iOS, formerly known as the iPhone operating system, is a mobile operating system developed and distributed solely by Apple Inc. iOS is evolving into a universal operating system for all Apple mobile devices, such as iPad, iPod Touch, and iPhone. iOS is derived from macOS and hence is based on a Unix-like operating system. iOS manages the device hardware. The technologies required to implement native applications are also provided by iOS. It also ships with various system applications, such as Mail and Safari, which provide standard system services to the user. iOS-native applications are distributed through the App Store, which is closely monitored by Apple. More details about iOS are covered in Chapter 2, Understanding the Internals of iOS Devices.