Without an operating system your computer would not be worth anything. The operating system allows your computer to interact with users, keep up with changing needs, and allows computers to perform a variety of functions by organizing and controlling hardware and software in the computer so that it works in a predictable way.
All desktop or laptop computers have operating systems. Most personal computers or PCs come preloaded with Microsoft Windows, Macintosh PCs generally come preloaded with Mac OS X, and most corporate computers use Linux or UNIX operating systems. Smaller hand-held devices such as complex cellular phones, iPad, iPod, or other hand-held computer-based devices are now complex enough that they also have operating systems. This allows the user to do more with their computerized devices and allows the device to have more functional capabilities.
There is a very broad family of operating systems, but the basic four types of operating systems you will generally see are real-time operating systems (RTOS), single-user/ single task operating systems, single-user/ multitasking operating systems, and multi-user operating systems. The planned use of your computerized device will determine the appropriate operating system for you.
Real-time operating systems are used to control machinery, industrial systems, and/or scientific instruments. Single-user/ single task operating systems are used to control the system so that one user can do one thing at a time. With a single-user/ multitasking operating system the user is able to have several programs running at the same time. This type of operating system is what is most typically used in personal computers. A multi-user operating system allows several users to access the computer’s resources at the same time.