The software that drives the computer. Over the years many operating systems have been born (many more have died!). Commonly referred to as the “OS”, the operating system is the software that communicates with the hardware and provides the environment for software applications to run. There are many different types of operating systems with some being created for a specific purpose. Popular examples of operating systems are Windows, Mac OS, Linux, UNIX and others. Even cell phones and PDAs have operating systems. Windows CE, Symbian OS and Palm OS are popular among handhelds and PDAs.