I know exactly what fragmentation is and don't need to 'gain a full understanding' as I already know what it is. There are lots of different devices with different screen sizes/resolutions, different features, sensors, etc., some have MicroSD slots, others don't, they run varying versions of Android, etc. This means there are apps that work for some phones and not others. This is fragmentation.
It's obvious that you do not have an understanding of it. It's obvious you are not interested in informing yourself, so I think we're done here. Have a nice day.
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im gona stick with my whatsapp, my contacts aren't even on google (i use outlook previously hotmail yeah sue me) and my other contacts are on facebook so
no thanks... i don't need to manage yet another list re-add friends, and have to manage a buddy list is a pain in the ass, yesterday i thought how bbm was going to fail nowadays with the horrible PIN-addy system, whatsapp or imessage just do things automatically with the phone number
You clearly don't understand how Hangouts works. You don't need to "re-add" anyone, and you don't need to manage a buddy list at all. You should at least become knowledgeable about an app before you decided to knock it.