Free Development Tools


  • The Open Watcom site offers a free C++ compiler, which includes WLink, Wasm and WD, a DPMI debugger which is compatible with HX.
  • MinGW, CygWin, DJGPP and EMX are all based on GCC, the GNU C/C++ compiler frontend. MinGW and CygWin are for Win32, DJGPP is for 32bit DOS, EMX is for OS/2 + 32bit DOS. The GCC C compiler is good and produces compact code, the C++ version tends to bloat the binaries a bit. HX supports MinGW, CygWin and DJGPP. EMX has not been tested.
  • The Digital Mars C++ compiler is free and the package includes OPTLINK, a very good OMF linker.
  • On the LADSoft site you may get the free and very good OMF linker VALX.EXE. Also somewhere on this site one may find the CC386 C compiler, which is shipped with several DOS extenders, but HX is compatible with it as well. Last but not least the site hosts GRDB, a debugger for DOS and DPMI applications. Written by David Lindauer.
  • Pelles C is a good and free C compiler. An IDE is included, as well as a full toolset (POLINK, POLIB, PORC) to build Win32 binaries.
  • The MS Visual C++ Toolkit 2003 - which included the MS optimizing Visual C++ compiler - is regretably no longer downloadable. Microsoft now recommends to download the Visual C++ 2008 Express Edition, which is "bloatware" IMO.
  • Borland also has a free C++ compiler to offer in the C++ Turbo Explorer package, but will force you to answer some questions first. Support for DOS extended applications is NOT included there, but luckily HX can fully replace this missing feature (;-)). Regretably the licence coming with this package doesn't allow commercial software development, so you cannot sell any binary created by the compiler.


  • Free Pascal is pretty much Delpi compatible and is free (GPL).
  • Virtual Pascal is 'officially dead'. But it is a very good, free compiler with a nice and fast IDE (Turbo Vision style).


  • Masm v6.15 is included here. The license requires that you own MS VC 6. Alternatively, Masm v8 can be used, but IIRC the license is pretty restricted.
  • NASM (Netwide Assembler) is a free assembler (BSD license) which runs on Linux, Win32 and DOS. Supports 16-, 32- and 64-bit, and lots of output formats. It runs a bit slow and the macro capabilities are pretty limited compared to MASM's.
  • FASM (Flat Assembler) is a free assembler which runs on Win32, DOS and Linux. Supports 16-, 32- and 64-bit assembly. OMF output format isn't supported. IMO FASM's assembly syntax and macro capabilities are the best among the "Nasm-style" assemblers.
  • YASM is a rewrite of NASM. BSD license.
  • POASM in included in PellesC. It's an assembler which understands Masm syntax to some degree, but is premature and restricted to FLAT memory model (32- and 64-bit).
  • GoASM is a freeware assembler, restricted to FLAT memory model (32- and 64-bit) and Windows programming.
  • SolASM (Solar Assembler) is a freeware assembler, supports 16-, 32- and 64-bit, and output formats Binary, Omf, Coff, Elf, Macho. Slightly premature.
  • LZASM (Lazy Assembler) is a free assembler which runs on Win32 and DOS. Supports TASM 'IDEAL' syntax.


  • FreeBasic is a free BASIC compiler (Win32 and DOS).
  • From Sudley Place Software you may get QLINK, an OMF linker and 386SWAT, a 386 debugger. Also take a look at DPMIONE, their free DPMI 1.0 server.
  • The WDOSX site offers another free PE based DOS extender, which you may compare with HX. (Not under development anymore.)
  • DosWin32 is -like WDOSX - a HX competitor. Some of the docs are in russian only.
  • A site where many free compilers, assemblers, debuggers and dos extenders are listed is Free Programmers Resources. A similiar site with a more general approach, but without DOS extenders is Free Programming Resources.  

DOS Sites