Answer from cs61c-ei (Jing Chen 16669246) for Question 3
Polling is the process of periodically checking status bits to see if it is time for the next I/O operation and is the simplest way for an I/O device to communicate with the processor. The principal drawback to this is that it wastes a lot of processor time because processors are much faster than I/O devices. The processor may read from the Status register many times until the next I/O operation.