Interface

The display responds to three sensors: a proximity sensor that shuts off the display and touchscreen when the iPhone is brought near the face to save battery power and to prevent spurious inputs from the user's face and ears, an ambient light sensor that adjusts the display brightness which in turn saves battery power, and a 3-axis accelerometer, which senses the orientation of the phone and changes the screen accordingly. Photo browsing, web browsing, and music playing support both upright and left or right widescreen orientations, while videos play in only one widescreen orientation.
A single "home" hardware button below the display brings up the main menu. Subselections are made via the touchscreen. The iPhone utilizes a full-paged display, with context-specific submenus at the top and/or bottom of each page, sometimes depending on screen orientation. Detail pages display the equivalent of a "Back" button to go up one menu.
The iPhone has three physical switches on its sides: wake/sleep, volume up/down, and ringer on/off. All other multimedia and phone operations are done via the touch screen.
The iPhone interface enables the user to move the content itself up or down by a touch-drag motion of the finger, much as one would freely slide or flick a playing card across a table with a finger. Similarly, scrolling through a long list in a menu works as if the list is pasted on the outer surface of a wheel: the wheel can be "spun" by sliding a finger over the display from bottom to top (or vice versa). In either case, the object continues to move based on the flicking motion of the finger, slowly decelerating as if affected by friction. In this way, the interface simulates the physics of 3D objects, giving it a real world feel.
The photo album and web page magnifications are examples of multi-touch sensing. It is possible to zoom in and out of web pages and photos by placing two fingers (e.g. thumb and forefinger) on the screen and spreading them farther apart or closer together, as if stretching or squeezing the image. As can be expected from multi-touch sensing, the two fingers don't have to be from the same hand.

Text input
For text input, the device implements a virtual keyboard on the touchscreen. It has automatic spell checking and correction, predictive word capabilities, and a dynamic dictionary that learns new words. The predictive word capabilities have been integrated with the dynamic virtual keyboard so that users will not have to be extremely accurate when typing—i.e. touching the edges of the desired letter or nearby letters on the keyboard will be predictively corrected when possible. The keys are somewhat larger and spaced further apart when in landscape mode, currently only available using the Safari. Not focusing more on texting has been considered a chief weakness of the iPhone, while at the same time the virtual keyboard is a bold step and a worthwhile risk.
David Pogue of The New York Times and Walt Mossberg of The Wall Street Journal both tested the iPhone for two weeks and found learning to use it initially difficult, although eventually usable. Pogue stated use was "frustrating" at first, but "once you stop stressing about each individual letter and just plow ahead, speed and accuracy pick up considerably." After five days of use, Mossberg "was able to type on it as quickly and accurately as he could on the Palm Treo he has used for years," and considered the keyboard a "nonissue." Both found that the typo-correcting feature of the iPhone was the key to using the virtual keyboard successfully.