I'm not entirely sure of what I am asking but I was discussing with a co-worker on what knowledge of programming they would consider to be acceptable for a full-time job/professional level. We were discussing mainly for C, but I understand that experience in multiple languages,and excelling in one would be sublime.
They said knowledge of pointers and knowing how to apply them, as well as data management would suffice for a graduate level position. This surprised me as I know these concepts and how to apply them, but I do not think I am necessarily capable of succeeding at a graduate/beginning role if I wanted a career change
I think it's a blur really, because different employers want different skills. I would agree though that you need to be at least fully capable of understanding every aspect of the language (not knowing by heart, just being capable of picking it up fast), know the syntax, know the build tools, lastly, ability to use design patterns common to C to some degree.
I think having at least Java, HTML/CSS and PHP should be enough to start a job search with. Of course, every employer will require a different skillset. But, starting with those three languages, moving on to other languages is a cinch, in my opinion of course.