Assembly Program: Recursion?

Question

I need to write a program that will iterate 10 times. Each time it will update a value and print it to the screen.

I know there has to do something with creating a stack and saving the the value so it can iterate back and get to the correct portion to continue with the program. Iv tried many things but I cant figure it out. Here is my code so far

# ############################################################### #
# Phase2.ASM                                                      #
#                                                                 #
# This program will recurse 10 times and show how much interest   #
# is made after 10        "months"                                        #
#                                                                 #
# ############################################################### #   

.data

PRINCIPAL:  .float  100.0   # principal = $100.00
INTEREST_RATE:  .float  0.012   # interest  = 1.2%

promptFirst:     .asciiz "Your starting Principal is $100.00: \n"
promptSecond:     .asciiz "Your interest rate is 1.2%: \n"
promptNow:          .asciiz "Interest Made After a Month:\n"
.text
.globl main

main:   



First:   
     # Prints the first prompt  
     li $v0, 4               # syscall number 4 will print string whose address is in $a0       
     la $a0, promptFirst     # "load address" of the string
     syscall                 # actually print the string   


Second:  
     # Prints the second prompt
     li $v0, 4               # syscall number 4 will print string whose     address is in $a0   
     la $a0, promptSecond    # "load address" of the string
     syscall                 # actually print the string    



jal CI


j EXIT



CI:




    la  $a0, PRINCIPAL  # load the address of the principal
    la  $a1, INTEREST_RATE  # load the address of the principal

    lwc1  $f2, ($a0)    # load the principal
    lwc1  $f4, ($a1)    # load the interest rate    
    mul.s $f12, $f4, $f2    # calculate the balance


    li $v0, 4            # syscall number 4 will print string whose address is in $a0   
    la $a0, promptNow    # "load address" of the string
    syscall              # actually print the string
    li  $v0, 2           # system call #2   
    syscall

jr $ra




EXIT:    
jr $ra


# END OF THE LINES ###############################################

My Current output so far:

Your starting Principal is $100.00:

Your interest rate is 1.2%:

Interest Made After a Month:

1.20000005

Aany help would really be appreciated. I really am terrible at assembly programming.

PS: The assignment HAS to be done via recursion

EDIT! NEW CODE

# ############################################################### #
# Phase2.ASM                                                      #
#                                                                 #
# This program will recurse 10 times and show how much interest   #
# is made after 10     "months"                                       #
#                                                                 #
# ############################################################### #   

.data

PRINCIPAL:  .float  100.0   # principal = $100.00
INTEREST_RATE:  .float  1.012   # interest  = 1.2%

promptFirst:     .asciiz "Your starting Principal is $100.00: \n"
promptSecond:     .asciiz "Your interest rate is 1.2%: \n"
promptNow:          .asciiz "\nYour Balance After A Month:\n"
.text
.globl main

main:   



First:   
     # Prints the first prompt  
     li $v0, 4               # syscall number 4 will print string whose address is in $a0       
     la $a0, promptFirst     # "load address" of the string
     syscall                 # actually print the string   


Second:  
     # Prints the second prompt
     li $v0, 4               # syscall number 4 will print string whose address is in $a0   
     la $a0, promptSecond    # "load address" of the string
     syscall                 # actually print the string    


li $t1, 0
jal CI

ENDCI:
j EXIT



CI:



    add $t1, $t1, 1 
    la  $a0, PRINCIPAL      # load the address of the principal
    la  $a1, INTEREST_RATE  # load the address of the principal

    lwc1  $f2, ($a0)        # load the principal
    lwc1  $f4, ($a1)        # load the interest rate    
    mul.s $f12, $f4, $f2    # calculate the balance


    li $v0, 4               # syscall number 4 will print string whose address is in $a0   
    la $a0, promptNow       # "load address" of the string
    syscall                 # actually print the string
    li  $v0, 2              # system call #2    
    syscall

    beq $t1, 10, ENDCI
    jal CI
jr $ra




EXIT:    
jr $ra


# END OF THE LINES ###############################################

new output:

our starting Principal is $100.00: Your interest rate is 1.2%:

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

Your Balance After A Month:

101.19999695

So i got the code to iterate 10 times. I need to update the amount so it shows up the previous month + interest added

Iv tried some lil stuff. Nothing really worth mentioning. I have examples from class on how to set up the stack frame and frame pointers but dont really know what im doing. — CoffeePeddlerIntern, Mar 11 '13 at 03:06
I got it where it iterates 10 times now. But the value doesnt update. Im not really sure how to to it with floating point numbers and how to update it and save it. — CoffeePeddlerIntern, Mar 11 '13 at 03:08

score 1 · Accepted Answer · answered Mar 11 '13 at 08:50

You need to store the current balance after each update so that the next call doesn't keep using the original value.

I.e. something like this:

lwc1  $f2, ($a0)        # load the principal
lwc1  $f4, ($a1)        # load the interest rate    
mul.s $f12, $f4, $f2    # calculate the balance
swc1  $f12, ($a0)

Before each additional call to CI you also need to save the current return address, and then restore it before returning:

addi $sp,$sp,-4     # push the current return address
sw   $ra,($sp)      # ...
beq  $t1, 10, CIRET
jal  CI
CIRET:
lw   $ra,($sp)      # pop the saved return address
addi $sp,$sp,4      # ....
jr   $ra

Thanks you so very much for your response. Helped a lot! Really appreciate it! — CoffeePeddlerIntern, Mar 11 '13 at 15:11

score 0 · Answer 2 · answered Mar 11 '13 at 01:46

0

The problem does not call for a recursion - a simple loop would do. A loop in assembly is just a conditional jump up the code (or an unconditional jump up combined with a conditional jump ahead).

The condition is counter-based, the counter would go from 0 to 9, or from 9 to 0, it's usually easier in assembly to do a conditional jump based on a comparison with zero.

answered Mar 11 '13 at 01:46

Seva Alekseyev

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Part of the assignment is that it has to be via recursion – CoffeePeddlerIntern Mar 11 '13 at 01:50

Assembly Program: Recursion?

2 Answers2