DOS/NT started in 1988 as an experiment in writing device drivers in C for 
Microsoft's MS-DOS1.  Both block and character device drivers were written, 
along with special C data structures to match the MS-DOS request packet.  It 
was then recognized that using the same techniques, an operating system 
could be written that would take advantage of the C language features and 
would require much less time to develop than the traditional assembly 
language techniques.  Although UNIX2 had proven this earlier, it was not 
tried with a traditional pc operating system.

At this time, a minimal operating system using the device drivers written 
earlier along with a new 8086 interrupt API was developed.  It was called 
XDOS and proved to be a functional operating system.  This new operating 
system was used to develop booting techniques and a C library SDK was 
developed for it.

XDOS enhancements were started in 1989 and MS-DOS was chosen as the new API.  
A more advanced architecture was also developed.  This included the use of 
an IPL (intermediate program loader) to set up the operating environment 
prior to loading the operating system itself and reentrant system calls 
facilitating real-time applications.  This version, know as NSS-DOS, was 
completed and demonstrated in 1991.  As a result of these demonstrations, 
NSS was approached to supply source license for this operating system by a 
major defense contractor.  The only new requirement - it had to run on 68K 
processors.

This presented a new challenge.  Due to the MS-DOS model used for the API, 
NSS-DOS relied heavily on a segmented architecture.  To meet this challenge, 
a major redesign of NSS-DOS was undertaken.  New proprietary techniques were 
developed that allowed the same source to be compiled on a variety of hosts 
and with a wide range of compilers.  This new version, DOS/NT, was the result o
of this new project.  The kernel was redesigned as a micro kernel along with 
logical separation of the filesystem, memory and task managers.  A new DOS 
API was designed along with a new DOS SDK to guarantee portability.  
Additionally, all processor unique code was separated from the core 
functions.  The result is  the highly portable operating system that DOS/NT 
represents.

After a number of successful commercial applications, DOS/NT is now part of
both dosemu and Free-DOS.  A new version, curently named DOS/C, is the
subject of an upcoming book.  This version is intended for binary
redistribution, free of any royalty.  See the accompanying license.txt file
for details.  If you have not received this file, contact me at the address
below and I will send a copy to you.

MS-DOS is a trademark of Microsoft Corporation.
UNIX is a trademark of USL, Inc.


Pat Villani
Networks Software Systems, Inc.
23 Cornwall Road
Freehold, NJ 07728

November 22, 1994