This document provides an overview of mobile operating systems. It discusses early pioneers like Martin Cooper and the Simon personal communicator. It then covers the evolution of modern mobile OSs like Symbian, iOS, Android, Windows Phone, and others. Key features of different OSs are outlined like the Java-based architecture of Android and Mach kernel underpinning iOS. The document concludes by noting that today's mobile OSs aim to provide full PC-like functionality through features like email, apps, games, browsing and more.