NAME
        IsInteractive -- Discover whether a file is "interactive"

    SYNOPSIS
        status = IsInteractive( file )
        D0                      D1

        bool isinteractive(bptr)

    FUNCTION
        The return value 'status' indicates whether the file associated
        with the file handle 'file' is connected to a virtual terminal.

    INPUTS
        file - BCPL pointer to a file handle

    RESULTS
        status - boolean

    SEE ALSO