INT 15h,  81h (129)      Device Close                                    many

    Provides an interface to close a device with a specific process.

       On entry:      AH         81h
                      BX         Device ID
                      CX         Process ID

       Returns:       Carry      Set if service not supported, else cleared

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       Notes:         The PC, PCjr, and the XT dated 11/08/82 do not
                      support this service.

                      This interface is supported for multi-tasking
                      environments, where more than one process (or task)
                      may be executing in the system. Usually the
                      operating system will supply the handler for this
                      service; this way, the operating system can keep
                      track of which processes are using each device on
                      the system.

                      The operating system will use this service to
                      discontinue the use of a device by a process.