Apple probably did not have as much trouble developing its OS X (read OS 10) operating system as it might in getting the millions of existing Mac users to accept it. The new system had to be designed to please fanatical, highly opinionated and committed fans. And these fans, generally being of a creative bent, have wildly different views as to how an operating system should behave. To resolve this dilemma, Apple created four distinct interfaces, allowing beta testers to move into OS X at their own speed and still take advantage of the new system's powerful and futuristic features. The Classic Interface is similar to the one Mac devotees are using in OS 9 and earlier versions. Most of the menus are in the same place and have similar contents - such as File, Edit and View. But some favourite parts are missing. For example, the Apple Menu that dropped down at the left of the Menu Bar is gone. This gave access to frequently used items and was a route to control panels and the Chooser. Also missing is the Application Switcher at the right-hand end of the Menu Bar, a feature used to switch between applications running in the background. Users also may miss the Control Strip - a tab that protruded from the side of the screen and gave instant control of frequently changed items such as sound volume. Many also will miss the pop-up windows, a way to clear the desktop while keeping important things handy. Though these features may be missed because of familiarity and habit, there is a better way to accomplish the same things on OS X. The better way is 'The Dock', described below. The point is that this Classic Interface is designed to appeal to the old guard, while getting them to sample the future. For the geeks, OS X re-introduces an old user interface that appeals to the techie bent. To programme, they simply use the Command Line Interface, available through an application called Terminal. Instead of using the mouse and graphic interface, Command Line lets a programmer or advanced user type in complex commands that will directly control the operating system. The pro user who manages large amounts of files on a day-to-day basis probably will prefer the 'Browser' environment, also called the 'List View'. This displays folder-document hierarchy in multiple lists from left (drives or folders) to right (files, documents and thumbnail images of final creations). As much as this is still a Mac operating system, and thus extremely customisable, it is the Aqua Interface that fully represents OS X. It is fluid, multi-dimensional and accessible. It moves and glows and flows with a sensuousness and energy that suggests it is alive, or certainly more alive than an operating system has ever been. Beta testers report that after a few awkward moments of breaking old habits, it is intuitive and inviting. Apple has posted movies showing some of these features at www.apple.com/macosx/theater/ . The most prominent feature of the Aqua Interface is The Dock, a row of icons along the bottom of the Aqua screen. These colourful and photorealistic icons sit poised to respond to any number of stimuli. Pass the mouse over The Dock and it swells like a wave to enlarge the icons for easy viewing. Click on an icon and it gracefully explodes to full size, exposing a document. Remember, this is a completely new operating system, not an upgrade, and as such Apple has done a remarkable job. I found it refreshing and quickly became comfortable using the Aqua Interface. E-mail Dave Horrigan at firstname.lastname@example.org with your Mac queries.