Ultimate Portability

One of the amazing things about computers is that, whereas all other machines are amplifiers of our senses and muscles, computers are amplifiers of our minds. Of course, as useful as they are, all computers are only as good as the software running on them. Some computers are totally dedicated to one specific task, such as the computer that monitors the health of your automobile engine and alerts you to problems with it. Others are general-purpose computers, capable of a wide variety of tasks.

Because modern cellphone networks are digitally based, all modern cellphones have a built-in computer. Most of these computers are special-purpose computers because they are dedicated to operating only the phone features. A few others are more general purpose in nature and contain some other programs, most with simple PDA and game-playing functionality. But a select few are truly general-purpose computers residing in the highly portable form factor of a cell phone. One of these is, of course, the subject of this book.

Modern Android-based cellphones are among the most useful of portable computers, due in no small part to some of the amazing programs written to take advantage of the machine's capabilities—that is, the devices built into the machine that it accesses programmatically.

The original Android cellphone, the HTC/T-Mobile G1, is an intricate collection of devices that enable clever programmers to design advanced applications. A quick review of these devices provides a glimpse of what the machine is really capable of:

■ Multiple radios

G3 Cellular, for cellular and Internet service Bluetooth, for short-range local service with BT-enabled devices Wi-Fi, for access to Internet services via a local Wi-Fi hotspot GPS, for getting locational fixes from GPS satellites

■ Multiple sensory devices

Microphone, for audio input

Accelerometer, for sensing motion in space-time

Magnetic compass, for sensing direction relative to Earth

Multiple I/O devices

Touch screen, which provides the device with a tactile sense Color display, the main output device for visually oriented humans Keyboard, the main device for text input Loudspeaker, the main device for audio output Earphones, the secondary device for audio output Multiple computer resources

Dual-core processor—ARM 9 and ARM 11 32-bit CPUs Multimegabytes of RAM, for "working" storage while running Multigigabytes of SD FLASH, for secondary storage of data 528MHz clock, a fast clock for a cellphone-size device

Couple all that with a flexible and powerful base operating system that enables software programs to use those devices in an efficient and coordinated manner, and you end up with a surprisingly sophisticated little device.

Although not strictly considered an application, we would not be faithful to our book's title designation if we didn't give well-deserved kudos to Linus Torvalds and his mighty crew of developers. Always remember, Android is Linux—and Linux is awesome!

Lastly, in our discussion of the "devices" that make up the Android cellphone, let's not forget the most amazing peripheral device of all: the Internet itself.

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