As a public service announcement, I thought I should alert my fellow class members that you DON'T have to reach around to the back of the iMac to plug in your flash drive (where you will likely forget it). Rather, Macs have hidden USB ports built right in the keyboard! Just look under the left side (as the mouse uses the right side port) and, voilà, you can plug in your flash drive right where you can see it while you work (and possibly remember it before you leave).
Hope that helps!