Print triangle of multidigit number in assembly x86

Question

I have to do o program which read a number between 0 and 255 and print a half pyramid, like this:

input: 4

output:

1
1 2
1 2 3
1 2 3 4

I've managed to do it for numbers between 0 and 9, but i really can't do it for two or three digits numbers.

See the following code

.model small
.stack 100h

.data
    msg db "Enter the desired value: $", 10, 13
    nr db ?

.code
    mov AX, @data
    mov DS, AX

    mov dl, 10
    mov ah, 02h
    int 21h
    mov dl, 13
    mov ah, 02h
    int 21h

    mov DX, OFFSET msg
    mov AH, 9
    int 21h
    xor ax, ax

    mov ah, 08h                 
  int 21h


  mov ah, 02h   
  mov dl, al
  int 21h   

 sub al,30h  
  mov ah,10
  mul ah                

  mov [nr],al         

  mov ah, 08h 
  int 21h   



  mov ah, 02h         
  mov dl, al
  int 21h

  sub al, 30h         
  add [nr], al 


    sub nr,30h

    mov dl, 10
    mov ah, 02h
    int 21h
    mov dl, 13
    mov ah, 02h
    int 21h

    mov cx,1

    mov bx,31h
    mov ah, 2
    mov dx, bx
    int 21h 

loop1:
    xor ax, ax
    mov al, nr
    cmp ax, cx
    je final

    mov dl, 10
    mov ah, 02h
    int 21h
    mov dl, 13
    mov ah, 02h
    int 21h

    mov bx, 0             

loop2:  
    inc bx               
    add bx,30h
    call function
    int 21h 
    sub bx,30h
    cmp bx, cx           
    jne loop2

    inc bx               
    add bx,30h
    mov ah, 2
    mov dx, bx
    int 21h 

    inc cx
    jmp loop1


    function:   


    MOV BX,10 

ASC2:
        mov dx,0            ; clear dx prior to dividing dx:ax by bx
        DIV BX              ;DIV AX/10
        ADD DX,48           ;ADD 48 TO REMAINDER TO GET ASCII CHARACTER OF NUMBER 
        dec si              ; store characters in reverse order
        mov [si],dl
        CMP AX,0            
        JZ EXTT             ;IF AX=0, END OF THE PROCEDURE
        JMP ASC2            ;ELSE REPEAT

EXTT:
        mov ah,9            ; print string
        mov dx,si
        int 21h

final:
    mov AH,4Ch   ; Function to exit
    mov AL,00    ; Return 00
    int 21h
end

Possible duplicate of [Print triangle of numbers in assembly x86](http://stackoverflow.com/questions/41743509/print-triangle-of-numbers-in-assembly-x86) — Bo Persson, Jan 20 '17 at 10:48

score 0 · Answer 1 · answered Jan 20 '17 at 14:53

(each paragraph below it's one bug/problem, to be addressed ... maybe you should start from scratch and try to write something more elegant, because this is a bit "messy")

What is sub nr,30h (after add [nr], al)? Can you explain, what it does? Try to imagine, what value is in the [nr] and what will that sub do to it. You have to decide, whether you work with numerical values, or ASCII characters, don't mix the two together mindlessly.

Move those "new line" sequences into separate procedure, so you can do call newline instead of those 6 lines, it will make easier to read the source, plus you can wrap them around with push/pop to preserve register values.

Why ah=8, int 21h input char, when you then output it? You can use ah=1 "with echo" input then.

add bx,30h
call function

^^ again, if bx is numerical value like 15, adding '0' to it before conversion to ASCII doesn't make sense. It will turn the 15 into 63, and display "63" (if your "function" is correct - it is not).

int 21h after call function does WHAT?

The function: will not return.

The function: works like argument was in ax, but the main code is calling it with bx I guess... nevertheless, bx content will be destroyed, while main code doesn't expect that.

etc...etc... too much of it. Just delete it, and start over. Stop adding random instructions to code, first make sure you have high-level overview and clear idea, what you want to do with which value and why, then write only instructions doing that. Verify in debugger often, that 2-6 new lines do what you EXPECT (because they will very likely not). "Adding just bunch of instructions and modifying them a bit, until it will work" approach may work in some high level language, but in Assembly there's million of possibilities with only 20 instruction long code, so it may take years. Rather focus to KNOW what you expect, so you can then easily compare state of debugger with your expectations, and find any discrepancy.

Print triangle of multidigit number in assembly x86

1 Answers1