Without the help and support of my good and long time friend Brian, the Author of 8bit Micro Systems, my www.PCXT-Micro.com site would probably still be in the primeval development stage.
Brian K. Hahn
There is a good source of information in the Tandy MS-DOS 3rd Edition (Vol. 2 Advanced Applications, Cat. No. 25-1507) by David A. Lien, some of which we have included on our site. This book has a considerable amount of detailed information for the person interested in doing programming in pre-Windows DOS.
These articles were written by Tim Paterson, the author of the original DOS. So it is the best historical source of the events and can be found at: Paterson Tech
History of DOS