The DOS 'APPEND' command was designed to allow programs to access files in additional directories beyond the one currently set as the working directory. This command aimed to simplify file accessibility in DOS environments, particularly when managing files across various directories. It highlights how early commands in DOS led to the development of subsequent commands like 'SUBST,' which creates a virtual drive for a specific folder to facilitate easier access, especially in scenarios like Remote Desktop sharing. Moreover, some discussions point out nuances in historical references about mainframes, clarifying that companies like DEC produced minicomputers rather than true mainframes. Overall, user experiences reveal the continuing relevance of these commands in modern computing contexts.