Editing Amiga (section)

== Operating systems ==

=== AmigaOS ===
[[File:AmigaOne X1000 02.jpg|thumb|AmigaOne X1000 running AmigaOS 4.1]]
{{Main|AmigaOS}}

AmigaOS is a single-user multitasking [[operating system]]. It was one of the first commercially available consumer operating systems for personal computers to implement [[Preemption (computing)|preemptive]] multitasking. It was developed first by Commodore International and initially introduced in 1985 with the Amiga 1000. [[John C. Dvorak]] wrote in ''PC Magazine'' in 1996: {{blockquote|[AmigaOS] remains one of the great operating systems of the past 20 years, incorporating a small kernel and tremendous [[Computer multitasking|multitasking]] capabilities the likes of which have only recently been developed in [[OS/2]] and [[Windows NT]]. The biggest difference is that the AmigaOS could operate fully and multitask in as little as {{nowrap|250 K}} of address space.<ref name="AutoP5-32" />}}

AmigaOS combines a [[command-line interface]] and [[graphical user interface]]. [[AmigaDOS]] is the disk operating system and command line portion of the OS and [[Workbench (AmigaOS)|Workbench]] the native graphical windowing, graphical environment for file management and launching applications. AmigaDOS allows long [[filename]]s (up to 107 characters) with [[Whitespace character|whitespace]] and does not require [[filename extension]]s. The [[windowing system]] and user interface engine that handles all input events is called [[Intuition (Amiga)|Intuition]].<ref name="amiga_intuition_ref" />

The multi-tasking kernel is called [[Exec (Amiga)|Exec]]. It acts as a scheduler for tasks running on the system, providing pre-emptive multitasking with prioritised round-robin scheduling. It enabled true pre-emptive multitasking in as little as 256&nbsp;KB of free memory.<ref name="amiga_rkm_libs_exec" /><ref name="holloway_oo_amiga_exec" />

AmigaOS does not implement [[memory protection]]; the [[68000]] CPU does not include a [[memory management unit]].<ref name="google.groups.com (Memory Protection)" /> Although this speeds and eases [[inter-process communication]] because programs can communicate by simply passing a [[pointer (computer programming)|pointer]] back and forth, the lack of memory protection made the AmigaOS more vulnerable to [[Crash (computing)|crashes]] from badly behaving [[Computer program|programs]] than other multitasking systems that did implement memory protection,<ref>{{cite book|url=https://books.google.com/books?id=Lr8ldHhh_wsC&pg=PA74 |title=Tech Book 1 - Published articles Oct 2006 - June 2008 - Michael Reed - Google Boeken |publisher=Michael Reed |isbn=9780956081315 |access-date=2013-07-24}}</ref> and Amiga OS is fundamentally incapable of enforcing any form of security model since any program had full access to the system. A co-operational memory protection feature was implemented in AmigaOS 4 and could be retrofitted to old AmigaOS systems using Enforcer or CyberGuard tools.

The problem was somewhat exacerbated by Commodore's initial decision to release documentation relating not only to the OS's underlying software routines,{{Citation needed|reason=says who?|date=September 2020}} but also to the hardware itself, enabling intrepid programmers who had developed their skills on the [[Commodore 64]] to [[PEEK and POKE|POKE]] the hardware directly, as was done on the older platform. While the decision to release the documentation was a popular one and allowed the creation of fast, sophisticated sound and graphics routines in games and demos, it also contributed to system instability{{Citation needed|reason=When and where|date=September 2020}}as some programmers lacked the expertise to program at this level. For this reason, when the new [[Advanced Graphics Architecture|AGA]] chipset was released, [[Commodore International|Commodore]] declined to release low-level documentation in an attempt to force developers into using the approved software routines.{{Citation needed|reason=this should be easy to document in press releases, etc.|date=September 2020}}

The latest version for the PPC Amigas is the [[AmigaOS 4 | AmigaOS 4.1]] and for the 68k Amigas is the AmigaOS 3.2.2

==== Influence on other operating systems ====
AmigaOS directly or indirectly inspired the development of various operating systems. [[MorphOS]] and [[AROS]] clearly inherit heavily from the structure of AmigaOS as explained directly in articles regarding these two operating systems. AmigaOS also influenced [[BeOS]], which featured a centralized system of [[Amiga support and maintenance software#Datatypes|Datatypes]], similar to that present in AmigaOS. Likewise, [[DragonFly BSD]] was also inspired by AmigaOS as stated by Dragonfly developer Matthew Dillon who is a former Amiga developer.<ref name="AutoP5-33" /><ref name="AutoP5-34" /> [[WindowLab]] and [[amiwm]] are among several [[window manager]]s for the [[X Window System]] seek to mimic the Workbench interface. IBM licensed the Amiga GUI from Commodore in exchange for the REXX language license. This allowed [[OS/2]] to have the WPS ([[Workplace Shell]]) GUI shell for OS/2 2.0, a 32-bit operating system.<ref>{{Cite web|url=http://www.os2bbs.com/os2news/OS2Warp.html|archive-url=https://web.archive.org/web/20121020022353/http://www.os2bbs.com/os2news/OS2Warp.html|url-status=dead|title=OS/2 News, OS/2 BBS|archive-date=October 20, 2012}}</ref><ref>{{cite web |author=Doug McIlroy |url=http://www.catb.org/esr/writings/taoup/html/ch03s02.html#os_2 |title=OS/2 Eric S. Raymond Operating System Comparisons The Art of Unix Programming |publisher=Catb.org |access-date=2013-07-24 |archive-url=https://web.archive.org/web/20130520104032/http://www.catb.org/esr/writings/taoup/html/ch03s02.html#os_2 |archive-date=2013-05-20 |url-status=live }}</ref>

=== Unix and Unix-like systems ===
Commodore-Amiga produced [[Amiga Unix]], informally known as Amix, based on AT&T [[UNIX System V|SVR4]]. It supports the [[Amiga 2500]] and Amiga 3000 and is included with the [[Amiga 3000UX]]. Among other unusual features of Amix is a hardware-accelerated windowing system that can scroll windows without copying data. Amix is not supported on the later Amiga systems based on [[68040]] or [[68060]] processors.

Other, still maintained, operating systems are available for the classic Amiga platform, including Linux and [[NetBSD]]. Both require a CPU with [[Memory management unit|MMU]] such as the [[68020]] with [[68851]] or full versions of the [[68030]], [[68040]] or [[68060]]. There is also a version of Linux for Amigas with PowerPC accelerator cards. [[Debian]] and [[Yellow Dog Linux]] can run on the AmigaOne.

There is an official, older version of [[OpenBSD]]. The last Amiga release is 3.2. [[MINIX]] 1.5.10 also runs on Amiga.<ref name="AutoP5-35" />

=== Emulating other systems ===
{{Main|Emulation on the Amiga}}

The [[Amiga Sidecar]] is a complete [[IBM PC XT]] compatible computer contained in an expansion card. It was released by Commodore in 1986 and promoted as a way to run business software on the Amiga 1000.