Counting zeros in an 8086 array
I wrote this code to count the number of zeros in the vec array:
.model small
.stack 100h
.data
vec dw 1,2,0,3,0,4,5,6,0,0,5
m1 dw 0
.code
mov ax,@data
mov ds,ax
mov di,1 ;di is our running index
number_of_zeros:
mov ax,vec[di]
cmp ax,0
je increment_m1 ;case its zero
inc di;case its not zero
cmp di,11
jl number_of_zeros
cmp di,11
je end
increment_m1:
inc m1
inc di
cmp di,11
jl number_of_zeros
cmp di,11
je end
end:
mov ax,m1
It doesn't display the correct output. I expect to see AX = 4, but instead, when the program is finished, I see AX = 3.
I think the problem has to do with the way I access the individual elements in the array. For some reason I can't figure it out, the first iteration says that vec [1] = 0200
Edit: Ok I'm fixing the code, it does indeed give the desired output, BUT ... It still shows weird values for vec [di]. I still think I am accessing it the wrong way and I got the correct result due to chance. I would like someone to view it.
source to share
There are three problems and many ways to improve your solution, I just mentioned the fixes:
- the first element of the array is offset
0
, not1
- each item is sized
2
, not1
- the comparison for the end condition needs to be updated (for reasons 1 and 2).
So this line
mov di,1 ;di is our running index
Should be
mov di,0 ;di is our running index
and this line
inc di;case its not zero
it should be
add di,2 ;case its not zero
and this line
cmp di,11
it should be
cmp di,20 ; last element is at offset sizeof(dw) * (num_elements-1) = 2 * (11-1) = 20
This should make it work.
source to share