This intrinsic is used for one specific purpose: determining whether a pair of
files (input file and list file) is interactive, duplicative, or both.
Interactive means that the file requires human intervention for all input
operations. For example, an input file and a list file opened to the same
terminal would form an interactive pair. Duplicative means that all input to
the input file is echoed automatically to the list file. For example, input to
a keyboard is duplicated on the associated CRT.
The FRELATE intrinsic has two required parameters: infilenum is the file number
of the input file, and listfilenum is the file number of the list file. Both
of these numbers are returned when you create the files using HPFOPEN or FOPEN.
The intrinsic returns a 16-bit unsigned integer. If the files are an
interactive pair, bit (15:1) =1, or =0 if they are not. If the files are a
duplicative pair, bit (0:1) =1, or =0 if they are not.
A file can be interactive, duplicative, or both. These attributes do not
change between the time the files are opened and the time they are closed. You
can use FRELATE to obtain information about files on all devices.
