display_lines.push(current_display_line);
$("#pv").html(print_pv(display_lines.length - 1));
display_line_num = display_lines.length - 1;
display_lines.push(current_display_line);
$("#pv").html(print_pv(display_lines.length - 1));
display_line_num = display_lines.length - 1;