gerard ROBIN - 2013-02-12

When I run this program:

(defpackage :system-examples
  (:use :common-lisp

(in-package :system-examples)

(defparameter gdev "xfig")  ; (was aqt) set this to the appropriate plplot device for your system

(defun my-make-array (dims)
  (make-array dims :initial-element 0.0 :element-type 'float))

(defun plot ()
  (plsdev gdev)
  (plcol0 1) ;; color of the frame
  (plwid 1) ;; largeur du trait cadre, courbe, …
  (plenv -6 6 0 36 0 0)
  (plcol0 2)
  (pllab "(x)" "(y)" "y = x#u2")
  (let ((x (my-make-array 121))
(y (my-make-array 121)))
    (dotimes (i 121)
      (let ((tmp (* 0.1 (- i 60)))) ;; abscisses des points de la courbe
       (setf (aref x i) tmp)
       (setf (aref y i) (* tmp tmp)))) ;; ordonnees des points de la courbe

    (plcol0 3)  ;; color de la courbe

    (plline x y))


I get : Enter graphics output file name:

How can I avoid this message?  what I want is that the result is automatically stored in a file whose name is given by the program.