Android (operating system)
Programs for Android, also called "apps" (short for applications), usually come from the Google Play Store. The Android programs have a file extension of .APK. On May 7, 2019, Kotlin replaced Java as Google’s preferred language for Android app development. Java is still supported, as is C++. Google states that "Android apps can be written using Kotlin, Java, and C++ languages". Other languages may also be used; such as Python and Go, and those languages and even C++ may have restrictions.  Large portions of the operating system itself are also written in Java. Over 2.6 million apps are available for Android in the Google Play Store. Some apps are distributed elsewhere.