An operating system is difficult to define, but has been called "the layer of software that manages a computer's resources for its users and their 詳細

Early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, … 詳細

The components of an operating system all exist in order to make the different parts of a computer work together. All user software needs to go through the operating system in … 詳細

If an application is written for use on a specific operating system, and is ported to another OS, the functionality required by that application may be implemented differently by that OS … 詳細

Multicomputer operating systems
With multiprocessors multiple CPUs share memory. A multicomputer or cluster computer has multiple CPUs, each of which has its own memory 詳細

Unix and Unix-like operating systems
Unix was originally written in assembly language. Ken Thompson wrote B, mainly based on BCPL, based on his experience in the MULTICS 詳細

A hobby operating system may be classified as one whose code has not been directly derived from an existing operating system, and has few users and active developers.
In some cases, hobby development is in support of a " 詳細