A diagram of cylinders/tracks and sectors on a platter. Also, a diagram of four (4) stacked platters, and eight (8) read/write heads.
<a href="//commons.wikimedia.org/wiki/User:LionKimbro" title="User:LionKimbro">LionKimbro</a>
<span class="int-own-work" lang="en">Own work</span>