Re: [ros-dev] (Free)DOS subsystem

[Peter Dolding]

Myria wrote:
>   I've wanted to write an NTVDM for ReactOS, but
> I'm not sure when I'd ever
>  have time.
>  Windows NT's DOS subsystem, NTVDM, is a user-mode program that runs on top
>  of Win32.  It runs DOS programs as Windows processes, using v86 mode to run
>  the programs.  DPMI programs are supported by asking the kernel to allocate
>  LDT segments and running directly.  (If you write a DOS32 program and know
>  the correct addresses, you can call MessageBoxW in user32.dll and it will
>  work.)
>  This differs significantly from DOSBox, which is effectively a machine
>  emulator rather than an API translator.  DOSEmu, in comparison, is
>  essentially the same design as NTVDM but for Linux.
>  FreeDOS in DOSBox works very well, because the FreeDOS kernel is its normal
>  self and is unaware that it's inside a VM.  However, this doesn't work for
>  NTVDM/DOSEmu.  In these, the FreeDOS kernel will need to be heavily
>  modified, particularly because the NT kernel handles file I/O.  Programs
>  inside the virtual DOS environment use illegal opcodes to talk to NTVDM.
>  Melissa
>     
True  Closest Freedos to Windows NT NTVDM is
http://freedos-32.sourceforge.net/.   Its was newer version under
development.  It could be stalled from 2005.
Peter Dolding