The terms directory and folder are used interchangeably to describe a place to store information. Prior to the introduction of Windows, files were stored in directories and sub-directories utilizing a "tree" structure. While this tree structure still exists in the graphical Windows environment, the terminology has changed from directories to folders. Files are now referred to as documents. A sub-folder is simply a folder within a folder. These names are now used somewhat interchangeably. Files, directories, and folders are discussed more thoroughly in a later section.

Windows 3.1 and DOS file names are limited to eight letters plus a three-letter suffix called an extension (this DOS format is referred to as the "8.3 convention"). Windows 98 and later versions allow extended filenames of up to 255 characters. Folder names use the same rules as file names.

The characters / \ ; : * ? " < > should not be used because they are associated with special functions when executing commands from a prompt. Legal or allowable characters include all other characters and numbers available on a standard computer keyboard.

Uppercase characters are treated the same as lowercase in Windows. A file named "BOB.TXT" is the same as a file named "bob.txt". This is not true on the UNIX OS. UNIX treats filenames more uniquely so "BOB.txt" and "bob.txt" are two different files.

Drive Letters
Drive letters use the 26 letters of the alphabet followed by a colon. A: and B: are reserved for floppy drives, C: for the hard drive, and D: for the CD-ROM or DVD-ROM in most systems. The My Computer window lists all the hard disks, floppy disks, CD-ROMs, DVD-ROMs, and network drives that are part of the computer or that can be accessed over a network. Care should be taken when making drive letter assignments, since many DOS and Windows programs make references to a specific drive letter. If multiple hard drives are listed, the second physical hard drive will assume the letter D and the designations for the CD-ROM, DVD-ROM and other devices will be changed.

With Windows 98, in addition to each drive being assigned a drive letter, it can optionally be assigned a name called a drive label. The drive label can be up to 11 characters in length.