In iOS7, when you double tap the home button, you not only see the list of apps that are currently running in the background, but also a preview window of each running app. What also changed is the way you shutdown any of the running app from the list.
Instead of holding down the app until it’s wiggling and clicking the cross-mark to kill it,
You simply swipe the preview window of the app you want to kill up to the top of the screen.
did you upgrade your iPhone 4 to iOS 7 ? I’m holding on after seeing the number from http://arstechnica.com/apple/2013/09/new-lease-on-life-or-death-sentence-ios-7-on-the-iphone-4/
Yes, I did. Its working great. Slow but still works. Its a great upgrade.