DJ Delorie has produced DJGPP, a protected mode programming environment
 which supports a port of the GNU C/C++/Ada. For more informat see
 <Q:10.04> [What and where is DJGPP?]

 Users of Borland C++ Version 4.xx could once purchase the Borland
 PowerPack for DOS Version 1.00; however, it appears that its sell has
 been discontinued. This package includes Borland C++ 4.02 Service
 Update, 16-bit DPMI libraries and extenders, 32-bit DPMI libraries and
 extenders, TurboVision 2.0 (16-bit DOS, 16-bit DPMI, 32-bit DPMI),
 SuperVGA BGI Drivers (16-bit DOS, 16-bit DPMI, 32- bit DPMI).

 A reader of comp.os.msdos.programmer has the following updateu about the
 PowerPack and additional information about DPMI programming:

 [begin quote]
   About protected-mode programming (Question 7.10), Borland no longer
   supports the PowerPack (from what I've read in this newsgroup), so
   I doubt that it can still be purchased. However, the FAQ could 
   mention that the extender is integrated into Borland C++ version 5.x
   (and probably the Builder product as well).
   
   Borland doesn't fully support that either, since the documentation
   isn't very clear about compiling DPMI programs and a stub for the
   executable has to be extracted from one of Borland's executables. The
   necessary steps were posted a long time ago (by someone else), and I
   can provide the information if necessary. Even if the FAQ didn't
   describe those steps, it could at least indicate that version 5.x can
   compile DPMI programs (as well as clarifying the PowerPack info).
 [end quote]

 There are more extenders out there. One notable DOS extender is Adam
 Seychell's DOS32 Version 3.5 beta. It can be found at
 <http://www.programmersheaven.com/zone5/cat19/1363.htm> Also check out
 Adam's page at <http://www.geocities.com/SiliconValley/2151/pmode.html>