Interrupt Driven IO vs Polling Basics Quiz

1. What is the primary difference between interrupt-driven I/O and polling?

Polling waits for device status; interrupts notify the processor when ready

Interrupts require more CPU cycles than polling

Polling is faster but consumes more power

Interrupts can only be used for disk I/O

Polling continuously checks the status of a device to determine if it is ready for data transfer, which can waste CPU resources. In contrast, interrupt-driven I/O allows devices to signal the processor when they are ready, enabling more efficient CPU usage and reducing the need for constant checking. This leads to better overall system performance.

Explanation

Polling continuously checks the status of a device to determine if it is ready for data transfer, which can waste CPU resources. In contrast, interrupt-driven I/O allows devices to signal the processor when they are ready, enabling more efficient CPU usage and reducing the need for constant checking. This leads to better overall system performance.

2. In polling, the processor repeatedly checks device status. Which statement best describes this approach?

It minimizes latency by continuously monitoring the device

It wastes CPU cycles when the device is not ready

It eliminates the need for device drivers

It requires hardware interrupt controllers

Polling involves the processor actively checking the status of a device at regular intervals. This can lead to inefficiency, as the CPU may spend time checking for readiness when the device is not prepared to communicate, thereby wasting valuable processing power that could be used for other tasks.

Explanation

Polling involves the processor actively checking the status of a device at regular intervals. This can lead to inefficiency, as the CPU may spend time checking for readiness when the device is not prepared to communicate, thereby wasting valuable processing power that could be used for other tasks.

3. What happens when a device generates an interrupt?

The processor pauses current execution and handles the device request

The device waits until the processor checks its status

The operating system ignores low-priority interrupts

The device controller must poll the processor

When a device generates an interrupt, it signals the processor to temporarily halt its current tasks. This allows the processor to address the device's request immediately, ensuring efficient handling of events and maintaining system responsiveness. This mechanism prioritizes critical tasks and facilitates smooth operation between hardware and software components.

Explanation

When a device generates an interrupt, it signals the processor to temporarily halt its current tasks. This allows the processor to address the device's request immediately, ensuring efficient handling of events and maintaining system responsiveness. This mechanism prioritizes critical tasks and facilitates smooth operation between hardware and software components.

4. Which scenario favors interrupt-driven I/O over polling?

High-frequency, unpredictable device events

Simple devices with predictable, frequent data transfers

Systems with limited interrupt hardware

Real-time systems requiring maximum latency

Interrupt-driven I/O is favored in scenarios with high-frequency, unpredictable device events because it allows the CPU to respond immediately to events as they occur, rather than continuously checking the device status. This efficiency reduces CPU usage and enhances system responsiveness, making it ideal for handling sporadic and rapid input from devices.

Explanation

Interrupt-driven I/O is favored in scenarios with high-frequency, unpredictable device events because it allows the CPU to respond immediately to events as they occur, rather than continuously checking the device status. This efficiency reduces CPU usage and enhances system responsiveness, making it ideal for handling sporadic and rapid input from devices.

5. What is CPU utilization like under polling when devices are idle?

Very low; the processor sleeps

Very high; the processor continuously checks device status

Moderate; polling is balanced with other tasks

Zero; polling halts all processing

Under polling, the CPU continuously checks the status of idle devices to determine if they require attention. This constant checking consumes processing power, leading to high CPU utilization, even when devices are not actively in use. As a result, the processor remains engaged rather than entering a low-power state.

Explanation

Under polling, the CPU continuously checks the status of idle devices to determine if they require attention. This constant checking consumes processing power, leading to high CPU utilization, even when devices are not actively in use. As a result, the processor remains engaged rather than entering a low-power state.

6. In interrupt-driven I/O, the ______ saves the processor's current state before handling the interrupt.

In interrupt-driven I/O, the interrupt handler is a special routine that manages the interrupt signal. Before processing the interrupt, it saves the processor's current state, including registers and program counter, ensuring that the system can resume normal operations seamlessly after the interrupt has been addressed. This mechanism maintains data integrity and system stability.

Explanation

In interrupt-driven I/O, the interrupt handler is a special routine that manages the interrupt signal. Before processing the interrupt, it saves the processor's current state, including registers and program counter, ensuring that the system can resume normal operations seamlessly after the interrupt has been addressed. This mechanism maintains data integrity and system stability.

