DOS/4G is a 32-bit DOS extender developed by Rational Systems (now Tenberry Software). It allows DOS programs to eliminate the 640 KB conventional memory limit by addressing up to 64 MB of extended memory on Intel 80386 and above machines.
Functioning as a highly flexible and reusable memory extension library, DOS/4G allowed programmers to access extended memory without programming specialized code. It embeds itself in the executable file at linking time and executes before main application code, so usually DOS/4G initialization messages show up at launch. It can operate within MS-DOS, PC-DOS, DR-DOS and other DOS clones, the DOS boxes of OS/2, Microsoft Windows, Windows NT and Windows 95, and DOS emulators such as DOSBox.
DOS/4GW was a free limited edition of DOS/4G and was included with the Watcom C compiler with a commercial re-distribution license. It was made widely popular by computer games like Doom.
Initial versions of DOS/4G had trouble with secondary DMA channels on the ISA bus, which prevented 16-bit devices like Gravis Ultrasound series from normally functioning; Gravis even had to develop a 'patch' utility which updated the game executable to work around this incompatibility.
In case of problems, DOS/4G or DOS/4GW can be replaced with the newer and free DOS/32; a patch utility can even replace DOS/4G code embedded inside a compiled executable file.
Famous quotes containing the word dos:
“If I were sufficiently romantic I suppose I’d have killed myself long ago just to make people talk about me. I haven’t even got the conviction to make a successful drunkard.”
—John Dos Passos (1896–1970)