/* boxcirc.c:
A simple example which draw a 2d box and circle, press ESCape key to exit. */
#include <gl/gl.h> #include <gl/device.h>
main()
{    
int dev,val;
initialize();
   while (TRUE) {        
      if (qtest()) {            
         dev = qread(&val);            
         if (dev == ESCKEY) {
            gexit();
            exit();
         }
         else if (dev == REDRAW) {
            reshapeviewport();
            drawboxcirc();
         }
      }
   }
}
initialize()
{
int gid;
prefposition(XMAXSCREEN/4, XMAXSCREEN*3/4, YMAXSCREEN/4, YMAXSCREEN*3/4);
   gid = winopen("boxcirc");
   qdevice(ESCKEY);
   qdevice(REDRAW);
   qenter(REDRAW,gid);
}
drawboxcirc()
{
pushmatrix(); translate(200.0, 200.0, 0.0); color(BLACK); clear(); color(BLUE); recti(0, 0, 100, 100); color(RED); circi(50, 50, 50); popmatrix();
}
The circ subroutine , clear subroutine , color or colorf subroutine .