Programming in mips


by missinglink
Tags: mips, programming
missinglink
missinglink is offline
#1
Jan23-13, 04:12 PM
P: 1
I am trying to teach mips to my self and wrote a fairly simple program and it isn't working and found out that the strings I declared in .data are somehow affecting one of my pointers.

Here is the code:

#Write a program that allows the user to enter 5 ints and store these ints in an array and display them in reverse order

.data


msg: .asciiz "Enter your number: "
msg1: .asciiz "Here are your numbers: "
msg2: .asciiz " "
array: .data 20


.text

main:

la $s0, array

add $t0, $s0, $zero

li $t1, 0
li $t2, 5

loop:

li $v0, 4

la $a0,msg

syscall

li $v0, 5

syscall

add $t2, $v0, $zero

sw $t2, 0($t0) # This is the line causing errors

addi $t0, $t0, 4
addi $t1, $t1, 1

slt $t3, $t1, $t2

bne $t3, $zero, loop

li $v0, 4

la $a0, msg1

syscall

li $t5, 0

loop1:

add $t0, $t0, -4

lw $t4, 0($t0)

li $v0, 4

add $a0, $t4, $zero

syscall

li $v0, 4

la $a0, msg2

syscall

addi $t1, $t1, -1

slt $t2, $t5, $t1

bne $t2, $zero, loop1

li $v0, 10

syscall


Can anyone help please?
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Mark44
Mark44 is offline
#2
Jan24-13, 09:27 AM
Mentor
P: 21,009
When you post code, it's good manners to put [ code ] and [ /code ] tags around it (without the extra spaces). I have done that below.
Quote Quote by missinglink View Post
I am trying to teach mips to my self and wrote a fairly simple program and it isn't working and found out that the strings I declared in .data are somehow affecting one of my pointers.

Here is the code:
#Write a program that allows the user to enter 5 ints and store these ints in an array and display them in reverse order

.data 


msg: .asciiz "Enter your number: "
msg1: .asciiz "Here are your numbers: "
msg2: .asciiz " "
array: .data 20


.text

main:

la $s0, array

add $t0, $s0, $zero

li $t1, 0
li $t2, 5

loop:

li $v0, 4

la $a0,msg

syscall

li $v0, 5

syscall

add $t2, $v0, $zero

sw $t2, 0($t0) # This is the line causing errors

addi $t0, $t0, 4
addi $t1, $t1, 1

slt $t3, $t1, $t2

bne $t3, $zero, loop

li $v0, 4

la $a0, msg1

syscall

li $t5, 0

loop1:

add $t0, $t0, -4

lw $t4, 0($t0)

li $v0, 4

add $a0, $t4, $zero

syscall

li $v0, 4

la $a0, msg2

syscall

addi $t1, $t1, -1

slt $t2, $t5, $t1

bne $t2, $zero, loop1

li $v0, 10

syscall
Can anyone help please?
I took a stab at running your code, and hit the same exception at the line you indicated. Since there essentially no comments in your code, it's difficult to tell what you are trying to do. Comments are even more important in assembly code, to help a reader (including yourself) understand what, and more importantly, why you are doing something.

It would be a good idea for you to break up your code into sections, using comments, where each section has a specific purpose.

The first block of code should ask the user to input the five numbers. When I ran your code, it continued asking for numbers well past the fifth. Your loop should keep track of how many times it has run, so that it asks for only five numbers and then moves on.

The final block should print the numbers. The simplest way to do this would be to merely print the numbers in reverse order, starting at the last number in the array (the highest memory address), and working your way to the beginning. I am assuming you don't actually need to reverse the numbers in the array itself.

With regard to the exception you're getting, this code:
sw $t2, 0($t0)
stores the value at $t2 (R10) at location $t0 + 0 (R8 + 0). When I ran the program, the address in R8 was 0, which meant that the program was trying to store a value in location 0.


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