An operating system (OS) is system software that manages computer hardware and software resources for its users and their applications. They include a kernel, which is the portion of the operating system code that is always resident in memory and facilitates interactions between hardware and software components.
There are three main purposes that an operating system fulfills:
-
Allocate resources among applications. The operating system gives each application a share of the resource, either in time (CPU) or space (memory), and isolates applications from each other to protect them from errors, but enable communications between different applications.
-
Provide an interface that abstracts the details of accessing hardware details (such as physical memory) to make things easier for programmers.
-
Provide common services, such as an interface for accessing network and disk devices, enabling an application to be run on different hardware without needing to be rewritten.