.386
.model flat,c
.STACK 100h

.data
bufferPtr dword 0
bufferHandleLow word 0
bufferHandleHigh word 0

.code

main PROC
  ; we need es the same as ds for movsb
  mov ax,ds
  mov es,ax

  ; place to catch bpint
  mov cx,0fh
  mov dx,1
  mov ah,86h
  int 15h

  ; reserve ram
  mov ax,0501h
  mov bx,0
  mov cx,64000
  int 31h
  shl ebx,16
  mov bx,cx
  mov bufferPtr,ebx
  mov bufferHandleLow,di
  mov bufferHandleHigh,si

  ; clear ram
  mov ecx,64000
  mov edi,ebx
  mov al,0
  rep stosb

  ; write pixel 15 at (10,10)
  mov edi,ebx
  add edi,320*10+10
  mov al,15
  stosb

  ; switch to 320x200 256 color chunky chained mode
  mov ah,0h
  mov al,13h
  int 10h

  ; copy buffer to vga card
  mov esi,bufferPtr
  mov edi,0a0000h
  mov ecx,320*200
  rep movsb

  ; wait 5s
  mov cx,0fh
  mov dx,5000
  mov ah,86h
  int 15h

  ; free memory
  mov ax,0502h
  mov si,bufferHandleHigh
  mov di,bufferHandleLow
  int 31h

  ; terminate with return code
  mov ah,4Ch
  mov al,00h
  int 21h
main ENDP

END main