The Time Dimension The design team developed the concept of a time-based operating system, using not only the two dimensions that you have on the screen, but also the third dimension of time. For example, everybody’s favorite complaint about the Macintosh human interface was that dragging a disk icon to the trash would eject it. That confused new users, because normally if you had a file that you wanted to delete, you would drag it to the trash and it would be gone; it seemed so wrong to make the same gesture eject a very valuable disk, full of information. In Mac OS X, depending on what you are doing at the time, different options are available to you. When you select an object that can be ejected, the trashcan changes to an eject icon, making sure that the action and what was showing on the screen are appropriate to the context. Similarly, when you select an empty CD or DVD disk, the trashcan changes to a “burn” icon. In previous versions of Mac OS, when you selected an application, all of that application’s windows came to the forefront. In Mac OS X, those windows appear in the order that you used them. If, for example, you are switching from Photoshop to an HTML editor, the Photoshop window is only one window behind; the system does not bring all of the other HTML editor windows to the front. This keeps the windows ordered in a way that people use them. As long as you can access the close button, even if it is behind several other windows, you can just click on it and it is gone. The principle of the time-based interface was built on some of the work that had been done in the Apple Advanced Technology Group (ATG) many years before: There was a project in ATG called Rosebud that explored how the dimension of time could be used to help people find things. This was based on an insight that people sometimes associate information with chronological events or sequences. For example, people may not remember where they saved a particular document on their computer but know that the last time they modified it was two days ago. Or
Mac OS 8—eject via trash Mac OS X—trash Mac OS X—eject Mac OS X—burn
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