An operating system, also known as an OS or O/S, is computer software that manages a computer and communicates with the system hardware. Kernels and programs called drivers are used by the operating system to manage installed hardware like the mouse, keyboard, network adaptor and video card. The operating system also manages system resources, including memory, processors and file management. Operating systems have evolved over time from command line based systems to systems with a Graphical User Interface or GUI. The GUI is used to manage the computer with a keyboard and mouse. Older operating systems like DOS and early AIX and, both developed by IBM, did not include a GUI. The system was managed by command lines and programs. Microsoft Windows has the most market share among modern operating systems. The Windows operating system runs on IBM platform, Intel based systems. Current versions of Windows are Windows Vista and Windows XP. Older versions like Windows 2000, Windows 98, Windows 95 and the original Windows, Windows 3.x, are no longer supported by Microsoft. Windows 2000 and above are multi-user and multi-processing operating systems. The operating system allows for multiple users to share the same computer, with separate logins, preferences and space for document storage. It also can handle multiple processors and multitask, or run several software programs at the same time. Mac OS X is another popular operating system that is shipped on Apple Macintosh computers. It succeeds the original Mac OS operating system. Previous versions of the Mac OS were compatible only with Motorola chip based Macintosh computers, but the current version can run on Intel-based systems. MAC OS X is based on the Unix operating system. Unix was developed in the 1970s and 80s, and uses a monolithic kernel for file system access, process control and networking. Device drivers are integrated with the kernel. Several other operating systems are based on a UNIX operating system. They are sometimes called Unix-like operating systems, and include BSD and Linux. UNIX systems run on a variety of systems and are usually used on servers and in schools and engineering applications. Among Unix based systems, Linux is the most popular. It’s available for free, and includes versions with GUIs like KDE, GNOME, Xfce and X Windows. Linux includes distributions like Ubuntu and HP-UX, which runs on HP computers and servers. Palm OS, Windows CE and Symbian OS.
