/*繪制矩形*/
 void drawrectangle()
 {  
   int x1,x2,y1,y2;
   int driver,mode;
    driver=DETECT;
    mode=0;
    initgraph(&driver,&mode,"");
    Lineset();
 do
 {
  printf("請輸入矩形左上角坐標(x1,y1)及右下角坐標(x2,y2):\n注意(0<x<640,0<y<480)\n");
  scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
 }
   while(x1<0 || x1>640 || x2<0 || x2>640 || y1<0 || y1>480 || y2<0 || y2>480);
   clrscr();
   bar(x1,y1,x2,y2);
   getch();
   closegraph();
   clrscr();

 }