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7. True or False: Polling is always more efficient than interrupt-driven I/O.

True

False

Polling can be less efficient than interrupt-driven I/O because it consumes CPU time continuously checking the status of devices, even when no data is available. In contrast, interrupt-driven I/O allows the CPU to perform other tasks until a device signals that it requires attention, leading to better resource utilization and overall system performance.

Explanation

Polling can be less efficient than interrupt-driven I/O because it consumes CPU time continuously checking the status of devices, even when no data is available. In contrast, interrupt-driven I/O allows the CPU to perform other tasks until a device signals that it requires attention, leading to better resource utilization and overall system performance.

8. What is context switching in the context of interrupt handling?

Saving and restoring processor state when switching between tasks

Changing the interrupt priority level

Polling multiple devices simultaneously

Disabling all device interrupts temporarily

Context switching in interrupt handling refers to the process of saving the current state of a processor when an interrupt occurs and restoring it when the interrupt is serviced. This allows the system to switch between different tasks efficiently, ensuring that each task can resume from where it left off, maintaining the integrity of their execution states.

Explanation

Context switching in interrupt handling refers to the process of saving the current state of a processor when an interrupt occurs and restoring it when the interrupt is serviced. This allows the system to switch between different tasks efficiently, ensuring that each task can resume from where it left off, maintaining the integrity of their execution states.

9. Which of the following is a disadvantage of interrupt-driven I/O?

Overhead from context switching and interrupt handling

Inability to handle multiple devices

Requires continuous CPU monitoring

Cannot prioritize device requests

Interrupt-driven I/O can lead to significant overhead due to frequent context switching between user programs and the interrupt handler. Each interrupt requires the CPU to save the current state, switch contexts, and then restore the state, which can degrade system performance, especially when handling a high volume of interrupts.

Explanation

Interrupt-driven I/O can lead to significant overhead due to frequent context switching between user programs and the interrupt handler. Each interrupt requires the CPU to save the current state, switch contexts, and then restore the state, which can degrade system performance, especially when handling a high volume of interrupts.

10. When is polling preferred over interrupt-driven I/O?

When devices have predictable, frequent data transfers

When minimizing power consumption is critical

When handling asynchronous device events

When interrupt latency must be minimized

Polling is preferred when devices transfer data at regular intervals, allowing the CPU to check the device status at predictable times. This method can be more efficient in scenarios with high-frequency data transfers, as it reduces the overhead of handling interrupts and can simplify the control flow in the system.

Explanation

Polling is preferred when devices transfer data at regular intervals, allowing the CPU to check the device status at predictable times. This method can be more efficient in scenarios with high-frequency data transfers, as it reduces the overhead of handling interrupts and can simplify the control flow in the system.

11. The ______ is responsible for determining which device caused an interrupt and invoking the appropriate handler.

An interrupt controller is a hardware component that manages interrupt requests from various devices. It identifies which device has generated an interrupt signal and prioritizes these requests. Once the source is determined, it invokes the corresponding interrupt handler, ensuring that the CPU can respond to events efficiently and in the correct order.

Explanation

An interrupt controller is a hardware component that manages interrupt requests from various devices. It identifies which device has generated an interrupt signal and prioritizes these requests. Once the source is determined, it invokes the corresponding interrupt handler, ensuring that the CPU can respond to events efficiently and in the correct order.

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12. True or False: Interrupt-driven I/O can result in lower CPU utilization compared to polling.

True

False

Interrupt-driven I/O allows devices to signal the CPU only when they need attention, freeing the CPU to perform other tasks in the meantime. In contrast, polling requires the CPU to repeatedly check the status of devices, which can lead to wasted cycles and higher CPU utilization. Thus, interrupt-driven I/O can indeed result in lower CPU utilization.

Explanation

Interrupt-driven I/O allows devices to signal the CPU only when they need attention, freeing the CPU to perform other tasks in the meantime. In contrast, polling requires the CPU to repeatedly check the status of devices, which can lead to wasted cycles and higher CPU utilization. Thus, interrupt-driven I/O can indeed result in lower CPU utilization.