What is wrong with my code? (adding numbers in an array)

Question

So, recent I have been taking assembly classes and one of them gave me an assignment. I coded everything except the last part... I just have to add the numbers in a given array and print the sum... easy right? No, i have an error when i run it says that line 12 is out of range for some reason =/

So, here is my code:

.data

array: .word 1,2
size: .word 2
la $s0, array
lw $s1, size
li $t9, 0

.text

loop:
lw $a0, ($s0)
add $a0, $a0, $a0
addi $s0, $s0, 4
add $t9, $t9, 1
blt $t9, $s1, loop

li $v0, 1
syscall

which line is line 12? lw $a0, ($s0)? What exactly is the error message? And what do you see when you run this in a debugger and look at register values? — Peter Cordes
– Peter Cordes, Commented Sep 24, 2017 at 17:01
@peter Cordes Error in C:\Users\Mohamad\Desktop\addingarray.asm line 13: Runtime exception at 0x00400004: address out of range 0x00000000 — Mohammad Al Baba
– Mohammad Al Baba, Commented Sep 24, 2017 at 17:23

Peter Cordes · Accepted Answer · 2017-09-24 17:27:36Z

2

la $s0, array is in the .data section, so it never executes.

If you'd used a debugger to single-step, you would have seen that your program never executes the instructions in the data section, and presumably starts execution at loop:.

At that point, $s0 happens to still be zero (according to your error message). Anyway, it's not pointing at array.

edited Sep 24, 2017 at 17:27

answered Sep 24, 2017 at 17:03

Peter Cordes

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7 Comments

Mohammad Al Baba Over a year ago

yes that worked great and i even noticed some logic errors and it now runs great thanks. 1 more thing... if i want to compare to strings do i just use beq bne? or is there more to it? im having some problems with my other program

Mohammad Al Baba Over a year ago

i just wanna see if a word is in the array here is my code idk whats wrong tbh

.data array: .asciiz "one", "two", "three" word: .asciiz "nine" msgone: .asciiz "\nThe word is found" msgtwo: .asciiz"\nThe word was not found" size: .word 4  .text la $s0, array lw $s1, size la $a1, word li $t9, 0   loop: beq $t9, $s1 , fail la $a0, ($s0) addi $s0, $s0, 4 add $t9,$t9, 1 beq $a1, $a0, found bne $a1, $a0, loop     fail: la $a0, msgtwo li $v0, 4 syscall  found: la $a0, msgone li $v0, 4 syscall  j done  done:

Peter Cordes Over a year ago

@MohammadAlBaba: If you entire string fits in a 32-bit register, yeah you could compare it with beq. Otherwise not. google for how to implement strcmp in asm. use a debugger. If you're using SPIM or MARS, there's probably one built-in.

Mohammad Al Baba Over a year ago

i am using mars but my program always says that the string isnt contained in the array its making me a bit insane :P

Peter Cordes Over a year ago

@MohammadAlBaba: So single-step your code and look at what values are in registers. Note that .asciiz "one" is 4 bytes, but .asciiz "three" is 6 bytes long. So your "array" isn't an array anymore. It's just some concatenated data with separately-labeled elements, separated by 0 bytes.

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