DOS3.3 questions

[be404@yfn.ysu.edu (Adalbert Goertz)]

I have always worked with Prodos and begin to set up games for our youngsters
which are either DOS or something else(Pascal?).
Anyway I am puzzled about the DOS games:
Some are selfbooting, others are not.
I have not figured out why some are selfbooting and why others are not and
give a message
THIS DISK HAS NO DOS TO BOOT.
INSERT ANOTHER DISK AND PRESS A KEY TO REBOOT.
I know that in Prodos booting, the computer looks for the PRODOS file.
What file is required to make DOS booting possible?
Do I ALWAYS have to run the Master disk first? I dont think so.
Thanks.
-- 
*************** Adalbert Goertz ****** ph 717-762-7378 ********
retired in Waynesboro PA (65 miles from Baltimore/Washington DC
  Mennonite genealogy of East and West Prussia prior to 1945.
Would anyone trade my PA home for house in CO,NM,AZ or ? ? ? ?