我如何在 mips 中将新行打印到文本文件中，它只是打印一个空格

Question

I have the following code in MIPS that i run it in mars simulator The code open a text file for writing The problem with the result it keep printing all strings that i provide in My code without printing any new line i tried to separate new line from the string it did not work it keeping print space instead of new line Here is my code

.data

fout:   .asciiz "testout.txt"      # filename for output
buffer: .asciiz "The quick brown fox jumps over the lazy dog."
buffer1:  .asciiz "\n"
 .text
 .globl main
 main:

  ###############################################################    
  # Open (for writing) a file that does not exist    
  li   $v0, 13       # system call for open file    
  la   $a0, fout     # output file name    
  li   $a1, 1        # Open for writing (flags are 0: read, 1: write)    
  li   $a2, 0        # modeA is ignored    
  syscall            # open a file (file descriptor returned in $v0)    
  move $s6, $v0      # save the file descriptor     

  ###############################################################    
  # Write to file just opened    
  li   $v0, 15       # system call for write to file    
  move $a0, $s6      # file descriptor     
  la   $a1, buffer   # address of buffer from which to write    
  li   $a2, 46      # hardcoded buffer length    
  syscall            # write to file    

  ###############################################################    
  # Write to file just opened    
  li   $v0, 15       # system call for write to file    
  move $a0, $s6      # file descriptor     
  la   $a1, buffer1 # address of buffer from which to write    
  li   $a2, 1     # hardcoded buffer length    
  syscall            # write to file    

  ###############################################################      
  # Write to file just opened
  li   $v0, 15       # system call for write to file    
  move $a0, $s6      # file descriptor 
  la   $a1, buffer   # address of buffer from which to write    
  li   $a2, 44       # hardcoded buffer length    
  syscall            # write to file    

  ###############################################################    
  # Close the file 
  li   $v0, 16       # system call for close file
  move $a0, $s6      # file descriptor to close
  syscall            # close       
  li $v0,10 
  syscall 

Answer 1

Your base code was pretty much correct. And well commented! Good job.

The main issue was that you were hardwiring the string lengths.

In the first syscall for buffer , the length was 46 [too high] and the file got an EOS char on the line. There was a newline output after that.

In the second syscall for buffer , the length was 44 [too low] and the file line was chopped. There was no newline output after that because you didn't do a syscall for one.

So, the simple fix would be to just manually adjust the lengths, but I'd recommend a strlen approach to output of text strings, just like you'd do in C.

I modified your code to add an fputs function that has the strlen as an internal loop [please pardon the gratuitous style cleanup]:

    .data

fout:       .asciiz     "testout.txt"   # filename for output
buffer:     .asciiz     "The quick brown fox jumps over the lazy dog."
nl:         .asciiz     "\n"

    .text
    .globl  main

main:

    ###############################################################
    # Open (for writing) a file that does not exist
    li      $v0,13                  # system call for open file
    la      $a0,fout                # output file name
    li      $a1,1                   # Open for writing (flags are 0: read, 1: write)
    li      $a2,0                   # modeA is ignored
    syscall                         # open a file (file descriptor returned in $v0)
    move    $s6,$v0                 # save the file descriptor

    ###############################################################
    # Write to file just opened

    # output string the first time
    la      $a1,buffer
    jal     fputs

    # output newline
    la      $a1,nl
    jal     fputs

    # output string the second time
    la      $a1,buffer
    jal     fputs

    # output newline
    la      $a1,nl
    jal     fputs

    ###############################################################
    # Close the file
    li      $v0,16                  # system call for close file
    move    $a0,$s6                 # file descriptor to close
    syscall                         # close

    li      $v0,10
    syscall

# fputs -- output string to file
#
# arguments:
#   a1 -- buffer address
#   s6 -- file descriptor
#
# registers:
#   t0 -- current buffer char
#   a2 -- buffer length
fputs:
    move    $a2,$a1                 # get buffer address

fputs_loop:
    lb      $t0,0($a2)              # get next character -- is it EOS?
    addiu   $a2,$a2,1               # pre-increment pointer
    bnez    $t0,fputs_loop          # no, loop

    subu    $a2,$a2,$a1             # get strlen + 1
    subiu   $a2,$a2,1               # compensate for pre-increment

    move    $a0,$s6                 # get file descriptor
    li      $v0,15                  # syscall for write to file
    syscall

    jr      $ra                     # return

---

UPDATE:

I used your code mars still exists there is no new line to be printed. mars ignores the new line and treat it as a null value.

I'm not sure what is happening on your end. I had tested this in mars and the code is correct. Here is the hex dump of testout.txt [which I had verified before posting]:

00000000: 54686520 71756963 6B206272 6F776E20  The quick brown
00000010: 666F7820 6A756D70 73206F76 65722074  fox jumps over t
00000020: 6865206C 617A7920 646F672E 0A546865  he lazy dog..The
00000030: 20717569 636B2062 726F776E 20666F78   quick brown fox
00000040: 206A756D 7073206F 76657220 74686520   jumps over the
00000050: 6C617A79 20646F67 2E0A               lazy dog..

By contrast, the hex dump for your original code was:

00000000: 54686520 71756963 6B206272 6F776E20  The quick brown
00000010: 666F7820 6A756D70 73206F76 65722074  fox jumps over t
00000020: 6865206C 617A7920 646F672E 000A0A54  he lazy dog....T
00000030: 68652071 7569636B 2062726F 776E2066  he quick brown f
00000040: 6F78206A 756D7073 206F7665 72207468  ox jumps over th
00000050: 65206C61 7A792064 6F672E             e lazy dog.

The only thing I can think of that might make a difference is the OS. I'm using linux. What is your OS? Windows? If so, the nl might need to be:

nl:   .asciiz    "\r\n"

All other OSes should be fine.