Question

In a memory mapped input/output __________

(a) the CPU uses polling to watch the control bit constantly, looping to see if a device is ready

(b) the CPU writes one data byte to the data register and sets a bit in control register to show that a byte is available

(c) the CPU receives an interrupt when the device is ready for the next byte

(d) the CPU runs a user written code and does accordingly

I had been asked this question during an interview for a job.

My doubt stems from Process Structures in section Distributed Communication of Operating System

Answer 1

Correct answer is (b) the CPU writes one data byte to the data register and sets a bit in control register to show that a byte is available

The best explanation: None.