Sorry, Darrel. What I meant was G_get_default_window(window). After I sent out the email, I realized that. I forgot I had a copy of GRASS program manual with me here. You know I should have brought more with me. Oh, I try to use D_get_u_north() (also for other three). But it won't compile for me. I recall they're GRASS funs, aren't they? --Xin