None of the disk$-$scheduling disciplines, except FCFS$,$ are truly fair

$($starvation may occur$).$

$($a$)$ Explain why this assertion is true.

$($b$)$ Describe a way to modify algorithms such as SCAN to ensure

fairness.

$($c$)$ Explain why fairness is an important goal in a time$-$sharing

system.

$($d$)$ Give three or more examples of circumstances in which it is

important that the operating system be unfair in serving $\frac{\text{I}}{O}$

requests.