This document discusses mobile operating systems. It begins by defining a mobile operating system as the software that controls functions on mobile devices. It then provides an overview of some popular past and current mobile operating systems, including Symbian OS, iOS, Windows Phone, Blackberry OS, and Android. The market share of these systems is shown, with Android having the largest share at over 60%. The document also discusses future mobile operating systems under development, such as Firefox OS, Ubuntu Touch, and Tizen OS. It concludes by stating that a successful mobile operating system balances factors like user experience, battery life, and security across both software and hardware.