Question

2. Single step the instructions.s program through at least two exceptions. Make sure that you see how the flow of control is changed by comparing the source code with PCSpim windows, pay particular attention to all registers.

Question 2 (0.4): how do you recognise that the normal program flow has been interrupted?

Question 3 (0.5): how can you find out what exception condition has occurred and what caused it?

#--------------------instruction.s---------------------
# This program implements:
#       sum = 0;
#       i = 9;
#       do {
#               sum = sum + A[9-i]
#               B[9-i] = sum;
#               i--;
#       }
#       until (i = 0) 


                .globl main     
main:
                add     $t2, $0, $0     # sum = 0  (sum is in $t2)
                add     $t1, $0, $0     # Set $t1 to point to beginning of data
                lw      $t4, 84($t1)    # Constant 4 stored in $t4
                lw      $t0, 88($t1)    # Constant 9 stored in $t0 (i)
                lw      $t5, 92($t1)    # Constant -1 stored in $t5
                add     $t1, $t1,$t4    # A starts at 4 (move $t1 to point to A)
loop:
                lw      $t3, 0($t1)     # $t3 has A[k]
                add     $t2, $t2, $t3   # sum = sum + A[k]
                sw      $t2, 40($t1)    # B[k] = sum
                add     $t1, $t1, $t4   # update address pointer
                add     $t0, $t0, $t5   # i--
                beq     $t0, $0, done   # if i = 0 go to done
                j       loop            # if i > 0 go to loop
done:   
                add     $t1, $0, $0     # Set $t1 to point to beginning of data
                sw      $t2, 0($t1)     # sum is stored
                li      $v0, 4          # print_str
                la      $a0, message    # load address of string 
                syscall                 #
                li      $v0, 1          # print_int
                lw      $a0, sum        # load integer value
                syscall                 #
                jr      $ra             # return to the main program
                add     $0, $0, $0      # nop


                .data
sum:            .word   0
A:              .word   0, 1, 2, 3, 4, 5, 6, 7, 8, 9
B:              .word   0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Four:           .word   4
Nine:           .word   9
Minus1:         .word   -1
message:        .asciiz "\nThe value of sum is:  

Answer 1

Please find the answer below.
Please do comments in case of any issue. Also, don't forget to rate the question. Thank You So Much.

Here error was due to following line of code.

1. due to line where it is mentioned t# Set $t1 to point to beginning of data

becuase the starting address of data is 0x10010000. It was initiated with 0

2. same error at another place whre t1 initialized to beginning of data.

3. " was missing in message data .

message:        .asciiz "\nThe value of sum is:  

Updated code is as below.

.globl main   
.text
main:
add $t2, $0, $0 # sum = 0 (sum is in $t2)
add $t1,$0,0x10010000 # Set $t1 to point to beginning of data
lw $t4, 84($t1) # Constant 4 stored in $t4
lw $t0, 88($t1) # Constant 9 stored in $t0 (i)
lw $t5, 92($t1) # Constant -1 stored in $t5
add $t1, $t1,$t4 # A starts at 4 (move $t1 to point to A)
loop:
lw $t3, 0($t1) # $t3 has A[k]
add $t2, $t2, $t3 # sum = sum + A[k]
sw $t2, 40($t1) # B[k] = sum
add $t1, $t1, $t4 # update address pointer
add $t0, $t0, $t5 # i--
beq $t0, $0, done # if i = 0 go to done
j loop # if i > 0 go to loop
done:   
add $t1,$0,0x10010000 # Set $t1 to point to beginning of data
sw $t2, 0($t1) # sum is stored
li $v0, 4 # print_str
la $a0, message # load address of string
syscall #
li $v0, 1 # print_int
lw $a0, sum # load integer value
syscall #
jr $ra # return to the main program
add $0, $0, $0 # nop

.data
sum: .word 0
A: .word 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
B: .word 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Four: .word 4
Nine: .word 9
Minus1: .word -1
message: .asciiz "\nThe value of sum is: "

2.)

On executing default code follwoing error was there.

3)

By seeing the error it is noticible that the program is trying to accesss non exist element in memroy. And it was causing the exception.