Largest and Smallest number ...in 32bit arm Assembly language - arrays

Question

This is a homework problem I have been struggling with all week.
The Guidelines:
" Write a program that asks the user to enter positive nonzero integer values. The user enters a -999 to signal the end of the data series. After all the numbers have been entered, the program should output the largest and smallest numbers entered.
Largest Number: XXXX
Smallest Number: XXXX
If a negative value is entered other than -999 the program should stop with an error message.
I would love to use an array, but can't find a way to use an array to store integers that a user has entered.
I realize it may be a mess, but here is the code I've adapted for a previous program:
.global main
.func main
#Starts Program
main:
sub sp, sp, #24 #stack
ldr r0, =userPrompt #calls prompt
bl printf #prints to screen
ldr r0, =format #calls format
mov r1, SP #Add Stack to register 1
bl scanf
ldr r3, [sp] #stores user input
add sp, sp, #16 #restores stack
mov r5, #0 #Moves 0 into R5
cmp r3, #0 #Compares r3 to 0
blt ex #branches to exception
// bgt ex2 #branches to exception2
storeValue:
STR r1, [r4]
add sp, sp, #24
getNum:
ldr r0, =userPrompt #calls prompt
bl printf #prints to screen
ldr r0, =format #Calls Format
mov r1, sp #Add Stack to register 1
bl scanf #Prints to Screen
ldr r3, [sp] #stores user input
add sp, sp, #16 #restores stack
mov r5, #0 #Moves 0 into R5
cmp r3, #0 #Compares r3 to decimal 0
blt exception #branches to excption if r3 = less than 0
loop: #Beginning of loop
cmp r4, r3 #Compares r3 to r4 to see if equal
bgt end #Greater than Branch
str r4,[] r4, r4, #1 #increases by 1
beq loop #branch if equal
blt loop #branch if less than
#End Program
mov r7, #1 #syscall
swi 0
ex:
ldr r0, = exception #calls exception to print(e)
bl printf #prints to screen
b getNum #branches to getNum to re-ask for a number
LrgNum:
.data
output: .asciz "\n\nLargest Number Entered %d is: %d\n\n\n" "\n\nSmallest Number Entered %d is: %d\n\n\n"
usrPrompt: .asciz "\n\nEnter positive numbers to compare. To see results enter -199 \t"
exception: .asciz "\nInvalid Entry. Enter a positive number greater than 0\n\n"
format: .asciz "%d"
input: .word 0
blanklines: .asciz "\n\n"
exitcom: .word "-199"
.end

Answer 1

For this very specific task, you don’t need an array at all: the minimum and maximum of a sequence can be computed “on-the-fly”, with no need for storing earlier values.
Now I won’t give you assembly code, but I think you already know how to implement all of it.
For the record: storing a sequence of unknown, arbitrarily long length would be much trickier, as you would need to allocate an initial buffer, then increase its capacity each time your buffer is full, by reallocating it with a larger capacity and copying its values. Last, but certainly not least: I am not entirely sure about ARM assembly, but I believe that, to be able to “allocate”, you would have to implement your own small memory manager (i.e., a malloc routine).