Editing Operating system (section)

==Popular operating systems==

{{Further|Usage share of operating systems|Comparison of operating systems}}
{{as of|2024|09|}}, [[Android (operating system)|Android]] (based on the Linux kernel) is the most popular operating system with a 46% market share, followed by [[Microsoft Windows]] at 26%, [[iOS]] and [[iPadOS]] at 18%, [[macOS]] at 5%, and [[Linux]] at 1%. Android, iOS, and iPadOS are [[mobile operating system]]s, while Windows, macOS, and Linux are desktop operating systems.<ref name="gs.statcounter.com"/>

===Linux===
{{Main|Linux}}
[[File:Layers of a Linux system.png|thumb|upright=1.7|[[Abstraction layer|Layer]]s of a Linux system]]
[[Linux]] is a [[free software]] distributed under the [[GNU General Public License]] (GPL), which means that all of its derivatives are legally required to release their [[source code]].{{sfn|Silberschatz et al.|2018|pp=779–780}} Linux was designed by programmers for their own use, thus emphasizing simplicity and consistency, with a small number of basic elements that can be combined in nearly unlimited ways, and avoiding redundancy.{{sfn|Tanenbaum|Bos|2023|pp=713–714}}

Its design is similar to other UNIX systems not using a [[microkernel]].{{sfn|Silberschatz et al.|2018|p=780}} It is written in [[C (programming language)|C]]<ref>{{cite news |last1=Vaughan-Nichols |first1=Steven |title=Linus Torvalds prepares to move the Linux kernel to modern C |url=https://www.zdnet.com/article/linus-torvalds-prepares-to-move-the-linux-kernel-to-modern-c/ |access-date=7 February 2024 |work=ZDNET |date=2022 |language=en}}</ref> and uses [[UNIX System V]] syntax, but also supports [[BSD]] syntax. Linux supports standard UNIX networking features, as well as the full suite of UNIX tools, while [[multiuser|supporting multiple users]] and employing [[preemptive multitasking]]. Initially of a minimalist design, Linux is a flexible system that can work in under 16 [[megabytes|MB]] of [[RAM]], but still is used on large [[multiprocessor]] systems.{{sfn|Silberschatz et al.|2018|p=780}} Similar to other UNIX systems, Linux [[Linux distribution|distribution]]s are composed of a [[Linux kernel|kernel]], [[system library|system libraries]], and [[system utilities]].{{sfn|Silberschatz et al.|2018|p=781}} Linux has a [[graphical user interface]] (GUI) with a desktop, folder and file icons, as well as the option to access the operating system via a [[command line]].{{sfn|Tanenbaum|Bos|2023|pp=715–716}}

[[Android (operating system)|Android]] is a partially open-source operating system closely based on Linux and has become the most widely used operating system by users, due to its popularity on [[smartphones]] and, to a lesser extent, [[embedded system]]s needing a GUI, such as "[[smart watch]]es, [[Android Automotive|automotive dashboard]]s, airplane seatbacks, [[medical devices]], and [[home appliance]]s".{{sfn|Tanenbaum|Bos|2023|pp=793–794}} Unlike Linux, much of Android is written in [[Java (programming language)|Java]] and uses [[object-oriented design]].{{sfn|Tanenbaum|Bos|2023|p=793}}

===Microsoft Windows===
{{Main|Microsoft Windows}}
[[File:Diagram of a security descriptor for a file on Windows.png|thumb|upright=1.3|Security descriptor for a file that is read-only by default, specified no access for Elvis, read/write access for Cathy, and full access for Ida, the owner of the file{{sfn|Tanenbaum|Bos|2023|pp=1021-1022}}]]
Windows is a [[proprietary]] operating system that is widely used on desktop computers, laptops, tablets, phones, [[workstation]]s, [[enterprise server]]s, and [[Xbox]] consoles.{{sfn|Tanenbaum|Bos|2023|p=871}} The operating system was designed for "security, reliability, compatibility, high performance, extensibility, portability, and international support"—later on, [[Energy efficiency in operating systems|energy efficiency]] and support for [[dynamic device]]s also became priorities.{{sfn|Silberschatz et al.|2018|p=826}}

[[Windows Executive]] works via [[Object Manager (Windows)|kernel-mode objects]] for important data structures like processes, threads, and sections (memory objects, for example files).{{sfn|Tanenbaum|Bos|2023|p=1035}} The operating system supports [[demand paging]] of [[virtual memory]], which speeds up I/O for many applications. I/O [[device drivers]] use the [[Windows Driver Model]].{{sfn|Tanenbaum|Bos|2023|p=1035}} The [[NTFS]] file system has a master table and each file is represented as a [[Record (computer science)|record]] with [[metadata]].{{sfn|Tanenbaum|Bos|2023|p=1036}} The scheduling includes [[preemptive multitasking]].{{sfn|Silberschatz et al.|2018|p=821}} Windows has many security features;{{sfn|Silberschatz et al.|2018|p=827}} especially important are the use of [[access-control list]]s and [[safety integrity level|integrity levels]]. Every process has an authentication token and each object is given a security descriptor. Later releases have added even more security features.{{sfn|Tanenbaum|Bos|2023|p=1036}}