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.