Counting spaces in a string, it prints the string and CX stays 0. assembly 8086

Question

.model  small
.stack  100H
.data

A   db   '   this is    a test $'

.code  

    mov ax, @data
    mov ds, ax 

    mov si, 0
    mov cx, 0  

myloop: 

    cmp A[si], '$'
    je final

    cmp  A[si], ' '   
    inc si
    je count
    jmp myloop

count:

    inc cx
    jmp myloop

final:

    mov dx, cx
    mov ah, 9
    int 21h

end

Click "edit" below your question, select all your code, click the button with the curly braces, save your question. — Jose Manuel Abarca Rodríguez, Jun 06 '16 at 21:09
Also, comment your code and learn to use a debugger. Furthermore `int21/09` expects a pointer to a string, it will not print a number. — Jester, Jun 06 '16 at 21:11
You need to convert CX into string = http://stackoverflow.com/questions/37605815/how-can-i-print-0-to-100-in-assembly-language-in-emu-8086/37618809#37618809 — Jose Manuel Abarca Rodríguez, Jun 06 '16 at 21:13
Note that `inc si` affects the `Z` flag, and destroys the result of the comparison `cmp A[si], ' '`. So the following `je count` is not testing what you think it does. — Weather Vane, Jun 06 '16 at 21:59
...and since `si` started at `0` incrementing it will cause "not zero" so you won't ever count any spaces. — Weather Vane, Jun 06 '16 at 22:19

Tommylee2k · Accepted Answer · 2016-06-08T06:58:26.207

0

you override the flags for the "is blank" comparison by the subsequent "inc si"

.model  small
.stack  100H
.data

A   db   '   this is    a test $'

.code  

    mov ax, @data
    mov ds, ax 

    mov si, 0
    mov cx, 0  

myloop: 

    cmp A[si], '$'
    je final

    cmp  A[si], ' '   
    jne do_not_count   ; skip count if it's not a blank

count:
    inc cx             ; it is a blank, count it

do_not_count:
    inc si
    jmp myloop

final:

    ;mov dx, cx                     ; this does NOT print CX
    ;mov ah, 9
    ;int 21h

    mov dl, cl                      ; workaround: this works for cx < 10
    add dl, '0'
    mov ah, 2
    int 21h

end

edited Jun 08 '16 at 06:58

answered Jun 07 '16 at 09:13

Tommylee2k

2,683
1
9
22

This still does not print a number, as commented above. – Weather Vane Jun 07 '16 at 17:13
you're right. to do this, in "final" CX must be converted to a decimal string, and this has to be printed. – Tommylee2k Jun 08 '16 at 06:55
the OP didn't really state what exactly he wanted. If his problem is "CX stays 0", counting the spaces is the solution, not printing CX ;) – Tommylee2k Jun 08 '16 at 07:04

Counting spaces in a string, it prints the string and CX stays 0. assembly 8086

1 Answers1