Operating system (OS) software is a set of programs that manage computer hardware resources and facilitate the use of application programs. Examples of modern operating systems are Linux, Mac OS X, Microsoft Windows, iOS, and Android.
The central component of an operating system is the kernel; this is the core software in an operating system that performs the functions listed below. Modern operating systems also have device drivers, as well as a selection of tools or utility programs that are used to manage and monitor the computer.
The activities carried out by the kernel typically include:
Process management. A running computer operating system typically has several programs running at once. The kernel controls the initiation, execution, and termination of these programs, as well as the allocation of hardware components (such as CPUs, memory, and peripherals) between the running programs.
Memory management. The kernel allocates memory to itself as well as to processes that are running. The kernel responds to processes that request more (or less) memory. Programs are permitted to use only the memory allocated to them; the kernel enforces this restriction.