Back in school I helped write a file system based on ramfs that used the ram in all of the computers in our lab as one big shared super fast hard disk. It was a great learning experience.

I wouldn't say it's necessary for every programmer to know how the linux vsf system works and how files, directories and links are stored behind the scenes, but it is really interesting. Here's a good description of vfs http://www.mjmwired.net/kernel/Documentation/filesystems/vfs... . The implementation in ramfs is pretty simple (compared to ext3). You can find it in your kernel source in fs/ramfs/inode.c. Theres a function in there called ramfs_mkdir that allocates and configures a new inode. Anyway, thats how i'd answer the question.