$($a$)$ The von Neumann machine contains the CPU, memory, and I$/$O devices. Can

we have a system without any I$/$O devices? Explain. $[3]$

$($b$)$ Computer A uses ASCII to encode characters while Computer $B$ uses $xYZ$

encoding invented by the company instead. As a designer for $B,$ try to argue

against the use of $xYZ$ encoding. $[2]$

$($c$)$ There are $3$ variables to consider if we should turn on the air conditioner and the

dehumidifier.

Let the logical variables $a,b$ and $c$ represent the conditions that temperature is

high, himidity is high and many people in the room respectively. Write down a

truth table with input $a,b,c,$ and output $d$ and $e,$ where $d$ is "turn on aircon"

and $e$ is "turn on dehumidifer".

Write down the logical expression $f$ and $g$ in terms of $a,b$ and $c$ for turning on

the aircon and dehumidifier respectively, i$.$e$.$

$d=f(a,b,c)$

$e=g(a,b,c)$

Simplification of the logical expressions are not required.

$($d$)$ Virutal memory system allows you to map a CPU address to an address anywhere

in the physical memory by means of a page table. Consider the PP$360$ CPU

which has a reset address at $0,$ i$.$e$.$ the CPU will run at address $0$ on power reset.

Explain if we can$/$cannot put the boot program at address $0xffff0000?$

$($e$)$ A computer Kell $530$ has both $SSD$ and $HDD.$ Suggest a way to improve the

performance of external storage access by suitably using the $SSD$ and $HDD.$