Android is an operating system based on the Linux kernel,and designed primarily for touchscreen mobile devices such as smartphones and tablet computers.The user interface of Android is based on direct manipulation, using touch inputs that loosely correspond to real-world actions, like swiping, tapping, pinching and reverse pinching to manipulate on-screen objects. Android allows users to customize their home screens with shortcuts to applications and widgets, which allow users to display live content, such as emails and weather information, directly on the home screen. Windows Mobile is a family of mobile operating systems developed by Microsoft for smartphones and Pocket PCs. Windows Mobile is the predecessor of Windows Phone. Most versions of Windows Mobile have a set of standard features, such as multitasking and the ability to navigate a file system similar to that of Windows 9x and Windows NT, The iPhone is a line of smartphones designed and marketed by Apple Inc. It runs Apple’s iOS mobile operating system. The user interface is built around the device’s multi-touch screen, including a virtual keyboard. The iPhone has Wi-Fi and can connect to many different cellular networks, An iPhone can shoot video (though this was not a standard feature until the iPhone 3GS), take photos, play music, send and receive email, browse the web, send texts, GPS navigation, tell jokes, record notes, do mathematical calculations, and receive visual voicemail.video games, reference works, social networking, etc. — can be enabled by downloading application programs and also it support millions of applications.