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| DOS/4G | |
|---|---|
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| Developer | Tenberry Software |
| Initial release | July 1991; 34 years ago (1991-07)[1] |
| Final release | |
| Operating system | DOS |
| Platform | IA-32 |
| Type | DOS extender |
| License | Proprietary |
| Website | web |
DOS/4G is a32-bitDOS extender developed byRational Systems (laterTenberry Software).[3] It allowsDOS programs to eliminate the 640KBconventional memory limit by addressing up to 64MB[4] ofextended memory onIntel 80386 and above machines.
Functioning as a highly flexible and reusable memory extension library, DOS/4G allowed programmers to access extended memory without writing specialized code. It embeds itself in the executable file atlinking time and executes before main application code, so usually DOS/4G initialization messages show up at launch. It can in principle operate withinMS-DOS,PC DOS,DR-DOS and other DOS clones, the DOS boxes ofOS/2,Microsoft Windows,Windows NT andWindows 95, and DOS emulators such asDOSBox. However, in practice few DOS/4G games or other applications will run on non-DOS-based versions ofWindows, includingWindows NT,Windows 2000 andWindows XP, since none of these allow direct access to the hardware as was used for display rendering in those days.
Rational Systems first announced DOS/4G in July 1991. It was available immediately, at a price of US$5000 and up.[1][5]
DOS/4GW 1.95 was a free limited edition of DOS/4G and was included with theWatcom C compiler with a commercial re-distribution license. It was made widely popular by computer games likeDoom orTomb Raider.
Initial versions of DOS/4G had trouble with secondaryDMA channels on theISA bus, which prevented 16-bit devices likeGravis Ultrasound series from normally functioning; Gravis even had to develop PREPGAME, a patch utility which updated the game executable with a new version 1.97 to fix the incompatibility.
In case of problems, DOS/4G or DOS/4GW can be replaced with the newer and freeDOS/32; a patch utility can even replace DOS/4G code embedded inside a compiled executable file.[6]
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