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
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.