Int 50 Fn 0003  - Vanderaart Text Windows - Output Line To Window          [V]

   AX = 0003h
   ES:BX -> text string
   CX = string length (0000h if ASCIZ string)
   DL = position (FFh centered, else flush left)
   DH = starting row
   DI = window handle

Return: AX = status
       0000h successful
       FFFFh did not fit in window