asm

di=(yCOLS+x)4

setup:
    mov ax,0x0c00
    push ax
    pop es       ; es=0x0c00  vram (Sanyo MBC555)
    xor di,di    ; di=0

    mov bx,20    ; bx=xpos
    mov ax,5     ; ax=ypos
setDotXY:        ; output: di=(y*COLS+x)*4
    mov cx,COLS 
    mul cx       ; y*COLS
    add ax,bx    ; +x
    shl ax,1     ; *2
    shl ax,1     ; *2
    xchg ax,di   
.setDot:         ; es:di = ax
    mov ax,0xffff
    times 2 stosw  

twt86

• http://twt86.co/?c=xSQgswcIBKfALQWRAkFeAkD8AoCcAEt18ooE%2BdLY6%2BE%3D#

online 8086 emulator

• https://yjdoc2.github.io/8086-emulator-web/

poging disassemble basic.exe (sanyo) met ndisasm

ndisasm -b16 -e1264 BASIC.EXE > tmp.lst

1264 = 0x200 + 0x2f0 (jmp 2f0)

ODA

• https://www.onlinedisassembler.com/odaweb/
• JetBrains dotPeek (.NET decompiler)

compile a com file on osx and run in dosbox

nasm -f bin first.asm -o first.com

disassemble with ndisasm

"To disassemble a DOS .COM file correctly, a disassembler must assume that the first instruction in the file is loaded at address 0x100, rather than at zero."

ndisasm -o100h filename.com

it will not understand .EXE files like debug will. It just disassembles.

hello world

from: https://github.com/nanochess

  org 0x100
start:
  mov bx,string
repeat:
  mov al,[bx]
  test al,al
  je end
  push bx
  mov ah,0x0e
  mov bx,0x000f
  int 0x10
  pop bx
  inc bx
  jmp repeat

end:
  int 0x20

string:
  db "Hello world!",0