Useful Mac OS X Terms: What is a Bundle?

In Mac OS 9, an application often resided in several folders, such as shared libraries in the Extensions folder, and the executable application in some arbitrary folder. In addition, an application itself was comprised of two "forks" within a single file: a data fork (which in the case of PowerPC code contained the program's executable code), and a resource fork. The resource fork contained templates for various elements of the user interface, such as the names of menus, menu items, dialogs, window types, the icon the Finder should display, and so forth.

In Mac OS X, this has changed. A bundle is a collection of these various data elements (executable code, resource information), each of which is a single file. These files are gathered together in a folder or "directory" and then presented to the user as a single, double-clickable file. In Mac OS X, applications are bundles.

Tip: Icons have an .icns suffix. You can edit them with Icon Composer or Pixie, two utilities that are available from the Apple Developer Connection (http://www.apple.com/developer/).

Tip: A bundle may be opened so you can see the individual components of the directory. Press Control then click its icon and choose Show Package Contents from the contextual menu.

Tip: Bundles are sometimes called "packages."

For further information, please visit Apple's Developer Connection at: http://www.apple.com/developer/ or you can view the specific Bundle information at:

http://developer.apple.com/techpubs/macosx/Essentials/SystemOverview/Bundles/