I have a problem with this code. I try to enter a string by input and save it into an array, this my code:
.data
.align 2
array: .space 80
size: .word 20
string: .space 20
op: .asciiz "Enter the array length"
prompt: .asciiz "Enter a string:"
text: .asciiz "The array of string is:"
newline: .asciiz "\n"
.text
.globl main
main:
add $t0, $zero, $zero # index of array
addi $t1, $zero, 1 # counter=1
li $v0, 4
la $a0, op
syscall
jal new_line
li $v0, 5
syscall
addi $s0, $v0, 0 # $v0 contains integer read
read_string:
bgt $t1, $s0, L1 # if ($t1 > length)then go to L1
li $v0, 4
la $a0, prompt
syscall
la $a0, string
li $a1, 20
li $v0, 8
syscall
sw $a0, array($t0)
addi $t0, $t0, 4
addi $t1, $t1, 1
j read_string
L1: #### here i want to print the array ####
add $t0, $zero, $zero # index of array
addi $t1, $zero, 1 # counter=1
la $a0, text
li $v0, 4
syscall
jal new_line
while: bgt $t1, $s0, done
lw $t2, array($t0)
li $v0, 4
move $a0, $t2
syscall
jal new_line
addi $t0, $t0, 4
addi $t1, $t1, 1
j while
new_line: la $a0, newline
li $v0, 4
syscall
jr $ra
done: li $v0, 10
syscall
The trouble is that this program show me the last string that I've entered by input, for example
Enter the array length:
2
Enter a string:asd
Enter a string:123
The array of string is:
123
123
Please I need some help, thanks a lot and have a nice day.
Your array indexing logic appears to be okay, but the problem was that you were always storing every entry with the same address, the address of string. The solution is a larger string area and incrementing a pointer to it when storing the strings.
I've corrected your code [untested]. Please pardon the gratuitous style cleanup, but I needed to understand your logic before trying to fix it. I've added more comments [I'm an old time asm guy, and I always comment every line] and annotated your code with [OLD] and my replacements with [NEW].
.data
.align 2
array: .space 80
size: .word 20
###string: .space 20 # [OLD]
string: .space 20000 # [NEW]
op: .asciiz "Enter the array length:"
prompt: .asciiz "Enter a string:"
text: .asciiz "The array of string is:"
newline: .asciiz "\n"
.text
.globl main
main:
# prompt user for array length
li $v0,4
la $a0,op
syscall
jal new_line # output newline
# read in array count
li $v0,5
syscall
addi $s0,$v0,0 # $v0 contains the integer we read
add $t0,$zero,$zero # index of array
addi $t1,$zero,1 # counter=1
la $s2,string # load address of string storage area [NEW]
read_string:
bgt $t1,$s0,L1 # if ($t1 > length) then array is done -- fly
# prompt the user for next "string"
li $v0,4
la $a0,prompt
syscall
# get the string
### la $a0,string # place to store string [OLD]
move $a0,$s2 # place to store string [NEW]
li $a1,20
li $v0,8
syscall
# store pointer to string into array
sw $a0,array($t0)
addi $t0,$t0,4 # advance offset into pointer array
addi $t1,$t1,1 # advance iteration count
addi $s2,$s2,20 # advance to next string area [NEW]
j read_string
#### here i want to print the array ####
L1:
add $t0,$zero,$zero # index of array
addi $t1,$zero,1 # counter = 1
# output the title
la $a0,text
li $v0,4
syscall
jal new_line
while:
bgt $t1,$s0,done # more strings to output? if no, fly
lw $t2,array($t0) # get pointer to string
# output the string
li $v0,4
move $a0,$t2
syscall
jal new_line
addi $t0,$t0,4 # advance array index
addi $t1,$t1,1 # advance count
j while
# new_line -- output a newline char
new_line:
la $a0,newline
li $v0,4
syscall
jr $ra
# program is done
done:
li $v0,10
syscall
UPDATE For extra credit, when you get the original version working, you can try replacing addi $s2,$s2,20 with jal stradv, where stradv is:
# stradv -- advance past end of string
stradv:
ldb $t2,0($s2) # get char
addi $s2,$s2,1 # we pre-increment because we want EOS + 1
bne $t2,$zero,stradv # is it EOS? if no, loop some more
jr $ra
This would allow large variable length strings [if you also increased the length on the string read syscall].
This is how I normally would have coded something like this, but I didn't want to add this until you had the basic code fully working.