IPhone & IPad: Universal App, Which OS version do my users need?

I have a universal app for ipad and iphone. What I'm trying to determine is what OS version do my users need to have in order for my app to work?

In Xcode, in the top left hand corne开发者_开发百科r I see: "Device - 4.0 | Release | MyAppName"

Does this mean they need to have ios 4.0? Also, the weird thing is that my ipad is running ios version 3.2.2 but for some reason it works when I build&run the program on the device...

Can anyone help me out on how this all works? Thanks in advance

No, this doen't restrict the minimum OS. In the build settings, you should set the base SDK as high as possibile (otherwise the newest devices may not be able to run it), but set the iOS deployment target to as low as possibile (the lowest for an universal app is 3.0 - but check if all your classes that you are using are available in 3.0), because this tells the min. iOS it can run on.