In Snow Leopard, little dots of light appeared in the Dock beneath apps that were open. But Lion’s default state is to eliminate these open-app indicators, in yet another way that Lion makes your Mac work like an iPad. Here’s how to get the dots back, so you always know what’s open.

It’s entirely possible that you might not care which apps are open on your Mac. Casual users probably have no need to know. But power users like to monitor their memory usage, for various reasons. High-powered apps tend to hog all the horsepower, for example, and quitting out of an app frees up that memory for other uses.

If you want to know when your apps are open, here’s what to do.

Open “Systen Preferences.” Click on the “Dock” icon. Check the box at the very bottom, where it says “Show indicator lights for open applications.”

There you go. From now on, you’ll know exactly when your apps are open or closed, just by glancing down at your Dock.