Devices Running Android

There are more than 40 Android phones in the market from more than ten manufacturers. Other hardware also runs Android, such as tablets and televisions. Software can access information on the target device using the android.os.Build class, for example:

if(android.os.Build.MODEL.equals("Nexus+One")) { ... }

Android-supported hardware shares some common features due to the nature of the operating system. The Android OS is organized into the following images:

■ Bootloader—Initiates loading of the boot image during startup

■ Boot image—Kernel and RAMdisk

■ System image—Android operating system platform and apps

■ Data image—User data saved across power cycles

■ Recovery image—Files used for rebuilding or updating the system

■ Radio image—Files of the radio stack

These images are stored on nonvolatile flash memory, so they are protected when the device powers down. The flash memory is used like read-only memory (hence, some call it ROM), but can it be rewritten as necessary (for example, with over-the-air Android operating system updates).

On startup, the microprocessor executes the bootloader to load the kernel and RAMdisk to RAM for quick access. The microprocessor then executes instructions and pages portions of the system and data images into RAM as needed.The radio image resides on the baseband processor, which connects to the radio hardware.

A comparison of some of the early and more recent smart phone models is shown in Table 1.1. It shows that the processing hardware architecture is similar across devices: a microprocessor unit (MPU), synchronous dynamic random access memory (SDRAM or RAM for short), and flash memory (called ROM for short). The screen size is given in pixels, but the dots per inch (dpi) vary depending on the physical screen size. For example, the HTC Magic has a 3.2-inch diagonal screen with 320x480 pixels.This equates to 180 pixels per inch, but is classified as a medium pixel density device by Android (which averages as 160 dpi). All smartphones also offer a CMOS image sensor camera, Bluetooth (BT), and Wi-Fi (802.11), although there are variations.

Table 1.1 Comparison of Some Representative Android Smartphones. Data from http://en.wikipedia.org/wiki/List_of_Android_devices and http://pdadb.net/.

Model

HTC Dream / G1 (October 2008)

528-MHz

QCOM

MSM7201A

RAM/ ROM

Screen

192MB/ TFT LCD 256MB 320x480 mdpi

Other Features

GSM/UMTS slide out keyboard, trackball, AGPS BT2.0, 802.11b/g, 3.1-MP camera

Table 1.1 Continued

Model

RAM/ ROM

Screen

Other Features

Samsung Moment (November 2009)

Motorola Milestone / Droid (November 2009)

Nexus One / HTC Passion (January 2010)

HTC Droid Incredible (April 2010)

HTC EVO 4G (June 2010)

800-MHz

ARM1176

JZF-S

550-MHz TI

0MAP3430

288MB/ 512MB

1-GHz QCOM Snapdragon

1-GHz QCOM Snapdragon

1-GHz QCOM Snapdragon

256MB/ 512MB

512MB/ 512MB

512MB/ 512MB

512MB/ 1GB

AMOLED CDMA/1xEV-DO 320x480 slide out keyboard mdpi (backlit), DPAD

TFT LCD GSM/UMTS or 480x854 CDMA/1xEV-DO hdpi slide out keyboard,

DPAD

BT2.1, 802.11b/g, 5-MP camera AGPS

AMOLED GSM/UMTS 480x800 Trackball, dual hdpi microphones

BT2.0,802.11a/b/g/n, 5-MP camera AGPS, geotagging

AMOLED CDMA/1xEV-DO 480x800 BT2.1, 802.11a/b/g/n, hdpi 8-MP camera

AGPS, geotagging

TFT LCD CDMA/1xEV-480x800 DO/802.16e-2005 hdpi BT2.1,802.11b/g,

8-MP camera 1.3MP front-facing camera, AGPS

Table 1.1 Continued

Model

RAM/ ROM

Screen

Other Features

Motorola Droid X (July 2010)

Sony-Ericsson Xperia X10a (June 2010)

Samsung Galaxy S Pro (August 2010)

Acer Stream / Liquid (September 2010)

1-GHz TI

OMAP363Q

1-GHz QCOM Snapdragon

1-GHz

Samsung

Hummingbird

1-GHz QCOM Snapdragon

512MB/ 8GB

256MB/ 1GB

512MB/ 2GB

512MB/ 512MB

TFT LCD CDMA/1xEV-DO, FM 480x854 radio hdpi BT2.1,802.11b/g/n,

8-MP camera AGPS, geotagging

TFT LCD GSM/UMTS, FM radio 480x854 BT2.1, 802.11b/g, hdpi 8-MP camera

AGPS, geotagging

AMOLED CDMA/1xEV-DO, 480x800 802.16, FM radio hdpi slide out keyboard

BT3.0, 802.11b/g/n, 5-MP camera 0.3MP front-facing camera, AGPS

AMOLED GSM/UMTS, FM radio 480x800 BT2.1, 802.11b/g/n, hdpi 5-MP camera

AGPS, geotagging

Other than improved capacity and performance on newer models, another main differentiator is additional features. Some devices offer 4G, some have FM radio, some have slide-out keyboards, and some have a front-facing camera. Knowing the differentiators helps a developer create great applications. In addition to the built-in hardware, every Android device comes with a secure digital (SD) card slot. An SD card provides additional storage space for multimedia and extra application data. However, until Android 2.2, the apps themselves could be stored only on the internal ROM.

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