I’m looking for a way to visualize how my .c and .h files interact and interface with each other. Is there a program that does that?? Maybe more generally, is there a program that helps design programs graphically?
Essentially, it specifies various types of diagrams you can create to display different aspects of your software design.
I don't know much about specific tools you can use to create UML diagrams. The only one I've ever used is Enterprise Architect, which is intented for professional software developers, and is probably expensive.
A search for "UML tools", or something similar, might help you find something free, or at least cheaper.
understand for c++ if it is still around lists the caller of every function and what every function calls. It draws a bit but I can't recall what all it draws and what is text. I haven't kept up with their newer versions, and its expensive.