An operating system, sometimes called an OS, is the foundation of all system software on your computer. It is the part of your computer that is responsible for controlling input and output devices, managing files, and prioritizing system requests, as well as controlling and allocating memory. If your computer didn't have a working operating system, it would essentially be a large paperweight.
If you have problems with your computer and need to call a tech support hotline, you'll probably be asked which operating system you are running. The easiest way to determine which operating system your computer is running is to watch what appears when you start your computer. In most cases, your computer will display the logo of which operating system it is running for a brief time before all of the software loads.
Microsoft Windows dominates the market for personal computers, although there are several different versions of the Windows operating system available. If your computer is running Microsoft Windows, you can go to START > RUN and type "winver.exe" in the open field to be taken to a dialog box describing which version of Windows is on your computer.
If your computer is running Mac OS X, you can determine which operating system version you have by selecting "About this Mac" from the Apple menu. A small window will appear that displays your version number.
Linux is the name usually given to any Unix-like operating system that works by using the Linux kernel. Linux operating systems are mostly used by servers, but they may also be found in video game systems, mobile phones, e-book readers, and DVRs. The Linux operating system is unique in that all underlying source code can be freely used, modified, and redistributed by anyone.
While troubleshooting technical problems is one example of a situation when it's helpful to know your computer operating system, knowing which operating system you have is also useful when you're purchasing new software for your computer. Some games and desktop publishing or personal accounting programs are only compatible with certain operating systems. For example, your purchase may not work if you're running a version of Windows that is considered to be out of date. However, for general Web surfing and sending email to friends and family, any operating system that allows your computer to work effectively is sufficient. An upgrade is only required when you begin to have problems that interfere with your productivity.