In a data input/output system having a plurality of input devices and a plurality of output devices, a display can be performed with a consistency maintained between an input parameter used to establish the operational condition of an input device to be used for data input and an output parameter used to establish the operational condition of an output device to be used for data output, and thereby the data input/output system, a data input/output method and a data input/output system control apparatus can be provided, wherein an optimum establishment of setting items which are related to a combination between input and output devices required in a case where a multiple of input and output devices are connected to one another can be easily done with reliability by use of a minimum number of operations and thereby eliminating erroneous operations.