Close the active input , output or error stream.

This procedure closes the file that is currently associated with the given stream. The file preceding the closed file (in the order of opening) is then assigned to the corresponding stream. A file that is closed with this procedure must previously have been opened with fopen. This function has no effect if the corresponding stream is not associated with any explicitly opened file ( i.e. it is not possible to close the default input, output or error streams). All open streams are automatically closed when the program terminates.

fflush, fopen, fselect, getfid, iseof.