setviewport

#include<graphics.h>
#include<conio.h>
 
main()
{
   int gd = DETECT, gm, midx, midy;
 
   initgraph(&gd, &gm, "C:\\TC\\BGI");
 
   midx = getmaxx()/2;
   midy = getmaxy()/2;
 
   setviewport(midx - 50, midy - 50, midx + 50, midy + 50, 1);
   circle(50, 50, 55);
 
   getch();
   closegraph();
   return 0;
}