Programmed I/O vs interrupt-driven I/O in Operating Systems - Quick Revision & Key Differences

Recall & Review

beginner

What is Programmed I/O?

Programmed I/O is a method where the CPU actively waits and checks the status of an I/O device to see if it is ready for data transfer. The CPU controls the data transfer directly by repeatedly polling the device.

beginner

What is Interrupt-driven I/O?

Interrupt-driven I/O is a method where the I/O device sends a signal (interrupt) to the CPU when it is ready for data transfer. The CPU can perform other tasks and only responds when interrupted by the device.

intermediate

How does CPU usage differ between Programmed I/O and Interrupt-driven I/O?

In Programmed I/O, the CPU is busy waiting and checking the device status, which wastes CPU time. In Interrupt-driven I/O, the CPU can do other work and only stops when interrupted, making better use of CPU time.

intermediate

Which I/O method is more efficient for slow devices and why?

Interrupt-driven I/O is more efficient for slow devices because the CPU does not waste time waiting. It can continue other tasks and only handles the device when it signals readiness.

beginner

What is a disadvantage of Programmed I/O?

A disadvantage of Programmed I/O is that it wastes CPU resources by constantly checking the device status, which can slow down overall system performance.

In Programmed I/O, how does the CPU know when the device is ready?

A By waiting for a timer

B By receiving an interrupt signal

C By using direct memory access

D By continuously checking the device status

Programmed I/O uses polling, where the CPU repeatedly checks the device status to know when it is ready.

What triggers the CPU to handle data transfer in Interrupt-driven I/O?

A A timer event

B A signal from the I/O device called an interrupt

C Continuous polling by the CPU

D Manual user input

In Interrupt-driven I/O, the device sends an interrupt signal to the CPU when it is ready.

Which I/O method allows the CPU to perform other tasks while waiting for the device?

A Interrupt-driven I/O

B Programmed I/O

C Both methods

D Neither method

Interrupt-driven I/O lets the CPU work on other tasks until interrupted by the device.

What is a main drawback of Programmed I/O?

A It cannot handle slow devices

B It requires complex hardware

C It wastes CPU time by busy waiting

D It uses interrupts

Programmed I/O wastes CPU time because the CPU keeps checking the device status instead of doing other work.

Which I/O method is generally better for improving CPU efficiency?

A Interrupt-driven I/O

B Both are equally efficient

C Programmed I/O

D Neither improves CPU efficiency

Interrupt-driven I/O improves CPU efficiency by allowing the CPU to do other work until interrupted.

Explain the main difference between Programmed I/O and Interrupt-driven I/O.

Think about how the CPU learns that the device is ready to transfer data.

Describe one advantage and one disadvantage of Programmed I/O.

Consider CPU usage and complexity.