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Files, Directories, Paths and the Directory Tree

The basis for the storage model on the PC, at a logical level, is the file. The universal concept of the file is one of the strengths of the PC file system, and is one that the PC shares with many other successful file systems such as that used by UNIX (of course, UNIX predates the PC by over a decade!) A file is simply a collection of bytes stored together with a name to identify it. A file can contain anything: program code, data, pictures, a movie, you name it. The meaningfulness of a file, and what it is used for, is determined by what you put in it, and what software you use with it. Even the file extension doesn't distinguish a file; it is just a naming convention.

As you probably know, files are stored in virtually every PC-based operating system using a paradigm known as the directory tree. The "base" of the tree is the (somewhat appropriately named) root directory. Within the root directory you can create either simple files or more directories (often called subdirectories). Each directory is a container that holds files or more subdirectories (or both). The directories can be "nested" to many levels of depth. Taken as a whole, the structure of directories and subdirectories forms a logical tree. (Well, it actually looks like the root structure of a tree. The "root" and "branch" analogies are used interchangeably in the computer world, much to the confusion of some arborists. :^) )

Each file or directory on the hard disk can be uniquely identified using two pieces of information: its filename, and the path along the directory tree that you traverse to get to it. For example, let's suppose you have a set of customer information files organized by region. The entire database is in a directory called "Customers" on the "D:" logical drive. Within this is a directory for each state. Within each of these state directories is a text file called "customer-list.txt". The file containing information about your customers in Texas would then be addressed as "D:\Customers\Texas\customer-list.txt". The filename is "customer-list.txt", and the path is "D:\Customers\Texas".

Note: Windows sometimes calls directories "folders". They are exactly the same thing.

Next: Internal Directory Structures

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