program read_range_plot
      character*20 user_filename

      write(*,*)'Which file to plot?'
      read(*,*)user_filename

      open(unit=10,file=user_filename)

      read(10,*)n

      read(10,*)x,y
      xmin=x
      xmax=x
      ymin=y
      ymax=y
      do i=1,n-1
        read(10,*)x,y
        if(x>xmax)xmax=x
        if(x<xmin)xmin=x
        if(y>ymax)ymax=y
        if(y<ymin)ymin=y
      end do

      close(10)
      open(unit=10,file=user_filename)
C     rewind(10)
      read(10,*)n

      if(pgopen('/xwin')<=0)stop
      call pgenv(xmin,xmax,ymin,ymax, 0,0)

      do i=1,n
        read(10,*)x,y
        call pgpt(1,x,y,20)
      end do

      call pgclos

      end