Any logical file number that has been created by the OPEN routine can be defined as an input channel. Of course, the device you intend opening a channel to must be an input device. Otherwise, an error will occur, and the routine will be aborted.

If you are getting data from anywhere other than the keyboard, this routine must be called before using either the CHRIN or the GETIN routines for data input. If you want to use the input from the keyboard, and no other input channels are opened, then the calls to this routine, and to the OPEN routine are not needed.