If you take the time to browse through the folders of nearly any game that's installed on your hard drive, you will see lots of files with interesting extensions: mpq, pk3, dat, upk, and so on. What you most likely will not find are images, models, sounds, or scripts. But then you start the game and everything appears on the screen and runs perfectly fine—why is that?

As you may have already guessed, it has something to do with these strange files that are carrying even stranger name suffixes. These files are containers, hiding away the game resources from the end user. Basically, they are similar to ZIP or RAR archives. Most of them are using a proprietary file format that sometimes even resembles a small file system, just as it might be implemented in an operating system.

Besides the obfuscation of resources, such file containers provide at least two more very important advantages over distributing assets openly. The first one concerns the installation process...