wrong integer output Mips

Question

I'm getting a wrong output when using this:

li $v0, 1

I have to save the user input as ASCII (from 0 to 9), convert it to integer, and then, print it as integer.

But when I have for example 10 in my register, it prints 16; when I have 20, it prints 32 and so on... it goes printing: my_number + 6^(n) and I don't know why...

This is my code:

.data
num1:   .space 32
num2:   .space 32
entra:  .asciiz "Put your Decimal: "
sale:   .asciiz "\nDecimal is: "        
.globl __start
.text
__start:    
la $a0, entra           # print 1st text
li $v0, 4
syscall
la $s4, num1            # space to put the copy of user's word without \n

li $a1, 25              # space to put user's word (number)
li $v0, 8               # take input
la $a0, num2   
syscall


li $t1, -1          # counter to know how many times we iterate over EliminarEnter

jal EliminarEnter       # this function remove \n char and save it to $t4

jal Funcion         # getting the symbol of the char
li $v0, 10
syscall             # exit

EliminarEnter:
    addi $t1, $t1, 1        # increment counter
    lb $t2, 0($a0)          # take byte of users word
    beq $t2, 10 QuitarEnter     
    sb $t2, 0($s4)          # save the byte in $t4
    addi $s4, $s4, 1        
    addi $a0, $a0, 1        # increment pointer in the word

j EliminarEnter

QuitarEnter:        
    jr $ra          
Funcion:
    sub $s4, $s4, $t1       # go to the first memory adress

Bucle: 

    lb $t2, 0($s4)      
    beq $t2, $zero Acabar   # if char is null '\0' --> End of program
    addi $t3, $t2, -48  # -48, t get the symbol of my char
    j GuardarIncrementar


GuardarIncrementar:

    rol $t4, $t4, 4     # rol positions
    add $t4, $t4, $t3   # where I save the decimal number
    addi $s4, $s4, 1    # increment adress of my new ASCII word (without '\n')

    j Bucle

Acabar:


    la $a0, sale        # printing 2nd text
    li $v0, 4
    syscall



    add $v1, $zero, $t4
    move $v0, $v1       
    move $a0 , $v0
    li $v0, 1       # printing MY NUMBER... THING THAT DOESNT WORK!!!
    syscall
    jr $ra          # exit

Sounds like you're treating your input string as hex (base 16). You can't have a string in your register, BTW. Did you check the docs for the system calls your program is using? And did you look at register values in a debugger? — Peter Cordes
– Peter Cordes, Commented Oct 8, 2016 at 22:10
I guess I'm working with the numbers in the ASCII table that relates to each character (number 0 --> the symbol of 48 is 0 and so on...), and yep, this code comes from a program in which I had to convert from Hex to Dec ;D — noona mun
– noona mun, Commented Oct 8, 2016 at 23:03

Craig Estey · Accepted Answer · 2016-10-08 22:12:38Z

2

You want to do decimal, so in GuardarIncrementar

Change:

    rol $t4, $t4, 4     # rol positions

Into:

    mul $t4, $t4, 10    # multiply by base 10

answered Oct 8, 2016 at 22:12

Craig Estey

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Peter Cordes · Accepted Answer · 2016-10-08 22:15:13Z

0

I think you're converting each input digit to a 4-bit number, and using

rol $t4, $t4, 4            # multiply by 16
add $t4, $t4, $t3          # and add the new digit

to accumulate the integer value.

That puts each input digit in its own 4 bits of the integer, which means you're treating your input as base 16 (but without handling A-F).

In base 10, you need to multiply by 10, not 16. So you can't use a single shift or rotate.

answered Oct 8, 2016 at 22:15

Peter Cordes

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