Is Registration id same for all devices in Push notification

I am new to android.I want to do small app using push notifications.I gone through the documents on push notifications.Actually to get notifications from 3rd party server we need to register for C2DM server (google provides this) .Then that server sends one registration id.My doub开发者_JAVA百科t is " That registration id is same for all devices which installs our application and requests for registration or each device will get different registration id to get notifications ".

please let me clear the doubt.As my research that reg id is different.

Thank You.

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I think, for the same iPhone and iOS its same. But if you upgrade the iOS it can be changed.