I/O Techniques (Polling, Interrupts, DMA) MCQs

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1. : What is the primary function of an I/O subsystem in a computer system?
(A) To manage the communication between the CPU and peripheral devices
(B) To execute instructions from memory
(C) To store data temporarily
(D) To perform arithmetic calculations

2. : Which component is responsible for converting digital signals into analog signals for output devices?
(A) Digital-to-Analog Converter (DAC)
(B) Analog-to-Digital Converter (ADC)
(C) Central Processing Unit (CPU)
(D) Memory Unit

3. : What is the purpose of a buffer in I/O operations?
(A) To temporarily hold data during transfer between devices and memory
(B) To permanently store data
(C) To execute I/O commands
(D) To manage the CPU’s registers

4. : 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

5. : 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

6. : 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

7. : 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

8. : 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

9. : 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

10. : 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

11. : 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

12. : 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

13. : 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

14. : 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

15. : 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

16. : 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

17. : 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

18. : 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

19. : 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

20. : 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)

21. : 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

22. : 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

23. : 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

24. : 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

25. : 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

26. : 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

27. : 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

28. : 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

29. : 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

30. : 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

31. : 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

32. : 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

33. : 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

34. : 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

35. : 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

36. : 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

37. : 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

38. : 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

39. : 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

40. : 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

41. : 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

42. : 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

43. : 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

44. : 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

45. : 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

46. : 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

47. : 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

48. : What is the primary function of polling in I/O systems?
(A) The CPU repeatedly checks the status of an I/O device to determine if it is ready for data transfer
(B) The I/O device sends an interrupt to the CPU
(C) Data is directly transferred between memory and I/O devices
(D) The system automatically handles data buffering

49. : How does interrupt-driven I/O differ from polling?
(A) Interrupt-driven I/O allows the CPU to perform other tasks while waiting for I/O operations, while polling requires the CPU to continuously check the device
(B) Polling is more efficient than interrupt-driven I/O
(C) Interrupt-driven I/O involves the CPU checking the device status regularly
(D) Polling allows for more efficient data transfer

50. : Which technique allows peripherals to transfer data directly to memory, bypassing the CPU?
(A) Direct Memory Access (DMA)
(B) Programmed I/O
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

51. : What is the main advantage of using Direct Memory Access (DMA) over interrupt-driven I/O?
(A) DMA reduces CPU involvement by allowing peripherals to handle data transfer directly
(B) DMA increases the number of interrupts generated
(C) DMA requires more CPU cycles for managing I/O operations
(D) DMA involves constant polling of I/O devices

52. : In which scenario is polling typically used?
(A) When the CPU needs to repeatedly check the status of an I/O device
(B) When the CPU waits for an interrupt signal from an I/O device
(C) When data is directly transferred between I/O devices and memory
(D) When the I/O device handles data transfer independently

53. : What does an interrupt signal do in an interrupt-driven I/O system?
(A) It informs the CPU that an I/O operation requires attention, causing the CPU to stop its current task
(B) It directly transfers data between memory and I/O devices
(C) It manages the CPU’s arithmetic operations
(D) It increases the system’s polling rate

54. : Which I/O technique minimizes CPU involvement by allowing peripherals to control data transfers directly?
(A) Direct Memory Access (DMA)
(B) Programmed I/O
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

55. : What is the role of an interrupt handler in an interrupt-driven I/O system?
(A) To process the interrupt request and execute the corresponding service routine
(B) To perform direct memory access operations
(C) To continuously poll the I/O device
(D) To manage data buffering

56. : How does programmed I/O operate in terms of CPU involvement?
(A) The CPU directly manages data transfer operations and waits for their completion
(B) The CPU uses DMA to transfer data
(C) The CPU relies on interrupts to manage I/O operations
(D) The CPU accesses I/O devices through memory-mapped I/O

57. : What is the main disadvantage of using polling as an I/O technique?
(A) It can be inefficient because the CPU is continuously occupied with checking the status of the I/O device
(B) It requires more complex hardware compared to other methods
(C) It reduces the system’s throughput
(D) It involves more frequent interrupts

58. : What does an interrupt vector table do in an I/O system?
(A) It maps interrupt requests to their corresponding interrupt service routines
(B) It manages the CPU’s arithmetic operations
(C) It performs data conversions
(D) It handles direct memory access operations

59. : How does interrupt-driven I/O improve efficiency compared to programmed I/O?
(A) By allowing the CPU to perform other tasks while waiting for I/O operations to complete
(B) By requiring more CPU cycles for managing I/O operations
(C) By increasing the number of interrupts required
(D) By directly handling memory-mapped I/O

60. : What is the benefit of using interrupts in I/O systems?
(A) Interrupts allow the CPU to handle I/O requests asynchronously, improving overall system efficiency
(B) Interrupts require constant CPU polling
(C) Interrupts simplify data buffering
(D) Interrupts increase the CPU’s involvement in I/O operations

