A, Android system architecture:
1. Linux kernel layer
Android based on the Linux kernel, provide the underlying hardware drivers for a variety of Android devices
such as: a display driver, audio, camera, Bluetooth, Wi-Fi driver, power management, etc.
2. System runtime layer
is provided by C / C ++ library for the Android system is the main feature support,
such as SQLite library provides support for the database tier,
OpenGL | ES 3D graphics library provides support for
Webkit library provides support for the browser kernel
, etc.
this layer also Android runtime library,
mainly to provide some of the core library that allows developers to write Android applications using JAVA
runtime library also includes the Dalvik virtual machine (after 5.0 operating environment changed ART), which enables Android applications to run in a separate process , and has its own instance of the Dalvik virtual machine
with respect to the Java virtual machine, dalvik virtual machine into mobile devices custom, optimized for limited phone memory and CPU performance situation
3. the application framework layer
mainly provides when building applications may be used in a variety of API,
Android comes with some of the core applications is the use of this API completed,
developers can also build your own program by using these API
4. application layer
all applications installed on the phone belong to this layer
, such as the system comes with contacts, text messages and other program
or download others program of
Or develop their own programs
Second, the various versions of Android, code-named
| version number | System Code | API | Chinese meaning | release time |
| 1.0 | Astro Boy & Bender | API 1 | Astro Boy & Clockwork Robot | 2008.9 |
| 1.1 | Petit Four | API 2 | Fancy Cakes | 2009.2 |
| 1.5 | Cupcake | API 3 | Cup cake | 2009.4 |
| 1.6 | Donut | API 4 | Donuts | 2009.9 |
| 2.0 | lightning | API 5 | Puffs | 2009.10 |
| 2.0.1 | API 6 | 2009.12 | ||
| 2.1 | API 7 | 2010.1 | ||
| 2.2 | Froyo | API 8 | Frozen yogurt | 2010.5 |
| 2.3.0-2.3.2 | Gingerbread | API 9 | gingerbread | 2010.12 |
| 2.3.3-2.3.7 | API 10 | 2011.2 | ||
| 3.0 | Honeycomb | API 11 | honeycomb | 2011.2 |
| 3.1 | API 12 | 2011.5 | ||
| 3.2.0-3.2.6 | API 13 | 2011.7 | ||
| 4.0.0-4.0.2 | Ice Cream Sandwich | API 14 | Ice cream sandwich | 2011.10 |
| 4.0.3-4.0.4 | API 15 | 2011.12 | ||
| 4.1 | Jelly Bean | API 16 | jelly Bean | 2012.7 |
| 4.2 | API 17 | 2012.11 | ||
| 4.3 | API 18 | 2013.7 | ||
| 4.4 | KitKat | API 19 | Kit Kat | 2013.11 |
| 4.4w-4.4w.2 | API 20 | 2014.6 | ||
| 5.0 | Lollipop（Android L） | API 21 | Lollipop | 2014.10 |
| 5.1 | API 22 | 2015.3 | ||
| 6.0 | Marshmallow（Android M） | API 23 | cotton candy | 2015.10 |
| 7.0 | Nougat（Android N） | API 24 | Nougat | 2016.5 |
| 7.1 | API 25 | 2016.10 | ||
| 8.0 | Oreo (Android O) | API 26 | Oreo | 2017.3 |
| 8.1 | API 27 | 2017.12 | ||
| 9.0 | Pistachio Ice Cream（Android P） | API 28 | Pistachio Ice Cream | 2018.8 |
| 10.0 | (Unknown) (Android Q) | API 29 | 2019.5 |