{{Short description|Interface between an external application and a BBS}}
In a bulletin board system (BBS), a '''door''' is an interface between the BBS software and an external application.<ref>{{cite journal|title=A Glossary of BBS Terms|journal=InfoWorld|date=15 Aug 1988|url=https://books.google.com/books?id=ZzoEAAAAMBAJ&q=BBS+door&pg=PA41|page=41}}</ref> The term is also used to refer to the external application, a computer program that runs outside of the main bulletin board program. Sometimes called ''external programs'', doors are the most common way to add games, utilities, and other extensions to BBSes.<ref name="wolf explosion">{{cite book|last=Wolf|first=Mark J P|title=The Video Game Explosion: A History from PONG to PlayStation and Beyond|year=2008|publisher=ABC-CLIO|url=https://books.google.com/books?id=XiM0ntMybNwC&q=BBS+door&pg=PA155|page=155|isbn=9780313338687}}</ref> Because BBSes typically depended on the telephone system, BBSes and door programs tended to be local in nature, unlike Internet games and applications.<ref name="wolf explosion"/>
From the 1990s on, most BBS software had the capability to "drop to" doors. Several standards were developed for passing connection and user information to doors; this was usually done with "dropfiles", small binary or text files dropped into known locations in the BBS's file system. Most doors were responsible for operating the serial port or other communications device directly until returning control to the BBS. Later development of FOSSIL drivers have allowed both BBSes and their doors to communicate without being responsible for direct operation of the communications hardware.
== Door games ==
A major use of doors is for ''door games'': computer games played on the BBS.<ref>{{cite web|title=BBS Door games|url=http://www.mobygames.com/game-group/bbs-door-games|work=Moby Games|accessdate=18 October 2012}}</ref> These games included strategy games such as ''TradeWars 2002'', ''Food Fight!'',<ref name="PC Magazine">{{cite web |last=Edwards |first=Benj |date=October 1, 2010 |title=The Internet's Forgotten Games: BBS Door Games |url=https://www.pcmag.com/slideshow_viewer/0%2C3253%2Cl%3D255130%26a%3D255131%26po%3D10%2C00.asp |url-status=dead |archive-url=https://web.archive.org/web/20160604214853/http://www.pcmag.com/slideshow_viewer/0%2C3253%2Cl%3D255130%26a%3D255131%26po%3D10%2C00.asp |archive-date=June 4, 2016 |accessdate=May 28, 2016 |work=PC Magazine |postscript=Slide 10 of 12. }}</ref> ''Solar Realms Elite'',<ref name="wolf encyclopedia">{{cite book|last=Wolf|first=Mark J P|title=Encyclopedia of Video Games: The Culture, Technology, and Art of Gaming|year=2012|publisher=ABC-CLIO|page=568}}</ref> ''Space Dynasty'', Usurper,<ref>{{cite book|last1=Wolf|first1=Mark|title=Encyclopedia of Video Games: A-L|date=2012|publisher=ABC-CLIO|isbn=978-0-313-37936-9|page=80}}</ref> and ''Barren Realms Elite''.<ref>{{cite book|last=Morrow|first=Blaine Victor|title=Dial Up!: Gale's Bulletin Board Locator|year=1996|publisher=Gale}}</ref> There were also role-playing games (RPG), often derived from earlier email-based games—examples include Seth Robinson's ''Legend of the Red Dragon'',<ref>{{cite book|last=Tresca|first=Michael J|title=The Evolution of Fantasy Role-Playing Games|year=2010|publisher=McFarland|pages=93–94}}</ref> popular dystopian RPG: ''Operation: Overkill,''<ref name="PC Magazine"/> and ''Mutants!''. BBSes often published high scores, encouraging players to beat others.<ref name="shefski199305">{{cite magazine | url=http://www.cgwmuseum.org/galleries/index.php?year=1993&pub=2&id=106 | title=A survey of gems to be found on private bulletin board systems | magazine=Computer Gaming World | date=May 1993 | accessdate=7 July 2014 | author=Shefski, William J. | pages=64}}</ref>
InterBBS leagues allowed users of different BBSes to compete against each other in the same game. A modern version of this known as BBSlink exists allowing sysops to offer door games on their BBS which are hosted on a remote server, thereby increasing the user base of the game.
== Other applications ==
While many of the most popular and memorable BBS doors have been games, numerous doors had non-entertainment applications such as user polls or the time bank, permitting users to time-shift their rationed BBS use. Frequently they act as a front-end to themed databases on subject such as astrology, numerology and fortune-telling, recipes, weather prediction, personal ads (sometimes with additional match-making functionality), classified ads and "for sale" listings (sometimes permitting auctions), BBS lists, and parting comments from the most recent BBS callers.
== References ==
{{reflist}}
== External links ==
* [https://breakintochat.com/ Break Into Chat] - BBS door game wiki * [http://archives.thebbs.org/ BBS Archives] - Collection of BBS doors and related files * [https://web.archive.org/web/20140814175202/http://goldfndr.home.mindspring.com/dropfile/ Dropfile Formats]
{{BBS}} {{video game gameplay}}
Category:Bulletin board systems Category:Bulletin board system software Category:Door games