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

62. : What is a key feature of Direct Memory Access (DMA) operations?
(A) DMA allows peripherals to transfer data directly to and from memory, bypassing the CPU
(B) DMA requires more frequent interrupts
(C) DMA increases the CPU’s workload
(D) DMA involves continuous polling of I/O devices

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

64. : What is the impact of using DMA on CPU performance?
(A) DMA improves CPU performance by offloading data transfer tasks to the DMA controller
(B) DMA increases the CPU’s involvement in data transfers
(C) DMA reduces the number of interrupts generated
(D) DMA requires constant polling by the CPU

65. : What does the term “programmed I/O” refer to in I/O operations?
(A) A method where the CPU directly manages data transfer operations and waits for their completion
(B) A method where DMA handles data transfers
(C) A method where I/O devices send interrupts to the CPU
(D) A method where data is accessed through memory-mapped I/O

66. : What is the role of a buffer in I/O systems?
(A) To temporarily store data to manage differences in processing speeds between the CPU and I/O devices
(B) To convert data signals
(C) To manage CPU registers
(D) To handle arithmetic calculations

67. : Which I/O technique involves the CPU being interrupted by an I/O device when it needs attention?
(A) Interrupt-driven I/O
(B) Programmed I/O
(C) Direct Memory Access (DMA)
(D) Memory-mapped I/O

68. : What is the benefit of using polling for I/O operations in specific scenarios?
(A) Polling can be useful when I/O devices have predictable and infrequent data transfer needs
(B) Polling increases the efficiency of data transfer
(C) Polling reduces the number of interrupts generated
(D) Polling minimizes the CPU’s involvement in I/O operations

69. : What is the primary advantage of using Direct Memory Access (DMA) for data transfers?
(A) It reduces the amount of CPU intervention needed during data transfers
(B) It simplifies the use of memory-mapped I/O
(C) It increases the CPU’s workload
(D) It requires continuous polling of the I/O device

70. : What does an interrupt service routine (ISR) do when an interrupt occurs?
(A) It processes the interrupt request and performs the necessary operations to handle it
(B) It performs direct memory access operations
(C) It continuously checks the status of I/O devices
(D) It directly manages data buffers

71. : Which I/O technique allows the CPU to remain inactive while waiting for data transfer to complete?
(A) Interrupt-driven I/O
(B) Programmed I/O
(C) Direct Memory Access (DMA)
(D) Memory-mapped I/O

72. : What is the main disadvantage of using DMA in a system?
(A) It can be complex to manage and requires additional hardware support
(B) It reduces the number of interrupts generated
(C) It increases the CPU’s workload
(D) It involves continuous polling of I/O devices

73. : In which I/O technique does the CPU actively manage the status of the I/O device?
(A) Programmed I/O
(B) Direct Memory Access (DMA)
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

74. : What is the benefit of using memory-mapped I/O for device communication?
(A) It allows devices to be accessed using the same address space as memory, simplifying the programming model
(B) It increases the number of interrupts generated
(C) It requires separate I/O instructions
(D) It minimizes the use of buffers

75. : How does Direct Memory Access (DMA) improve data transfer efficiency?
(A) By enabling high-speed data transfers with minimal CPU intervention
(B) By requiring more frequent interrupts
(C) By increasing the CPU’s involvement in data transfers
(D) By simplifying programmed I/O operations

76. : Which I/O method allows for asynchronous handling of I/O operations?
(A) Interrupt-driven I/O
(B) Programmed I/O
(C) Direct Memory Access (DMA)
(D) Memory-mapped I/O

77. : What does the term “DMA controller” refer to in an I/O system?
(A) A component that manages direct memory access operations, handling data transfers between memory and peripherals
(B) A component that generates interrupts for I/O devices
(C) A component that performs arithmetic calculations
(D) A component that manages I/O buffers

78. : What is the primary role of polling in I/O management?
(A) To check the status of I/O devices at regular intervals and determine when they are ready for data transfer
(B) To handle interrupts from I/O devices
(C) To perform direct memory access operations
(D) To manage data buffering

79. : How does the CPU handle I/O operations in a programmed I/O system?
(A) The CPU directly controls data transfers and waits for the completion of each operation
(B) The CPU delegates data transfers to a DMA controller
(C) The CPU waits for interrupts from I/O devices
(D) The CPU accesses I/O devices through memory-mapped I/O

80. : What is a key benefit of using interrupts in I/O systems?
(A) Interrupts allow the CPU to handle I/O operations asynchronously, freeing up CPU time for other tasks
(B) Interrupts increase the complexity of I/O management
(C) Interrupts require more frequent polling of devices
(D) Interrupts simplify direct memory access operations

