The document provides an overview of Symbian OS, including: - Symbian OS is an open, mobile operating system designed for battery-powered devices. It provides robustness, stability and low power consumption. - The OS layers include the user interface, core system services, and hardware interface layers. It supports various UI designs like Series 60 and UIQ. - The platform has evolved over time with new versions adding features like multimedia enhancements, graphics acceleration, security improvements and support for additional devices and networks.