.MODEL SMALL
.STACK
.DATA
    msg1  db '1+2+...+$'
    odoa  db 0dh,0ah,'$'
    t1    db 20 dup (?)
    tt    db 20 dup (?)
    oper  db 120
    tmp   db ?
    tab   db '0123456789'
.CODE
    MOV   AX,@DATA
    MOV   DS,AX
;
    lea   dx,msg1
    mov   ah,09
    int   21h
;
    xor   si,si
    xor   ax,ax
    lea   bx,tab
    mov   dl,10
    mov   al,oper
    mov   tmp,al
;
cont:
    idiv  dl
    mov   tmp,al      ;  ah is the remainder, al is the quotient
    mov   al,ah
    xlat
    mov   tt[si],al
    inc   si
    xor   ax,ax
    mov   al,tmp
    cmp   al,0
    je    final
    jmp   cont
;
final:
    mov   tt[si],'$'
    lea   dx,tt
    mov   ah,09
    int   21h
;
    mov   dl,'='
    mov   ah,02     ; print '='
    int   21h
;
    lea   dx,odoa
    mov   ah,09
    int   21h
;
    mov   ah,4ch
    int   21h
END