程序集 8086 中的嵌套循环（

Question

; ( iam facing problem in printing this series 122222223222) can you plz look on code and point my mistake )

.model small 
.stack 100h 
.code 
start:
mov cx,3

l1:

mov ah, 02
mov dl, 49
int 21h 
inc dl

mov bx,cx
mov cx, 3

l2:

mov ah, 02
mov dl,50
int 21h 

loop l2

mov cx,bx
inc dl
loop l1

mov ah, 4ch
int 21h 

end start

Answer 1

Your program is almost OK. The output currently is "122212221222".

That "1" character that keeps repeating, comes from the fact that you re-use the immediate value 49 within the loop where you should have kept this number outside the loop!
I suggest you store it in the DH register, retrieve it from there and increment DH on each iteration:

    mov  dh, "1"   ; ASCII=49
    mov  cx, 3
outerLoop:
    mov  ah, 02h
    mov  dl, dh    ; Successively "1", "2", "3"
    inc  dh
    int  21h

    mov  bx, 3
innerLoop:
    mov  ah, 02h
    mov  dl, "2"   ; ASCII=50
    int  21h 
    dec  bx
    jnz  innerLoop

    dec  cx
    jnz  outerLoop

Please notice that instead of using BX to preserve the outer loop counter, you can just as easily use BX as the counter for the inner loop.

For readability you can:

• use more descriptive labels
• insert blank lines to make the innner loop stand out
• write functional comments