Drive Letters and the File System

Chapter 2 - Drive Letters and the File System

 

If you've ever opened My Computer on Windows XP or Computer on Windows Vista or Windows 7, right away you've seen a large number of drives. Some of them might have been your computer's internal hard drives and optical drives. Others might have belonged to USB drives, like external hard drives or flash drives. Still others might have belonged to your computer's built-in media card reader, if your system has one. And if you have an old computer, you might even still have a letter assigned to a floppy drive, though floppy drives are becoming rarer and rarer. (Thankfully, in my opinion- floppy drives are slow and unreliable, and a $10 four gigabyte flash drive can hold the contents of roughly 1,500 three-and-a-half inch floppy disks.) 

Before you can use the Command Prompt effectively, you need to understand how drive letters work, and how the Windows file system is laid out. We'll address both these topics in this chapter.

 

DRIVE LETTERS

 

In the Windows operating system, every physical drive (or logical partition on a physical drive – more on those in Chapter 9) is assigned a drive letter. For instance, your first hard drive might receive the letter C, your first optical drive the letter D, and so forth. This is different from Mac OS X and Linux, where additional drives generally show up as subfolders on the hard drive – usually in the /media or the /Volumes folder (a USB flash drive with a volume label of STORAGE would show up with a drive letter on a Windows system, but as the /Volumes/STORAGE directory on a Mac).

Why use drive letters? They provide a convenient way of finding which disk is holding a particular file. If you know that the full path to a file named Book.doc is C:\Storage\Book.doc file, then you know that the file is on the C drive, which is probably the first hard drive on your system. 

Any drive can be assigned any letter. However, by tradition and convention (and in some cases technical requirements) certain letters usually get assigned to certain kinds of drives. The letters A and B are rarely used on modern Windows systems – in older DOS computers, the letters A and B were reserved for the first and second floppy drives in the system. 

The letter C is almost always assigned to the first hard drive (or hard drive partition) in a system, generally the partition or hard drive where Windows is installed. On a modern computer, you can install Windows on any hard drive with any letter. However, it is usually best to install Windows on C, since many older (and badly-written) programs expect to find Windows on the C drive, and refuse to run if Windows is installed on any other drive letter. 

The letter D, traditionally, is assigned to the first optical drive in the computer – a CD-ROM, DVD-ROM, CD-RW, or DVD-RW drive (or a drive that combines all four functions, as most modern drives do). However, on many modern laptops and desktops, the D drive is assigned to a recovery partition on the hard drive, which contains the files necessary to reinstall Windows from scratch in case of operating system corruption or irreparable virus damage. (Computer manufacturers started doing this to save on the cost of including a recovery DVD with the system.) If your system has a recovery partition on D, then your first optical drive will receive the letter of E.

After D and E, there is no generally agreed convention for which devices get which letters. As you add drives to your system, whether internal hard drives or removable USB flash drives and hard drives, Windows will assign them the next available letter. If you want a device to have a different letter, you can reassign the letter either using the Disk Management snap-in in the Computer Management console, or using the DISKPART command-line utility (more on DISKPART in Chapter 9).

 

THE PATH

 

As you work with the Command Prompt, you might notice that in order to run an executable file you need to either change to the directory containing a file, or type its full path at the prompt. However, for many of the built-in Windows commands, you can type the command in any directory, and Command Prompt will run it. Why is that?

This is something called the system path, or generally just the path, that Command Prompt uses to find commands. Basically, the path consists of a few directories set apart by Windows for storing commands. If you type a command at the prompt, Command Prompt searches the directories in the path for the command. If it doesn’t find the command in the path, it then checks the current directory. And if it doesn’t find the command there, it comes back with the usual error message:

FILENAME is not recognized as an internal or external command, operable program or batch file.

