can you close all apps at once?

only by turning off your phone

No, you have to do it one by one, or turning off the phone.
Hope that helps!

Read the link I provided. Very few 3rd party apps run in the background.

It doesn't even work for me if I turn my phone off. I need to do the power + home buttons reset then it wipes out the apps from the bar.

That is a fast app switching bar which includes recently used apps. Only a few apps will run in the background. Because an app is in the fast app switching bar or recently used apps bar DOES NOT MEAN THE APP IS RUNNING IN THE BACKGROUND.

Read the link I provided with my first post in this thread.

I've often thought it would be nice to have a " close all apps " button. Apparently, most of them just stay in a suspended state using no processor power, but there are some that run in the background all the time. I suppose these are the ones that run the battery down faster than it should.

There is no need for one. Read the link I included with my first post in this thread.

The overwhelming majority of 3rd party apps will continue to be quit when pressing the home button to leave the app since there is no need for the overwhelming majority of 3rd party apps to run in the background or to be left in a suspended state.

Some apps such as games will be left in a suspended state when leaving the app so when returning to the app you can begin where you left off instead of launching the app and starting over. When such an app is in a suspended state, it isn't using any battery or processor cycles since it is suspended or frozen.

A handful of apps such as a music streaming app or a GPS turn by turn voice navigation app will continue to run in the background when leaving the app. Unless you are using such an app that has been updated for iOS4 in order to do so, no 3rd party apps are running in the background. The overwhelming majority of 3rd party apps will continue to be quit and a few such as games will be in a suspended state when leaving the app - not using ANY battery or processor cycles.

I agree with Allan McDonald. We need a close all button or an "app for that".

I know, Allan Sampson, that it is not needed for all apps but some apps don't refresh their info unless the app is closed and then reopened. I don't always want to see the info that was there when it was suspended and I might just want to shut down all those apps actually running in the background.

Too many Allans. 🙂

Name the 3rd party apps you are using that are suspended when leaving the app instead of being quit.

And name the 3rd apps you are using that are actually running in the background when leaving the app and how many of these are actually running in the background at the same time.

I'll bet you dollars to donuts there will be no quit all running apps selection since very few apps are suspended when leaving the app and even less can run in the background.

Wow! I keep seeing this topic again and again. That task bar sure bothers people. I can say this with confidence. I am a registered app developer. There are very few apps that take any resources when not the foreground app. The exceptions are app using location services and you will see the loc service icon next to the battery if one is active and Music apps. Then you will hear the music. Other apps are allowed several seconds to finish a task before they are placed in stasis. This is only for apps that have been made Multitasking aware. Older apps will just quit. Their icons will remain in the task bar but the app will not be in RAM and if you tap it's icon it will start up just as it would if you tapped it's icon on a home screen page.
Multitask Aware apps reside in a suspended state in RAM. They are not taking any resources what so ever. They can be cleared anytime the system needs the space. The user will never notice these actions.
Rest assured the bogged down state that the iphone 3g used to get into is gone. Just use the phone. Don't worry about the task bar. Have fun with this amazing device.

Thanks for backing up what I've provided several times in this thread. Hopefully this will finally sink in at some point.

I thought you linking to my multitasking article on When Will Apple would do the trick, but seems like some people are just so used to old style multitasking that if they see something in a "taskbar" then it must be running.

There actually are good reasons to have 'close all apps' function. I acknowledge your point that there are only a few apps using resources, and therefore, 'don't worry about it'. However, when I want to close one of 'few' multitaskers, it is not much fun scrolling 4 screens to find it. Also, with a little vision, one can see that there will be additional multi tasking apps in the future. Further 'close all apps' is not a difficult function to implement.