Convert Binary to Decimal in MIPS, Assembly MARS -

i trying convert binary decimal in mips language, using mars simulator. program accepts binary number, , conversion, multiplying (shift left number's place $t9). way of saying multiplying each 1 digit 2 raised power of place, , summing result.

i not have understanding of how values stored , communicated between ascii, decimal, , problem "sum" coming out 40,000 rather value of binary number in decimal. doing wrong here?

 .data   msg1:     .asciiz "enter number in base 2 (-2 quit): "   msg2:     .asciiz "\nresult: "   allones:     .asciiz "1111111111111111"   empty:     .space 16   newline:     .asciiz "\n"   sum:     .space 16    summsg:     .asciiz "\nsum: "   onefound:     .asciiz "\none found\n"   zerofound:      .asciiz "\nzero found\n" .text .globl main main:  getnum: li $v0,4        # print string system call la $a0,msg1         #"please insert value (a > 0) : " syscall  la $a0, empty li $a1, 16              # load 16 max length read $a1 li $v0,8                # 8 string system call syscall  la $a0, empty li $v0, 4               # print string syscall  li $t4, 0               # initialize sum 0  startconvert:   la $t1, empty   li $t9, 16                # initialize counter 16  firstbyte:   lb $a0, ($t1)      # load first byte   blt $a0, 48, printsum    addi $t1, $t1, 1          # increment offset   subi $a0, $a0, 48         # subtract 48 convert int value   beq $a0, 0, iszero   beq $a0, 1, isone   j convert     #   iszero:    subi $t9, $t9, 1 # decrement counter    j firstbyte   isone:                   # 2^counter     li $t8, 1               # load 1    sllv $t5, $t8, $t9    # shift left counter = 1 * 2^counter, store in $t5    add $t4, $t4, $t5         # add sum previous sum      move $a0, $t4        # load sum    li $v0, 1              # print int    syscall    subi $t9, $t9, 1 # decrement counter    j firstbyte  convert:  printsum:    srlv $t4, $t4, $t9    la $a0, summsg    li $v0, 4    syscall   move $a0, $t4      # load sum  li $v0, 1      # print int  syscall  exit:    li $v0, 10       # exit system call    syscall 

one issue you're decrementing $t9 twice per iteration. should leave first decrement (the 1 after subtracting 48) is, , remove other two.

another issue if parsing string left-to-right, need take length of string account @ point. ideally, you'd setting $t9 length of string instead of 0 (on second line after startconvert), don't yet know length of string.

one option parse through string beforehand determine length, , set $t9 value.

a more elegant way whole thing in 1 pass: assume string 16 characters long, including delimiter (so, assign 16 $t9 first). suppose string 5 characters long. after loop, sum high factor of 2^(16-5) = 2^11. observe final value of $t9 11. can fix error shifting sum register right $t9 many bits.

finally, looks mars putting character of 0x0a (this pressing enter) onto end of string (except when use 15 characters; uses 0x00 instead, because automatically stops after 15th character before giving chance press enter). on beqz line, instead of comparing 0, instead check if $a0 < 48. take care of both cases, whether delimiter 0x00 or 0x0a.

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here's version fixes:

.data   msg1:     .asciiz "enter number in base 2 (-2 quit): "   msg2:     .asciiz "\nresult: "   allones:     .asciiz "1111111111111111"   empty:     .space 16   newline:     .asciiz "\n"   sum:     .space 16    summsg:     .asciiz "\nsum: "   onefound:     .asciiz "\none found\n"   zerofound:      .asciiz "\nzero found\n" .text .globl main main:  getnum: li $v0,4        # print string system call la $a0,msg1         #"please insert value (a > 0) : " syscall  la $a0, empty li $a1, 16              # load 16 max length read $a1 li $v0,8                # 8 string system call syscall  la $a0, empty li $v0, 4               # print string syscall  li $t4, 0               # initialize sum 0  startconvert:   la $t1, empty   li $t9, 16             # initialize counter 16  firstbyte:   lb $a0, ($t1)      # load first byte   blt $a0, 48, printsum    # don't think line works    addi $t1, $t1, 1          # increment offset   subi $a0, $a0, 48         # subtract 48 convert int value   subi $t9, $t9, 1          # decrement counter   beq $a0, 0, iszero   beq $a0, 1, isone   j convert     #   iszero:    j firstbyte   isone:                   # 2^counter     li $t8, 1               # load 1    sllv $t5, $t8, $t9    # shift left counter = 1 * 2^counter, store in $t5    add $t4, $t4, $t5         # add sum previous sum      move $a0, $t4        # load sum    li $v0, 1              # print int    syscall    j firstbyte  convert:  printsum:    srlv $t4, $t4, $t9     la $a0, summsg    li $v0, 4    syscall   move $a0, $t4      # load sum  li $v0, 1      # print int  syscall  exit:    li $v0, 10       # exit system call    syscall