Editing Copland (operating system) (section)

===Mac OS legacy===
Launched in 1984, the Macintosh and its operating system were designed from the start as a single-user, single-tasking system, which allowed the hardware development to be greatly simplified.<ref>{{Cite web|url=https://www.macworld.com/article/2025408/30-years-of-the-apple-lisa-and-the-apple-iie.html|title=30 years of the Apple Lisa and the Apple IIe|date=January 18, 2013|website=Macworld|access-date=August 28, 2020|archive-date=August 19, 2020|archive-url=https://web.archive.org/web/20200819175606/https://www.macworld.com/article/2025408/30-years-of-the-apple-lisa-and-the-apple-iie.html|url-status=live}}</ref>

{{Blockquote |text=The Macintosh lacks multitasking but tries to fake it, and it insists on a complicated user interface but leaves much of the work up to the application. These are serious drawbacks, and it is difficult to imagine elegant repairs for them.|author=Adam Brooks Webber |source=''[[Byte (magazine)|Byte]]'' (September 1986)<ref>{{cite magazine |last=Webber |first=Adam Brooks |title=Amiga vs. Macintosh |magazine=Byte |date=September 1986 |volume=11 |issue=9 |pages=249–256 |url=https://archive.org/details/byte-magazine-1986-09/page/n259/mode/2up}} (Adam Webber was the programmer responsible for porting [[TrueBASIC]] to the Amiga and Macintosh)</ref>}}

These limits meant that supporting the multitasking of more than one program at a time would be difficult, without rewriting all of this operating system and application code. Yet doing so would mean the system would run unacceptably slow on existing hardware. Instead, Apple adopted a system known as [[MultiFinder]] in 1987, which keeps the running application in control of the computer, as before, but allows an application to be rapidly switched to another, normally simply by clicking on its window. Programs that are not in the foreground are periodically given short bits of time to run, but as before, the entire process is controlled by the applications, not the operating system.

Because the operating system and applications all share one memory space, it is possible for a bug in any one of them to corrupt the entire operating system, and crash the machine. Under MultiFinder, any crash anywhere will crash all running programs. Running multiple applications potentially increases the chances of a crash, making the system potentially more fragile.

Adding greatly to the severity of the problem is the [[Patch (computing)|patching]] mechanism used to add functions to the operating system, known as [[System Preferences|CDEVs]] and [[Extension (Mac OS)|INITs]] or Control Panels and Extensions. Third party developers also make use of this mechanism to add features, including [[screensaver]]s and a hierarchical [[Apple menu]]. Some of these third-party control panels became almost universal, like the popular [[After Dark (software)|After Dark]] screensaver package.<ref name=Tidbits>{{cite web
 | last = Engst
 | first = Adam C.
 | title = After Dark Returns for Mac OS X
 | url = http://db.tidbits.com/article/7211
 | work = Tidbits
 | access-date = September 11, 2013
 | location = Ithaca, New York
 | date = June 9, 2003
 | archive-date = July 17, 2011
 | archive-url = https://web.archive.org/web/20110717055324/http://db.tidbits.com/article/7211
 | url-status = live
 }}</ref> Because there was no standard for use of these patches, it is not uncommon for several of these add-ons — including Apple's own additions to the OS — to use the same patches, and interfere with each other, leading to more crashing.