Androids Underlying Architecture

The Android platform is designed to be more fault-tolerant than many of its predecessors. The handset runs a Linux operating system upon which Android applications are executed in a secure fashion. Each Android application runs in its own virtual machine (see Figure 1.8). Android applications are managed code; therefore, they are much less likely to cause the phone to crash, leading to fewer instances of device corruption (also called "bricking" the phone, or rendering it useless).

The Linux Operating System

The Linux 2.6 kernel handles core system services and acts as a hardware abstraction layer (HAL) between the physical hardware of the handset and the Android software stack. Some of the core functions the kernel handles include

■ Enforcement of application permissions and security

■ Low-level memory management

■ Process management and threading

■ The network stack

■ Display, keypad input, camera,Wi-Fi, Flash memory, audio, and binder (IPC) driver access

The Android Platform

f \

Android

Application

A

Written Using

Android

Java Framework

DALVIK Virtual Machine

t >

Android

Application

B

Written Using

Android

Java Framework

DALVIK Virtual Machine

/ -

Android

Application

C

Written Using

Android

Java Framework

DALVIK Virtual Machine

Linux 2.6 Operating System

(Hardware Abstraction Layer)

Other Drivers WiFi, Bluetooth, Camera, Audio, Telephony, Flash, Device Sensors

Physical Hardware

Figure 1.8 Diagram of the Android platform architecture.

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