If you want to find out what your system’s path is, simply type the PATH command at the prompt:

PATH

The results will generally look something like this:

C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem

Command Prompt will search these three directories for commands. There might be other directories in your system’s path – installed programs sometimes add their directories to the path. You can also add directories to the path using the PATH command, though it’s best to do so sparingly. If you add too many commands to the path, Command Prompt will search them all to find a command, which can slow down system performance.

 

NETWORK DRIVES

 

From the days of Windows for Workgroups in the early 1990s, Windows has offered strong support for file sharing – accessing files stored in a shared folder on a remote server. It is possible to connect file shares to your computer and assign them a drive letter – a process called “drive mapping” or “mapping a network drive.” Once a shared folder has been mapped to your computer as a network drive, you can use it like any other kind of drive, copying files to and from it (though that may depend on your permissions to the shared folder). We’ll discuss network drives more in Chapter 10.

 

THE WINDOWS FILE SYSTEM

 

We’ve been talking about “directories”, but what do we mean by that term?

If you look at the root of your C drive through Windows Explorer, you’ll see a number of different folder icons. A “directory” is a virtual folder that allows you to sort and organize your files into different containers, so everything isn’t messily stored in just one folder. (In fact, in earlier versions of Windows, if you had too many items in your hard drive’s root directory, Windows mistakenly assumed that your hard drive had filled up!) 

You could put additional directories inside directories – these directories within directories are called “subdirectories.” You can put additional subdirectories within those subdirectories, as many as you wish. If you think of the root directory of your hard drive (represented by the \ character) as the trunk of a tree, then the directories and their subdirectories are branches off the main trunk. In fact, Windows includes a command that lets you view the filesystem as a tree:

TREE

Type that command at the prompt, and you will see your filesystem represented as a tree. It will quickly scroll past your screen – the modern Windows operating system contains many thousands of directories and subdirectories. In the next section, we’ll talk about some of the more important directories on your computer’s hard drive.

 

IMPORTANT DIRECTORIES

 

If you go to the root directory of your C drive (or the drive where Windows is installed), you should see a few directories. The most important of the directories is C:\Windows, which contains the system files that make up Windows itself. The Windows directory also contains the C:\Windows\system32 directory, which holds a number of important components and utilities for Windows itself. Do not delete any of the files in this directory! Doing so can disable important parts of Windows, and may even render your system unbootable. 

Also in the root directory of your C drive is the C:\Program Files folder. By default, your system’s applications install themselves here. If your computer runs a 64-bit version of Windows, you’ll also have a C:\Program Files (x86) folder, where Windows installs any 32-bit software programs. All 64-bit applications will go into the regular C:\Program Files folder on a 64-bit Windows system. If you need to uninstall a program, it’s a bad idea to simply go into the C:\Program Files directory and start deleting files – you will get better results by uninstalling an application using the Programs and Features item in Control Panel. 

The C:\Program Data directory is hidden, but contains a number of application data files and system data files. For instance, all the Start Menu shortcuts are stored in C:\ProgramData\Microsoft\Windows\Start Menu\Programs. Unless you know what you’re doing, it’s not a good idea to delete or alter files in the C:\Program Data directory. 

The root directory of C also holds the C:\Users folder. This folder contains the user profiles – the personal data – of every user who logs into the system. Go into the C:\Users folder, and you will see folders named for every user account on the system. Inside each of those folders, you will see the profile folders for the user – their Desktop folder, which holds the files on their Desktop, their Documents folder, their Pictures folder, and so forth. There are also a number of hidden directories that contain application settings, data files, user preferences, and similar files.

Generally, when working on a computer, it is always a good idea to back up the contents of the C:\Users directory. Especially if it is the personal machine of a technically unskilled user – the user will almost always claim that he or she doesn’t “have anything important” on the machine if you need to wipe the hard drive and reinstall Windows. Nevertheless, if you do wipe the machine and reinstall Windows, a few weeks later the user will become irate when he notices that “all his stuff is missing” – and of course the user has no backup copies! It is therefore always a good idea to back up the C:\Users directory when repairing a Windows computer.