(求助)图形程序问题

#include <graphics.h>
main()
{
int gdriver,gmode,i;
gdriver=DETECT;
registerbgidriver(EGAVGA_driver);
initgraph(&gdriver,&gmode,"");
setbkcolor(0);
cleardevice();
for (i=0;i<15;i++);
    {
     setbkcolor(i);
     circle(320,240,20+i*10);
     delay(100);
    }
for (i=0;i<15;i++)
    {
     cleardevice();
     setcolor(i);
     circle(320,240,20+i*10);
     delay(100);
    }
closegraph();
return 0;
}
当我运行完这个程序的时候怎么不能正常退出,总是黑屏,但没死机,就是看不到屏幕
----------------解决方案--------------------------------------------------------
结尾加上exit(1);
----------------解决方案--------------------------------------------------------
#include<stdio.h>
     #include<graphics.h>
     int main()
     {
          int gdriver, gmode, i;
          gdriver=DETECT;
   registerbgidriver(EGAVGA_driver);/*建立独立图形运行程序*/
   initgraph(&gdriver, &gmode, "");/*图形初始化*/
          setbkcolor(0);                   /*设置图形背景*/
          cleardevice();
          for(i=0; i<=15; i++)
          {
            setcolor(i);                   /*设置不同作图色*/
            circle(320, 240, 20+i*10);     /*画半径不同的圆*/
     getch();                    
          }
          for(i=0; i<=15; i++)
          {
             setbkcolor(i);                /*设置不同背景色*/
             cleardevice();
             circle(320, 240, 20+i*10);
      getch();
          }
          closegraph();
          return 0;
     }
----------------解决方案--------------------------------------------------------
我觉得registerbgidriver()没必要
----------------解决方案--------------------------------------------------------
注意initgraph()路径是否正确
----------------解决方案--------------------------------------------------------