1947 [USA] † 2018

Terrance Colligan was the founder of Rational Systems (later renamed Tenberry Software), which, among other things, developed the DOS extender DOS/16M (for 16-bit systems) and DOS/4G (for 32-bit systems). This extension would be remembered for its DOS/4GW version included with Watcom compilers, which would eventually become an industry standard.

There was also a DOS/4GX for Quarterdeck's DESQview/X.

This allowed programs that took advantage of the new processors' real mode to run, even though DOS ran in protected mode for backward compatibility.

The DOS Protected Mode Interface (DPMI) was a specification introduced in 1989 that allowed a DOS program to run in a special protected mode, giving access to many of the features of those new processors.
Initially developed by Microsoft for Windows 3.0, it was later a free specification controlled by a free association committee.

DOS extenders were initially developed in the 1980s, after the introduction of the Intel 80286 processor, but were later replicated after the release of the Intel 80386, primarily to address the memory limitations of MS-DOS.

Of all the existing extenders (most notably DOS/32 Advanced and PMODE/W), DOS/4GW emerged in 1990, a 32-bit extender that allowed DOS programs to eliminate the conventional 640 KB memory limit, allowing them to address up to 64 KB of extended memory on Intel 80386 machines and higher.
DOS/4GW could operate within MS-DOS, PC-DOS, DR-DOS, and other DOS clones. It was developed as a subset of the earlier DOS/4G, an extender that shipped with the Watcom C/C++ and Fortran compilers.

Functioning as a highly flexible and reusable memory extension library, DOS/4GW allowed programmers to access extended memory without programming a single line of code specifically for it. The extender was embedded into the executable at link time and executed before the main application code, so DOS/4GW initialization messages usually appeared at startup, as seen in applications such as Adobe Acrobat Reader 1.0 and games such as Mortal Kombat (Midway Games, 1992), Doom (id Software, 1993), TFX (Digital Image Design, 1993), Rise of the Robots (Mirage, 1994), Descent (Parallax Software, 1995) or Duke Nukem 3D (3D Realms, 1996).