{{Short description|Phoenix software company, developer of DOS/4GW and DOS/4G protected-mode extenders}} {{Infobox company | name = Tenberry Software | former_name = Rational Systems | type = Private | location = Phoenix, Arizona, United States | industry = Software, DOS extenders | products = DOS/16M, DOS/4G, DOS/4GW | key_people = Terence Colligan (president) }}
'''Tenberry Software''', formerly '''Rational Systems''', was a software company based in Phoenix, Arizona, best known for developing DOS/4G and DOS/4GW, DOS extenders that became a de facto standard for running 32-bit software under 16-bit MS-DOS in the early 1990s. The company also developed DOS/16M, an earlier extender that enabled 16-bit applications to access extended memory beyond the conventional 640 KB limit.
== History and products == Rational Systems developed DOS/16M and then DOS/4G, one of the first commercial DOS extenders enabling software to run in protected mode on Intel 80386 and later processors while booting from MS-DOS. DOS extenders were essential during the early 1990s because DOS itself could not directly address memory above 1 MB; a protected-mode extender allowed applications to bypass this constraint and access several megabytes of RAM, which was important for memory-intensive programs such as games, compilers and engineering tools.
Watcom licensed DOS/4G and bundled a royalty-free run-time version, DOS/4GW, with its Watcom C/C++ compiler. Developers who compiled software with Watcom C/C++ could distribute DOS/4GW freely with their products. This arrangement made DOS/4GW ubiquitous in the PC games market of the early-to-mid 1990s: titles including ''Doom'', ''Quake'', ''Duke Nukem 3D'' and numerous others shipped with DOS/4GW, making its startup message — "DOS/4GW Protected Mode Run-Time" — familiar to a generation of PC gamers.<ref>{{cite magazine|url=https://books.google.com/books?id=jjgEAAAAMBAJ&q=Tenberry%2BSoftware&pg=PA41|title=HelpDesk|magazine=InfoWorld|date=29 August 1994|page=41}}</ref><ref>{{cite book|last=Microcomputers|title=Windows/DOS Developer's Journal|url=https://books.google.com/books?id=QiFMAAAAYAAJ|year=1995|publisher=R&D Publications}}</ref>
The company renamed itself Tenberry Software in the mid-1990s. President Terence Colligan was involved with the company through this period.<ref>{{Cite web|url=http://www.javiergutierrezchamorro.com/dep-terry-colligan/3678|title=DEP Terry Colligan|date=17 September 2018}}</ref><ref>{{cite web|url=https://www.techmonitor.ai/hardware/ibm_microsoft_move_to_retrieve_desperate_os2_situation|title=IBM, Microsoft Move to Retrieve Desperate OS/2 Situation|date=9 October 1989|access-date=3 January 2026|publisher=Tech Monitor}}</ref>
== See also == * Phar Lap
== References == {{reflist}}
== External links == * [https://web.archive.org/web/20180615223025/http://www.tenberry.com/index.html Tenberry Software] (archived)
Category:Defunct software companies of the United States Category:Companies based in Phoenix, Arizona {{US-software-company-stub}}