INT 15 C - OS HOOK - DEVICE CLOSE AH = 81h BX = device ID CX = process ID CF clear Return: CF clear if successful AH = 00h CF set on error AH = status (see #00496) Note: this function should be hooked by a multitasker which wishes to keep track of device ownership; the default BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware. The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. handler merely returns successfully SeeAlso: AH=80h,AH=82h