| tsgrimey |
Feb 8th, 2005 9:36 PM |
SPIM Assembly Programming Simulation Problem
I'm trying to get this small program to work properly, but having problems. All its suppose to do is read in a string from a user, then output to console with the characters reversed. I also must mention that I can only change the code between "now reverse code here"...and..."not beyond here". Anyone know how to solve this? :(
:
# reverse --- Read and echo a reversed copy of it to the console
.data
line: .space 80
reversed_line: .space 80
prompt: .asciiz "Enter a line to be echoed.\n"
nl: .asciiz "\n"
.text
.globl main
main:
li $v0, 4 # Syscall code for print string.
la $a0, prompt # Starting address of string.
syscall
li $v0, 8 # Syscall code for read string.
la $a0, line # Starting address of buffer.
li $a1, 80 # Length of buffer.
syscall
li $v0, 4
la $a0, nl
syscall
li $v0, 4
la $a0, line
syscall
# now reverse it your code should go here
la $s2, reversed_line
addi $s2, $s2, 79 # end of str2
addi $t1, $zero, 0 # null
sb $t1, 0($s2)
addi $s2, $s2, -1
lb $t2, nl # newline
sb $t2, 0($s2)
la $s1, line
loop:
lb $t1, 0($s1) # read char from str1
beq $t1, $t2, done # '\n' - end of str1 ?
addi $s2, $s2, -1 # update str2 pointer
sb $t1, 0($s2) # write to str2
addi $s1, $s1, 1 # update str1 pointer
j loop
done:
# and not beyond here
# now print the reversed string
li $v0, 4
la $a0, reversed_line
syscall
li $v0, 4
la $a0, nl
syscall
j main
li $v0, 10 # Syscall code for exit.
syscall
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