I have DOS 6.22, the last retail version, on 3.5 inch diskettes and a DOS 6 "manual" that came with a Packard Bell computer. Knowing some DOS commands was helpful when I was working at a Defense agency where I had some access to a UNIX system which involved working from a command prompt, or whatever it was called in UNIX. For example, the ls command in UNIX listed the files in a directory like the dir command in DOS.