Editing History of operating systems (section)

===Personal computer era===
[[File:Apple Lisa (Little Apple Museum) (8032162544).jpg|thumb|Apple Lisa running Lisa OS]]
The development of microprocessors made inexpensive computing available for the [[small business]] and hobbyist, which in turn led to the widespread use of interchangeable hardware components using a common interconnection (such as the [[S-100 bus|S-100]], SS-50, [[Apple II]], [[Industry Standard Architecture|ISA]], and [[Conventional PCI|PCI]] [[bus (computing)|bus]]es), and an increasing need for "standard" operating systems to control them. The most important of the early OSes on these machines was [[Digital Research]]'s [[CP/M]]-80 for the 8080 / 8085 / Z-80 CPUs. It was based on several Digital Equipment Corporation operating systems, mostly for the PDP-11 architecture. Microsoft's first operating system, [[Marc McDonald|MDOS/MIDAS]], was designed along many of the PDP-11 features, but for microprocessor based systems. [[MS-DOS]], or [[IBM PC DOS|PC DOS]] when supplied by IBM, was designed to be similar to CP/M-80.<ref>{{cite web|url=https://www.embedded.com/was-dos-copied-from-cp-m/|title=Was DOS copied from CP/M?|author=Bob Zeidman|date=August 6, 2016}}</ref> Each of these machines had a small boot program in ROM which loaded the OS itself from disk. The BIOS on the IBM-PC class machines was an extension of this idea and has accreted more features and functions in the 20 years since the first IBM-PC was introduced in 1981.

The decreasing cost of display equipment and processors made it practical to provide graphical user interfaces for many operating systems, such as the generic [[X Window System]] that is provided with many Unix systems, or other graphical systems such as [[Apple Computer|Apple]]'s [[classic Mac OS]] and [[macOS]], the [[RadioShack|Radio Shack]] Color Computer's [[OS-9|OS-9 Level II/Multi-Vue]], [[Commodore International|Commodore]]'s [[AmigaOS]], [[Atari TOS]], [[IBM]]'s [[OS/2]], and [[Microsoft Windows]]. The original GUI was developed on the [[Xerox Alto]] computer system at Xerox [[PARC (company)|Palo Alto Research Center]] in the early 1970s and commercialized by many vendors throughout the 1980s and 1990s.

Since the late 1990s, there have been three operating systems in widespread use on personal computers: [[Apple Inc.]]'s [[macOS]], the [[Open-source software|open source]] [[Linux]], and [[Microsoft Windows]]. Since 2005 and the [[Mac transition to Intel processors]], all have been developed mainly on the [[x86]] platform, although macOS retained [[PowerPC]] support until 2009 and Linux remains ported to a multitude of architectures including ones such as [[68k]], [[PA-RISC]], and [[DEC Alpha]], which have been long superseded and out of production, and [[SPARC]] and [[MIPS architecture|MIPS]], which are used in servers or embedded systems but no longer for desktop computers. Other operating systems such as AmigaOS and OS/2 remain in use, if at all, mainly by [[retrocomputing]] enthusiasts or for specialized embedded applications.