$($a$)$ Explain the following data structures, including in each explanation a diagram:

$($i$)$ A Queue

$($ii$)$ A Stack

$($iii$)$ A Heap

$(2$ marks for each answer$)$

$($b$)$ Explain the purpose of the Job Scheduler. What optimisations does it perform while scheduling?

$(9$ marks$)$

$($c$)$ What are the fields of the Process Control Block $($PCB$)?$ Provide an explanation for each field.