In computing, an operating system (OS) is the system software responsible for the direct control and management of the hardware that makes up a computer and basic system operations.
Colloquially, the term is most often used to mean all the software that "comes with" a computer system before any applications are installed.
The operating system takes care that other applications are able to use memory, in- and output devices and have access to the file system. If multiple applications are running, the operating system schedules these such that all processes have sufficient processor time.
Classifications and Terminology
An operating system is conceptually broken into two components. A shell and a kernel. As the name implies the shell is an outer wrapper to the kernel which in turn talks directly to the hardware.
Hardware <-> Kernel <-> Shell <-> Applications
In some operating systems the shell and the kernel are completely separate entities, allowing you to run varying combinations of shell and kernel (eg Unix), in others their separation is only conceptual (eg Windows).
Kernel design ideologies include monolithic kernel, microkernel and exokernel. Among commercial systems, such as Unix and Windows, the monolithic approach is predominant, with a few noted exceptions (eg, QNX). The microkernel approach is more popular among research OSes. Many embedded systems use ad-hoc exokernels.
See also: Programming, Software |
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