IPhone 4 models. In fall 2010, pentalobe screws started to replace the Philips screws used in post-repair units in the US and in production units in Japan. The iPhone 4 shipped with iOS 4, which was the newest version of Apple's iOS mobile operating system at the time. iOS 4 introduced a multitasking system, allowing apps to remain "suspended" in memory, perform certain operations in the background, and allowing users to switch between apps using an on-screen menu. It also introduced FaceTime, which allows users to perform video calls between other iPhone, iPad, iPod Touch, and OS X users. The iPhone 4
IPhone 3GS There are two ways to activate Voice Control: hold the Home button while in the home screen for a few seconds; or, change the effect of what double-clicking the home button does so it will activate Voice Control (only on iOS 3.x; on iOS 4 or later, double clicking the Home button opens the multitasking bar). VoiceOver, Color Inversion, and Text Zoom were introduced as exclusive features to the iPhone 3GS. VoiceOver is a feature that dictates music details, system menus, text, and other things which was first introduced on the third generation iPod shuffle. Color inversion reverses the color