hmm, it provides an interface of sorts between programs and the hardware though, and provides an environment for other software to act as an interface between the hardware and the apps, also it provides a command line interface to the user, so perhaps DOS and its associated software are an OS together.
I think DR-DOS is a better operating system, and FreeDOS is a lot better, although the latter is not good for running any GUI over in my experience, and the former is closed, and sometimes a bit finnicky for no apparent reason.