How to organize my c code

Question

I have large main file contains about 7,000 lines of C code. If I want to make this code modular and separate the code from this file. what is the main criteria for separating the functions out of the file and functions that should stay in the file.

Answer 1

• Follow earlier suggestions.
• Eliminate any duplicate or almost duplicate code by creating functions.
• Organize by functionality and dependency. Modules should have as little inter-dependency as possible.
• Follow SOLID Principles and other design patterns and practices (all of which can be implemented in some degree in C).

I like to use a top-down decomposition of the code. For example:

main()
{
    Initialize();
    Introduce();
    while (some_condition)
    {
        DoSomething();
        DoSomethingElse();
    }
    SayGoodbye();
    Shutdown();
}

The main() should be short and to the point and give you a quick overview of what the program does from a high-level. Each of these functions can be broken down in a similar way. This should continue until the lowest level functions have a single, focused purpose (logical modularity). These functions can be put into additional .c/.h files to have physical modularity.

Good luck!

Answer 2

Break up by functionality/responsibility.

For example, place all string handling in one module/file, place file handling in another.

Answer 3

It is a simple measure: the fewer declarations you have in the .h file, the more modular it is. Grouping by functionality is important. Having extern declarations is very bad, give those an extra 'penalty'.