The iPhone has a minimal hardware user interface, featuring five buttons. The only physical menu button is situated directly below the display, and is called the “Home button” because it closes the active app, accesses TOUCH ID, and navigates to the home screen of the interface.The device maintains a similar design to iPhone 5, with a 4 in (10 cm) LCD Touchscreen, with a screen resolution of 640×1136 at 326 . However its home button has been updated with a new flat design using a laser-cut sapphire cover surrounded by a metallic ring; the button is no longer concave, nor does it contain the familiar squircle icon seen on previous models.The phone itself is 0.30 in (7.6 mm) thin and weighs 112 grams (4.0 oz).The phone uses an aluminum composite frame.The device is available in three color finishes; “space-grey” (replacing black with
slate trim), white with silver trim, and white with gold trim.
The home button on iPhone 5S incorporates a fingerprint recognition system known as Touch ID, based on technology from AuthenTec, a company which Apple had acquired in 2012. The sensor uses a capaciter CMOS-based sensor which can detect the “sub-epidermal layers” of fingers at 500 pixels per inch, and uses a 360-degree design that can read the print at any angle. The sensor itself is activated by a touch-sensitive metallic ring surrounding the button. Touch ID can be used for various authentication activities within the operating system, such as unlocking the device or authenticating App store and itunes purchases instead of an Apple ID password. The sensor can be trained to recognize the fingerprints of multiple fingers and multiple users. Fingerprint data is stored in an encrypted format within a “secure enclave” of the A7 chip itself, and is not accessible to any other apps or servers!