dem10 0 Newbie Poster

Hello all, I am trying to write code for these three functions.
1. readdata: The readdata function has two parameters ($a0 and $a1) which contain the addresses of two integers. The function is to prompt and read two integers. The strings for the prompts are provided in the data segment. Once the integers are read, the function readdata must then call the function order which places the values in the ascending order. As this function calls another function, you must store $ra on the runtime stack at the beginning of the function and restore it the end. This function must access the memory ONLY through the parameters in $a0 and $a1.

2. order: The function order has two parameters ($a0 and $a1) that contain the addresses of two integers. The function must arrange the values referred to by the parameters so they are in ascending order. To do this, you must read the values from memory into the registers $s0 and $s1, compare them and save them in ascending order. As $s0 and $s1 are “saved” registers, they must be stored on the runtime stack at the beginning of the function and restored to the original values at the end. As this is a leaf function, the $ra does not need to be stored.

3. getsum: The getsum function has two parameters ($a0 and $a1). This function must determine the sum of the numbers from the first value in $a0 through the second value in $a1. For example, if the values are 5 and 8, then the sum is 26. This value must be returned using the register $v0. Do not use any saved registers in this leaf function.

Not required, but good to do: this function is easily done recursively. Give it a try!

Requirements:
1. each function must have a comment with a description of the purpose of the function
2. all instructions must be commented.
3. parameters must be passed using the registers specified
4. return value must be returned using the register specified
5. $s0 and $s1 must be saved on the stack, used and restored from the stack in the function order
6. $ra must be saved on the stack and restored from the stack in function readdata


I wrote code for the first two functions. However, when I try to run it I get this error:
line 79: Runtime exception at 0x004000ac: store address not aligned on word boundary 0x00000001. Does anybody know what this could be. My code is below:

.data
	.word 0
	.word 0
prompt1: .asciiz "Enter a number "
prompt2: .asciiz "Enter another number "
result:  .asciiz "The sum of the numbers is  "
	
	.text
	.globl main
main:
	li $s0, 1		#initialize for saving registers test
	li $s1, 2		#initialize for saving registers test

#note: at this point, the values of $s0 and $s1 now should be 1 and 2

#read data
	lui $a0, 0x1001	#address of first integer loaded as parameter
	addu $a1, $a0, 4	#address of second integer loaded as parameter
	jal readdata		#jump to the readdata function

#note: at this point, the values of $s0 and $s1 again should be 1 and 2 and 
#	the input values should be stored into memory in ascending order

#get sum
	lui $t0, 0x1001	#set address of first integer
	lw $a0, ($t0)		#get first number
	lw $a1, 4($t0)	#get second number	
	jal getsum		#call getsum function
	move $s2, $v0		#get the return value
	
#print results
	la $a0, result	#get string for result
	li $v0, 4		#set command to print string
	syscall		#print string
	move $a0, $s2		#get saved value of sum
	li $v0, 1		#set command to print integer
	syscall		#print integer

#exit	
	li $v0, 10		#set command to end program
	syscall		#end program

# Your code goes here.
	
readdata:
	addi	$sp, $sp, -4
	sw	$ra, ($sp)
	# sw 	$a0, 4($sp)
	# sw 	$a1, 8($sp)

	li	$v0, 4
	la	$a0, prompt1
	syscall 

	li	$v0, 5
	syscall
	move	$a0, $v0
	
	li	$v0, 4
	la	$a0, prompt2
	syscall
	
	li	$v0, 5
	syscall
	move	$a1, $v0

	jal 	order

	# lw 	$a0, 4($sp)
	# lw 	$a1, 8($sp)
	lw 	$ra,  ($sp)
	jr 	$ra

order:
	addi	$sp, $sp, -8
	sw 	$s0, 4($sp)
	sw 	$s1, 8($sp)

	lw 	$s0, ($a0)
	lw	$s1, ($a1)
	
	bgt	$s0, $s1, swapval
	jal 	ret

	swapval: 
		move 	$t1, $s0
		move	$s0, $s1
		move 	$s1, $t1
		jal 	ret

	ret:
		lw 	$s0, 4($sp)
		lw 	$s1, 8($sp)
		jr	$ra

getsum:
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