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| Developer(s) | Tenberry Software |
|---|---|
| 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).[2] It allowsDOS programs to eliminate the 640KBconventional memory limit by addressing up to 64[3]MB 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.
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.[4]
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