Fluent C

Chapter 8. Organizing Files in Modular Programs

Any programmer who implements a larger piece of software and wants to make that software maintainable confronts the question of how to make the software modular. The most important part of that question that is related to dependencies between software-modules is answered, for example, by the SOLID design principles described in the book Clean Code: A Handbook of Agile Software Craftsmanship by Robert C. Martin (Prentice Hall, 2008) or by the design patterns described in the book Design Patterns: Elements of Reusable Object-Oriented Software by the Gang of Four (Prentice Hall, 1997).

However, making software modular also raises the question of how to organize the source files in a way that allows someone to make the software modular. That question has not yet been answered very well, which results in bad file structures in codebases. It is difficult to make such codebases modular later on, because you don’t know which files you should separate into different software-modules or into different codebases. Also, as a programmer, it is difficult to find the files containing APIs that you are supposed to use, and thus you might bring in dependencies to APIs that you are not supposed to use. This is an issue for C in particular because C does not support any mechanism to mark APIs for internal use only and restrict access to them.

There are such mechanisms in other programming languages, and there is advice on how to structure files. ...