Editing Computer multitasking (section)

== Preemptive multitasking ==
{{Main|Preemption (computing)#Preemptive multitasking}}
[[File:Kubuntu_21.04_(KDE_Plasma_5)_-_Virtual_Desktops.png|thumb|Kubuntu (KDE Plasma 5) four [[Virtual desktop]]s running multiple programs at the same time]]
Preemptive multitasking allows the computer system to more reliably guarantee to each process a regular "slice" of operating time. It also allows the system to deal rapidly with important external events like incoming data, which might require the immediate attention of one or another process.  Operating systems were developed to take advantage of these hardware capabilities and run multiple processes preemptively. Preemptive multitasking was implemented in [[TOPS-10|the PDP-6 Monitor]] and [[Multics]] in 1964, in [[OS/360 and successors#MFT|OS/360 MFT]] in 1967, and in [[Unix]] in 1969, and was available in [[PDP-8#Programming facilities|some operating systems]] for computers as small as DEC's PDP-8; it is a core feature of all [[Unix-like]] operating systems, such as [[Linux]], [[Solaris (operating system)|Solaris]] and [[Berkeley Software Distribution|BSD]] with its [[Comparison of BSD operating systems|derivatives]],<ref>{{cite web
 | url = http://www.ibiblio.org/team/intro/unix/what.html
 | title = UNIX, Part One | work = The Digital Research Initiative
 | date = 2002-01-30 | access-date = 2014-01-09
 | publisher = ibiblio.org
}}</ref> as well as modern versions of Windows.

Possibly the earliest preemptive multitasking OS available to home users was [[Microware]]'s [[OS-9]], available for computers based on the [[Motorola 6809]] such as the [[TRS-80 Color Computer 2]],<ref name="rainbow198309_dynamicuno">{{ cite magazine | url=https://archive.org/details/198309Rainbow/page/236/mode/2up | title=Dynamic Uno | magazine=The Rainbow | last1=Downard | first1=Dan | date=September 1983 | access-date=9 May 2024 | pages=236–240 }}</ref> with the operating system supplied by Tandy as an upgrade for disk-equipped systems.<ref name="tandyrsc11">{{ cite book | url=https://archive.org/details/RSC-11_Computer_Catalog_1984_Radio_Shack_a/page/n52/mode/1up | title=1984 TRS-80 Catalog | publisher=Tandy Corporation | date=1984 | access-date=14 May 2024 | pages=53–54 }}</ref> [[Sinclair QDOS]] on the [[Sinclair QL]] followed in 1984, but it was not a big success. Commodore's [[Amiga]] was released the following year, offering a combination of multitasking and multimedia capabilities. Microsoft made preemptive multitasking a core feature of their flagship operating system in the early 1990s when developing [[Windows NT 3.1]] and then [[Windows 95]]. In 1988 Apple offered [[A/UX]] as a [[UNIX System V]]-based alternative to the [[Classic Mac OS]]. In 2001 Apple switched to the [[NeXTSTEP]]-influenced [[Mac OS X]].

A similar model is used in [[Windows 9x]] and the [[Windows NT|Windows NT family]], where native 32-bit applications are multitasked preemptively.<ref>{{cite magazine|url=http://www.smartcomputing.com:80/editorial/article.asp?article=articles%2F2005%2Fs1606%2F08s06%2F08s06.asp|magazine=[[Smart Computing]]|title=Windows 2000 &16-Bit Applications|volume=16|issue=6|pages=32–33|date=June 2006|author=Joseph Moran|archive-url=https://web.archive.org/web/20090125104811/http://www.smartcomputing.com/editorial/article.asp?article=articles%2F2005%2Fs1606%2F08s06%2F08s06.asp|archive-date=January 25, 2009|url-status=dead}}</ref> 64-bit editions of Windows, both for the [[x86-64]] and [[Itanium]] architectures, no longer support legacy 16-bit applications, and thus provide preemptive multitasking for all supported applications.