Study proc$2.$c and trace the program. What will be the output if you run the program? Compile and

run proc$2.$c in a terminal $($or any IDE$)$ and verify your answer.

$2.$ Load proc$2.$s in MARS. This is the MIPS version of proc$2.$c$.$ Do not assemble and run this

program, as there are errors due to the misuse of registers. Study the MAIN function and discuss with

your partners about what it does $($compare it with the C version$).$

$3.$ When MAIN calls SUM, SUM knows where to return to$.$ Why? After SUM called SUB, what happens to the

address returning to MAIN? Discuss with your partners about how you would resolve this problem. Do

not attempt to fix it yet, as we have more problems to come.

$4.$ The input argument $($n$)$ in function SUM is used to call the next function, SUB, as well as being added to

the return value. According to the register convention, the first argument of all function calls must be

stored in $a$0.$ From line $27$ of proc$2.$s$,$ the value in $a$0$ is no longer the same as the input argument

of SUM $($it has been changed to store input argument of SUB$).$ We can resolve this problem by saving the

original $a$0$ into a temporary register, but we may eventually run out of registers if our program is large.

Discuss with your partners about how you would resolve this problem. Do not attempt to fix it yet.

$5.$ Have a look at line $24.$ What happens to the original value in $s$0$ from MAIN after this statement is

executed? Is this a problem? Why? Discuss with your partners about how you would fix this problem.

Do not attempt to fix it yet.

$6.$ Now we know that SUM needs to backup $3$ values before calling SUB. Insert prologue and epilogue into

the code so the program will run correctly. $($Hint: study function SUB, as it does not contain any errors$)$