Trouble with MIPS array

Question

i'm trying to write some code that take as input integers and strings, stores them into an array and then prints them in order (int-string, int-string etc.). I will eventually add some sorting code for the integer, when i get this to work. The problem is i can't get the code to work right, i can't manage to have the output come out correctly. I'm assuming the problem lies in the array, since i'm not sure how it is supposed to work (MIPS is definitely not my forte). The code is the following:

.data
 array:         .space  400 #array


 in_name:
   .asciiz "\nInsert name: "
 in_date:
   .asciiz "\nInsert date (mmdd): "
 appt:
   .asciiz "\nList: "
 spaz:      .asciiz " "

 .text
 main:      

    la  $s0, array      #load array in s0
    addi    $t0, $zero, 0       #t0=0 counter
    addi    $s1, $zero, 0       #s1=0 array size counter
            j    Input

 Input:
        li  $v0, 4           
    la  $a0, in_date
    syscall             #ask date 
    li  $v0, 5          
    syscall             #read date
    add     $t1, $zero, $t0                #offset in t1
    add     $t1, $t1, $t1           #t1*2
    add     $t1, $t1, $t1           #t1*4
    add     $s2, $t1, $s0           #array with offset in s2
    sw  $v0, 0($s2)     #save date
    addi    $t0, $t0, 1     #t0++
    addi    $s1, $s1, 1     #array size counter +1
    li      $v0, 4
    la      $a0, in_name          
    syscall                         #ask name
        li      $a0, 4                 
    li      $v0, 9
    syscall                         #space for new word (4bytes)
            la      $a0, array
            li      $a1, 4
    li      $v0, 8
    syscall                         #read name
    add     $t1, $zero, $t0                #offset in t1
    add     $t1, $t1, $t1           #t1*2
    add     $t1, $t1, $t1           #t1*4
    add     $s2, $t1, $s0           #array with offset in s2
    sw  $v0, 0($s2)     #save name
    addi    $s1, $s1, 1     #array size counter +1
    addi    $t0, $t0, 1     #t0++
    beq $s1, 10, print          #if array size=10 go to print
    j   Input               #start over until s1=10



  print:
    la  $a0, appt           
    li  $v0, 4          
    syscall             #print list
    addi    $t0, $zero, 0       #t0=0 counter

res:
    add     $t1, $zero, $t0                #offset in t1
    add     $t1, $t1, $t1           #t1*2
    add     $t1, $t1, $t1           #t1*4
    add     $s2, $t1, $s0           #array with offset in s2
    lw  $a0, 0($s2)     #load date
    li  $v0, 1          
    syscall             #print data
    addi    $t0, $t0, 1             #t0++
    la  $a0, spaz               #load space
    li  $v0, 4          
    syscall             #print space
    add     $t1, $zero, $t0                #offset in t1
    add     $t1, $t1, $t1           #t1*2
    add     $t1, $t1, $t1           #t1*4
    add     $s2, $t1, $s0           #array with offset in s2
    lw  $a0, 0($s2)     #load name
    li      $v0, 4
    syscall                         #print name
    addi    $t0, $t0, 1             #t0++
    la      $a0, spaz             
    syscall                         #print space
    addi    $t0, $t0, 1     #t0++ counter
    bne $t0, $s1, res           #start over until t0=s1
    j   end         
 end:
    li  $v0, 10         
    syscall             #the end

Depending on which program i use to test it i get an error or the program ends correctly but with a wrong output (just some numbers). Can someone point out to me how should i correct it to make it work properly? Thanks

Answer 1

I changed the program a little. I created 2 arrays for numbers and strings. As I read date and name I save them to num_array and str_array respectively. This makes it easier to deal with addressing, and might be easier for processing later. Comments in the code should be helpful.

.data
    num_array:   .space 400 #array
    str_array:   .space 400
    in_name: .asciiz "\nInsert name: "
    in_date: .asciiz "\nInsert date (mmdd): "
    appt:    .asciiz "\nList: "
    spaz:    .asciiz " "
 .text
 main:      
    la $s0, num_array        #load array in s0
    la $s1, str_array
    addi $t0, $zero, 0       #t0=0 counter
    addi $s2, $zero, 0       #s1=0 array size counter
    j    Input

 Input:
    # prompt for date
    li  $v0, 4           
    la  $a0, in_date
    syscall

    # read date
    li  $v0, 5          
    syscall

    # store date in the num_array
    sw $v0, 0($s0)

    # increment counter and move to next position in the array
    addi $t0, $t0, 1
    addi $s2, $s2, 1
    addi $s0, $s0, 4

    # prompt for name
    li      $v0, 4
    la      $a0, in_name          
    syscall                         #ask name

    # store name (max 4 bytes) to str_array ($s1)  
    move $a0, $s1
    li      $a1, 4
    li      $v0, 8
    syscall                         #read name

    # move to the beginnig of next string in $s1
    # increment by 4 because length of each input word is 4
    addi $s1, $s1, 4

    beq $s2, 10, print          #if array size=10 go to print
    j   Input               #start over until s1=10



print:
    # print "List:"
    la  $a0, appt           
    li  $v0, 4          
    syscall             #print list

    addi    $t0, $zero, 0       #t0=0 counter    
    la $s0, num_array # address of num_array
    la $s1, str_array # address of str_array
res:
    # get number from num_array and print it
    lw $a0, 0($s0)
    li $v0, 1
    syscall

    # move to the next element, increment by 4 because numbers take 1 word = 4 bytes
    addi $s0, $s0, 4 

    # get string from str_array and print it
    la $a0, 0($s1)
    li $v0, 4
    syscall

    # print space
    la $a0, 32
    li $v0, 11
    syscall

    # move to the next element, increment by 4 because strs have 4 bytes length (in your case)
    addi $s1, $s1, 4

    # increment loop counter
    addi $t0, $t0, 1
    blt $t0, $s2, res # $s2 is size of the array
end:
    li  $v0, 10         
    syscall             #the end

Here is the output:

Insert date (mmdd): 1201

Insert name: aaa
Insert date (mmdd): 1202

Insert name: bbb
Insert date (mmdd): 1203

Insert name: ccc
Insert date (mmdd): 1204

Insert name: ddd
Insert date (mmdd): 1205

Insert name: eee
Insert date (mmdd): 1206

Insert name: fff
Insert date (mmdd): 1207

Insert name: ggg
Insert date (mmdd): 1208

Insert name: hhh
Insert date (mmdd): 1209

Insert name: iii
Insert date (mmdd): 1210

Insert name: jjj
List: 1201aaa 1202bbb 1203ccc 1204ddd 1205eee 1206fff 1207ggg 1208hhh 1209iii 1210jjj 
-- program is finished running --