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.
| Formerly | Rational Systems |
|---|---|
Company type | Private |
| Industry | Software, DOS extenders |
| Headquarters | Phoenix, Arizona, United States |
Key people | Terence Colligan (president) |
| Products | DOS/16M, DOS/4G, DOS/4GW |
History and products
editRational 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.[1][2]
The company renamed itself Tenberry Software in the mid-1990s. President Terence Colligan was involved with the company through this period.[3][4]
See also
editReferences
edit- ↑ "HelpDesk". InfoWorld. 29 August 1994. p. 41.
- ↑ Microcomputers (1995). Windows/DOS Developer's Journal. R&D Publications.
- ↑ "DEP Terry Colligan". 17 September 2018.
- ↑ "IBM, Microsoft Move to Retrieve Desperate OS/2 Situation". Tech Monitor. 9 October 1989. Retrieved 3 January 2026.
External links
edit- Tenberry Software (archived)
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