Int 2Fh / 4B05h         Identify Instance Data                       DOS 5.0+

    Identifies instance data maintained by a client program. A task
    switcher calls this function to create a linked list of instance
    data blocks for all client programs running on the system. Client
    programs with instance data must intercept interrupt 2Fh and
    process function 4B05h when they receive the function call.

        Entry   AX    = 4B05h
                ES:BX = 0000:0000h
                CX:DX = Address of service-function handler

        Return  ES:BX = Pointer to a SwStartupInfo structure
                or
                ES:BX = 0000:0000h

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