Wd96ball.zip 648 KB WDosX Version 0.96b Dos extender.This dos extender is used by Pascal Pro compiler.Source code is available.
Pro32v17.zip 76 KB Pro32 Version 1.7 Dos extender.This dos extender is used by DPas compiler and Pass32 assembler.Source code is available.
CAUSEWAY
The famous Causeway DOS extender for Watcom C/C++ has now been released into the public domain, sources and all. This means that it is not only free, you can do whatsoever you want with it (it's now public property). If you have a copy of the now defunct Watcom C/C++ around, or if you use assembly language and want to write in 32 bit protected mode, this is the extender to get. The extender has a small footprint, is very fast, and has a good selection of useful features. It comes with a linker and symbolic debugger, all of which include sources. The complete manual is also available from their web site (you have to save it page by page). This was my personal favourite among all available DOS extenders (back when I still wrote MSDOS software). Highly recommended.
Note: Watcom C/C++ will be eventually be released free under the Open Watcom Project.
WDOSX
This extender was originally developed for 32 bit programs generated by Borland C++ and Delphi. It has since been extended to support programs compiled and linked with Visual C++ and Watcom C/C++ as well as programs assembled using NASM. It provides most of the DPMI services, extends the most frequently used int 21h services as well as some of the int 33h (mouse) services. The extender is prepended to your executable and you need not ship any separate EXE files. A full-screen debugger is included. You can distribute applications bound with the extender royalty free (yes - even if they are commercial programs). The program is still being actively developed with new features being added to the development version. Believe it or not: source code is provided!
PRO32
This extender supports a number of assemblers and can handle DPMI, VCPI, and raw XMS. You can also use the DOS extender and protected mode debugger written by the same author (also free).
386POWER
If you write programs in assembly language, you may find this 32 bit DOS extender useful. It comes with source code which you can link with your assembly code to make a program that can run in 32 bit protected mode.
CSDPMI
This program is not really a DOS extender, but a DPMI host. It is useful if you need to distribute MSDOS programs that need DPMI services. It comes complete with source code. It is the DPMI server that comes with the free DJGGP C compiler . Sources for the DPMI host are also available here.
DOS32
A 32 bit DOS extender for use with assembly language files. It comes with a debugger and linker. This is an old 1995 version of the extender. If I'm not wrong, the new versions are commercial programs, and are no longer downloadable from the Internet. However, the documentation for this version suggests that you can distribute applications linked with the extender freely without payment of royalties.
EOS
This dos extender is designed to be used with an assembler or with Watcom C/C++. If used with the latter, it is a drop-in replacement for DOS4G/W. While the documentation for the (API) functions it supports is excellent, the documentation for its licensing terms is undecipherable. As a result, I'm not really sure whether the program can be used for freeware programs without a (shareware) payment being made, or whether a (paid) license has to be obtained before distributing applications linked with it.
PMODE
An early and well-known free DOS extender with source code. It is designed to be used with assembly language programs. This original version spawned versions (by others) for Watcom C/C++ (PMODE/W - see elsewhere on this page) and DJGPP .
RAW32
Not strictly a dos extender, this program is basically a protected mode environment for you to use with your assembly language programs (I think). It comes complete with source code and little else.
PMODE/W DOS EXTENDER
This is an adaptation of the PMODE DOS extender. It was modified so that it can function as a drop-in replacement for the DOS4GW extender that comes with Watcom C/C++. The extender provides a subset of DPMI services (not all) to the executable and extends some int 21h and int 33h (mouse) services (those extended by DOS4GW). It can run on systems with DPMI/VCPI/XMS services and systems that have none of the above. The extender may be used for freeware programs without payment of royalties.
NOTE: Both the official and unofficial sites seems to have disappeared, and no one seems to know what has happened. In the meantime, you can get the latest known version (1.33) of this DOS extender by clicking here (143,190 bytes) (this is a direct link to a zip file, so you might want to right click and use Save As or something).