🚀 go-pugleaf

I've got a strange problem here that I'm hoping some of you out there in
computer land can help me with.
        I wrote an interactive graphics program in FORTRAN 77 on VMS for a VAX.
The program runs nicely, producing both graphics and alphanumeric text on a
Tektronik 4105 screen.
        The problem however, is that when this file (ie the executable file)
was mailed to another user and executed, only the alphanumeric text
appeared on the screen, whereas the graphics didn't.
        It is possible that the alphanumeric output goes to unit 5 and the
graphics to unit 6, but I don't see how this should affect things as by
default both units 5 and 6 and assigned to the terminal.
        Thanks for your help!
                Eliot