My work iMac just got upgraded to OS X “Lion” (10.7), and I’ve configured everything how I’ve wanted it and pretty much gotten accustomed to all of the new software features and quirks.

One of the new features in Lion is that the OS is designed so that you never have to think about saving, because every new (read: the one’s that implement the feature) Application saves their state intelligently upon exiting/quitting. This feature sounds great, and it is most of the time… but having used computers for years and logically thinking of quitting an app as being able to start it again with a clean slate, made for quite the confusing experience sometimes.

Now, for the average consumer, I can see how this can save someone’s ass, but for some of the applications I was using it was really more annoying than anything else.

Luckily, there’s a quick Terminal command you can run that will disable this window saving behavior in an app:

defaults write com.namespace.appname NSQuitAlwaysKeepsWindows -bool false

Obviously, insert the namespace and app name of the offending app into that command to switch off the window saving behavior.

So, for example to turn off the annoying feature of the new Terminal app that makes it so upon launch the terminal window shows grayed out text from the previous session, you would enter this in your Terminal/CLI:

defaults write com.apple.Terminal NSQuitAlwaysKeepsWindows -bool false

And to stop having the Preview app stack window upon window of itself every time it opens a new window over its previous one (even though its been closed completely), you enter this:

defaults write com.apple.Preview NSQuitAlwaysKeepsWindows -bool false

And there you go. The app should no longer save its state (at least its open windows anyway) and resume it upon launch.