Friday, July 6, 2007

How iphone Works


In January 2007, Steve Jobs introduced the Apple iPhone during his keynote address at the Macworld Conference and Expo. In its first appearance onscreen and in Jobs's hand, the phone looked like a sleek but inanimate black rectangle.

Then, Jobs touched the screen. Suddenly, the featureless rectangle became an interactive surface. Jobs placed a fingertip on an on-screen arrow and slid it from left to right. When his finger moved, the arrow moved with it, unlocking the phone. To some people, this interaction between a human finger and an on-screen image -- and its effect on the iPhone's behavior -- was more amazing than all of its other features combined.

And those features are plentiful. In some ways, the iPhone is more like a palmtop computer than a cellular phone. As with many smartphones, you can use it to make and receive calls, watch movies, listen to music, browse the Web, and send and receive e-mail and text messages. You can also take pictures with a built-in camera, import photos from your computer and organize them all using the iPhone's software. Although it's not a turn-by-turn GPS receiver, the iPhone also lets you view map and satellite data from Google Maps, including overlays of nearby businesses.
A modified version of the Macintosh OS X operating system, also used on Apple desktop and laptop computers, lets you interact with all of these applications. It displays icons for each application on the iPhone's screen. It also manages battery power and system security. The operating system synchs the phone with your computer, a process that requires a dock much like the one used to synch an iPod. It also lets you multitask and move through multiple open applications, just like you can on a laptop or desktop computer.

But instead of using a mouse or a physical keyboard, the iPhone uses virtual buttons and controls that appear on its screen. This isn't really a new phenomenon -- touch screens have been part of everything from self-checkout kiosks to smartphones for years. But the iPhone's touch-screen is a little different from many of the others currently on the market. When you touch the screen on a PDA or a Nintendo DS, you typically use a slender, pointed stylus. The iPhone, on the other hand, requires you to use your fingers. It can also detect multiple touch points simultaneously, which many existing touch-screens cannot do.

The iPhone Touch-screen
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Shot at 2007-07-06
Electronic devices can use lots of different methods to detect a person's input on a touch-screen. Most of them use sensors and circuitry to monitor changes in a particular state. Many, including the iPhone, monitor changes in electrical current. Others monitor changes in the reflection of waves. These can be sound waves or beams of near-infrared light. A few systems use transducers to measure changes in vibration caused when your finger hits the screen's surface or cameras to monitor changes in light and shadow.
The basic idea is pretty simple -- when you place your finger or a stylus on the screen, it changes the state that the device is monitoring. In screens that rely on sound or light waves, your finger physically blocks or reflects some of the waves. Capacitive touch-screens use a layer of capacitive material to hold an electrical charge; touching the screen changes the amount of charge at a specific point of contact. In resistive screens, the pressure from your finger causes conductive and resistive layers of circuitry to touch each other, changing the circuits' resistance.


iPhone Features and Applications
The front surface of the Apple iPhone has only one button -- the Home button. Pressing the Home button takes you to the main screen of the iPhone's graphical user interface. There, you can choose from the device's four primary functions using icons at the bottom of the phone:
Phone: GSM or EDGE cellular phone service as well as a visual voice mail menu
Mail: POP and IMAP e-mail access, including in-line pictures, HTML capabilities and push e-mail from Yahoo mail
Web: Safari Web browser
iPod: Music and videos

You can open the iPhone's other applications from the upper portion of the Home screen. These include a calendar, calculator, notepad, and widgets, or mini-applications made specifically for the iPhone. You can also use an iPhone to check weather reports and stock quotes. Even though the iPhone doesn't support Flash, which the YouTube site relies on, you can watch YouTube videos using the corresponding application. The keys and buttons you need to navigate each application appear only when you need them.
The shape of the screen changes when you need it to as well -- you can shift the perspective from vertical to horizontal by tilting the phone. An accelerometer inside the iPhone lets the operating system know to change the orientation of the image on the screen. This means that you can scroll through long lists of music files on a long, narrow screen, and you can watch movies in a widescreen format.
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