Apparatus and method for defining I/O devices connected to terminals of a distributive data processing system and for downloading programs from a control computer into said terminals. A global listing containing identities of all devices that can be coupled to the terminal is prepared at each terminal. A configuration list of devices which are actually coupled to the terminal is derived from the global list. The configuration list is stored at the terminal and at the control computer. Thereafter, only programs that are required for controlling the devices that are actually coupled to the terminal are downloaded into the terminal.