Operating systems (OS) are the software which drive computing devices. They provide the software glue and are to software what a motherboard is to hardware. Computing devices have different requirements for their OS, as such there is a great variety of OS out there. PDA (personal digital assistants) have a streamlined OS which does not provide a lot of the functionality of say a PC OS. OS used on embedded devices tend to be very primitive and may lack security or even memory management. The more general purpose a device is, the more complicated and advanced the OS has to be.

Safety critical systems tend to have their own OS. Imagine if windows XP controlled air traffic control? The design concerns of a safety critical system will drive what features the OS will have. Real time response and stability would be two of the main areas of concern. Whilst PC OS'S tend to have ease of use and security as their major concerns.

The average user will not be aware of the operating system other than it's name! However understanding how the OS is nessesary in order to secure and optimise your computing experience.