View source for Open system (computing)

{{Refimprove|date=June 2008}}
{{distinguish|Open-source software}}
'''Open systems''' are [[computer system]]s that provide some combination of [[interoperability]], [[software portability|portability]], and [[open standard|open software standard]]s. (It can also refer to specific installations that are configured to allow unrestricted access by people and/or other computers; this article does not discuss that meaning).

The term was popularized in the early 1980s, mainly to describe systems based on [[Unix]], especially in contrast to the more entrenched [[mainframe computer|mainframes]] and [[minicomputer]]s in use at that time. Unlike older [[legacy system]]s, the newer generation of Unix systems featured standardized programming interfaces and peripheral interconnects; third party development of hardware and software was encouraged, a significant departure from the norm of the time, which saw companies such as [[Amdahl Corporation|Amdahl]] and [[Hitachi Data Systems History|Hitachi]] going to court for the right to sell systems and peripherals that were compatible with IBM's mainframes.

The definition of "open system" can be said to have become more formalized in the 1990s with the emergence of independently administered software standards such as [[The Open Group]]'s [[Single UNIX Specification]].

Although computer users today are used to a high degree of both hardware and software interoperability, in the 20th century the open systems concept could be promoted by Unix vendors as a significant differentiator. IBM and other companies resisted the trend for decades, exemplified by a now-famous warning in 1991 by an IBM account executive that one should be "careful about getting locked into open systems".<ref>{{cite newsgroup 
  | title = Open Systems Strategy from IBM
  | author = Ian Dickinson
  | date = 1991-07-11
  | newsgroup = comp.unix.misc
  | url = http://groups.google.com/group/comp.unix.misc/msg/8d6c9967273f11db
  | access-date =  2006-08-13
}}</ref>

However, in the first part of the 21st century many of these same legacy system vendors, particularly IBM and [[Hewlett-Packard]], began to adopt [[Linux]] as part of their overall sales strategy, with "[[Open-source software|open source]]" marketed as trumping "open system".  Consequently, an IBM mainframe with [[Linux on IBM Z]] is marketed as being more of an open system than [[commodity computer]]s using closed-source [[Microsoft Windows]]—or even those using Unix, despite its open systems heritage. In response, more companies are opening the source code to their products, with a notable example being [[Sun Microsystems]] and their creation of the [[OpenOffice.org]] and [[OpenSolaris]] projects, based on their formerly closed-source [[StarOffice]] and [[Solaris (operating system)|Solaris]] software products.

==See also==
* [[Open API]]
* [[Open format]]
* [[Open mainframe]]
* [[Open System Environment Reference Model]]
* [[Unix wars]]

==References==
{{Reflist}}

[[Category:Computer systems]]
[[Category:History of computing]]
[[Category:Open standards| ]]
[[Category:Unix history]]