I/O method does the CPU perform read and write operations directly to and from the I/O device?
(A) Programmed I/O
(B) Direct Memory Access (DMA)
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

80. : What does a “hardware interrupt” refer to?
(A) A signal generated by hardware to alert the CPU to an event that needs immediate attention
(B) A software command that suspends current operations
(C) A method for managing memory allocation
(D) A type of data conversion process

81. : Which I/O technique involves the CPU waiting for an I/O operation to complete before continuing with other tasks?
(A) Programmed I/O
(B) Interrupt-driven I/O
(C) Direct Memory Access (DMA)
(D) Memory-mapped I/O

82. : How does a memory-mapped I/O system simplify the communication between the CPU and I/O devices?
(A) By using the same address space for both memory and I/O devices, simplifying access
(B) By isolating I/O operations from memory operations
(C) By using dedicated I/O instructions
(D) By directly accessing CPU registers

83. : What is the function of an I/O bus in a computer system?
(A) To provide a communication pathway between the CPU, memory, and I/O devices
(B) To manage data storage
(C) To execute arithmetic calculations
(D) To control the operating system

84. : What does the term “buffering” refer to in I/O operations?
(A) The temporary storage of data to accommodate differences in processing speeds between I/O devices and the CPU
(B) The process of executing I/O commands
(C) The management of CPU registers
(D) The conversion of analog signals

85. : How does interrupt-driven I/O differ from programmed I/O in terms of CPU involvement?
(A) Interrupt-driven I/O allows the CPU to handle other tasks while waiting for I/O operations, whereas programmed I/O requires the CPU to wait for completion
(B) Programmed I/O requires less CPU involvement
(C) Both methods involve the CPU handling I/O operations concurrently
(D) Interrupt-driven I/O increases CPU cycles for data transfer

86. : What is the main disadvantage of programmed I/O?
(A) It can be inefficient because the CPU is occupied with I/O operations, reducing overall performance
(B) It requires more complex hardware compared to other methods
(C) It reduces the number of interrupts generated
(D) It increases the efficiency of data transfer

87. : What does an I/O controller manage in a computer system?
(A) The communication between the CPU and I/O devices
(B) The execution of software programs
(C) The management of CPU cache
(D) The conversion of data signals

88. : What is the role of an interrupt handler in an interrupt-driven I/O system?
(A) To process and manage interrupts and execute appropriate actions
(B) To handle data storage
(C) To convert digital signals to analog
(D) To execute arithmetic operations

89. : In which type of I/O system does the CPU perform data transfers directly between memory and the I/O device?
(A) Programmed I/O
(B) Direct Memory Access (DMA)
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

90. : What is the main advantage of using a DMA controller?
(A) It allows for efficient data transfer without requiring constant CPU intervention
(B) It simplifies the buffering process
(C) It reduces the number of interrupts required
(D) It handles arithmetic calculations

91. : What does “memory-mapped I/O” mean in terms of accessing I/O devices?
(A) I/O devices are accessed through the same memory address space as regular memory
(B) I/O devices are accessed through dedicated I/O instructions
(C) I/O devices are accessed using separate data buses
(D) I/O devices require manual data conversion

92. : What is the impact of buffering on I/O performance?
(A) Buffering can improve performance by accommodating differences in processing speeds and reducing I/O wait times
(B) Buffering decreases the overall system performance
(C) Buffering has no impact on I/O performance
(D) Buffering increases the number of interrupts generated

93. : How does an I/O bus improve the efficiency of I/O operations?
(A) By providing a standardized pathway for data transfer between the CPU, memory, and I/O devices
(B) By isolating I/O operations from memory access
(C) By directly managing I/O device interrupts
(D) By simplifying the data conversion process

94. : What role does a system interrupt play in I/O operations?
(A) It signals the CPU to stop its current task and handle an I/O request
(B) It manages the data transfer between memory and I/O devices
(C) It converts analog signals to digital
(D) It executes arithmetic operations

95. : Which of the following is a characteristic of Direct Memory Access (DMA) operations?
(A) DMA allows for high-speed data transfer with minimal CPU involvement
(B) DMA requires the CPU to manage every data transfer operation
(C) DMA increases the number of interrupts required
(D) DMA involves constant CPU polling of I/O devices

96. : What is the main function of an I/O port?
(A) To provide an interface for connecting and communicating with I/O devices
(B) To manage the CPU’s execution of instructions
(C) To store data permanently
(D) To convert digital data to analog

97. : Which type of I/O system is characterized by the CPU issuing I/O commands and directly managing data transfer operations?
(A) Programmed I/O
(B) Direct Memory Access (DMA)
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

98. : How does the use of interrupts benefit the handling of I/O operations?
(A) It allows the CPU to perform other tasks while waiting for I/O operations to complete
(B) It requires the CPU to actively manage every I/O operation
(C) It simplifies the buffering process
(D) It decreases the efficiency of data transfer

99. : What is the purpose of an interrupt vector table in an I/O system?
(A) To map interrupt requests to the corresponding interrupt service routines
(B) To manage data buffers
(C) To execute memory operations
(D) To convert data signals

100. : Which component is responsible for generating interrupts in an I/O system?
(A) I/O devices
(B) The CPU
(C) Memory units
(D) The system bus

Input/Output Organization MCQs
By: Prof. Dr. Fazal Rehman | Last updated: June 23, 2025

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