fdpp is a 64-bit DOS core.
It is based on a FreeDOS kernel ported to modern C++.
In short, FreeDOS plus-plus.
Can be compiled with clang (not gcc!) and booted under dosemu2.
Just run make.
For an out-of-tree build, run <path_to_fdpp>/configure
before running make.
After compiling, run sudo make install to install.
For the ubuntu package please visit this PPA. Fedora packages are here.
The simplest way to get it running is to use
dosemu2.
Get the pre-built dosemu2 packages from
ubuntu PPA
or from
COPR repo
of build it from sources.
fdpp uses fdppconf.sys file at boot. This file has the standard format of config.sys with some syntax extensions. It is fully backward-compatible with the DOSish config.sys, and if fdppconf.sys is missing, config.sys is attempted instead.
fdpp is a user-space library that, as any DOS, can
run DOS programs. Being a library, it can't act on
its own and needs a host program to operate. This
also means it can't be booted from the bare-metal
PC, as the original freedos could.
The host program needs to provide a couple of
call-backs for running real-mode code in v86 or
similar environment. See
this code
as an example of providing call-backs to fdpp, and
this code
as an example of the boot loader.
Sufficiently DOS-oriented kernels like
freedos-32
or
pdos/386
are the good candidates for running fdpp in the future.
A meta-compiler that was initially able to compile the
freedos kernel from its almost unmodified sources.
As the project evolves, the ability to compile freedos
from the unmodified sources have lost its value and was
dropped, as our copy of freedos is now heavily modified.
As the result, the compiler is very small and is targeted
only to our coding patterns.
The main tasks of it are to parse FAR pointers and generate
thunks to real-mode asm code of freedos. As with any other
compiler, fdpp is supplied with a small runtime support
library and a dynamic linker.
Simply put, fdpp runs every DOS program we tried, so the
compatibility level is supposed to be very high. Better
than that of most other known DOS clones, including FreeDOS.
OTOH fdpp removes some compatibility hacks that FreeDOS had.
For example it doesn't play tricks with disabling A20 when
returning to user code, so you may see "Packed file is corrupt"
message on some old exe files. Using "loadfix" command avoids
that problem.
If you find some compatibility problems, please
report a bug.
fdpp can work in any environment with STL/C++ runtime support. Requirements to the standard libraries are very small, far within the ISO standards. No posix or OS-specific APIs are used. The build requirements are in line with today's posix-compatible environments: you'll need the full stack of tools like bison, autoconf, sed etc. Additionally you'll need a clang tool-chain as clang++ is the only compiler to build fdpp with. That said, building fdpp under itself may be a challenge. :)
FreeDOS kernel is a DOS-compatible kernel that is used as a core of fdpp.
dosemu2 is a virtual machine that allows you to run DOS software under linux. It is a primary host platform for fdpp.
comcom32 is a 32bit command.com that is supposed to be used with fdpp while we don't have a 64bit one.
dosbox has a good built-in DOS written in C++. It is tightly coupled to dosbox; you can't easily port it to your project, whereas fdpp is designed to be plugable. Also it uses host APIs and libraries for filesystem access, CD-ROM playing and similar things. fdpp uses no host APIs or libraries, which may be good or bad, depending on your use-case. dosbox is cleanly written in C++, whereas fdpp wraps the C-coded freedos kernel into a C++ framework, resulting in a nuclear C/C++ mix.
freedos-32 is a kernel written with DOS compatibility in mind. It has a rich user-space part with libc. Very good candidate for running fdpp. Unfortunately, the kernel was scrapped, and currently something else is being developed.
freedos-64 seems to be a project planning to implement a 64bit kernel around the real-mode freedos kernel.
NightKernel
is A 32-bit drop-in replacement for the FreeDOS kernel, as
they call themselves. In fact, it is an assembly-written
ring-0 kernel, currently w/o any DOS compatibility at all.
Can't be used to run fdpp because it doesn't support user-space
add-ons.
pdos/386
is a Public Domain Operating System with a user interface as simple
as MSDOS.
It supports a "theoretical 32-bit MSDOS API" (probably similar to
that of 32-bit DOS extenders) and some of the Win32 API, allowing
a subset of Windows executables to be run. PDOS/386 is good enough to
run gcc, as, and ld to rebuild itself.
As for running fdpp - pdos/386 is a very promising project, but
its author seems to be reluctant at adding v86 support, preferring
to switch to real mode for bios calls. The lack of v86 leaves very
small room for fdpp and for DOS programs in general unfortunately.