A concatenated stream is an input stream which is a composite stream of zero or more other input streams, such that the sequence of data which can be read from the concatenated stream is the same as the concatenation of the sequences of data which could be read from each of the constituent streams.
Input from a concatenated stream is taken from the first of the associated input streams until it reaches end of file_1; then that stream is discarded, and subsequent input is taken from the next input stream, and so on. An end of file on the associated input streams is always managed invisibly by the concatenated stream—the only time a client of a concatenated stream sees an end of file is when an attempt is made to obtain data from the concatenated stream but it has no remaining input streams from which to obtain such data.