All of these files can be viewed using CrystalMaker. You can download a free demo of CrystalMaker, which will allow you to open these files and play around with them. It won't allow you to save new files.
If you want to view more atoms in these structures, go to the Transform menu, select Set Range, and then click on Expand until the number of "atoms in range" is as desired.
Hexagonal Close Packed (HCP) Structure.