iS-DOS assembler

Press RESET immediately, All! How can the subject have something like a *.h file in the project for inclusion? it during assembly? That is, for example, I have a file in which a lot of labels are defined and I want to use it during assembly other files. At the same time, you don’t want to define included labels as global - much less of them will be used than there are. Actually the whole question how to do 'include' or something similar. I read the documents. Include not found. :-(