program plot_auto_scale
      character*20 fname
      write(*,*)'Filename?(20 chr max)'
      read(*,*)fname
      open(unit=10,file=fname)
      read(10,*)n
      do i=1,n
        read(10,*)x,y
        if(i==1)then
           xmax=x
           ymax=y
           xmin=x
           ymin=y
         else
           if(x>xmax)xmax=x
           if(y>ymax)ymax=y
           if(x<xmin)xmin=x
           if(y<ymin)ymin=y
        end if
      end do  
      i_dummy=pgopen('/xwin')
      call pgenv(xmin,xmax,ymin,ymax,0,0)
      rewind(10)
      read(10,*)n_dummy
      do i=1,n
        read(10,*)x,y
        call pgpt(1,x,y,20)
      end do
      call pgclos
      end