making a rectangular star shape with 8086 assembly

Question

I'm trying to make a rectangular star shape with 8086 assembly using 1 loop and making the outer one with cmp to 0 and jne the code is below.

Here's my code:

.model small
.stack 100h
.data
ml db 'how many lines you want',13,10,'$'
ms db 'how many stars in each line',13,10,'$'
lines db 0
stars db 0

nl db 13,10,'$'
.code
Main Proc
mov ax, @data
mov ds, ax

mov dx, OFFSet ml
mov ah,9h
int 21h

mov ah,1h
int 21h

sub al,'0'

mov [line],al
int 21h

xor ah,ah

mov dx, OFFSet ms
mov ah,9h
int 21h

mov ah,1h
int 21h

sub al,'0'

mov [stars],al
int 21h

mov cx,[stars]
int 21h


outer:
dec [line]
mov cl,[stars]
int 21h
inner:
mov dl, '*'
mov ah, 2h
int 21h
loop inner

mov dx, OFFSet nl
mov ah,9h
int 21h

cmp [line],0
jne outer

 MOV AH,4CH
 INT 21H

Main ENDP
END Main

Answer 1

a recktagular star shape

It is true that this wording is confusing, but the code clearly wants to draw a rectangle made out of asterisks.

The good news is that your nested loops are rather fine. However you have written lots of redundant int 21h instructions that serve no real purpose and are harmful. To be removed.

A big problem is that you are loading the CH register with a non-zero value and as a consequence, the first run of the inner loop will draw too many stars.

 stars db 0 nl db 13,10,'$'

The mov cx,[stars] instruction not only loads stars in CL but also it loads the number 13 in CH .

This is a cleaned version of your code:

mov dx, OFFSet ml
mov ah, 09h
int 21h

mov ah, 01h
int 21h
sub al, '0'
mov [line], al

mov dx, OFFSet ms
mov ah, 09h
int 21h

mov ah, 01h
int 21h
sub al, '0'
mov [stars], al

outer:
  mov  cl, [stars]
  mov  ch, 0                  <<<<< Because LOOP uses CX
inner:
  mov  dl, '*'
  mov  ah, 02h
  int  21h
  loop inner
  mov  dx, OFFSet nl
  mov  ah, 09h
  int  21h

  dec  [line]
  jnz  outer

Instead of dec [line] and cmp [line], 0 , you can conditionally jump ( jnz outer ) based on the Zero Flag that is already defined by the dec instruction.

---

It's just as easy to not use LOOP at all (because later you'll have to un-learn it, really)

outer:
  mov  cl, [stars]
inner:
  mov  dl, '*'
  mov  ah, 02h
  int  21h
  dec  cl                  <<<<<<
  jnz  inner               <<<<<<
  mov  dx, OFFSet nl
  mov  ah, 09h
  int  21h

  dec  [line]
  jnz  outer