Used by the routine at E11E.

any logical file that has already been opened by the OPEN routine, FFC0, can be defined as an input channel by this routine. the device on the channel must be an input device or an error will occur and the routine will abort.

if you are getting data from anywhere other than the keyboard, this routine must be called before using either the CHRIN routine, FFCF, or the GETIN routine, FFE4. if you are getting data from the keyboard and no other input channels are open then the calls to this routine and to the OPEN routine, FFC0, are not needed.

when used with a device on the serial bus this routine will automatically send the listen address specified by the OPEN routine, FFC0, and any secondary address.

possible errors are:

• 3 : file not open
• 5 : device not present
• 6 : file is not an input file