Projects for beginners

[Richard Kenner]

    It also effectively sets those dependencies in concrete. If, for any
    reason, the dependencies change for a particular header, you have to
    change all sources that include it.

>From a conceptual point of view, you do anyway.  A header is a specification
of something which is implemented in a .c file.  If the specification
of something changes, you have to look at all callers to make sure they
reflect the change of specification.