A host device supplying, via a hub, different picture signals to projectors connected to ports, respectively, of the hub, executes a correlation process to obtain port numbers of the ports, respectively, and serial numbers of the projectors, with the port numbers correlated with the serial numbers; an enumeration process to enumerate display devices, respectively, to obtain display device information of each of the display devices, and to obtain the serial numbers of the projectors in accordance with an order in which the display devices were enumerated; and an array generation process to collate the serial numbers obtained by the correlation process to the serial numbers obtained by the enumeration process to store, in array elements, the display device information in an order identical to an order of the collated serial numbers, based on a numerical order of the port numbers obtained by the correlation process.