In general, the Operating System is the software on the first layer is placed on the computer’s memory when the computer starts. While other software is executed after running the Operating System and Operating System will perform the core public service for the software. Common core services such as access to the disk, memory management, task scheduling, and user interface. So that each software no longer have a common core tasks, because it can be served and carried out by the Operating System. Section of code that perform the core duties and the public called the “kernel” an Operating System.
The main operating systems that used a public computer (including PCs, personal computers) is divided into 3 major groups:
a) Microsoft Windows family – which is comprised of the Windows Desktop Environment (version 1.x to version 3.x), Windows 9x (Windows 95, 98, and Windows ME), and Windows NT (Windows NT 3.x, Windows NT 4.0 , Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7 (Seven) which was released in 2009, and of Windows 8, which was released in October 2012)).
b) Unix family of operating systems that use the POSIX interface, such as SCO UNIX, BSD family (Berkeley Software Distribution), GNU / Linux, MacOS / X (based on a modified BSD kernel, and is known by the name of Darwin) and GNU / Hurd.
c) Mac OS, an operating system for Apple’s computers are commonly called Mac or Macintosh. Latest operating system is Mac OS X version 10.6 (Snow Leopard). When the summer of 2011, launched version 10.7 (Lion).