81. : Which method involves the CPU checking the status of an I/O device before proceeding with data transfer?
(A) Polling
(B) Interrupt-driven I/O
(C) Direct Memory Access (DMA)
(D) Memory-mapped I/O

82. : What is the primary purpose of an interrupt vector table?
(A) To map interrupt requests to their corresponding interrupt service routines
(B) To manage direct memory access operations
(C) To handle programmed I/O operations
(D) To perform data conversions

83. : How does Direct Memory Access (DMA) benefit system performance?
(A) By reducing the CPU’s workload and enabling faster data transfers
(B) By increasing the number of interrupts required
(C) By simplifying programmed I/O operations
(D) By requiring constant CPU polling of I/O devices

84. : What is a key feature of interrupt-driven I/O systems?
(A) The CPU is notified by an interrupt when an I/O operation requires attention
(B) The CPU continuously checks the status of I/O devices
(C) Data transfers are managed directly by memory
(D) The system uses DMA for data transfers

85. : Which I/O technique minimizes CPU involvement by allowing peripherals to handle data transfers?
(A) Direct Memory Access (DMA)
(B) Programmed I/O
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

86. : What is the main advantage of programmed I/O?
(A) It allows direct control of data transfers by the CPU
(B) It requires minimal CPU intervention
(C) It simplifies the use of memory-mapped I/O
(D) It reduces the number of interrupts

87. : How does polling affect CPU performance?
(A) Polling can reduce performance by occupying the CPU with frequent status checks
(B) Polling improves performance by reducing the need for interrupts
(C) Polling simplifies direct memory access operations
(D) Polling reduces data buffering requirements

88. : What is the key advantage of using interrupt-driven I/O compared to polling?
(A) Interrupt-driven I/O allows the CPU to perform other tasks while waiting for I/O operations to complete
(B) Interrupt-driven I/O requires more CPU cycles for managing I/O operations
(C) Interrupt-driven I/O simplifies programmed I/O operations
(D) Interrupt-driven I/O minimizes the use of buffers

89. : What does a DMA controller do?
(A) It manages data transfers between memory and peripherals, reducing CPU intervention
(B) It generates interrupts for I/O operations
(C) It directly manages data buffering
(D) It performs arithmetic calculations

90. : In which I/O method does the CPU handle data transfers directly and wait for completion?
(A) Programmed I/O
(B) Direct Memory Access (DMA)
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

91. : What is the benefit of using DMA in data transfer operations?
(A) It enables faster data transfers with minimal CPU involvement
(B) It increases the number of interrupts generated
(C) It simplifies interrupt-driven I/O
(D) It requires more frequent polling of devices

92. : What is the main disadvantage of interrupt-driven I/O systems?
(A) They can increase the complexity of handling multiple interrupts
(B) They require less CPU intervention compared to programmed I/O
(C) They reduce system performance by increasing polling frequency
(D) They simplify direct memory access operations

93. : How does memory-mapped I/O simplify device access?
(A) By using the same address space as memory for device communication
(B) By requiring separate I/O instructions
(C) By increasing the number of interrupts required
(D) By managing data buffers directly

94. : What does an interrupt-driven I/O system rely on to handle I/O operations efficiently?
(A) The use of interrupts to notify the CPU of I/O operations needing attention
(B) Continuous polling of I/O devices
(C) Direct Memory Access (DMA) for data transfers
(D) Memory-mapped I/O for device communication

95. : Which I/O technique is characterized by the CPU waiting for each I/O operation to complete before continuing?
(A) Programmed I/O
(B) Direct Memory Access (DMA)
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

96. : What is the role of polling in I/O systems?
(A) To periodically check the status of I/O devices and determine when they are ready for data transfer
(B) To handle direct memory access operations
(C) To process interrupts from I/O devices
(D) To manage data buffering

97. : How does Direct Memory Access (DMA) benefit system performance?
(A) By enabling efficient data transfers with minimal CPU involvement
(B) By increasing the number of interrupts required
(C) By requiring constant polling of I/O devices
(D) By simplifying programmed I/O operations

98. : What does an interrupt vector table do in an I/O system?
(A) It maps interrupt requests to their corresponding interrupt service routines
(B) It manages direct memory access operations
(C) It performs data conversions
(D) It handles programmed I/O operations

99. : Which technique minimizes CPU intervention by allowing peripherals to handle data transfers directly?
(A) Direct Memory Access (DMA)
(B) Programmed I/O
(C) Interrupt-driven I/O
(D) Memory-mapped I/O

100. : What is the primary function of polling in I/O systems?
(A) The CPU repeatedly checks the status of an I/O device to determine if it is ready for data transfer
(B) The I/O device sends an interrupt to the CPU
(C) Data is directly transferred between memory and I/O devices
(D) The system automatically handles data buffering

I/O Techniques (Polling, Interrupts, DMA) MCQs
By: Prof. Dr. Fazal Rehman | Last updated: June 23, 2025

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