This document provides an overview of system software, including operating systems and utility programs. It defines system software and describes the main functions of operating systems, such as starting up and shutting down computers, providing user interfaces, managing memory, and establishing internet connections. Several examples of stand-alone operating systems for desktop computers are given, including Windows, Mac OS X, Linux, and UNIX. Server operating systems and embedded operating systems are also briefly outlined. Finally, common utility programs are summarized, such as file managers, disk cleaners, backup utilities, and screen savers.