Int 15 Fn 80  C - OS Hook - Device Open (at,xt286,ps)                      [B]

   AH = 80h
   BX = device ID
   CX = process ID
   CF clear

Return: CF clear if successful
       AH = 00h
   CF set on error
       AH = status
       80h invalid command (PC,PCjr)
       86h function not supported (XT)

Note:  this function should be hooked by a multitasker which wishes to keep
     track of device ownership; the default BIOS handler merely returns
     successfully

See Also: AH=81h,AH=82h