Understanding Mac OS X Directories

Mac OS X includes many standard folders, often called directories in Mac OS X lingo. You have seen several of these as you learned about using the Go menu, working with Finder windows, and so on.

Some directories, such as the Mac OS X System directory, are critical to your Mac's operation, whereas others are merely organizational devices, such as the Documents directory within each user's Home directory.

There are two general groups of directories you will work with: those for the system and those for users.

Mac OS X System Directories

Two main directories provide access to Mac OS X system-level files and folders.

The Computer Directory

The Computer directory is the highest-level folder on your Mac. It shows the volumes mounted on your machine, including hard drives, drive partitions, disk images, DVDs, CD-ROMs, and so on (see Figure 4.10). The name of the Computer directory is the name of your Mac.

Figure 4.10. The Mac OS X Computer directory represents all the contents of your machine as well as the network resources you can access.


Most of the contents of the Computer directory should be familiar to you, such as volumes, CD-ROMs, and so on.

One exception to this is the Network folder, which contains the resources you can access via a network.

To learn more about the Network volume, see Chapter 26, "Building and Using a Network," p. 821.

The Mac OS X Startup Volume

One of the directories in the Computer directory is the one on which you installed Mac OS X. The name of this directory depends on what you named the volume (for example, I called mine Mac OS X).

By default, your startup volume directory contains the following four directories that are part of the Mac OS X installation:

  • Applications? Under Mac OS X, all Carbon and Cocoa applications are stored in this directory.

    To learn how to install applications, see Chapter 6, "Installing and Using Mac OS X Applications," p. 143.

  • Library? The Library folder contains many subfolders that provide resources to support applications, hardware devices, and other items you add to your Mac. This library directory contains the system folders that can be modified.

  • System? This folder contains the Library folder that provides the core operating system software for Mac OS X. The items in this folder can't be modified except by installation applications, system updaters, or using the root account.

    To learn more about the Library and System directories, see "Mac OS X to the Max: Exploring Mac OS X," p. 238.

  • Users? The Users directory contains the Home directory for each user for whom an account has been created. The Home directory of the user currently logged in has the Home icon; the Home directories for the rest of the users have plain folder icons. If you have deleted user accounts, it also contains folder called "Deleted Users" that contains a disk image for each deleted user account (if you elected to keep the user's resources when you deleted his folder).

    The Users directory also contains the Shared folder. Items placed in this folder can be accessed by any user who logs in to the Mac.


If you installed Mac OS X version 10.3 using the Archive and Install option, the startup volume also includes the Previous Systems folder, which contains the folders from the previous Mac OS X installations.

Mac OS X User Directories

As you learned in Chapter 2, each user account includes a Home folder. By default, this folder contains eight directories in which the logged-in user can store folders and files.

To learn about the specific directories in a user's Home directory, see "Understanding the Home Folder," p. 21.

Although the Home folder contains the eight default directories, you can add directories within these folders as well as create new folders within the Home folder itself.

The benefit to using the standard directories is that they are integrated into the OS so you can access them quickly and in many ways. For example, you can select the Documents directory in Mac OS X Save and Open dialog boxes. This makes keeping your documents organized easier than if you create your own directories outside your Home folder.


You can add any folder to the Places sidebar, which is visible in all Open and Save dialog boxes along with Finder windows (when the sidebar is displayed). Adding a folder to the sidebar makes that folder accessible from many locations.

Another benefit of using the standard Mac OS X directories is that they take advantage of the default security settings that go with the user account. When you use directories outside a user account's Home folder, you should check and set the security of the folders you are using if you want to limit the access to those resources by other people who use your Mac.

To learn how to configure an item's security, see "Understanding and Setting Permissions," p. 843.

Most of the user directories are self-explanatory, such as Documents, Movies, and Music. A few of them are worthy of more detailed attention, though.

The Desktop Directory

The user's Desktop folder contains the items the user has placed on his desktop. Each user can have as much or as little on his desktop as he likes. When another user logs in, she sees only the contents of her desktop folder on the desktop.

The Library Directory

In the Library directory are system files specifically related to the user account. The Library directory includes a number of subdirectories (see Figure 4.11).

Figure 4.11. Each user has a Library directory in which files that relate to that user's system resources, such as preferences, are stored.


The particular folders you see depend on the applications you have used and what you have done. For instance, if you have installed iMovie, iPhoto, and iTunes, you'll find folders and files related to each of these applications. In the Fonts folder are fonts that only you can access. Your Internet plug-ins are stored in the Internet Plug-Ins folder, and the Preferences directory is where applications store your personal preferences.

The Public Directory

A user's Public directory is available to all users who log in to a particular Mac. This directory lets users conveniently share or transfer files because placing files or folders within the Public directory makes them available to all the other users on a particular machine.

To access the files and folders in another user's Public folder, perform the following steps:

  1. Open the Users directory.

  2. Open the Home directory for the user who has a file you want to share.

  3. Open the Public directory and use the files contained within it.


You can open a file or folder within another user's Public directory, or you can drag the file to your own directory to make a copy of it.

Within the Public directory, you also see a Drop Box folder. Other users can place items into this folder, but no one else can open the folder. This is useful when you want others to transfer items to you but don't want all the other users to be able to see what has been shared.

The Sites Directory

The Sites directory contains the files and folders that make up the Web site for each user account.

For more information on sharing a Web site under Mac OS X, see "Using Mac OS X to Serve Web Pages," p. 446.

    Part I: Mac OS X: Exploring the Core
    Part III: Mac OS X: Living the Digital Life