Introduction to Android

What is Android?

Android is an open-source mobile operating system built on a Linux kernel, developed by Google and the Open Handset Alliance. Apps are written mainly in Java/Kotlin and run in a secure sandbox on the Android runtime.

Anatomy of an Android App

An app is a set of components: Activities (screens), Services (background work), Broadcast Receivers (system events) and Content Providers (shared data). The manifest declares all of them along with required permissions.

Android Platform Stack

From bottom to top: the Linux kernel, native libraries, the Android runtime, the application framework and finally the apps.

Key Points

• Apps are sandboxed; each runs in its own process and user id.
• The manifest is the app's contract: components, permissions, and entry points.
• Activities are the visible screens users interact with.