Technically speaking, Android is open-source. This means anyone can look at the operating system's code, or change it - this is how OEMs like HTC and Samsung add their own tweaks. That openness has often been a rallying cry for hardcore Android enthusiasts. Why use a closed platform like iOS, when you can have a free and open-source platform?

But even from the beginning, there were components of Android that were closed-source. The Gmail app, Maps, Google Talk, and the Play Store were some of the earliest examples. To combat the always-present fragmentation of Android, Google offers many APIs through the Play Services Framework.

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