No one likes to scroll through 500 lines of code. Unless you’re totally immersed in your project and can keep everything stored in your noggin, break out functions into modules.
Many C programmers prefer to group related functions into similar files. C programmers typically have an output file, an input file, an initialization file, and so on. Each file, or module, is compiled and linked separately to form the code. The benefits are that the files are smaller and if they compile and work, you no longer need to mess with them.