Phil Schiller took the stage today at WWDC 2011 to talk Lion with the audience of developers from all over the world. He announced that Mac OS X Lion will have a Resume feature that allows users to quit an app on their Mac, and return to it much later, seamlessly resuming where they left off. The feature should work in much the same way as multitasking does on iOS devices, where you can leave a game of Scrabble or Words With Friends, and come back to it days later only to find everything exactly as you left it. The obvious benefit of this feature — and this is huge — is that you no longer need to keep your apps open to save their states. This means that you can quit an app in Lion to save resources, without fear of losing what you were working on previously.

The Resume feature works hand-in-hand with Lion’s other great save feature, Autosave. Autosave automatically creates saved versions of a file for you as you work, so you never need to manually save a file again, as long as you’re working in a Lion-compatible application. This makes the Mac work more like stateless apps such as Notational Velocity and Evernote, and less like the traditional file-save model that has been in use for the last 25+ years of computing history. This will be fantastic for novice Mac users, who often forget to save what they are working on, and will allow the rest of us to focus more on our work, and less on our computers — a trend that Apple seems to be wholeheartedly embracing.

These two features will combine with Lion’s new Versions feature. Versions will use Autosave to create automatic versions of a file as you work. These versions will be saved inside the file itself — not as separate files. It accomplishes this by only documenting the changes you make to the file, rather than creating a whole new copy of the file. This allows you to have many, many versions of a document inside of just one file. This will be a dream come true for writers and coders alike, as they will be able to simply revert back to a previous version in a split second when a mistake is detected. For example, if a website breaks when you use a current version of its code, you can just revert back to a version when it was working perfectly. Another use case is that of a college student writing a paper. Let’s say you accidentally delete an entire page of your paper, but don’t notice until much later. You could revert back to a version containing the missing text, copy the text, and revert back to the current version, pasting the missing text back in. It’s like time travel, but without all the massive storage requirements and time-consuming backups of Time Machine.

These three features combine to make Lion a truly next-gen operating system, a tool that actively works, even on the lowest levels, to make your life easier. It achieves this by leaving behind the old traditions and forming new ones designed for computing work in today’s high-speed world. We won’t need to worry about saving — or losing — a file ever again.