<ol class="carousel-indicators">
      <li data-target="#main_display" data-slide-to="0" class="active"></li>
      <li data-target="#main_display" data-slide-to="1"></li>
      <li data-target="#main_display" data-slide-to="2"></li>
      <li data-target="#main_display" data-slide-to="3"></li>
  </ol>

  <div class="carousel-inner" role="listbox">
      <div class="item active">
          <img class="d-block w-100" src="/lib/exe/fetch.php?media=slider1.jpg" alt="First slide">
      </div>
      <div class="item">
          <img class="d-block w-100" src="/lib/exe/fetch.php?media=slider2.jpg" alt="Second slide">
      </div>
      <div class="item">
          <img class="d-block w-100" src="/lib/exe/fetch.php?media=slider3.jpg" alt="Third slide">
      </div>
      <div class="item">
          <img class="d-block w-100" src="/lib/exe/fetch.php?media=slider4.jpg" alt="Fourth slide">
      </div>
  </div>

  <a class="left carousel-control" href="#main_display" role="button" data-slide="prev">
      <span class="glyphicon glyphicon-chevron-left" aria-hidden="true"></span>
      <span class="sr-only">Previous</span>
  </a>
  <a class="right carousel-control" href="#main_display" role="button" data-slide="next">
      <span class="glyphicon glyphicon-chevron-right" aria-hidden="true"></span>
      <span class="sr-only">Next</span>
  </a>